JP2991970B2 - Friction material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction material used for a clutch, a brake and the like, and more particularly to a friction material suitable for an electromagnetic clutch.

[0002]

2. Description of the Related Art Electromagnetically operated friction clutches, that is, electromagnetic clutches, have good responsiveness, controllability and maneuverability due to the electric power source, and are most advantageous for automatic or remote control. Therefore, in a vehicle, an industrial machine, a production machine, or the like, the electromagnetic clutch is widely and generally used for transmitting and interrupting relatively small power (torque).

[0003] As a friction material (clutch lining) of such an electromagnetic clutch, a sintered alloy-based friction material may be used in some cases. However, in general, it is the same as a disc brake pad, a drum brake lining, or the like. A resin-based friction material, that is, a fiber base material forming a skeleton;
A friction material formed by thermoforming a mixture containing a thermosetting resin as a binder and a filler such as a friction modifier is used. In more detail, as the fiber base material,
Organic fibers such as aramid fibers, potassium titanate fibers or whiskers, inorganic fibers such as ceramic fibers, copper fibers,
Non-ferrous metal fibers such as brass fibers are used in appropriate combination. In addition, a phenol resin is generally used as a thermosetting resin as a resin binder. Furthermore, fillers dispersed and filled in the matrix of these fiber base materials and resin binders are mainly fillers such as barium sulfate and calcium carbonate for improving abrasion resistance and heat resistance, Graphite to adjust and stabilize the coefficient of friction,
Solid lubricants such as molybdenum disulfide and friction modifiers such as cashew dust are used.

[0004]

By the way, in such an electromagnetic clutch, it is particularly necessary that a stable coefficient of friction be obtained from the beginning of use. That is, the friction torque caused by the frictional engagement between the friction material and the mating material is determined by the friction coefficient between them and the operating force (pressure) for pressing them, but in the case of an electromagnetic clutch, the operating force by the electromagnetic coil is constant. This is because the operation characteristics cannot be controlled by adjusting the pedal operation like a brake or a clutch of an automobile. For example, when the friction coefficient is small, the engagement characteristics do not become as set, and the predetermined response and controllability cannot be obtained.

[0005] However, the friction coefficient of a friction material is determined by the surface properties of its sliding surface, that is, the conformability to a mating material (hit).
And it is not constant from the beginning of use. That is, the friction coefficient is generally low and unstable in the early stage of use when the sliding surface is rough and the contact with the mating material is not sufficient. Then, the frictional engagement with the partner material is repeated,
As the sliding surface is smoothed and adapted to the mating material, the coefficient of friction gradually increases and then stabilizes to a constant value. Therefore, in the case of an electromagnetic clutch, after assembly, before the actual use is started, the frictional coefficient rises to a constant value, and until the frictional material stabilizes, the contacting process is performed to allow the frictional material to adapt to the mating material in advance. (Break-in processing) is generally performed. The same applies to other frictional engagement devices that cannot control the operating force, such as an electromagnetic brake and an electromagnetic clutch / brake.

[0006] However, in the case of this contact, particularly in the case of an electromagnetic clutch, it is required that a sufficiently stable friction coefficient is obtained from the initial stage of use, so that it may take a very long time, and it may take 30 minutes. Some of the above were necessary. Therefore, with respect to the friction material used in such an electromagnetic clutch or the like, there has been a demand for shortening the contact time, that is, the time until the rise of the initial friction coefficient is stabilized.

Therefore, an object of the present invention is to provide a friction material capable of shortening the time required for hitting, that is, the time required for the friction coefficient to be stabilized in the initial stage of use (initial friction coefficient rise time). Is what you do.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted various investigations and studies to solve the above-mentioned problems, and as a result, obtained a polishing powder of a rubber mold friction material (semi-mold friction material). By blending at a predetermined ratio to the whole,
It has been found and confirmed that the initial friction coefficient rise time can be effectively reduced.

That is, a friction material according to claim 1 is a friction material obtained by thermoforming a mixture containing a fiber base material, a resin binder made of a thermosetting resin, and a filler. At least a part thereof contains abrasive powder of a rubber mold friction material in a ratio of 10 to 70% by weight based on the whole friction material.

The rubber-molded friction material (semi-molded friction material) is used as a facing of a clutch for a power train of an automobile, and is used for roving of a base fiber impregnated with a resin. It is obtained by adhering a compounded rubber containing a filler, winding it up in a ring shape, heating and pressing, and then polishing and polishing the surface. The polishing powder is generated as polishing dust during the polishing finish.

As described above, in the friction material according to the present invention, the abrasive powder of the rubber mold friction material is blended at a predetermined ratio with respect to the entire friction material. The time required for hitting, that is, the time required for the initial friction coefficient to stabilize, can be effectively reduced.

The reason or the effect of the abrasive powder on the rubber mold friction material is speculated, but is presumed as follows. That is, since the polishing powder of the rubber mold friction material is obtained as described above, it appropriately contains a rubber component, and therefore has appropriate flexibility and moderately high abrasion. As a result, the friction material is imparted with appropriate flexibility and abrasion by the addition of the abrasive powder of the rubber mold friction material, so that the friction material easily conforms to the mating material, and as a result, the contact time, that is, the initial friction coefficient It is believed that the rise time is reduced. In addition, since the polishing powder of the rubber mold friction material is very fine particles and also has a moderate elasticity, the friction material is densified by its blending, and as a result, the friction material surface is easily smoothed, Another reason is that the contact with the counterpart material is easily made uniform. Note that such densification of the friction material also has an advantage in that when oil or a solvent accidentally adheres to the friction material, penetration into the friction material is prevented.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the friction material will be described in more detail.

As described above, in the friction material of the present invention, in order to reduce the time required for the initial friction coefficient to rise (hit time), at least a part of the filler is polished by a rubber mold friction material. Mix the flour.

Here, as described above, a relatively large amount of the polishing powder of the rubber mold friction material is generated as polishing dust in the polishing and finishing step of the normal rubber mold friction material manufacturing process, and is generally discarded. It has been disposed of as landfill. Therefore, the use of this abrasive powder
It also reduces the amount of waste and recycles resources.

The rubber-molded friction material is used as a facing of a pedal-operated friction clutch provided between an engine of an automobile and a transmission, for example, and is a base material impregnated with a coupling resin. To the roving of the material fiber, a compounded rubber containing a filler is adhered, wound up in a ring shape, and then heated and pressed, and then
The obtained friction material molded product is generally manufactured by polishing the surface to a predetermined thickness. This friction material is also called a semi-mold friction material because it is manufactured by winding a roving to which a compounded rubber is adhered into a ring shape and shaping.

More specifically, this rubber mold friction material is obtained by impregnating a roving made of a base fiber such as a glass fiber with a thermosetting resin solution as a binding resin, and preliminarily curing the resin coating. After the roving is obtained, the roving is impregnated with a solution of a compounded rubber containing a rubber and a filler, and dried, and then the compounded rubber-adhered roving is wound into a clutch-facing shape or the like and preformed. Then, it is heat molded, and finally, the molded body is polished and finished to a predetermined thickness to produce the molded body. Here,
As the base fibers of the rubber mold friction material, in addition to inorganic fibers such as glass fibers, metal fibers such as brass fibers, and organic fibers such as aramid fibers and novoloid fibers are used in appropriate combination. Further, a thermosetting resin such as a phenolic resin or an epoxy resin is used as the binding resin, and SBR, NBR, or the like is used as the rubber. Further, as the filler, a solid lubricant such as graphite, a filler such as barium sulfate and calcium carbonate, an organic polymer powder such as cashew dust and the like are used.

Therefore, in the polishing powder of the rubber mold friction material obtained in the polishing finishing step, a composite of a base fiber such as glass fiber, a cured product of a thermosetting resin and rubber, and a filler is crushed. It consists of a fine powder in a different form.
In other words, on the components, apart from further containing rubber,
It is substantially the same as the resin mold friction material. In some cases, the polishing powder of the rubber mold friction material obtained as polishing debris in such a polishing finishing process contains foreign matters such as crushed pieces of a belt sander. Is done.

Such an abrasive powder can be used by being generally blended at a blending ratio of 10 to 70% by weight with respect to the whole friction material. If this ratio is too small, generally less than 10% by weight, the effect of shortening the rise time of the initial friction coefficient cannot be sufficiently obtained for practical use. On the other hand, the larger the mixing ratio of the abrasive powder, the shorter the hitting time and the more advantageous in terms of recycling waste. However, even if it is added too much, the effect due to it will not only reach a plateau state, but too much compounding will make it difficult to mix other filler components and fiber components, and will reduce the moldability and formability. There is also a tendency that the strength and the like of the friction material afterwards are reduced. Therefore, up to 70% by weight,
It is preferable to mix at a ratio less than that. A more preferable mixing ratio of the rubber mold friction material polishing powder is 30 to 60.
% By weight.

Other components forming the friction material of the present invention,
That is, the fiber base material, the resin binder, and other fillers are
It is the same as the conventional one.

The fibrous base material, that is, the fibrous base material which forms the skeleton of the friction material, is aramid fiber,
Novoloid fiber, nylon fiber, organic fiber such as rayon fiber, silicate fiber, alumina fiber, alumina-silica fiber, tyrano fiber, calcium silicate fiber, potassium titanate fiber or whisker, carbide, nitride fiber or whisker, Examples include ceramic fibers such as magnesium oxide whiskers, rock wool, and slag wool, or inorganic fibers such as whiskers, carbon fibers, and glass fibers, and metal fibers such as copper fibers, brass fibers, steel fibers, and stainless steel fibers. . These fibers can be used in an arbitrary combination of one or more of them. But,
Among them, aramid fibers are particularly preferable, since they can be fibrillated, so that they can be easily handled at the time of mixing the friction material and can prevent segregation of the material components.
This can be suitably used in combination with a ceramic fiber or the like as appropriate.

As the resin binder for binding and holding the fiber base material and the filler, phenol resin, melamine resin, epoxy resin, polyimide resin,
A thermosetting resin such as a polyester resin is exemplified. However, among these, a phenol resin can be most preferably used because of its high bonding strength and high thermal strength. Further, as this phenol resin, a modified phenol resin modified with alkylbenzene or the like can also be suitably used.

Further, as the filler as a powdery component, in addition to the above-mentioned abrasive powder of the rubber mold friction material, a filler such as barium sulfate and calcium carbonate, a filler such as graphite, molybdenum disulfide and antimony trisulfide may be used. Solid lubricant, cashew dust or other organic polymer powder, silica,
Abrasive agents such as zirconium oxide and alumina, metal powders such as copper powder, zinc powder, and brass powder for improving thermal conductivity, and other additives for adjusting friction can be used. .

However, when deciding the specific composition of these components, especially the fiber base material and the filler, it is necessary to make sure that the abrasive powder of the rubber mold friction material already contains the fiber base material and the filler. It is necessary to consider. That is, the amount of the overlapping filler component and the fibrous base material can be made smaller than in the normal case according to the blending amount of the abrasive powder of the rubber mold friction material.

The friction material according to the present invention can be manufactured by a usual method as a resin mold friction material. That is, the above-mentioned fiber base material, a resin binder composed of a thermosetting resin, and various fillers including abrasive powder of a rubber mold friction material are uniformly mixed, and the mixture is preformed, and then preformed. The body can be produced by a usual thermoforming method in which a body is heated and pressed.

[0026]

The present invention will be described below in more detail with reference to examples and comparative examples.

FIG. 1 is a table showing the composition (% by weight) of the friction materials of Examples 1 to 4 of the present invention, Comparative Examples 1 and 2, and the results of evaluation tests. FIG. 2 is a characteristic diagram showing the change over time of the friction coefficient during the contact test of the friction materials of Example 4 of the present invention and Comparative Examples 1 and 2.

[Production of Friction Material (Electromagnetic Clutch Lining)] The friction materials of Examples 1 to 4 of the present invention were produced with the composition (% by weight) shown in FIG. Further, for comparison with these examples, the friction materials of Comparative Examples 1 and 2 were also manufactured. In addition, each friction material of these Examples and Comparative Examples is specifically embodied as a lining for an electromagnetic clutch.

Embodiments 1 to 4 As shown in FIG. 1, the friction material (electromagnetic clutch lining) of each of these embodiments is composed of a fiber base material and a thermosetting resin for bonding and holding the fiber base material. Resin binder consisting of, and various fillers dispersed and filled in the matrix of these fiber base material and the resin binder, formed as at least a part of the filler, the initial friction coefficient rise time In order to reduce the (hit time), the abrasive powder of the rubber mold friction material (semi-mold friction material) is included. In each of these examples, the mixing ratio of the abrasive powder of the rubber mold friction material and other materials contained as a part of the filler is variously changed. Here, the following materials were used.

Aramid fibers, rock wool, and calcium silicate fibers were used in an appropriate combination as a fibrous base material which is a fibrous component forming the skeleton of the friction material.
Therefore, each friction material is formed here as a non-steel friction material that does not include steel fibers.

A phenol resin was used as a resin binder for binding and holding these fiber base materials.

As the filler, cashew dust for adjusting and stabilizing the friction coefficient and barium sulfate as a filler were used in addition to the abrasive powder of the rubber mold friction material.

Here, the abrasive powder of the rubber mold friction material is prepared by adhering a compounded rubber containing various fillers to a roving made of glass fiber and brass fiber impregnated with phenolic resin, winding it into a ring shape and heating it. This is generated in a surface polishing finishing step of a rubber mold friction material obtained by pressure molding. Specifically, the composition of the rubber mold friction material is as follows: glass fiber 30% by weight, brass fiber 5% by weight, phenol resin 10% by weight, compounded rubber 55% by weight.
(Styrene-butadiene rubber (SBR) 35% by weight, carbon black 10% by weight, barium sulfate 35% by weight,
Cashew dust 10% by weight, vulcanizing agent 10% by weight). Accordingly, the composition of the polishing powder is also substantially equal to the composition of the rubber mold friction material, although the proportion of the compounded rubber component is somewhat large.

Using these materials, the friction materials of Examples 1 to 4 were produced by changing the mixing of the abrasive powder of the rubber mold friction material and other materials.

More specifically, in Example 1, the blending of the abrasive powder of the rubber mold friction material was relatively reduced to 30% by weight. As for other materials, as a fiber base material, 3% by weight of aramid fiber and rock wool 23 were used.
% By weight and 8% by weight of calcium silicate fiber,
Also, 16% by weight of a phenol resin as a resin binder,
It is a mixture of 13% by weight of cashew dust and 7% by weight of barium sulfate as a filler. Therefore, cashew dust and barium sulfate, which overlap with the components of the polishing powder,
The total amount is 15% by weight and 13% by weight, respectively. The ratio of SBR as a rubber component is 6
% By weight.

In Example 2, the amount of the abrasive powder for the rubber mold friction material was slightly increased to 42% by weight. And about a fiber base material, the same material as Example 1 was used, and 3% by weight of aramid fiber and 23% by weight of rock wool were used.
And 2% by weight of calcium silicate fiber,
It contains 15% by weight of a phenolic resin as a resin binder, 8% by weight of cashew dust as a filler, and 7% by weight of barium sulfate.

In Example 3, the mixing ratio of the abrasive powder of the rubber mold friction material was further increased to 51% by weight. Further, as the fiber base material, only 4% by weight of aramid fiber was mixed, 22% by weight of phenol resin as a resin binder, 16% by weight of cashew dust as a filler, and 7% by weight of barium sulfate. .

In Example 4, the mixing ratio of the abrasive powder of the rubber mold friction material was further increased to 53% by weight. And, as in Example 3, only 4% by weight of aramid fiber was blended as in Example 3, and 18% by weight of phenol resin as a resin binder and Cashew Dust 1 as a filler.
8% by weight and 7% by weight of barium sulfate are blended.

<Comparative Examples 1 and 2> In contrast to these examples, the friction materials of Comparative Examples 1 and 2 were formed in accordance with the composition of a brake pad for an automobile, and both were made of a fiber base material. And a resin binder made of a thermosetting resin, and various fillers, and formed without blending abrasive powder of a rubber mold friction material.

Specifically, in Comparative Example 1, 8% by weight of aramid fiber and calcium silicate fiber 1
2% by weight and 12% by weight of calcium titanate fiber are blended, and 10% by weight of a phenol resin is used as a resin binder, 7% by weight of cashew dust, 44% by weight of barium sulfate, and 7% by weight of a graphite are used as a filler. % By weight.

In Comparative Example 2, 5% by weight of aramid fiber, 11% by weight of rock wool, and 8% by weight of calcium titanate fiber were blended as a fiber base material, and 10% by weight of a phenol resin was used as a resin binder. %, As a filler, 6% by weight of cashew dust, 58% by weight of barium sulfate, and 2% by weight of graphite.

The production of the friction materials (electromagnetic clutch linings) of these Examples and Comparative Examples was carried out by a usual thermoforming method, specifically as follows. That is, the friction material raw material having the above-mentioned composition containing or not containing the abrasive powder of the rubber mold friction material is sufficiently uniformly mixed with a blender, and then the powder mixture is put into a preforming mold,
At normal temperature, pressure was applied at a pressure of 400 kg / cm ² for 10 seconds to form a preform of a friction material. Next, the preform of the friction material was thermoformed at a pressure of 200 to 400 kg / cm ² at a temperature of 150 to 160 ° C. for 3 minutes to obtain a friction material as an electromagnetic clutch lining.

[Evaluation Test] Next, a friction test was carried out on each of the friction materials of the various examples and comparative examples produced by changing the mixing ratio of the abrasive powder and the like of the rubber mold friction material as described above. At high temperatures and at high temperatures. In addition, a hit test was carried out for each friction material, and the initial friction coefficient rise time (hit time) was measured.
Further, apart from these tests, the oil porosity of each friction material was measured. Details of these tests are as follows.

(1) Friction test For each friction material, the friction coefficient at low and high temperatures
It was measured by performing a JIS constant speed friction test according to IS-D-4411. The test conditions are as follows. (Test conditions) Rotation speed of friction partner material: 7 m / s Pressing: 10 kg / cm ² Measurement temperature: 100 ° C, 150 ° C, 200 ° C, 250 ° C (2) Hitting test Initial friction coefficient rise time (hitting time) For the measurement, for each friction material, a hit test was performed using a tester (FMTM tester) equivalent to SAE-J-661, and a change with time of the initial friction coefficient was measured.
The time required for this to stabilize (initial friction coefficient rise time) was measured. The test conditions are as follows. (Test conditions) Rotation speed of friction partner material: 0.7 m / s Pressing: 3.5 kg / cm ² ON / OFF: 12 seconds / 6 seconds (3) Oil porosity For oil porosity, see JIS-D-4418. The test was performed and measured according to the procedure.

FIG. 1 shows the friction coefficient, initial friction coefficient rise time, and oil porosity at each of these temperatures measured for the friction materials of the examples and comparative examples, together with their compositions. FIG. 2 shows the change over time in the initial friction coefficient of each of the friction materials of Example 4 and Comparative Examples 1 and 2. In FIG. 2, the coefficient of friction rises,
The point at which the temperature becomes constant and stable is indicated by a circle.

[Test Results] As shown in FIGS. 1 and 2, Comparative Example 1 corresponds to a friction material conforming to a general automobile brake pad and does not contain abrasive powder of a rubber mold friction material as a filler. In Comparative Example 2 and Comparative Example 2, the friction coefficient showed a sufficiently high value, and the change due to temperature change was small and in a favorable range. In both cases, it takes 30 minutes and a long time is required.

On the other hand, in each of the examples in which the abrasive powder of the rubber mold friction material was used in a sufficient ratio as the filler, a sufficiently high friction coefficient was obtained at each temperature and the initial friction was high. The coefficient rise time is extremely short, and a stable friction coefficient is obtained within 5 minutes. Further, the oil porosity shows a remarkably low value as compared with the comparative example, and it can be seen that the friction material is densified by containing the abrasive powder of the rubber mold friction material which is a fine particle.

As described above, based on the test results, by using the abrasive powder of the rubber mold friction material at a predetermined ratio,
It can be seen that the time required for the initial friction coefficient to stabilize is greatly reduced, and that a good friction coefficient can be maintained thereafter.

The friction material of the present invention,
Although the electromagnetic clutch lining has been described as an example, the present invention is not limited to the electromagnetic clutch lining, but may be applied to other electromagnetic brake linings, clutch facings, disk brake pads, or drum brake linings. Similarly, it can be advantageously applied as a friction material of the friction engagement device.
Further, the types and the mixing ratios of the fiber base material, the resin binder, and the filler forming the friction material can be variously changed without being limited to the embodiment.

[0050]

As described above, the friction material according to the present invention comprises a fibrous base material, a resin binder comprising a thermosetting resin,
In a friction material obtained by thermoforming a mixture containing a filler, a polishing powder of a rubber mold friction material is contained as a part of the filler at a ratio of 10 to 70% by weight based on the whole friction material.

Therefore, according to this friction material, since the abrasive powder of the rubber mold friction material is contained in a predetermined ratio, the friction material is given appropriate flexibility and abrasion, and the abrasive powder is very fine. Because of the fine particles, the friction material is densified, so it can be easily blended with and hit against the mating material. As a result, the time required for the initial friction coefficient to stabilize (the contact time) There is an effect that can be greatly reduced. In addition, since the polishing powder of the rubber mold friction material is generated in a relatively large amount in the polishing and finishing step of the normal rubber mold friction material manufacturing process, and is generally disposed of as waste, The use of abrasive powder also reduces the amount of waste and recycles resources.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing a blend composition (% by weight) of friction materials (electromagnetic clutch linings) of Examples and Comparative Examples of the present invention
It is a table | surface figure which shows the result of the evaluation test of those friction materials.

FIG. 2 is a characteristic diagram showing a change with time of an initial friction coefficient at the time of a contact test of friction materials of Example 4 of the present invention, Comparative Examples 1 and 2.

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-61-162537 (JP, A) JP-A-63-293335 (JP, A) JP-A-5-86355 (JP, A) JP-A-5-86355 78649 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) F16D 69/02 F16D 13/62 C09K 3/14 C08J 5/14

Claims (1)

(57) [Claims] 1. A friction material obtained by thermoforming a mixture containing a fiber base material, a resin binder made of a thermosetting resin, and a filler, wherein at least a part of the filler is a rubber mold friction material. A friction material comprising the abrasive powder of the above in an amount of 10 to 70% by weight based on the whole friction material.