JPS5924286B2 - Oil-free bearing - Google Patents

Description

[Detailed description of the invention] This invention relates to an oil-free bearing.

BACKGROUND ART Conventionally, bearings have been widely molded using synthetic resins such as polyamide, polyethylene, polyacetal, polybutylene phthalate, polycarbonate, and polytetrafluoroethylene.

All of the above synthetic resins have excellent physical properties such as self-lubricating properties and wear resistance, so when used as bearings, there is no need for lubrication, making them very useful bearings. The scope of use was limited to bearings operated under light loads, and the disadvantage was that it was not suitable for use in high-load applications.

Therefore, in order to improve the friction resistance and wear characteristics of the synthetic resin and make it able to withstand higher load operation, lubricating oil has been mixed into the synthetic resin. As disclosed in Japanese Patent Application Laid-open No. 48-22133, a resin that absorbs lubricating oil is mixed in, or a rubbery substance that absorbs lubricating oil is mixed in as shown in Japanese Patent Publication No. 495-4816. However, instead of having these contaminants absorb the lubricating oil or using the above-mentioned polymeric compounds as lubricating oil-carrying substances, Japanese Patent Publication No. 48-375
As seen in No. 71, it has been proposed to use Graphift, but in the case of the former two types of polymer compounds that absorb lubricating oil, the lubricating oil absorption effect depends on the three-dimensional molecular structure of the polymer compound. This is due to the so-called swelling phenomenon in which the lubricant is absorbed between the parts, so once the lubricant is absorbed, it is difficult to leach out. However, it is difficult to
Even if the polymer compound or graphite absorbs and carries lubricating oil, there is a limit to the amount of absorption.Usually, the amount of lubricating oil per 1 volume of lubricating oil absorbent is about 3 volumes, and this is why resin When it is desired to contain a large amount of lubricating oil, a large amount of lubricating oil absorbent is naturally required, which has the disadvantage of impairing the physical properties of the base resin and reducing the mechanical strength required for the bearing.

5 Furthermore, since the absorbents that function as lubricant carriers themselves have poor lubricity, when exposed to sliding surfaces,
This has the disadvantage that it is forced to come into contact with the receiving shaft (rotating shaft), which impairs the low friction and even low abrasion properties of the bearing.

Furthermore, the oil-free bearings made of synthetic resin have a high coefficient of thermal expansion and low thermal conductivity. Therefore, it is necessary to mold them to dimensions that take into account the coefficient of thermal expansion depending on the usage conditions, which has a negative impact on dimensional stability. However, it had some drawbacks.

Therefore, the application range of oil-impregnated resin bearings is as follows: bearings for office equipment, etc. with a PV value of 400k9Ad・m/Min.
There was a problem that it was limited to those with a limit of In view of the above-mentioned drawbacks, the present inventors conducted research tests aimed at obtaining a constituent material for an oil-free bearing that can absorb a large amount of lubricating oil without impairing the physical properties of the base resin. Norbornene-based synthetic elastomers are most suitable as lubricating oil carriers, and mixing metal powder is extremely effective in improving the physical properties of bearings and at the same time imparting ductility to the exuded lubricating oil to plastics. They discovered this, and based on this knowledge, they came up with the present invention. That is, the gist of the oil-free bearing according to the present invention is that 1 to 40% by volume of lubricating oil and 0.1 to 20% by volume as the lubricating oil carrier.
It is characterized by being composed of a norbornene-based synthetic elastomer, 0.5-20% by volume of graphite as a solid lubricant, 0.5-50% by volume of metal powder, and the remainder by volume of synthetic resin. It is something.

In addition to the above, lubricating oils include spindle oil, turbine oil, machine oil, aromatic lubricating oil such as daimona oil, naphthenic lubricating oil, paraffinic lubricating oil, or hydrocarbons, esters, polyglycols, silicones, etc. Any commonly used lubricating oil such as synthetic oil may be used.

In addition, the reason why the amount of lubricating oil added is 1 to 40% by volume is 1.
If it is less than 4% by volume, sufficient lubricity cannot be expected;
This is because if it exceeds 0% by volume, there is no point in increasing the amount of lubricating oil for reasons that will be described later.

As the norbornene-based synthetic elastomer, a vulcanized blend of norbornene-based resin or polynorbornene-based resin is used. This norbornene-based synthetic elastomer is in the form of powder particles, and since these particles have an extremely porous structure, they can absorb a large amount of lubricating oil, and this absorption capacity is up to 10 volumes per 1 volume of the norbornene-based synthetic elastomer. reach

Moreover, the temperature dependence of this absorption capacity is such that the absorption amount increases as the temperature increases. Therefore, even when exposed to high temperatures during machining, the lubricating oil remains trapped, and the screws due to lubricating oil seepage. It has characteristics such as preventing slippage and causing lubricating oil to ooze out due to a decrease in absorption capacity when the product temperature drops to room temperature after processing. Therefore, if the entire constituent material of an oil-free bearing is 100% by volume, lubricating oil 1 to 4
0% by volume of norbornene synthetic elastomer.
A content of 1 to 20% by volume is sufficient.

However, if the lubricating oil is in the amount of the norbornene resin mentioned above, it is possible to contain a larger amount, but if the lubricating oil is too large, the leakage due to excessive content will be significant, so the amount of lubricating oil should be reduced to around 40% by volume. It is appropriate to set the upper limit to .

Furthermore, graphite is added as a solid lubricant to assist the lubricating effect of the lubricating oil.

This graphite includes natural graphite (scale-like, scale-like, earth-like),
Artificial graphite or the like is used, and in order to improve dispersibility and lubricity, it is desirable that the particle size is as fine as possible. Since the graphite has thermal conductivity and thermal expansion coefficient comparable to those of metals, it also contributes to improving the physical properties of the bearing like the metals described below.

The reason why the amount of graphite added was set at 0.5 to 20% by volume is as follows.
If it is less than 0.5% by volume, no lubricating effect can be expected, and if it is added in excess of 20% by volume, no improvement in effectiveness can be expected, but on the other hand, as the amount added increases, the entire bearing body tends to become brittle. This is because it is inconvenient.

Sprayed kelmet powder or bronze powder is used as metal powder.

These metal powders contribute to lowering the coefficient of thermal expansion and improving the thermal conductivity of bearings, but they also impart metallic properties to the plastic surface, where lubricating oil usually has low ductility, making it easier to use lubricating oil on bearings. It aids in the formation and retention of an oil film on the sliding surface, and it is desirable that its amount be as large as possible, but the effect will be improved even if it is added in an amount exceeding 50% by volume. On the other hand, the structural structure of the bearing body tends to become rapidly brittle9 and molding becomes difficult, so it is optimal that the amount added is in the range of 0.5 to 50% by volume. Next, embodiments of the invention will be described.

Example 1 30% by volume of lubricating oil (product name: Daphne Super Mechanical Oil 100) and 6% by volume of norbornene-based synthetic elastomer (product name: NORSOREX)
12 at room temperature after mixing with a pen shell mixer.
Leave to stand for a period of time to obtain a homogeneously mixed slurry. To this, 10% by volume of scaly graphite, 15% by volume of atomized Kelmet powder, and 39% by volume of polyacetal resin powder are added. After mixing again with a pen shell mixer, extrusion molding is performed. to make pellets,
Using this, a bearing body of predetermined dimensions was molded by injection molding.

Example 2 A bearing was obtained in the same manner as in Example 1 except that bronze powder was used instead of the sprayed Kelmet powder as the metal powder shown in Example 1.

Example 3 Lubricating oil (product name: Daphne Super Mechanic Oil 1)
00) Add 4% by volume of norbornene-based synthetic elastomer (trade name: NORSOREX) to 20% by volume,
After mixing in a pen shell mixer, it was left at room temperature for 12 hours to obtain a homogeneously mixed slurry. To this, 20 volume % of scale graphite, 15 volume % of atomized Kelmet powder, and 41 volume % of polyacetal resin powder were added, and the mixture was mixed again. After mixing in a pen shell mixer, the pellets were formed by extrusion molding, and the pellets were used to mold a bearing body of a predetermined size by injection molding.

Example 4 A bearing body was molded in the same manner as in Example 3, except that the same amount of nylon 66 was used in place of the polyacetal resin in Example 3.

Example 5 To 10% by volume of lubricating oil (same as in Example 1), 2% by volume of norbornene-based synthetic elastomer (same as in Example 1 (1)) was added, mixed with a pen shell mixer, and then left at room temperature for 12 hours. , a uniformly mixed slurry was obtained, and scaly graphite 1 was added to it.
0% by volume and 15% by volume of bronze powder were added, mixed again in a pen shell mixer, and then extruded into pellets, which were then used to mold a bearing body of a predetermined size by injection molding.

Example 6 A bearing body was molded in the same manner as in Example 4, using polybutylene terephthalate instead of the nylon 66 resin used in Example 4.

Example 7 A bearing body was molded in the same manner as in Example 5, using polybutylene phthalate instead of the nylon 66 resin.

The bearing bodies molded in each of the above examples are all 8 mm.
It had dimensions of φ x 10 mm φ x 15 m T1L, and was used to receive an S45C unhardened shaft with a surface roughness of 3S, and friction and wear tests were conducted under the following test conditions.

Regarding the test conditions and test results, the comparative examples listed in the table above are as follows: (Comparative Example 1) is a mixture of polyacetal resin 95% by volume and lubricating oil (trade name: Daphne Super Mechanical Oil 100).
), and after mixing them, a bearing of a predetermined size was molded. (Comparative Example 2) was made by adding 5% by volume of the same lubricating oil as in Comparative Example 1, 20% by volume of graphite, and 60% by volume of polyacetal resin. (Comparative Example 3), in which 55 volume % of polyacetal resin and 1 1 of ethylene vinyl acetate copolymer (EVA) were mixed, and a bearing of a predetermined size was molded from this mixture.
0% by volume, 10% by volume of lubricating oil of the same type as Comparative Example 1, 1% by volume of graphite
(Comparative Example 4), in which nylon 66 resin was used in place of the polyacetal resin in Comparative Example 3, and a bearing was molded from this mixture by mixing 0% by volume and 15% by volume of bronze powder. A bearing body molded in the same manner as (Comparative Example 5)
) is a bearing body molded in the same manner as in Comparative Example 3 using polybutylene terephthalate resin instead of the polyacetal resin in Comparative Example 3. (Comparative Example 6) is a bearing body made of ethylene vinyl acetate copolymer (EVA) of Comparative Example 3. A bearing was molded in the same manner as in Comparative Example 3 using the same amount of butadiene rubber (BR) instead.

As is clear from the soil surface, if we compare samples made of the same synthetic resin, such as Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2, the performance is significantly superior. In addition, in this invention, the metal powder is uniformly dispersed within the main synthetic resin, and is also similarly dispersed on the surface, so that the metal powder originally prevents lubricating oil from becoming a lubricant. The lubricating oil's ductility is imparted to the synthetic resin, which has low ductility, and the lubricating oil film that oozes out is formed and maintained, thereby improving the sliding properties of the bearing.

As is clear from the above, the present invention exhibits superior sliding characteristics compared to conventional bearings, and therefore, for example,
Washing machine pulsators, etc. have a PV value of 800 to 1000 kg
/(It can also be applied to high load bearings such as 1-7 f-m/Min, increasing versatility.

Claims (1)

[Claims] 1 1 to 40% by volume of lubricating oil and 0 as the lubricating oil carrier
．． 1 to 20% by volume of norbornene-based synthetic elastomer, 0.5 to 20% by volume of graphite as a solid lubricant, and 0.5% to 20% by volume of graphite.
An oil-free bearing comprising 5 to 50% by volume of metal powder and the remaining volume% of synthetic resin.