DE112010001176T5 - friction pair - Google Patents

Abstract

A friction pair which generates a friction force by means of mutual sliding friction comprises: a first friction material (1) containing first hard particles (11) and a resin (12) with a lower Mohs hardness than the first hard particles (11); and a second friction material (2) containing second hard particles (21) and either a metallic material or an inorganic material (24) having a lower Mohs hardness than the second hard particles (21) and a higher Mohs hardness than the resin (12) . The resin (12) of the first friction material (1) surrounds the entire surface of the first hard particles (11), and the metallic material or inorganic material (24) of the second friction material (2) forms a matrix in which the second hard particles ( 21) are embedded.

Description

BACKGROUND OF THE INVENTION

1. Field of the invention

The invention relates to a friction pair which exhibits satisfactory wear resistance as well as satisfactory noise characteristics, vibration characteristics and braking characteristics.

2. Description of the Related Art

Brake pads, brake pads, clutch linings, and other friction materials used in industrial machinery, rail vehicles, freight vehicles, automobiles, and the like, must have high reliability and increasingly higher performance to ensure safety. In particular, since friction materials convert kinetic energy into heat by friction, they must have sufficient heat resistance to the frictional heat generated during braking. From the point of view of running stability, the friction materials must also exhibit frictional properties which remain constant with changes in temperature and weather conditions, which over a long period of time have superior wear resistance with little change in properties and which produce no noise such as squealing during braking or vehicle vibration. In particular, in view of the product value and smoothness of vehicles, noises and vibrations attributable to friction vibrations of the friction material are an important technical problem.

To meet these requirements, friction materials are generally formed by combining a plurality of types of components. For example, various combinations of fiber base materials are used to maintain the shape of the friction material, binders that bind components such as fiber bases, and fillers to adjust various properties of the friction materials (such as adjustment and stabilization of wear resistance, heat resistance or coefficient of friction). Friction materials are made by curing a raw material mixture obtained by mixing these ingredients with a mixer by hot pressing, followed by molding, grinding and sizing if necessary. Into the friction material are mixed hard particles of high hardness, which highly effectively increase the friction coefficient of the friction material to improve the braking properties of the friction material. Although the braking properties can be improved by increasing the amount of hard particles, the counter material can suffer from wear by the hard particles. Local wear caused by the hard particles results in uneven wear of the friction surface of the mating material while abrasion from the worn mating material may remain on the friction surface, thereby exacerbating the wear of the friction surfaces of the friction couple. This allows the friction material to have less wear resistance, while more likely to cause noise and vibration. It is therefore difficult to maintain good braking properties in a friction material, while ensuring excellent wear resistance, noise characteristics and vibration characteristics.

In order to solve the above problems, Japanese Patent Application Laid-Open 2003-268352 ( JP 2003-268352 A ) a friction material containing substrate fibers, a binder and a friction modifier. The friction modifier contains a highly elastic abrasive material composed of porous hard particles and a highly elastic substance fixed in the pores of the porous hard particles.

The in the JP 2003-268352 A described invention refers to one of the friction materials, which forms a friction pair. However, the braking characteristics and wear resistance of a friction material are determined by the combination of materials in the friction pair that forms the friction surface. It is therefore difficult to achieve a friction pair which fully achieves the intended performance by merely improving the properties of one of the friction materials constituting the friction pair. Thus, a friction material having excellent wear resistance and excellent noise characteristics, vibration characteristics and braking properties can be achieved by a material design concentrating on the friction surfaces of a first friction material as well as a second friction material forming the friction pair. The design of only one of the friction materials necessitates a separate design of a counter friction material that matches the former friction material in a process that requires trial and error for repeated prototype design and evaluation. Therefore, the common design of the Friction materials that form a pair of friction, save the cost and time of developing a pair of friction, and make it possible to predict the resulting gains in the performance of the friction pair.

BRIEF SUMMARY OF THE INVENTION

The invention provides a friction pair having wear resistance, noise characteristics, vibration characteristics and braking characteristics.

A friction pair according to a first aspect of the invention generates frictional force by means of mutual sliding friction and comprises: a first friction material containing first hard particles and a resin having lower Mohs hardness than the first hard particles, the resin surrounding the entire surface of the first hard particles; and a second friction material containing the second hard particle and either a metallic material or an inorganic material having a lower Mohs hardness than the second hard particles and having a higher Mohs hardness than the resin, the metallic material or the inorganic material forming a matrix of the second friction material, in which the second hard particles are embedded.

The friction pair has a stress distribution mechanism by which, even when a stress acts on the friction pair, the stress applied to the first hard particles or the second hard particles is sufficiently absorbed by the resin, the metallic material or the inorganic material. As a result, the first hard particles or the second hard particles are less likely to be exposed to stress beyond the yield stress. Therefore, the frictional pair can generate a high frictional force by means of the first hard particles and the second hard particles while achieving excellent friction force stability and suppression of noise and vibration.

• 1. Das erste Reibmaterial enthält außerdem erste anorganische Teilchen mit eiMohshärtner geringeren e als die ersten harten Teilchen, und ein erstes Verhältnis r_c/r_f des mittleren Durchmessers r_c der harzbeschichteten harten Teilchen bezüglich des mittleren Durchmessers r_f der ersten anorganischen Teilchen beträgt mindestens 0,2;
• 2. das zweite Reibmaterial enthält außerdem zweite anorganische Teilchen mit ärteiner geringeren Mohshe als die zweiten harten Teilchen, und ein zweites Verhältnis R_A/R_F des mittleren Durchmessers R_A der zweiten harten Teilchen bezüglich des mittleren Durchmessers R_F der zweiten anorganischen Teilchen beträgt mindestens 0,2;
• 3. das erste Reibmaterial erfüllt die unten stehende Formel (1); und
• 4. das erste Reibmaterial und das zweite Reibmaterial erfüllen die unten stehende Formel (2).

In the above friction pair, the first friction material may further include an elastic material that forms a matrix of the first friction material in which the resin-coated hard particles in which the first hard particles are coated by the resin are embedded. The friction pair may also meet at least one of the following first to fourth conditions:

• 1. The first friction material also contains first inorganic particles having harder than the first hard particles, and a first ratio r _c / r _{f of} the average diameter r _{c of} the resin-coated hard particles with respect to the mean diameter r _{f of} the first inorganic particles is at least 0.2;
• 2. the second friction material also includes second inorganic particles having ärteiner lower Mohshe than the second hard particles, and a second ratio R _A / R _F of the average diameter R _A of the second hard particles is relative to the mean diameter R _F of the second inorganic particles at least 0.2;
• 3. the first friction material satisfies the formula (1) below; and
• 4. The first friction material and the second friction material satisfy the formula (2) below.

• In the formula (1), s is the average layer thickness of the resin in the resin-coated hard particles, E _b is the elastic modulus of the resin, E _m is the elastic modulus of the elastic material, and r _a is the mean diameter of the first hard particles, where E _m > E _b applies.

In the formula (2), C _{a is} the concentration (vol%) of the first hard particles in the first friction material, C _A is the concentration (vol%) of the second hard particles in the second friction material, r _a is the mean diameter of the first hard particles in the first friction material, R _A is the mean diameter of the second hard particles in the second friction material, σ ₁ is the yield stress of the first friction material, and σ ₂ is the yield stress of the second friction material, where σ ₁ = 10 to 100 MPa, σ ₂ = 100 to 800 MPa and C _A = 0.1 to 95 vol .-% applies.

In a friction pair having the above features, the elastic material in the first friction material ensures that the entire friction surfaces of the friction materials contact each other. This makes it possible to generate a friction force between the entire friction surfaces. When the friction pair having the above features satisfies the first condition, the first ratio r _c / r _{f is} at least 0.2. Thereby, a compressive stress generated in the first friction material also acts on the resin-coated hard particles, whereby even when the resin-coated hard particles are in the middle of a close-packed structure, the stress is uniformly transmitted throughout the first friction material is formed by four first inorganic particles. When the friction pair having the above features satisfies the second condition, the second ratio R _A / R _{F is} at least 0.2. Thereby, a compressive stress generated in the second friction material also acts on the hard particles, whereby a stress is transmitted evenly over the entire second friction material even if the second hard particles are in the middle of a densely packed structure, which four second inorganic particles is formed. In addition, when the friction pair having the above features satisfies the third condition, the stress concentrates by setting an appropriate coating thickness s in the first hard particles. In addition, if the friction pair having the above features satisfies the fourth condition, the occurrence of flow in the first hard particles and the second hard particles can be suppressed.

The friction pair can also fulfill all of the first to fourth conditions.

In the above friction pair, the first hard particles and / or the second hard particles may have a Mohs hardness of at least 4.5.

A friction pair having the above features can achieve even higher friction forces while achieving excellent friction force stability and noise and vibration suppression. A friction pair having the above features uses hard particles that have a high yield stress. As a result, the flow in the hard particles is not easy to flow, since the stress acting on the first and second friction materials causes only a displacement of the constituents surrounding the hard particles on the outermost surface of the materials. This reduces wear and improves the wear resistance of the friction materials.

The above friction pair may satisfy the third condition, wherein the elastic modulus E _{b of} the resin may be at least 1 GPa.

In the friction pair described above, a resin having a sufficient modulus of elasticity prevents the first hard particles from peeling off the first friction material when the first friction material is rubbed. In addition, the friction pair reaches a more suitable stress to which the first hard particles are exposed and a more suitable protrusion amount of the first hard particles from the first friction surface. The friction pair also suppresses the occurrence of flow in the first hard particles.

In the above friction pair, the resin may contain at least one non-crystalline resin selected from the group consisting of polyimides, polyamide-imides, polycarbonates, polyphenylene ethers, polyallylates, polysulfones and polyethersulfones.

The selection of a suitable non-crystalline resin results in an even more suitable stress to which the first hard particles are exposed and a still more suitable amount of protrusion of the first hard particles from the first friction surface.

The above friction pair may satisfy the first condition and / or the second condition, and the first inorganic particles and / or the second inorganic particles may have a Mohs hardness of not more than four.

The friction pair having the above features uses the first inorganic particles and / or the second inorganic particles having a low yield stress. Therefore, the first hard particles and / or the second hard particles do not break in the resin-coated hard particles when the first and second friction materials are subjected to stress. This makes it possible to reduce the wear in the friction materials and to achieve a desired wear resistance.

The above friction pair may satisfy the third condition, and the elastic modulus E _{m of} the elastic material may be at least 1 GPa.

In the friction pair having the above features, an elastic material having a sufficient elastic modulus reaches a more suitable stress to which the first hard particles are exposed and a more suitable protrusion amount of the first hard particles from the first friction surface.

The elastic material may contain at least one resin selected from the group consisting of phenol resins, modified phenolic resins, amino resins, furan resins, unsaturated polyester resins, diallyl phthalate resins, alkyd resins, epoxy resins, thermosetting polyamideimide resins, thermosetting polyimide resins, and silicone resins.

In the friction pair having the above features, the selection of a suitable elastic material achieves a more suitable stress to which the first hard particles are exposed and a more suitable protrusion amount of the first hard particles from the first friction surface.

The above friction pair may satisfy the first condition and / or the second condition, and the first ratio r _c / r _f and / or the second ratio R _A / R _F may be at least 0.3. Alternatively, both the first condition and the second condition may be satisfied, and both the first ratio and the second ratio may be 0.3 or more.

The friction pair having the above features allows at least one of the following effects. At a first ratio of at least 0.3, in the resin-coated hard particles, even when the resin-coated hard particles are in the middle of a close-packed structure formed by four first inorganic particles, stress can be more reliably generated when in the first friction material, a compressive stress occurs. At a second ratio of at least 0.3, in the second hard particles, even when the second hard particles are in the middle of a close-packed structure formed of four second inorganic particles, stress can be more reliably generated when in the second friction material, a compressive stress occurs.

The first friction material may contain a total of at least 5% by volume of the resin-coated hard particles and the elastic material, and the volume ratio of the resin-coated hard particles to the elastic material may range from 2: 1 to 1:50.

In the friction pair having the above features, excellent friction force stability and noise and vibration suppression can be achieved when the first friction material contains the resin-coated hard particles and the elastic material in more suitable amounts. In the above-described friction pair, moreover, excellent friction force stability and noise and vibration suppression can be achieved when the volume ratio of the resin-coated hard particles and the elastic material falls within an appropriate range.

In the above friction pair, the elastic modulus of the first friction material may be 100 to 300 MPa.

The friction pair having the above features prevents the first hard particles from falling off the first friction material under friction. In addition, the friction pair reaches a more suitable stress to which the first hard particles are exposed and a more suitable protrusion amount of the first hard particles from the first friction surface. The friction pair having the above features can also suppress the occurrence of flow in the first hard particles.

In the above friction pair, the surface roughness of the friction surface of the second friction material may be not more than 10 μm.

The friction pair having the above features allows a good first braking and makes it possible to suppress frictional force variations and wear increases.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, advantages and technical and industrial significance of this invention will be described with reference to the accompanying drawings, in which like numerals denote like elements, with reference to the following detailed description of exemplary embodiments of the invention. Show it:

1 12 is a schematic diagram illustrating resin-coated hard particles that occupy the voids in a first friction material in a close-packed structure formed of inorganic particles;

2 a graph schematically illustrating a range defined by the condition (4), wherein the X-axis (r _a / R _A ) represents ² and represents the Y-axis (C _a / C _A );

3 a diagram illustrating a typical example of a friction pair of the invention;

4A and 4B schematic sectional views illustrating typical examples of a friction pair before and after voltage application; and

5 12 is a schematic sectional view illustrating comparatively situations before and after the occurrence of strain in resin-coated hard particles (c) on a friction surface portion and in an elastic material (m) constituting the matrix of a friction material when a stress acts on the friction material.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A friction pair according to a first aspect of the invention generates frictional force by means of mutual sliding friction and comprises a first friction material containing hard particles (a) and a resin (b) surrounding the entire surface of the hard particles (a); and a second friction material containing hard particles (A) and either a metallic material or an inorganic material (M) forming a matrix of the second friction material in which the hard particles (A) are embedded. The resin (b) of the first friction material has a lower Mohs hardness than the hard particles (a), and the metallic or inorganic material (M) of the second friction material has a lower Mohs hardness than the hard particles (A) and a higher Mohs hardness than the resin (b).

• (1) Das erste Reibmaterial enthält außerdem anorganische Teilchen (f) mit einer ärtgeringeren Mohshe als die harten Teilchen (a), und ein Verhältnis r_c/r_f des mittleren Durchmessers r_c der harzbeschichteten harten Teilchen (c) bezüglich des mittleren Durchmessers r_f der anorganischen Teilchen (f) beträgt mindestens 0,2.
• (2) Das zweite Reibmaterial enthält außerdem anorganische Teilchen (F) mit eiMohshärtner geringeren e als die harten Teilchen (A), und ein Verhältnis R_A/R_F des mittleren Durchmessers R_A der harten Teilchen (A) bezüglich des mittleren Durchmessers R_F der anorganischen Teilchen (F) beträgt mindestens 0,2.
• (3) Das erste Reibmaterial erfüllt die unten stehende Formel (1).
• (4) Das erste Reibmaterial und das zweite Reibmaterial erfüllen die unten stehende Formel (2).
  

In an example of a friction pair specifically implementing the first aspect of the invention, the first friction material preferably contains resin-coated hard particles (c) in which the resin (b) coats the hard particles (a) and an elastic material (m). which forms the matrix of the first friction material in which the resin-coated particles are embedded; and the second friction material contains the hard particles (A) and either the metallic material or the inorganic material (B) (hereinafter called "matrix material") forming the matrix of the second friction material, the friction pair having at least one of the following conditions (1 ) to (4).

• (1) The first friction material further contains inorganic particles (f) with a ärtgeringeren Mohshe than the hard particles (a), and a ratio r _c / r _f of the average diameter r _c of the resin-coated hard particles (c) r with respect to the average diameter _{f of} the inorganic particles (f) is at least 0.2.
• (2) The second friction material further contains inorganic particles (F) with eiMohshärtner lower e as the hard particles (A), and a ratio R _A / R _F of the average diameter R _A of the hard particles (A) with respect to the mean diameter R _F the inorganic particle (F) is at least 0.2.
• (3) The first friction material satisfies the formula (1) below.
• (4) The first friction material and the second friction material satisfy the formula (2) below.
  

In the formula (1), s is the average layer thickness of the resin (b) in the resin-coated hard particles (c), E _b is the elastic modulus of the resin (b), E _m is the elastic modulus of the elastic material (m), and r _a is the mean diameter of the hard particles (a), where E _m > E _b .

In the formula (2), C _{a is} the concentration (vol%) of the hard particles (a) in the first friction material, C _A is the concentration (vol%) of the hard particles (A) in the second friction material, r _a is the mean diameter of the hard particles (a) in the first friction material, R _A is the mean diameter of the hard particles (A) in the second friction material, σ ₁ is the yield stress of the first friction material, and σ ₂ is the Yield stress of the second friction material, where σ ₁ = 10 to 100 MPa, σ ₂ = 100 to 800 MPa and C _A = 0.1 to 95 vol .-% applies.

The friction pair comprises a first friction material and a second friction material. Special applications of the friction pair include z. B. disc brakes, wherein the friction pair has a brake pad as the first friction material and a disc as the second friction material.

The "Mohs hardness" is a typical hardness index to express the hardness of minerals, ranging from 10 for diamond to 1 for talc.

The hardness and hardness ratios of the hard particles in the friction materials, the average diameter and the ratios of the mean diameters of the hard particles, and the amounts and ratios of addition amounts of the hard particles have not been scientifically treated in conventional friction pairs. Therefore, regardless of the frictional force of the friction material, the problems of wear resistance and noise and vibration suppression have persisted. Conversely, no matter how high the wear resistance and the noise and vibration suppression effect of the friction pair is, a friction pair failing to produce a high frictional force can be obtained. It has therefore been difficult to simultaneously achieve friction resistance and noise and vibration suppression while maintaining a high frictional force.

Hard particles are an important component to increase the friction coefficient of the friction surface and to ensure the braking properties of the friction material. The hard particles have a yield stress, and therefore the hard particles do not easily flow when the friction materials are subjected to stress.

The hardness of the hard particles can lead to excessive wear in the counter material. If the counter material also contains hard particles, the hard particles in one of the friction materials are rubbed alternately and intermittently against the hard particles and the other components than the hard particles in the counter material. This can cause a friction fluctuation of the friction pair. Or the friction between the hard particles may break the hard particles in at least one of the materials. In turn, the broken hard particles remaining on the friction surface may promote wear in the friction material and / or the counter material.

Therefore, when a friction material is developed by itself as in conventional friction materials, it is not enough to simultaneously achieve wear resistance and noise and vibration suppression while maintaining a high frictional force. Instead, in a friction pair, friction materials must be designed as material combinations, and in the respective friction materials, the composition ratios of hard particles and so on must be controlled.

A friction pair according to a first aspect of the invention comprises a first friction material and a second friction material, each having hard particles and an elastic material other than the hard particles. In addition, the friction pair has employed a stress distribution mechanism and a material design technique which prevent the hard particles from being exposed to stress beyond the yield stress.

The use of such a stress distribution mechanism and method of material design limits local fractures in the elastic material of the friction material different from the hard particles, so that the outermost surface layer of the friction material is stretched, making it less likely that local fractures will spread into the friction material. Thus, a suitable wear resistance and a suitable noise and vibration suppression can be achieved while maintaining a high frictional force.

Namely, the above stress distribution mechanism is a dynamic mechanism in which the supernatant amount of the hard particles from the friction surface is sufficiently reduced by the deformation of the elastic material in each friction material surrounding the hard particles. When hard particles protrude from the friction surface, the friction between hard particles takes place not only between the tips of the protruding portions in the first and second friction materials but also in portions other than the tips of the protruding portions. Therefore, significant wear can not be avoided, no matter how consistent the hard particles are against wear. The stress distribution mechanism described above solves this problem. The described mechanism controls the Stress acting on the respective hard particles in the first and second friction materials so that the hard particles are not subjected to stress beyond the yield stress and so that the hard particles rub against each other only at the tip of the protruding portion. This makes it possible to simultaneously improve the wear resistance and the noise and vibration suppression, while maintaining a high frictional force.

Namely, the above material designing method is a scientific method that involves adjusting the average diameters, blending amounts, moduli of elasticity and so on of the hard particles and the elastic materials other than the hard particles and other materials existing in the respective friction materials. While the above-described stress distribution mechanism solves the problems described above, the mechanism itself is trial and error with respect to repeated prototype design and evaluation of friction pairs, while the gain in performance enabled by the mechanism is difficult to predict. The development of a friction pair with an optimal combination of friction materials then becomes a time consuming task. The development time of friction pairs can be shortened, and the gain in friction pair performance can be predicted by scientifically designing various parameters such as the average diameters, mixing amounts, elastic moduli, etc. of the respective materials present in the first and second friction materials.

In a concrete example of a friction pair provided with the above-described stress distribution mechanism and designed in accordance with the material designing method described above, the friction pair comprises a first friction material comprising resin-coated hard particles (c) in which hard particles (a) are coated with a Resin (b) are coated, and containing an elastic material (m) other than the resin-coated hard particles, which forms the matrix of the first friction material; and a second friction material containing hard particles (A) and a matrix material (M), wherein the friction material satisfies at least one of the conditions (1) to (4) described below. The hard particles (A) in the second friction material may also be resin-coated.

Further, in condition (1), the first friction material contains inorganic particles having a lower Mohs hardness than the first hard particles, and a first ratio r _c / r _{f of} the average diameter r _{c of} the resin-coated hard particles with respect to the mean diameter r _{f of} the first inorganic one Particle is at least 0.2 ". In condition (2) "also includes the second friction material of second inorganic particles having a lesser Mohs hardness than the second hard particles, and a second ratio R _A / R _F of the average diameter R _A of the second hard particles with respect to the mean diameter R _F of the second inorganic particles is at least 0.2 ",

1 FIG. 12 is a schematic diagram illustrating resin-coated hard particles occupying the voids in a close-packed structure formed of inorganic particles in a first friction material. FIG. Inorganic particles (f) 61 drawn as solid lines and inorganic particles (f) 62 , which are drawn as dotted lines and are closer to the paper front than the former, form a densely packed structure. The resin-coated hard particles (c) 63 prove the gaps in the densely packed structure. It is believed that the inorganic particles 61 and 62 and the resin-coated hard particle 63 are spherical. In 1 is the inorganic particle 62 translucent to the resin-coated hard particle 63 to show.

When the resin-coated hard particles 63 exactly fit into the gaps of the densely packed structure (in the tetrahedral gaps), the diameter of the resin-coated hard particles is 63 0.225 r _f ≈ 0.2 r _f , where r _{f is} the diameter of the inorganic particles (f) 61 and 62 is. If the resin-coated hard particles 63 therefore, have a diameter equal to or greater than the above, that is, when the ratio of r _c with respect to r _f (r _c / r _f ) is equal to or greater than 0.2, where r _{c is} the diameter of Resin-coated hard particles (c), any compressive stress acting in the first friction material acts not only to the inorganic particles (f) but also to the resin-coated hard particles (c), whereby the stress can be evenly transferred over the entire first friction material even if the resin-coated hard particles (c) in the Center of a densely packed structure formed by four inorganic particles (f).

The relationship between inorganic particles (F) and hard particles (A) in the second friction material is similar. Namely acts when the ratio (R _A / R _F ) of R _A relative to R _{F is} equal to or greater than 0.2, wherein R _{F is} the average diameter of the inorganic particles (F) and R _{A is} the middle Diameter of the hard particles (A) is any compressive stress generated in the second friction material not only on the inorganic particles (F) but also on the hard particles (A), whereby the stress uniformly throughout the second even Friction material can be transferred when the hard particles (A) are in the center of a densely packed structure formed by four inorganic particles (F).

In the conditions (1) or (2), the inorganic particles (f) or (F) have an inorganic substance functioning as, for example, a friction modifier of the corresponding friction material. Specific materials which can be used for the inorganic particles (f) or (F) may include, for example, carbon, ceramics, oxides such as iron oxide or copper oxide, inorganic fillers such as barium sulfate or calcium carbonate, metal powders such as copper powder or brass powder or a solid lubricant such as graphite or molybdenum disulfide lock in.

In the condition (1), the Mohs hardness of the inorganic particles (f) and the inorganic particles (F) is preferably not more than 4, which is sufficient to provide higher frictional forces while achieving excellent frictional force stability and suppression of noise and vibration , If inorganic particles having a Mohs hardness of more than 4 are used in each of the first and second friction materials, the inorganic particles have a high yield stress, and therefore, if the first and second friction materials are subjected to stress, it may be more likely hard particles (a, A) of the resin-coated hard particles and / or the second friction material break when the resin-coated hard particles (c) are in contact with the inorganic particles (f) and when the hard particles (A) react with the inorganic particles Particles (F) are in contact. As a result, the wear increases in each friction material, so that the desired wear resistance may not be achieved. In particular, the Mohs hardness of at least one kind of the above-mentioned inorganic particles is better still not more than 3.5, and more preferably not more than 3.

Preferably, in the condition (1), at least 0.3 and / or R _A / R _F in the condition (2), r _c / r _{f is} at least 0.3. Even if the resin-coated hard particles (c) are in the middle of a densely packed structure formed of four inorganic particles (f), a ratio r _c / r _f of at least 0.3 enables a more reliable generation of stress in the resin-coated hard particles (c) when a compressive stress occurs in the first friction material. A ratio R _A / R _F of at least 0.3 is generated in the hard particles (A) even when the hard particles (A) are in the middle of a densely packed structure formed by four inorganic particles (F) Reliable tension, when in the above-described second friction material, a compressive stress occurs.

The mean diameter r _{f of} the inorganic particles (f), the mean diameter R _{F of} the inorganic particles (F), the average diameter r _{c of} the resin-coated hard particles (c) and the average diameter R _{A of} the hard particles (A) can be, for example be measured using laser diffraction or a scattering method (microtrack method).

In the condition (3), the first friction material satisfies the formula (1) below.

In the formula (1), s is the average layer thickness of the resin (b) in the resin-coated hard particles (c), E _b is the elastic modulus of the resin (b), E _m is the elastic modulus of the elastic material (m), and r _a is the mean diameter of the hard particles (a), where E _m > E _b .

5 Fig. 12 is a schematic sectional view comparatively illustrating the situation before and after the occurrence of strain in the resin-coated hard particles (c) on the friction surface portion and in the elastic material (m) constituting the matrix of the friction material, when stress is applied to the friction material acts. In the schematic diagram, the cross section of the resin-coated hard particles (c) in the tension-applying direction is shown in the form of cut-outs of small areas of large circles. The cross section of the elastic material (m) is also shown as sections of a portion of the same length as the resin coated hard particles (c). To emphasize the stretch, the cross sections are shown as bands. In 5 are an elastic material (m) 71m and resin-coated hard particles (c) 73c on a friction surface 70 before the friction material is subjected to stress. The elastic material 71m and the particles 73c are in 5 shown as dashed lines. An elastic material (m) 72m and resin-coated hard particles (c) 74c are depicted so that they represent the situation after on the elastic material 71m and the particles 73c by stresses σ _m and σ _c , which are generated by friction, in the in 5 indicated by the arrows indicated direction. In 5 are the elastic material 72m and the particles 74c shown as solid lines. The particles 73c contain the hard particles (a) 73a and the coating resin (b) 73b , and the particles 74c contain the hard particles (a) 74a and the coating resin (b) 74b , As in 5 is shown, r _{a is} the mean diameter of the hard particles 73a , and s is the average coating thickness of the coating resin 73b ,

If on the hard particles 74c a stress σ _c acts on the hard particles 74a a stress σ _a and on the coating resin 74b a stress σ _b . Because the resin-coated hard particles 74c , the hard particles 74a and the coating resin 74b are arranged in the center, the stresses can be expressed as σ _a = σ _b = σ _c = ε _b · E _b = ε _a · E _a (formula (1a)). In the formula (1a), ε _a and ε _b respectively denote the strain in the hard particles 74a and the coating resin 74b and E _a and E _b respectively denote the elastic moduli of the hard particles 74a and the coating resin 74b , In general, E _b << E _a , which is why it is assumed that ε _a = ε _b · (E _b / E _a ) ≈ 0. Therefore, the strain (the amount of displacement) is ε _{a of} the hard particles 74a in the resin-coated hard particles 74c is negligible, and thus it is possible to express ε _b as ε _b ≈ _e = γ / (2s) (formula (1b)), where ε _{c is} the elongation of the resin-coated hard particles 74c and γ represents the change in the size of the resin-coated hard particles 74c represents.

The stretching of the elastic material 72m can be expressed as ε _m = γ / (r _a + 2s) (formula (1c)), assuming that the average diameter of the elastic material 72m and the average diameter of the resin-coated hard particles 73c , as in 5 is, by and large, identical. In the formula (1c), it is considered that the change in the size of the resin-coated hard particles 74c and the change of the elastic material 72m , as in 5 is, on the whole, identical.

The relation σ _m ≤ σ _c must apply to allow the stress in the hard particles 74a within the resin-coated hard particles 74c concentrated. According to the above formula (1a), σ _b = σ _c , and therefore, the relation σ _m ≦ σ _{c can be expressed} as σ _m × E _m ≦ σ _b × E _b (formula (1d)). When the formulas (1b) and (1c) are used in the formula (1d), we obtain (E _m · γ) / (r _a + 2s) ≦ (E _b · γ) / (2s) (formula (1e)) , By converting the formula (1e), we obtain the above formula (1) in which E _m > E _b .

In the condition (3), E _{b is} preferably equal to or greater than 1 GPa, because a resin (b) having a sufficient elastic modulus prevents the hard particles (a) from falling off the first friction material during friction, and reaches suitable stress to which the hard particles (a) are exposed, and a suitable supernatant amount of the hard particles (a) from the friction surface, resulting in the hard particles (a) to suppress the occurrence of flow. If E _{b is} less than 1 GPa, the waste prevention effect and flow suppression effect of the hard particles (a) may be lost. In particular, E _{b is} preferably not less than 2 GPa, and more preferably not less than 3 GPa.

In the condition (3), E _{m is} preferably not less than 1 GPa because an elastic material (m) having a sufficient modulus of elasticity is subjected to a suitable stress to which the hard particles (a) are exposed and a suitable supernatant amount of the hard particles (a ) leads from the friction surface. In particular, E _{m is} preferably not less than 2 GPa, and more preferably not less than 3 GPa.

The method for calculating the average layer thickness s may, for example, be accompanied with a determination of the thickness of the coating resin, in which the diameter of the hard particles before the resin coating is subtracted from the diameter of the hard particles after the resin coating. The method for measuring the diameter of the hard particles before and after the resin coating may include, for example, laser diffraction or a scattering method (microtracking method).

For example, the moduli of elasticity E _b and E _m may be measured and calculated by means of a test according to the method described in the Japanese Industrial Standard JIS K 7181 is defined.

The method for measuring the mean diameter r _{a of} the hard particles (a) may be the same method used for measuring the mean diameter r _{f of} the inorganic particles (f).

In the condition (4), the first friction material and the second friction material satisfy the formula (2) below.

In the formula (2), C _a is the concentration (vol .-%) of the hard particles (a) in the first friction material, CA is the concentration (vol .-%) of the hard particles (A) in the second friction material, r _a is the mean diameter of the hard particles (a) in the first friction material, R _A is the mean diameter of the hard particles (A) in the second friction material, σ ₁ is the yield stress of the first friction material, and σ ₂ is the yield stress of the second Friction material, where σ ₁ = 10 to 100 MPa, σ ₂ = 100 to 800 MPa and C _A = 0.1 to 95 vol .-% applies.

The formula (2) is derived as follows. In the friction pair in the first embodiment of the invention, the frictional forces mainly occur in the hard particles. When friction occurs between the first friction material and the second friction material, a frictional force F ₁ received by the first friction material from the second friction material concentrates in the hard particles (a) on the outermost surface layer of the first friction material. The frictional force F ₁ must be from the hard particles (a) in the outermost surface layer and from the constituents surrounding the hard particles (a) (the elastic material (m), the resin (b) coating the hard particles , and inorganic particles (f)) are sustained. The first friction material comprises the hard particles (a) and the above-described surrounding components. Therefore, the yield stress on the material carrying the hard particles (a) is the yield stress σ _{1 of} the first friction material. Accordingly, the frictional force F _{1 can be expressed} as F ₁ α σ ₁ · r _a ² · C _a (formula (2a)), where C _{a is} the concentration of the hard particles (a) in the first friction material and r _{a is} the mean diameter the hard particle (a) in the first friction material.

Similar to the case of the first friction material, a friction force F ₂ received by the second friction material from the first friction material may be expressed as F ₂ α σ ₂ · R _A ² · C _A (Formula (2b)), where C _A the concentration of hard particles (A) in the second friction material is, R _{A is} the mean diameter of the hard particles (A) in the second friction material, and σ _{2 is} the yield stress of the second friction material. Ideally, F ₁ should be equal to F ₂ due to the law of actio and reactio, but formula (2) is obtained assuming 0.2 ≤ (F ₂ / F ₁ ) ≤ 5, taking into account the contact likelihood ,

In addition to meeting the formula (2) satisfies the condition (4) requires that σ ₁ = 10 to 100 MPa, σ ₂ = 100 to 800 MPa and C _A = 0.1 to 95 vol .-% is applicable. Sufficient friction force can not be generated if the yield stress σ _{1 of} the first friction material is less than 10 MPa. If the σ ₁ value is more than 100 MPa, the second friction material may suffer from excessive wear. Preferably, σ _{1 is} not less than 22 MPa, and more preferably not less than 24 MPa. In addition, σ _{1 is} preferably not more than 38 MPa, and more preferably not more than 36 MPa.

Sufficient friction force can not be generated when the yield stress σ _{2 of} the second friction material is less than 100 MPa. If the σ ₂ value is more than 800 MPa, the first friction material may suffer from excessive wear. Preferably, σ _{2 is} not less than 110 MPa, and more preferably not less than 120 MPa. In addition, σ _{2 is} preferably not more than 790 MPa, and more preferably not more than 780 MPa.

The yield stress σ _{1 of} the first friction material and the yield stress σ _{2 of} the second friction material can be measured and calculated by determining the yield stress based on a test according to the above-mentioned method JIS K 7181 is defined.

Sufficient frictional force can not be generated when the concentration C _A of hard particles (A) is in the second friction material is less than 0.1 vol .-%. If the value of C _{A is} more than 95% by volume, the first friction material may suffer from excessive wear. C _A is preferably at least 0.15 vol .-%, and more preferably at least 0.2 vol .-%. In addition, CA is preferably not more than 92.5% by volume, and more preferably not more than 90% by volume.

From the conditions σ ₁ = 10 to 100 MPa and σ ₂ = 100 to 800 MPa, the inequality 1 ≤ (σ ₂ / σ ₁ ) ≤ 80 arises (formula (2c)). From the formula (2c) and the formula (2), the inequality formula (2d) below can be derived.

2 is a graph schematically illustrating one of the condition (4) defined area, wherein the X-axis (r _a / R _A) ² represents and the Y-axis (C _a / C _A) represents. The range represented by the formula (2d) is represented by the curve (C _a / C _A ) · (r _a / R _A ) ² = 0.2 and the curve (C _a / C _A ) · (r _a / R _A ) ² = 400 limited. Since C _A = 0.1 to 95% by volume, the upper limit γ ₁ of (C _a / C _A ) is γ ₁ (= C _a / 0.1% by volume) and the lower limit is γ ₂ (= C _a / 95 vol.%). The area represented by the condition (4) is thus the area with the oblique hatching in the graph.

In the friction pair of the first embodiment of the invention, under the above conditions (1) to (4), at least condition (1) is preferably satisfied from the viewpoint of the above-described stress distribution mechanism and material designing method, better still at least conditions (1) and (3) are satisfied ), and it is best to satisfy all the conditions (1) to (4).

Next, a detailed explanation will be given on the first friction material, the resin-coated hard particles (c) in the first friction material in which the hard particles (a) are coated with the resin (b) and the elastic other than the resin-coated hard particles Material (m) that forms the matrix of the first friction material. A detailed explanation next follows next to the second friction material, the hard particles (A) in the second friction material, and the matrix material (M) having a lower Mohs hardness than the hard particles (A) and a higher Mohs hardness than the resin (b). and in which the hard particles (A) are embedded.

The hard particles (a) and (A) used in the first friction material and the second friction material have a high hardness and are made of a material which is the main agent responsible for the friction of the friction material. Specific examples of such a material are, for example, ceramic materials. The ceramics include carbides such as silicon carbide, tungsten carbide, boron carbide, titanium carbide, zirconium carbide, tantalum carbide, iron carbide or chromium carbide; Oxides such as alumina, zirconia, titania, chromia or silica; Nitrides such as silicon nitride, titanium nitride, boron nitride or zirconium nitride; or boron compounds such as titanium boride or iron boride. In addition to the above-mentioned ceramic materials, hard intermetallic compounds such as FeAl can be used as the hard particles (a) and the hard particles (A). The hard particles (a) and (A) may be the same material among the above-mentioned materials. Alternatively, the hard particles (a) and (A) may be different materials. Also, for the hard particles (a) and the hard particles (A), mixtures of two or more different materials of the above materials may be used.

In order to increase the frictional force while achieving excellent frictional force stability and suppression of noise and vibration, the Mohs hardness of at least one kind of the hard particles (a) and the hard particles (A) is preferably not less than 4.5. The hard particles have a low yield stress when hard particles having a Mohs hardness of less than 4.5 are used in both of the first and second friction materials, and thus the higher the probability that the hard particles will flow in the hard particles as well as the second material are subjected to tension. This increases wear in each friction material itself, which may preclude achieving the desired wear resistance. In particular, the Mohs hardness of at least one kind of the above hard particles is preferably not less than 4.75 and better still not less than 5.

The resin (b) used in the first friction material is an elastic material having an appropriate elastic modulus. The resin (b) is mainly responsible for sufficiently reducing the supernatant amount of the hard particles (a) from the friction surface by being deformed during friction. Namely, the resin (b) is preferably at least one non-crystalline resin selected from polyimides, polyamide-imides, polycarbonates, polyphenylene ethers, polyallylates, polysulfones and polyethersulfones. The choice of a suitable non-crystalline resin results in a more suitable stress to which the hard particles (a) are exposed and a more suitable amount of supernatant of the hard particles (a) from the friction surface during friction and better suppression of flow of the hard particles. The resin (b) may be a mixture of two or more different materials of the above materials.

The resin-coated hard particles (c) used in the first friction material are finished by completely coating the hard particles (a) with the resin (b). By the hard particles coated with an elastic resin, unlike the case where the hard particles are not coated with the elastic resin, the resin functions to sufficiently reduce the supernatant amount of the hard particles from the friction surface, while also imparting hard particles to the hard particles allowed to sufficiently generate a high frictional force.

The method for coating the hard particles with the elastic resin may, for example, be a dipping method in which the hard particles are coated with the elastic resin by dipping; a coating method in which the elastic resin in the form of a spray or the like is applied to the hard particles; a method in which the coating resin and the hard particles are mechanically kneaded together into pellets; or a method in which the coating resin is formed as a fluid layer and the hard particles heated to a temperature equal to or higher than the softening point of the resin are fed into the fluid layer. The optimum coating method can be selected in accordance with the material actually used. In particular, the coating method is preferably selected from among the methods described above, because this makes it possible to make the thickness of the elastic resin coating (for example, the average coating thickness s in the above condition (3)) with higher accuracy.

Besides the resin-coated hard particles (c), the first friction material according to a first aspect of the invention further comprises an elastic material (m) other than the resin-coated hard particles. The elastic material also forms the matrix of the first friction material.

The elastic material (m) preferably contains at least one elastic material selected from phenol resins, modified phenol resins, amino resins, furan resins, unsaturated polyester resins, diallylphthalate resins, alkyd resins, epoxy resins, thermosetting polyamideimide resins, thermosetting polyimide resins, and silicone resins. The selection of a suitable elastic material results in a more suitable stress to which the hard particles (a) are exposed and a more suitable amount of supernatant of the hard particles (a) from the friction surface during the friction.

The matrix material (M) forms the matrix of the second friction material. Specific examples of the matrix material (M) include, for example, a metallic material such as iron, cobalt, nickel, chromium, titanium, copper, aluminum or alloys having one of these metals as a main component; or an inorganic material such as carbon, a composite of carbon and carbon fibers or a composite of carbon and a ceramic.

The first friction material according to a first aspect of the invention may also use a base material. The base material used is preferably a material that does not deform when heated, especially organic fibers such as aramid fibers, nylon, cellulose or the like or inorganic fibers such as steel fibers, copper fibers, ceramic fibers, glass fibers, rock wool or the like. The proportion of the base material preferably ranges from 5 to 50% by volume of the entire friction material.

The first friction material preferably contains not less than 5% by volume in total of the resin-coated hard particles (c) and the elastic material (m), wherein the volume ratio of the resin-coated hard particles (c) to the elastic material (m) falls within the range of 2: 1 to 1:50 falls. With respect to the above-described stress distribution mechanism, the combined effects of frictional force stability and noise and vibration suppression may not be sufficiently adjusted when the total concentration of resin-coated hard particles (c) and elastic material (m) is less than 5% by volume , The wear of the second friction material may increase relative to that of the first friction material when the concentration of the resin-coated hard particles (c) exceeds a concentration at which the volume ratio of the resin-coated hard particles (c) to the elastic material (m) is 2: 1. On the other hand, the friction force may decrease when the concentration of the elastic material (m) exceeds the concentration at which the volume ratio of the resin-coated hard particles (c) to the elastic material (m) is 1:50. In particular, the total concentration of resin-coated hard particles (c) and elastic material (m) is preferably not less than 6% by volume, and the volume ratio of the resin-coated hard particles (c) to the elastic material (m) is preferably in the range of 1: 1 to 1:30 falls. Most preferably, the total concentration of resin-coated hard particles (c) and elastic material (m) is not less than 7% by volume, and the volume ratio of resin-coated hard particles (c) to elastic material (m) is from 1: 2 to 1: 10 is enough.

The elastic modulus of the first friction material preferably ranges from 100 to 300 MPa. The modulus of elasticity of the friction material as a whole may become too low when the elastic modulus of the first friction material is less than 100 MPa. This can prevent a more suitable stress, which is exposed to the hard particles (a) contained in the first friction material, and a more appropriate amount of protrusion of the hard particles (a) from the friction surface. The modulus of elasticity of the first friction material as a whole may be too high when the elastic modulus of the first friction material is more than 300 MPa. Thereby, the hard particles (a) in the first friction material may fall off during the friction. In particular, the elastic modulus of the first friction material is preferably not less than 120 MPa, and more preferably not less than 140 MPa. In addition, the elastic modulus of the friction material is preferably not more than 280 MPa, and more preferably not more than 260 MPa. The method for measuring the elastic modulus of the first friction material may be the same as the method for measuring the elastic modulus of the above-described elastic resin or the elastic modulus of the elastic material.

The surface roughness of the friction surface of the second friction material is preferably not more than 10 μm, since a surface roughness of more than 10 μm may impair initial braking, which in turn may lead to friction force variation and increased wear. The surface roughness is in accordance with the ten-point mean roughness (R _z JIS) according to Japanese Industrial Standard JIS B 0601 Are defined. In particular, the surface roughness of the friction surface of the second friction material is at most 9 μm, and more preferably not more than 8 μm. The above-described effects can be sufficiently adjusted when the surface roughness of the friction surface of the second friction material is at least 0.01 μm.

The above-explained materials comprising the first friction material may be mixed by using a conventional method, for example, dry mixing using a vertical mixer, a horizontal mixer or the like; or a method in which wet mixing is carried out using the above mixer or the like under the presence of water or an organic solvent, followed by vacuum deaeration or heating deaeration to remove the solvent. The friction material may be formed by using a method in which the mixture obtained by using the mixing methods described above is filled and pressed into a heated mold, or a method in which a mixture obtained by the above mixing methods is bonded to a base material , The friction material may be formed into a suitable shape such as a wire, a rod, a plate or a sheet.

The second friction material may be prepared by using various methods, such as mixing a ball mill or the like by mixing the hard particles (A) with particles of the matrix material (M) and, if necessary, with inorganic particles (F) followed by eager to sinter the resulting mixture; Bonding a sintered body to a friction surface portion of a structural base member by mechanical fastening or by welding, such as arc welding or laser welding; Spraying a mixed material powder onto the friction surface of a structural base member by plasma spraying or the like; or applying a metallic material (M) in which hard particles (A) or hard particles (A) and inorganic particles (F) are dispersed by particle dispersion deposition on the friction surface of a structural base member. A casting method may also be used as long as hard particles segregate during the solidification process. The second friction material may be cast iron, provided that the alloy composition and casting conditions are controlled so that cementite (iron carbide) separates out.

3 Fig. 10 is a schematic sectional view illustrating a typical example of a friction pair of the invention. The friction pair 100 The invention has a first friction material 1 and a second friction material 2 such that a friction surface 41 of the first friction material 1 against a friction surface 43 of the second friction material 2 encounters. The first friction material 1 has resin-coated hard particles (c) 13 in which hard particles (a) 11 with a resin (b) 12 coated and one of the particles (c) 13 different elastic material (m) 14 which forms the matrix of the first friction material. The second friction material 2 has hard particles (A) 21 and a matrix material (M) 24 , The friction pair 100 preferably satisfies at least the two conditions (1) and (3) described above.

The 4A and 4B Fig. 12 are schematic sectional views illustrating typical examples of the above friction pair before and after stress application. 4A illustrates the situation before application of a tension to a typical example of the friction pair, ie the situation prior to sliding friction. The projection section 50 of hard particles (a) 11 and (A) 21 , which protrudes from the friction surface of the respective friction material is a factor that the stress applied to the friction pair exceeds the yield stress in the hard particles. 4B represents the situation after application of a tension to a typical example of the friction pair, ie the situation during the sliding friction. As shown in the figure, the resin (b) 12 containing the hard particles (a) 11 coated, and the matrix material (M) 24 deformed during stress application. This has the friction pair 100 a stress distribution mechanism that provides sufficient excessive stress to the hard particles (a) 11 , (A) 21 is passed through the deformation of the resin (b) 12 or the matrix material (M) 24 is absorbed when the friction pair 100 is subjected to a voltage. This makes it less likely that the hard particles will be exposed to stress beyond the yield stress. In addition, the elastic material ensures (m) 14 in the first friction material, a contact surface 15 over the entire friction surface. This allows effective friction over the entire surface between the friction surfaces.

The friction pair in the above typical example thus has a stress distribution mechanism by which sufficient excessive stress, which is transmitted to the hard particles (a), (A) upon application of a stress to the friction pair, through the resin (b) or through the matrix material (M), whereby it is less likely that the hard particles (a), (A) will be exposed to a stress exceeding the yield stress. Therefore, the friction pair by means of the hard particles (a), (A) generates high frictional force, while achieving excellent frictional force stability and suppression of noise and vibration.

1. Preparation of resin-coated hard particles by coating hard particles (a) with a resin (b)

As the hard particles (a) silicon carbide (SiC, Mohs hardness 9.3, Green Densic ^® (GC) by Showa Denko) was used. As the resin (b) was used, a polyamide-imide ((hereafter PAI, Molykote ^® PA-744) from Dow Corning Toray). To coat the hard particles (a) with the resin (b), the SiC was mixed with PAI dissolved in a solvent in an equivalent volume ratio (1: 1) of PAI and SiC (solid in solvent). The solvent was then evaporated to form the resin-coated hard particles. The particle size of SiC before and after the resin coating. was measured using a laser diffraction particle size analyzer. The thickness of the resin coating (s) was then calculated based on the difference between the mean diameter of SiC after the resin coating and the mean diameter of SiC before the resin coating.

2. Production of a friction pair

A first friction material (brake pad) according to an example of the invention was prepared by mixing the materials shown in Table 1 below in the proportions indicated (% by volume). The term "SiC (PAI-coated)" in Table 1 denotes resin-coated silicon carbide obtained in the above-described preparation of resin-coated hard particles. The particle sizes indicated in Table 1 below were measured using the laser diffraction particle size analyzer described above. Among the materials shown in Table 1, the Mohs hardness of the SiC (the hard particle (a)) is 9.3, and the average diameter of the resin-coated SiC is 26 μm. The Mohs hardness of Mika (inorganic particles (f), average diameter 15 μm) is 2.5 to 3.0. The Mohs hardness of barium sulfate (inorganic particles (f), average diameter 10 μm) is 3.5. Therefore, the first friction material of the example satisfies the condition (1). The details of the manufacturing process were as follows. First, various raw materials were mixed uniformly for 5 minutes in a vertical mixer to give a raw material raw material mixture. In a following step, the hot mold was filled in a Reibmaterialausgangsgemisch heated to 150 ° C for 10 minutes shape and pressed at 200 kg / cm ^2. This was followed by curing at 200 ° C for 2 hours to give the first friction material. The second friction material (disc) was prepared according to the procedure below. As the hard particles (A), tungsten carbide (WC, Mohs hardness 9) having an average diameter of 3 μm was used, while as the matrix material (M), cobalt (Mohs hardness 5.5) was used. The second friction material was obtained by plasma spraying the WC onto a cast iron disk using cobalt as the binder. The WC concentration in the spray layer was 90% by volume. The first friction material (brake pad) and the second friction material (disc) were combined to give the friction pair of the example.

A first friction material (brake pad) of a comparative example was prepared by mixing the materials shown in Table 1 below in the proportions (% by volume) shown in Table 1 in the column of Comparative Example. The term "SiC (uncoated)" in the Table 1, silicon carbide (SiC), Mohs' hardness 9.3, Green Densic ^® (GC) of Showa Denko), was as it was used without any resin coating. The particle sizes indicated in Table 1 below were measured using the laser diffraction particle size analyzer described above. In the materials shown in Table 1 below, the SiC has by definition no resin coating, and therefore, the first friction material of this Comparative Example does not satisfy Condition (1). The details of the manufacturing process were as follows. First, uniformly different starting materials were mixed in a vertical mixer for 5 minutes to give a raw material raw material mixture. In a subsequent hot-forming step, the raw material starting material mixture was filled in a mold heated to 150 ° C and pressed at 200 kg / cm ^{2 for} 10 minutes. This was followed by curing at 200 ° C for 2 hours to give the first friction material. The second friction material (disc) was made using the same method as used in the preparation of the second friction material of the friction pair according to the example. The first friction material (brake pad) and the second friction material (disc) were combined to give the friction pair of the comparative example. Table 1 starting material component Concentration (% by volume) example Comparative example Fiber base material aramid 5 5 copper fibers 10 10 glass fibers 10 10 Friction modifier and filler Graphite (average particle diameter: 5 μm) 5 5 SiC (PAI-coated, average particle diameter: 26 μm) 10 0 SiC (uncoated, average particle diameter: 20 μm) 0 10 Mika (average particle diameter: 15 μm) 10 10 Barium sulfate (average particle diameter: 10 μm) 30 30 binder phenolic resin 20 20 total 100 100

3. Measurement and evaluation of the friction properties of the friction pair

Sample bodies of the friction pairs according to the example and the comparative example were placed under a load of 200 N at a temperature of 100 ° C or 300 ° C and allowed to slide against each other at a speed of 1 m / sec for 1 hour, followed by braking of 1 m / s to 0 m / s. Table 2 compares the coefficient of friction (μ), the coefficient of friction change (Δμ) during braking, and the amounts of wear before and after braking. Table 2 example Comparative example Coefficient of friction (μ) / 100 ° C 0.65 0.65 Coefficient of friction (μ) / 300 ° C 0.65 0.65 Δμ / ° C 1:00 0.02 0.05 Δμ / 300 ° C 0.03 0.06 Wear Quantity / 100 ° C 0.1 mm 0.1 mm Wear Quantity / 300 ° C 0.3 mm 0.3 mm

As shown in Table 2, the coefficients of friction μ and the amount of wear in the friction pairs of Example and Comparative Example were the same at both 100 ° C and 300 ° C. In contrast, the coefficient of friction change Δμ remained smaller in the friction pair of the example. The results of the above friction property measurements show that the friction pair of the example of the invention satisfying the condition (1) has, in particular, a better friction force stability as compared with a conventional friction pair which does not satisfy the condition (1).

4. Measurement and evaluation of the squeaking of the friction pair

During a simulated city trip of a motor vehicle equipped with the respective friction pair (braking 100 times at a speed of 40 km / h, with a deceleration of 0.1 to 1.5 m / s ² and a temperature of 50 to 150 ° C), the Number of occurrences of squeaks and the volume of this squeaking for the friction pairs of the example and the comparative example measured. Table 3 compares the number of squeaks and their volume together. Table 3 example Comparative example Occurrence of squeaks 40 times 100 times Quietschlautstärke Medium - low High - medium

As Table 3 shows, the friction pair of the example gave less squeaking than the friction pair of the comparative example, and at lower volume. The measurement results of the frictional properties with respect to squeaking show that the friction pair of the example of the invention satisfying the condition (1) suppresses brake squeal to a greater degree than a conventional friction pair which does not satisfy the condition (1).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2003-268352 A [0004, 0005]

Cited non-patent literature

• JIS K 7181 [0071]
• JIS K 7181 [0079]
• JIS B 0601 [0096]

Claims (15)

Friction pair that generates a friction force by means of mutual sliding friction, wherein the friction pair comprises: a first friction material containing first hard particles and a resin having a lower Mohs hardness than the first hard particles, the resin surrounding the entire surface of the first hard particles; and a second friction material containing the second hard particle and either a metallic material or an inorganic material having a lower Mohs hardness than the second hard particles and having a higher Mohs hardness than the resin, the metallic material or the inorganic material forming a matrix of the second friction material, in which the second hard particles are embedded. The friction pair according to claim 1, wherein the first friction material further comprises an elastic material forming a matrix of the first friction material in which resin-coated hard particles are embedded in which the first hard particles are coated by the resin. The friction pair according to claim 2, wherein the friction pair satisfies at least one of the following four conditions, wherein the first condition is satisfied when the first friction material further contains first inorganic particles having a lower Mohs hardness than the first hard particles and a first ratio of the average diameter of the resin-coated ones hard particles with respect to the mean diameter of the first inorganic particles is not less than 0.2; the second condition is satisfied when the second friction material further contains second inorganic particles having a lower Mohs hardness than the second hard particles and a second ratio of the mean diameter of the second hard particles to the mean diameter of the second inorganic particles is not less than 0.2 ; the third condition is satisfied when the first friction material satisfies the formula (1) below

where s is the average coating thickness of the resin on the resin-coated hard particles, E _{b is} the elastic modulus of the resin, E _{m is} the elastic modulus of the elastic material, and r _{a is} the mean diameter of the first hard particles, where E _m > E _b ; and the fourth condition is satisfied when the first friction material and the second friction material satisfy the formula (2) below

where C _{a is} the concentration (vol%) of the first hard particles in the first friction material, C _{A is} the concentration (vol%) of the second hard particles in the second friction material, r _{a is} the mean diameter of the first hard particles in the first friction material, R _{A is} the mean diameter of the second hard particles in the second friction material, σ _{1 is} the yield stress of the first friction material and σ _{2 is} the yield stress of the second friction material, where σ ₁ = 10 to 100 MPa, σ ₂ = 100 to 800 MPa and C _A = 0.1 to 95 vol .-% applies. A friction pair according to claim 3, wherein the friction pair satisfies all of the first to fourth conditions. Friction pair according to one of claims 1 to 4, wherein the first hard particles and / or the second hard particles have a Mohs hardness of at least 4.5. The friction pair according to any one of claims 3 to 5, wherein the friction pair satisfies the third condition and the elastic modulus of the resin is not less than 1 GPa. A friction pair according to any one of claims 1 to 6, wherein the resin is at least one non-crystalline resin selected from the group consisting of polyimides, polyamide-imides, polycarbonates, polyphenylene ethers, polyallylates, polysulfones and polyethersulfones. A friction pair according to any one of claims 3 to 7, wherein the friction pair satisfies the first condition and / or the second condition and the first inorganic particles and / or the second inorganic particles have a Mohs hardness of not more than 4. Friction pair according to one of claims 3 to 8, wherein the friction pair satisfies the third condition and the elastic modulus of the elastic material is at least 1 GPa. A friction pair according to any one of claims 2 to 9, wherein the elastic material comprises at least one resin selected from the group consisting of phenol resins, modified phenolic resins, amino resins, furan resins, unsaturated polyester resins, diallylphthalate resins, alkyd resins, epoxy resins, thermosetting polyamideimide resins, thermosetting polyimide resins and silicone resins is. A friction pair according to any one of claims 3 to 10, wherein the friction pair satisfies the first condition and / or the second condition, and the first ratio and / or the second ratio is equal to or greater than 0.3. The friction pair of claim 11, wherein the friction pair satisfies both the first condition and the second condition and both the first ratio and the second ratio are at least 0.3. A friction pair according to any one of claims 2 to 12, wherein the concentration of the resin-coated hard particles and the elastic material in the first friction material is at least 5% by volume, and the volume ratio of the resin-coated hard particles to the elastic material is from 2: 1 to 1:50 enough. Friction pair according to one of claims 1 to 13, wherein the modulus of elasticity of the first friction material ( 1 ) Is 100 to 300 MPa. A friction pair according to any one of claims 1 to 14, wherein the surface roughness of the friction surface of the second friction material is not more than 10 μm.

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