Propeller for vessel, propeller boss, and manufacturing method for the same

Abstract

To provide a propeller boss for a propeller for vessel having both strength to produce propulsion of a vessel and corrosion resistance enduring sea water.SOLUTION: A propeller boss of a propeller for vessel includes a base material composed of ferrous alloy and a surface layer material composed of metal material having corrosion resistance for sea water and covering a surface of the base material. The propeller for vessel includes the propeller boss and a plurality of blades planted on the propeller boss.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a propeller boss for a marine propeller. [Background technology]

[0002] Conventionally, marine propellers include a propeller boss fixed to a propeller shaft to which thrust from a drive source is transmitted, and a plurality of blades provided on the outer circumferential surface of the propeller boss. Patent Document 1 discloses this type of marine propeller.

[0003] The marine propeller of Patent Document 1 includes a propeller boss fixed to a propeller shaft, multiple blades provided on the outer peripheral surface of the propeller boss, and a cap attached to the rear end of the propeller boss. The propeller boss, multiple blades, and cap are configured to be rotatable together by thrust from a drive source. The propeller boss and blades are formed as a single component by casting a corrosion-resistant metal material such as a copper alloy. Alternatively, the propeller boss is made of a copper alloy, and the blades fixed to the propeller boss are made of carbon fiber reinforced plastic. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-6169 Summary of the Invention [Problem to be solved by the invention]

[0005] Marine propellers must be strong enough to generate thrust for the ship and corrosion-resistant enough to withstand seawater. As a result, the material options for marine propellers are limited, making it difficult to meet the current demand for higher power density.

[0006] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a propeller boss for a marine propeller that combines the strength required to generate thrust for a ship with the corrosion resistance required to withstand seawater. [Means for solving the problem]

[0007] In order to solve the above problems, a propeller boss for a marine propeller according to one embodiment of the present disclosure includes a base material made of an iron-based alloy and a surface layer material that covers the surface of the base material and is made of a metal material that is corrosion-resistant to seawater.

[0008] A marine propeller according to one aspect of the present disclosure includes the propeller boss and a plurality of blades attached to the propeller boss.

[0009] A method for manufacturing a propeller boss of a marine propeller according to one embodiment of the present disclosure includes forming a base material made of an iron-based alloy into the shape of the propeller boss by casting, and coating the surface of the base material with a metal material that is corrosion-resistant to seawater. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a propeller boss for a marine propeller that combines the strength required to generate thrust for a ship with the corrosion resistance required to withstand seawater. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a marine propeller according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram illustrating the gear shifting mechanism of a marine propeller. [Figure 3] FIG. 3 is a cross-sectional view of a wall forming a propeller boss of a marine propeller. [Figure 4] FIG. 4 is a cross-sectional view of a modified example of a wall forming a propeller boss of a marine propeller. DETAILED DESCRIPTION OF THE INVENTION

[0012] A marine propeller according to this embodiment will be described below with reference to the accompanying drawings. The marine propeller according to this embodiment is suitably applied to a screw propeller whose blade angle can be freely changed, i.e., a controllable pitch propeller (CPP). However, the application of the marine propeller 1 according to this disclosure is not limited to CPPs, but can also be applied to fixed pitch propellers (FPPs).

[0013] <<Outline of Marine Propeller 1>> First, a schematic configuration of a marine propeller 1 according to one embodiment of the present disclosure will be described. The marine propeller 1 shown in Fig. 1 includes a propeller boss 2 fixed to a propeller shaft 10 to which thrust from a drive source is transmitted, and a plurality of blades 3 provided on the outer peripheral surface of the propeller boss 2. In the example shown in Fig. 1, the marine propeller 1 includes four blades 3, but the number of blades 3 is not limited to this example.

[0014] The propeller boss 2 has a cylindrical shape with one end closed that extends in the axial direction of the propeller shaft 10. The open end of the propeller boss 2 is fixed to a flange 12 of the propeller shaft 10 by a plurality of bolts. The propeller boss 2 may be fixed to the flange 12 by press fitting.

[0015] A plurality of blade holes 21 are provided in the body of the propeller boss 2, penetrating the propeller boss 2 in the radial direction. The propeller boss 2 of the marine propeller 1 according to this embodiment is provided with the blade holes 21 at four locations dispersed in the circumferential direction in accordance with the number of blades 3. A blade 3 is implanted in each of the blade holes 21.

[0016] The propeller boss 2 contains components of a gear change mechanism 31 that changes the angle of the blades 3. FIG. 2 is a diagram illustrating the gear change mechanism 31 of the marine propeller 1. As shown in FIG. 2, the gear change shaft 32, crosshead 33, and crankpin ring 34 of the gear change mechanism 31 of the marine propeller 1 are disposed within the propeller boss 2. The gear change shaft 32 is a shaft extending parallel to the propeller shaft 10 and passes through the inside of the propeller shaft 10. The reciprocating motion of the crosshead 33 is transmitted to the gear change shaft 32 and crankpin ring 34. The bases of the blades 3 are fixed to the crankpin ring 34. The bases of the blades 3 or the crankpin ring 34 pass through the blade holes 21. The crankpin ring 34 converts the reciprocating motion of the crosshead 33 into rotational motion around the center of rotation of the blades 3 via a crankpin and a slide.

[0017] The propeller boss 2 houses a hydraulic cylinder that reciprocates the pivot shaft 32. The interior of the propeller boss 2 is divided into a first cylinder chamber 38 and a second cylinder chamber 39 by a hydraulic piston 37 connected to the crosshead 33 and the pivot shaft 32. High-pressure oil is supplied to the first cylinder chamber 38 or the second cylinder chamber 39 by an oil supply device, causing the hydraulic piston 37 to slide within the propeller boss 2. The movement of the hydraulic piston 37 moves the pivot shaft 32 and the crosshead 33. The movement of the crosshead 33 causes the blades 3 to rotate simultaneously via the crankpin ring 34, changing the pitch angle. However, the configuration of the pivot mechanism 31 for the blades 3 of the marine propeller 1 is not limited to this embodiment, and a pivot mechanism 31 with a known configuration can be used.

[0018] <<Material composition of Propeller Boss 2>> Here, we will explain the material configuration of the propeller boss 2 of the marine propeller 1. Fig. 3 is a cross-sectional view of the wall that forms the propeller boss 2 of the marine propeller 1. As shown in Fig. 3, the propeller boss 2 is made up of a base material 24 and a surface layer material 25 that covers the surface of the base material 24. In other words, the surface of the propeller boss 2 that comes into contact with seawater is covered with the surface layer material 25.

[0019] The substrate 24 is made of a material with higher strength than copper alloys such as aluminum bronze, which are used as materials for conventional propellers. Corrosion resistance is not required for the substrate 24. Examples of materials for the substrate 24 include iron-based alloys such as cast carbon steel, cast steel for welded structures, high-tensile carbon steel for structures, cast low-alloy steel, cast stainless steel, cast high-manganese steel, cast steel for high-temperature and high-pressure applications, cast steel for low-temperature and high-pressure applications, cast carbon steel for general industrial machinery, malleable cast iron, austenitic cast iron, gray cast iron, spheroidal graphite cast iron, CV graphite cast iron, thick-walled ferritic spheroidal graphite cast iron for low-temperature applications, and austempered spheroidal graphite cast iron. These iron-based alloys are less expensive than the copper alloys used as materials for conventional propellers, contributing to reduced manufacturing costs. The substrate 24 is a casting formed by casting, as described below. However, the substrate 24 is not limited to a single layer and may be composed of multiple layers. For example, as shown in FIG. 4, the substrate 24 may be composed of a molded body 241 made of an iron-based alloy and an intermediate coating layer 242 that coats the molded body 241, and the surface of the substrate 24 (i.e., the surface of the intermediate coating layer 242) may be covered with a surface layer material 25. The intermediate coating layer 242 may be made of multiple layers. Examples of materials for the intermediate coating layer 242 include functional materials such as strength materials, and copper alloys of a different type from the surface layer material 25. By having the intermediate coating layer 242 on the substrate 24 in this way, a function different from that of the surface layer material 25 can be imparted to the propeller boss 2.

[0020] The surface layer material 25 is made of a material that has corrosion resistance to seawater equal to or greater than that of the copper alloys used as materials for conventional propellers. Examples of materials for such surface layer material 25 include copper, copper alloys, and stainless steels such as austenitic stainless steel, ferritic stainless steel, duplex stainless steel, martensitic stainless steel, and precipitation hardened stainless steel. The surface layer material 25 may be made of a noble metal that is resistant to rust (i.e., has a low tendency to ionize).

[0021] The propeller boss 2 having the above material configuration has higher strength than the propeller bosses of conventional propellers due to the base material 24, and is corrosion-resistant to seawater due to the surface layer material 25 that covers the surface of the base material 24. In this way, the present disclosure can provide a propeller boss 2 for a marine propeller 1 that has both the strength to generate thrust for the ship and the corrosion resistance to withstand seawater.

[0022] <<Propeller Boss 2 Manufacturing Method>> A method for manufacturing the propeller boss 2 of the marine propeller 1 configured as described above will now be described. First, the base material 24 of the propeller boss 2 is molded from the material of the base material 24. In this embodiment, the base material 24 is molded by casting. More specifically, the material of the base material 24 of the propeller boss 2 is melted to form a molten metal, which is poured into a cavity of a mold corresponding to the propeller boss 2 and cooled to solidify. After the base material 24 is released from the mold, its surface shape is adjusted by machining or the like, and then it is sent to the next process. The surface shape may be adjusted after the subsequent coating process.

[0023] Next, the surface of the substrate 24 is coated with the material of the surface layer 25. Directed energy deposition (DED), a type of additive manufacturing method for metal materials, can be used as a coating method. Directed energy deposition (DED) is a method of depositing a metal material on a target surface by irradiating the target surface with a laser or electron beam and spraying a powdered or filamentary metal material onto the target surface, melting and solidifying the metal material. Among directed energy deposition methods, laser metal deposition (LMD), in which a laser is irradiated onto the target surface and metal powder is sprayed onto the irradiated area, is preferred. Specifically, powder of the material of the surface layer 25 is generated, and the surface of the substrate 24 is irradiated with a laser and sprayed with the powder, melting the powder and solidifying it on the surface of the substrate 24. The surface layer 25 is coated on the outer wall surface of the substrate 24, but not on the inner wall surface of the substrate 24. The blades 3 and the variable-speed mechanism 31 are assembled to the propeller boss 2 manufactured through the above process to form the marine propeller 1.

[0024] [Summary] The propeller boss 2 of the marine propeller 1 according to the first aspect of the present disclosure includes a base material 24 made of an iron-based alloy, The substrate 24 is characterized by including a surface layer 25 made of a metal material having corrosion resistance against seawater and covering the surface of the substrate 24.

[0025] The propeller boss 2 of the marine propeller 1 according to the second item of the present disclosure is the propeller boss 2 according to the first item, which has a formed body 241 made of an iron-based alloy and an intermediate coating layer 242 made of a material different from the surface layer material 25 and coating the surface of the formed body 241.

[0026] A marine propeller 1 according to a third aspect of the present disclosure includes the propeller boss 2 according to the first or second aspect, and a plurality of blades 3 attached to the propeller boss 2.

[0027] A method for manufacturing a propeller boss 2 of a marine propeller 1 according to a fourth aspect of the present disclosure includes: forming a base material 24 made of an iron-based alloy having the shape of a propeller boss 2 by casting; and This involves coating the surface of the substrate 24 with a metal material that is resistant to corrosion by seawater.

[0028] The propeller boss 2 of the marine propeller 1 according to the first to third items of the present disclosure, and the propeller boss 2 of the marine propeller 1 manufactured by the method according to the third item, include a base material 24 made of an iron-based alloy, which has a higher specific strength than the copper alloy propeller bosses of conventional propellers. The base material 24 allows the propeller boss 2 according to the present disclosure to have higher strength than the copper alloy propeller bosses of conventional propellers. By increasing the strength of the propeller boss 2, the marine propeller 1 equipped with the propeller boss 2 can achieve a higher power density than conventional propellers equipped with a copper alloy propeller boss. Furthermore, the propeller boss 2 according to the present disclosure can be made smaller and slimmer, while still maintaining the same strength as a copper alloy propeller boss, and is expected to improve propulsion performance by reducing propulsion resistance.

[0029] Furthermore, when the marine propeller 1 is a controllable pitch propeller as in the above embodiment and the hydraulic cylinder of the variable speed mechanism 31 is built into the propeller boss 2, high hydraulic pressure is applied from the inside to the outside to the wall of the propeller boss 2. In the propeller boss 2 according to the present disclosure, the inner wall of the propeller boss 2 is made of an iron-based alloy with a high specific strength, and therefore can withstand higher pressures than conventional propeller bosses made of copper alloys, making it particularly suitable as a propeller boss with a built-in hydraulic cylinder. [Explanation of symbols]

[0030] 1: Marine propeller 2: Propeller boss 3: Blade 24: Base material 241: Molded body 242: Intermediate coating layer 25: Surface material

Claims

1. a substrate made of an iron-based alloy; A surface layer material made of a metal material having corrosion resistance to seawater and covering the surface of the base material. Propeller boss of a marine propeller.

2. The substrate has a molded body made of an iron-based alloy and an intermediate coating layer made of a material different from the surface layer material and coating the surface of the molded body.

2. A propeller boss for a marine propeller according to claim 1.

3. A propeller boss according to claim 1 or 2; and a plurality of blades attached to the propeller boss. Marine propeller.

4. forming a base material made of an iron-based alloy in the shape of a propeller boss by casting; and Coating the surface of the substrate with a metal material that is corrosion-resistant to seawater, A manufacturing method for propeller bosses for marine propellers.

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