JP5183902B2 - Non-asbestos friction member - Google Patents

Description

  The present invention relates to a friction member used for brakes of automobiles, railway vehicles, industrial machines, etc., and more particularly to a friction member having both fading characteristics and squeal characteristics. It relates to used brake pads, brake linings, clutch facings, etc.

  Conventionally, a friction material uses a fiber base material, a friction adjusting material, a filler, and a binder, blends them, and is manufactured by a manufacturing process including steps such as preforming, thermoforming, and finishing. However, the use of non-asbestos friction materials has been limited in order to prevent pollution, etc., and the use of powdered materials has been limited for inorganic fillers contained in non-asbestos friction materials. Has increased. For this reason, the friction material tends to have a high hardness and a low porosity. Since the initial friction coefficient depends on the hardness, the friction characteristic is lowered, and since the fade characteristic is dependent on the porosity, these tend to be lowered. In addition to this, noise was easily generated.

  In order to improve the above drawbacks and provide a friction material that does not generate noise or noise during braking, in “Patent Document 1”, a reinforcing fiber, an inorganic and organic filler, and a binder resin are mixed. The friction material raw material is injected into a cavity created between the mold and the pad back plate in multiple layers in the thickness direction of the friction material, and the raw material for the adhesive layer in contact with the back plate is granulated. A disk brake consisting of a laminated structure consisting of an adhesive layer with a low porosity and a base material layer with a high porosity. Manufactures pads. As a result, it is described that the rust generation of the back plate is prevented, the adhesive strength is increased, the interlayer strength of the friction material is also improved, and a highly reliable disc brake pad can be obtained.

In “Patent Document 2”, a friction material containing 5 to 30% by volume of a granulated material composed of a binder and inorganic fibers having an average particle diameter of 2.5 to 11 mm with respect to the friction material composition is fade-resistant. He states that it has excellent characteristics and that it makes almost no noise or abnormal noise during braking.
In addition, “Patent Document 3” describes a granulated product composed of a binder, an inorganic fiber, and rubber powder such as NBR and SBR having an average particle diameter of 2.5 to 11 mm with respect to the friction material composition. It has been reported that the same effect can be obtained when the blending amount is the same as “2”.

Further, "Patent Document 4" describes a friction material containing 10 to 50% by weight of metal fiber whose surface is coated with one or more types of elastomers among butyl rubber, silicon rubber, and fluorine rubber. When the elastomer is blended in an amount of 2 to 15 parts by weight with respect to 100 parts by weight of the metal fiber, the metal fiber is less likely to fall off and segregate, suppresses the oxidative deterioration of the metal fiber, and has noise performance and wear resistance. Used as an excellent friction material.
However, in any case, it has been difficult to satisfy the target performance necessary for the friction material such as squealing characteristics, wear resistance, and fading characteristics in a balanced manner.
Japanese Patent Laid-Open No. 7-301265 Japanese Patent Laid-Open No. 10-226782 Japanese Patent Laid-Open No. 10-226783 JP 2002-309234 A

  With respect to vehicle brakes, as a measure for reducing unsprung loads in order to improve fuel efficiency and handling characteristics, there is a demand for reducing the size of the brake including the system. On the other hand, for downsizing, it is necessary to increase the braking effectiveness level (the friction material effectiveness level). However, increasing the brake effectiveness level (the friction material effectiveness level) tends to increase the grindability, and generally tends to cause squeal and judder characteristics to deteriorate. It is difficult to achieve both merchandise and sexiness. In order to improve it, an improvement effect can be obtained by blending a rubber-based material, but if blended, the heat resistance as a friction material is lowered, leading to high speed, high temperature effect, and fade resistance.

Further, in recent years, as the friction material has become non-asbestos, the use ratio of the inorganic filler has increased. As a result, there has been a problem that it is difficult to obtain a molded product having desired properties with respect to characteristics such as friction performance.
In fact, many non-asbestos friction materials are used for both disc brakes and drum brakes. However, one of the problems is that unpleasant noise called squeal is generated during braking.
The cause of squeal is thought to be mainly due to frictional vibration between the friction material and the disk rotor and drum during brake braking. To prevent this squeal, a composition with good vibration characteristics is used as one of the friction materials. Although the composite friction material provided in the part and the friction material with the hardness distribution on the surface of the friction material devised to make the friction distribution difficult to cause friction vibration are considered, there are problems such as high manufacturing cost.
Therefore, the problem to be solved by the present invention is to provide a non-asbestos friction material having good squealing and abnormal noise characteristics without impairing the performance of the friction material itself such as friction wear performance in the non-asbestos friction material. It is.

The present invention has solved the above problems by the following means.
(1) In a non-asbestos friction member in which a friction material including a thermosetting resin binder, a reinforcing fiber, and a friction modifier and a pressure plate are bonded, the friction material has a thickness portion from the bonding surface to an effective wear allowance. A non-asbestos friction member characterized by further containing 30 to 40 vol% of premix particles obtained by heating and stirring a material containing an elastomer and a crosslinking agent.
(2) The non-asbestos friction member according to (1), wherein the premix particles are obtained by heating and stirring a material containing an elastomer, a crosslinking agent, and reinforcing fibers.
(3) The non-asbestos friction member according to (1) or (2), wherein the premix particles contain 10 to 97 vol% of an elastomer.
(4) A friction material material in which premix particles obtained by heating and stirring a material containing an elastomer and a crosslinking agent are mixed with a friction material containing a thermosetting resin binder, a reinforcing fiber, and a friction modifier, The method for producing a non-asbestos friction member according to (1), wherein the friction material raw material not containing the mixed particles is laminated on a mold and preformed, followed by heat treatment.

  Without changing the characteristics of the friction material itself by providing a layer containing the premix in addition to the material of the friction material only on the adhesive surface on the pressure plate side of the friction material and the thickness portion up to the effective wear allowance of the friction material, Since the flexibility of the friction material can be increased, it is possible to obtain a friction member having good noise and abnormal noise characteristics.

Hereinafter, the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the friction member of the present invention has an adhesive surface (adhesive layer) 3 on the side in contact with the pressure plate 2, and the friction material 6 includes a premix-containing portion 7 and an effective wear allowance 5. In contrast, a conventional standard friction member has a structure in which a friction material 6 is provided on an adhesive surface (adhesive layer) 3.
In general, the friction material is manufactured through each step of finishing processing such as blending of friction material, stirring, preforming at room temperature, thermoforming, heating (after-cure), and polishing. In the thermoforming process, the binding material is cured by a reaction by heat, so that the entire friction material is firmly bonded and integrated to have strength and hardness. The heating (after cure) conditions also affect the quality of the friction material. A novolak-type phenol resin (including various modified types) is generally used as a binder for the friction material, and hexamethylenetetramine or the like is added and mixed as a curing agent. This curing agent is added together with the novolac type phenolic resin as a binder in a powder state when the friction material is blended. A resol type phenol resin is also used.

  A friction material used for a disc brake pad or the like always generates heat and becomes high temperature in order to change kinetic energy into heat energy. Accordingly, such a friction material is required not only to have heat resistance, wear resistance, etc., but also to have stable friction characteristics with little change in the coefficient of friction even when the temperature changes. Furthermore, it is necessary that noise (squeal) and judder are not generated, and the friction material is required to satisfy target performances over a number of items.

  The friction material is integrally bonded to the pressure plate and used as a disc brake pad. This bonding is conventionally performed by applying an adhesive to a pressure plate and thermoforming it, and thermosetting resin adhesives such as phenolic resins and epoxy resins, or crosslinkable rubber adhesives are used. ing. In addition, this adhesive is strongly bonded simultaneously with the molding of the friction material by press-molding the preformed friction material together with the pressure plate.

  In the present invention, in the friction material of the friction member, only the thickness portion from the adhesive surface 3 (adhesive surface on the pressure plate side) to the effective wear allowance 5 is added to the pre-mix 4 (rubber, fiber, It is characterized by a non-asbestos-based pad material containing 2-40 vol%, preferably 20-40 vol%, of a composite such as graphite. The thickness of the premix-containing portion 7 is 1 to 6 mm, and is preferably in the range of 1 to 2 mm from the same adhesive surface 2 as the effective wear allowance 5 of the friction material 6.

The constituent materials of the premix used in the present invention are an elastomer and a cross-linking agent, and can further contain fibers, and general materials used for friction materials can be used.
The premix is based on silicon rubber, butyl rubber, chlorobutyl rubber, NBR rubber, etc., and elastomers such as olefin, vinyl chloride, styrene, polyester, and fibers such as steel fiber, aramid fiber, cellulose fiber, and acrylic fiber. , Graphite and the like, sulfur, and a cross-linking agent, which are manufactured with a stirrer such as a kneader or a Banbury mixer. When an aramid fiber is used, those having an average diameter of 1 to 50 μm and an average length of about 0.5 to 5 mm are preferable. As the crosslinking agent, a substance that gives a crosslinked structure by reaction with respect to the elastomer is used. In the case of rubber, a vulcanization accelerator is used, and as the vulcanization accelerator, thiazole-based MBT, MBTS, ZmMBT, thiuram, and the like. Compounds such as TMTM, TMTD, and TETD (all abbreviations) of the system can be used. The content of the base elastomer, such as rubber, is 10 to 97% by volume, preferably 20 to 50% by volume. The fiber content is 1 to 90% by volume, preferably 3 to 70% by volume. The content of the vulcanization accelerator is 0.1 to 10% by volume, preferably 0.5 to 5% by volume. The average particle size of the premix used in the present invention is 0.1 to 8 mm, preferably 0.5 to 4 mm.

  The premix used in the present invention can be granulated by a conventional method, cured by heat treatment and granulated, and granulated particles using a normal granulator such as a compression mold, a mixing mold, an extrusion mold, etc. Can be When the amount of rubber is adjusted during granulation, fluidity during granulation of the compounding material can be improved by melting the rubber. Moreover, the particle size of the granulated particles may be made uniform by sieving after granulation.

The friction material raw material used in the present invention is a fiber component, a binder, a friction modifier, or the like as a base material that is usually used, and is a non-asbestos raw material.
The fiber component that is the base material of the friction material includes metal fibers such as steel fibers, copper fibers, and brass fibers; aromatic polyamide fibers (aramid pulp, etc .: commercially available products such as DuPont's brand name Kevlar), acrylic Examples thereof include organic fibers such as fibers, cellulose fibers, and flame-resistant acrylic fibers; non-asbestos inorganic fibers such as potassium titanate fibers, glass fibers, alumina fibers, carbon fibers, and rock wool. One or a combination of two or more of these can be used.

Examples of the binder include thermosetting resins such as phenol resins, urea resins, melamine resins, or modified resins thereof.
Examples of friction modifiers include organic dust such as cashew dust, rubber dust, and melamine dust; fillers such as calcium carbonate, barium sulfate, and calcium hydroxide; grinding of metal oxides such as magnesia, alumina, and zirconia Materials: Metal powders such as aluminum powder, copper powder and zinc powder, lubricants such as graphite and molybdenum disulfide, etc. are used, and one or a combination of two or more selected from these is used as a filler. be able to.

  Further, in the friction material of the present invention, the components of the low steel friction material are phenol resin, steel fiber, aramid fiber, cellulose fiber, calcium carbonate, barium sulfate, mica, metal powder, sulfide, graphite, organic dust, alumina, It consists of magnesia, minerals, iron oxide, etc.

  Although the outline of the manufacturing process of the non-asbestos friction material according to the present invention has already been described, it was formed into a predetermined shape by a sheet metal press as in the conventional method, subjected to degreasing treatment and primer treatment, and an adhesive was applied. A raw material that is sufficiently homogenized by stirring by mixing a pressure plate, reinforcing fibers such as heat-resistant organic fibers and metal fibers, and powder materials such as inorganic and organic fillers, friction modifiers, and thermosetting resin binders. A preform formed by molding (preliminary molding) at room temperature at a predetermined pressure is thermoformed at a predetermined temperature and pressure in the thermoforming process, or the preforming process is omitted and the agitating material is added to the thermoforming mold. Is directly injected and thermoformed to fix both members together, after-curing, and finally finishing.

  In the manufacturing process of the friction material of the present invention, formation of the friction material comprising the effective wear allowance and the premix-containing portion can be performed by a general manufacturing method. In other words, prepare a raw material with a predetermined amount of premix mixed in the friction material component and agitate, and a raw material with only the friction material component agitated. The same manufacturing method as a friction material having a normal adhesive layer to be preformed can be employed.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, the scope of the present invention is not limited by these Examples.

(Examples 1-4, Reference Examples 1-2 and Comparative Examples 1-2)
Table 1 shows the formulation of nine types of premixes used in the premix-containing part of the present invention. Specifically, the blending ratios of chlorobutyl rubber, silicon rubber, NBR rubber, steel fiber, aramid fiber, cellulose fiber, filler and vulcanization accelerator are changed, and the mixture is heated and stirred with a kneader, and the average particle size is about 0.00. A granulated heat treatment was performed on 5 to 4 mm irregular shaped particles.

(Create brake pads)
According to the formulation shown in Table 2, the prepared mixture was preliminarily molded by pressing at room temperature and 20 MPa for 1 minute. Next, a premix-containing compound and a friction material compound serving as an effective friction allowance are sequentially set in a thermoforming mold together with a pressure plate subjected to primer treatment and coated with a phenol resin adhesive, and 20-80 MPa, Thermoformed at a temperature of 100 to 170 ° C. for 1 to 10 minutes. And heat processing was performed at 200-400 degreeC for 20-200 minutes, and the brake pad was created. In that case, the thickness of the premix containing part of this invention is 1 mm and 2 mm.
Table 2 shows the formulation of the friction material containing the premix of the present invention and the test results of the friction material. The friction material is a low steel friction material, and the blending ratio of various blending materials is as follows. For the friction materials of Reference Examples 1-2 and Examples 1-3 , Premix Formulation Example 3 was used, and for Example 4 , Premix Formulation Example 9 was used. Comparative Example 1 is a standard friction material to which no premix is added as shown in FIG. 2, and Comparative Example 2 is a friction material in which a premix is uniformly added as shown in FIG.

Mixing ratio of low steel friction material (Example) (vol%)
Phenolic resin: 20
Calcium carbonate: 10
Barium sulfate: 10
Cashew dust: 5
Graphite: 20
Alumina: 5
Aramid fiber: 5
Steel fiber: 20
Copper: 5

(Evaluation of friction material)
The friction performance and physical property values of the 8 types of brake pads prepared were measured. The measurement results are shown in Table 2. In Table 2, abnormal noise was evaluated for the presence or absence of abnormal noise by a noise test.
X: Bad Δ: Near the target ○: Good The friction coefficient was measured according to JASO C406. The shear strength was measured according to JASO C427 at 20 ° C. The compressive deformation was measured according to AK-Standard (displacement amount corresponding to a hydraulic pressure of 100 bar).
From the above evaluation results, the premix compounding amount in the premix part in the vicinity of the adhesive surface is appropriately 20 to 40 vol% based on the balance of shear strength, compression deformation and friction characteristics.

  According to the present invention, a friction member that suppresses the occurrence of squeal and abnormal noise and has both fade characteristics and wear resistance has been put to practical use. Therefore, the friction material of the present invention is particularly useful for brake pads, brake linings, clutch facings and the like used for industrial machines, railway vehicles, luggage vehicles, passenger cars and the like.

It is sectional drawing which shows the outline of the layer structure of the friction member of this invention. It is sectional drawing of the standard friction member which consists of a friction layer independent. It is sectional drawing of the friction member for a comparison which shows that the premix is mix | blended with the whole friction layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Friction member 2 Pressure plate 3 Adhesive surface 4 Premix 5 Effective wear allowance 6 Friction material 7 Premix containing part

Claims (4)

In a non-asbestos friction member in which a friction material including a thermosetting resin binder, a reinforcing fiber, and a friction modifier and a pressure plate are bonded, the friction material is an elastomer in a thickness portion from the bonding surface to an effective wear allowance. And 30-40 vol% of premix particles obtained by heating and stirring the material containing the crosslinking agent, and a non-asbestos friction member.   The non-asbestos friction member according to claim 1, wherein the premix particles are obtained by heating and stirring a material containing an elastomer, a crosslinking agent and a reinforcing fiber.   The non-asbestos friction member according to claim 1 or 2, wherein the premix particles contain 10 to 97 vol% of an elastomer.   A friction material raw material obtained by mixing premix particles obtained by heating and stirring a material containing an elastomer and a crosslinking agent with a friction material containing a thermosetting resin binder, a reinforcing fiber, and a friction modifier, and the premix particles 2. The method for producing a non-asbestos friction member according to claim 1, wherein a non-mixed friction material is laminated on a mold and preformed, followed by heat treatment.

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