JP4014237B2 - Brake sliding part - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a brake sliding portion formed of a carbon fiber reinforced carbon composite material (hereinafter referred to as C / C composite material) that has excellent strength, friction, and sliding characteristics and also has good thermal conductivity.
[0002]
[Prior art]
A general brake material has a function of converting kinetic energy into heat energy by friction-joining a rotating body and a fixed body, and decelerating and further stopping a moving object.
In recent years, due to the increase in weight due to higher speed and larger size, C / C composite materials have been put to practical use on many airplanes due to their excellent thermal conductivity, large heat capacity, high strength, etc., especially as aircraft brake materials. It is becoming like this.
[0003]
In general, a C / C composite material is obtained by impregnating or mixing a long or short carbon fiber such as PAN, pitch, or rayon with a thermosetting resin such as phenol resin or furan resin or a thermoplastic resin such as pitch. It is manufactured by calcining a heat-molded product in a non-oxidizing gas atmosphere, further densifying and graphitizing.
[0004]
[Problems to be solved by the invention]
The characteristics desired as the C / C brake material are a material having a braking ability capable of stopping within a first defined stopping distance, that is, a material having an appropriate friction coefficient.
Secondly, it is desirable that an excessive braking torque value is generated at the time of braking, so that it does not have a property that does not cause a so-called cracking effect or impose an excessive load around the brake material. That is, it is a material that does not have an excessive friction coefficient and that has an appropriate instantaneous friction coefficient.
[0005]
Third, it is necessary that the amount of wear is small. The C / C composite material is composed of matrix carbon and carbon fiber, but when used as a brake material, the carbon fiber or matrix carbon is worn away by peeling off from the sliding surface. Is to greatly improve the service life of the brake.
Fourth, when assembled as a brake assembly and braked, it has sufficient compressive strength (compressive strength in a direction parallel to the sliding surface) to withstand compressive stress applied to the mounting portion.
Finally, it is necessary that the heat capacity and the thermal conductivity in the direction parallel to the sliding surface be large so that the temperature of the brake disk does not rise excessively due to the heat generated by the sliding.
[0006]
[Means for Solving the Problems]
Accordingly, the inventors have repeatedly studied eagerly to solve the above-described problems, and as a result, the brake sliding portion comprising a stator and a rotor made of an annular disk-shaped C / C composite material formed of a carbon fiber reinforced carbon composite material. Because
(1) Using an inertia friction tester, a test piece consisting of a rotor having an average sliding surface diameter of 83.5 mm and a stator is fixed to a holder, and the rotor rotated at a sliding surface speed of 22 m / s is brake pressure. When the sliding surface pressure is 150 psi , the average friction coefficient is 0.18 to 0.26.
Braking initial instantaneous dynamic friction coefficient of the time the brake pressure reaches the set value, 0.35 or less (2) when slid in the same manner, the amount of wear, 3 × 10 ^-4 mm / dose / surface the following (3) annular disc rotor and compressive strength in the direction parallel to the sliding surface of the stator, 10 kg / mm ² or more on
It has become known what is.
[0007]
Hereinafter, the present invention will be described in detail.
As the carbon fibers used in the present invention, pitch-based carbon fibers can be used, but desirably, the carbon fiber has a tensile modulus of 10 to 25 t / mm ² and is 1600 in an inert gas atmosphere. It is more desirable if it has the property that the tensile modulus is converted to 50 t / mm ² or more when fired at ˜2000 ° C.
[0008]
The form of carbon fiber used is in the form of tows, strands, rovings, yarns, etc. made of a plurality of single fibers, and it is preferable to use short fibers obtained by cutting them. These short fibers are formed from a bundle of a plurality of single fibers, and in the present invention, short fibers of about 0.3 to 100 mm, preferably about 5 to 50 mm are used. When the C / C composite material is used, the short fibers are opened and dispersed to produce a sheet in which single fibers are randomly oriented two-dimensionally (two-dimensional random), and a matrix material is filled between carbon fibers. It is preferable.
[0009]
Here, as a specific production method for producing the two-dimensional random sheet by dry-opening the short fibrous carbon fiber, for example, a carbon fiber is mechanically monofilamentated in spinning, and a sheet is produced. There is a method of manufacturing a sheet by using a random weber or by opening with air.
[0010]
Further, as a method of producing a two-dimensional random sheet by wet-opening the short fibrous carbon fiber, for example, using a beater or pulper that is usually used for beating treatment of pulp or the like, After opening the short carbon fibers in a solvent, for example, supply them little by little to a form having a screen at the bottom, or evenly disperse by means such as stirring after opening, and after making paper with a wire mesh etc., dry The method of making it is mentioned. As the solvent for uniformly dispersing the short-fiber carbon fibers, water, acetone, alcohol anthracene oil having 1 to 5 carbon atoms or the like can be preferably used, but other organic solvents may be used. In addition, it is preferable to disperse or dissolve phenol resin, furan resin, pitch, or the like in the solvent, because the carbon fibers are adhered to each other, and handling in the next process becomes easier. Furthermore, it is preferable to add a thickener such as sodium fibrin glycolate, polyvinyl alcohol, or hydroxycellulose to the solvent because the effect is further increased.
[0011]
As the basis weight (weight per 1 m ² ) of the two-dimensional random sheet, various materials can be taken depending on the purpose, but 10 to 500 g / m ² is optimal in consideration of handling property, impregnation property, and uniformity.
The two-dimensional random sheet thus obtained is impregnated with a matrix such as phenol resin, furan resin, petroleum-based or coal-based pitch and then dried. At that time, the matrix used is one that is dissolved in a solvent such as alcohol, acetone, anthracene oil or the like and adjusted to an appropriate viscosity.
[0012]
Next, the dried sheets are laminated and filled in a mold according to the purpose, and pressure-molded in a temperature range of 100 to 500 ° C., and Vf (carbon fiber content) = 5 to 65%, preferably 10 A molded body of about -65%, more preferably about 35-50% is obtained. After that, through primary firing in which the temperature is raised to 800 to 2200 ° C., preferably 1800 to 2200 ° C. at an increase rate of 1 to 200 ° C./hr in an inert gas atmosphere such as N ₂ gas, the C / C composite Get the material.
[0013]
The fired C / C composite material has a large number of voids, and cannot be put into practical use as it is. Therefore, in the present invention, in order to reduce the voids, a densification process by CVD is performed, and then a densification process is performed using pitch or resin as a matrix.
[0014]
In the densification process by CVD, the C / C composite material placed in the reactor is heated by induction heating coil or resistance heating, and the like, and the vapor of hydrocarbons such as methane or propane or halogenated hydrocarbons. Is impregnated into the voids with pyrolytic carbon produced by supplying H ₂ gas, Ar gas or N ₂ gas into the reactor.
[0015]
In the densification treatment with pitch or resin, the tank on which the C / C composite material after the densification treatment by CVD is heated to a predetermined temperature, the inside of the tank is evacuated, and then the melted pitch or resin is supplied and pressurized. So that the voids are impregnated. Thereafter, baking is performed at a temperature of 700 to 2100 ° C., preferably 700 to 1000 ° C. The densification process of the target C / C composite material is performed by repeating the densification process such as impregnation and firing of the pitch or resin. Furthermore, a graphitization process can be performed as needed.
[0016]
The densification treatment is performed until the volume is increased by 10 to 35%, preferably 10 to 25% by the densification treatment by CVD. Next, densification is performed until the bulk density is normally 1.60 to 1.80, preferably 1.65 to 1.75, by a densification treatment by impregnation and firing of pitch or resin.
[0017]
When the final heat treatment is performed after the densification treatment, the bulk density after the final heat treatment is 1.60 to 1.80, preferably 1.65 to 1.75. The final heat treatment temperature is 1400 to 2100 ° C, preferably 1500 to 1800 ° C.
[0018]
The C / C composite material thus produced has a hardness measured with a Rockwell hardness meter of 70 to 125 HRP, preferably 85 to 120 HRP, and Vf (volume content of carbon fiber) of 10 to 50%. Preferably it is 30 to 45%.
The compressive strength 10 Kg / mm ² or more, preferably 12 Kg / mm ² or more, the thermal conductivity of 30 W / m · K or more, preferably 35W / m · K or more, more preferably 40W / m · K or more.
The brake sliding portion obtained by manufacturing and combining the annular disk rotor and the stator using the C / C composite material thus manufactured has an average friction coefficient of 0.18 to 0.26, preferably 0. 19 to 0.24, instantaneous dynamic friction coefficient is 0.35 or less, wear amount is 3 × 10 ⁻⁴ mm / turn / surface, preferably 2 × 10 ⁻⁴ mm / turn / surface or less, and excellent performance It is what you have.
[0019]
Below, the evaluation method of a C / C composite material is demonstrated.
(Brake performance test) Using an inertia friction tester, a test piece (average sliding surface diameter 83.5 mm) consisting of a fixed disk (stator) and a rotating disk (rotor) formed of a C / C composite material Affix to the holder and slide against each other to perform the friction test (FIG. 1).
Test conditions were as follows: brake pressure (as sliding surface pressure) 150 psi, sliding surface speed = 22 m / s (absorbed energy per unit area E = 2.0 × 10 ³ J / cm ² ), average friction coefficient, brake Measure the instantaneous friction coefficient and wear amount at the beginning of braking (until the time when the brake pressure reaches the set value).
(Strength) Measured according to JIS-K7208.
(Thermal conductivity) Measured using a laser flash method in accordance with JIS-R1611.
[0020]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to an Example, unless the summary is exceeded.
[0021]
Example 1
Pitch-based carbon fiber ("Dialead" K321 manufactured by Mitsubishi Chemical Corporation) cut to a length of 30 mm was dry-opened to obtain a 300 g / m ² carbon fiber sheet that was two-dimensionally randomly oriented. The sheet was impregnated with a phenol resin diluted with ethanol and then dried to prepare a sheet impregnated with a phenol resin having a basis weight of 580 g / m ² . This sheet was laminated in a mold and pressure molded at 280 ° C. to obtain a molded body with Vf≈42%. This molded body is first fired at 2000 ° C. and then subjected to the above-described densification treatment by CVD (CVD volume% ≈17%), followed by impregnation with resin and firing at 1000 ° C. in an inert atmosphere to carbonize. The annular disk rotor and stator made of a C / C composite material having a bulk density of approximately 1.70, Vf of approximately 40%, and Rockwell hardness of 93 to 104 HRP are performed by repeating the densification process multiple times and performing a final heat treatment at 1600 ° C. Obtained. A brake sliding part was manufactured by combining the obtained annular disk rotor and stator.
[0022]
When the performance test of this brake sliding part was conducted, the average friction coefficient 0.20: instantaneous friction coefficient 0.31, wear amount 1.0 × 10 ⁻⁴ mm / time / surface, thermal conductivity 44 W / m · K As a result, a compressive strength of 13.4 kg / m ² was obtained.
[0023]
(Comparative Example 1)
A green body similar to that in Example 1 was subjected to primary firing under the same conditions, followed by densification treatment using only the pitch and final heat treatment under the same conditions as in Example 1. Bulk density≈1.72, Vf≈40%, lock A C / C composite material having a well hardness of 100 to 110 HRP was obtained, and a brake sliding part was manufactured.
[0024]
When the performance test of this brake sliding part was conducted, the average friction coefficient was 0.25, the instantaneous friction coefficient was 0.39, the wear amount was 3.3 × 10 ⁻⁴ mm / time / surface, and the thermal conductivity was 60 W / m · K. The compressive strength was 17.7 kg / mm ^2, and although the compressive strength and thermal conductivity were improved as compared with Example 1, the friction and wear characteristics were greatly inferior.
[0025]
(Comparative Example 2)
A PAN-based carbon fiber (Toray "Torca" T300 manufactured by Toray) was impregnated with a phenol resin, dried, cut to a length of 30 mm, filled into a mold, pressed into a mold, and pressure-molded at 280 ° C. ≈40% molded body was obtained. This molded body is first fired at 2000 ° C., and then subjected to the above-mentioned densification treatment by CVD (CVD volume% ≈20%), subsequently impregnated with pitch, and fired at 1000 ° C. in an inert atmosphere for carbonization. The final heat treatment at 1600 ° C. is repeated a plurality of times to obtain a C / C composite material having a bulk density of 1.68, Vf of 40%, and Rockwell hardness of 100 to 110 HRP, and the brake sliding portion is Manufactured.
[0026]
When the performance test of this brake sliding part was conducted, Vf and Example 1 had the same hardness, but the average friction coefficient was 0.22, the instantaneous friction coefficient was 0.37, and the wear amount was 6.8 × 10 ^−4. Compared to Example 1, the results were significantly inferior to Example 1 in mm / time / surface, thermal conductivity of 20 W / m · K, and compressive strength of 9.8 kg / mm ² .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a test method for a brake material used in the present invention.
[Explanation of symbols]
1 Rotor disk 2 Stator disk

Claims (2)

A brake sliding portion composed of an annular disk rotor and a stator formed of a carbon fiber reinforced carbon composite material,
(1) Using an inertia friction tester, a test piece consisting of a rotor having an average sliding surface diameter of 83.5 mm and a stator is fixed to a holder, and the rotor rotated at a sliding surface speed of 22 m / s is brake pressure. When the sliding surface pressure is 150 psi , the average friction coefficient is 0.18 to 0.26.
Braking initial instantaneous dynamic friction coefficient of the time the brake pressure reaches the set value, 0.35 or less (2) when slid in the same manner, the amount of wear, 3 × 10 ^-4 mm / dose / surface (3) A brake sliding portion characterized by being a carbon fiber reinforced carbon composite material having a compressive strength in a direction parallel to the sliding surfaces of the annular disk rotor and the stator of 10 kg / mm ² or more.   The brake sliding portion according to claim 1, wherein the annular disk rotor and the stator have a thermal conductivity in a direction parallel to the sliding surface of 35 W / m · K or more.

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