JP2018111784A - Friction material composition, friction material and friction member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce fading phenomenon generation itself by reducing temperature increase itself of a friction material during use, and suppressing deterioration of the friction material caused by the temperature increase of the friction material.SOLUTION: In a friction composition containing a reinforced fiber material, a friction adjustment material and a binder, a material absorbing heat by a transition enthalpy accompanying solid-solid phase transition is further blended as a heat storage material. The heat storage material may be an inorganic oxide-based compound, and may be vanadium dioxide-based compound represented by the general formula:VMOand/or LiVO. In the above formula, M is an element having tetra-, penta- or hexa- valency, X is the number of 0 or more and less than 1. Preferably M is one or more kind of element selected from Cr, W, Mo, Nb, Ta, Os, Ir, Ru and Re and X is the number of 0 or more and 0.5 or less.SELECTED DRAWING: None

Description

  The present invention is a friction material that can reduce the occurrence of a fade phenomenon itself by reducing the temperature rise of the friction material during use, and can suppress the deterioration of the friction material due to the temperature rise of the friction material. The present invention relates to a composition, a friction material, and a friction member.

  A friction material used in an automobile brake pad or the like is required to have high wear resistance and a stable high coefficient of friction. For the purpose of achieving such characteristics, the composition constituting the friction material (hereinafter sometimes referred to as “friction material composition”) includes a reinforcing fiber material, a friction modifier, and a bond. Materials etc. are blended at an appropriate ratio.

  However, when the load is used in a high load state, for example, when the brake is used continuously or during sudden braking, a so-called “fade phenomenon” may occur. In the fade phenomenon, the temperature of the friction material rises (for example, up to about 300 ° C. to 400 ° C.) due to frictional heat generated with use under a high load state, for example, a resin as a binder (for example, phenol resin) And / or other organic components are thermally decomposed to produce liquid or gaseous decomposition products. And when this decomposition product intervenes in a friction sliding surface, the friction coefficient in a friction sliding surface will fall and the braking force as a brake will fall.

  Moreover, when at least a part of the friction material reaches a higher temperature (for example, a temperature of 600 ° C. or more) due to a higher load, the organic fiber as the reinforcing fiber material is thermally decomposed, and the life as the friction material is greatly increased. May be shorter. Therefore, in the friction material according to the prior art, technical development has been made with a focus on reducing the friction coefficient and / or the deterioration of the friction material at high temperatures.

For example, a friction material and a drum brake having excellent fade characteristics and wear resistance by containing a titanate compound content of 1 to 22% by volume and a binder of 18% by volume or more with respect to the entire friction material A technique for providing a friction material has been proposed (see, for example, Patent Document 1). Further, in a friction material composition containing a binder, a fiber substrate (reinforcing fiber material), an abrasive (abrasive), an inorganic filler, and an organic filler, the specific surface area calculated by the BET method is 400 to 800 m ² /. A technique for improving the squealing characteristics without significantly lowering the coefficient of friction at a high temperature by incorporating a silicate having a Mohs hardness of 6 or less as an abrasive material is proposed. (For example, refer to Patent Document 2).

JP 2014-224175 A JP, 2015-165024, A JP 2010-163510 A

  As described above, in the friction material according to the related art, it has been proposed to reduce the friction coefficient and / or the deterioration of the friction material at a high temperature by adding a specific material to the friction material composition. It was. That is, these conventional techniques are developed on the premise that “the friction material becomes high temperature”.

  However, the present inventor thought that the occurrence of the fade phenomenon itself should be reduced if the temperature rise of the friction material itself during use can be reduced. That is, one object of the present invention is to provide a friction material composition, a friction material, and a friction member that can reduce the occurrence of the fade phenomenon itself by reducing the temperature rise of the friction material during use. To do.

  As a result of diligent research, the present inventor, by blending a heat storage material with the composition constituting the friction material, for example, stores the friction heat generated when used in a brake pad or the like, thereby increasing the temperature of the friction material. It has been found that it can be reduced.

  In view of the above, the friction material composition according to the present invention (hereinafter sometimes referred to as “the composition of the present invention”) includes a reinforcing fiber material, a friction adjusting material, and a binding material. The composition is a friction material composition further comprising a substance that absorbs heat by a transition enthalpy accompanying a solid-solid phase transition as a heat storage material.

  Furthermore, the friction material according to the present invention (hereinafter sometimes referred to as “the present friction material”) is a friction material formed by molding the composition of the present invention.

  In addition, the friction member according to the present invention (hereinafter sometimes referred to as “the present friction member”) is a friction member made of the friction material of the present invention and a back metal.

  According to the composition of the present invention, the heat storage material absorbs friction heat generated during use as a friction material, and the temperature rise of the friction material can be reduced. As a result, the occurrence of the fade phenomenon itself can be reduced. Furthermore, for example, a reduction in the friction coefficient (that is, a reduction in braking force) due to thermal decomposition of the resin as a binder and / or other organic components is reduced, or the organic fiber as a reinforcing fiber material is thermally decomposed. The resulting shortening of the life (that is, shortening of the service life) can be reduced.

  In addition to the above, the heat storage material contained in the composition of the present invention is a substance that absorbs heat due to the transition enthalpy accompanying the solid-solid phase transition, and therefore does not liquefy with the heat storage. As a result, as will be described in detail later, it is possible to reduce the possibility that the heat storage material leaks out of the system as the heat is stored, or the friction coefficient decreases due to being interposed in the friction sliding surface.

  Other objects, other features, and attendant advantages of the present invention will be readily understood from the description of each embodiment of the present invention described with reference to the following drawings.

<< First Embodiment >>
Hereinafter, the friction material composition according to the first embodiment of the present invention (hereinafter may be referred to as “first composition”) will be described. First, the heat storage material will be described in detail below.

<Heat storage material>
As described above, as a result of earnest research, the present inventor, by blending a heat storage material with the composition constituting the friction material, stores the frictional heat generated when used in, for example, a brake pad, etc. It has been found that the temperature rise of the material can be reduced. The heat storage material is a material that can release and / or absorb heat at a constant temperature, and can reduce a temperature change associated with the entry and exit of heat. As such a heat storage material, a wide variety of substances are known. A sensible heat storage material that stores heat using the specific heat of the material, and a change in enthalpy accompanying the phase transition of the material (hereinafter referred to as “transfer enthalpy”). And the latent heat storage material that uses the latent heat storage material.

  Of these two types of heat storage materials, a latent heat storage material is desirable from the viewpoint of storing a relatively large amount of heat. Specific examples of the latent heat storage material include inorganic salt hydrates, organic compounds, and molten salts. However, any of these latent heat storage materials is a heat storage material that utilizes a transition enthalpy associated with a phase transition (solid-liquid phase transition) between a solid state and a liquid state. When a heat storage material that transitions from a solid phase to a liquid phase with heat storage is blended into the friction material composition, the heat storage material liquefied with heat storage leaks out of the system or intervenes in the friction sliding surface. As a result, the friction coefficient may decrease. Depending on the type of the heat storage material, the heat storage material may be phase-separated into a liquid phase and a solid phase or decomposed along with the heat storage.

  On the other hand, a heat storage material that utilizes a transition enthalpy associated with a phase transition between a solid state and a solid state (solid-solid phase transition) does not liquefy with heat storage. As a result, there is no possibility that the heat storage material leaks out of the system with heat storage or the friction coefficient decreases due to interposition in the friction sliding surface. Furthermore, there is no possibility that the heat storage material is phase-separated into a liquid phase and a solid phase or decomposed with heat storage. Therefore, as the heat storage material blended in the first composition, it is desirable to use a substance that absorbs heat by the transition enthalpy accompanying the solid-solid phase transition.

<Constitution>
Next, the configuration of the first composition will be described. The first composition is a friction material composition including a reinforcing fiber material, a friction adjusting material, and a binding material.

  As the reinforcing fiber material contained in the first composition, one or two or more additives that are conventionally blended in the friction material composition as a reinforcing fiber material can be blended. Examples of such reinforcing fiber material include inorganic fibers and organic fibers. Examples of inorganic fibers include metal fibers such as copper fibers and iron fibers, glass fibers, rock wool (rock wool), ceramic fibers such as wollastonite fibers and potassium titanate fibers, and carbon fibers (carbon fibers). Can be mentioned. Examples of organic fibers include resin fibers such as aramid fibers, cellulose fibers, and acrylic fibers.

  The type and content of the material blended in the first composition as the reinforcing fiber material are the friction characteristics (for example, friction coefficient, wear resistance, vibration characteristics, and the like) required for the friction material obtained by molding the first composition. It can be determined as appropriate according to various physical properties such as squealing characteristics and durability. The content (mixing ratio) of the reinforcing fiber material with respect to the entire first composition is not particularly limited, but is generally about 3% by mass to 30% by mass.

  The friction modifier has a role of adjusting the friction characteristics of the friction material. As the friction modifier contained in the first composition, one or two or more additives that are conventionally blended in the friction material composition as a friction modifier can be blended. Examples of such friction modifiers include abrasives (abrasives), organic dust, inorganic dust, and metal powder. Examples of the abrasive include inorganic particles such as alumina and chromite. Examples of the organic dust include friction dust such as cashew dust and rubber dust (rubber dust). Examples of inorganic dust include calcium hydroxide, magnesium hydroxide, calcium carbonate, barium sulfate, iron oxide, zirconium oxide, magnesium oxide, aluminum oxide, magnesium silicate, zirconium silicate, potassium titanate, vermiculite and mica. Can do. Examples of the metal powder include copper, brass, tin, iron and zinc powder.

  The kind and content of the material blended in the first composition as a friction modifier can be appropriately determined according to various physical properties required for the friction material obtained by molding the first composition. The content (mixing ratio) of the friction modifier with respect to the entire first composition is not particularly limited, but is generally about 30% to 70% by mass.

  The binder has a role of binding various blending components constituting the friction material. As the binder contained in the first composition, one or two or more additives that are conventionally blended in the friction material composition as a binder can be blended. Examples of such a binder include thermosetting resins such as phenol resin, melamine resin, epoxy resin, polyimide resin and urea resin, and modified products of the thermosetting resin. Specific examples of such thermosetting resins include elastomer-modified phenol resins, phenol resins (including straight phenol resins and various modified phenol resins), melamine resins, epoxy resins, polyimide resins, and various rubbers. be able to. Examples of various modified phenol resins include hydrocarbon resin-modified phenol resins, epoxy-modified phenol resins, rubber-modified phenol resins, and the like. Examples of various rubbers include nitrile rubber (NBR) and acrylic.

  The kind and content of the material blended in the first composition as a binder can be appropriately determined according to various physical properties required for the friction material obtained by molding the first composition. Although the content rate (blending ratio) of the binder with respect to the entire first composition is not particularly limited, it is generally about 5% by mass to 20% by mass.

  In addition to the above, the first composition further includes, as a heat storage material, a substance that absorbs heat by a transition enthalpy accompanying a solid-solid phase transition. As described above, the “solid-solid phase transition” is a phase transition between a solid state and a solid state, and a heat storage material that uses a transition enthalpy associated with a solid-solid phase transition does not liquefy with heat storage.

  Examples of the latent heat storage material as described above include a heat storage material made of a substance that stores heat by electronic phase transition. Specifically, examples of the latent heat storage material as described above include a substance that stores heat by changing the crystal structure with heat storage.

  In addition, although the magnitude | size (for example, particle size etc.) of a thermal storage material is not specifically limited, For example, from viewpoints of workability, the dispersibility in a friction material composition, oxidation resistance (oxidation stability), etc., it is 1 micrometer thru | or 100 micrometers. It is desirable for the heat storage material to have a particle size.

  Further, for example, when there is a problem in the adhesion between the heat storage material and the binder, the heat storage material may be subjected to a surface treatment. Specific examples of such surface treatment include, for example, plating treatment with various metals and coating treatment with various coupling agents (for example, silane coupling agents).

<effect>
As described above, the first composition includes a heat storage material. With this heat storage material, friction heat generated when the friction material obtained by molding the first composition is used, for example, in a brake pad or the like can be stored, and the temperature rise of the friction material can be reduced. As a result, according to the first composition, the occurrence of the fade phenomenon itself can be reduced. Furthermore, for example, a reduction in the friction coefficient (that is, a reduction in braking force) due to thermal decomposition of the resin as a binder and / or other organic components is reduced, or the organic fiber as a reinforcing fiber material is thermally decomposed. The resulting shortening of the life (that is, shortening of the service life) can be reduced.

  Also, for example, in applications as wet friction materials such as clutches in automatic transmissions (AT), the temperature change of automatic transmission oil (AT fluid, AT oil) is reduced by heat absorption and heat dissipation by the heat storage material. be able to. As a result, it is possible to reduce the deterioration of the automatic transmission fluid or to promote the heat retention of the automatic transmission fluid.

  In addition, since the heat storage material contained in the first composition is a substance that absorbs heat by the transition enthalpy accompanying the solid-solid phase transition, it does not liquefy with the heat storage. As a result, according to the first composition, it is possible to reduce the possibility that the heat storage material leaks out of the system as the heat is stored, or the friction coefficient decreases due to interposition in the friction sliding surface. Furthermore, the possibility that the heat storage material phase-separates into a liquid phase and a solid phase or decomposes with heat storage can be reduced. Such characteristics are also desirable from the viewpoint of ease of kneading between the heat storage material and other components such as a binder.

<< Second Embodiment >>
The friction material composition according to the second embodiment of the present invention (hereinafter sometimes referred to as “second composition”) will be described below. The 2nd composition has the same composition as the 1st composition mentioned above except containing a specific kind of substance as a heat storage material. Therefore, in the following description, the heat storage material will be described in detail.

<Heat storage material>
An important characteristic required for the latent heat storage material is a large change in enthalpy accompanying the phase transition (that is, a large transition enthalpy). In addition to this, another important characteristic required for the heat storage material is high thermal conductivity.

  For example, in a friction material obtained by molding a friction material composition including a heat storage material having a small thermal conductivity, it is difficult to quickly conduct frictional heat generated on the friction sliding surface to other parts. . Accordingly, the frictional heat may exceed the amount of heat that can be stored by the heat storage material in the vicinity of the friction sliding surface. In this case, even if the heat storage material contained in the portion other than the vicinity of the friction sliding surface has not yet undergone phase transition and heat storage is possible, the frictional heat generated on the friction sliding surface is conducted to the heat storage material. As a result, the temperature difference between the vicinity of the frictional sliding surface and other portions becomes large. That is, the temperature in the vicinity of the frictional sliding surface locally increases, and the occurrence of the fade phenomenon cannot be reduced.

  On the other hand, in a friction material obtained by molding a friction material composition including a heat storage material having a large thermal conductivity, it is possible to quickly conduct frictional heat generated on the friction sliding surface to other parts. . Therefore, even if the friction heat exceeds the amount of heat that can be stored by the heat storage material in the vicinity of the friction sliding surface, the friction heat can be quickly conducted to the heat storage material included in a portion other than the vicinity of the friction sliding surface. Can do. As a result, the temperature difference between the vicinity of the frictional sliding surface and other portions is reduced. That is, the temperature in the vicinity of the frictional sliding surface can be prevented from rising locally, and the occurrence of the fade phenomenon can be more reliably reduced.

  As described above, in order to more reliably reduce the occurrence of the fade phenomenon, it is desirable that the heat storage material has a large thermal conductivity. In general, organic materials have a lower thermal conductivity than inorganic materials. From such a viewpoint, a heat storage material made of an inorganic material is more preferable than a heat storage material made of an organic material, and a heat storage material made of an inorganic oxide compound is more preferable.

<Constitution>
Therefore, in the second composition, the heat storage material is an inorganic oxide compound.
The inorganic oxide compound as the heat storage material contained in the second composition is not particularly limited as long as it is a substance that absorbs heat by the transition enthalpy accompanying the solid-solid phase transition. For example, a metal oxide and a plurality of kinds of metal elements Or a composite oxide containing

<effect>
As described above, the second composition contains an inorganic oxide compound as a heat storage material. As a result, the frictional heat generated on the frictional sliding surface can be quickly conducted to other parts, so that the temperature in the vicinity of the frictional sliding surface is prevented from rising locally, and the occurrence of a fade phenomenon is prevented. It can reduce more reliably.

<< Third Embodiment >>
The friction material composition according to the third embodiment of the present invention (hereinafter sometimes referred to as “third composition”) will be described below. The 3rd composition has the same composition as the 2nd composition mentioned above except containing a specific substance as a heat storage material. Therefore, in the following description, the heat storage material will be described in detail.

<Heat storage material>
As above-mentioned, the 2nd composition can reduce generation | occurrence | production of a fade phenomenon more reliably by including an inorganic oxide type compound as a heat storage material. As a result of intensive studies, the present inventor has found that a vanadium dioxide-based latent heat storage material (see, for example, Patent Document 3) can be used as such an inorganic oxide compound.

<Constitution>
Specifically, in the third composition, the heat storage material is a vanadium dioxide compound and / or LiVO ₂ represented by the following general formula (1).

In the general formula (1), M is an element having a tetravalent, pentavalent, or hexavalent valence. More specifically, M is an element that can have a tetravalent, pentavalent, or hexavalent valence, and may be an element that has a plurality of valences. Typically, M is a transition element. On the other hand, X is a numerical value that is 0 or more and less than 1. That is, in the third composition, the heat storage material may be vanadium dioxide or a composite oxide of vanadium (V) and another element (M). The other element (M) may be a single element or a combination of two or more kinds of elements. Further, the heat storage material may be LiVO ₂ . In addition, the heat storage material may be a combination of the vanadium dioxide compound and LiVO ₂ as described above.

  In the vanadium dioxide compound represented by the general formula (1), the ratio of the atomic composition of vanadium (V) and the other element (M) (ie, 1-X: X) and the other element (M) are selected. The type of element to be used is appropriately determined according to the heat storage characteristics to be achieved by the compound. That is, the heat storage characteristic of the compound can be adjusted by a combination of M and X. The “heat storage characteristic” referred to here refers to, for example, the magnitude of the endothermic amount of the compound and the maximum temperature (hereinafter sometimes referred to as “latent heat temperature”). In addition, the endothermic amount and latent heat temperature of the compound can be measured by, for example, differential scanning calorimetry (DSC: Differential Scanning Calorimetry).

<effect>
As described above, the third composition contains the vanadium dioxide compound represented by the general formula (1) and / or LiVO ₂ as a heat storage material. Thereby, the temperature rise at the time of use of the friction material obtained by shape | molding a 3rd composition can be reduced more reliably, and generation | occurrence | production of a fade phenomenon itself can be reduced more reliably. Further, by appropriately selecting the combination of M and X in the general formula (1), the heat storage characteristics (for example, the heat absorption amount and the latent heat temperature) of the heat storage material can be easily adapted to the intended application. Can be adjusted.

<< 4th Embodiment >>
The friction material composition according to the fourth embodiment of the present invention (hereinafter sometimes referred to as “fourth composition”) will be described below. The 4th composition has the same composition as the 3rd composition mentioned above except including the more desirable vanadium dioxide system latent heat storage material as a heat storage material. Therefore, in the following description, the heat storage material will be described in detail.

<Heat storage material>
As described above, in the third composition, the ratio of the atomic composition of vanadium (V) and the other element (M) in the vanadium dioxide compound represented by the general formula (1) (that is, 1-X : X) and the combination of the elements selected as the other elements (M) as appropriate, the heat storage characteristics of the heat storage material can be easily adjusted to suit the intended use. . Based on such knowledge, the present inventor has found a more preferable combination of M and X in the vanadium dioxide-based latent heat storage material as a result of intensive studies.

<Constitution>
Specifically, in the general formula (1), M is one or more elements selected from the group consisting of Cr, W, Mo, Nb, Ta, Os, Ir, Ru, and Re. On the other hand, X is a numerical value that is 0 or more and 0.5 or less.

<effect>
As described above, in the fourth composition, the “other element (M)” constituting the vanadium dioxide compound represented by the general formula (1) is selected from the specific element group described above. . Furthermore, it mix | blends so that the atomic composition ratio (namely, X) of the other element (M) with respect to the sum total of vanadium (V) and another element (M) may enter into the specific range mentioned above. As a result, the temperature rise during use of the friction material obtained by molding the fourth composition can be more reliably reduced, and the occurrence of the fade phenomenon itself can be more reliably reduced.

<< 5th Embodiment >>
By the way, the heat storage characteristic as the whole friction material is influenced not only by the heat storage characteristic of the heat storage material itself, but also by the content (mixing ratio) of the heat storage material in the heat storage material composition. As a result of diligent research, the present inventor has demonstrated that the friction material exhibits excellent heat storage characteristics when the content of the heat storage material in the friction material composition according to the present invention falls within a specific range, and further improves the various effects described above. It was found that it can be exhibited effectively.

<Constitution>
In view of the above, in the friction material composition according to the fifth embodiment of the present invention (hereinafter sometimes referred to as “fifth composition”), the content of the heat storage material in the entire friction material composition. Is 1% by mass or more and 60% by mass or less. When the said content rate is less than 1 mass%, since it becomes difficult to exhibit sufficient heat storage effect resulting from having mix | blended the heat storage material in a heat storage material, it is unpreferable. On the other hand, when the content is greater than 60% by mass, for example, the content of the binder in the entire friction material composition is relatively small, and it is difficult to maintain an integral shape as the friction material. Therefore, it is not preferable. In particular, since a heat storage material made of an inorganic oxide compound is often hard and brittle, if the content of the heat storage material in the entire friction material composition is excessive, the resulting friction material tends to be brittle.

<effect>
As described above, the fifth composition includes the heat storage material described above at a content of 1% by mass or more and 60% by mass or less with respect to the entire composition. Thereby, the heat storage material was blended while reducing the problem that the friction material obtained by molding the fifth composition became brittle or it was difficult to maintain the integral shape as the friction material. A sufficient heat storage effect due to the above can be exhibited.

<< 6th Embodiment >>
By the way, as stated at the beginning of the present specification, the present invention relates not only to the friction material composition described above but also to the friction material.

<Constitution>
The friction material according to the sixth embodiment of the present invention (hereinafter sometimes referred to as “sixth friction material”) includes various types of the present invention including the first composition to the fifth composition described above. It is a friction material formed by shape | molding the friction material composition which concerns on this embodiment.

<Production method>
As a method for producing the sixth friction material, among various production methods conventionally employed as a production method for the friction material, depending on various physical properties, sizes, shapes, etc. required for the friction material, You can choose. For example, a friction material composition obtained by mixing a reinforcing fiber material, a friction modifier, a binder, a lubricant, and a heat storage material is molded at a predetermined temperature and a predetermined pressure, and then predetermined The sixth friction material can be manufactured by thermoforming at a temperature of (for example, 160 ° C.) and further subjecting to heat treatment (for example, 210 ° C.) and finishing treatment.

<effect>
As described above, the sixth friction material is a friction material formed by molding the friction material composition according to various embodiments of the present invention. Thereby, the temperature rise at the time of use of a 6th friction material can be reduced, and generation | occurrence | production of fade phenomenon itself can be reduced. As a result, for example, a reduction in friction coefficient (that is, a reduction in braking force) due to thermal decomposition of resin and / or other organic components as a binder is reduced, or thermal decomposition of organic fibers as a reinforcing fiber material. It is possible to reduce the shortening of the lifetime (that is, the shortening of the service life) due to.

<< 7th Embodiment >>
By the way, as described at the beginning of the present specification, the present invention relates not only to the friction material composition and the friction material as described above but also to the friction member.

<Constitution>
The friction member according to the seventh embodiment of the present invention (hereinafter sometimes referred to as “seventh member”) is a friction member according to various embodiments of the present invention including the above-described sixth friction material. A friction member made of a material and a back metal.

<effect>
As described above, the seventh friction member is a friction member including the friction material and the back metal according to various embodiments of the present invention. Therefore, similarly to the sixth friction material, it is possible to reduce the temperature rise when the seventh friction member is used, and to reduce the occurrence of the fade phenomenon itself. As a result, the same effect as the sixth friction material can be achieved.

  The sixth friction material and the seventh friction member can be used as friction materials in brake pads, brake linings, clutch facings, and the like used in, for example, industrial machines, railway vehicles, luggage vehicles, and passenger cars.

<Preparation of friction material composition sample>
In this test, various friction material composition samples having a simplified composition compared to a general friction material composition were prepared. Specifically, Table 1 lists aramid fibers as a reinforcing fiber material, barium sulfate as a friction modifier, phenol resin as a binder, and various vanadium dioxide compounds as heat storage materials having different latent heat temperatures. It was weighed so that the content ratio (mixing ratio) would be. These raw materials were uniformly mixed in a Henschel mixer for 10 minutes to prepare various friction material composition samples.

  As shown in Table 1, for the friction material composition samples according to Examples 1 to 3, each of the heat storage materials having latent heat temperatures of 198 ° C., 123 ° C. and 68 ° C. was 38.7% by mass. Blended. For the friction material composition samples according to Example 4 and Example 6, 49.6% by mass, 59.6% by mass, and 2.9% by mass, respectively, of a heat storage material having a latent heat temperature of 68 ° C. . Furthermore, no heat storage material was added to the friction material composition sample according to Comparative Example 1.

<Preparation of friction material sample>
Each of the various friction material composition samples described above is put into a mold and warm-formed at a pressure of 25 MPa and a temperature of 160 ° C. for 5 minutes to obtain a cylindrical shaped body having a diameter of 10 mm. It was. And the friction material sample which concerns on the Example 1 thru | or Example 6 and the comparative example 1 which were mentioned above was prepared by taking out the said molded object from a metal mold | die, and subjecting it to heat processing over 3 hours at the temperature of 210 degreeC, respectively.

《Heat storage characteristics of friction material sample》
The heat storage characteristics were measured for each of the various friction material samples obtained as described above. Specifically, about 10 mg of a sample cut from each friction material sample is sealed in a measurement pan, and a high sensitivity differential scanning calorimeter DSC8230 manufactured by Rigaku Corporation is used in a temperature range of 30 ° C. to 250 ° C. The temperature was raised and differential scanning calorimetry (DSC) was performed.

  In this example, the total endotherm [J], which is the integrated value of the endothermic peaks caused by the endotherm due to the transition enthalpy over the above temperature range, is measured, and the endotherm per unit mass [g] of each sample [J] / G] was calculated and used as an index of heat storage characteristics. As the heat absorption amount increases, the heat storage material absorbs the frictional heat generated during use as a friction material, so that the temperature rise of the friction material can be reduced, and the occurrence of a fade phenomenon can be reduced. As a result, various problems caused by the temperature rise of the friction material can be reduced.

<Mechanical strength of friction material sample>
Furthermore, the mechanical strength of each of the various cylindrical friction material samples obtained as described above was measured. Specifically, a cylindrical sample having a length of 20 mm was cut out from each friction material sample, and a compression test was performed using Autograph AG-Xplus manufactured by Shimadzu Corporation in accordance with JIS K7181. In this example, the maximum load (compressive stress) in the compression process was determined as the compressive strength (compressive strength) [MPa] and used as an index of mechanical strength.

<Evaluation of friction material sample>
The test results for the heat storage characteristics (heat absorption amount) and mechanical strength (compressive strength) of each friction material sample are also listed in Table 1 above. Regarding the heat storage characteristics (heat absorption amount), in the friction material samples according to Examples 1 to 6, heat storage (heat absorption) due to the blending of the heat storage material is observed, and an effect of reducing the temperature rise of the friction material is expected. In addition, from the relationship between the type and content of heat storage agent blended in these friction material samples and the amount of heat absorbed, the latent heat temperature and the amount of heat absorption can be adjusted according to the type and content of the heat storage agent blended. It was also confirmed that it was possible. On the other hand, in the friction material sample according to Comparative Example 1 in which no heat storage material was blended, as a matter of course, heat storage (heat absorption) due to the transition enthalpy due to the blending of the heat storage material was not observed, and the temperature of the friction material was increased. It cannot be expected to reduce the effect.

  As for the mechanical strength (compressive strength), in any of the friction material samples according to Examples 1 to 6 and Comparative Example 1, the compressive strength changed according to the content ratios of the reinforcing fiber material and the binder. Specifically, in any of the friction material samples according to Example 4 and Example 5 in which the content ratios of the reinforcing fiber material and the binding material are small (less) compared to the friction material samples according to Example 1 to Example 3. A smaller (lower) compressive strength was observed. However, there is no practical problem with respect to the compressive strength observed in the friction material samples according to Example 4 and Example 5. On the other hand, compared with the friction material samples according to Examples 1 to 3, the content ratios of the reinforcing fiber material and the binding material are large (large), and any friction material sample according to Example 6 is larger (high). Compressive strength was observed.

  From the above results, by appropriately adjusting the contents of the heat storage agent, the reinforcing fiber material and the binder constituting the friction material, the heat storage characteristics and mechanical strength of the friction material are suitably balanced, It was confirmed that a friction material having characteristics suitable for the intended use can be provided.

In this example, various vanadium dioxide compounds were employed as heat storage materials as described above. However, in the friction material composition according to the present invention, as described above, a combination of one or more compounds selected from various vanadium dioxide compounds and LiVO ₂ or LiVO ₂ is employed as a heat storage material. Also good.

  Although several embodiments and examples having specific configurations have been described above for the purpose of describing the present invention, the scope of the present invention is limited to these exemplary embodiments and examples. It should be understood that modifications should be made as appropriate within the scope of the claims and the description of the specification.

Claims (7)

A friction material composition comprising a reinforcing fiber material, a friction modifier, and a binder,
A material that absorbs heat by a transition enthalpy accompanying a solid-solid phase transition is further included as a heat storage material
Friction material composition. The friction material composition according to claim 1,
The heat storage material is an inorganic oxide compound.
Friction material composition. The friction material composition according to claim 2,
The heat storage material is a vanadium dioxide compound and / or LiVO ₂ represented by the following general formula (1):

In the general formula (1), M is an element having a tetravalent, pentavalent, or hexavalent valence, and X is a numerical value that is 0 or more and less than 1.
Friction material composition. The friction material composition according to claim 3,
In the general formula (1), M is one or more elements selected from the group consisting of Cr, W, Mo, Nb, Ta, Os, Ir, Ru, and Re, X is 0 or more and 0. A numerical value that is 5 or less,
Friction material composition. The friction material composition according to any one of claims 1 to 4,
The content of the heat storage material in the entire friction material composition is 1% by mass or more and 60% by mass or less.
Friction material composition.   A friction material obtained by molding the friction material composition according to any one of claims 1 to 5.   A friction member comprising the friction material according to claim 6 and a back metal.