JPS6315975B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a bronze-based dry sintered friction material that has a particularly high coefficient of friction and is also improved in its aggressiveness against mating materials. Conventionally, asbestos-based dry friction materials, including those used in dry friction clutches and brakes, have had the problem of decreasing friction coefficients due to thermal and water fade phenomena, but with bronze-based friction materials, the decrease in friction coefficients due to water fade phenomena is small. However, the above-mentioned asbestos-based friction materials have a drawback of having a low coefficient of friction. In addition, increasing the coefficient of friction increases wear, so it is necessary to suppress the above-mentioned contradictory problems, and there is a need for development in terms of material composition in particular. The present invention has been made in view of the above points, and provides a dry sintered friction material made of a bronze-based sintered alloy, in which the sintered alloy has a weight ratio of 60 to 80% copper;
3-20% tin, 3% alumina and/or silica
~20%, graphite 3~10%, molybdenum disulfide 1~5
The present invention provides a dry sintered friction material having a high coefficient of friction containing 10% or less of calcium fluoride and improved aggressiveness against a mating plate. Hereinafter, the dry sintered friction material of the present invention will be explained separately into a matrix component, a wear-resistant component, and a lubricating component for convenience. (1) Matrix component The dry sintered friction material of the present invention uses a bronze-based sintered alloy as a matrix component.
Conventional asbestos-based friction materials have a high coefficient of friction, but have low resistance to the aforementioned thermal fade phenomenon and water fade phenomenon. Furthermore, iron-based sintered friction materials have the disadvantage of rust and low wear resistance. Therefore, in the present invention, we focused on a bronze-based matrix material, and selected a composition in the range of 60 to 80% copper and 3 to 20% tin in terms of weight ratio (the same applies hereinafter). This range is rather typical for conventional bronze-based matrix ranges. However, the selection criterion is based on the stability of the friction surface. That is, the bronze-based matrix material is related to material strength, and requires the above-mentioned addition amount in order to stabilize the coefficient of friction during braking and to suppress the occurrence of cracks and increase in wear. (2) Wear-resistant component The dry sintered friction material of the present invention contains 3 to 20% of alumina (Al ₂ O ₃ ) and/or silica (SiO ₂ ) as a wear-resistant component. This content is approximately the same as the conventional range, but has the effect of increasing the coefficient of friction and scraping off deposits and reaction products generated during friction. However, if there is too much, the range will be appropriately selected to attack the opponent material depending on the aggressiveness towards the opponent material. (3) Lubricating components The dry sintered friction material of the present invention contains 3 to 10% graphite and molybdenum disulfide (MoS ₂ ) as lubricating components.
1-5%, and calcium fluoride ( _CaF2 ) 10
% or less. The selection criteria were selected based on improved aggressiveness against mating materials and retention of a high coefficient of friction in high temperature conditions. In other words, these components convert into graphite, graphite, and
MoS ₂ and CaF ₂ exhibit lubricity in the respective temperature ranges in that order, and act as friction coefficient improvers when the respective temperature ranges are exceeded. and especially
CaF ₂ has a lubricating effect under high-temperature friction conditions, and various experimental results have also revealed that it has a significant effect on improving the aggressiveness of mating materials. Note that lead (Pb) and zinc (Zn), which are common lubricating ingredients, are not added based on the knowledge that a high coefficient of friction cannot be maintained due to the thermal fade phenomenon. That is, the dry sintered friction material of the present invention has a friction coefficient of about 0.4 to 0.6, and is a material with a high friction coefficient, and has high resistance to thermal fade phenomenon and water fade phenomenon, and has high resistance to the opposing material. It has improved aggressiveness. Next, an example of the dry sintered friction material of the present invention will be described. Samples A to C were produced as dry sintered friction materials of the present invention, and samples D to G were produced as conventional comparative materials. Its component composition (unit weight %) is as shown in Table 1. Moreover, the manufacturing conditions at this time were that after compression molding to a density of 79 to 82%, sintering was performed by holding under pressure for 60 minutes at a temperature of 780° C. to 820° C. in a reducing atmosphere. The size of the sample is 20 mm long x 15 mm wide x 5 mm thick.
It was made into a rectangular plate.

[Table] Next, the performances of A to G above were compared using a constant speed friction tester specified in JIS D 4411, and the results shown in Table 2 were obtained.

【table】

[Table] Table 2 compares the following four factors: friction coefficient, wear rate, attack on mating plate, and heat fade resistance. In this case, these characteristic values were obtained by friction tests and fade tests. In both tests, the mating plate was FC20 with an outer diameter of 350 mmφ, the sliding speed was 10 m/src, and
Two samples of the size described above were pressed against a mating plate at a rotational direction of 180° under the condition of surface pressure = 5 kg/cm ² . In addition, in the friction test, the friction surface temperature was set as natural heat generation, and the friction coefficient μ, wear rate δ, and opponent plate aggressiveness were measured as shown in Table 2 during continuous rotation for 15 minutes. Regarding the aggressiveness of the opponent board, the amount of decrease in the thickness of the opponent board was measured using a surface roughness meter.
The evaluation criteria were: none = 0, large = 0.004 mm, and very large = 0.0010 mm. Furthermore, in the fade test, the coefficient of friction at 100°C was increased to 250°C by continuing to press.
The amount of decrease in the coefficient of friction when the temperature reached ℃ was measured. The evaluation criteria for heat fade resistance in Table 2 were: excellent = 0.01, good = 0.02, and slightly poor = 0.03. As a result, the samples (A to C) related to the products of the present invention were
All showed excellent performance, and the effect of adding CaF ₂ was particularly remarkable. In contrast, samples without addition of CaF ₂ (D to G) were conducted for comparison.
None of them had good attack resistance to the mating plate and heat fade resistance. As for the amount of CaF ₂ added, various tests have revealed that a suitable range is 10% or less. Ten
% was excluded because it generally results in an increase in the amount of wear. As explained above, the present invention provides a dry friction material having the following effects by adding calcium fluoride to a bronze-based dry sintered friction material with a specific component composition. It is. First, a dry sintered friction material having a high coefficient of friction is provided. In the present invention, a high coefficient of friction of about 0.4 to 0.6 is obtained and the heat fade resistance is also excellent. This means that a stable friction surface can be obtained even when sliding at high speeds, making it particularly suitable for automobiles. Second, a dry sintered friction material with improved aggressiveness against a mating plate is provided. In general,
If the coefficient of friction is high, the amount of wear will increase, and the aggressiveness against the mating plate will also increase accordingly. However, in the present invention, while the friction coefficient is high, the wear rate is also suppressed. This is clear from the fact that when looking at the wear rates in Table 2, A to C of the present invention are located between D and E and F and G of the conventional example. Therefore, the improvement in aggressiveness also leads to a reduction in so-called barking. Third, a dry sintered friction material is provided that also has improved resistance to water fade. Since the present invention is based on a bronze matrix, it is resistant to water fade, and is particularly suitable for exposed type two-wheeled vehicles. In this case, if stainless steel is used as the mating plate, the problem of rust will be solved at the same time.

Claims (1)

[Claims] 1. A dry sintered friction material made of a bronze-based sintered alloy, wherein the sintered alloy contains 60 to 80% copper and 3% tin by weight.
~20%, 3~20% alumina and/or silica
%, graphite 3-10%, molybdenum disulfide 1-5% and calcium fluoride 10% or less.