JPH0414159B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a lubricant film stabilizing composition formed on the friction surface of a friction agent used for clutch linings and brake linings of motors with electromagnetic clutches and brakes used to drive industrial sewing machines. . Conventional configuration and its problems Figure 1 shows the main parts of a motor with an electromagnetic clutch and brake.A clutch plate 2, which is one of the clutch components, is fixed to one end of the rotating shaft 1 of the drive motor. A flywheel 3, which is an inertial body, is fixed. An end bracket 4 located opposite the flywheel 3 holds a clutch yoke 5 having a clutch winding 5a, a brake yoke 6 having a brake winding 6a, and a brake shoe 7, and also connects the clutch shaft via a bearing 8. 11 is supported. This clutch shaft 11 has a pulley 9 for taking out an output at one end, and a sliding shaft portion (spline) 10 is formed at the other end. A clutch ring 14 holding a clutch lining (friction material) 13 and a brake ring 15 are supported so as to be movable in the axial direction on the sliding shaft 10 (relative movement in the rotational direction is not possible), and both are connected by an O-ring 16 and a coupling 17. connected. Next, the operation of the electromagnetic clutch/brake will be explained. The rotating shaft 1 is continuously rotating, and a flywheel 3 fixed to the end of the shaft is in a state where rotational energy is stored. Therefore, when the clutch winding 5a is energized, the electromagnetic force is extracted to the pulley 9 through the sliding shaft 10 and the clutch shaft 11. When stopping the brake winding 6a, the electromagnetic force 6 is generated.
b occurs and the brake ring 15 moves to the brake shoe 7.
brake lining (friction material) 13
A braking force is generated between the sliding shaft 10 through the brake shaft 10 and the brake shoe 7 fixed to the end bracket 4 through the clutch shaft 11. Motors with electromagnetic clutches and brakes having the above configuration are widely used to drive industrial sewing machines that typically start and stop frequently. Rotational speeds up to 5000 rpm are used. In this case, as with normal friction materials for clutches and brakes, the noise generated during clutch and brake operation and the unpleasant odor from the friction surface are disliked. Furthermore, since a motor with an electromagnetic clutch and brake for driving a sewing machine performs clutch and brake operations about 10,000 times a day, a long-life friction material is required. In order to satisfy the above requirements, an electromagnetic clutch
Cork is used as the friction material for brake motors, for example as known from US Pat. No. 3,664,472, and its counterpart is usually highly ground carbon steel. The above cork is generally pressed cork made by heating and compressing the mixture of cork particles obtained by crushing cork bark and a particle binder such as phenol resin, polyurethane resin, urea resin, or polyvinyl acetate resin, or fired cork. say. The reason why cork is used as a friction material is that although cork is a natural plant product, it is chemically stable against oils and fats, organic acids, soaps, alkalis, and salts, and it is also suitable for friction surfaces. This is because, as a friction material for electromagnetic clutches and brakes whose temperature is up to about 80°C, it does not generate any strange odor and has sufficient heat resistance.
Furthermore, it has a soft and diving tan δ derived from the approximately 260,000 minute air-filled cell structure per ¹ cm3, and has a large porosity, which makes the contact sound during clutch and brake operation soft, and the coefficient of friction is low. This is because, in addition to frictional characteristics such as these, it has the advantage of being a material that is less likely to squeal during clutch/brake operation due to the above-mentioned properties. On the other hand, the frictional characteristics of the cork generally tend to change due to external factors such as temperature and sliding speed unless a lubricating film is present on the friction surface, resulting in unstable clutch/brake operation. Furthermore, since dry cork itself has a high coefficient of friction, the coefficient of static friction is higher than the coefficient of kinetic friction, just like other materials with high friction coefficients. In such a case, the stick/slip phenomenon is likely to occur in the low speed region,
In this state, the rate of change in the coefficient of friction due to temperature is large, and squealing noise is likely to occur during clutch/brake operation. Furthermore, cork itself has poor heat dissipation properties, so frictional heat tends to accumulate on the friction surface.
As a result, the mechanical strength of the cork near the friction surface becomes smaller than the adhesion force with the mating material, and some of the cork may transfer to the mating material, or some of the cork may fall off. Causes abnormal friction and wear. This abnormal wear phenomenon becomes noticeable especially when the clutch/brake operation is performed at high speed F, accompanied by a squealing noise. As a friction material that prevents the problems caused by the frictional characteristics of cork as described above and takes advantage of the advantages of cork, for example, cork is impregnated with grease as in U.S. Patent No. 3,777,864, or cork is lubricated. There are friction materials impregnated with oil. However, since cork is used as a waterproof material and cork stopper, it is difficult to directly infiltrate lubricating oil into the cork's own cells due to its own resinous substance and uniform cell structure. is allowed to penetrate between the cork particles of pressed cork or fired cork. In addition, this type of friction material, including friction materials in which cork is impregnated with a portion of the base oil of grease, is more susceptible to abnormal wear phenomena during clutch and brake operation than when cork is used as is. The reason why it is effective against squealing noise is that a lubricating film is formed on the friction surface, which can improve problems caused by the frictional characteristics of cork. Generally, when lubricating oil or grease exists on a friction surface and functions as a lubricating film, the coefficient of friction decreases, but even if the lubricating film is formed only from lubricating oil, for example, the coefficient of friction will still maintain a value of 0.3 or more. Since this is easy, it is possible to secure a sufficient friction coefficient as a friction material for clutch/brake operation, and it is also possible to maintain a lubricating film against external factors such as temperature, surface pressure, and sliding speed. This is because the effect makes it possible to maintain a significantly stable coefficient of friction. Of course, if the lubricating oil or grease loses its function as a lubricating film on the friction surface, the clutch
This not only causes squealing noise during brake operation, but also accelerates wear of the friction material, leading to the end of its service life. Therefore, we are addressing the issue of extending the lifespan of the friction material, which is an issue with motors with electromagnetic clutches and brakes that use porous materials such as cork, as well as the desire for friction materials that are less likely to generate squealing noises when the clutch or brake is operated. On the other hand, it is important to have a means for the lubricating oil or grease to maintain its function as a lubricating film on the friction surface for a long period of time. Purpose of the Invention The present invention aims to maintain the function of the lubricating film of the friction material for a motor with an electromagnetic clutch/brake and to perform stable clutch/brake operation over a long period of time. The purpose of this invention is to suppress the phenomenon of a decrease in transmitted torque during clutch/brake operation, which is a drawback caused by this. Structure of the Invention The present invention aims to stabilize a lubricating film formed by lubricating oil or grease on the friction surface of a soft porous material such as pressed cork or fired cork used as a friction material for a motor with an electromagnetic clutch/brake. Regarding the composition, one type or a mixture of two or more types selected from the compounds listed in a to d below is used. a amorphous ethylene-α-olefin copolymer with a molecular weight of 5×10 ⁴ or more, amorphous ethylene-α-olefin-nonconjugated polyene copolymer, b synthetic oil, mineral oil, c solid lubricant, d vulcanizing agent , thermopolymerizable resin, and drying oil. In addition, various additives known as lubricating oil additives may be appropriately used in the synthetic oil and mineral oil (b). Description of Examples The amorphous ethylene-α-olefin copolymer referred to in the present invention is an amorphous copolymer of ethylene and α-olefin. Examples of α-olefins include propylene, 1-butene, 1-hexene, and the like. Particularly preferred polymers are ethylene-propylene copolymers, ethylene-butene-1
It is a copolymer. The ethylene content in the copolymer is 20
~85 mol%, preferably 30-80 mol%. Furthermore, the amorphous ethylene-α-olefin-nonconjugated polyene copolymer is a low unsaturated amorphous copolymer consisting of ethylene, α-olefin, and nonconjugated polyene. Examples of α-olefins include propylene, butene-1, hexene-1, and the like. Particularly preferred are propylene and butene-1. A non-conjugated polyene is a cyclic or acyclic polyene containing two or more non-conjugated double bonds, such as hexadiene-1,4, hexadiene-1,
5, acyclic conjugated dienes such as heptadiene-1,6, 2-methyl-pentadiene-1,4, acyclic non-conjugated trienes such as octatriene-1,4,7, ethylidenenorbornene, zinclopentadiene, cyclo octadiene-1,4, cyclooctadiene-1,5, cyclododecadiene-1,
6, cyclododecadiene-1,7, cycloheptadiene-1,4, cyclohexadiene-1,4,
and cyclododecatriene-1,5,9. Among them, cyclic nonconjugated dienes are preferred, and dicyclopentadiene and ethylidene norbornene are particularly preferred. Particularly preferred amorphous ethylene-α-olefin-nonconjugated polyene copolymers are ethylene-propylene-dicyclopentadiene copolymer and ethylene-propylene-ethylidenebornene copolymer. The ethylene content in the copolymer is 20-85 mol%, preferably 30-80 mol%, and the content of non-conjugated polyene is 0.1-20 mol%, preferably 0.1-15 mol%. In addition, the mineral oil or synthetic oil referred to in the present invention is generally used as a base oil for grease, etc., but in order to reduce the friction coefficient of the friction material to 0.5 or less, it must have a kinematic viscosity of 100 cst or less at 40°C. Preferably. In addition, the vulcanizing agent referred to in the present invention refers to the general formula R-
Refers to an organic peroxide represented by OOH. however,
R is an aliphatic, cycloaliphatic or aromatic residue, which may have a substituent. Specific examples include bromo-t-butyl-hydroperoxide, cumene hydroperoxide, t-
Examples include amyl hydroperoxide. It also includes the case where a solution of a transition metal salt of an organic carboxylic acid having 7 or less carbon atoms in a polar organic solvent is used in combination with a compound having a carbon-carbon double bond as a vulcanization accelerator. Furthermore, as a substitute for the vulcanizing agent, one or more thermopolymerizable resins selected from the group consisting of epoxy resins, phenolic resins, and acrylic resins, or even drying oil may be used. These vulcanizing agents or thermopolymerizable resins are preferably liquid and crosslinkable at low temperatures. In addition, the solid lubricants referred to in the present invention include graphite, molybdenum disulfide, tungsten disulfide, metal iodides such as nickel iodide, carbon fluoride, etc., and one or more of these are used as appropriate. be done. In the present invention, in addition to the above, methanol, ethanol, ethylene glycol, octane, hexane,
Organic solvents such as toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, and dimethyl acetamide can also be used in combination. The above-mentioned lubricating film function stabilizer consisting of the amorphous copolymer, mineral oil, synthetic oil, vulcanizing agent or thermopolymerizable resin composition, drying oil, solid lubricant, and diluent can be easily mixed uniformly. can be manufactured. In particular, the amorphous ethylene-α-olefin copolymer or amorphous ethylene-α-olefin-nonconjugated polyene copolymer referred to in the present invention has a molecular weight of 5×
10 Use ⁴ or more. This is, for example, a molecular weight 1 commonly used as a lubricating oil viscosity index improver.
~1.5×10 ⁴ polyisobutylene or molecular weight 5×10 ³
It has superior shear stability and thermal stability compared to ~2.0×10 ⁴ polymethacrylate (methacrylic acid ester polymer). Next, details of the present invention will be specifically explained while comparing with comparative examples. The friction properties of the friction material used in the following explanation are based on JIS-D4411, and the mating material is a carbon steel plate ground to a surface roughness of 3S.
The sliding speed is 2m/sec, and the surface pressure of the friction material is 1.8Kgf/
^cm2 condition. (Comparative Example) Figure 2 shows the relationship between friction surface temperature and dynamic friction coefficient. In the figure, A is a pressed cork obtained by adding 20 parts by weight of a polyurethane resin as a binder to 100 parts by weight of cork particles of 14 to 35 mesh, and heating and compressing the mixture to an apparent density of about 0.6 g/cm ³ . B is a friction material obtained by impregnating A with a lubricating oil having a kinematic viscosity of 85 cst at 40°C, and C is a friction material impregnated with a lubricating oil having a kinematic viscosity of 465 cst at 40°C. The characteristic curve in Figure 2A shows that when cork such as pressed cork or fired cork is used as a friction material, the dynamic friction coefficient changes greatly depending on temperature.
It is obvious that this tends to cause squealing noise during clutch/brake operation. In this case, although the value of the dynamic friction coefficient varies somewhat depending on the type and amount of the binder in the cork particles, it remains the same with respect to changes due to temperature. Therefore, we will focus on B and C, which correspond to friction materials made of cork impregnated with lubricating oil, as known from US Pat. No. 377,786. When a lubricating film is formed on the friction surface by the lubricating oil impregnated into the cork as in this case, the rate of change in the coefficient of dynamic friction due to temperature becomes extremely stable. Further, as inferred from the value of the dynamic friction coefficient, it is also possible to adjust the friction material to have a desired friction coefficient by appropriately selecting the base oil viscosity of the lubricating oil or grease that forms the lubricating film. In the case of C, since the coefficient of dynamic friction is high, it can be inferred that squealing noise is likely to occur during clutch/brake operation. FIG. 3 is a characteristic diagram showing changes in the dynamic friction coefficient and the amount of friction with respect to the friction distance. Table 1 shows the structure of the friction material shown in FIG.

[Table] In Fig. 3, a characteristic feature is that the change in the dynamic friction coefficient of friction materials C, D, and E with respect to the friction distance shows a maximum. This phenomenon occurs as the coefficient of dynamic friction increases as the lubricating oil forming a lubricating film on the friction surface is consumed, and as a result, some of the cork particles near the friction surface fall off. Then, the lubricating oil existing inside the friction material, that is, between the cork particles, flows out from that part onto the friction surface and forms a lubricating film, so that the coefficient of dynamic friction decreases again. However, because a sufficient lubricant film cannot be secured between the cork particles near the friction surface due to the effects of temperature, surface pressure, etc., the coefficient of dynamic friction becomes stable at a high level, and the clutch and brake tend to squeal when operating. . Further, when such a coefficient of dynamic friction shows a maximum, an abnormal friction state occurs, which has the drawback of extremely shortening the life of the friction material. Even if the oil content is increased for friction material C as shown in D and E, or even if grease is applied to the friction surface, the maximum point of change in the coefficient of dynamic friction and the corresponding abnormal wear phenomenon will be slightly shifted to the long distance side. Just let it happen. As mentioned above, even if lubricating oil is impregnated between cork particles and a lubricating film is formed on the friction surface, or grease is applied to supplement the amount of lubricating oil that forms the lubricating film, it will not last long. It is insufficient as a friction material for stable clutch/brake operation across the range. This is because the space between cork particles near the friction surface is narrowed by surface pressure or frictional heat, so the lubricating oil present inside the friction material does not function effectively on the friction surface. (Example) Next, an example of the friction material lubricating film stabilizing composition according to the present invention will be described. However, friction material F contains 15 parts by weight of an amorphous ethylene-propylene copolymer with a molecular weight of about 7 x ¹⁰⁴ , 0.5 parts by weight of a mixture of cumene hydroxyperoxide and ethylene glycol dimethacrylate, 10 parts by weight of molybdenum disulfide, and A friction material lubricating film stabilizing composition comprising 80 parts by weight of alkylbenzene having a viscosity of 28 cst was applied to the friction surface of friction material C shown in Table 1. In addition, G is 15 parts by weight of amorphous ethylene-propylene-dicyclopentadiene copolymer with a molecular weight of about 7 x 10 ⁴ , 8 parts by weight of phenol resin,
10 parts by weight of molybdenum disulfide and kinematic viscosity at 40°C
A friction material lubricating film stabilizing composition comprising 80 parts by weight of alkylbenzene of 28 cst was similarly applied to the friction surface of friction material C. Incidentally, the friction material E is a comparative example of the friction material lubricating film stabilizing composition according to the present invention, and is obtained by applying grease to the friction surface of the friction material C. However, the grease is 15 parts by weight of polyisobutylene with a molecular weight of approximately 5 x ¹⁰³ ,
10 parts by weight of molybdenum disulfide, 9.5 parts by weight of lithium stearate, and 80 parts by weight of alkylbenzene having a kinematic viscosity of 28 cst at 40°C. In both F and G in Figure 3, the fluctuations in the coefficient of dynamic friction are extremely small compared to friction materials ~G, and the values are also at the stage where the friction distance of C is still small, that is, when the lubricant oil forms a lubricant film on the friction surface. It is equivalent to the value of the coefficient of kinetic friction when the function is fully fulfilled. This clearly shows that the friction material lubricating film stabilizing composition according to the present invention does not inhibit the lubricating film function of the lubricating oil in any way, and moreover works to stabilize that function over a long period of time. Incidentally, in the case of friction material E shown as a comparative example, although it has a similar structure to friction materials F and G, the above-mentioned effects clearly observed in F and G are not realized. Next, the above friction material F, (example), and friction material H
(Comparative Example) A case will be explained in which the motor is installed in the motor with an electromagnetic clutch and brake shown in FIG. FIG. 4 is a characteristic diagram showing the number of clutch/brake operations, wear of the friction material, and changes in transmitted torque when clutch/brake operations are performed every 1.5 seconds. As described above, according to the present invention, the life of the friction material is more than doubled,
Moreover, the transmitted torque can be improved by more than 20%. FIG. 5 is a characteristic diagram showing the relationship between amorphous ethylene-propylene copolymers having different molecular weights and the same structure as friction material F and the transmitted torque. As described above, when the molecular weight of the amorphous copolymer is 5×10 ⁴ or more, the transmission torque is significantly improved.
As a comparative example, a sufficient improvement in transmission torque was not observed in the case where polyisobutylene having a molecular weight of 10,000 to 15,000 and polymethacrylate having a molecular weight of 5,000 to 20,000 were substituted with an amorphous copolymer. Effects of the Invention As described above, a friction material lubrication based on an amorphous ethylene α-olefin copolymer or an amorphous ethylene α-olefin non-conjugated polyene copolymer having a molecular weight of 5×10 ⁴ or more according to the present invention Use of the membrane function stabilizing composition allows stable clutch/brake operation over a long period of time.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the configuration of the main parts of a motor with an electromagnetic clutch and brake, Figure 2 is a characteristic diagram showing the relationship between friction surface temperature and dynamic friction coefficient, and Figure 3 is a diagram showing comparative examples C, D, E and the present invention. A characteristic diagram showing the coefficient of dynamic friction and wear versus friction distance for Invention Examples F and G. Figure 4 shows the friction materials of Comparative Example E and Invention Example F installed in the motor with the electromagnetic clutch and brake shown in Figure 1. FIG. 5 is a characteristic diagram showing the relationship between the number of clutch/brake operations, friction, and transmitted torque in this case. FIG. 5 is a characteristic diagram showing the relationship between the molecular weight of an amorphous copolymer and transmitted torque.

Claims (1)

[Claims] 1 a Amorphous ethylene-α with a molecular weight of 5×10 ⁴ or more
-Olefin copolymer or amorphous ethylene-
α-olefin-nonconjugated polyene copolymer, b synthetic oil, c solid lubricant, d vulcanizing agent, thermopolymerizable resin,
A friction material lubricating film stabilizing composition comprising a drying oil and comprising one or a mixture of two or more selected from the above groups a to d.