JP2571179B2 - Disc brake caliper boots - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc brake for automobiles and general industrial machines, which is provided between a slide shaft and a caliper slidably mounted on a mounting for pressing a friction material against a disc rotor. The present invention relates to a disc brake caliper boot that seals.

[0002]

2. Description of the Related Art Generally, in a disk brake widely used in automobiles and the like, braking is performed by pressing a brake pad made of a friction material with a hydraulic piston against a steel disk rotor rotating with an axle.

The portion in which the hydraulic piston and the hydraulic cylinder are housed is called a caliper, and many recent disk brakes employ a floating caliper having one cylinder in terms of heat radiation effect.

FIG. 1 is a schematic sectional view showing a basic structure of a disc brake provided with a floating caliper.

As shown in FIG. 1, the cylinder body 1 is located inside the caliper 50 near the axle and having a good heat radiation effect.
0 is provided, and a piston 20 is slidably disposed in the cylinder body 10. The first pad A is mounted on the mounting 30 so as to be located at the tip of the piston 20.
Supported by The second pad B is fixed to one end of the caliper 50 main body.

[0006] A steel disk rotor 13 that rotates with the axle is disposed so as to be sandwiched between the first pad A and the second pad B.

The caliper 50 main body is slidably engaged with the mounting 30 fixed to the knuckle 40 by the slide pin 3 and has a floating structure.

[0008] The disc brake provided with the caliper 50 operates as follows during braking.

First, when the driver steps on a brake pedal (not shown), an arrow 7
When the hydraulic pressure in the zero direction is applied, the piston 20 is pushed in the direction of the arrow 80. Thereby, the first pad A is pressed against one surface of the disk rotor 13.

On the other hand, at the same time that the piston 20 is pushed out in the direction of arrow 80, the cylinder body 10
It moves in the direction of the arrow 90 opposite to 0. Thereby, caliper 5
The whole 0 also moves inward as indicated by the arrow 100, and the second pad B fixed to one end of the caliper 50 main body is pressed against the other surface of the disk rotor 13.

FIG. 2 is an enlarged view of a part (dotted frame 101) of the caliper 50 of FIG. As shown in FIG. 2, a slide pin 3 serving as a slide shaft of the cylinder body 10 is fixed to a mounting 30 by a bolt screw 4.

Lubrication of grease or the like lubricated to the engaging portion to prevent water and dust from entering the engaging portion between the slide pin 3 and the cylinder body 10 and to smoothly slide the cylinder body 10 Boots 11 made of an elastic material are fitted to both ends of the slide pin 3 so as to protect the agent.

The boot 11 has a sliding portion a which is fitted to annular projections provided on the inner periphery of both ends of the cylindrical cylinder body 10 and slides together with the cylinder body 10.
And a seal portion b which has a bellows shape and holds a lubricant such as grease.

The conventional disk brake caliper boot 11 as shown in FIG. 4 is itself formed of a rubber composition having no self-lubricating property such as nitrile rubber, acrylic rubber, silicone rubber, etc., and therefore has a large friction coefficient. , It was easy to cause sticking to the sliding shaft. Therefore, by applying a lubricant such as grease to the sliding shaft, the boot 11 for the disc brake caliper is provided with lubricity to prevent the occurrence of sticking.

[0015]

However, in the case of long-term stock, there is a possibility that the lubricant leaks due to the tightening of the seal portion b of the disc brake caliper boot 11, and the lubricant is depleted.

Further, when the disk brake caliper boot 11 is used in such a situation, there is a problem that the sticking easily occurs due to a shortage of the lubricant, and the friction torque is increased, so that the function of the brake operation is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to stabilize a brake operation function for a long period of time, particularly, having excellent surface non-adhesion, low friction characteristics and wear resistance characteristics. It is an object of the present invention to provide a boot for a disc brake caliper capable of performing the following.

[0018]

SUMMARY OF THE INVENTION A disc brake caliper boot according to the present invention comprises a caliper mounted slidably on a mounting and a sliding shaft for pressing a friction material against a disc rotor in a disc brake. A boot that seals a space between a sliding shaft and a part or the whole of which includes a thermoplastic fluororesin as a first essential component, a fluororubber as a second essential component, and a low molecular weight as a third essential component. It is composed of a lubricating rubber composition containing a fluoropolymer.

In the present invention, the thermoplastic fluororesin as the first essential component is a polymer having a carbon chain in a main chain and a fluorine bond in a side chain. Examples of such a thermoplastic fluororesin include, for example, a tetrafluoroethylene polymer (hereinafter abbreviated as PTFE), a tetrafluoroethylene / perfluoroalkylvinyl ether copolymer (hereinafter abbreviated as PFA), and tetrafluoroethylene / hexafluoro Propylene / perfluoroalkyl vinyl ether copolymer (hereinafter abbreviated as EPE), tetrafluoroethylene / hexafluoropropylene copolymer (abbreviated as FEP), tetrafluoroethylene / ethylene copolymer (abbreviated as ETFE) , A trifluorochloroethylene polymer (hereinafter abbreviated as CTFE), a trifluorochloroethylene / ethylene copolymer (hereinafter abbreviated as ECTFE), a polyvinyl fluorolide (hereinafter abbreviated as PVF), and a polyvinylidene Is preferably 1 or more polymers selected from the group consisting of emissions fluoride (hereinafter abbreviated as PVDF).

In particular, there is no fiberization in the kneading step,
ETFE, PFA, and FEP are preferred in consideration of the ease of kneading such as meltability and the maintenance of rubbery elasticity of the final product. In ETFE, MI value (melt-in index) is 1 to 20 g / 10 mi at 300 ° C. and 2160 g.
Those having n are preferred.

Any of the resins described above can be used in catalytic emulsion polymerization,
It can be produced by various polymerization methods such as suspension polymerization, catalyst solution polymerization, gas phase polymerization and ionizing radiation irradiation polymerization. The molecular weight is preferably 50,000 or less,
More than 5,000 and up to about 20,000 are particularly desirable.

As a representative example corresponding to the above conditions, a PF manufactured by Mitsui-Dupont Fluorochemical Co., Ltd.
AMP10, Teflon FEP100 manufactured by Mitsui-DuPont Fluorochemicals Co., Ltd., FPE, Aflon COP manufactured by Asahi Glass Co., Ltd., ETFE, NEOFLON CTFE manufactured by Daikin Industries, CTFE, KF manufactured by Kureha Chemical Co., Ltd.
Polymers, such as Tedlar manufactured by DuPont, which is PVF.

In the present invention, the fluororubber is a polymer or a copolymer of a unit monomer containing one or more fluorine atoms on average, having a glass transition point of room temperature or lower and having elasticity at room temperature. If it is, it is not particularly limited, and a wide range can be exemplified.

Examples of the method of polymerizing the fluororubber include bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, catalyst polymerization, ionizing radiation polymerization, and redox polymerization. The molecular weight of the fluororubber is usually 50,000
0 or more is desirable, and as high a molecular weight as possible gives good results.
Above, particularly preferably 100,000 to 250,000
It is good to use the one of the degree.

Representative examples of the above conditions include, for example, Afras manufactured by Asahi Glass Co., which is a tetrafluoroethylene-propylene copolymer, and DuPont / Showa, which is a vinylidene fluoride-vinylidene fluoride-hexafluoropropylene copolymer. Viton, vinylidene fluoride
Hexafluoropropylene / tetrafluoroethylene copolymer Montefluos technofluorone, fluorosilicone-based elastomer Dow Coating Silastic LS, phosphazene-based elastomer Firestone PNF, and perfluoro-based elastomer Daikin Perflo manufactured by Daikin Industries, Ltd. can be mentioned.

The composition obtained by mixing the above fluororubber and thermoplastic fluororesin has properties as an elastic body. In the present invention, the low-molecular-weight fluoropolymer as the third essential component is blended in order to provide such an elastic body with more excellent sliding properties.

In the present invention, the low molecular weight fluoropolymer, tetrafluoroethylene (TFE), main structural unit -C _n F _2n -O- _(n is an integer from 1 to 4) fluoropolyether having major Structural unit

[0028]

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A compound having a molecular weight of 50,000 or less among polyfluoroalkyl group-containing compounds having 2 to 20 carbon atoms. In order to provide excellent sliding characteristics,
The molecular weight of the low molecular weight fluoropolymer is particularly preferably 5,000 or less. Among such low molecular weight fluoropolymers, those having an average particle size of 5 μm or less of the tetrafluoroethylene low order polymer represented by the following formula are particularly preferable.

[0030]

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Examples of such a material include Vidax AR manufactured by DuPont and Fluonbrant L169 manufactured by Asahi Glass.

Next, as a fluoropolyether having an average molecular weight of 50,000 or less and having a main structural unit of —C _n F _2n —O— (n is an integer of 1 to 4),

[0033]

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And the like. Such polymers have structural units containing functional groups such as isocyanate groups, hydroxyl groups, carboxyl groups, and ester groups in order to improve the affinity (adhesion) to other compounding materials and additives. desirable.

The following are specific examples of such a fluoropreether.

[0036]

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These fluoropolyethers may be used alone or in combination. Further, a fluoropolyether containing activated hydrogen in the functional group and an isocyanate compound containing no polyfluoroether group may be used in combination. In addition, a method of using a fluoropolyether having an isocyanate group in combination with a diamine, a triamine, or a diol or a triol that does not contain various fluoropolyether groups is employed. You may.

In particular, it is preferable to use a combination of fluoropolyethers whose functional groups react with each other to increase the molecular weight. As such, for example,
It is likewise preferred to combine those having units containing isocyanate groups with those containing units containing hydrogen groups.

Examples of the compound having a polyfluoroalkyl group include compounds having a polyfluoroalkyl group as shown below.

[0040]

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As those having the above-mentioned polyfluoroalkyl group (with 2 to 20 carbon atoms) and having an average molecular weight of 50,000 or less,

[0042]

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A polymer of a reaction product of a compound having a reactive group and a polyfluoroalkyl group with an ethylenically unsaturated compound having a group that reacts with the reactive group (for example, fluoroalkyl acrylate, etc.); Examples include a reaction product of a compound having a reactive group and a fluoroalkyl group with various polymers having a group that reacts with the reactive group, or a polycondensate of the compound.

As with the above-mentioned fluoropolyalkyl group, the compound containing a polyfluoroalkyl group can be used to improve the affinity (adhesion) of other compounding materials and additives with a functional group having a high affinity, for example, an isocyanate group. Compounds having a unit containing a hydroxyl group, a mercapto group, a carboxyl group, an epoxy group, an amino group, a sulfone group and the like are preferred.

These polyfluoroalkyl group-containing compounds may be used alone or in combination. Further, a polyfluoroalkyl group-containing compound having a reactive group having activated hydrogen and an isocyanate compound having no polyfluoroalkyl group may be used in combination. Also,
Polyfluoroalkyl group-containing compound having an isocyanate group, and various polyfluoroalkyl group-free diamines, toluamines or various polyfluoroalkyl group-free diols, triols and the like to adopt a method such as combined use Is also good.

The combination of the functional groups is preferable from the viewpoint of increasing the strength, and specifically has at least a polyfluoroalkyl group having 2 to 20 carbon atoms and at least one selected from a hydroxyl group, a mercapto group, a carboxyl group and an amino group. A combination with a fluorine-containing polymer containing one kind or a fluorine-containing polymer having a polyfluoroalkyl group having 2 to 20 carbon atoms and having a unit containing an isocyanate group;
And a combination with a fluoropolymer having a unit having a reactive group having an activated hydrogen.

Of these low molecular weight fluoropolymers,
Using tetrafluoroethylene polymer or fluoropolyether gives excellent results in lubricity,
In particular, it has been found that the use of a tetrafluoroethylene polymer provides the most desirable results.

In the present invention, the compounding ratio of the fluororubber and the thermoplastic fluororesin is preferably such that the weight ratio of the fluororubber to the thermoplastic fluororesin is from 50:50 to 95: 5. 50% by weight of thermoplastic fluororesin
If it exceeds / 100, sufficient elastic properties cannot be obtained for the target composition, and if it is less than 5/10, sufficient wear resistance cannot be obtained.

It is preferable that the low molecular weight fluoropolymer is 5 to 50 parts by weight based on 100 parts by weight of the total of the fluororubber and the thermoplastic fluororesin. If the blending ratio of the low molecular weight fluoropolymer is less than 5 parts by weight, sufficient sliding properties cannot be obtained, and if it exceeds 50 parts by weight, the rubbery elastic properties are impaired.

In addition, the above lubricating rubber composition is
Abrasion resistance can be improved by adding a cured powder of a thermosetting resin that is not melted at 00 ° C. or a heat-resistant resin powder having a glass transition point of 300 ° C. or higher.

Examples of the thermosetting resin powder include fine powder after thermosetting such as a phenol resin and an epoxy resin, and examples of the heat resistant resin having a glass transition point of 300 ° C. or higher include polyimide resin and aromatic aramid resin. Fine powder.

Among the commercially available resin powders, phenol resin cured and pulverized products include Bell Pearl H300 manufactured by Kanebo Co., Ltd.
As a cured and crushed product of polyimide resin, Mikasa Sangyo Co., Ltd .:
As PWA20, pulverized aromatic aramid resin, MP-P manufactured by Asahi Kasei Corporation, and thermoplastic resin powder having a glass transition point Tg of 300 ° C. or higher include UPILEX S (Tg> 500) manufactured by Ube Industries, Ltd. is there.

The particle size of such a thermoplastic resin powder is 1
A material having a size of −15 μm is desirable in terms of maintaining rubber-like elasticity and easiness of the kneading step. The thermosetting resin powder is preferably added in an amount of 5 to 20% by weight based on the first to third essential components. If the content is less than 5% by weight, the effect of improving the wear resistance will not be obtained.
A large amount exceeding the weight% is not preferable because rubber elasticity decreases.

Various additives may be added in addition to the above components as long as the object of the present invention is not impaired. For example,
As a vulcanizing agent for fluoro rubber, isocyanurate, organic peroxide, etc., sodium stearate, magnesium oxide,
And an antioxidant such as calcium hydroxide, or an acid acceptor, an antistatic agent such as carbon, a filler such as silica and alumina, other metal oxides, a coloring agent, and a flame retardant may be appropriately added. Needless to say.

The method of mixing the above-mentioned various raw materials is not particularly limited, and the raw materials can be mixed by a method generally used widely. For example, the elastomer and other materials that are the main raw materials may be individually and sequentially mixed simultaneously or simultaneously by a roll mixer or other mixer. At this time, it is desirable to provide a temperature controller in order to prevent heat generation due to friction.

When a roll mixer is used,
As a finishing mixture, it is more preferable to tightly tighten the roll interval to about 3 mm or less and perform tight milling.

[0057]

The boot for a disc brake caliper seals between the caliper slidably mounted on the mounting and the sliding shaft, and slides with the caliper that slides itself. It has been demanded that appropriate lubricity can be maintained for a long period of time and that fatigue is less likely to occur.

The disk brake caliper boot according to the present invention has a small coefficient of friction against sliding of the caliper because the portion or the whole thereof in contact with the sliding shaft is formed of a lubricating rubber composition. Excellent wear resistance and moderate rubber-like elasticity makes it less likely that bellows-like parts will fatigue. Appropriate lubricity can be maintained between the caliper and the sliding shaft. For this reason, compared with the conventional boot for disc brake calipers, it is excellent in durability and can stabilize the brake operation function for a long time.

[0059]

EXAMPLE In an example according to the present invention, a boot 1 for a disc brake caliper as shown in FIG. 3 was formed of a lubricating rubber composition. The lubricating rubber composition comprises a thermoplastic fluororesin as the first essential component, a fluororubber as the second essential component, and a low molecular weight fluoropolymer as the third essential component.

The raw materials used in Examples and Comparative Examples 1 and 2 are collectively shown below. The mixing ratio of each component is all weight%, but the raw materials shown in (3) to (9) are weight% based on the total weight 100 of the raw materials shown in (1) and (2).

(1) Vinylidene fluoride / fluoropropylene copolymer (Technoflon FOR4 manufactured by Asahi Monte Co., Ltd.)
20) (2) Tetrafluoroethylene / ethylene copolymer
(Aflon COP manufactured by Asahi Glass Co., Ltd.) (3) Low molecular weight fluoropolymer (low molecular weight TFE)
(Lubricant L169 manufactured by Asahi Glass Co., Ltd.) (4) Low molecular weight fluoropolymer (low molecular weight PFPE)
(Fomblin Z-DISO manufactured by Anyimont Japan
C) (5) Carbon (MT carbon manufactured by Fadelbild) (6) Sodium stearate (general industrial material) (7) Magnesium oxide MgO (general reagent) (8) Calcium hydroxide Ca (OH) ₂ (general reagent) ( 9) Phenolic resin (Kanebo Bell Pearl H3)
00) (10) Nitrile-butadiene copolymer (NBR)
(General industrial material hardness JIS-A70) First, the fluororubber (1) is wound around a roll mixer adjusted to a roll interval of about 5 to 10 mm, and MT carbon, sodium stearate, Mg
O and Ca (OH) ₂ were added and kneaded. Thereafter, the roll interval was adjusted to 1 mm, and mastication was performed about 10 times. At this time, in order to prevent frictional heat, cooling water was always passed through the roll, and the roll temperature was maintained at 60 ° C. or lower. Next, the cooling water was stopped, steam was passed through the roll, the rubber temperature was adjusted to 70 ° C. or more and 90 ° C. or less, and then the roll interval was returned to about 5 to 10 mm, and the low molecular weight fluorine-containing polymer was removed. While adding little by little, kneading was performed at the compounding ratio of each example shown in Table 1. After that, again set the roll interval to 1m
m and mastication was performed 10 times.

[0062]

[Table 1]

In the compound obtained in the above steps, 150 × 150 × 1t sheet was subjected to primary vulcanization (170
C., 10 minutes, press pressure 7 kgf / cm ² ), and secondary vulcanization (230 ° C., 16 hours, free) was performed.
Friction test, abrasion test, non-adhesiveness and elastic properties were obtained for each test piece. The method of each test is as shown below.

Test method <Friction test> The obtained test pieces were tested for inner diameter φ17 and outer diameter φ2.
1. Processed to a thickness of 2 mm and bonded to a φ17 × φ21 × 10 mm SPCC ring piece to obtain a test piece. The partner material is S
UJ2 (bearing steel) φ6 × φ33 × 6 mm disk-shaped test pieces were evaluated using a thrust-type friction tester. The test conditions were a sliding speed of 1 m / min and a surface pressure of 3 kgf / cm ² . The coefficient of friction after 50 hours is shown in Table 2.

<Abrasion test> The sliding speed was 30 m / min and the surface pressure was 1.7 kgf /
Under the condition of cm ² , SUJ2 (bearing steel) φ6 × φ33 ×
Table 2 shows the results obtained with a 6 mm disc-shaped test piece as the mating material.
Are also shown.

<Non-Adhesiveness Test> The contact angle of the obtained test piece was measured one minute after dropping water as a sample liquid by a goniometer type contact angle measuring instrument. The measurement results are shown in Table 2. . In this test, the larger the contact angle, the better the non-adhesion.

[0067]

[Table 2]

Comparative Examples 1 and 2 Specimens having the same dimensions as the examples were processed with the NBR (Comparative Example 1) and the fluororubber composition (Comparative Example 2) shown in Table 1, and the thrust-type friction and wear described above were obtained. Using a tester, friction and wear tests were performed under the same conditions as in the examples, and the results are shown in Table 2.

A non-adhesion test was also conducted in the same manner as in the examples, and the results are shown in Table 2.

The boot for a disc brake caliper according to the present embodiment is formed of a lubricating rubber composition, so that the kinetic friction coefficient, the wear coefficient and the contact angle shown in Table 2 clearly show the comparison. It can be seen that the sliding resistance is reduced as compared with the disc brake caliper boots of Example 1 and Comparative Example 2, and that it has excellent wear resistance and non-adhesiveness.

As described above, according to the present invention, it is possible to provide a boot for a disc brake caliper having a low torque, a long life, and a sealing property and a sliding property as compared with a conventional boot for a disc brake caliper.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic structure of a disc brake provided with a floating caliper as a background of the present invention.

FIG. 2 is an enlarged view of a part of the disc brake caliper shown in FIG.

FIG. 3 is a sectional view of a boot for a disc brake caliper according to an embodiment of the present invention;

FIG. 4 is a sectional view of a conventional boot for a disc brake caliper.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Disc brake caliper boot 3 Slide pin 4 Bolt screw 10 Cylinder body 30 Mounting In each figure, the same code | symbol shows the same or equivalent part.

Claims (7)

(57) [Claims] 1. A disc brake caliper boot for sealing a space between a caliper slidably mounted on a mounting and a sliding shaft in order to press a friction material against a disc rotor in a disc brake. A lubricating rubber in which a part or the whole in contact with a moving shaft is blended with a thermoplastic fluororesin as a first essential component, a fluororubber as a second essential component, and a low molecular weight fluoropolymer as a third essential component A boot for a disc brake caliper, comprising a composition. 2. The boot for a disc brake caliper according to claim 1, wherein a hardened powder of a thermosetting resin or a heat-resistant resin powder having a glass transition point of 300 ° C. or higher is added to the lubricating rubber composition. . 3. The thermoplastic fluororesin as the first essential component is a tetrafluoroethylene / ethylene copolymer, a tetrafluoroethylene / perfluoroalkylvinyl ether copolymer and a tetrafluoroethylene / ethylene copolymer.
The disc brake caliper boot according to claim 1, wherein the boot is at least one member selected from the group consisting of hexafluoropropylene copolymers. 4. The boot for a disc brake caliper according to claim 1, wherein the fluoro rubber as the second essential component is a fluoro rubber having a molecular weight of 100,000 to 250,000. 5. The fluororubber as the second essential component is a tetrafluoroethylene / propylene copolymer, a vinylidene fluoride / hexafluoropropylene copolymer,
The disc brake caliper according to claim 1, wherein the disc brake caliper is at least one polymer selected from the group consisting of a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, a fluorosilicone copolymer, and a perfluoro-based copolymer. Boots. 6. The low-molecular-weight fluorine-containing polymer as the third essential component is selected from the group consisting of a fluoroolefin polymer having an average molecular weight of 50,000 or less, a fluoropolyether and a polyfluoroalkyl group-containing compound.
The disc brake caliper boot according to claim 1, wherein the boot is a polymer of at least one kind. 7. The low-molecular-weight fluorine-containing polymer as the third essential component is a tetrafluoroethylene polymer.
The boot for a disc brake caliper according to claim 1.