JPS5924285B2 - Oil-free bearing - Google Patents

Description

[Detailed description of the invention] The present 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, they do not require lubrication and can be very useful. 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 above synthetic resin and make it able to withstand higher load operation, lubricating oil is mixed into the above synthetic resin. Kaisho 48-221
As disclosed in Japanese Patent Publication No. 33, a resin that absorbs lubricating oil is mixed in, or as in Japanese Patent Publication No. 49-4816, a rubbery substance that absorbs lubricating oil is mixed,
To make these contaminants absorb the lubricating oil, or to use the above-mentioned lubricating oil carrier instead of a polymer compound,
As seen in Publication No. 37571, it has been proposed to use graphite, but in the case of the former two polymer compounds that absorb lubricating oil, the lubricating oil absorption effect is due to the interaction between the three-dimensional molecular structure of the polymer compound. This is due to the so-called swelling phenomenon in which the lubricant is absorbed by the lubricant.Once absorbed, the lubricant is difficult to leach out, and therefore it is difficult to leach out the lubricant to the extent that it can contribute to improving the sliding properties. In addition, even if the polymer compound or graphite absorbs and supports lubricating oil, there is a limit to the amount of absorption; usually, the amount of lubricating oil is about 3 volumes per 1 volume of lubricating oil absorbent. When it is desired to contain a large amount of lubricating oil in the resin, 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.

Furthermore, since the above-mentioned synthetic resin has a large thermal expansion coefficient, when heat is generated during use as a bearing, there is a drawback that expansion deformation is significant and uneven wear of the bearing portion occurs.

Therefore, in the case of conventional synthetic resin bearings, the PV value is 400k, such as roller bearings of office equipment and sliding parts of drawers.
gZd·m/Min is the limit, and there is nothing that can withstand even higher loads.

In view of the above drawbacks, the present invention aims to obtain a constituent material of an oil-free bearing that can absorb a large amount of lubricating oil without impairing the physical properties of the base resin, and a constituent material that can minimize the effects of heat on the bearing. As a result of intensive research and testing by the inventors, the lubricating oil. As a carrier, norbornene-based synthetic elastomer and expanded graphite were heated at 200°C to 1000°C.
Porous graphite obtained by heat-treating and expanding in the C-axis direction is most suitable, and atomized Kelmet powder or bronze powder is most suitable as a material that provides stability against heat. It was discovered that metal powder imparts ductility to the surface of a synthetic resin, which originally has low oil ductility, and based on this knowledge, the present invention was accomplished.

That is, the oil-free bearing of the present invention contains 1 to 40% by volume of lubricating oil, a norbornene-based synthetic elastomer as the lubricating oil carrier,
Expanded graphite is heat-treated at 200°C to 10,000°C and expanded in the C-axis direction.
1 to 20% by volume, 0.5 to 20% by volume, 0.5 to 50% by volume of sprayed kelmet powder or bronze powder, and the remaining volume made up of synthetic resin.

In the above, expanded graphite refers to an intercalation compound obtained by oxidizing natural graphite with a high degree of crystallinity using an oxidizing agent.It expands irreversibly when heated and has a porous structure that absorbs various liquid components. Refers to graphite that exhibits

The synthetic resin occupying the remaining volume means so-called engineering plastics having excellent self-lubricating properties and low abrasion properties, such as polyacetal, polyamide, polybutylene terephthalate, polycarbonate, and polytetrafluoroethylene.

Next, this invention will be explained in more detail. The lubricating oils used in this invention include aromatic lubricating oils such as spindle oil, turbine oil, machine oil, and dynamo oil, naphthenic lubricating oils, paraffinic lubricating oils, or hydrocarbon, ester, polyglycol, and silicone oils. Any commonly used lubricating oil may be used, such as synthetic oil. The reason why the amount of lubricating oil is set to 1 to 40% by volume is that if it is less than 1% by volume, the amount of lubricating oil is too small and the effect of the lubricating oil cannot be obtained, and if it exceeds 40% by volume, it will be described later. This is because adding lubricating oil becomes wasteful for some reason.

As the norbornene-based synthetic elastomer as a lubricating oil carrier, a norbornene-based resin or a vulcanized mixture of a norbornene-based resin is used.

This norbornene-based synthetic elastomer is in the form of powder particles and has an extremely porous structure, so it can absorb a large amount of lubricating oil, and this absorption capacity is per volume of norbornene-based synthetic elastomer. The lubricating oil can reach up to 10 volumes.

Furthermore, this absorption capacity is temperature dependent, and the absorption amount increases as the temperature increases. Therefore, even when exposed to high temperatures during machining, the lubricating oil remains trapped, resulting in screw damage due to lubricating oil seepage. It has characteristics such as being able to prevent slips and causing lubricating oil to ooze out due to a decrease in absorption capacity when the temperature of the product after processing falls to room temperature.

Therefore, in order to absorb 1 to 40% by volume of lubricating oil,
0.1-20% by volume of norbornene-based synthetic elastomer
It is sufficient.

In addition, expanded graphite, which functions as another lubricant carrier,
It expands in the C-axis direction by heat treatment at 200°C to 1000°C to form a porous structure with lubricating oil adsorption ability, and then absorbs lubricating oil. They have almost the same absorption capacity.

On the other hand, since the expanded graphite described above also has lubricity as a general function of graphite, it may be configured such that the entire amount of lubricating oil is contained in the norbornene-based synthetic elastomer without having the expanded graphite carry the lubricating oil.

The lubricant can be contained in each lubricant by dividing the total amount of lubricant as appropriate, but even if the amount of lubricant is increased, the lubricant will decrease as the temperature rises. As a result, lubricating oil can only be stably supported within the above-mentioned range.

Sprayed Kelmet powder or bronze powder is added to reduce the coefficient of thermal expansion and improve thermal conductivity of bearings, as well as to impart lubrication oil ductility to the synthetic resin surface. It is desirable to add as much as possible, but if more than 50 (f) is added in terms of volume %, the effect of adding soil cannot be expected to be that great, and the structure of the bearing body tends to become brittle, making molding difficult. Therefore, the addition amount is set within 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)
and 6% by volume of expanded graphite heat-treated at 300°C and expanded in the C-axis direction to make it porous, mixed with a pen shell mixer, and left at room temperature for 12 hours.
A homogeneously mixed slurry was obtained, and 20% by volume of Kelmet powder (Pb3O%) was sprayed as a metal powder, and polyacetal resin powder (trade name: DURACON M9) was sprayed as a synthetic resin.
After adding 38% by volume of O-02) and mixing again with a pen shell mixer, pellets were formed by extrusion molding, and the pellets were used to mold a bearing body of a predetermined size by injection molding.

Example 2 Lubricating oil (product name: Daphne Super Mechanical Oil 1)
00) Adding 5% 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, which was mixed with 7% by volume of expanded graphite, 20% by volume of Kelmet powder (Pb3O%) sprayed as metal powder, and synthetic resin. Then, 48% by volume of polyacetal resin powder (trade name: Diyuracon M9O-02) was added, and a bearing body of predetermined dimensions was molded in the same manner as in Example 1.

Example 3 A bearing body was molded in the same manner as in Example 1 except that the same amount of nylon 66 resin was used in place of the polyacetal resin in Example 1.

Example 4 A bearing body was molded in the same manner as in Example 1 using the same amount of polybutylene phthalate resin instead of the polyacetal resin in Example 1.

Example 5 A bearing body was molded in the same manner as in Example 1, using the same amount of polycarbonate resin instead of the polyacetal resin used in Example 1.

The bearing bodies molded in Examples 1 to 5 above all had dimensions of 8m71Lφ x 10mmφ x 15mm, and were made to receive S45C unquenched shafts with a surface roughness of 3S, and under the following test conditions. Friction and wear tests were conducted with

Test conditions Test results In Comparative Example 2, 5% by volume of oil (trade name: Daphne Super Mechanical Oil 100) was added and mixed to form a bearing of a predetermined size. Lubricating oil 5% by volume and Kelmet powder 20%
In Comparative Example 3, 60% by volume of polyacetal resin, 5% by volume of the same lubricating oil as in Comparative Example 1, and 5% by volume of the same lubricating oil as in Comparative Example 1 were added as a lubricating oil carrier to 60% by volume of polyacetal resin. Ethylene vinyl acetate copolymer (EVA) 20
In Comparative Example 4, the polyacetal resin used in Comparative Example 3 was added to 40% by volume, and Kelmet powder was added in proportion to the amount of the reduced amount. In Comparative Example 5, the same amount of butadiene rubber (BR) was added in place of the ethylene-vinyl acetate copolymer in Comparative Example 3. In Comparative Example 6, the same amount of nylon 66 resin was used instead of the polyacetal resin used in Comparative Example 4, and the bearing was molded in the same manner as Comparative Example 4. Example 8 is similar to Comparative Example 4.
In Comparative Example 8, the same amount of polycarbonate resin was used instead of the polyacetal resin in Comparative Example 4, and the same amount of polybutylene phthalate resin was used instead of the polyacetal resin in Comparative Example 4. Similar to 4, the bearing is molded.

As is clear from the table above, when comparing samples made of the same main synthetic resin, such as Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2, the performance is significantly superior. I understand that.

In addition, in the present invention, the metal powder is uniformly mixed in the main synthetic resin and is evenly dispersed on the surface. The spreadability of the lubricating oil is obtained, and the form and retention of the oil film are achieved.

Therefore, the dimensional stability due to the metal powder mixture and the sliding properties are also good, and from these, the PV value is 800 to 100.
0kgZ?・It can be used for high-load applications such as washing machine pulsators, significantly expanding the versatility of oil-free resin bearings. Furthermore, since the norbornene-based synthetic elastomer and expanded graphite used in this invention both have sufficient lubricating oil absorption ability, their addition can be extremely small relative to the amount of oil required, and It becomes possible to increase the amount of other constituent materials added, and the physical properties of the bearing as a whole can be significantly improved.

Claims (1)

[Claims] 1 Lubricating oil 1 to 40% by volume, norbornene-based synthetic elastomer as the lubricating oil carrier, and expanded graphite 200 to 10% by volume.
Porous graphite obtained by heat treatment at 00°C and expansion in the C-axis direction was 0.1 to 20% by volume, and 0.5 to 20% by volume, respectively.
20% by volume, sprayed kelmet powder or bronze powder from 0.5 to 5
An oil-free bearing characterized in that the remaining volume is made of synthetic resin.