JP2000205318A - Friction material for brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent rust from generating on a rotor surface due to wetting of a rotor or a friction pad by combining a material effective for rust prevention with friction material for brake constituted of fiber base material, friction regulating material, and binding material. SOLUTION: Following material effective for rust prevention of iron is combined with friction material for brake singly or in a plurality of sorts. Namely, following is used. 1) metallic powder of lower standard electrode potential than iron - example: zinc powder. 2) metallic oxide powder of lower standard electrode potential than iron- example: zinc oxide powder. 3) alkali metallic salt, alkali earth metallic salt, alkali metallic salt or alkali earth metallic salt of molybdic acid (or boric acid) - example: sodium molybdate (or lithium, calium, or the like). 4) organic substance having rust prevention effect, fluorine series polymer powder - example: PTFE, FEP, PVdF. 5) strong alkali material - example: hydroxide (calcium hydroxide or the like) of alkali metal, alkali earth metal, or carbonate (sodium carbonate) of alkali metal. alkali earth metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material for a brake used in a motor vehicle, and more particularly to a friction material for a brake having reduced brake noise, in particular, creep goo noise at the start of an automatic vehicle.

[0002]

2. Description of the Related Art Recently, a friction material having a high porosity of 10 to 30% has been used as a friction material mainly used for a brake or the like in order to improve fade resistance and high-speed effectiveness. . By the way, when the friction material gets wet with water due to driving in rainy weather, passing through a puddle, or the like, or when the vehicle is stopped outdoors at night, the friction material easily absorbs moisture therein. Then, the friction material that has absorbed the moisture is in the process of drying the water, immediately before stopping at the time of braking, at a speed of approximately 5 km / h or less, or at the time of starting in an automatch vehicle, that is, stepping on the brake petal,
While the brake pedal is loosened in the D range and the brakes are completely released, creeping force causes the brakes to be dragged and a low-frequency noise is generated while starting at a very low speed. This low frequency noise is also called "creep goo" and is disliked because it causes discomfort. This low frequency noise is
The larger the porosity of the friction material, the more water it absorbs. Further, when the friction material absorbs moisture, there is a problem that a squealing noise is generated at the time of braking, or a friction coefficient becomes too high and an abnormal effect is generated.

[0003] The cause of such a creep goo noise has been examined. Rust generated on the braking surface of the rotor causes a stick-slip phenomenon due to frictional engagement with a friction material, which is the cause of the creep goo noise. I understood. In this regard, the rust-prevention treatment of the rotor is also effective in preventing creep goo noise, but the friction engagement with the friction material wears the braking surface of the rotor.
The effect of the rust prevention treatment gradually disappears, and the effect cannot be maintained for a long time.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a friction material for a brake which has a reduced brake noise, especially a creep goo noise at the start of an automatic vehicle.

[0005]

According to the present invention, when the rotor or the friction pad is wet by washing with water or the like, the creep goo noise at the time of starting increases because the friction material contains water and produces an unusual noise during friction. Rather than the problem of letting the rotor and friction pad get wet, rust is generated on the rotor surface, and as described above, emphasis is placed on causing creep goo noise, and the rust is not generated. It is. That is, the present invention has solved the above-mentioned problems by the following means. (1) A brake friction material comprising a fiber base material, a friction adjusting material, and a binder, the material having an effect of preventing rust of iron.

[0006] In a friction portion in an automobile or a vehicle, a friction material is pressed against a rotor or a drum made of an iron-based material to apply a brake. For this reason, the friction surface of the rotor or drum is constantly pressed by the friction material and is in a polished form, exposing a new metal surface.
Since this metal surface is very easily rusted, rust is immediately generated in a state of being splashed with water as described above. According to the present invention, in order to solve this problem, a material having an effect of preventing rust of iron is added to a friction material for a brake.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In other words, even if a material effective in preventing rust of iron is compounded, the range is wide. Therefore, this point will be specifically described as follows. May be used alone or in combination. Metal powder having a lower standard electrode potential than iron (preferably 3 parts by weight) A metal powder having a higher ionization tendency than iron, if it is easily understood. Example: Zinc powder A metal oxide powder having a lower standard electrode potential than iron (preferably 5 parts by weight) A metal oxide powder having a higher ionization tendency than iron when it is commonly understood. Example: zinc oxide powder

An alkali metal salt (preferably 1 part by weight) or an alkaline earth metal salt (preferably 5 parts by weight) An alkali metal salt of molybdic acid (or boric acid, phosphoric acid, chromic acid, dichromic acid) or alkaline earth metal Metal salts Example: Sodium molybdate (or lithium, potassium, etc.), sodium borate, calcium molybdate (or magnesium, etc.) Organic substance having a rust-preventive effect (preferably 1.5 parts by weight) Fluorine-based polymer powder Example: 4 Fluorinated ethylene polymer (PTFE) Tetrafluoroethylene-hexafluoropropylene copolymer (FEP) Polyvinylidene fluoride (PVdF) Strong alkali material (preferably 3 parts by weight) Example: Alkali metal alkaline earth metal hydroxide ( Calcium hydroxide, etc.) or alkali metal alkaline earth metal carbonates (carbonic acid) Sodium, etc.)

The above-mentioned substance has an effect of preventing the dissolution of iron by dissolving zinc powder before iron, for example, like tin. The above-mentioned substances are not so often used that their metal oxides have a lower standard electrode potential than iron, and zinc oxide alone does not have such an effect, so it is better to use it in relation to other substances. . The above-mentioned substances are known to have a rust-preventing effect on iron in the iron surface treatment technology, but are not included in the friction material because they are special substances. Since the substance has heat resistance, it does not decompose even in frictional joining between the rotor and the friction material, but rather melts a little by the heat, or becomes a liquid and covers the rotor surface thinly, so the rust-preventive effect of the rotor There is. These substances may be added alone to the friction material, or may be used in combination. The amounts of these substances used are preferably as described above with respect to the basic material in order to prevent the generation of rust, and the upper limit is about twice the above-mentioned preferred amount. The basic characteristics (abrasion resistance-coefficient of friction, etc.) are hindered.

According to the present invention, not only when the friction pad absorbs moisture during parking for a long time such as at night (hereinafter simply referred to as "moisture absorption") but also when the car is washed, etc. It is possible to effectively reduce creep goo noise when the pad is wet with water (hereinafter, simply referred to as “when wet with water”). In order to manufacture the friction material for a brake of the present invention, the above-mentioned powders are blended in a friction material composed of a fiber base material, a friction modifier, a lubricant, and a binder, and the blend is preformed according to a normal manufacturing method. Then, it can be manufactured by thermoforming. In addition, when a substance having a large water solubility is blended in or in, an alkali metal salt can be blended, or an alkali metal salt aqueous solution can be impregnated after thermoforming without previously blending the alkali metal salt. . Examples of the alkali metal salt include sodium molybdate, sodium carbonate, lithium carbonate, and sodium borate. As the tetrafluoroethylene polymer, for example, Fluon Bricant L169 manufactured by Asahi Glass Co., Ltd.
J, L170J and the like can be used.

In the case where the friction material is impregnated later, an aqueous solution of an alkali metal salt is impregnated after the finishing step in the production process of the friction material. However, the impregnation may be performed before the finishing step. As the impregnation method, means such as a vacuum impregnation method, coating, and doweling can be used, but the vacuum impregnation method is preferable because the impregnation efficiency inside the friction material is good. After the impregnation, a drying treatment is performed at 110 ° C. for 1 hour.

FIG. 1 shows a manufacturing process of a friction pad for a disc brake, which is formed into a predetermined shape by a sheet metal press, subjected to a degreasing process and a primer process, and is coated with an adhesive. Combine fiber base materials such as organic fibers, inorganic fibers, and metal fibers with powdered raw materials such as inorganic / organic fillers, friction modifiers, and thermosetting resin binders. The preformed body formed by molding at a predetermined pressure (preliminary molding) is thermoformed at a predetermined temperature and pressure in a thermoforming step, and the two members are fixed together, after-cured, and finally finished The steps before the treatment are the same as the conventional method.

Examples of the above-mentioned heat-resistant organic fibers include aromatic polyamide fibers and flame-resistant acrylic fibers. Examples of the inorganic fibers include ceramic fibers such as potassium titanate fibers and alumina fibers, glass fibers, carbon fibers, and rock fibers. Wool and the like can be mentioned, and examples of the metal fiber include a copper fiber and a steel fiber. Examples of the inorganic filler include metal particles such as copper, aluminum, and zinc, scaly inorganic substances such as balm curite and mica, and particles such as barium sulfate and calcium carbonate.Examples of the organic filler include synthetic rubber and Cashew resin and the like. Examples of the thermosetting resin binder include phenol resins (including various modified phenol resins such as straight phenol resins and rubbers), melamine resins, epoxy resins, and cyanate ester resins. Examples of the friction modifier include metal oxides such as alumina and silica, magnesia, zirconia, chromium oxide, and quartz. Examples of the solid lubricant include graphite and molybdenum disulfide.

[0014]

The present invention will be described in detail with reference to the following examples. However, the present invention is not limited to only these examples.

Examples (Examples of Formulation of Friction Material as Basic Material) Phenol resin 20 vol% Aramid pulp 15 vol% Friction modifier 65 vol% (cashew dust, titanium, magnesia, graphite)

(Preparation of Samples of Examples and Comparative Examples) Pads of Examples 1 to 6 were prepared by a conventional manufacturing method by blending 100 parts by weight of the above-mentioned basic material with a material having an antirust effect. The results of a test on the occurrence of rust and creep goo noise on the rotor are shown below. Was. Example 1 (Example 1) Metal zinc powder 3 parts by weight Example 2 (Example 2) Zinc oxide powder 5 parts by weight Example 3 (Example 3) 1 part by weight of sodium molybdate Example 4 (Example 4) Calcium molybdate 5 Parts by weight Example 5 (Example 5) tetrafluoroethylene polymer powder 1 part by weight Example 6 (Example 6) 4 parts by weight of calcium hydroxide Example 7 (comparative example) (without the above additives) 0 parts by weight It is a combination of the above. Note) 1. According to preliminary experiments, when the sodium molybdate powder exceeds 5 parts by weight, the water absorption becomes too large, and the friction pad swells, causing dragging of the brake and noise.

(Test Method) A vehicle equipped with a new rotor and a disk brake using the friction pad of the above sample was mounted on a vehicle.
After running every km, a brake was applied at an initial speed of 50 km / h to stop the vehicle. After sufficient running between the friction pad and the rotor was obtained by running 200 km, the following test was performed. (1) Moisture Absorption Test (Part 1) The vehicle was left in an environment room at a room temperature of 20 ° C. and a temperature of 95% (humidity at which a creep goo sound is likely to be generated) for 12 hours, and the speed of 20 km / h
At a speed of h, braking was performed at a deceleration of 0.2 G, and a sensory test was performed for the generation of creep goo noise. (2) Moisture Absorption Test (Part 2) The vehicle was left in an environment room at a room temperature of 20 ° C. and a temperature of 95% (humidity at which a creep goo sound is likely to be generated) for 36 hours, and the speed was 20 km / h.
At a speed of h, braking was performed at a deceleration of 0.2 G, and a sensory test was performed for the generation of creep goo noise. (Test results) The test results are shown in Table 1.

[0018]

[Table 1]

In the two-stage display in each column of Table 1, for example, "small / small", the first half "small" indicates that the rust on the braking surface is very small, and the second half "small" indicates. , Indicating that the generation of creep goo noise is small. -"Rust generation rate (area ratio) on the braking surface" in Table 1: Large: 70% or more to 100%: Medium: Less than 70% to 40%: Small: Less than 40% To 15%,: minute ... less than 15% to 1%,: none ... less than 1%,-creep goo sound evaluation criteria 12 hours left ... minute or less passed 36 hours left ... small or less passed

[0020]

According to the present invention, not only when the friction pad absorbs moisture due to parking for a long time such as at night, but also when the rotor and the friction pad get out of the friction material when the car and the like are wet, the creep goo may come out. Sound can be effectively reduced. Since the friction material of the present invention contains a substance that prevents the generation of rust in iron materials such as rotors, it is possible to effectively prevent the generation of rust in iron materials that are the cause of the generation of creep goo noise, and to reduce creep goo noise. Can be reduced. Therefore, the amount of the compound for preventing the generation of rust may be small, and the friction coefficient of the friction material is not reduced. Further, rust transferred from the rotor to the sliding surface of the friction material can be prevented by frictional engagement between the rotor and the friction material, which is effective in reducing creep goo noise. Further, the substance salt for preventing the generation of rust used for that purpose can be easily mixed and compounded as a powder in the production of the friction material. The present invention is applicable not only to a disc brake but also to a lining of a brake shoe of a drum brake.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of a production process of a friction material of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Michinori Yanagi 19-5 Nihonbashi Koamicho, Chuo-ku, Tokyo Inside Akebono Brake Industry Co., Ltd. (72) Inventor Junichi Ito 19th Nihonbashi Koamicho, Chuo-ku, Tokyo No. 5 Akebono Brake Industry Co., Ltd. (72) Inventor Masami Takebayashi 19-5 Nihonbashi Koami-cho, Chuo-ku, Tokyo F-term inside Akebono Brake Industry Co., Ltd. 3J058 BA21 FA01 GA23 GA24 GA26 GA27 GA33 GA34 GA35 GA37 GA38 GA45 GA50 GA55 GA57 GA58 GA92 GA95 4K018 AB08 KA05

Claims (1)

[Claims] 1. A brake friction material comprising a fibrous base material, a friction adjusting material, and a binding material, comprising a material effective for preventing rust of iron.