JP2008074389A - Propeller for watercraft and outboard motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a propeller for watercraft having superior abrasion resistance. <P>SOLUTION: The propeller for watercraft comprises a propeller body 27b having a blade portion and a hub portion, the propeller body 27b is molded by casting an aluminum alloy, and an anodized coating 27c provided so as to cover a surface of the propeller body, the anodized coating 27c obtained by performing a blast treatment to the surface of the propeller body and, thereafter, anodizing the surface of the propeller body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a marine propeller and an outboard motor.

  Outboard motors are widely used for small vessels such as pleasure boats and small fishing boats because they are attached to the hull just by hooking them to the stern of the vessel and do not occupy space in the vessel. Various outboard motors are used today depending on the size and application of the hull.

  Generally, an outboard motor having a propeller made of stainless steel and an engine with a high output (for example, 100 horsepower or more) is used for a relatively large ship. On the other hand, an outboard motor equipped with a propeller made of aluminum or the like and an engine with a relatively small output is used for a relatively small ship. A propeller made of aluminum is light in weight and can be manufactured at a low cost, and is therefore suitable as a propeller for an outboard motor equipped with an engine with a small output.

  When the marine propeller is formed of aluminum, it is necessary to prevent corrosion of the aluminum alloy by seawater. For this reason, generally, a propeller in which the surface of a propeller body made of an aluminum alloy is coated for corrosion prevention is widely used.

In Patent Document 1, in order to solve the problem that the edge of the propeller becomes dull due to the coating film provided on the surface of the propeller and the water breakage when the propeller rotates, the propeller made of an aluminum alloy is subjected to hard anodizing treatment, and the edge of the propeller It has been disclosed to ensure the sharpness.
Utility Model Registration No. 3029215 Specification

  Small boats equipped with outboard motors are often used in the sea or rivers for fishing, business, leisure, etc., and may be moored by pulling them up to sandy beaches or moored in shallow sand on the riverbank. is there. For this reason, when mooring a ship or sailing from a mooring place to a river or the sea, the surface of the propeller is easily worn by rolling up the sand and rotating the propeller in the water containing the sand. As a result, the surface of the propeller is peeled off due to wear, and the propeller body is corroded or the propeller body is polished. Since the coating film does not have sufficient hardness, the conventional outboard motor propeller has a problem of short life due to wear.

  Patent Document 1 merely discloses forming an alumite layer known as an anticorrosive film for aluminum instead of a coating film for anticorrosion, and does not disclose any of the above-described problems. Moreover, in order to prevent the edge of a propeller from becoming dull, a hard alumite layer cannot be formed thickly. For this reason, the thickness of the hard alumite layer of the propeller of Patent Document 1 is at most about 15 μm, and it is considered that sufficient wear resistance cannot be obtained.

  In addition, an aluminum alloy propeller is generally formed by die casting or gravity casting. However, even if the formed propeller is subjected to anodization as it is, the coating thickness varies. As a result, sufficient wear resistance could not be obtained. Further, if the film is formed thick for the purpose of obtaining sufficient wear resistance, it is necessary to perform anodization for a long time, and the hardness of the film is lowered. As a result, wear resistance is reduced.

  Such a problem has occurred not only in ships equipped with outboard motors, but also in small ships where engines are installed onboard.

  An object of the present invention is to solve such problems of the prior art and to provide a marine propeller and an outboard motor having excellent wear resistance.

  A marine propeller according to the present invention is a propeller body having a blade portion and a hub portion, which is a propeller body formed by casting an aluminum alloy, and an anodized film provided so as to cover the surface of the propeller body. And an anodic oxide film obtained by anodizing the surface of the propeller body after the blast treatment.

  In a preferred embodiment, the aluminum alloy contains silicon, and a length of a eutectic region containing eutectic silicon particles is 18 μm or less at an interface between the propeller body and the anodized film.

In a preferred embodiment, the surface roughness Rz of the anodized film is 25 μm or more and 40
It is below μm.

  In a preferred embodiment, the anodic oxide film has a thickness of 20 μm or more and 100 μm or less.

  In a preferred embodiment, the anodic oxide film has a hardness of 350 Hv or more and 450 Hv or less.

  In a preferred embodiment, the propeller body is formed by die casting using the aluminum alloy.

  In a preferred embodiment, the particle size of the eutectic silicon particles in the eutectic region at the interface is 0.8 μm or less.

  In a preferred embodiment, the aluminum alloy is an Al—Mg alloy containing 0.3 wt% or more and 2.0 wt% or less of silicon.

  The outboard motor of the present invention includes a marine propeller defined in any of the above.

  The ship of this invention is provided with the said propeller for ships.

  The marine propeller of the present invention includes a propeller body obtained by die casting of an aluminum alloy containing silicon in a proportion of 0.3 wt% to 2.0 wt%, and an anodized film provided on the surface of the propeller body. The anodized film has a thickness of 20 μm or more and 100 μm or less, and the difference between the maximum thickness and the minimum thickness of the anodized film is 25 μm or less.

  In a preferred embodiment, the anodic oxide film has a hardness of 350 Hv or more and 450 Hv or less.

  The marine propeller manufacturing method of the present invention includes a step (A) of forming a propeller body having a blade portion and a hub portion by casting an aluminum alloy, a step (B) of performing a blast treatment on the surface of the propeller body, And (C) forming an anodized film so as to cover the surface of the propeller body by anodizing the propeller body subjected to the blast treatment.

  In a preferred embodiment, the aluminum alloy contains silicon, and the eutectic region containing silicon has a length of 18 μm or less at the interface with the anodized film of the propeller body. Perform sweep processing.

  In a preferred embodiment, the blast treatment in the step (B) is performed so that the surface roughness Rz of the anodized film is 25 μm or more and 40 μm or less.

  In a preferred embodiment, in the step (C), the anodizing time is adjusted so that the anodized film having a thickness of 20 μm or more and 100 μm or less is formed.

  In a preferred embodiment, in step (C), the concentration and temperature of the anodizing electrolytic bath are adjusted so that the anodized film having a hardness of 350 Hv to 450 Hv is formed.

  In a preferred embodiment, in the step (A), the propeller body is formed by a die casting method.

  In a preferred embodiment, the molding in the step (A) is performed so that the particle size of the eutectic silicon particles in the eutectic region at the interface is 0.8 μm or less.

  In a preferred embodiment, the aluminum alloy is an Al—Mg alloy containing 0.3 wt% or more and 2.0 wt% or less of silicon.

  According to the present invention, the surface of the propeller body is covered with the hard anodic oxide film, and the wear resistance is excellent. The anodic oxide film is obtained by anodizing the surface of the propeller body formed by casting after the blast treatment. For this reason, nonuniformity of the composition in the vicinity of the surface of the propeller body, such as a eutectic structure precipitated by casting, is improved by the blast treatment, and an anodic oxide film having a uniform film thickness is obtained. Accordingly, problems such as partial wear and corrosion are unlikely to occur, and the product life as a propeller is long. For this reason, the propeller for ships excellent in durability and economy is realized.

  Hereinafter, embodiments of a marine propeller and an outboard motor according to the present invention will be described.

  FIG. 1A is a side view of a ship 50 provided with an outboard motor according to the present invention. The ship 50 includes a hull 51 and an outboard motor 52. The outboard motor 52 includes the clamp 16, the propeller 27, and the steering handle 22, and is attached to the stern 12 of the hull 51 by the clamp 16. The operator can change the traveling direction of the ship 50 by the steering handle 22.

  FIG. 2 is a side view of the outboard motor 52. The outboard motor 52 includes an engine 48, and the rotational driving force of the engine 48 is transmitted to the drive shaft 21 to which the drive gear 23 is attached. The outboard motor 52 includes a switching mechanism 41 and a clutch device 25 in order to move the ship 50 forward or backward by changing the rotation direction of the propeller 27. The clutch device 25 includes a forward gear 31 and a reverse gear 33. By operating a shift lever 49 connected to the switching mechanism 41, one of the forward gear 31 and the reverse gear 33 is selectively meshed with the drive gear 23. Thereby, the propeller 27 fixed to the output shaft 29 rotates in the forward direction or the reverse direction. The engine 48 and these drive mechanisms are housed inside the casing 14 and the cowling 10.

  The marine propeller of the present invention is preferably used for an outboard motor, but is also suitable for a marine vessel in which an engine is mounted in a hull (also referred to as an inboard). FIG.1 (b) is a side view of the ship 150 provided with the propeller 27 for ships of this invention. An engine 152 is installed in the hull 151 of the ship 150, and the driving force of the engine 152 is transmitted via a shaft to the propeller 27 that is supported so as to be rotatable at the rear part of the ship bottom.

  FIG. 3 is a plan view showing the propeller 27. The propeller 27 includes a blade portion 61 and a hub portion 62 to which the blade portion 61 is connected. In this embodiment, the hub portion 62 includes an outer hub 70, an inner hub 71, and a rib 72 that connects the outer hub 70 and the inner hub 71. In the present embodiment, the outboard motor 52 employs a structure in which the exhaust gas of the engine 48 is ejected from the gap 72h between the inner hub 71 and the outer hub 70 to the rear of the propeller 27. In this way, the hub is doubled. However, when the outboard motor 52 emits exhaust gas from other places, the hub portion 62 may adopt a single structure. There is no restriction | limiting in particular in the number and shape of the blade | wing part 61, The propeller 27 may be provided with shapes other than the shape shown in FIG.

  An inner hub 71 of the hub portion 62 defines a cylindrical inner space, and a bush 73 is press-fitted into the inner space. The bush 73 is made of an elastic body such as rubber, and the bush 73 is fixed in the inner hub 71 by friction between the bush 73 and the inner hub 71. A hole 73c is provided at the center of the bush 73, and the output shaft 29 is inserted into the hole 73c.

  Since the bush 73 and the inner hub 71 are fixed by friction, when the propeller 27 collides with a driftwood or the like during rotation, the bush 73 slips in the inner hub 71, so that the output shaft 29 rotates while the propeller 29 rotates. 27 can be stopped. This prevents various gears from being damaged and the engine 48 from being damaged.

  In the present invention, the surface of the propeller 27 is covered with an anodized film. The inventor of the present application examined the formation of an anodized film on the surface of the propeller in order to enhance the wear resistance of the propeller made of an aluminum alloy for ships. This is because an anodized film of aluminum is generally high in hardness, and is considered suitable for enhancing wear resistance. However, as a result of detailed studies, it has been found that it is difficult to obtain an anodized film having a uniform thickness because the aluminum alloy constituting the propeller contains an additive element other than aluminum.

  FIG. 4 schematically shows a cross-sectional structure of a propeller 90 in which an anodized film is formed on the surface of a propeller body formed by a die casting method. As shown in FIG. 4, an anodized film 91 is formed on the surface of a propeller body 92 made of an aluminum alloy.

The propeller body 92 is integrally formed by casting in order to reduce the manufacturing cost and increase the bonding strength between the blade portion and the hub portion. Further, during casting, silicon is generally added to the aluminum alloy so that the molten metal reaches every corner of the mold, thereby improving the fluidity of the molten aluminum alloy. However, when the molten metal is cooled, primary aluminum crystallizes out, and after the alloy phase 96 is formed, a eutectic structure including eutectic silicon particles 94 is deposited. This agglomerated portion of the eutectic structure is referred to as a eutectic region 93. The eutectic region 93 is less likely to be anodized than the alloy phase 96 and the distribution in the vicinity of the surface is not uniform. Therefore, the difference between the thickness t ₁ of the anodic oxide film in the portion where the eutectic region 93 is large and the thickness t _{2 in the} portion where the eutectic region 93 is small is large, and the thickness variation in the entire anodic oxide film 91 is large. It turns out that becomes large.

  A natural oxide film may be formed on the surface of the propeller body 92 formed by casting. Since the natural oxide film inhibits the formation of the anodized film, it causes variation in the thickness of the anodized film.

  In order to reduce the variation in thickness, the inventor of the present application performs a polishing process on the surface of the propeller body 92 before anodizing, and precipitates in the vicinity of the surface of the propeller body 92. It has been found that the size of the eutectic region 93 may be reduced by crushing 93 to make the distribution of the eutectic region 93 uniform. Here, the polishing process refers to a process such as shot blasting, in which a shot material is projected onto an object to mechanically grind the surface of the object or to give kinetic energy of the shot material to the surface of the object.

  When the surface of the propeller body is subjected to a polishing process, the surface roughness of the propeller body increases. Since the surface of the formed anodized film reflects the surface roughness of the propeller body before anodizing, the surface of the propeller on which the anodized film is formed also becomes rough. Conventionally, as disclosed in JP-A-60-33192, the propeller propulsive force is greatly influenced by the surface roughness of the propeller, and it is considered that the propulsive force is greatly reduced when the propeller surface becomes rough. It was.

  For this reason, for example, as disclosed in Japanese Patent Application Laid-Open No. 09-001319, the surface of an aluminum alloy is etched or shot blasted in order to form a decorative anodic oxide film with excellent aesthetics. Even if it was known, it was thought that applying a blast treatment to the propeller body to form an anodized film resulted in a decrease in propulsive force and was inappropriate. However, according to the study by the present inventor, it has been found that if the surface roughness is equal to or less than a predetermined value, the propulsive force is hardly reduced even if the surface of the propeller is roughened by the blast treatment. Hereinafter, the structure of the propeller 27 will be described in more detail.

  FIG. 5 shows a cross section near one surface of the blade portion 61 of the propeller 27. Propeller 27 includes a propeller body 27b and an anodized film 27c provided on the surface of propeller body 27b in blade 61 and hub 62. Although not shown, in the blade portion 61 and the hub portion 62, an anodic oxide film 27c is also provided on the other surface of the propeller body 27b.

  The propeller body 27b is integrally formed by casting using an aluminum alloy as described above. For this reason, the propeller body is composed of an aluminum alloy having a composition suitable for casting. When the aluminum alloy is melted, the aluminum alloy preferably contains silicon, and more preferably contains 0.3 wt% or more and 2.0 wt% or less silicon so that the molten metal has sufficient fluidity. . When the silicon content is less than 0.3 wt%, the castability deteriorates because the fluidity of the molten metal is not sufficient. Further, when the silicon content is more than 2.0 wt%, eutectic silicon particles become large as will be described below, and it becomes difficult to obtain a uniform anodic oxide film even if a predetermined blast treatment is performed. .

  The formation of the propeller body 27b is preferably performed by a die casting method. By injecting the molten metal into the mold by using the die casting method, the molten metal is rapidly cooled, and the eutectic region can be reduced. Further, the particle diameter of the eutectic silicon particles can be reduced.

  More preferably, the aluminum alloy further contains at least one of iron and manganese of 0.5 wt% or more and 1.8 wt% or less. By including at least one of iron and manganese in the above-described proportion, the releasability from the mold is improved during die casting, and seizure to the mold can be prevented. Moreover, by including magnesium in a proportion of 2.5 wt% or more and 5.5 wt% or less, mechanical properties such as strength, elongation, and impact resistance can be improved, and corrosion resistance can be improved.

As an aluminum alloy, for example, Al-4Mg-0.8Fe-0.4Mn, Al-5
An Al-Mg alloy having a composition such as Mg-1.3Si-0.8Fe-0.8Mn or Al-6.5Mg-1.1Fe-0.7Mn can be used.

  The anodic oxide film 27c is obtained by anodic oxidation of the surface of the propeller body 27b and then anodic oxidation. As shown in FIG. 5, the roughness Rz of the surface 27t of the anodized film 27c is preferably 40 μm or less. Since the anodized film 27c is obtained by anodizing the surface of the propeller body 27b, the surface 27t corresponds to the surface of the propeller body 27b before the anodization. For this reason, the roughness of the surface 27t approximately matches the roughness of the surface after the propeller body 27b has been subjected to the polishing process.

  In general, the anodized film 27c of aluminum alloy has a high hardness. For this reason, the propeller 27 on which the anodized film 27c is formed has high wear resistance. More preferably, the anodized film has a hardness of 350 Hv or more and 450 Hv or less. If the hardness of the anodized film is lower than 350 Hv, sufficient wear resistance characteristics cannot be obtained. On the other hand, the higher the hardness of the anodized film, the better. However, when an anodic oxide film having a hardness greater than 450 Hv is to be obtained, a special treatment solution must be used, which increases the manufacturing cost of the anodic oxide film.

  The anodized film 27c preferably has a thickness of 20 μm or more and 100 μm or less. Here, the thickness means a thickness determined by a microscope cross-section measurement method defined in JIS H8680. When the minimum film thickness of the anodized film is smaller than 20 μm, sufficient wear resistance characteristics cannot be obtained. On the other hand, the thicker the anodic oxide film, the better the wear resistance. However, when the maximum film thickness of the anodic oxide film 27c exceeds 100 μm, it takes time to form the anodic oxide film, and the productivity is lowered.

  The hardness of the anodic oxide film 27c can be adjusted by changing the concentration and temperature of the electrolytic bath used for anodic oxidation. The thickness of the anodized film 27c can be adjusted by the anodizing time. As an anodizing treatment method for forming the anodized film 27c, a treatment method for forming a hard film is preferably used, and an electrolytic solution such as sulfuric acid or oxalic acid can be used.

  FIG. 6 schematically shows the crystal structure at the interface 27s between the propeller body 27b and the anodized film 27c. As shown in FIG. 6, a eutectic region 66 containing eutectic silicon particles 65 in the alloy phase 67 is precipitated at the interface 27 s of the propeller body 27 b. The length of the eutectic region 66 is preferably 18 μm or less. Here, the length of the eutectic region 66 refers to the maximum of the lengths of the eutectic region whose interface is measured by the microscopic cross section measurement method. If the length of the eutectic region 66 is larger than 18 μm, the film thickness of the anodized film becomes non-uniform even when the polishing process is performed. As a result, the wear resistance characteristics cannot be sufficiently obtained in the portion where the film thickness is small, and the propeller body is exposed and corrosion or the like is likely to occur.

  The particle diameter of the eutectic silicon particles 65 in the eutectic region 66 is preferably 0.8 μm or less. If the particle size of the eutectic silicon particles 65 is larger than 0.8 μm, the film thickness of the anodized film becomes non-uniform. The particle diameter of the eutectic silicon particles refers to a value obtained by measuring the long side and the short side of the eutectic silicon particles with an electron microscope and obtaining (long side + short side) / 2 using the measured value.

  The length of the eutectic region 66 at the interface 27s is smaller than that of the eutectic region immediately after casting due to the polishing process before anodic oxidation. This polishing process will be described in detail below.

  FIGS. 7A and 7B schematically show the cross section of the propeller body 81 formed by casting and the structure of the tissue at the position of the depth t from the surface 81s. Due to the casting, a eutectic region 83 is precipitated in the alloy phase 82 in the vicinity of the surface 81 s of the propeller body 81. The eutectic region 83 includes eutectic silicon particles 84. When the propeller body 81 is formed by the die casting method, the length of the eutectic region 83 is about 10 μm to 50 μm.

  A shot material is projected from the surface 81s of the propeller body 81, and the propeller body 81 is polished. When the shot material collides with the surface 81s of the propeller body 81, kinetic energy is given to the vicinity of the surface 81s of the propeller body 81, and the eutectic region 83 located in the vicinity of the surface 81s is crushed. As a result, as shown in FIG. 8A, a propeller body 81 'in which the refined eutectic regions 83' are distributed in the vicinity of the surface 81s' is obtained. Since the shot material polishes the surface 81s' of the propeller body 81 ', the roughness of the surface 81s' increases.

  Since the anodic oxide film 27c (FIG. 5) is formed by oxidizing the vicinity of the surface of the propeller body 81 ′, at least the eutectic region 83 ′ in the area converted to the anodic oxide film 27c is subjected to the polishing treatment. It is preferable that the material is crushed and reduced in size. As shown in FIG. 8 (a), if the region from the surface 81s ′ to the depth t is converted into an anodized film, the anodized film and the propeller body 81 ′ are located at the position of the depth t. An interface is formed. Therefore, as shown in FIG. 8B, at the position from the surface 81s ′ to the depth t, the position from the surface 81s ′ to the depth t so that the eutectic region 83 ′ has the length in the above-described range. It is preferable that the eutectic region 83 ′ is crushed.

  Although the eutectic region 83 ′ is crushed by the polishing process, the eutectic silicon particles 84 in the eutectic region 83 ′ are hardly crushed.

  The blasting process is performed under such a condition that the eutectic region 83 'is crushed at the position of the depth t from the surface 81s' and has a length in the above-described range. For example, a steel ball having a size of 0.4 mm to 1.2 mm is used as the shot material.

  If the polishing process is applied excessively, the eutectic region inside the propeller body is also crushed. From the viewpoint of forming an anodic oxide film having a uniform thickness, there is no problem even if the eutectic region inside the propeller body is crushed. However, under such conditions, the surface 81s' is greatly scraped by the shot material, and the surface roughness increases. As a result, the roughness Rz of the propeller surface after forming the anodized film exceeds 40 μm, and when the propeller is attached to the outboard motor, sufficient propulsive force cannot be obtained. Therefore, it is preferable to perform the polishing process in a range where the roughness Rz of the surface 81s' does not exceed 40 μm. Further, according to a detailed examination by the inventors of the present application, when the surface roughness Rz of the anodic oxide film after the blast treatment is smaller than 25 μm, the blast treatment is not sufficient and the anodic oxide film is obtained so that a uniform anodic oxide film is obtained. It was found that the crystal region was not reduced.

  When the eutectic region is polished so that the length of the eutectic region is 18 μm or less and the anodized film is formed so that the minimum film thickness is 20 μm or more, the difference between the maximum thickness and the minimum thickness of the anodized film Becomes 25 μm or less, and the thickness of the anodized film can be made uniform.

  The propeller of the present invention is manufactured, for example, by the following procedure. As shown in FIG. 9, first, for example, an aluminum alloy having a composition of Al-4Mg-0.8Fe-0.4Mn is melted (step S101), and the molten metal is injected into a mold having the shape shown in FIG. 3 by die casting. (Step S102). After cooling, the gate for pouring molten metal is cut from the propeller body taken out from the mold, and cutting is performed so that the propeller body has a predetermined shape, such as adjustment of the thickness and shape of the blades (step S103).

Next, the propeller body is subjected to a blasting process as described above (step S104). Before or after the blasting treatment, a treatment for removing foreign matter or the like on the surface of the propeller body may be performed by mechanical, chemical, or electrical treatment. Thereafter, the surface of the propeller body is degreased and etched (step S105), and after the surface of the propeller is cleaned, anodization is performed (step S106). For example, a 17% sulfuric acid bath is used, the propeller body is used as an anode, and oxidation is performed at a constant current of 4 A / dm ² for 30 minutes while maintaining a bath temperature of 4 ° C. As a result, an anodized film having a thickness of 40 μm and a hardness of 400 Hv is obtained.

  Next, dyeing is performed as necessary (step S107). Dyeing can be performed by coloring with a dye, electric field coloring, or the like, and is performed by depositing a dye or metal oxide in the fine pores of the anodized film. Thereafter, a micropore sealing process is performed so as not to cause decolorization or corrosion resistance (step S108).

  Thereafter, a bush is press-fitted into the hub of the propeller (S109), and after completion inspection (S110), the propeller is completed.

  The propeller 27 having such a structure is excellent in wear resistance because the surface is covered with a hard anodic oxide film. The anodic oxide film is obtained by anodizing the surface of the propeller body formed by casting after the blast treatment. For this reason, the nonuniformity of the composition in the vicinity of the surface of the propeller body, such as a eutectic precipitated by casting, is improved by the blast treatment, and an anodic oxide film having a uniform film thickness is obtained. Accordingly, problems such as partial wear and corrosion are unlikely to occur, and the product life as a propeller is long. In particular, the propeller surface can be prevented from being worn even in water mixed with sand. For this reason, it is excellent also in economical efficiency. Furthermore, since the thickness of the anodic oxide film is uniform, unevenness of color and the like is unlikely to occur on the appearance of the propeller, and a propeller excellent in aesthetic appearance can be obtained.

  Therefore, according to the ship provided with the outboard motor of the present invention, it is possible to prevent the propeller from being worn even when sailing in shallow sand. For this reason, when used in the near sea or rivers for the purpose of fishing, business, leisure, etc., the ship equipped with the outboard motor of the present invention exhibits excellent durability and is economical.

(Experimental example 1)
In order to confirm the effect of the present invention, the surface of the propeller body formed by two casting methods is subjected to a polishing process under various conditions, and then an anodized film is formed to prepare a sample, physical characteristics, etc. I investigated. For comparison, a sample that was not subjected to the polishing treatment was prepared and the characteristics were compared. The results are shown in Table 1 below.

  The propeller bodies of Samples 1 to 5 were manufactured by die casting using an aluminum alloy having a composition of Al-4Mg-0.8Fe-0.4Mn-0.3Si. The propeller bodies of Samples 6 to 8 were produced by gravity casting using an aluminum alloy having a composition of Al-7Si-0.4Fe-0.3Mg.

  The propeller bodies of Samples 2 to 5, 7 and 8 were subjected to a polishing process under different conditions. For comparison, the propeller bodies of Samples 1 and 6 were not subjected to the polishing treatment.

  The characteristics of the prepared samples were evaluated as follows.

(Eutectic silicon particle size and eutectic region size)
Each size at the interface between the propeller body and the anodized film was determined by SEM observation.

(Surface roughness)
The surface roughness Rz (ten-point average roughness) of the anodized film was measured using a surface roughness measuring instrument by the method defined in JIS B0601.

(Film thickness)
The thickness of the anodized film was determined by observing the cross section of the anodized film with a metal microscope.

(appearance)
The quality of the appearance was visually determined at a position 300 mm away from the sample surface due to diffuse daylight. O and X indicate that the appearance was uniform and non-uniform, respectively.

(Abrasion resistance)
A sand drop wear test specified in JIS H8501 was conducted for a certain period of time and judged by appearance. ○ indicates that the propeller body, which is the base material, is not exposed, and × indicates that the propeller body is exposed.

(Performance test)
A sample was attached to an outboard motor having a predetermined output, and the engine was driven at a predetermined number of revolutions in a predetermined section to measure the required time. Moreover, the required time was measured by the same method using the conventional propeller which has the film by coating. ○ indicates that the result was comparable to the time required for the conventional propeller, and × indicates that the time required was significantly longer than the time required for the conventional propeller.

(Judgment)
In the evaluation of the wear resistance and performance test, a sample having one or more evaluation items determined as x was determined as x.

  As can be seen from Table 1, the size of the eutectic region is reduced by performing the blast treatment. Moreover, it turns out that a eutectic area | region becomes small in general, so that the polishing process time becomes long. However, Samples 4 and 5 have the same eutectic region size although the polishing time is different. Therefore, it is considered that the effect of crushing the eutectic region by the blast treatment in about 120 seconds is saturated. Similar results were obtained with samples 7 and 8.

  On the other hand, the size of the eutectic silicon particles does not change regardless of the blast treatment. That is, it is considered that the eutectic silicon particles are not crushed by the polishing process.

  The surface roughness of the anodized film increases as the polishing time increases. The difference δ between the maximum film thickness and the minimum film thickness of the anodized film is generally smaller as the eutectic region is smaller. Therefore, it can be said that the uniformity of the film thickness of the anodized film can be improved by reducing the size of the eutectic region by the blast treatment. However, when the samples 4 and 5 are compared with the samples 7 and 8, the difference δ between the maximum film thickness and the minimum film thickness is the sample 4, 5 although the eutectic region of the samples 7 and 8 is smaller. Is bigger than. This is because the eutectic silicon particles have a larger particle size in the samples 7 and 8, so the samples 7 and 8 have a higher silicon content in the eutectic region, and an anodic oxide film is less likely to be formed. It seems to be because it has become.

  Out of the obtained samples, the appearances of Samples 1 and 6 were non-uniform. This is considered to be due to the fact that the film thickness of the anodized film is nonuniform due to the large eutectic region.

  As for the wear resistance, Samples 4, 5, 7, and 8 having a minimum film thickness of 20 μm or more in the anodized film showed good results. In Samples 1 and 2, if the anodic oxidation film is formed so that the minimum anodization time is increased to 20 μm or more in the samples 1 and 2, it can be considered that the evaluation in wear resistance is improved. Since it is uniform, it is considered that it is necessary to perform anodization for a very long time in order to make the minimum film thickness 20 μm or more.

Regarding the performance test, the evaluation of the samples 7 and 8 is worse. This is considered to be because the propeller surface roughness exceeds 40 μm, so that a sufficient driving force cannot be obtained. In particular, Sample 8 was ground to such an extent that the propeller was deformed by the blasting process or did not have a predetermined thickness.

  From these results, it can be seen that it is effective to reduce the eutectic region by scouring treatment in order to make the thickness of the anodic oxide film uniform. In particular, samples 4 and 5 in which the length of the eutectic region is 18 μm or less and the particle size of the eutectic silicon particles is 0.8 μm or less are excellent in wear resistance and are durable marine propellers. It turns out that it is suitable.

(Experimental example 2)
A propeller of Sample 5 was attached to an outboard motor (Yamaha Motor Co., Ltd .: F40BWHDL-00000008) mounted on a ship (Yamaha Motor Co., Ltd .: W-23AF1). The throttle was operated so that the engine speed was constant at 1000, 2000, 3000, 4000, and 5000 RPM, and the speed of the ship at each speed was measured. This measurement was repeated several times, and the average arrival speed at each rotation number was determined. For comparison, a conventional sample in which a protective film by coating was formed on the propeller body that had been subjected to the polishing treatment under the conditions of Sample 2 instead of the anodized film was prepared, and the same measurement was performed. The surface roughness of the conventional sample was Rz = 1.5 μm.

  Moreover, these two samples were attached to an outboard motor mounted on a ship, and a monitor test using the ship for 160 days was performed in a usage environment where the sandy coast was moored. The above-described measurement was performed again for each sample after the monitor test.

  As is apparent from Table 2, the surface roughness Rz of the propeller of Sample 5 is 40 μm, but Sample 5 has the same driving force as that of the conventional product. In addition, it can be seen that the sample 5 after the monitor test has the same driving force as that immediately after the production, and the propeller is hardly worn. On the other hand, the arrival speed is reduced in the conventional product. In particular, at the time of high rotation (4000, 5000 RPM), the reaching speed is reduced by about 10 to 20%, and the propulsion force is reduced due to propeller wear.

  FIG. 10 shows a shape obtained by projecting the propellers of the sample 5 and the conventional sample after the monitor test onto a plane perpendicular to the axis. In FIG. 10, the projected shape 100 immediately after the preparation of the sample is indicated by a solid line. The projection shape 101 of the sample 5 after the monitor test almost coincides with the projection shape 100 immediately after the preparation of the sample. On the other hand, the projection shape 102 of the conventional sample after the monitor test is smaller than the projection shape 100. Specifically, the vicinity of the tip of the blade is reduced by cutting. This is considered that the tip of the blade portion was worn by sand or the like. Thus, when the area of the blade portion is reduced, the amount of water ejected backward by the rotation of the propeller is reduced, and as a result, the propulsive force is reduced. As a result, fuel consumption also deteriorates.

  From these results, it can be seen that the propeller of the present invention can prevent a decrease in propulsive force due to wear and is excellent in economic efficiency.

  The marine propeller and the outboard motor of the present invention are suitably used for various ships, and in particular, are suitably used for small ships used for various purposes such as fishing, business, and leisure.

(A) It is a side view which shows the ship provided with the outboard motor by this invention, (b) is a side view of the ship provided with the propeller for ships by this invention. It is a side view which shows embodiment of the outboard motor of this invention. It is a top view which shows embodiment of the propeller of the outboard motor by this invention. It schematically shows the structure obtained when the propeller body is anodized without performing the scouring process. It is a figure which shows the partial cross section in the blade | wing part of the propeller of FIG. In FIG. 5, it is a figure which shows typically the structure of the structure | tissue in the interface with the anodic oxide film of a propeller main body. (A) is a figure which shows typically the structure structure of the cross section of the propeller main body after casting, (b) is a figure which shows the structure structure in the position of the depth t from the surface typically. (A) is a figure which shows typically the structure | tissue structure of the cross section of the propeller main body after a blasting process, (b) is a figure which shows typically the structure | tissue structure in the position of the depth t from the surface. It is a flowchart which shows the manufacturing process of the propeller shown in FIG. The example after the monitor test and the projection figure of the conventional propeller are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cowling 12 Stern 14 Casing 16 Clamp 21 Drive shaft 22 Steering handle 25 Clutch device 27 Propeller 27b Propeller body 27c Anodized film 31 Forward gear 33 Reverse gear 50 Ship 51 Ship body 52 Outboard motor 61 Blade part 62 Hub part 65, 84 94 Eutectic silicon particles 66, 83, 93 Eutectic region 82 Alloy phase 73 Bush

Claims (20)

A propeller body having a blade portion and a hub portion, the propeller body formed by casting an aluminum alloy;
An anodized film provided so as to cover the surface of the propeller body, and an anodized film obtained by anodizing the surface after the surface of the propeller body is cleaned. Propeller for.   2. The marine propeller according to claim 1, wherein the aluminum alloy contains silicon, and a length of a eutectic region containing eutectic silicon particles is 18 μm or less at an interface between the propeller body and the anodized film.   The marine propeller according to claim 2, wherein the surface roughness Rz of the anodized film is 25 μm or more and 40 μm or less.   The marine propeller according to claim 3, wherein the anodized film has a thickness of 20 μm to 100 μm.   The marine propeller according to claim 4, wherein the anodized film has a hardness of 350 Hv or more and 450 Hv or less.   The marine propeller according to claim 1, wherein the propeller body is formed by die casting using the aluminum alloy.   The marine propeller according to claim 2, wherein the eutectic silicon particles in the eutectic region have a particle size of 0.8 µm or less at the interface.   The marine propeller according to claim 4, wherein the aluminum alloy is an Al-Mg alloy containing 0.3 wt% or more and 2.0 wt% or less of silicon.   An outboard motor equipped with a marine propeller defined in any one of claims 1 to 8.   A ship provided with a marine propeller as defined in claim 9. A propeller body obtained by die casting of an aluminum alloy containing silicon in a proportion of 0.3 wt% to 2.0 wt%;
An anodized film provided on the surface of the propeller body;
With
The marine propeller, wherein the anodized film has a thickness of 20 μm or more and 100 μm or less, and a difference between the maximum thickness and the minimum thickness of the anodized film is 25 μm or less.   The marine propeller according to claim 11, wherein the anodized film has a hardness of 350 Hv to 450 Hv. A step (A) of forming a propeller body having a blade portion and a hub portion by casting an aluminum alloy;
A step (B) of polishing the surface of the propeller body;
A step (C) of forming an anodic oxide film so as to cover the surface of the propeller body by anodizing the propeller body subjected to the blast treatment;
For manufacturing a marine propeller.   The aluminum alloy contains silicon, and the blast treatment in the step (B) is performed so that the length of the eutectic region containing silicon is 18 μm or less at the interface between the propeller body and the anodized film. A method for manufacturing a marine propeller according to claim 13.   The marine propeller manufacturing method according to claim 13, wherein the blast treatment in the step (B) is performed so that the surface roughness Rz of the anodized film is 25 μm or more and 40 μm or less.   The method for manufacturing a marine propeller according to claim 13, wherein in the step (C), the time for the anodization is adjusted so that the anodized film having a thickness of 20 μm to 100 μm is formed.   14. The method for manufacturing a marine propeller according to claim 13, wherein in step (C), the concentration and temperature of the electrolytic bath for anodization are adjusted so that the anodized film having a hardness of 350 Hv to 450 Hv is formed.   The said process (A) is a manufacturing method of the marine propeller of Claim 13 which shape | molds the said propeller main body by the die-casting method.   The method for manufacturing a marine propeller according to claim 14, wherein the forming in the step (A) is performed so that a particle diameter of silicon in the eutectic region is 0.8 μm or less at the interface.   The method for manufacturing a marine propeller according to claim 13, wherein the aluminum alloy is an Al—Mg alloy containing 0.3 wt% or more and 2.0 wt% or less of silicon.

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