JPS5924284B2 - 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 is limited to bearings that are operated under light loads, such as bearings in the driving parts of toys or sliders in the sliding parts of furniture drawers, where the PV value is 9/(- 77f-771/m
It has the disadvantage that it is limited to those with an upper limit of m, and is not suitable for use with higher loads.

For this reason, we improved the friction resistance and wear characteristics of the above synthetic resin,
In order to make the resin more resistant to high-load operation, lubricating oil is mixed into the resin, for example, as disclosed in Japanese Patent Application Laid-Open No. 48-22133, Adding a resin that absorbs lubricating oil, or mixing a rubbery substance that absorbs lubricating oil as seen in Japanese Patent Publication No. 49-4816, and allowing these mixed substances to absorb lubricating oil. As an oil-bearing substance,
Rather than the above-mentioned polymer compounds,
As seen in No. 71, it has been proposed to use graphite, but in the case of the former two types of 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.
Therefore, it is difficult to leach out the lubricating oil to an extent that can contribute to improving the sliding properties.Also, even if the polymer compound or graphite absorbs and supports the lubricating oil, the amount of absorption is limited. There is a limit to the amount of lubricating oil, usually 1 volume of lubricating oil absorbent, and about 3 volumes of lubricating oil.For this reason, if you want the resin to contain a large amount of lubricating oil, a large amount of lubricating oil absorbent is naturally required. Therefore, it had the disadvantage of impairing the physical properties of the base resin and reducing the mechanical strength required for bearings.

Therefore, the larger the amount of lubricant mixed in, the better. However, due to the above, it is necessary to satisfy the absorption amount within a certain limit. Therefore, the applicable range of these bearings is limited to office equipment. PV value is 400kg/d・m/M, such as roller bearings of the same type.
The problem was that it could not be applied to applications with even higher loads.

However, oil-free bearings are desired to be applied to equipment with higher loads than to save labor on maintenance of operating equipment, and conventional bearings have the drawback of not being able to fully meet these demands. Ta.

Furthermore, the absorbents that function as lubricating oil carriers themselves have poor lubricity, so if they are exposed on the sliding surface, they are forced to come into contact with the receiving shaft (rotating shaft), which makes them less effective as bearings. There was a drawback that even friction properties and low wear properties could be impaired. In view of the above-mentioned drawbacks, the present inventors conducted intensive research and tests with the aim of 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 elastomer is used as a carrier material that can support a sufficient amount of lubricating oil without impairing the strength of the entire bearing.
and expanded graphite were found to be most suitable, and based on this knowledge, the present invention was accomplished. That is, the gist of the present invention is to provide an oil-free bearing with lubricating oils 1 to 4.
0% by volume, norbornene-based synthetic elastomer and expanded graphite as carriers for the lubricating oil, respectively 0.1 to 20% by volume,
0.5 to 20% by volume, and the remaining volume is 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 porous pores that adsorb various liquid components. Refers to graphite that exhibits characteristics. In addition, the synthetic resins that account for the remaining volume percent include the aforementioned polyacetal,
It refers to so-called engineering plastics, such as polyamide and polybutylene terephthalate, which have excellent self-lubricating properties and low abrasion properties.

Next, this invention will be explained in more detail.

Lubricating oils used in carrying out this invention include aromatic lubricating oils such as spindle oil, turbine oil, machine oil, and dynamo oil, naphthenic lubricating oils, paraffinic lubricating oils, and hydrocarbon, ester, and polyester oils. Any commonly used lubricating oil such as synthetic oil such as glycol or silicone may be used. Further, 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. Lubricating oil reaches up to 10 volumes. Moreover, the temperature dependence of this absorption capacity is
As the temperature increases, the amount of absorption increases. Therefore, even when exposed to high temperatures during machining, the lubricating oil remains trapped, preventing screw slip due to lubricating oil seepage.
It has a characteristic that when the temperature of the product after processing falls to room temperature, lubricating oil oozes out due to a decrease in absorption capacity.

Therefore, if the entire constituent assembly of an oleoresin bearing is 100% by volume, the amount of norbornene synthetic elastomer can be sufficiently supported by 0.1 to 20% by volume of lubricating oil to 1 to 40% by volume. be.

Expanded graphite can be obtained by mixing artificial graphite, natural graphite, mainly natural scaly graphite with concentrated sulfuric acid, concentrated nitric acid mixture, potassium chlorate,
When used in combination with strong oxidizing agents such as potassium dichromate,
After wet oxidation treatment, this product was heated to 200 to 1000
The material is heated to 0.degree. C. and expanded 50 to 300 times in the C-axis direction to form a porous structure capable of adsorbing lubricating oil, which then absorbs lubricating oil.

This lubricating oil absorption capacity is approximately equivalent to that of a norbornene-based synthetic elastomer.

Therefore, the lubricating oil is carried by both the norbornene-based synthetic elastomer and expanded graphite.

The reason for limiting the volume percent of the lubricating oil to 1 to 40 volume percent is that if it is less than 1 volume percent, sufficient lubricity cannot be obtained;
This is because if the amount exceeds 0% by volume, the amount of lubricating oil relative to the resin bearing increases too much, the lubricating oil leaks out significantly, and carrying the lubricating oil becomes meaningless. As for the formulation for absorbing the above lubricating oil, the total amount of lubricating oil required may be divided and supported by the norbornene-based synthetic elastomer and the expanded graphite 2, but only the norbornene-based synthetic elastomer absorbs the lubricating oil. It may be configured such that the entire amount of lubricating oil is supported and the expanded graphite is not supported with lubricating oil.

That is, since expanded graphite itself has lubricity as a general function of graphite, expanded graphite itself may be used as a lubricant.

In addition, when the expanded graphite is not loaded with lubricating oil,
Instead of expanded graphite, normal graphite, artificial graphite, natural graphite itself, or a mixture of expanded graphite and the above-mentioned normal graphite may be used.

Next, embodiments of the invention will be described.

(Example 1) 8% by volume of norbornene-based synthetic elastomer (product name: NORSOREX) and 30% by volume of expanded graphite
20% by volume of lubricating oil (trade name: Daphne Super Mechanical Oil 100) was added to each 8% by volume of the material that was heat-treated at 0°C and expanded in the C-axis direction to become porous with lubricating oil adsorption. After mixing with a mixer, mix at room temperature for 1
Leave to stand for 2 hours to obtain a slurry mixture of lubricating oil and lubricating oil carrier. To this mixture, 64% by volume of polyacetal resin powder (trade name: Zyuracon M9O-02) as a synthetic resin was added, and mixed again with a mixer. Mixed.

The obtained mixed powder was made into pellets by extrusion molding, and then a bearing body of a predetermined size was molded by injection molding. (Example
2) Norbornene-based synthetic elastomer (product name: NORSO
REX) 30% by volume of lubricating oil (trade name: Daphne Super Mechanical Oil 100) was added to 10 volumes, mixed with a mixer, and left at room temperature for 12 hours to uniformly mix the lubricating oil and lubricating oil carrier. Obtain a slurry and add 8 to this mixture.
% by volume of expanded graphite and 52 % by volume of polyacetal resin powder (trade name: DURACON M9O-02) were added and mixed again with a mixer.

The obtained mixed powder was made into pellets by extrusion molding, and then a bearing body of a predetermined size was molded by injection molding. (Example
3) Nylon 6 instead of polyacetal resin in Example 1
6, a bearing body was molded in the same manner as in Example 1.

(Example 4) A bearing body was molded in the same manner as in Example 1, using polybutylene terephthalate instead of the polyacetal resin in Example 1.

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

The bearing bodies molded in Examples 1 and 2 above both have a diameter of 8 mmφXlOm77! φ×15m77! A shaft of S45C with no hardening and a surface roughness of 3S was received on this shaft, and friction and wear tests were conducted under the following test conditions.

Test conditions The comparative examples in the above table are conventional examples, and (Comparative example 1) is a mixture of 95 volume % polyacetal resin and lubricating oil (
Product name: 5% by volume of Daphne Super Mechanical Oil 100) was added and mixed, and then a bearing of the specified dimensions was formed. (Comparative Example 2) is the same lubricating oil as Comparative Example 1, 20% by volume. Ethylene vinyl acetate copolymer (EVA)
Mix 20% by volume and 60% by volume of polyacetal resin,
A bearing of a predetermined size was molded from this mixture. (Comparative Example 3) was a bearing molded using the same amount of nylon 66 in place of the polyacetal resin of Comparative Example 2. (Comparative Example 4) was a bearing of a predetermined size. Ethylene vinyl acetate copolymer (EV
(Comparative Example 5) is a bearing molded using the same amount of butadiene rubber (BR) instead of A), and (Comparative Example 5) is a bearing molded using the same amount of polybutylene terephthalate instead of the polyacetal resin of Comparative Example 2. , (Comparative Example 6) is Comparative Example 2
The bearing is molded using the same amount of polycarbonate instead of polyacetal resin.

As is clear from the table above, Example 1, Comparative Example 1, and Example 2
If we compare the same main synthetic resins, such as Comparative Example 2 and Comparative Example 3, Example 3 and Comparative Example 3,
It can be seen that the performance of the present invention in terms of wear resistance and friction resistance is significantly superior.

As is clear from the above, the oil-free bearing of the present invention has excellent wear resistance and friction resistance properties compared to conventional bearings, and therefore has a P value of 800 to 1000k9, for example in the pulsator of a washing machine.
/CTil-m/Mm and other high-load bearings.
It has increased versatility and also has excellent dimensional stability because the temperature rise is small due to its wear resistance and friction properties. Furthermore, since the norbornene-based synthetic elastomer and expanded graphite used as the lubricating oil carrier in this invention have sufficient lubricating oil absorption ability even if the total amount of each is 20% by volume or less, a large amount of activated carbon, synthetic rubber, etc. Since there is no need to mix the base resin, there is less deterioration in the physical properties of the base resin.
It can also have excellent mechanical strength.

Claims (1)

[Claims] 1 1 to 40% by volume of lubricating oil, 0.0% by volume of norbornene synthetic elastomer as a carrier for the lubricating oil, and 0.0% by volume of expanded graphite, respectively.
An oil-free bearing characterized in that 1 to 20% by volume, 0.5 to 20% by volume, and the remaining volume are made of synthetic resin.