JPH04234477A - Dry friction material - Google Patents

Abstract

PURPOSE:To prevent judder in clutching. CONSTITUTION:A dry friction material comprising an organic fiber, an inorganic fiber, a metal wire, a filler and a binder and having a water absorption ratio of 2% or less after spraying misty water at a rate of 200cc/hour for 15 hours.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry friction material used primarily as a clutch facing.

0002

[Prior Art] The properties required for clutch facings include excellent heat resistance, abrasion resistance, an appropriate coefficient of friction, and excellent strength, and asbestos has traditionally been used as the base material. has been used. However, as it has become clear that asbestos has an adverse effect on the human body, there is a need for a base material to replace asbestos, and friction materials with various compositions have been proposed.

For example, JP-A-62-292937 discloses a friction material containing aromatic polyamide fibers as base fibers. Although aromatic polyamide fibers are organic fibers, they have excellent thermal performance and are suitable as base materials for friction materials.

0004

By the way, it is known that vibrations of 10 to 20 Hz called judder may occur during clutch engagement. This is explained as being caused by torsional resonance in the drive system due to fluctuations in clutch transmission torque. It is known that this judder tends to occur when starting the engine in the morning and is called morning judder, but the cause is not clear.

The present invention has been made in view of the above circumstances, and its main purpose is to prevent judder.

[0006]

[Means for Solving the Problems] The present inventors conducted intensive research to find out the cause of the occurrence of judder, and found that water has a large influence. If the moisture contained in the clutch facing exceeds a certain amount,
They discovered that judder occurs under certain conditions.

That is, when the clutch facing contains a large amount of water, the coefficient of friction is small at the initial stage of engagement with the mating plate due to the lubricating action of the water. It is clear that when the water gradually decreases due to frictional heat during engagement and the engagement progresses, judder will occur at some point before the water disappears, and after the water disappears, the engagement will return to normal. became. This phenomenon occurs when the clutch facing reaches a certain amount of water, forming an extremely thin film of water on the friction surface, which causes the clutch facing and the mating plate to come into close contact, causing large torque fluctuations. This was thought to be due to this. According to this theory, the reason why judder tends to occur when starting the engine in the morning can be clearly explained. That is,
During the night when the car is not in use, the clutch facing absorbs moisture, which causes the above phenomenon, and after a short period of parking, the amount of moisture absorbed is small, so judder does not occur.

Based on this knowledge, the present inventors completed the present invention by considering the prevention of moisture absorption in the clutch facing. That is, the dry friction material of the present invention that solves the above problems is made of organic fibers, inorganic fibers, metal wires, fillers, and binding materials,
It is characterized by having a water absorption rate of 2% or less after being sprayed at an amount of /hour for 15 hours.

[0009] As the organic fiber, the same materials as conventional ones such as pulp and various synthetic fibers can be used. Among these, aromatic polyamide fibers having excellent thermal properties and mechanical strength are preferred. It is desirable to use organic fibers having an equilibrium moisture content of 4% or less. Thereby, the water absorption rate of the entire friction material can be easily reduced to 2% by weight or less. Note that the organic fibers are generally comprised so as to occupy 10 to 40% by weight of the entire friction material. If the organic fiber content is less than 10% by weight, problems such as burst strength will occur;
When the amount increases, heat resistance, friction characteristics, etc. decrease.

As the inorganic fibers, conventional ones such as glass fibers, rock wool, and various ceramic fibers can be used. Since inorganic fibers generally do not absorb moisture easily, they can be used relatively freely. This inorganic fiber is
Generally, it is configured to account for 20 to 50% by weight of the entire friction material. If the inorganic fiber content is less than 20% by weight, problems will occur in heat resistance, frictional properties, etc., and if it is more than 50% by weight, burst strength, etc. will be reduced.

[0011] As the metal wire, conventionally used wires such as copper wire, brass wire, and stainless steel wire can be used. This metal wire generally accounts for 5 to 15% by weight of the entire friction material.
It is configured to occupy . If the metal wire is less than 5% by weight, the heat resistance will decrease, and if it is more than 15% by weight, the weight will increase and it will attack the mating material, which is not preferable.

[0012] As the filler, organic fillers such as cashew dust and resin powder, and inorganic fillers such as calcium carbonate, barium sulfate, metal powder, and graphite can be used in the same manner as conventionally. The appropriate amount is generally 2 to 20% by weight. As the bonding material, thermosetting resins having excellent heat resistance, such as melamine resin and phenol resin, can be used as in the past. Its blending amount is generally 15~
25% by weight is suitable. Note that if a high molecular weight straight phenolic resin is used, the water absorption rate of the entire friction material can be easily reduced to 2% or less.

[0013] Compounded rubber can also be used, and NBR, SBR, BR, etc. are used as the rubber elastomer, carbon black is used as the rubber reinforcing material, and sulfur is used as the vulcanizing agent, and the filler can be mixed with these. The blending amount is generally 15 to 65% by weight and is appropriately set based on performance and cost. The friction material of the present invention is formed from the above raw materials using a known molding method such as press molding.

The greatest feature of the present invention is that the water absorption rate of the entire friction material is 2% or less. Here, the water absorption rate is
It refers to the rate of increase in weight after spraying atomized water at a rate of 200 cc/hour onto a friction material for 15 hours. By setting this water absorption rate to 2% or less, judder can be reliably prevented. In order to keep the water absorption rate low in this way, it can be achieved by using raw materials with low water absorption as shown in the examples. In addition, in the case of friction materials containing compounded rubber components, judder may occur even if the water absorption rate is around 1%, so in such cases it is desirable to lower the water absorption rate to 0.5% or less. . Further, it is preferable not to perform sodium nitrite treatment, which has been conventionally performed to impart rust prevention performance, because it increases the water absorption rate.

[0015]

[Operations and Effects of the Invention] In the dry friction material of the present invention, the overall water absorption rate is suppressed to 2% or less. Therefore, since the amount of water is insufficient to form a thin film of water during engagement with the mating material, it is presumed that close contact with the mating material is prevented and fluctuations in torque are prevented. This can prevent judder from occurring.

[0016]

[Examples] Hereinafter, the present invention will be explained in detail using examples. (Example 1) The clutch facing of this example was made of aromatic polyamide fiber ("Kevlar #49") as an organic fiber.
” Manufactured by DuPont, equilibrium moisture content 3-3.5%) 20% by weight
and ceramic fibers as inorganic fibers (“SC bulk”)
20% by weight (manufactured by Shin Nihon Kagaku Co., Ltd.) and long glass fiber (9μ
135Tex" made by Nippon Glass Fiber Co., Ltd.), 5% by weight of cashew dust ("M103" made by Cashew Co., Ltd.) as an organic filler, and graphite (made by Nippon Glass Fiber Co., Ltd.) as an inorganic filler.
"PAG100" manufactured by Nippon Graphite Co., Ltd.) 5% by weight, brass wire as a metal wire ("#38" manufactured by Mie Senko Co., Ltd.) 10% by weight, and a melamine-modified phenol resin as a binding material (melamine / phenol = 70 / 30, manufactured by Sumitomo Duress Co., Ltd.) 20
It consists of % by weight.

[0017] As a method of manufacturing this clutch facing, the above-mentioned raw materials are mixed in the above-mentioned ratio, and the mixture is pressurized with a mold to preform. Then 150-200℃, 100-30℃
Heat and pressurize at 0 kg/cm2 for 1 to 10 minutes, and then heat treatment (usually 150 to 300°C, treatment time 3 to 16 hours)
to obtain a molded body. The surface of the molded body was then polished and the necessary holes were drilled to form the clutch facing.

Regarding the obtained clutch facing,
The water absorption rate and judder property were measured and the results are shown in Table 1. The water absorption rate was determined by humidifying the sample with a humidifier at a rate of 200 cc/hour for 15 hours, and measuring the rate of increase in weight before and after humidification. In addition, to check the judder property, attach the clutch facing to the car ("Crown" manufactured by Toyota Motor Corporation) and run the inside of the clutch housing with a humidifier for 20 minutes.
After humidifying at a rate of 0 cc/hour for 15 hours, the maximum value of starting acceleration was measured. Note that the maximum value of the starting acceleration without humidification is 0.08G. And the maximum value of starting acceleration is 0
．． It is known from experience that if it is less than 2, no judder will occur.

From Table 1, the water absorption rate of the clutch facing of this embodiment is as low as 1.48%, and as a result, the starting acceleration is as low as 0.13G, and judder is prevented. (Example 2) In this example, 20% by weight of aromatic polyamide fiber ("Kevlar #29" manufactured by DuPont, equilibrium moisture content 7%) was used as the organic fiber, and melamine-modified phenol resin (melamine/phenol resin) was used as the binder. =70/30,
The composition was the same as in Example 1, except that 16% by weight of a polymeric straight phenol resin ("Resin X" manufactured by Mitsubishi Yuka Co., Ltd.) was used. The water absorption rate and starting acceleration of this clutch facing were also measured in the same manner as in Example 1, and the results are shown in Table 1.

From Table 1, the water absorption rate of the clutch facing of this embodiment is as low as 1.80%, and as a result, the starting acceleration is as low as 0.16G, and judder is prevented. (Example 3) In this example, aromatic polyamide fiber (
35% by weight bulky fibers of Kevlar #49 (manufactured by DuPont, 100Tex) and long glass fibers ("9μ, 850Tex", manufactured by Nippon Glass Fiber Co., Ltd.), and 5% by weight of brass wire ("#40", manufactured by Mie Senko Co., Ltd.) A clutch facing was formed from the above, 10% by weight of a melamine-modified phenol resin (melamine/phenol = 70/30, manufactured by Sumitomo Durez Co., Ltd.) as a binder, and 50% by weight of compounded rubber. The compounded rubber is 100 parts by weight of SBR ("1502" manufactured by Nihon Gosei Rubber Co., Ltd.), 25 parts by weight of carbon black HAF, 20 parts by weight of cashew dust, 5 parts by weight of graphite, 50 parts by weight of calcium carbonate, 50 parts by weight of precipitated barium sulfate. , sulfur 30
parts by weight and 3 parts by weight of a vulcanization accelerator.

The water absorption rate and starting acceleration of this clutch facing were also measured in the same manner as in Example 1, and the results are shown in Table 1. From Table 1, the clutch facing of this example has an extremely low water absorption rate of 0.48%, which reduces the starting acceleration to 0.
．． As low as 18G, judder is prevented. (Comparative Example 1) Aromatic polyamide fiber ("
Kevlar #29” manufactured by DuPont, equilibrium moisture content 7%) 20
The structure is the same as in Example 1 except that weight % is used. The water absorption rate and starting acceleration of this clutch facing were also measured in the same manner as in Example 1, and the results are shown in Table 1.

[0022] From Table 1, this clutch facing has a high water absorption rate of 2.28%, which reduces the starting acceleration to 0.2%.
0G, which is higher than that of the example. Therefore, there is a possibility that judder may occur. (Comparative Example 2) For the clutch facing of Comparative Example 1,
After polishing, spray a 5% aqueous solution of sodium nitrite to 110
Sodium nitrite treatment was performed by drying at ℃ for 1 hour. The water absorption rate and starting acceleration of this clutch facing were also measured in the same manner as in Example 1, and the results are shown in Table 1.

Table 1 shows that this clutch facing has an extremely high water absorption rate of 4.58%, and as a result, the starting acceleration is 0.29G, which is much higher than that of the example. Therefore, it can be seen that judder is particularly likely to occur. (Comparative Example 3) For the clutch facing of Example 3,
A sodium nitrite treatment was performed in the same manner as in Comparative Example 2. The water absorption rate and starting acceleration of this clutch facing were also measured in the same manner as in Example 1, and the results are shown in Table 1.

Table 1 shows that this clutch facing has a relatively low water absorption rate of 1.02%, but a starting acceleration of 0.24G, which is higher than that of the example. Therefore, it can be seen that when compounded rubber is included, the water absorption rate needs to be lower than when it is not included. For example, by using the composition as in Example 3, the water absorption rate can be reduced to 0.5%.
It can be as follows.

[0025]

[Table 1] In other words, as in the example, the water absorption rate was 2 without compounded rubber.
% or less, and by setting it to 0.5% or less with compounded rubber, the maximum value of the starting acceleration becomes less than 0.2, and it is clear that the occurrence of judder can be prevented.

Claims (1)

[Claims] [Claim 1] Organic fibers, inorganic fibers, metal wires,
It consists of a filler and a binder, and 200cc/mist of water is
A dry friction material having a water absorption rate of 2% or less after being sprayed for 15 hours.