JPH0256390B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sintered friction material for heavy loads, and more specifically, it is used for brake linings and clutch facings of large automobiles such as trucks, industrial vehicles such as cranes and tractors, trains and other railway vehicles, etc. The invention relates to a sintered friction material that has a short braking distance and a small amount of wear. In general, aspest and other fibers are used in the brake linings and clutch facings of passenger cars such as motorcycles and four-wheelers, but the clutch facings do not get wet when it rains. It is said that the disadvantage of these materials is that the braking distance becomes longer. For this reason, brake linings made of sintered metal materials have recently been used in light vehicles such as motorcycles instead of these fiber materials. This brake lining will not lose its braking distance or other performance even if it gets wet with water during rain, but in order to maintain a certain level of performance,
It may contain harmful ingredients such as Pb,
They tend to cause pollution problems and are subject to heavy wear, so improvements are needed. In addition, brake linings made of sintered metal materials were developed primarily for use in motorcycles, and cannot be applied directly to heavy-duty vehicles such as large automobiles, industrial vehicles, and railway vehicles. The development of friction materials is awaited. In addition, in large automobiles and vehicles, the load per unit area of the friction material itself is very large compared to passenger cars, etc. Furthermore, due to traffic congestion, brake linings, etc. are frequently used and the conditions of use are harsh. Therefore, there is a desire for a material that can improve and stabilize the coefficient of friction, have excellent wear resistance, and improve releasability from the back metal under these conditions. The present invention was established in line with the above points, and specifically, despite supporting a large load per unit area, the friction coefficient is improved and stabilized even under severe usage conditions with high frequency of use. turned into
We propose a sintered friction material with excellent wear resistance. That is, in the present invention, the weight percentage of graphite powder is 5 to 5.
15%, 1 to 5% powder of at least one of the following metal sulfur compounds such as MoS ₂ , FeS, CuS, boron nitride, tetrafluoroethylene resin, graphite fluoride, carbon fiber, Sn, Bi, or Sb, SiO _{2 and Al2O3}
Alternatively, it is characterized in that it is a molded body in which 2 to 10% of ZrO ₂ composite oxide powder is blended, and the base is made of a bronze composition of 5 to 12% Sn. The reasons for limiting the ingredients will be explained below. (1) Graphite 5-15wt% First, graphite is blended primarily to control adhesion of metals due to mutual sliding, thereby maintaining a stable coefficient of friction and providing appropriate lubricity to the friction material. give. Therefore, when an appropriate amount of graphite is blended, wear resistance is improved and squealing during braking is also prevented. In this sense, the amount of graphite added must be at least 5%, and 15%
Exceeding this is not preferable because the material strength decreases and wear increases. Note that it is preferable that the particle size of graphite is as fine as possible. The reason for this is that if the particle size is coarse, during pressure molding,
This is because layered cracks occur in a direction perpendicular to the direction of compression, and in this sense the grain size is preferably 24 mesh or less. (2) Metal sulfides, boron nitride, tetrafluoroethylene resin (PTFE), graphite fluoride, carbon fiber, Sn, Bi, Sb1-5wt% These metal sulfides have the same lubricity as graphite. However, in particular, MoS ₂ ,
By adding one or more of WS ₂ , FeS, and CuS, brake squeal can be prevented, and squeal can be effectively prevented even under heavy loads. It is preferable that the particle size of these sulfides and the like is fine; if it becomes coarse, the friction coefficient and lubricity become unstable. Further, in terms of addition, if it is less than 1%, the effect is small, but if it exceeds 5%, the strength of the material decreases and wear increases, which is not preferable. (3) Composite oxide powder of SiO ₂ and Al ₂ O ₃ or ZrO ₂ 2 to 10 wt% This composite oxide of SiO ₂ not only gives an abrasion effect to the sliding surface, but also forms an oxide film on the other sliding surface. The objective is to obtain a stable coefficient of friction and improve wear resistance by removing this. Therefore, if the amount is less than 2%, the effect will be small, and if it exceeds 10%, the opponent will be likely to be damaged, which is not preferable. In this way, SiO ₂ and Al ₂ O ₃ composite oxide and SiO ₂
The reason for blending ZrO ₂ composite oxide powder is
This is because, compared to the case where SiO ₂ is added as a powder alone, the ablation effect exerted on the mating material by the composite oxide powder is more remarkable, and the oxide film is also removed better. Furthermore, SiO ₂ has a low melting point and is subject to a large load in large automobiles, etc., and SiO ₂ melts due to temperature rise during braking, making it impossible to achieve the desired effect. On the other hand, the above-mentioned composite oxide has a high melting point, so it does not melt even if the temperature rises during braking to a considerable degree, and the desired effect can be achieved. Note that SiO ₂ composite oxide and the like require a certain degree of particle size in order to provide a certain degree of ablation effect. However, if it is too rough, it will actually damage the mating material. From this point of view, about 200 to 80 meshes is preferable. As mentioned above, graphite, metal sulfide, etc., composite oxide of SiO ₂ , etc. are mixed, and the base is made of bronze with about 5 to 12% Sn. Therefore, although copper alloy powder such as bronze powder can be blended as the base powder, tin powder and copper powder can also be blended and shaped and sintered. In other words, when mixing tin powder and copper powder,
The tin is alloyed with copper to form bronze and strengthen the base. Therefore, it is sufficient to control the particle size of tin from the viewpoint of alloying with copper, and the amount of tin to be mixed from the viewpoint of alloying with copper, so as to obtain sufficient strength as a base material. Similarly, copper powder is also regulated in terms of alloying with tin, but if a bronze base can be formed, other impurities can be included. Next, examples will be described. First, each powder was blended in the weight ratio shown in Table 1,
This was mixed, pressure-molded, and sintered using a conventional method to prepare a sample (90 x 25 x 10 tmm).
These samples were then tested using an inertial testing machine under the following conditions using STY-80 steel (wheel material for railway vehicles) as a counterpart material. Moment of inertia 8Kg-m/ ^sec2 Pushing force 14Kg/ ^cm2 Radius of action 225mm Initial speed 35Km/h, 60Km/h This inertia sliding was repeated 25 times, and the friction coefficient, amount of friction, and wear When looking for the abrasion effect against the situation and the mating material, the second result was obtained.
It was as shown in the table.

[Table] In addition, 〓 means that Cus and FeS are mixed at approximately 50% each, and each powder contains MoS ₂ and 〓 is 100%.
mesh, graphite is 24 mesh, SiO ₂ , Al ₂ O ₃ ,
ZrO ₂ was set at around 80 mesh.

[Table] As a result, the product according to the present invention was able to maintain a friction coefficient, had a small amount of wear, and was completely excellent without any squealing. In addition, a wet test was conducted by sprinkling water under the above test conditions, and almost the same test results were obtained. Furthermore, in Table 1
MoS ₂ , boron nitride, tetrafluoroethylene resin, graphite fluoride, carbon fiber, Bi,
A similar test was conducted by replacing the powder with powders such as Sb, Sn, etc., and the same effect was obtained.

Claims (1)

[Claims] 1 Graphite powder 5-15% by weight percentage, MoS ₂ ,
WS ₂ , metal sulfides such as FeS, CuS, boron nitride,
1 to 5% powder of at least one of tetrafluoroethylene resin, graphite fluoride, carbon fiber, Sn, Bi, or Sb, 2 to 10% composite oxide powder of SiO ₂ and Al ₂ O ₃ or ZrO ₂ % is blended,
A sintered friction material for heavy loads, characterized in that the base is a molded body consisting of a bronze composition of 5 to 12% Sn.