JP2003127155A - Method for degassing friction material in thermoforming process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a degassing method for preventing the occurrence of defective molding such as a crack and a blister and a thermoforming method for friction material which can obtain the friction material excellent in quality at a high temperature in a short time. SOLUTION: In the method for degassing the friction material in a thermoforming process, in a method for producing the material in which a preliminary molding of a raw material for the material is thermoformed by using a mold for thermoforming the material comprising a press mold, a middle mold, and a pressurization mold, temperature differences are formed in the press mold and the pressurization mold, a part in which the preliminary molding is last cured during thermoforming is biased toward the press mold or the pressurization mold, and a projection having a vent passage which is inserted into the final curing part and connected to the outside is formed in the press mold or the pressurization mold corresponding to the final curing part so that gas can be discharged from the final curing part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a degassing method in a thermoforming process for manufacturing a friction material, and more particularly to a thermoforming of a friction material used for industrial machines, railway vehicles, luggage vehicles, passenger cars and the like. The present invention relates to a degassing method in a process, and more specifically, to a degassing method in a thermoforming process such as a brake pad, a brake lining, and a clutch facing used for the above applications.

[0002]

2. Description of the Related Art Conventionally, friction materials mainly used for brakes of automobiles, railway vehicles, industrial machines, etc., generally include various fillers, various fibers for reinforcement, abrasives, graphite, metal Various resins are blended with a friction adjusting material such as powder as a binding material for binding these materials. In the manufacturing process of a brake pad for a disc brake, which is one example of a conventionally known method for manufacturing a friction material, it is molded into a predetermined shape by a sheet metal press, subjected to degreasing treatment and primer treatment, and then coated with an adhesive. Pressure plate, heat-resistant organic fiber, inorganic fiber, fiber base material such as metal fiber, inorganic / organic filler,
Mixing powder materials such as friction modifiers and binders (thermosetting resins such as phenolic resins), and thoroughly homogenizing the raw materials by stirring and molding at room temperature at a predetermined pressure (preforming)
In the thermoforming step, the preformed body produced in this way is thermoformed at a predetermined temperature and pressure so that both members are integrally fixed, aftercured, and finally finished.

In the thermoforming process, as shown in FIG. 8, the pressure plate (P / P) is used.
1 and the preform 2 of the friction material raw material, the metal middle mold 3,
Upper die 4 which is a pressing die and lower die (punch) 5 which is a pressure die
The above-mentioned material preform 2 is pressed by the upper die 4 and the lower die 5 together with the P / P 1 at the same time. The heating plate 7 provided on the lower die 5 is used to heat the preform 2 together with P / P1. Note that FIG.
In the above, P / P1 is arranged on the preform 2, but depending on the type of the apparatus, the preform 2 may be arranged on the P / P1, and the lower mold is a presser mold. The upper mold may be a pressure mold.

[0004]

In the thermoforming process of the preform 2 of the friction material raw material, gas is generated along with the thermosetting reaction of the organic binder (thermosetting resin) in the friction material raw material. Then, when the generated gas is confined inside the thermoformed friction material, the generated gas with a high gas pressure trapped inside the friction material is released at a dash during depressurization of the press pressure, causing cracks and blisters. Becomes However, in the conventional thermoforming die shown in FIG. 8, since it is made of the same material without paying particular attention to the thermal conductivity,
Heat is easily transferred from the middle mold 3 and the lower mold 5, and as a result, the surface of the friction material in contact with the middle mold 3 that contacts P / P1 and the friction surface that contacts the lower mold 5 are rapidly hardened, so that the gas is used as a friction material. There is a problem that it is trapped inside and causes the cracks 14 and blisters described above.

In order to prevent defective molding, the gas accumulated inside must be discharged. Further, in order to shorten the molding time, it is preferable to mold at a high temperature to accelerate the curing reaction of the organic binder. However, since the gas is concentratedly generated, there are many defective moldings. In order to solve the above-mentioned problem, several degassing methods have been proposed so far. For example, a method in which a large number of needles are provided in the upper mold or the lower mold, or a method of forming a gas vent hole by penetrating a protrusion to a depth close to the thickness of the friction material through a through hole provided in the pressure plate is proposed. ing. However, these methods
The method was not a method of degassing directly from the portion where the gas was collected, and the effect was insufficient.

The present invention has been made in view of the above-mentioned conventional problems, and a method of degassing for preventing the occurrence of molding defects such as cracks and blisters, and a friction material excellent in quality at high temperature for a short time. An object of the present invention is to provide a thermoforming method for a friction material obtained in 1.

[0007]

[Means for Solving the Problems] The inventors of the present invention have made various studies on a thermoforming mold and a molding method that do not cause molding defects such as cracks and blisters, and have found that in the friction material raw material during the thermoforming process of the friction material. It was found that the gas generated by the curing reaction of the thermosetting resin, which is the binder, is not smoothly degassed, which is the main cause of cracks and blisters. Then, the present inventors have completed the present invention based on the above findings.

That is, the present invention has solved the above problems by the following constitution. (1) In a method of manufacturing a friction material in which a preform of a friction material raw material is thermoformed using a friction material thermoforming die including a pressing die, a medium die, and a pressure die, a temperature difference is generated between the pressing die and the pressure die. Provided, the pre-molded body at the time of thermoforming the final curing portion is brought closer to one of the pressing mold or the pressing mold, and the pressing mold or the pressing mold corresponding to this final curing part is rushed into the final curing part, and A degassing method in a thermoforming process of a friction material, characterized in that a degassing passage communicating with the outside of the mold is provided to allow degassing from the final hardened part. (2) The pressure die is heated to a temperature higher than that of the press die to bring the final cured portion of the preform of the friction material raw material to the press die side, and the protrusion is formed on the press die to penetrate the hole in the pressure plate. (1) is characterized in that a gas vent hole is formed so as to penetrate into the final cured portion of the preform.
The degassing method of the described molding process. (3) The degassing method in the thermoforming process according to (1) or (2), wherein the protrusion is made of a material having a thermal conductivity smaller than that of the friction material.

(4) The pressing die is heated to a temperature higher than that of the pressing die, and a part of the middle die is made of a material having a lower thermal conductivity than the rest of the middle die, whereby the final cured part of the preform is obtained. Is closer to the material side of the heating die and the medium-sized material having low thermal conductivity, and the pressure die is provided with a projection having a gas vent hole that projects into the final curing portion, to form a gas vent passage. The degassing method in the thermoforming process according to any one of 1) to (3). (5) The degassing method in the thermoforming process according to (4), wherein a part of the middle die is made of a porous material. (6) The degassing method in the thermoforming process according to any one of (1) to (5), wherein the protrusion is made of fiber reinforced plastic.

That is, the skeleton of the present invention is a thermostat having both a means for collecting the gas by controlling the position of the final hardening portion of the preformed body to be thermoformed and a means for removing the gas collected in the final hardening portion. It is to thermoform a preform of the friction material using a forming die.

In the normal thermoforming process, the temperature distribution of the friction material is high at the outer periphery and low at the inner portion as shown in FIG. Usually, the friction material is integrally formed with an iron plate called a pressure plate (P / P). P / P absorbs heat from the mold and delays heat conduction to the friction material. Therefore, the lowest temperature part is slightly closer to the upper mold side from the center of the friction material. The coldest parts are voided because the organic binder is the last to cure. Therefore, the gas moves and collects in the “part where the organic binder is finally cured” (hereinafter, referred to as “final curing part”). When the press pressure is released in this state, the gas expands and cracks and blisters occur. In normal thermoforming, the temperature distribution is as shown in FIG. 8, so cracks occur in a portion of the friction material having a thickness of about ⅔.

That is, the present invention uses the following two means as the crack preventing means. 1) A means for collecting the gas by controlling the position of the final curing part. 2) A means for releasing the gas collected in the final curing section to the outside.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A degassing method in the thermoforming process of a friction material according to the present invention will be described in detail with reference to the drawings. In addition,
A component having the same function as the component shown in FIG.
It shows using the same code. Each of the above-mentioned two means will be described in detail below.

1) Means for Collecting Gas by Controlling Position of Final Hardening Section The amount of heat given from the mold to the friction material is made different so that the place where the gas is to be collected has the lowest temperature. A specific example will be given below and described with reference to the drawings. Example-1: In order to bring the final cured portion to the pressing die (upper die) 4, a large amount of heat may be applied from the pressure die (lower die) 5 (in the case of FIG. 1).・ The temperature of the lower die 5 is set higher than the temperature of the upper die 4. -Use a material having a higher thermal conductivity than the upper mold 4 material for the lower mold 5 material. -Use a material having a lower thermal conductivity than the material of the lower die 5 for the material of the upper die 4. -Use a porous material for the upper mold material to reduce heat conduction. (To move to the lower mold side, reverse the above)

Example-2 In order to bring the final cured portion to one side surface on the pressure die (lower die) 5 side, a method of bringing it to the lower die 5 side (Example 1)
(See the reverse case of step 1) and the following method (see FIG. 2). -Use a material with high thermal conductivity on the side opposite to the side that collects gas (medium size). -Use a material with low thermal conductivity for the side (medium size) on the gas collection side. -Use a porous material on the gas collecting side to reduce the thermal conductivity.

2) Means for venting gas from the final curing part (see FIG. 3)
And 4) The pressing die (upper die) 4 or the pressurizing die (lower die) 5 is provided with a degassing projection (hereinafter referred to as a projection) 8 (FIG. 3 (a) or (b)).
(Refer to FIG. 3), and degas the final curing part 6. The projection 8 is provided with a gas vent hole 9 and a gas vent groove 10 to allow gas to escape. When the friction material 2 is provided with a slit, the convex portion 12 is provided on the lower mold 5 corresponding to the slit to release the gas (see FIG. 4). In this case, since the slit is formed together with the thermoforming, the post-process can be omitted.

Here, if the final hardened portion 6 is controlled centering on the friction material 2, the projections 8 and the convex portions 12 become long. In order to shorten the length of the projection 8 or the convex portion 12, it is preferable to provide the projection 8 or the convex portion 12 on the side closer to the final cured portion 6. For example (see FIGS. 5 and 6) Example-1: Protrusion 8 when the final cured portion 6 is brought closer to the upper mold 4 side.
Is provided on the upper mold 4 (see FIG. 5). Example-2: When the final cured portion 6 is brought close to one side surface on the side of the lower mold 5, a protrusion 8 is provided on the lower mold 5 on the closer side (see FIG. 6).

Here, the thermal conductivity of the protrusions 8 and the protrusions 12 is
It must be equal to or less than the friction material 2. This is because when the thermal conductivity of the protrusions 8 and the protrusions 12 is higher than that of the friction material 2, the organic binder around the protrusions 8 and the protrusions 12 is cured first. The surroundings of the projections 8 and the convex portions 12 become dense and prevent gas venting. When the thermal conductivity of the protrusions 8 and the protrusions 12 is made equal to or less than that of the friction material 2, the organic binder around the protrusions 8 and the protrusions 12 is cured last. Then, a void can be secured around the protrusion 8 during the thermoforming process, and the gas can be easily released. The thermal conductivity of the friction material 2 is described below. The thermal conductivity of the protrusion 8 is adjusted depending on the type of the friction material 2. Non-asbestos: 1-3 W / mK Semi-metallic: 6-18 W / mK

[0019]

Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to this embodiment.

Examples 1 and 2, Comparative Examples 1 to 10 As shown in FIG. 7, thermoforming dies having a structure in which a pressing die (upper die) was provided with protrusions to release gas were produced. (A) shows the top view of a pressing die, (b) shows the longitudinal cross-sectional view of the whole thermoforming die. The protrusions of this example were made of fiber reinforced plastic (FRP) made of the following materials. Plastic: Polyimide resin. Reinforcing fiber: Carbon fiber. Filler: barium sulfate, calcium carbonate, magnesia. Protrusions with different thermal conductivity were produced by changing the type and amount of filler and reinforcing fiber mixed in the plastic. A protrusion having a thermal conductivity of 1 W / mK was used in Example 1 and a protrusion having a thermal conductivity of 5 W / mK was used in Example 2. In Comparative Example 1, the protrusion was made of SUS304 (heat conductivity: 15 W / mK) having a higher heat conductivity than the semi-metallic friction material (heat conductivity 12 W / mK).
In Comparative Example 2, a conventional mold having no protrusion was used. Friction material raw materials were mixed and stirred in the proportions shown in Table 1 to obtain a friction material agitated product.

[0021]

[Table 1]

The friction material agitated material is put into a preforming mold, and pressure-molded at a room temperature of 40 MPa to obtain 100 length × 40 width × thickness 2
A 0 mm preform was prepared. Next, the preform was put into a thermoforming die to perform thermoforming. The molding conditions were set as the following three conditions. The relationship between these molding conditions and Examples 1 and 2 and Comparative Examples 1 to 10 will be described together. In addition,
In Comparative Examples 3 to 10 of (1) and (2), the presence / absence of protrusions and the material of the protrusions were changed as in the case of (3).
(Figures in parentheses are molding time for semi-metallic compound) (1) Conventional molding conditions: upper mold temperature 155 ° C, lower mold temperature 1
55 ° C, molding time 420 seconds (410 seconds) ... Comparative Examples 7 to 10 (2) High temperature / short time molding conditions: upper mold temperature 175 ° C, lower mold temperature 175 ° C, molding time 90 seconds (75 Second) Comparative Examples 3 to 6 (3) High temperature / short time molding conditions: upper mold temperature 175 ° C., lower mold temperature 205 ° C., molding time 90 seconds (75 seconds) ・ ・ ・ Examples 1 and 2, In the conditions of Comparative Examples 1 to 2 * (3), the lower mold temperature was set to be 30 ° C. higher than the upper mold temperature in order to control the position of the final cured portion to the upper mold side.

After the thermoforming was completed, an appearance inspection and a tapping sound inspection were conducted to compare the defective molding rates. The test results are shown in Table 2.

[0024]

[Table 2]

[0025]

[Table 3]

In high-temperature, short-time molding, the molding defect rate of the molding die provided with the protrusion was small. Especially, when the thermal conductivity of the protrusions was smaller than that of the friction material, the defective molding rate was small. Furthermore, when the temperature of the pressurizing mold (lower mold) is raised by 30 ° C. higher than the temperature of the pressing mold (upper mold) to control the position of the final curing part,
It was possible to completely prevent molding defects. According to the present invention, it becomes possible to significantly shorten the molding time and mold with a high yield.

[0027]

According to the present invention, a thermoforming die is used which is provided with means such as providing a temperature difference between the pressing die and the pressure die.
It has become possible to control the position of the final hardened part and collect gas there, and to release the gas collected in this final hardened part. As a result, it is possible to prevent molding defects that occur during the thermoforming process, improve the product yield, and perform molding at high temperature and in a short time, thus reducing manufacturing costs.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a molding die that brings a final cured portion closer to a holding die side in the present invention.

FIG. 2 (a) is a vertical cross-sectional explanatory view of a molding die in which the final cured portion of the present invention is brought closer to one side surface on the pressure die side,
(B) is line XX cross section explanatory drawing of the shaping | molding die of (a).

FIG. 3 is a side view and a plan view of a gas venting projection according to the present invention, in which (a) is an illustration of a projection having a gas venting hole;
(B) is explanatory drawing of the protrusion which has a gas vent groove.

4A and 4B are explanatory views of a pressure die with a protrusion for degassing when a slit is provided in the friction material according to the present invention, FIG. 4A is a plan view of the pressure die, and FIG. 4B is a side view of the pressure die. Is.

FIG. 5 is an explanatory cross-sectional view of a molding die that brings the final cured portion closer to the holding die side in the present invention.

FIG. 6 is a cross-sectional explanatory view of a molding die in which the final cured portion of the present invention is brought close to one side surface of the pressure die.

FIG. 7 shows a molding die used in an example of the present invention, in which (a) is a plan view and (b) is a cross-sectional explanatory view.

FIG. 8 is a sectional view of a molding die for explaining a friction material temperature distribution in a conventional thermoforming process.

[Explanation of symbols]

1 Pressure plate (P / P) 2 Preform of friction material 3 medium 3A Medium size (low thermal conductivity, porous) 3B Medium size (high thermal conductivity) 4 Presser type (upper type) 5 Pressurized type (lower type) 6 Final curing part (lowest temperature part) 7 hot plate 8 protrusions 9 Venting hole 10 Venting groove 11 Venting path 12 Projection 13 Dore hole 14 Crack

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Kusaka             Saitama Prefecture Hanyu City East 5-4-71 Co., Ltd.             Akebono Brake Central Technology Research Institute (72) Inventor Kurihara             Saitama Prefecture Hanyu City East 5-4-71 Co., Ltd.             Akebono Brake Central Technology Research Institute F term (reference) 3J058 BA61 FA01 FA11 FA21 FA35                       GA63 GA65 GA92 GA93                 4F202 AA37 AH81 AJ04 AJ10 AJ12                       CA09 CB01 CK42 CP01 CP02                       CP04                 4F204 AA36 AA40 AB11 AB16 AB18                       AB25 AE08 AH17 AJ04 AJ10                       AJ12 FA01 FB01 FF01 FN01                       FN12 FN16 FQ15

Claims (6)

[Claims] 1. A method for producing a friction material in which a preform of a friction material raw material is thermoformed using a die for thermoforming a friction material, which comprises a holding die, a medium die and a pressure die, and a temperature is applied to the holding die and the pressure die. A difference is provided, and the part where the preform is finally cured during thermoforming is brought closer to either the pressing mold or the pressing mold,
It is possible to vent gas from the final curing section by providing a pressing die or a pressurizing die corresponding to the final curing section with a projection having a gas vent passage leading to the outside of the die. A method of degassing during the thermoforming process of a friction material. 2. The pressure die is set to a temperature higher than that of the pressing die to bring the final cured portion of the preform of the friction material raw material toward the pressing die side, and the projection is formed on the pressing die to form the hole portion of the pressure plate. The degassing method in the thermoforming process of the friction material according to claim 1, wherein a degassing hole is formed so as to penetrate therethrough and to enter the final cured portion of the preformed body. 3. The degassing method in the thermoforming process of the friction material according to claim 1, wherein the protrusion is made of a material having a thermal conductivity smaller than that of the friction material. 4. The pressing die is heated to a temperature higher than that of the pressing die, and a part of the middle die is made of a material having a lower thermal conductivity than the rest of the middle die, whereby a final cured portion of the preform is formed. 2. The degassing path is formed by providing a protrusion having a degassing hole that projects toward the final hardening portion on the pressurizing die side and toward the material side having a low thermal conductivity of the medium die. 4. A degassing method in the thermoforming process of the friction material according to claim 3. 5. The degassing method in the thermoforming process of the friction material according to claim 4, wherein a part of the middle die is made of a porous material. 6. The degassing method in the thermoforming process of the friction material according to claim 1, wherein the protrusion is made of fiber reinforced plastic.