JPS5822336B2 - Polyamide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for fitting and fixing a metal boss to a ring-shaped object such as a polyamide resin molded article, such as a gear, a wheel, or a roll.

The object thereof is to provide a method for reliably and firmly fitting and fixing a metal boss to a molded product made of polyamide resin as described above with a simple operation.

In recent years, it has become common practice to manufacture gears and other items using polyamide resin, but although parts with a small load can be made of only polyamide resin, parts with a large load cannot be made of polyamide resin alone. It cannot be used because the strength of the keyway is low.

Therefore, a method has been adopted to strengthen the keyway by fixing a metal boss, but the conventional method has the following drawbacks.

In other words, processing of polyamide resin and metal bosses is complicated and productivity is low, and when used in a high-temperature atmosphere when applied to gears, for example, when the number of bolts is small, the coefficient of thermal expansion of polyamide resin is lower than that of metal. Since it is approximately 10 times larger than the above, the gear teeth will be deformed.

To prevent this phenomenon, it is necessary to use fixing bolts and increase the number of bolts, which further increases the cost of the product.

Furthermore, if the gear has a complicated shape or has a thin tooth width, it is difficult to fix the gear with bolts.

Conventionally, methods for heating the metal boss to melt polyamide resin include oil immersion, electric furnace or hot air dryer, but methods using electric furnace and hot air dryer have lower temperature. Because control and uniform heating are difficult, there are parts of the polyamide resin that are in contact with the metal bosses that do not completely melt or that carbonize, making it impossible to obtain the necessary fixing strength.

Furthermore, although the oil immersion method allows for uniform heating, it has the disadvantage that post-treatment to remove the oil is very time-consuming.

The present invention eliminates these drawbacks of the conventional method, and its gist is that when fitting and fixing a metal boss to a molded product made of polyamide resin, the drying loss rate of the molded product is set to 0.5 coefficient or less, and A polyamide resin molded product having an inner diameter with a shrinkage fit of 0.4 to 3 factors relative to the outer diameter of the metal boss is heated and expanded, the metal boss is fitted into the molded product for shrink fitting, and then this is subjected to high frequency heating. The present invention resides in a method for fixing a metal boss to a polyamide resin molded article, characterized in that the metal boss and the polyamide resin are welded by doing so.

In the present invention, the most typical example of the polyamide resin molded article is a gear.

Compared to conventional fixing methods, 1) metal bosses and polyamide resin can be easily processed, making it cheaper to manufacture;
) Since the polyamide resin and the metal boss are bonded at their contact surfaces, the teeth do not deform during thermal expansion.

(3) Since no fixing devices such as bolts are used, the head of the bolt does not stick out and get in the way. (4) The shape of the metal boss itself is simple, so even special gears can be manufactured easily. Furthermore, after shrink fitting the metal boss,
Since the metal boss is heated by high frequency and the adjacent polyamide resin is welded and blended together, it has the advantage that a product with extremely low residual strain can be obtained.

Furthermore, if a silane coupling agent is used as a binder if necessary, it is recognized that the polyamide resin and the metal boss are bonded extremely strongly.

In the present invention, the metal boss usually has a pitch of, for example, 2 mr.
Although it is desirable to perform knurling (mesh-like unevenness) to the level of IL or appropriate groove processing, it is recognized that the radial strength increases significantly when further treatment with a silane coupling agent is performed.

Similarly, nylon primer treatment has conventionally been carried out as a pretreatment for nylon resin coating, but in the present invention, it can be used as a binder between the metal boss and the polyamide resin, and can exhibit excellent bonding strength.

As mentioned above, the polyamide resin molded product that fits into this
For gears and various other ring-shaped objects, it is important to select the shrinkage fit and drying loss rate within a certain range.

Therefore, a wire fit allowance of 0.4 to 3% is appropriate.

If this range is exceeded, shrink fitting becomes difficult, and the residual stress caused by shrink fitting is too large, making it easy for cracks to occur when machining gear teeth.If it is below this range, the fixing strength decreases, making it unsuitable for use. It becomes unbearable and sufficient effects cannot be achieved.

In particular, when the temperature of the gear increases during use, the fixing strength decreases extremely.

Furthermore, since the polyamide resin has high water absorption and contains other volatile components, it must be thoroughly dried, and the loss on drying must be less than 5%.

When heated above this value, volatile content (mainly water)
evaporates and significant bubbles are generated in the resin, reducing the fixing strength and making it unusable.

A metal boss is heat-fitted to the polyamide resin molded product prepared in this way, and the metal boss is heated by placing it in a high-frequency heating coil to weld the polyamide resin adjacent to the metal surface.

In this case, the frequency is usually 80-400 KHz, the voltage 1-
15KV, current 0.1~10A1 heating time 30~300
Select from a range of seconds.

After heating is completed, the cooling means is not particularly limited as long as it is allowed to cool in the air.

Example 1 After knurling the circumferential surface of a cylindrical steel material with a diameter of 60 mm and a thickness of 301n7IL with a pitch of 2 cages, the surface is degreased.

One side diameter: 110 mm, thickness: 30 mm, boss hole diameter: 59.4 mm
(shrink fit 1%) polyamide resin gear from 120~
The cylindrical steel material was dried in an atmosphere of 150°C for 2 hours to remove volatile components to a coefficient of 0.5 or less. In this heated state, the cylindrical steel material was shrink-fitted to a polyamide resin gear, and this was attached to the inner path 1.
Insert into 10CrfL cylindrical coil, frequency 200KH
z, voltage 3.8KV, current 1. Heating was performed for 60 seconds with OA to generate heat and weld the metal cylinder.

After completion of the process, it was left to cool in the air to obtain a polyamide resin gear to which a metal boss was fixed.

The metal boss fixing strength in the radial direction was measured and was 32
A torque of kg·m was obtained.

Example 2 After degreasing and washing a cylindrical steel material with water, a solution prepared by diluting a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., KBM403) with methyl alcohol to an amount of 25% of the active ingredient was applied,
The same procedure as in Example 1 was carried out except that it was dried at 130° C. for 10 minutes.

As a result of measuring the metal boss fixing strength in the radial direction, the torque was 175 kg·m.

Example 3 In place of the silane coupling agent in Example 2, a nylon brimer agent (Varcum 2896-131 manufactured by American Polymer Co., Ltd.) was used, and as a result, the torque was 105 kg.
It was m.

Claims (1)

[Claims] 1. When fitting and fixing a metal boss to a polyamide resin molded product, the drying loss rate of the molded product shall be 0.5 coefficient or less, and the shrink fit allowance shall be 0.4 to 3 coefficients relative to the outer diameter of the metal boss. A product made of polyamide resin characterized by heating and expanding a polyamide resin molded product having an inner diameter given by heating, inserting a metal boss into the molded product, shrink-fitting it, and then welding the metal boss and polyamide resin by high-frequency heating. A method of fixing metal bosses to molded objects.