JP4198043B2 - Electrolytic corrosion prevention structure of the clamp that improves corrosion resistance - Google Patents

Description

  The present invention relates to a structure for preventing electrolytic corrosion of a clamp that improves corrosion resistance.

  With respect to the conventional clamp structure, as shown in FIG. 4, the bolt 74 is passed through the second boss 79, and the bolt 74 is screwed into the screw hole formed in the first boss 78, thereby sandwiching the slit 75. The separated first and second boss portions 78 and 79 were tightened.

  In addition, there exist some which are disclosed by patent document 1 in the structure of a clamp.

  By the way, when two different metals are brought into contact, there is a problem that the contact portion is corroded by electrolytic corrosion.

  For example, when a magnesium (Mg) alloy member, which is a light alloy, is fastened using an iron-based bolt, electrical corrosion (electric corrosion) between Mg and iron occurs in the presence of moisture. In particular, when used in parts that are subject to muddy water such as undercarriages of motorcycles and automobiles, and parts that are prone to snow melting salt in snowy areas, moisture adhesion in the presence of electrolytes (Na +, Ca2 +, Cl-, etc.) Electric corrosion may progress violently.

In order to solve this problem, in general, an insulating coating is formed on the surface of the bolt 74 to form an insulating layer, thereby preventing electric corrosion.
Japanese Patent Laid-Open No. 11-240479

  However, in the conventional clamp structure, the slit 75 has a considerably large gap in order to reduce the thickness due to weight reduction. Corrosion factors such as rain and muddy water entered through this gap, and electric corrosion was induced between the bracket 71 and the bolt 74.

  Accordingly, an object of the present invention is to solve the above-described problems, and to provide an electrolytic corrosion prevention structure for a clamp that prevents corrosion factors from entering through a gap between slits and prevents electrolytic corrosion.

To achieve the above object, according to a first aspect of the present invention, there is provided an electroerosion prevention structure for a light alloy clamp in which first and second boss portions facing each other through a gap are fastened through an iron-based bolt. An insulating coating layer having an insulating property is formed at least on the surface of the bolt, flat first and second slit surfaces facing each other are formed on the first and second boss portions, and the clamp is fastened, A slit having a maximum width of 1.2 mm or less is formed between the second slit surfaces and the clamp is fastened, the slit has a wedge-shaped cross-sectional shape, and the tips of the first and second boss portions are brought into contact with each other. It was .

  In a second invention, in the first invention, the maximum width of the slit is set in a range of 0.8 mm to 1.2 mm in a state where the clamp is fastened.

According to the first invention, in the state where the first and second boss portions are fastened through bolts, the flat first and second slit surfaces are formed with slits for preventing the invasion of corrosion factors. The clamp is sufficiently tightened while leaving a tightening margin, and a corrosion factor is prevented from entering between the first and second boss portions from the outside, and corrosion due to electrolytic corrosion can be suppressed.
The slit has a wedge-shaped cross-sectional shape, and the first and second slit surfaces are brought into contact with each other so as to partially close the slit so that a corrosive factor such as water from the outside is first and second. It is possible to effectively prevent intrusion between the two boss portions and to suppress corrosion due to electrolytic corrosion.

  According to the second invention, the maximum width of the slit is set to 0.8 to 1.2 mm, thereby effectively preventing a corrosive factor such as water from entering between the first and second boss portions from the outside. Corrosion due to electric corrosion can be suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows the structure of the clamp of this embodiment.

  The clamp 50 is applied to a mounting portion of a front fork for a motorcycle.

  The bracket 1 is connected to the steering shaft of the motorcycle and supports the outer tube 18 of the front fork via the clamp 50.

The clamp 50 tightens the first and second boss portions 8 and 9 that face each other via the slit 5 via the bolt 4 to reduce the diameter of the fork hole formed in the bracket 1, and the outer tube of the front fork Tighten and fix 18.

  FIG. 2 is a cross-sectional view showing a fastening portion of the clamp 50.

  The bolt 4 is passed through the bolt hole 15 of the second boss portion 9, and the bolt 4 is screwed into the screw hole 31 formed in the first boss portion 8. The boss portion 8 is pressed and fastened.

  Flat first and second slit surfaces 11 and 12 were formed on the surfaces of the first and second boss portions 8 and 9 facing each other.

  The first and second slit surfaces 11 and 12 form a slit 5 therebetween.

  The slit 5 is configured so that the maximum width of the slit 5 is 1.2 mm or less, preferably 0.8 mm to 1.2 mm in a state where the first and second boss portions 8 and 9 are fastened with the bolt 4.

  Specifically, the outer tube 18 has a diameter of 50 mm, and the bolt 4 is tightened with a torque of 18 to 28 N · m (preferably 23 N · m). At this time, the first and second slit surfaces 11 and 12 form a wedge-shaped slit 5 having a cross-sectional shape. At the tip 5a of the slit 5, no gap is opened, and the first and second boss portions 8, 9 are in contact with each other. The gap at the base end 5b of the slit 5 is 1.2 mm or less.

  The bracket 1 is made of a light alloy magnesium alloy, and the bolt 4 is made of an iron-based material.

  Anodizing treatment or chemical conversion treatment and coating are applied to the surface of the bracket 1 of the magnesium alloy member.

  A fluororesin coating layer was formed on the entire surface of the bolt 4 as an insulating coating layer having insulating properties.

  The surface treatment for forming the fluororesin coating layer on the surface of the bolt 4 is performed by applying a base treatment to the surface of the bolt 4 and then applying a coating film made of, for example, tetrafluoroethylene-based fluororesin paint to a thickness of 20 to 30 μm Form with.

  The coating film made of a tetrafluoroethylene-based fluororesin coating formed on the surface of the bolt 4 has high adhesion to the surface of the iron-based bolt 4 and is not easily cracked or peeled off, so that insulation can be maintained.

  The electrolytic corrosion preventing structure of the clamp 50 is configured as described above, and has the following effects.

  By forming the slit 5 having a maximum width of 1.2 mm or less on the flat first and second slit surfaces 11 and 12 in a state in which the first and second boss portions 8 and 9 are fastened via the bolt 4, The clamp 50 is sufficiently tightened with the clamping allowance of the clamp 50, and the corrosion factor is prevented from entering between the first and second boss portions 8 and 9 from the outside, thereby suppressing corrosion due to electrolytic corrosion. It is done.

  By setting the maximum width of the slit 5 to 0.8 to 1.2 mm, it is possible to effectively prevent a corrosive factor such as water from entering between the first and second boss portions 8 and 9 from the outside. Corrosion caused by can be suppressed.

  The slit 5 has a wedge-shaped cross-sectional shape, and the front end portions 11a and 12a of the first and second slit surfaces 11 and 12 are brought into contact with each other so as to partially close the slit 5 to corrode water or the like from the outside. It is possible to effectively prevent the factor from entering between the first and second boss portions 8 and 9, and to suppress corrosion due to electrolytic corrosion.

  In the present embodiment, the fluorine-based coating layer is used as the insulating layer. However, the present invention is not limited to this, and other coatings may be used as long as the coating is hard and smooth and has insulating characteristics.

  In the present embodiment, the fluorine-based coating layer is formed on the surface of the bolt 4 as the insulating layer, but it may be formed on the inner surface of the bolt hole 15. Of course, a fluorine-based coating layer may be formed on both the surface of the bolt 4 and the inner surface of the bolt hole 15.

  FIG. 3 shows a second embodiment.

  In this embodiment, there is no restriction on the gap of the slit 5. An O-ring that is a seal member 20 is interposed in the slit 5. The seal member 20 is not limited to an O-ring, and a packing material such as NBR is used.

  Since the sealing material 20 is interposed between the first and second slit surfaces 11 and 12 with the first and second boss portions 8 and 9 being fastened via the bolts 4, the clamping allowance of the clamp 50 remains. Thus, the clamp 50 is sufficiently tightened, and it is possible to reliably prevent the corrosion factor from entering between the first and second boss portions 8 and 9 from the outside, and to suppress corrosion due to electrolytic corrosion.

  Although the present invention has been described in certain terms with regard to structural and methodological features, the means disclosed herein include preferred forms of practicing the invention, and the invention is illustrated and described. It is not limited to specific features. Accordingly, the present invention includes any forms or modifications within the scope of the claims as appropriately interpreted in accordance with the principle of equality.

  The present invention can be applied to various clamps such as a clamp that supports a front fork of a motorcycle, other front fork parts, a pump cover, and valves.

It is a figure which shows the electrolytic corrosion prevention structure of the clamp of 1st Embodiment. It is sectional drawing which shows the electrolytic corrosion prevention structure of the clamp of 1st Embodiment. It is a figure which shows the electrolytic corrosion prevention structure of the clamp of 2nd Embodiment. It is a figure which shows the conventional clamp structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bracket 4 Bolt 5 Slit 6 Head 8 1st boss | hub part 9 2nd boss | hub part 11 1st slit surface 12 2nd slit surface 15 Bolt hole 20 Sealing material 50 Clamp

Claims (2)

In the electrolytic corrosion prevention structure of the light alloy clamp that fastens the first and second boss portions facing each other through a gap via an iron-based bolt,
Forming an insulating coating layer having insulating properties on at least the surface of the bolt;
Forming flat first and second slit surfaces facing each other on the first and second boss portions;
In a state where the clamp is fastened, a slit having a maximum width of 1.2 mm or less is formed between the first and second slit surfaces ,
A structure for preventing galvanic corrosion of a clamp , wherein the slit has a wedge-like cross-sectional shape in a state in which the clamp is fastened, and the tip portions of the first and second boss portions are in contact with each other .   The structure for preventing electrolytic corrosion of a clamp according to claim 1, wherein the maximum width of the slit is set in a range of 0.8 mm to 1.2 mm in a state where the clamp is fastened.

Images