JP7316400B1 - Oil seal for forward/reverse rotation - Google Patents

Abstract

[Solution] A vulcanized molded product containing 10 to 50 parts by weight of a filler having an average particle diameter of 0.2 to 4.0 µm per 100 parts by weight of rubber has an arithmetic mean height of cross-sectional roughness of 0.1 to 1.0 µm Sa. rubber molding. This rubber molding contains a filler with an average particle diameter of 0.2 to 4.0 μm, and selects a vulcanized molded product with an arithmetic mean height of cross-sectional roughness of 0.1 to 1.0 μmSa. By reducing the oil film thickness on the seal sliding surface of a reverse rotating oil seal or the like, there is an excellent effect of suppressing the biting of metal foreign matter into the sliding surface of the seal and the shaft. Therefore, it is suitably used as a seal material for oil seals and the like. [Selection figure] None

Description

The present invention relates to a forward/reverse rotating oil seal .

Oil seals are widely used as important mechanical parts in the fields of automobiles, industrial machinery, and the like. Among them, the bi-rotating oil seal, which aims to keep the fluid sealed even in both forward and reverse rotation of various parts, is used as a component part for pumps, automobile differentials, agricultural machinery, railway vehicles, etc. Used in a wide range of fields.

Conventionally used oil seals may leak sealed fluid when a member in contact with the oil seal is rotated forward and then reversed.

The present applicant has previously proposed that 100 wt. A fluororubber composition prepared by adding 1 to 100 parts by weight of wollastonite having an aspect ratio of 8 or more per part and kneading it is vulcanized and molded to form a sliding surface for railway vehicles. We have proposed an oil seal for both forward and reverse rotation (Patent Document 1).

In addition, in Patent Document 2, as a molding material for an oil seal that is excellent in durability such as heat resistance and wear resistance, and which can sufficiently satisfy lubricating oil resistance and sealing performance, an average of 100 parts by weight of fluororubber A fluororubber composition containing 3 to 60 parts by weight of at least one of diatomaceous earth, wollastonite, talc, graphite and carbon fiber having a particle size of 6 to 35 μm has been proposed.

However, in the market, the sliding surface of the shaft may be damaged by metal foreign matter contained in the oil in the forward/reverse rotation oil seal, and in this case, the shaft must be replaced. In order to avoid such a phenomenon, it is desirable to suppress damage to the shaft and extend the service life of the shaft.

Here, from the results of analysis of collected products from the market, it was found that the cause of damage to the shaft is that metallic foreign matter contained in the oil intervenes between the sliding surface of the lip and the shaft. , is presumed to cause shaft damage.

Japanese Patent Application Laid-Open No. 2008-64201 Patent No. 6,435,666

SUMMARY OF THE INVENTION It is an object of the present invention to provide a forward/reverse rotation oil seal capable of suppressing the biting of metallic foreign matter.

Specifically, the present invention
1. 10 to 50 parts by weight of a filler of diatomaceous earth or polytetrafluoroethylene resin having an average particle diameter of 0.2 to 4.0 μm per 100 parts by weight of fluororubber, and the arithmetic mean height Sa of the cross-sectional roughness of the vulcanized molded product is Oil seal for both forward and reverse rotation with a thickness of 0.1 to 1.0 μm and a maximum height Sz of 10 to 20 μm.

The oil seal for both forward and reverse rotation according to the present invention contains a filler that is diatomaceous earth or polytetrafluoroethylene resin with an average particle size of 0.2 to 4.0 μm, and the arithmetic mean height of the cross-sectional roughness of the vulcanized molding is 0.1 to 1.0 μm in thickness Sa and 10 to 20 μm in maximum height Sz. This provides an excellent effect of suppressing the biting of metallic foreign matter into the sliding surface of the shaft.

The oil seal for both normal and reverse rotation of the present invention contains a filler made of diatomaceous earth or polytetrafluoroethylene resin having an average particle size of 0.2 to 4.0 μm per 100 parts by weight of rubber, and the arithmetic mean of cross-sectional roughness The height Sa is 0.1-1.0 μm, and the maximum height Sz is 10-20 μm.

Examples of the rubber include fluororubber, nitrile rubber, acrylic rubber, and the like, and fluororubber is used from the viewpoint of being excellent in heat resistance, oil resistance, and the like.

As the fluororubber, vinylidene fluoride or tetrafluoroethylene and other fluorine-containing olefins or copolymer rubbers of olefins are used. Vinylidene-hexafluoropropylene-tetrafluoroethylene terpolymer, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-perfluoro(methyl vinyl ether) copolymer, vinylidene fluoride-tetrafluoroethylene Ethylene-perfluoro(methyl vinyl ether) terpolymer, Tetrafluoroethylene-propylene copolymer, Tetrafluoroethylene-perfluoro(methyl vinyl ether) copolymer, Tetrafluoroethylene-perfluoro(methyl vinyl ether)-ethylene 3 bromine- and/or iodine-containing compounds, nitrile groups, glycidyl groups, hydroxyalkyl groups, perfluorophenyl groups, and other crosslinkable groups are introduced into these various copolymerized fluororubbers. can also be used.

The fluororubber contains a filler of diatomaceous earth or polytetrafluoroethylene resin having an average particle size (measured by a laser diffraction scattering method) of 0.2 to 4.0 μm in an amount of 10 to 50 parts by weight, preferably It is blended at a ratio of 10 to 40 parts by weight.

It is thought that the more rough the rubber, the thicker the oil film on the sliding surface, and the more likely foreign matter in the oil will get caught in the sliding surface between the seal material and the shaft. Therefore, if a filler with a larger average particle size is used, foreign matter present in the oil will intervene in the sliding surface between the lip and the shaft in the forward/reverse rotation seal, and the shaft will be damaged due to the foreign matter getting caught. damage will occur.

On the other hand, when a filler having an average particle diameter smaller than this is used, the vulcanized molding cannot be provided with the arithmetic mean height Sa of cross-sectional roughness aimed at by the present invention, resulting in poor sealing performance. I'm going to be able to do it. Here, when the filler is fibrous, the average particle size means the average fiber length.

In addition, if the filler is used in a proportion smaller than this, the vulcanized molding cannot be given the arithmetic mean height Sa of cross-sectional roughness that is the object of the present invention, and the sealing performance is deteriorated. On the other hand, if it is used in a proportion higher than this, it tends to become sandy during kneading, making kneading impossible.

As the filler, diatomaceous earth and polytetrafluoroethylene [PTFE] resin are used .

To the rubber composition consisting of the above essential components, various compounding agents required from vulcanization operation, physical properties, functions, etc. are added. Vulcanizing agents, vulcanizing aids such as quaternary onium salts, phosphate vulcanization accelerators, polyfunctional unsaturated compound co-crosslinking agents, reinforcing agents such as carbon black, divalent metal oxides or hydroxides , an acid acceptor such as hydrotalcite, and other necessary compounding agents are blended, and then the composition is prepared by any kneading means using an open roll, a kneader, etc. Primary vulcanization by heat press for 3 to 30 minutes and, if necessary, secondary vulcanization at about 150 to 250°C for about 0.5 to 24 hours are vulcanized and molded into sealing materials such as oil seals. .

The obtained vulcanized molding is selected to have an arithmetic mean height Sa of cross-sectional roughness of about 0.1 to 1.0 μm. Also, the maximum height Sz of the cross-sectional roughness is about 10 to 20 μm.

The invention will now be described with reference to examples.

Example 1
VdF-HFP copolymer (DuPont product Viton A500) 100 parts by weight Carbon black (CANCARB product THERMAX N990 LSR) 2 Same as above
Diatomaceous earth (Chuo Silica Product Oplite W3005K; 20 〃
Average particle size 2.7μm)
Magnesium oxide (Kyowa Chemical Industry product Star Mag CX-150) 5 〃
Calcium hydroxide (OHMI CHEMICAL INDUSTRIES CALDIC#1000) 5 〃
Bisphenol AF 50 wt% fluororubber diluted product 2.3 Same as above
(Unimatec product CHEMINOX AF-50)
35 wt% phosphate-based vulcanization accelerator diluted product (company product B-35F) 1 Same as above
The above components are kneaded using a closed kneader and an open roll, and then press-cured at 180°C for 4 minutes and oven-cured at 200°C for 15 hours (secondary curing) using a 2RT-35t press. Vulcanization) was performed to vulcanize and mold a test piece for roughness measurement with a thickness of 2 mm and an oil seal.

Example 2
In Example 1, the amount of carbon black was changed to 13.5 parts by weight, and the amount of diatomaceous earth was changed to 14.1 parts by weight.

Example 3
In Example 1, the amount of carbon black was changed to 18 parts by weight, and the same amount (20 parts by weight) of PTFE resin (AGC product FLUON PTFE L-172JE; average particle size 0.24 μm) was used instead of diatomaceous earth. .

Example 4
In Example 3, the amount of carbon black was changed to 30 parts by weight.

Comparative example 1
In Example 1, the same amount (20 parts by weight) of Chuo Kasei Product SILIKA #6B (average particle size: 12.6 μm) was used as diatomaceous earth.

Comparative example 2
In Example 1, no diatomaceous earth was used.

Comparative example 3
In Example 1, the same amount (20 parts by weight) of carbon beads (Marilyn GC-025 manufactured by Gun Ei Chemical Industry Co., Ltd.; average particle size 25 μm) was used instead of diatomaceous earth.

Comparative example 4
In Comparative Example 1, the amount of diatomaceous earth was changed to 70 parts by weight.

Roughness measurement was performed using the test pieces obtained in each of the above examples and comparative examples, and shaft durability and sealing properties were evaluated using oil seals.
Female cut surface roughness: JIS B0601, ISO 4287 compliant,
Cutoff; λs 2.5μm, λc 0.8mm
A vulcanized molded product of a rubber composition is cut using a slicer or the like, and the
Arithmetic flattening of a smooth cross-section was observed by a non-contact method using a laser microscope.
The uniform height was calculated and the maximum height was measured. Shaft durability test: The oil seal was set in a rotation tester, and alumina with a grain size of 2.0 μm
Assuming metal foreign matter in the recovered oil) The state where the contained turbine oil is centered on the rotating shaft
under the conditions of test oil temperature of 120°C and rotation speed of 1500 rpm, forward rotation 1 hour
120 hours of operation with a 5-minute pause and a 5-minute rest period as one cycle.
Measure wear depth
If the wear depth of the shaft is less than 20 μm, it is evaluated as ○, and if it is 20 μm or more, it is evaluated as ×.
Sealed in the state, test oil temperature 100 ° C, rotation speed 2000 rpm, reverse rotation 15
After running for a minute, remove the oil from the lip of the oil seal with a syringe.
After pouring a certain amount of oil, measure the amount of oil sent to the oil side, and continue to run in the forward direction for 15 minutes.
Measure the amount of oil fed in after operation
The sealability was evaluated by calculating the K value using the following formula.
Q=KUD2G1 ^{/ 2}
Q: fluid feed rate per unit time, U: shaft peripheral speed,
D: shaft diameter, G: dimensionless characteristic number (= μub/Pr, μ: fluid viscosity, u: shaft peripheral speed,
b: contact width of seal, Pr: strain force)
Those with a K value of 1.0×10 ^-5 or more are 〇, those with a K value of 0.5×10 ^-5 or more and less than 1.0×10 ^-5
was evaluated as △, and less than 0.5×10 ^-5 as ×.

The results obtained in each of the above examples and comparative examples are shown in the following table.
table
Practical example Comparative example
Measurement/evaluation items 1 2 3 4 1 2 3 4
[Method cut surface roughness]
Arithmetic mean height (μm Sa) 0.79 0.53 0.68 0.55 1.16 － 2.70 －
Maximum height (μm Sz) 17.6 16.7 13.6 15.2 21.7 － 45.7 －
[Axis durability]
Shaft wear depth evaluation ○ ○ ○ ○ × － × －
[Sealability]
Pump volume measurement △ ○ ○ ○ 〇 × 〇 －

From the above results, the following can be said.
(1) In each embodiment, by using a fine filler and reducing the roughness of the material surface, it is difficult for foreign matter to get caught in the sliding surface of the lip seal, and the durability of the shaft is improved.
(2) When the average particle size of the filler is large, foreign matter tends to be caught, and the desired shaft durability cannot be ensured (Comparative Examples 1 and 3).
(3) If no filler is blended, the oil pumping function deteriorates and sufficient sealing performance cannot be obtained (Comparative Example 2).
(4) If the blending amount of the filler is too large, it tends to become sandy during kneading, making kneading impossible (Comparative Example 4).

Claims (1)

10 to 50 parts by weight of a filler of diatomaceous earth or polytetrafluoroethylene resin having an average particle diameter of 0.2 to 4.0 μm per 100 parts by weight of fluororubber, and the arithmetic mean height Sa of the cross-sectional roughness of the vulcanized molded product is Oil seal for both forward and reverse rotation with a thickness of 0.1 to 1.0 μm and a maximum height Sz of 10 to 20 μm.