JP6254424B2 - Friction material - Google Patents

Description

  The present invention relates to a friction material, and more particularly, to a friction material that maintains a friction material strength and a friction coefficient and reduces brake vibration in a friction material used for an automobile brake.

Conventionally, friction materials used for brakes and the like are manufactured by a manufacturing process including steps such as preforming, thermoforming, and finishing using a fiber base material, a friction adjusting material, a filler, and a binding material. ing. As friction materials used for brakes, etc., organic fibers such as aramid fibers, inorganic fibers such as glass fibers, fiber base materials such as metal fibers such as copper fibers, rubber dust, cashew dust, metal particles, ceramic particles and graphite, Organic / inorganic friction modifiers such as elastic graphite, fillers such as calcium carbonate and barium sulfate, and binders such as phenol resins are used.
Above all, elastic graphite used as a friction modifier is used in various environments when used as a friction material component because of its lubricity and especially its excellent thermal and chemical stability. In order to reduce noise while maintaining damping characteristics, friction materials added with elastic graphite have been studied.
In the case of a friction material, in order to improve fade resistance, a metal having a high thermal conductivity, particularly a hard material such as a copper fiber or a copper particle or an abrasive material, may be added.

For example, in Patent Document 1, in order to prevent premature seizure that occurs as a result of the local friction of the friction material, when a load of 9000 kg / cm ² is applied as a reference, a load of 0.1 kg / cm ² is applied. It describes that high elastic graphite having a volume compression rate of 80% or more and a recovery rate of 50% or more when the load is removed is blended in the friction material as a filler.

  In Patent Document 2, in a non-asbestos-based friction material using a fiber base material, a friction modifier, and a binder, friction characteristics are obtained by blending 0.5% to 2.5% by volume of partially graphitized coke. A non-asbestos-based friction material is described in which the amount of compressive strain of the friction material is adjusted to improve the brake feeling without deteriorating.

  Patent Document 3 aims to provide a friction material that is excellent in fading performance while maintaining good damping characteristics, that is, having a low coefficient of friction reduction at high speed and high load, does not contain organic dust, A friction material comprising a fiber base material, a binder, and a filler and containing 5 to 25% by weight of elastic graphite having an average particle diameter of 0.1 to 5.0 mm is described.

  Patent Document 4 discloses a friction material including a fiber base material, a binding material, and a friction modifier. By blending a grinding material such as chromite or zirconium silicate as a friction modifier, high speed without deteriorating the rotor attacking property. It is described that a friction material with improved effectiveness and fading characteristics can be obtained.

  In Patent Document 5, a friction material including a fiber base material, a friction modifier, and a binder contains potassium titanate powder, steel fiber, calcium pyrophosphate, and iron oxide, and is sufficient even in an ultrahigh temperature range around 700 ° C. It has excellent fading characteristics and excellent friction strength. Further, according to the friction coefficient, wear resistance, vibration characteristics, squealing characteristics, etc., it may be blended with abrasives such as alumina, magnesia, zirconia, chromium oxide, chromite alone or in combination of two or more. Has been.

Japanese Patent Application Laid-Open No. 3-282020 JP 2007-326999 A JP 2009-155439 A JP 2010-222555 A JP2012-52069A

  On the other hand, in recent years, market demands regarding vibration characteristics in automobile brakes as well as brake squeal are high, and it is indispensable to satisfy both friction characteristics and vibration characteristics such as heat resistance strength, friction coefficient, and wear life. However, in the prior art, a friction material having both friction characteristics and vibration characteristics (torque fluctuation amount) has not been put into practical use.

  Therefore, the problem to be solved by the present invention relates to a friction material containing elastic graphite used for a friction member such as a disc brake pad and a drum brake shoe of an automobile brake device, even if the amount of copper component is suppressed. It is an object of the present invention to provide a friction material that has both improved wear resistance and friction and vibration characteristics compatible with a wide range of vehicle types, while hardly deteriorating other characteristics.

  As a result of intensive studies in order to solve the above problems, the present inventors have found that in a friction material comprising at least a fiber base material, a friction modifier and a binder, the copper content is 5 mass in terms of copper element. It was found that the friction characteristics and vibration characteristics can be made compatible by using elastic graphite, chromite and steel fibers in combination, and the present invention has been completed.

That is, the subject of this invention was achieved by the following friction material.
(1) A friction material including a fiber base material, a friction modifier and a binder, wherein the content of at least one copper component selected from copper, a copper alloy and a copper compound is 5% by mass or less in terms of copper element. A friction material containing 2 to 7% by mass of elastic graphite, 3 to 10% by mass of chromite, and 3 to 15% by mass of steel fiber.
(2) The friction material according to (1), wherein the content of the copper component is 0.5% by mass or more in terms of copper element.
(3) The friction material according to (2), wherein the copper component is fibrous.
(4) The friction material according to (2) or (3), wherein the copper component is at least one of copper fiber and brass fiber.

For the purpose of controlling brake vibration (torque fluctuation), the friction material added with elastic graphite and blended with chromite and steel fiber suppresses the decrease in the friction coefficient, ensuring an appropriate friction coefficient and wear life. A friction material having good friction characteristics can be provided.
In addition, the friction material of the present invention is a friction material that can ensure heat resistance strength and friction characteristics without containing a large amount (more than 5% by mass) of a copper component.

  Hereinafter, although the form for implementing this invention is demonstrated in detail, the following embodiment is an illustration and this invention is not limited to these.

In the friction material of the present invention, elastic graphite, chromite and steel fibers are blended, and the content of the copper component is 5% by mass or less. If content of a copper component is 5 mass% or less, it is preferable at the point with little load to an environment.
The content of the copper component is calculated in terms of copper element. When the friction material of the present invention contains a copper component, it may be contained as a simple copper, and may be contained in a state of a copper alloy containing manganese, aluminum, tin or the like in copper, zinc and nickel. , And may be included as a copper compound such as an oxide or sulfide.

  The elastic graphite used in the present invention is obtained by graphitizing raw coke for graphitizing in order to obtain elastic graphite. The graphitization rate is 80%. It is preferable to be -95%. Examples of the raw coke include carbonaceous mesophase or raw coke produced when coal tar pitch, coal pitch, petroleum pitch, etc. are heat-treated at about 350 to 500 ° C., or these are mixed acid of nitric acid or nitric acid and sulfuric acid. Examples of the conventional raw material for producing elastic graphite, such as those treated, can be mentioned.

  The average particle size of the elastic graphite is preferably 0.1 to 1.0 mm. If the average particle diameter of the elastic graphite is within this range, the porosity of the friction material can be effectively increased while the elastic modulus of the friction material is improved satisfactorily. Thereby, in addition to good damping characteristics, the organic substance decomposition gas generated during the fading can escape to the pores in the elastic graphite, and the fading performance is improved. If the average particle diameter of the elastic graphite is 0.1 mm or more, the damping characteristic is maintained, which is preferable. On the other hand, if the average particle diameter of the elastic graphite is 1.0 mm or less, the dispersibility of the fiber base material is maintained, which is preferable. Further, the recovery rate of elastic graphite is preferably 50% or more at a compression rate in the range of 10 to 90%. If the recovery rate at a compression rate of 10 to 90% is 50% or more, a good elastic modulus of the friction material can be obtained. More preferably, the recovery rate is 70% or more at a compression rate in the range of 10 to 90%. Alternatively, the recovery rate at a compression rate of 50% is 70% or more, and preferably the recovery rate at a compression rate of 50% is 90% or more.

The content of elastic graphite is 2 to 7% by mass with respect to the total amount of the friction material. By setting the content of elastic graphite to 2% by mass or more, the damping characteristics of the friction material can be sufficiently exerted and brake vibration can be suppressed. On the other hand, the fall of a friction coefficient can be suppressed by content of elastic graphite being 7 mass% or less.
In the friction material, elastic graphite may be used in combination with conventional graphite (natural graphite, artificial graphite).

In blending the friction material, a material that is usually used is used as long as the gist of the present invention is met. Organic fiber, inorganic fiber, and metal fiber are used as the reinforcing fiber substrate.
Examples of organic fibers include aromatic polyamide (aramid) fibers, flame resistant acrylic fibers, and cellulose fibers. Examples of inorganic fibers include ceramic fibers such as potassium titanate fibers and alumina fibers, and biosoluble inorganic fibers. , Glass fiber, carbon fiber, rock wool, and the like, and examples of the metal fiber include steel fiber, copper fiber, brass fiber, and the like, and these can be used alone or in combination of two or more.

The friction material of the present invention includes steel fibers. The steel fiber has an effect of maintaining the strength of the friction material, and the content is 3 to 15% by mass with respect to the total amount of the friction material, and preferably 5 to 10% by mass.
The friction material of the present invention may contain copper components such as copper fibers and brass fibers. The copper component is preferably 0.5 to 5% by mass and more preferably 1 to 5% by mass with respect to the total amount of the friction material. A small amount of copper fiber or brass fiber is preferably blended together with elastic graphite in order to improve vibration characteristics.

  In order to ensure sufficient mechanical strength, the content of the fiber base material is preferably 10 to 40% by mass, more preferably 10 to 30% by mass with respect to the total amount of the friction material.

  The binder is made of a thermosetting resin, and as the thermosetting resin, phenol resin, melamine resin, epoxy resin, polyimide resin, resins obtained by modifying these thermosetting resins with cashew oil, silicone oil, various elastomers, Examples include resins in which various elastomers, fluoropolymers and the like are dispersed in these thermosetting resins, and these can be used alone or in combination of two or more. In order to secure sufficient mechanical strength and wear resistance, the content of the binder is preferably 5 to 15% by mass, and more preferably 5 to 10% by mass with respect to the total amount of the friction material.

As friction modifiers, organic fillers such as resin dust, rubber dust (pulverized tire tread rubber), unvulcanized rubber particles, vulcanized rubber particles, barium sulfate, calcium carbonate, calcium hydroxide , Inorganic fillers such as non-whisker-like titanate compounds such as vermiculite, mica, potassium titanate, lithium potassium titanate, magnesium potassium titanate, silicon carbide, alumina, silica, magnesia, zirconium silicate, zirconium oxide, chromium oxide , Abrasives such as iron trioxide (Fe ₃ O ₄ ), chromite, graphite, elastic graphite, antimony trisulfide, coke, molybdenum disulfide, tin sulfide, zinc sulfide, iron sulfide, polytetrafluoroethylene (PTFE) Such as lubricants, metal powders such as aluminum, tin, zinc, etc. These can be used alone or in combination of two or more. The content of the friction modifier is preferably 50 to 90% by mass, more preferably 60 to 85% by mass, based on the total amount of the friction material, depending on the desired friction characteristics.

In addition, as the friction adjusting material of the present invention, it is particularly preferable to include an abrasive, and those having a Mohs hardness of 5.5 to 9 are preferable. Examples of the abrasive include chromite, zirconium silicate, zirconium oxide and the like, and the friction material of the present invention includes at least chromite.
The content of chromite in the friction material is 3 to 10% by mass, preferably 3 to 7% by mass. By containing chromite in such a range, the friction coefficient can be controlled.
As the abrasive, chromite may be used alone, or a material other than chromite may be used in combination. Chromite has a Mohs hardness of about 5.5 and is relatively low in grindability. By adjusting the content of chromite, it is possible to suppress the attack of the mating material and contribute to ensuring vibration characteristics.

  The effect of the above-mentioned abrasive becomes even more effective by setting the average particle diameter of each abrasive to a specific range. The average particle size of chromite is preferably 1 to 20 μm, more preferably 5 to 15 μm. If it is 1 μm or more, the grinding effect is exhibited, so that the effect is ensured and the required coefficient of friction can be maintained. Moreover, if it is 20 micrometers or less, a grinding effect | action will not become high too much and it can suppress a partner material attack property. Each average particle diameter is a value (median diameter) measured by a laser diffraction particle size distribution meter.

  In the present invention, known friction adjusting materials other than the above can be appropriately blended as necessary.

As a specific aspect of the manufacturing method of the friction material according to the present invention, it can be performed by a known manufacturing process, for example, the above-mentioned components are blended, and the blend is preformed, thermoformed, according to a normal production method, A friction material can be produced through processes such as heating and polishing.
A general process in manufacturing a brake pad provided with a friction material is shown below.
(A) forming a pressure plate into a predetermined shape by a sheet metal press;
(B) a step of subjecting the pressure plate to a degreasing treatment, a chemical conversion treatment and a primer treatment;
(C) a step of blending raw materials such as a fiber base material, a friction modifier, and a binder, sufficiently homogenizing by stirring, and molding at a predetermined pressure at room temperature to prepare a preform,
(D) A thermoforming process (molding temperature 130 to 180 ° C., molding pressure 30 to 80 MPa) in which the preform and the pressure plate coated with the adhesive are applied to each other by applying a predetermined temperature and pressure. , Molding time 2-10 minutes)
(E) A step of performing aftercure (150 to 300 ° C., 1 to 5 hours) and finally performing finishing treatment such as polishing, surface baking, and painting.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited only to these examples.

(Examples 1-16, Comparative Examples 1-9)
<Production of friction material>
The manufacturing process of the friction material is as follows.
1. Mixing of raw materials The blended raw materials were put all at once into a mixing stirrer and mixed and stirred at room temperature for 5 minutes. In addition, the specific raw material used the raw material shown below. Specific blending ratios are shown in the table. In addition, 7 mass% of brass fibers corresponds to 4.9 mass% in terms of copper element.

2. Production Step Friction materials were produced through steps such as preforming, thermoforming, heating, polishing, etc. for the mixture composed of the above blended materials.
(1) Preliminary molding The above mixture was put into a mold of a preforming press, and molded at room temperature for 10 seconds at 20 MPa at room temperature to prepare a preform.
(2) Thermoforming The preform was put into a thermoforming mold, and a metal plate (pressure plate: P / P) previously coated with an adhesive was stacked thereon and subjected to heat and pressure molding at 150 ° C. and 45 MPa for 5 minutes.
(3) The heat-pressed compact was heat treated at 250 ° C. for 3 hours, and then polished and coated to a predetermined thickness of 16 mm to obtain a friction material. (Pad area: 60 cm ² )

<Evaluation: Friction test>
The following evaluation was implemented using said friction material.
(1) Torque fluctuation amount evaluation a) According to JASO sliding conditions; speed 65 → 0 kph, deceleration 3.5 m / s ² , control temperature 150 ° C. (rotor temperature).
b) Braking conditions: Braking was carried out 10 times at a speed of 130 → 40 kph and a constant hydraulic pressure of 4 MPa.
c) The amount of torque fluctuation during each braking was measured.
(2) Evaluation of compressive strain amount It evaluated based on JISD4413.
(3) Friction coefficient (first fade minimum friction coefficient) / friction material wear amount This was performed according to JASO C406.
(4) Crack resistance It was repeated 5 times that the friction material heated to 300 ° C. was put into water.

The evaluation is performed with ◯, Δ, and ×, and the determination criteria are as shown below.
・ Torque fluctuation (Nm) ○; 200>
Δ: 200-250
×; 250 ≦
・ Compression strain (μm / 2 sheets) ○; 136 ≦
△; 120 ≦ X ≦ 135
×; 120>
・ First Fade Minimum Friction Coefficient ○; 0.26 ≦
Δ; 0.20 ≦ X ≦ 0.25
×; 0.20>
・ Friction material wear amount (mm) ○; 1.2>
Δ: 1.2 to 1.5
×; 1.5 ≦
・ Crack resistance ○: No cracking
×: With crack generation

  Evaluation of the friction material was performed for each evaluation item of torque fluctuation amount, compression strain amount, friction coefficient, friction material wear amount, and crack resistance. As can be seen from the examples and comparative examples, the friction material of the example containing 2 to 7% by mass of elastic graphite, 3 to 10% by mass of chromite, and 3 to 15% by mass of steel fiber at the same time is a criterion for the above evaluation items. Is almost satisfied. However, it was shown that the friction material of the comparative example is below the criterion of either the torque fluctuation amount or the crack resistance.

  The friction material of the present invention is capable of ensuring both vibration characteristics and friction characteristics by blending specific amounts of chromite, steel fiber and elastic graphite as raw materials of the friction material, while maintaining a high friction coefficient, and being resistant to cracking. As well as ensuring the balance of the effect, the friction material suitable for a wide range of vehicles, especially passenger cars, more specifically, the demand for brake pads, brake linings, and clutch facings used in the above-mentioned applications is expected. The

Claims (4)

A friction material comprising a fiber base material, a friction modifier and a binder, wherein the content of at least one copper component selected from copper, a copper alloy and a copper compound is 5% by mass or less in terms of copper element, A friction material comprising 2-7% by mass of elastic graphite as a friction modifier, 3-10% by mass of chromite as the friction modifier, and 3-15% by mass of steel fibers as the fiber base material.   The friction material according to claim 1, wherein the content of the copper component is 0.5% by mass or more in terms of copper element.   The friction material according to claim 2, wherein the copper component is fibrous.   The friction material according to claim 2 or 3, wherein the copper component is at least one of copper fiber and brass fiber.