JPH09170629A - Carbon fiber reinforced carbon type sintered body clutch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a clutch which has a durability to bear a high load and a high temperature, by making a carbon crystal sedimentary layer at a specific thickness, and the strength ratio at a specific value of peak of the Raman spectrum within a specific scope. SOLUTION: The thickness of a carbon crystal sedimentary layer Lc indicates the lamination of a carbon layer in the layer structure in a C/C composite, and the Lc is made 2 to 70nm, favorably 10 to 40nm. On the other hand, by the Raman spectrum, the existing ratio of the carbon forming a layer structure, and the carbon forming no layer structure in the C/C composite, can be known. As a result, a Raman band near 1,360cm<-1> indicates the existence of an amorphous form carbon, while the Raman band near 1,600cm<-1> indicates the existence of a graphite crystal structure. The strength ratio of the peak of the Raman spectrum near 1,360cm<-1> , and the peak near 1.600cm<-1> , is specified as 0.4 to 0.9.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a clutch mounted on a vehicle.

[0002]

2. Description of the Related Art Up to now, a paper material containing cellulose as a main component has been used as a wet friction clutch facing material. However, a facing material that can withstand high temperatures has been desired. In response to this, Japanese Patent Application Laid-Open No. 4-76085 proposes a differential limiting device in which a friction surface of a friction plate is improved by using a carbon fiber reinforced carbonaceous composite so as to withstand high load and high temperature. There is. But,
Since carbon fiber reinforced carbonaceous composites generally have high density and few pores, when this is used for the friction plates, it is difficult to remove the lubricating oil when the friction plates are in close contact with each other, and the dynamic friction coefficient becomes low. is there. Although carbon fiber reinforced carbonaceous composites have a proven track record in applications such as brake discs for races, when used as wet clutch facings, low-temperature fired ones are difficult to use because of their hardness. However, there is a problem in that the workability is poor, and the friction plate of the other party to be engaged wears down when used for a long time, resulting in poor durability. On the contrary, the high-temperature fired product has a problem that it is easily worn and the manufacturing cost becomes high.

[0003]

The present invention has been made against the background of the above-mentioned conventional technical problems and has a durability capable of withstanding a high load and a high temperature and functions as a solid lubricant. The object of the present invention is to obtain a clutch having a friction plate which has appropriate softness and has a large number of pores and is excellent in heat conductivity in oil.

[0004]

According to the present invention, a first friction plate and a second friction plate are disposed so as to be superposed on each other, and the first friction plate and the second friction plate are opposed to each other. The carbon fiber reinforced carbonaceous sintered body is integrally engaged with two rotatable members in the rotational direction, and at least one of the friction surfaces of the first friction plate and the second friction plate has at least one friction surface. In the clutch constituted by, the carbon fiber reinforced carbonaceous composite has a carbon crystal deposition layer thickness Lc of 2 to 70 nm, preferably 10 to 40.
and Raman spectrum of 1,360 cm ^-1
Carbon fiber reinforced carbonaceous material having an intensity ratio R [I _1,360 / I _1,600 ] of a peak in the vicinity of 1600 cm ⁻¹ of 0.4 to 0.9 and a porosity of 22 to 60% The present invention provides a carbon fiber reinforced carbonaceous sintered body clutch, which is characterized by being composed of a bonded body (hereinafter, referred to as "C / C composite").

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the clutch of the present invention, the first
At least one of the friction plate and the second friction plate of
It is composed of C / C composite. One of the features of the present invention is to control the graphitization degree of the C / C composite that constitutes the friction plate of the clutch, in order to control the thickness Lc of the carbon crystal deposition layer and the Raman spectrum near 1,360 cm ^-1 . It is defined by the intensity ratio R [I _1,360 / I _1,600 ] of the peak and the peak in the vicinity of _1,600 cm ⁻¹ .

The thickness Lc of the carbon crystal deposition layer indicates the stacking of carbon layers in the layer structure in the C / C composite. In the present invention, Lc is 2 to 70 nm
And preferably 10 to 40 nm. When the thickness Lc of the carbon crystal deposition layer is less than 2 nm, the C / C composite does not have sufficient softness as a solid lubricant, and the aggressiveness to the mating material is remarkable. On the other hand, if it exceeds 70 nm,
Interlayer slippage causes peeling between layers, resulting in poor wear resistance, easy clogging of the friction surface, and poor durability. In addition, Lc can be usually obtained from the half width obtained from X-ray diffraction precision measurement.

On the other hand, the Raman spectrum shows the abundance ratio of carbon forming a layered structure and carbon not forming a layered structure in the C / C composite. That is, 1,360
The Raman band in the vicinity of cm ⁻¹ is considered to be due to Raman activation due to the decrease or loss of the symmetry of the hexagonal lattice due to structural defects. Therefore, the Raman band near 1,360 cm ^-1 indicates the presence of amorphous carbon. on the other hand,
It is considered that the Raman band near 1,600 cm ^-1 is due to Raman-active double degenerate vibration, which is only one of the three vibration modes of the two-dimensional hexagonal lattice forming the plane of the graphite layer. Therefore, 1,600 cm ^-1
Raman bands in the vicinity indicate the presence of the graphite crystal structure. Further, since the intensity of each Raman band represents its abundance ratio, the intensity ratio R [I _1,360 / I _1,600 ] of the peak in the vicinity of _1,360 cm ^{−1 and} the peak in the vicinity of _1,600 cm ^{−1 of} the Raman spectrum is It can be used as a parameter indicating the ratio of the layer structure and the graphite crystal structure. FIG.
The Raman spectrum charts of various carbons and their intensity ratios R are illustrated in FIG.

In the present invention, the Raman spectrum of 1,36
0cm peak intensity ratio of the vicinity of the peak and 1,600Cm ^-1 near ^-1 0.4 The R [I _1,360 / I _1,600]
It is defined as 0.9. Intensity ratio R [I _1,360 / I _1,600 ]
However, if it is less than 0.4, the C / C composite becomes too soft, and the abrasion of the disc itself due to friction increases more than necessary. On the other hand, if it exceeds 0.9, the carbon particles in the C / C composite become large. It becomes easy to fall off, and the aggression to the opponent material increases. Furthermore, the intensity ratio R [I _1,360 / I _1,600 ]
Is more preferably 0.5 to 0.7.

One of the features of the present invention is to define the porosity of the C / C composite constituting the friction plate of the clutch, improve the thermal conductivity of the friction plate of the wet clutch, and prevent the deterioration of the lubricating oil. At the same time, it is necessary to secure an escape port for the lubricating oil when the friction plates are in close contact with each other. That is, although the graphite crystal itself has very good thermal conductivity, when the graphite crystal structure has a disordered layer structure and surrounds the graphite crystal structure as in the C / C composite of the present invention, the thermal conductivity is high. Is lowered, and it becomes difficult to quickly lower the temperature of the friction plate surface. By the way, the lubricating oil moves in and out of the pores of the friction plate, so that the lubricating oil itself serves as a heat medium,
Lower the temperature of the friction plate surface. Therefore, the apparent thermal conductivity of the C / C composite can be improved by increasing the porosity.

The pores serve as escape ports for the lubricating oil when the friction plates are brought into close contact with each other. Therefore, the presence of the pores prevents the lubricating oil from remaining between the friction plates and obstructing the close contact between them. If the lubricating oil remains between the friction plates when the friction plates are in close contact, the so-called μ
The characteristics deteriorate.

In the present invention, the porosity of the C / C composite is specified as 22 to 60%. If the porosity is less than 22%, the temperature of the friction plate surface cannot escape, and the lubricating oil deteriorates. Moreover, since there is not enough capacity as an escape port for the lubricating oil, clogging of the pores easily occurs, On the other hand, 6
If it exceeds 0%, the strength of the C / C composite decreases, and it is easily damaged. A more preferable porosity is 31 to 50%.

The method for measuring the porosity is not particularly limited, but the porosity can be measured by, for example, the mercury penetration method. The mercury porosimetry method calculates the porosity by the pressure applied to mercury and the amount of mercury that has penetrated into the pores due to the pressure. Here, the relationship between the pressure applied to the mercury and the minimum pore diameter that allows the mercury to enter the pores is expressed by the following Washburn equation (I). P · D∝-4σ cos θ (I) [wherein, P is applied pressure, D is pore diameter, σ is surface tension of mercury, and θ is contact angle of mercury with respect to sample. ] That is, the pressure applied to mercury is in inverse proportion to the pore diameter that mercury can invade, and if pressure is successively applied, it will penetrate even finer pores, and the pore diameter is unique. Can be determined. On the other hand, the amount of mercury that has entered the pores by pressurization, that is, the amount of press-fitting, is the total volume of the pores. Therefore, the relationship between the pore diameter and the pore volume, that is, the pore distribution becomes clear.

A method for producing a C / C composite having the above graphitization degree and porosity will be described below.
The C / C composite in the present invention is a sintered body of a carbon fiber reinforced carbonaceous composite. In the present invention, the carbon fiber reinforced carbonaceous composite is composed of a carbonaceous aggregate forming a carbon matrix, a carbonaceous binder and carbon fibers.

A carbon matrix having no softening point and having a volatile content of 20% by weight or less is applied. In particular, in order to maintain the strength of the composite,
Those having self-sintering property are preferable. The carbon matrix may be either petroleum-based or coal-based, but coal pitch-based is preferable from the viewpoint of carbonization yield. The particle size of the carbon matrix is preferably 2 to 150 μm.

The carbon fiber is for ensuring the strength of the C / C composite which is a sintered body of the carbon fiber reinforced carbonaceous composite.

The fiber length of the carbon fibers is not particularly limited and may be short fibers or long fibers.
Preferably 0.03 to 50 mm, more preferably 1 to 3
Short fibers of 0 mm are good. If the fiber length is less than 0.03 mm, the strength of the C / C composite cannot be secured, while if it exceeds 50 mm, the fibers are entangled with each other and the dispersibility may be reduced. The fiber diameter is preferably 5 to 25 μm, particularly preferably 7 to 15 μm. If the fiber diameter is less than 5 μm, the desired porosity and porosity cannot be obtained. On the other hand, if the fiber diameter exceeds 25 μm, the mechanical properties of the reinforcing fiber become insufficient.

The proportion of carbon fibers in the carbon fiber reinforced carbonaceous composite is preferably 10 to 70% by weight, and further 20
-40% by weight is more preferable. The ratio of carbon fiber is 10
If it is less than wt%, the strength and friction and wear properties as a material cannot be maintained, while if it exceeds 70 wt%, it becomes brittle as a material and it may be difficult to maintain a desired shape.

Examples of the binder of the carbon matrix and the carbon fiber include carbon powder, phenol resin powder, petroleum-based or coal-based pitch-based powder, and carbon powder and coal-based pitch-based powder are particularly preferable. Since the carbon yield of the phenol resin powder is particularly low, it is necessary to repeat the dipping step, and further, the phenol resin powder is abruptly softened during the subsequent sintering, so that the C / C composite having a desired shape may not be obtained.

It is preferable that the carbon powder has self-sinterability and is not carbonized or is not carbonized sufficiently. By using the carbon powder having the self-sintering property as the binder, a dense matrix can be formed by firing once. The carbon powder may be petroleum-based or coal-based, and examples thereof include mesocarbon microbeads, bulk mesophase crushed products, and low temperature calcined coke crushed products. Among them, petroleum-based and / or coal-based mesocarbon microbeads are preferable from the viewpoint of particle size, composition uniformity, and stability, and coal-based mesocarbon microbeads are more preferable from the viewpoint of carbonization yield.

The particle size of the carbon powder is preferably 2 to 150 μm. If the particle size is less than 2 μm, the dispersibility is reduced and a homogeneous matrix cannot be obtained, while if it exceeds 150 μm, a dense matrix cannot be obtained.

The content of the binder is preferably 30 to 80% by weight, and more preferably 42 to 75% by weight, based on the carbon fiber reinforced carbonaceous composite. When the content is less than 30% by weight, sufficient porosity cannot be obtained. On the other hand, when the content exceeds 80% by weight, the porosity of the matrix increases and the carbon fiber content decreases, so that a composite material is obtained. Cannot obtain sufficient strength.

In the present invention, the C / C composite is produced by mixing the above-mentioned carbon matrix, carbon fiber and binder, molding this to form a carbon fiber reinforced carbonaceous composite, and then firing. The mixing method is not particularly limited, and can be performed by a conventional method, for example. The molding method is also not particularly limited, but, for example, 0.
Pressure molding of 05 to ² t / cm ² is suitable. In addition, cold isostatic pressing (CIP), hot isostatic pressing (H
IP) or hot pressing method can also be used.
The molding temperature can be 600 ° C. or lower in the air and 1,000 ° C. or lower in an inert atmosphere.

The carbon fiber reinforced carbonaceous composite obtained by molding is sintered into a C / C composite. By sintering, the uncarbonized portions of the carbon fibers and carbon powder contained in the carbon fiber reinforced carbonaceous composite undergo carbonization and solidification,
Part is graphitized. Sintering is 700-2,800 ° C,
It is preferable to carry out for 0.5 to 24 hours, especially 1,000
It is more preferable to carry out at 2,500 ° C. for 2 to 12 hours. If the sintering temperature is less than 700 ° C, a C / C composite having a desired degree of graphitization cannot be obtained, while 2,800
If the temperature exceeds ℃, the hardness of the matrix decreases and the amount of wear increases. Further, the sintering is preferably performed in a non-oxidizing atmosphere such as nitrogen gas or argon gas.

In the clutch of the present invention, both the first friction plate and the second friction plate may be made of the above-mentioned C / C composite, or one of them may be made of the C / C composite. . Further, even if the first friction plate and / or the second friction plate is entirely composed of the above-mentioned C / C composite, only the part which becomes the sliding surface is composed of the C / C composite, and the part responsible for the strength. For example, the back plate portion can be made of a structural material such as metal, resin, or ceramics. Even if the first friction plate and the second friction plate are directly formed into a predetermined shape by the above-mentioned method and sintered to form a block-shaped C / C composite, and then formed into a predetermined shape. It may be created by machining. In the clutch of the present invention, the parts other than the first friction plate and the second friction plate may be the same as those of the conventional clutch.

[0025]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, unless otherwise specified, the following parts and% are based on weight.

Examples 1 to 8 and Comparative Examples 1 to 5 Coal coke powder [MPC-1 manufactured by Mitsubishi Chemical Co., Ltd.] as a carbon matrix, PAN-based carbon fiber [φ10 μm manufactured by Toray Industries, Inc. as a carbon fiber, T -300], as a binder, self-sintering coal pitch-based carbon powder [φ10μ
m, manufactured by Mitsubishi Chemical Co., Ltd., TGP], dry-blended according to the formulation shown in Tables 1-2, hot-press molded in the atmosphere at 500 ° C., sintered in a nitrogen atmosphere, and C / C
Got a composite.

With respect to the obtained C / C composite, the thickness Lc of the crystal deposition layer and the Raman spectrum of 1,360 c
The intensity ratio R [I _1,360 / I _1,600 ] and the porosity of the peak near m ^{−1 and} the peak near _1,600 cm ⁻¹ were measured. At this time, the measurement was performed by the following method. The thickness Lc of the crystal deposition layer was determined from the half width of the chart of the precise measurement using the standard silicon sample of the X-ray diffraction of the crushed C / C composite. The intensity ratio R is the ratio of the intensity of the peak in the vicinity of 1,360 cm ^{-1 to} the intensity of the peak in the vicinity of 1,600 cm ^{-1 of} the Raman spectrum. Regarding the porosity, a mercury porosimeter (Shimadzu Corporation) is used for C / C composites cut into appropriate sizes.
Manufactured by Poisizer 9320), and determined by mercury porosimetry.

Next, a C / C composite is formed to have a thickness of 3 mm,
A first friction plate processed into the shape of a friction plate having an outer diameter of 127 mm and an inner diameter of 108 mm, and an SPC28 processed into the same shape.
And a second friction plate consisting of And 3,000
The first friction plate was fixed on the rotating plate rotating at 0 rpm, the second friction plate was fixed on the non-rotating thrust plate, and the thrust plate was pressed with a pressing force of 5 kg / cm ² ,
It was rotated 3000 times. At this time, the temperature of the ATF oil was 100 ° C. For each friction plate, the coefficient of static friction (μ _s ) between the first friction plate and the second friction plate, 1200 rp
The coefficient of kinetic friction (μ _d ) at m and the coefficient of friction μ ₀ at the time of apparent slippage were measured. The static friction coefficient (μ _s ) was the coefficient of friction when the second friction plate was 0.7 rpm. In addition, as an index of friction characteristics, the ratio of the friction coefficient at the time of apparent slippage and the dynamic friction coefficient (μ ₀ / μ _d )
Was calculated. When μ ₀ / μ _d is 1 or less, it is judged that the friction characteristics are good.

From Table 3, it was found that the first friction plates of Examples 1 to 8 had appropriate softness, but had no problem in durability. According to Table 4, the first friction plate of Comparative Example 1 has a poor μ characteristic, and the first friction plate of Comparative Example 2 has too much wear and is not suitable as a friction plate used for a clutch. Do you get it. Further, in the first friction plates of Comparative Example 3 and Comparative Example 4, the ATF oil deteriorated and the μ characteristic deteriorated. The first friction plate of Comparative Example 5 was broken during the durability test.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

According to the present invention, C / which constitutes the friction plate
By setting the graphitization degree and the porosity of the C composite to specific values, the frictional plate has favorable μ characteristics, thermal conductivity, and oil rejection performance, so that the differential limiting property is excellent and oil deterioration is suppressed, A clutch with significantly improved durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a chart of Raman spectra of various carbons.

Claims (3)

[Claims] 1. A first friction plate and a second friction plate are disposed so as to be superposed on each other, and the first friction plate and the second friction plate are formed into two members that can rotate relative to each other. In a clutch in which at least one of the friction surfaces of the first friction plate and the second friction plate is made of a carbon fiber reinforced carbonaceous sintered body. The fiber-reinforced carbonaceous composite has a carbon crystal deposition layer thickness Lc of 2 to 70.
and Raman spectrum of 1,360 cm ^-1
Carbon fiber reinforced carbonaceous material having an intensity ratio R [I _1,360 / I _1,600 ] of a peak in the vicinity of 1600 cm ⁻¹ of 0.4 to 0.9 and a porosity of 22 to 60% A carbon fiber reinforced carbonaceous material sintered body clutch characterized by being composed of a united body. 2. The carbon crystal deposition layer has a thickness Lc of 10 to 4
The carbon fiber reinforced carbonaceous material sintered body clutch according to claim 1, which has a thickness of 0 nm. 3. The carbon fiber reinforced carbonaceous material clutch according to claim 1, which has a porosity of 31 to 50%.