JPS61238592A - Coupling structure of stern shaft mechanism - Google Patents

Abstract

PURPOSE:To improve insulation and get good creep-resistance by using sprayed ceramic coating film as an insulating material for the coupling of the propeller shaft mechanism. CONSTITUTION:A propeller shaft 3 and an intermediate shaft 4 are connected through a coupling member 6. Strayed ceramic coating film 10 is formed for insulation in this portion. The portion to be insulated by spraying include meeting surfaces A of a pair of flanges 6-1, 6-2 of the coupling member 6, the shank surface B of a coupling bolt 7 and the head lower surface C of the coupling bolt 7.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention aims to prevent damage (spark erosion) to the main engine crankshaft caused by electrical discharge caused by a potential difference between the stern shaft system and the hull of a ship. This relates to an insulated joint in the stern shaft system.

[Conventional technology]

The hull of a ship is usually made of iron and has low seawater resistance, while the propulsion propeller is made of copper alloy and has high seawater resistance. Therefore, anti-corrosion measures such as painting are generally applied to ship bodies.

By the way, the natural potentials of iron and copper alloy are -550 to -650 mV and -250 to -35 mV, respectively, at the seawater silver chloride electrode level.
0 mV, but it is said that the natural potential of iron that is less likely to corrode is preferably about 150 mV or less than the above potential, so an anti-corrosion current is usually applied to -750 to -860 mV to prevent corrosion. .

However, when the propeller is stopped, the potential between the propeller and the hull is the same, but when the propeller is rotating, an oil film (oil film insulation) is formed on the bearing, resulting in a potential difference of approximately 400 to 600 mV between the two metals. It turns out.

As a result, there is a major problem in that damage (pitting) occurs to the main engine, crankshaft, and main bearing due to potential discharge (this is called spark erosion). As a measure to prevent this spark erosion, there is a method of attaching a grounding device to the intermediate shaft located between the propeller shaft and the main engine to keep the potential difference below a certain value.

However, with this method, it is difficult to install a grounding device that has low contact resistance and is highly stable over a long period of time for the propulsion shaft, which is a rotating body. It has the problem of being scarce.

In addition, by forcing current to flow through earth,
Fdj) Another disadvantage is that the sacrificial anode on the body side becomes extremely worn out.

Therefore, a method has been proposed in which electrical insulation is applied to the shaft joints of the propulsion shaft system, but this is maintenance-free and completely 8-year-old.
& It is considered to be a method with excellent functional reliability.

[Problem that the invention seeks to solve]

Currently, resin-based (FR) is used as insulation material for propulsion shaft joints.
Although insulating plates and linings (P) have been applied, they have poor creep resistance, cause looseness during use, and cannot withstand long-term use, so they are not yet sufficient as a practical technology.

[Means for Solving the Problems] The present invention employs a ceramic sprayed coating as the above-mentioned insulating material.

Hereinafter, the present invention will be described in detail with reference to the drawings.

In the figure, 1 indicates an iron-based (Fe) hull, and 2 indicates a copper alloy-based (Cu) propeller. 3 is the propulsion propeller shaft, 4
is an intermediate shaft, and a main engine 5 such as a crankshaft (not shown) is connected to the intermediate shaft 4.

The propeller shaft 3 and intermediate shaft 4 are connected via a joint member 6, and a thermal spray coating 10 is applied to this portion for insulation. This joint part t! ' 6 is a pair of flanges 6
-L 6-2 Align the end faces, both flanges 6-L 6-2
are connected by a plurality of joint ports 7. As shown in FIG. 2, the locations where thermal spray insulation is applied are the mating surfaces A of the pair of flanges 6-1 and 6-2, the body peripheral surface B of each joint port 7, and the joint port 7. and the lower surface C of the head.

In this case, the mating surface A of the flange 61.6-2 does not necessarily need to be thermally sprayed on both sides, and either one side may be used.

Next, as the thermal spray coating 10, ceramic-based coatings, particularly alumina-based coatings (for example, Al1 oa) are preferable from the viewpoint of insulation properties. Although the thickness of the thermal spray coating 10 is not particularly limited, it is required to be at least 100 μm from the viewpoint of insulation resistance.

However, if it is too thick, there is a problem of peeling, so 5
00! It is better not to exceed tm.

Further, although thermal spraying does not require special limited thermal spraying conditions, in order to improve the adhesion of the thermal spray coating 10, +1. l Plast the surface with scale glisotho, etc. (2) Preheat the base material to about 150℃+31 Ni
-Cr, Ni- is thermally sprayed with a metal of No. 1 as a base layer, etc., to form a ceramic to the required thickness as described above.

After thermal spraying, the surface is polished to an appropriate thickness if necessary.

〔Effect of the invention〕

As described above, according to the present invention, not only can the required insulation properties be obtained extremely easily, but also the creep resistance is extremely superior to that of conventional products, and it can withstand long-term use, making it suitable as a practical technology. The value is very high.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the stern shaft system, and FIG. 2 is an explanatory diagram of insulated parts of the joint in the stern shaft system.

Claims (1)

[Claims] 1. At the joint between the propeller shaft for marine propulsion and the main engine, one or both of the mating surfaces of a pair of flanges forming the joint, the circumferential surface of the body of the joint bolt, and the head of the joint bolt. A stern shaft joint structure characterized by a ceramic sprayed coating formed on the lower surface.