Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-03-30
2001-05-15
Sanders, Kriellion (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S494000
Reexamination Certificate
active
06232385
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to resin parts for use in a mechanical transmission such as gears, friction wheels and cams and a method for manufacturing the same.
There are two types of transmissions, namely, mechanical type and fluid type. The former has such parts as gears, friction wheels and cams to convert the rotary or reciprocating motion of a shaft, crank or rod to a different motion.
It is desired that such parts be small, lightweight, less expensive, need no grease and consume less energy. To meet these requirements, such parts are often made from resins.
Among resins used for this purpose, resin materials known as super-engineering plastics, which are characterized by their high heat resistance, are especially desirable if the parts are used at high temperatures over 150° C. There are two types of super-engineering plastics, i.e. thermosetting type and thermoplastic type. The former type includes polyimide (PI for short) resin and phenolic (PF) resin. The latter type includes polyarylether ketone (PAEK) resin, thermoplastic polyimide (TPI) resin, and polyamideimide (PAI) resin.
Among such super-engineering plastics, thermoplastic resins are more suitable in mechanical strength at low temperature and injection moldability for mass-production. As the main material for resin parts for mechanical transmissions, TPI resin, which has a glass transition point (Tg) of about 250° C. and a heat resistance of 200° C. or over, is particularly desirable because of its high mechanical strength in a wide temperature range and good injection moldability and mass-productivity.
But machine parts made by injection molding TPI resin have some drawbacks. One is that its crystallinity is as low as 4% or under. Low crystallinity means low wear resistance. Thus, such machine parts are not durable enough and poor in dimensional stability at high temperatures for use in mechanical transmissions.
When two of such TPI resin parts are brought into rolling, sliding or any other type of frictional contact with each other in a mechanical transmission, low wear resistance results from high cohesiveness. Thus, they tend to wear much more quickly than when a TPI resin part and a metal part are brought into frictional contact with each other under the same conditions.
An object of the invention is to provide machine parts which are made from TPI resin and can be used in a wide temperature range from lower than normal temperature to high temperature over 200° C. and are still high in wear resistance and durability.
Another object of the invention is to provide machine parts that show high cohesive wear resistance and durability when they are brought into rolling, sliding or any other type of frictional contact with each other in a mechanical transmission.
SUMMARY OF THE INVENTION
According to the invention, there is provided a resin part for use in a mechanical transmission, said resin part being formed from a resin composition comprising 100 parts by weight of thermoplastic polyimide resin, and 10-100 parts by weight of a reinforcing material, said thermoplastic polyimide resin having a crystallinity of 10% or over.
As the reinforcing material, fibrous material such as carbon fiber or glass fiber or whisker is preferable. The part may be a gear, friction wheel or cam.
From another aspect of the invention, there is provided a method of manufacturing a resin part comprising injection-molding a resin composition comprising 100 parts by weight of thermoplastic polyimide resin and 10-100 parts by weight of a reinforcing material, and heating the injection molding thus formed to adjust the crystallinity of the thermoplastic polyimide resin to 10% or over.
The heating is preferably conducted at a temperature of 220-340° C. for 5-24 hours.
The resin parts thus formed according to the present invention show high wear resistance and long life.
Crystallinity of the thermoplastic polyimide resin is reliably adjustable to 10% or over by the method according to the present invention.
Gears, friction wheels and cams thus formed show improved wear resistance and high durability (long life) even if used under high-load conditions such as under large torque.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The thermoplastic polyimide resin used in this invention may be a polymer having repeating units shown in Formula 1 or 3. An additional resin may be mixed into the thermoplastic polyimide resin in such an amount that the target crystallinity of the polyimide resin is achievable.
(In the formula 1, X denotes direct coupling, —SO
2
—, —CO—, —C(CH
3
)
2
—, —C(CF
3
)
2
— or —S—. R
1
, R
2
, R
3
and R
4
is hydrogen, alkyl group, alkoxy group, halogenated alkyl group, halogenated alkoxy group or halogen group. Y is one or more group selected from the group consisting of the following formula:
(In the formula 3, R
5
and R
6
are hydrogen, alkyl group, halogenated alkyl group, halogenated alkoxy group or halogen group. n is an integer (1, 2, 3 or 4). Y is as defined above in relation to formula 1.)
Such an additional resin may be a resin formed by a polymer having the following repeating units: polyphenylene sulfide (PPS) resin having a repeating unit shown in Formula 4 as polymer components; polyether nitride (PEN) resin having a repeating unit shown in Formula 5; polyaryletherketone (PAEK) resin having a repeating unit shown in Formulas 6-9. Among the PAEK resins, especially preferable ones are polyetherketone (PEK) resin having a repeating unit shown in Formula 6; polyetheretherketone (PEEK) resin having the repeating unit shown in Formula 7; and polyetherketoneetherketone (PEKEKK) resin having the repeating unit shown in formula 8.
The reinforcing material used in the present invention may be carbon fiber, glass fiber, whisker or any other fibrous filling material, or flaky or powdery inorganic reinforcing material, or their mixture.
Specific fibrous reinforcing materials usable in this invention are carbon fibers such as PAN carbon fibers and pitch carbon fibers, milled fiber, glass fiber, potassium titanate fiber, boron fiber, silicon carbide fiber, metallic fibers formed of copper, aluminum or zinc fiber, other inorganic fibers, organic fibers such as aromatic polyamide fibers, and whiskers.
Specific whiskers include silicon carbide whisker, silicon nitride whisker, potassium titanate whisker, aluminum borate whisker, zinc oxide whisker, magnesium sulphate whisker, magnesia whisker, magnesium borate whisker, titanium diborate whisker, calcium carbonate whisker, graphite whisker, bismuth whiskers, magnesium oxide whisker, aluminum nitride whisker and ceramics whiskers such as mullite and magnesium pyroborate.
Specific inorganics include glass beads, wollastonite, talc, kaolin, silicon dioxide, clay, asbestos, calcium carbonate, magnesium hydroxide, silica, diatomaceous earth, carborundum in powdery or granular form, and flakes such as mica, aluminum foil and zinc foil.
The reinforcing material is treated with an epoxy or amino group silane coupling agent to improve affinity with the resin and its dispersibility.
Among these reinforcing materials, carbon fiber, glass fiber and whisker are especially preferable.
The reinforcing material should be added at the rate of 10-100 parts by weight, preferably 20-70 parts by weight to 100 parts by weight of the resin. If the rate is lower than this range, the resin parts formed tend to be deformed or broken during use in a mechanical transmission due to insufficient mechanical strength. If the rate is higher than the above range, flowability of resin during molding tends to be very poor and also the molded parts formed tend to be brittle due to shortage of the resin content, resulting in deformation or breakage. Also, depending upon the kind of reinforcing material, the mating resin member in the transmission may be worn severely.
Provided that the effect of the invention is not unduly affected, various additives may be incorporated into the thermoplastic polyimide resin, the main component. Such additives include solid lubricants such as polyte
Egami Masaki
Kataoka Mari
Shimazu Eiichiro
NTN Corporation
Sanders Kriellion
Wenderoth , Lind & Ponack, L.L.P.
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