JP2014104384A - Powder coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brake pad coating method which can make a powdered paint adhere to the outer peripheral side surface of a pad part 3 even when the pad part 3 is insulative, and can make a coating film of the pad part 3 worn by braking thinner than the film thickness of a back plate 2.SOLUTION: In a powder coating method of a brake pad 1, which coats a powdered paint, discharged from a coating gun 7, on the outer surface of a metal back plate 2 other than the joint surface of an insulative pad part 3 and the outer peripheral side surface other than the friction surface of the pad part 3 in the brake pad 1 where the pad part 3 is joined to the back plate 2, before the powdered paint is sprayed, the back plate 2 and the pad part 3 are heated so that the temperature of the back plate 2 is made higher than that of the pad part 3.

Description

  The present invention relates to a method of coating a brake pad, in which a pad portion, which is a friction member, is bonded to a metal back plate (back metal) with a powder paint.

  Powder coating, which does not contain organic solvents and can collect and reuse overspray powder that has not adhered to the object to be coated, has been adopted in many products in recent years as an environmentally friendly coating.

  It started with road materials such as guardrails and fences, and is widely used in products used at home such as refrigerators and air conditioner outdoor units.

  Recently, in addition to automobile bodies, powder coating is used for painting automobile parts such as wipers and coil springs, and powder coating is also used for painting brake pads (Patent Document 1). ).

JP 2007-125522 A

  A brake pad is a metal back plate (back metal) bonded with a pad part that is a friction member. Conventionally, from the viewpoint of rust prevention and corrosion prevention, only the outer surface of the metal back plate is painted. There are many cases.

  However, since the brake pad is a part that can be seen through the gaps in the aluminum wheel, recently, from the viewpoint of design, not only the back plate, but also the outer surface of the pad part bonded to the back plate is painted except for the friction surface. It has come to be.

  The pad portion which is a friction member is formed by pressing and molding a molding material such as a base fiber, a filler, a friction modifier, and a resin binder.

  For the base fiber of the pad part, organic fiber such as aramid fiber, rayon fiber, nylon fiber, triacetate fiber, potassium titanate fiber, rock wool fiber, metal fiber such as steel fiber, stainless steel fiber, etc. Used in combination.

  Examples of the filler include alkaline earth metal sulfate such as barium sulfate, magnesium carbonate, lead sulfate, silica, mica, carbonate, talc, graphite, molybdenum disulfide solid lubricant, tire rubber powder, etc. Friction modifiers for metal powders such as organic powders, copper alloys, aluminum and zinc, and inorganic powders such as metal particles and graphite powder are used.

  Moreover, as a resin binder, phenol-type resin, polyimide-type resin, melamine-type resin, etc. are used.

  By the way, since the pad part of the brake pad is a wear part, if metal material is contained in the material of the pad part, scattering of metal powder becomes a problem of environmental hormones. The material is gradually removed and the pad portion is becoming insulating.

  When the metal material is included in the molding material of the pad part, the pad part is also conductive. Therefore, by grounding the pad part together with the back plate, the back plate and the pad part are electrostatically powdered. It is possible to paint.

  However, when the pad part becomes insulating, the adhesive force of the powder paint due to static electricity is weak, and when the powder paint is sprayed from the electrostatic paint gun, the powder paint once adheres to the pad part. However, the powder coating material adhering to the pad portion is blown away by the discharge air of the electrostatic coating gun.

  In particular, in the case of a friction charging type paint gun, since the frictional charging is performed by the strong conveying air, the air discharged together with the powder coating is also strong, and the powder coating adhering to the pad portion is easily blown off by the discharged air. .

  Insulating pad parts that do not easily adhere to such powder coatings should be preheated above the melt temperature of the powder coatings by placing the brake pads that are the objects to be coated in a heating furnace before spraying the powder coatings. Can be painted in the same way as the back plate.

  However, when the brake pad is preheated and painted, the film thickness of the insulating pad portion becomes the same as that of the back plate.

  When the film thickness of the pad portion is thick, when the pad portion is consumed by braking of the brake, the coating film on the pad portion is also consumed, and scattering of coating film components becomes a problem.

  Therefore, in order to reduce the scattering amount of the coating film component, it is desirable to make the thickness of the coating film of the pad portion thinner than the thickness of the coating film of the back plate.

  Therefore, the present invention can attach a powder coating material to the outer peripheral side surface of the pad portion even when the pad portion is insulative, and the coating film of the pad portion consumed by braking of the brake is applied to the film of the back plate. An object of the present invention is to provide a method of painting a brake pad that can be made thinner than the thickness.

In order to solve the above-described problems, the present invention provides a brake pad in which an insulating pad portion is bonded to a metal back plate, and friction between the outer surface of the back plate excluding the bonding surface of the pad portion and the pad portion. In the powder coating method for brake pads, in which the outer peripheral surface except the surface is painted with powder paint discharged from the paint gun, the back plate is heated so that the back plate is hotter than the pad before spraying the powder paint. The plate and the pad are heated.
In order to heat the back plate and the pad portion so that the back plate is hotter than the pad portion, the back plate is heated by high frequency induction heating, and the heat of the raised back plate is conducted to the pad portion. You can do it.
Alternatively, the back plate and the pad portion may be heated so that the far plate is irradiated with far infrared rays so that the back plate has a higher temperature than the pad portion.
As the coating gun, an electrostatic coating gun can be used.

  According to this invention, even when the pad portion is insulative, the powder coating can be adhered to the outer peripheral side surface of the pad portion, and the coating film of the pad portion that is consumed by braking of the brake is applied to the film of the back plate. It can be made thinner than the thickness.

It is the perspective view which looked at the brake pad which is a to-be-coated object of the powder coating method of this invention from the back plate side. It is the perspective view which looked at the brake pad which is a to-be-coated object of the powder coating method of this invention from the pad part side. It is the schematic which shows the coating line of 1st Embodiment of this invention. It is sectional drawing of a heating furnace provided with the high frequency heating apparatus used for 1st Embodiment of this invention. It is a schematic front view which shows the coating booth part of 1st Embodiment of this invention. It is a schematic plan view which shows the coating line of 2nd Embodiment of this invention. It is a schematic side view which shows the coating booth part of 2nd Embodiment of this invention. It is a schematic plan view which shows the coating line of 3rd Embodiment of this invention. It is sectional drawing of a heating furnace provided with the far-infrared apparatus used for 3rd Embodiment of this invention. It is a schematic perspective view which shows the coating gun of 3rd Embodiment of this invention. It is a schematic side view which shows the coating gun of 3rd Embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIGS. 1 and 2, a brake pad 1 that is an object to be coated by the powder coating method according to the present invention is obtained by joining a pad portion 3 that is a friction member to a metal back plate 2.

  The painted surface of the brake pad 1 that is the object to be coated is the outer surface of the metal back plate 2 excluding the bonding surface of the pad portion 3 and the outer peripheral side surface excluding the friction surface of the pad portion 3, and the pad portion 3 is insulated. Made of sex material.

  FIG. 3 shows a painting line A of the brake pad 1. The painting line A shown in FIG. 3 performs painting with a set of four brake pads 1, and the preheating line B also performs the preheating by arranging the four brake pads 1 in groups.

  The brake pad 1 is placed on the conveyor 4 with the pad portion 3 facing down on the preheating line B and the painting line A.

  In the preheating line B, two rows of high-frequency heating devices 5 are installed above a set of four brake pads 1 and are heated from above the metal back plate 2.

  The high-frequency heating device 5 can rapidly raise the temperature of the metal back plate 2 by only being turned on for a few seconds. For example, when the metal back plate 2 is heated for 1 to 1.5 seconds by a high-frequency heating device having an output of 15 KW, the temperature of the metal back plate 2 is increased to 150 ° C.

  Since the pad portion 3 is insulative, even if the high-frequency heating device 5 is turned on, high-frequency heating is not performed.

  The pad part 3 is heated by heat conduction through the contact surface with the metal back plate 2 whose temperature has been raised. Therefore, the temperature of the pad portion 3 can be set lower than the temperature of the metal back plate 2.

  For example, it takes about 4 minutes to raise the temperature of the pad 3 to 80 ° C. by the back plate 2 heated to 150 ° C.

  In the present invention, the coating is performed with the temperature of the back plate 2 and the pad portion 3 set lower than the temperature of the pad portion 3. That is, with respect to the back plate 2 heated to 150 ° C., the pad portion 3 is transferred to the coating line A while being heated to 80 ° C., and coating is performed in the coating booth 6.

  There is a temperature difference of 70 ° C. between the 150 ° C. back plate 2 and the 80 ° C. pad portion 3. When the brake pad 1 having this temperature difference is painted in the painting booth 6, the high temperature back plate Since a large amount of powder paint adheres to 2, a difference occurs in the film thicknesses of the back plate 2 and the pad part 3, and the film thickness of the pad part 3 can be reduced.

  In the painting line A shown in FIG. 3, grounding is performed from the back plate 2 side in the painting booth 6 and painting is performed using the painting gun 7. In this embodiment, the back plate 2 is heated to 150 ° C. Since the pad portion 3 is preheated to 80 ° C., the powder coating adheres to the back plate 2 and the pad portion 3 without grounding. A corona gun can be used as the coating gun 7.

  The brake pad 1 painted in the painting line A is guided to the baking / drying furnace 9 by the transfer conveyor 8.

  In the coating line A of FIG. 3, the back plate 2 was preheated to 150 ° C. and the pad portion 3 was preheated to 80 ° C., but the material and properties of the pad portion 3 (for example, moisture absorption in the pad), The temperature of the back plate 2 and the pad portion 3 is appropriately changed depending on the properties of the powder coating (the melting point of the coating, the glass transition point, etc.), the coating conditions, the atmosphere of the coating booth, and the like. However, in the present invention, it is important to set the temperature of the pad portion 3 lower than that of the back plate 2.

  For example, when the back plate 2 is applied at 150 ° C. and the pad portion 3 is applied at 80 ° C. (Embodiment 1 of the present invention), and when the back plate 2 and the pad portion 3 are both applied at 150 ° C. Table 1 shows a comparison between (Comparative Example 1) and the case where the back plate 2 and the pad portion 3 are both coated at room temperature (26 ° C.) (Comparative Example 2).

  As shown in Table 1, in Example 1, the thickness of the back plate 2 falls within the standard thickness (30 to 45 μm), and the thickness of the pad portion 3 is smaller than the thickness of the back plate 2 (20 to 30 μm). In the case of the comparative example 2 in which the back plate 2 and the pad portion 3 are preheated in a state where there is no temperature difference, the thickness of the pad portion 3 is larger than that of the back plate 2. It becomes thicker than the film thickness. Further, in the case of Comparative Example 3 in which the back plate 2 and the pad portion 3 were coated without preheating at room temperature, the powder coating material did not sufficiently adhere to the pad portion 3.

Table 1 shows the minimum value and the maximum value at three points for each of the four measurement points when four brake pads 1 were painted per test. The insulation resistance value of the pad portion 3 of the brake pad 1 subjected to the coating experiment was 4 × 10 ¹³ Ω (1000 V × 2000 MΩ resistance meter). The speed of the conveyor was 3.5 m / min, and the coating was performed at a total discharge rate of 50 g / min with two guns of a discharge rate of 26 g / min (1 gun) and a discharge rate of 24 g / min (1 gun). The powder coating used was an epoxy black.

  In Example 1 of Table 1, a high-frequency heating device with an output of 15 KW was used for preheating, and in Comparative Example 1, a hot-air circulating furnace (gas furnace) was used for preheating.

  Next, FIG. 6 shows a coating line A according to another embodiment of the present invention.

  In the painting line A of FIG. 6, two types of brake pads 11 in which the pad portion 3 is conductive and the brake pad 1 in which the pad portion 3 is insulative can be painted.

  Stock yards 10A and 10B for separately storing the brake pad 11 in which the pad portion 3 is conductive and the brake pad 1 in which the pad portion 3 is insulative are provided, and only the brake pad 1 in which the pad portion 3 is insulative is provided. In addition, the high frequency induction heating device 12 provided in the stock yard 10b performs preheating to perform coating.

  The brake pads transferred to the painting line A are placed on the movable carriage 13 and passed through the painting booth 14, and then conveyed to the baking / drying furnace 15.

  The movable carriage 13 is made of aluminum, and a resin mounting plate 16 having heat resistance is provided on the mounting surface of the brake pad 1 so that the preheated brake pad 1 can be directly carried into the painting booth 1. is set up. As resin which forms the mounting board 16, vinyl chloride and polyetheretherketone can be used, for example.

  On the upper surface of the mounting plate 16 on which the brake pad 1 is mounted, a grounding part 17 is installed so that the grounding can be performed from the pad part 3 of the brake pad 1.

  In the embodiment shown in FIG. 6, two friction charging paint guns are used as the paint gun 7. The frictional charging type paint gun discharges the powder paint together with the powder paint vigorously, so that the powder paint adhering to the object to be coated is not blown away by the discharge air. The discharged air is applied to the mounting surface of the movable carriage 13 so that the powder coating that has bounced off is indirectly applied to the object to be coated.

  In the embodiment shown in FIG. 6, in the case where the pad portion 3 is an insulating brake pad 1, after the back plate 2 is preheated to 80 ° C. and the pad portion 3 is 50 ° C. in the stock yard 10B. And sent to the painting booth 14.

This preheating temperature is set to a temperature lower than that in the embodiment of FIG. 3, but the powder coating sufficiently adheres to the insulating pad portion 3 at this temperature. The reason is that impurities such as moisture contained in the pad portion 3 are activated by preheating, and the insulation resistance value of the insulating pad portion 3 that was 2 × 10 ¹³ Ω at room temperature before preheating is as follows: This is considered to be due to the fact that the charged powder coating is liable to adhere to 4 × 10 ¹¹ Ω.

  Table 2 shows the results of coating the pad portion 3 with the insulating brake pad 1 and the pad portion 3 with the conductive brake pad 11 using the coating line A shown in FIG.

  In the case where the pad portion 3 is an insulating brake pad 1, the coating was performed by preheating the back plate 2 at 80 ° C. and the pad portion 3 at 51 ° C. (Example 2). In the case of the natural brake pad 11, the back plate 2 and the pad portion 3 were both coated at room temperature (27 ° C.) without preheating (Comparative Example 3).

  As shown in Table 2, when preheating is performed so that the temperature of the back plate 2 is higher than that of the pad portion 3 (Example 2), even if the pad portion 3 is insulative, the conductive pad portion 3, the thickness of the back plate 2 is kept within the standard thickness (25 to 45 μm), and the thickness of the pad portion 3 is precisely smaller than the thickness of the back plate 2 (15 to 30 μm). And settled.

Table 2 shows the minimum value and the maximum value of 3 points of each of the four measurement points when four brake pads 1 are painted per test. The insulation resistance value of the insulating pad part 3 subjected to the coating experiment was 2 × 10 ¹³ Ω at room temperature, but when preheated to 51 ° C., the insulation resistance value decreased to 4 × 10 ¹¹ Ω. . The moving carriage 13 was applied at a speed of 8.5 m / min, a discharge rate of 40 g / min (1 gun) and a discharge rate of 42 g / min (1 gun) and a total discharge rate of 82 g / min. The powder coating used was an epoxy black.

  Moreover, the high frequency induction heating apparatus 12 with an output of 10 KW was used for preheating.

  Next, in the painting line A of FIG. 8, the pad portion 3 is coated with the conductive brake pad 11 and the pad portion 3 of the insulating brake pad 1 is coated with the same line as in the painting line A of FIG. Is.

  In the painting line A in FIG. 8, an endless conveyor belt 18 passes through the painting booth 19. The conductive brake pad 11 is transferred from the right side in the traveling direction. On the other hand, the insulating brake pad 1 is transferred from the left side. The painting gun 7 uses a frictional charging type painting gun. Unlike the corona gun, the triboelectric charging gun does not concentrate the electric field due to free ions, and can suppress the thick film on the edge. When the pad part 3 is conductive, three pieces are set in series from the stock yard 10 </ b> A as they are (normal temperature) and transferred onto the conveyor belt 18. The transferred brake pad 11 passes through the painting booth 19 and is painted. In the embodiment of FIG. 8, in order to emphasize the uniformity of the film thickness, as shown in FIGS. 10 and 11, the gun tip branch nozzle 20 does not perform direct coating toward the object to be coated. That is, coating is performed by dispersing the discharge patterns so that the discharge patterns collide with each other.

  The brake pad 1 having the insulating pad portion 3 is provided with a stock yard 10B on the left side in the traveling direction, and the brake pad 1 is heated in the stock yard 10B. In the embodiment of FIG. 8, as shown in FIG. 9, a far-infrared device 21 such as a carbon heater is installed on the mesh-shaped transport belt 17 for preheating. Unlike a general furnace, the far-infrared device 21 can raise the temperature of only the directly irradiated part. Far-infrared rays include short waves, medium waves, and long waves, which are classified according to the temperature rise of the directly irradiated surface or inner surface. In this example, a medium wave was used. When the back plate 2 is transferred to the transport belt 18 from the far infrared device 21 on the upper surface, that is, the brake pad 1 aligned so that the pad portion 3 is installed on the transport belt 17, the back plate 2 When the temperature was 90 ° C., the pad portion 3 was set to 72 ° C. and coating was performed. The brake pad 1 is difficult to dampen once the temperature rises. The coating gun 7 was applied in the same discharge amount as that of the brake pad 11 having the conductive pad portion 3.

  Table 3 shows the results of coating the pad portion 3 with the insulating brake pad 1 and the pad portion 3 with the conductive brake pad 11 using the coating line shown in FIG.

  When the pad portion 3 is an insulating brake pad 11, preheating is performed and the back plate 2 is coated at 90 ° C. and the pad portion 3 is 72 ° C., and the pad portion 3 is a conductive brake pad 11. No preheating was performed, and both the back plate 2 and the pad portion 3 were coated at room temperature (28 ° C.).

  As shown in Table 3, when preheating is performed so that the temperature of the back plate 2 is higher than that of the pad portion 3 (Example 3), even if the pad portion 3 is insulative, the conductive pad As in the case of painting the brake pad 11 having the part 3 (Comparative Example 4), the film thickness of the back plate 2 falls within the standard film thickness (30 to 45 μm), and the film thickness of the pad part 3 is also the same as that of the back plate 2. It fits exactly in the standard film thickness (10-30 micrometers) thinner than a film thickness.

  Table 3 shows the minimum value and the maximum value of the three measurement points at three points when three brake pads 1 are painted per test. The conveyor belt 17 was coated at a speed of 4.0 m / min, a discharge rate of 39 g / min (1 gun) and a discharge rate of 36 g / min (1 gun) with a total discharge rate of 72 g / min. The powder coating used was an epoxy black.

  In addition, an infrared furnace manufactured by Helius was used for preheating.

DESCRIPTION OF SYMBOLS 1 Brake pad 2 Back plate 3 Pad part 4 Conveyor 5 High-frequency heating device 6 Coating booth 7 Coating gun 8 Transfer conveyor 9 Drying furnace 10A, 10B Stockyard 12 High-frequency induction heating device 13 Moving carriage 14 Coating booth 15 Drying furnace 16 Place plate 17 Grounding part 18 Conveying belt 19 Painting booth 20 Gun tip branch nozzle 21 Far infrared device

Claims (4)

  In the brake pad in which the insulating pad part is bonded to the metal back plate, the outer surface of the back plate excluding the bonding surface of the pad part and the outer peripheral side surface excluding the friction surface of the pad part were discharged from the paint gun. In a powder coating method for a brake pad to be coated with a powder coating, the back plate and the pad are heated so that the back plate is hotter than the pad before spraying the powder coating. Powder coating method for brake pads.   2. The brake pad powder coating method according to claim 1, wherein the back plate is heated by high frequency induction heating, and the heat of the raised back plate is conducted to the pad portion to heat the pad portion.   2. The brake pad powder coating method according to claim 1, wherein the back plate and the pad portion are heated so that the back plate is irradiated with far-infrared rays so that the temperature of the back plate is higher than that of the pad portion.   The powder coating method for a brake pad according to any one of claims 1 to 3, wherein an electrostatic coating gun is used as the coating gun.

Images