JP2014193424A - Airless coating device and airless coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a size of paint particles as compared with a case using a fan spray nozzle and reduce generation of a tail.SOLUTION: The airless coating device, which has a flow path 40 for paint 41 and comprises a nozzle 23 having an orifice 27 provided on a downstream end of the flow path 40, pressurizes the paint 41 to be sprayed from the orifice 27. In the nozzle 23, a chamber 35 is provided at a further upstream side than the orifice 27 of the flow path 40. In the nozzle 23, the pressurized paint 41 is supplied to the further upstream side than the chamber 35 of the flow path 40, and in an opening 37 at a downstream end of the device is provided a groove 36 that is connected to the chamber 35 to guide the paint 41 from the opening 37 to a direction along an inner wall surface 26a of the chamber 35.

Description

  The present invention relates to an airless coating apparatus and an airless coating method in which paint is pressurized and sprayed from a nozzle.

  As one aspect of an airless coating apparatus that performs coating without using compressed air, there is known an apparatus that injects pressurized liquid paint at a high pressure from an orifice of a fan spray nozzle attached to the tip of a spray gun. (For example, refer to Patent Document 1). As shown in FIG. 13, in this type of airless coating apparatus, the paint 53 is atomized after being sprayed from the orifice 52 of the fan spray nozzle 51. In FIG. 13, a region surrounded by a two-dot chain line indicates a spray pattern having a cross-sectional shape when the sprayed paint diffuses.

  The atomization of the paint 53 is considered to occur as follows. When the paint 53 is pushed out from the orifice 52 at a high pressure, the paint 53 flies in a direction in which the spray pattern 54 is widened away from the orifice 52 (a direction away from the central axis L3 of the fan spray nozzle 51). The paint 53 forms a film at a location close to the orifice 52. However, as the distance from the orifice 52 increases, the surface tension overcomes the force for maintaining the form of the film, and the paint 53 is torn off. Even after the paint 53 is torn off, the paint 53 flies in the direction of spreading the spray pattern 54 and is torn off again. In this way, the coating 53 is atomized by repeating the phenomenon of flying and tearing in the direction of spreading the spray pattern 54.

  Then, as shown in FIG. 14, the paint particles 55 adhere to the article CM. Each paint particle 55 flows and becomes flat after adhering to the article CM, and fuses with other paint particles (not shown) located near the article CM. By performing this fusion on a large number of paint particles 55, a coating film (not shown) is formed on the surface of the article CM.

  The airless coating apparatus of the above type has the advantage that the coating particles 55 are less scattered and the coating efficiency is higher than that of an air spray coating apparatus that sprays paint in a mist form with compressed air.

JP 2009-248020 A

  However, in the airless coating apparatus of the type using the fan spray nozzle 51, the particle diameter of the paint particles 55 when the paint is atomized is large. Strictly speaking, it is possible to reduce the particle size of the paint particles 55 somewhat by increasing the supply pressure of the paint to the fan spray nozzle 51. However, as the supply pressure is increased, the injection amount of the paint increases. Because it becomes, it is not realistic. Therefore, in the type of airless coating apparatus using the fan spray nozzle 51, there is a problem that usable coating forms are limited. For example, as one of the forms of painting that uses interior and exterior products of vehicles as a coating, a coating film having a metallic luster by using a paint in which a color pigment and a fine flake of metal such as aluminum are mixed in a solvent There is a so-called metallic coating that forms In this metallic coating, generally, the high quality is that the flakes are dispersed in the coating film in a state substantially parallel to the surface of the interior / exterior product. This is because the light incident on the coating film is thin and regular reflection (incidence angle and reflection angle are equal, and the reflected light is a parallel light) and is rich in glitter.

  In this regard, in the airless coating apparatus of the type using the fan spray nozzle 51, a large number of flakes are likely to be included in the paint particles having a large particle diameter. And as shown in FIG. 14, many thin pieces 57 overlap because the coating-material particle | grains 55 adhere to the to-be-coated article CM. If the thin pieces 57 remain attached to each other when the paint particles 55 flow after the attachment to the object CM, it becomes difficult to disperse the thin pieces 57 cleanly in the coating film. As a result, the light incident on the coating film is likely to be reflected (diffuse reflection) at an angle (reflection angle) different from the incident angle, and it is difficult to obtain a glittering feeling. Therefore, it is difficult for the airless coating apparatus of the type using the fan spray nozzle 51 to perform high-quality metallic coating rich in glitter on the interior and exterior products of the vehicle.

  Further, as shown in FIG. 13, in the airless coating apparatus of the type using the fan spray nozzle 51, a portion having a larger film thickness than the other portion, called a tail, is likely to occur in the outer edge portion 54O of the spray pattern 54. This deteriorates the appearance quality of the coating film. For example, the tail is considered to be generated by the following phenomenon. In the process of atomization of the paint described above, the paint located in the intermediate portion 54I of the spray pattern 54 can easily fly in the direction of expanding the spray pattern 54, but the paint located in the outer edge portion 54O is more than that. It is difficult to fly in the direction of spreading the spray pattern 54. The latter paint is subjected to a force that causes the spray pattern 54 to fly in the direction of contraction due to intermolecular force or the like. Therefore, more paint flies in the outer edge portion 54O of the spray pattern 54 than in the intermediate portion 54I. Then, the coating material adheres to the object CM, so that a coating film having a thickness larger than that of the intermediate portion 54I is formed at the outer edge portion 54O of the spray pattern 54.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an airless coating apparatus capable of reducing the size of paint particles and suppressing the occurrence of tails compared to the case of using a fan spray nozzle. And providing an airless coating method.

  An airless coating apparatus that solves the above-described problem is an airless coating apparatus that includes a nozzle having a paint flow path and an orifice provided at a downstream end of the flow path, and pressurizes the paint to be sprayed from the orifice. A chamber is provided upstream of the orifice of the flow path in the nozzle, and pressurized paint is supplied upstream of the chamber of the flow path in the nozzle; and A groove is provided in the opening at the downstream end of the chamber, connected to the chamber, and guides the paint from the opening in a direction along the inner wall surface of the chamber.

  An airless coating method for solving the above-described problem is an airless coating method in which pressurized paint is supplied to a flow path of a nozzle and sprayed from an orifice at a downstream end of the flow path. A chamber is provided on the upstream side of the orifice of the passage, and on the upstream side of the chamber, a groove connected to the chamber is provided at the opening at the downstream end of the chamber. The paint flowing through the groove in the path is guided from the opening in a direction along the inner wall surface of the chamber.

  According to the above configuration and method, when pressurized paint is supplied to the groove of the nozzle, the paint flows through the groove and is guided from the opening at the downstream end of the groove in a direction along the inner wall surface of the chamber. The coating material swirls in the chamber by flowing along the inner wall surface.

  When the paint is sprayed from the orifice, it turns away from the orifice. This swirl is performed to enlarge the spray pattern as it moves away from the orifice. The paint forms a film near the orifice. However, as the distance from the orifice increases, the surface tension overcomes the force that tries to maintain the shape of the film, and the paint tears. Even after the paint is torn off, the paint flies in the direction of spreading the spray pattern and is torn off again. In this way, the phenomenon that the spray pattern spreads in the direction of expanding the spray pattern while turning is repeated, so that the paint is atomized into paint particles having a smaller particle diameter than when the fan spray nozzle is used.

  A large number of paint particles adhere to the object to be coated. Each paint particle flows and becomes flat after adhering to the object to be coated, and fuses with other paint particles located close to the object to be coated. A coating film is formed on an object to be coated by performing the above-mentioned fusion on a large number of paint particles.

  Here, when the form of painting is metallic painting, the number of metal flakes contained in the paint particles decreases as the particle diameter of the paint particles decreases. Then, paint particles containing a small number of metal flakes adhere to the object. The adhered paint particles flow and extend along the surface of the object to be coated, so that the metal flakes in the paint particles become substantially parallel to the surface of the object to be coated. A large number of coating particles adhere to the object to be fused together, whereby a coating film in which a large number of metal flakes are separated (dispersed) from each other is formed on the surface of the object to be coated. When light is incident on this coating film, the light hits the metal flakes and is easily regularly reflected, resulting in a rich glitter.

Note that the small particle size of the paint particles is effective in improving the appearance quality not only in metallic coating but also in coating films formed by other coating forms such as solid coating.
In addition, the paint including the metal flakes flies while turning as described above. The radius of swirling of the paint and flakes increases as the distance from the orifice increases. Therefore, in the process of atomization of the paint, the paint located in the middle part of the spray pattern and the paint located in the outer edge part can fly in the direction of expanding the spray pattern. And a coating film which has a thickness comparable as an intermediate part is formed also in the outer edge part of a spray pattern because a coating material adheres to a to-be-coated article. The phenomenon that a tail, which is a thick part, is hardly generated at the outer edge portion of the spray pattern.

  In the airless coating apparatus, at least a part of the nozzle is configured by a combination of a housing and a core. The housing opens at an upstream end surface of the housing, and is at least downstream of the core. An attaching portion to which an end portion is attached; a tapered portion which is provided on the downstream side of the attaching portion and decreases in diameter as it moves away from the attaching portion; and from the inner bottom portion of the tapered portion to the downstream side The orifice extending and opening at the downstream end face of the housing is formed, and the chamber is surrounded by a space surrounded by the downstream end face of the core attached to the adherent portion and the inner wall surface of the tapered portion It is preferable that the groove is provided at a location connecting the outer peripheral surface of the core and the downstream end surface in the core.

  According to the above configuration, when at least the end portion on the downstream side of the core is attached to the adherend portion of the housing, a space surrounded by the downstream end surface of the core and the inner wall surface of the tapered portion of the housing is generated. This space functions as a chamber.

  Then, when the pressurized paint is supplied to the outer peripheral surface of the core, the paint flows along the groove and is guided in the direction along the inner wall surface of the chamber from the opening provided in the end face on the downstream side of the core. The coating material swirls within the chamber by flowing along the tapered portion whose diameter decreases as it moves away from the adherend portion.

  In the airless coating apparatus, an end surface on the downstream side of the core is formed by a circular plane, and the groove extends from the outer peripheral surface of the core in a direction along a tangent to the end surface, and the outer peripheral portion of the end surface has the It is preferable to have an opening.

  According to said structure, the coating material which flows along a groove | channel is guide | induced to the direction in alignment with the tangent of the end surface from the opening provided in the outer peripheral part in the end surface of the downstream of a core. As the paint flows along the tapered inner wall surface, a strong swirling flow of the paint is generated in the chamber.

  In the airless coating apparatus, the coating material supplied to the nozzle includes metal flakes, and the atomized coating particles sprayed from the orifice of the nozzle have an average particle size after adhering to the object to be coated. It is preferable that the diameter is 35 μm or less.

  According to said structure, the high voltage | pressure coating material containing the metal thin piece is supplied to the groove | channel of a nozzle. The metal flakes, along with the paint, are ejected from the orifice after passing through the groove and chamber. The paint containing the metal flakes is atomized in the process of moving away from the orifice. Within the atomized paint particles may be several metal flakes. The paint particles adhere to the object to be coated. The adhered paint particles flow and extend along the surface of the object to be coated, so that the metal flakes are substantially parallel to the surface of the object to be coated. A large number of coating particles adhere to the object to be fused together, whereby a coating film in which a large number of metal flakes are separated (dispersed) from each other is formed on the surface of the object to be coated.

  Here, the metal flakes contained in the paint used when the interior / exterior product of the vehicle is painted metallic generally has an average particle diameter of about 20 μm. It is desirable that the coating particles in which several pieces of metal flakes with this average particle diameter can enter have an average particle diameter of 35 μm or less when attached to the object. As described above, since the coating particles flow and become flat after adhering to the object to be coated, the average particle size after the atomization and before adhering to the object to be coated (in flight) is smaller than 35 μm. Have a diameter.

  Therefore, when the paint particles adhere to the object to be flattened, the paint particles can contain several metal flakes, and the flakes are on the surface of the object to be coated. It becomes a state substantially parallel to. A large number of paint particles adhering to the object to be coated are fused together to form a coating film in which a large number of metal flakes are separated (dispersed) from each other on the surface of the object to be coated.

  In the airless coating apparatus, when water is sprayed from the orifice of the nozzle in place of the paint and atomized, the water particles have a size with an average particle diameter of 20 μm or less during flight. It is preferable.

  In the airless coating apparatus, the inner diameter of the orifice is in the range of 0.1 mm to 0.4 mm, the supply pressure of the paint supplied to the groove is in the range of 5 MPa to 15 MPa, and the area of the opening in the groove Is the uppermost stream part of the chamber, where X is the supply pressure of the paint supplied to the groove when the total sum is 0.1 mm ^ 2 ("^" represents a power) to 0.6 mm ^ 2 When the ratio of the diameter at the depth to the depth of the same chamber is Y, the inner diameter of the orifice, the paint so that the ratio Y is not less than the value obtained by the following equation and not more than 5.0 It is preferable that the supply pressure, the total area of the openings, the diameter at the most upstream part of the chamber, and the depth of the chamber are set.

Formula: Y = 0.005X + 0.175
By satisfying the above conditions, it becomes possible to include several metal flakes in each paint particle when the paint containing the metal flakes is made into fine particles. A plurality of coating particles adhere to the object to be coated, become flattened, and fuse with each other, thereby forming a coating film in which metal flakes are dispersed.

  Note that the total area of the openings depends on the length, width, and number in the direction along the groove. Therefore, by appropriately setting the length, width, and number of the openings, the total area of the openings in the groove can be made closer to 0.1 mm ^ 2 to 0.6 mm ^ 2.

  Appropriate settings are: the opening length is set to 0.11 mm to 0.33 mm, the opening width is set to 0.15 mm to 0.25 mm, and the number of openings is set to 2 to 4 Is Rukoto.

  According to the airless coating apparatus and the airless coating method, it is possible to make the paint particles smaller than when a fan spray nozzle is used, and to suppress the generation of tails.

It is a figure which shows one Embodiment of an airless coating apparatus and the airless coating method, and is a schematic block diagram of the same coating apparatus. The fragmentary sectional view of the nozzle used for the airless painting device in one embodiment. The fragmentary sectional view shown in the state which decomposed | disassembled the housing and core in the nozzle of FIG. The fragmentary perspective view of the core in FIG. The front view which shows the state which looked at the core of FIG. 4 from the direction shown by arrow A. FIG. In one embodiment, the fragmentary sectional view which shows notionally how a coating material flows in the chamber of a nozzle, and is injected from an orifice. The graph explaining the area | region required in order to adhere the coating particle of an average particle diameter of 35 micrometers or less to a to-be-coated article in the relationship between the ratio of the diameter and depth of a chamber, and the supply pressure of a coating material in one Embodiment. In one Embodiment, the fragmentary sectional view which expands and shows the state by which the coating particle containing the metal flake adhered to the surface of the to-be-coated object, and flowed and became flat. In one Embodiment, the fragmentary sectional view which expands and shows the state in which the coating film in which the thin piece of metal was disperse | distributed was formed in the surface of to-be-coated object. It is a figure explaining the modification with which the groove | channel was provided in two places of the core, and the front view which shows the groove | channel and peripheral part in a core. It is a figure explaining the modification by which the groove | channel was provided in three places of the core, and the front view which shows the groove | channel and peripheral part in a core. It is a figure explaining the modification of a groove | channel, and is a front view which shows the groove | channel and peripheral part in a core. It is a figure for demonstrating a prior art, and is a partial perspective view which shows a mode that a coating material is injected from the fan spray nozzle of an airless coating apparatus. It is a figure for demonstrating a prior art, it expands the state where the coating particle which sprayed from the fan spray nozzle, atomized, and the metal particle including the metal flakes adhered to the surface of the object, and flowed and became flat. FIG.

  Hereinafter, as an embodiment of an airless coating apparatus and an airless coating method, an airless coating apparatus used when an interior / exterior product of a vehicle is a coating object and a coating film is formed on the surface of the coating object, and the apparatus An airless coating method performed using the above will be described with reference to FIGS.

  As shown in FIG. 1, the airless coating apparatus 10 of this embodiment includes a plurality of paint tanks 11a, 11b, 11c, low pressure pumps 18a, 18b, 18c, a color change device (CCV: color change valve) 15, and a high pressure pump 20. And a regulator 21 and an airless gun 22.

  Different types of paint are stored in the paint tanks 11a, 11b, and 11c. Paints to be stored are generally used for painting interior and exterior parts of vehicles. Typical paints for solid paint, paint for metallic paint, paint for clear paint, and paint for pearl paint are typical. is there. In the present embodiment, the paint for metallic coating containing fine flakes of metal such as aluminum is stored in the paint tank 11a, and the paint for solid coating not containing metal flakes is stored in the paint tank 11b. ing. The metal flakes contained in the metallic paint for interior and exterior products of vehicles generally have an average particle size of about 20 μm.

  The color changing device 15 is for switching the type of paint supplied to the nozzle 23 of the airless gun 22 and incorporates the same number of valves as the paint tanks 11a, 11b, and 11c. The color change device 15 is also provided with a cleaning circuit.

  The paint tank 11a is connected to the color changing device 15 by the paint supply path 16a, the paint tank 11b is connected by the paint supply path 16b, and the paint tank 11c is connected by the paint supply path 16c. Each of the coating material supply paths 16a, 16b, and 16c is configured by a commonly used hose having a strength that can withstand a low-pressure coating material.

  The low pressure pump 18a is provided in the paint supply path 16a, the low pressure pump 18b is provided in the paint supply path 16b, and the low pressure pump 18c is provided in the paint supply path 16c. The low-pressure pumps 18a, 18b, and 18c are pumps that deliver paint at a low pressure of about 0.2 MPa to 0.3 MPa, for example, move the diaphragm (membrane) up and down or left and right to change the volume, and suck and discharge A diaphragm type pump is used.

The airless gun 22 is for injecting paint toward the object to be coated, and is connected to the color changing device 15 through the paint supply path 19.
The high-pressure pump 20 is for increasing the pressure of the paint after being sent from any of the low-pressure pumps 18a, 18b, and 18c and passing through the color changing device 15 to a high pressure of about 5 MPa to 15 MPa. In the present embodiment, as the high-pressure pump 20, a type driven by air is used, but other types, for example, a type driven by electricity may be used. The high-pressure pump 20 is disposed in the vicinity of the upstream side of the airless gun 22 in the paint supply path 19. The regulator 21 is for controlling the pressure of the paint increased by the high-pressure pump 20 to be a target value. Note that at least a portion downstream of the high-pressure pump 20 in the paint supply path 19 is constituted by a high-pressure hose having a strength capable of withstanding the paint that has been increased in pressure by the high-pressure pump 20 to a high pressure.

  As each paint tank 11a, 11b, 11c, low-pressure pumps 18a, 18b, 18c, paint supply passages 16a, 16b, 16c, and color changing device 15, a conventional air spray painting facility that performs painting using compressed air is used. Is possible.

  The airless gun 22 incorporates a nozzle 23 for spraying paint. As shown in FIG. 2, a part of the nozzle 23 is configured by a combination of a housing 24 and a core 30 attached to the housing 24. As shown in FIG. 3, the housing 24 and the core 30 are formed with a high-pressure paint flow path 40 that has passed through the high-pressure pump 20 and the regulator 21.

In the housing 24, an adherend portion 25, a tapered portion 26, and an orifice 27 are formed in this order from the upstream side (left side in FIG. 3) to the downstream side (right side in FIG. 3).
The adherend portion 25 has two types of surfaces 25a and 25b. One surface 25 a opens in a circular shape on the upstream end surface 24 a of the housing 24. The surface 25a has a cylindrical shape with a constant inner diameter at any location along the central axis L1 of the housing 24. The other surface 25b is inclined with respect to the central axis L1 and has a tapered shape with a diameter decreasing toward the downstream side.

  The tapered portion 26 is provided on the downstream side of the surface 25 b of the adherend portion 25. The taper portion 26 has an inner wall surface 26a that decreases in diameter toward the downstream side. The inner wall surface 26a is a surface constituting an inner wall surface of the chamber 35 described later.

  The orifice 27 is a location that functions as a spray port for the paint, and opens at a location on the central axis L <b> 1 on the downstream end face 24 b of the housing 24. The orifice 27 has a circular cross section, and is configured by a hole having the same inner diameter at any location in the direction along the central axis L1, and is connected to the inner bottom portion (the most downstream portion) of the tapered portion 26. Yes.

  On the other hand, the core 30 has a columnar main body 31 having an outer diameter substantially the same as the inner diameter of the cylindrical surface 25 a in the adherend portion 25. At the downstream end of the main body 31, a shape corresponding to the surface 25b, that is, a tapered annular contact surface 32 having a diameter reduced toward the downstream side is formed. A downstream end surface 33 surrounded by the annular contact surface 32 in the main body 31 is configured by a circular plane orthogonal to the central axis L <b> 2 of the core 30.

  As shown in FIG. 2, the core 30 (the main body 31) is fitted into the adherend 25 at the downstream end thereof, so that the core 30 is attached to the housing 24. In this mounted state, a part (downstream part) of the outer peripheral surface 34 of the core 30 (main body 31) is in contact with the surface 25a, and the annular contact surface 32 is in contact with the surface 25b. A space surrounded by the inner wall surface 26a of the tapered portion 26 and the end surface 33 of the core 30 (main body portion 31) constitutes a chamber 35 for generating a swirling flow of paint.

  A groove 36 that connects the outer peripheral surface 34 of the main body 31 and the downstream end surface 33 is formed at the downstream end of the core 30. As shown in FIG. 4, in the present embodiment, the grooves 36 are provided at a plurality of locations (four locations) of the main body 31. Each groove 36 extends from the outer peripheral surface 34 of the main body portion 31 in a direction along the tangent line of the downstream end surface 33. As shown in FIG. 5, each groove 36 has a body portion 31 when the core 30 is viewed from one side in the direction along the central axis L <b> 2. Extends from the outer peripheral surface 34 to the tangential direction of the downstream end surface 33. The inner bottom surface of each groove 36 is inclined at a groove angle θ with respect to the end face 33 as indicated by a broken line in FIG. As shown in FIG. 5, the downstream end of each groove 36 has an opening 37 at the outer peripheral portion of the end surface 33, that is, at the boundary portion with the annular contact surface 32 of the end surface 33. The plurality of grooves 36 are provided around the central axis L <b> 2 of the core 30 at equal angles (90 °) or at substantially equal angles.

  Here, as shown in FIGS. 3 and 4, the supply pressure of the paint supplied to each groove 36 is X, and the ratio (D1) of the diameter D1 at the most upstream part of the chamber 35 to the depth D2 of the chamber 35 / D2) is Y.

  FIG. 7 shows factors such as the inner diameter D3 of the orifice 27, the supply pressure X of the paint, the total area SA of the openings 37 in the groove 36, the diameter D1 at the most upstream portion of the chamber 35, and the depth D2 of the chamber 35. The combination of these factors is set at multiple levels, and the results of an experiment in which paint is sprayed from the nozzle 23 for each level to adhere to the object to be coated are analyzed. The opening 37 for each groove 36 is indicated by a halftone dot in FIG. 5, and the area of the portion with the halftone dot is the area of the opening 37. The total SA is the sum of the areas of the openings 37 for all the grooves 36.

  Referring to FIG. 7, in the present embodiment, after satisfying all of the following conditions 1 to 3, the ratio Y is not less than the value obtained by the following formula 1 and not more than 5.0. In addition, the inner diameter D3 of the orifice 27, the paint supply pressure X, the total area SA of the openings 37, the diameter D1 and the depth D2 of the chamber 35 are set. This is a condition necessary for making the average particle diameter of the coating particles when adhered to the object to be coated and flattened to be 35 μm or less. Further, when water is sprayed from the orifice 27 of the nozzle 23 and atomized instead of the paint, it is also a necessary condition for making the average particle size (Sauter average particle size) of flying water particles 20 μm or less. . The average particle size of water particles in flight is a value obtained by measuring the average particle size of water particles flying at a location 80 mm away from the nozzle 23 using a commercially available measurement device that performs measurement by irradiating a laser beam. is there. The average particle size of 35 μm or less for the paint particles and the average particle size of 20 μm or less for the water particles are several pieces (for example, 5 or less) of metal flakes in which one paint particle has an average particle size of about 20 μm. 42 is a particle size that can contain 42.

Condition 1: The inner diameter D3 of the orifice 27 is in the range of 0.1 mm to 0.4 mm.
Condition 2: The supply pressure X of the coating material 41 supplied to the groove 36 is in the range of 5 MPa to 15 MPa.

Condition 3: The total area SA of the openings 37 is in the range of 0.1 mm ^ 2 ("^" represents a power) to 0.6 mm ^ 2.
Y = 0.005X + 0.175 (Formula 1)
As shown in FIG. 5, the total sum SA depends on the length D4 of the opening 37 in the direction along the groove 36, the width W of the opening 37, and the number N of the openings 37. Therefore, by appropriately setting the length D4, the width W, and the number N, the total area SA of the openings 37 in the groove 36 can be brought close to 0.1 mm ^ 2 to 0.6 mm ^ 2. .

  The appropriate setting is that the length D4 of the opening 37 is set to 0.11 mm to 0.33 mm, the width W of the opening 37 is set to 0.15 mm to 0.25 mm, and the number N of the openings 37 is 2 to 4 is set.

  The width W of the opening 37 and the inner diameter D3 of the orifice 27 are set in consideration of the fact that clogging is less likely to occur when the coating material 41 including metal flakes flows through the groove 36.

  Further, the groove angle θ (see FIG. 3), which is the angle formed by the inner bottom surface of the groove 36 with respect to the end surface 33 of the core 30, is set to a value that satisfies the above condition 3 for the total area SA of the openings 37. The groove angle θ is preferably set to 20 ° to 56 °, for example.

  As shown in FIG. 1, a paint discharge path 45 is branched from the upstream side of the nozzle 23 of the paint supply path 19 in the airless gun 22. The discharge path 45 has a larger diameter than the inner diameter D3 of the orifice 27 in the nozzle 23. A switching valve 46 is provided at a branch portion of the discharge path 45 from the paint supply path 19 to switch the paint flow path downstream of the branch portion.

  The airless coating apparatus 10 of this embodiment is configured as described above. Next, as an operation of the present embodiment, a method (airless coating method) of performing metallic coating on the surface of the object CM using the airless coating apparatus 10 will be described.

  In the present embodiment, in order to perform metallic coating, as shown in FIG. 1, the color changing device 15 is connected to the coating tank 11a in which the coating material for metallic coating is stored among the coating material supply paths 16a, 16b, and 16c. The mode is switched to connect only the applied paint supply path 16 a to the paint supply path 19. Of the low-pressure pumps 18a, 18b, and 18c, only the low-pressure pump 18a connected to the paint supply path 16a is driven. Therefore, the paint stored in the paint tank 11a and containing the metal flakes is sent out at a low pressure to the downstream side of the paint supply path 16a by the low-pressure pump 18a.

  Here, if the color changing device 15 is disposed between the high pressure pump 20 and the airless gun 22, the paint that has become high pressure due to the pressure increase flows in the color changing device 15. A color change device 15 is required, and an increase in cost is inevitable. However, in the present embodiment, since the color changing device 15 is disposed between the low pressure pumps 18a, 18b, 18c and the high pressure pump 20 as described above, the low pressure paint flows through the color changing device 15. . Therefore, the low pressure type color changing device 15 is sufficient, and the cost increase is suppressed.

  The low-pressure paint that has passed through the color changing device 15 is increased in pressure by the high-pressure pump 20 to become high pressure, and is supplied to the airless gun 22 after being controlled by the regulator 21 to reach the target pressure.

  On the other hand, in the airless gun 22, the paint supply path 19 and the nozzle 23 communicate with each other and the communication between the paint supply path 19 and the discharge path 45 is blocked by the switching operation of the switching valve 46. The paint flowing through the paint supply path 19 is not discharged from the discharge path 45 but is supplied to the nozzle 23.

  Since the high-pressure pump 20 is disposed in the vicinity of the upstream side of the nozzle 23 in the coating material supply paths 16a, 16b, 16c, 19, the coating material is pressurized immediately before being supplied to the nozzle 23, and thus the high-pressure coating material is used. Is efficiently supplied to the nozzle 23. Here, when the high-pressure paint supplied to the airless gun 22 through the color changing device 15, the high-pressure pump 20, and the regulator 21 is a paint 41, as shown in FIG. 6, the paint 41 includes many thin pieces of metal. In this state, it flows through the flow path 40 in the nozzle 23.

  The coating material 41 including the flakes is supplied from the outer peripheral surface 34 of the main body 31 of the core 30 to each of the plurality of grooves 36. The paint 41 flows along the grooves 36 and is guided in a direction along the inner wall surface 26 a of the chamber 35 from an opening 37 provided on the end surface 33 on the downstream side of the core 30 (main body portion 31). Since the inner wall surface 26a has a tapered shape with a diameter decreasing toward the orifice 27 side, the coating material 41 and the metal flakes flow along the inner wall surface 26a, thereby turning in the chamber 35. The paint 41 and the flakes turn with a small radius as they approach the orifice 27. Therefore, the turning speed of the paint 41 and the flakes increases as it approaches the orifice 27.

  As indicated by arrows in FIG. 5, in the present embodiment, the paint 41 and the flakes are in a direction along the tangent line of the end surface 33 from a plurality of openings 37 provided at equal or substantially equal angles in the circumferential direction of the end surface 33. And is guided in a direction inclined with respect to the end face 33 with a groove angle θ. As shown in FIG. 6, the coating material 41 and the flakes guided from the openings 37 flow along the inner wall surface 26 a, whereby a strong swirling flow of the coating material 41 and the flakes is generated in the chamber 35.

  When the paint 41 and the flakes are sprayed from the orifice 27 to the outside of the housing 24, the paint 41 and the flakes move away from the orifice 27 while turning. This turning is performed so that the spray pattern (the cross-sectional shape when the sprayed paint diffuses) is enlarged as the distance from the orifice 27 increases. The paint 41 forms a film at a location close to the orifice 27. However, as the coating material 41 moves away from the orifice 27, the surface tension overcomes the force for maintaining the form of the film, and the coating material 41 is torn off. Even after the paint 41 is torn off, the paint 41 flies in the direction of spreading the spray pattern and is torn off again. In this way, the phenomenon that the spray pattern spreads in the direction of expanding the spray pattern while turning is repeated, so that the paint 41 is atomized into paint particles having a smaller particle diameter than the airless coating apparatus of the type using the fan spray nozzle 51. To go. The atomized paint particles have a particle size that can contain several pieces (for example, 5 or less) of metal flakes (a particle size that gives a particle size of 35 μm or less when attached to an object to be coated). . The average particle size for this paint corresponds to an average particle size of 20 μm or less for the flying water particles.

  Then, the paint particles including the above-mentioned several metal flakes and the paint particles including no metal flakes adhere to the object to be coated. As shown in FIG. 8, the attached paint particles 43 flow and extend along the surface of the object CM, so that each metal flake 42 in each paint particle 43 is substantially parallel to the surface of the object CM. It becomes a state. As shown in FIG. 9, the coating film 44 in a state in which a large number of metal thin pieces 42 are separated (dispersed) from each other is formed as a result of the large number of coating particles 43 adhering to the coating CM and fusing together. Formed on the surface.

  When light is incident on the coating film 44, it is substantially parallel to the surface of the object CM in a state where a large number of thin metal pieces 42 are dispersed, so that the light hits the thin metal piece 42 and is regularly reflected (incident angle). And the reflection angle is equal, the reflected light beam is a parallel light beam, and it is easy to reflect, and is rich in glitter.

  Further, as shown in FIG. 6, the paint 41 including the metal flakes flies while turning as described above even after being sprayed from the orifice 27. The radius of swirl of the paint 41 and the flakes increases as the distance from the orifice 27 increases. Therefore, in the process of atomization of the paint 41, the paint 41 located at the middle part of the spray pattern and the paint 41 located at the outer edge part can fly in the direction in which the spray pattern is widened (direction away from the central axis L1). It is. And the coating film 44 which has a thickness comparable as an intermediate part is formed also in the outer edge part of a spray pattern because the coating material 41 adheres to the to-be-coated material CM. Therefore, unlike an airless coating apparatus (see FIG. 13) in which the paint 53 is sprayed from the orifice 52 of the fan spray nozzle 51, a thick portion called a tail is unlikely to be generated at the outer edge portion of the spray pattern.

  In the case where the paint supply path 16b connected to the paint tank 11b in which the paint for solid coating is stored is connected to the paint supply path 19 by the switching operation of the color changing device 15, and the low pressure pump 18b is driven. The paint is supplied to the airless gun 22 in the same manner as described above, and is sprayed from the orifice 27 of the nozzle 23. In this case, the paint particles having a smaller particle size due to atomization are attached to the article CM. A coating film with high appearance quality is formed on the surface of the article CM by coating the paint particles together.

  At the time of switching the paint by the color changing device 15, the paint supply path 19 and the discharge path 45 are communicated by the switching operation of the switching valve 46, and the communication between the paint supply path 19 and the nozzle 23 is blocked. The paint is not supplied to the nozzle 23 and is discharged from the discharge path 45.

  Here, since the diameter of the discharge path 45 is set to be larger than the inner diameter D3 of the orifice 27, the paint is discharged from the discharge path 45 more efficiently than in the case of being ejected from the nozzle 23. Therefore, when the color changing device 15 switches the paint, the paint before the color changing temporarily remains downstream of the color changing device 15 in the paint supplying route 19, but the paint supply route is changed by the switching operation of the switching valve 46. 19 and the discharge path 45 are communicated with each other, so that the remaining paint is discharged from the paint supply path 19 through the discharge path 45 in a short time.

According to the embodiment described in detail above, the following effects can be obtained.
(1) As the airless coating apparatus 10, a chamber 35 is provided on the upstream side of the orifice 27 of the flow path 40 in the nozzle 23. A groove 36 that guides the pressurized paint 41 in the direction along the inner wall surface 26a of the chamber 35 from the opening 37 is provided on the upstream side of the chamber 35 of the flow path 40 in the nozzle 23 (FIG. 6).

  Further, as an airless coating method, the pressurized paint 41 is caused to flow through the flow path 40 of the nozzle 23 and sprayed from the orifice 27 at the downstream end of the flow path 40. As the nozzle 23, a chamber 35 is provided on the upstream side of the orifice 27 of the flow path 40, and a groove 36 connected to the chamber 35 is provided on the upstream side of the chamber 35 at the opening 37 at its downstream end. Is used. Then, the pressurized paint 41 flowing through the flow path 40 is supplied to the groove 36, and the paint 41 is guided from the opening 37 at the downstream end of the groove 36 in the direction along the inner wall surface 26a of the chamber 35 (see FIG. 6).

  Therefore, the paint 41 can be swung in the chamber 35 and sprayed from the orifice 27, and the paint 41 is made into paint particles 43 having a smaller particle size than the type of airless coating apparatus using the fan spray nozzle 51. Can do. When the paint 41 is a paint for metallic coating including the metal flakes 42, the flakes 42 are dispersed and a coating film 44 rich in glitter can be formed on the surface of the object CM ( FIG. 9). In addition, it is possible to suppress the occurrence of a tail that causes a problem in the type of airless coating apparatus using the fan spray nozzle 51. Thus, the coating film 44 with high appearance quality can be formed on the surface of the article CM.

  (2) A part of the nozzle 23 is configured by a combination of the housing 24 and the core 30. The housing 24 is provided on the downstream side of the adherent portion 25, and is provided on the downstream side of the adherent portion 25. A tapered portion 26 that decreases in diameter as it moves away from the downstream side 25, and an orifice 27 that extends from the inner bottom of the tapered portion 26 to the downstream side and opens at the end surface 24 b of the housing 24 are formed. A chamber 35 is configured by a space surrounded by the end surface 33 of the core 30 (main body portion 31) attached to the adherend portion 25 and the inner wall surface 26 a of the tapered portion 26. A groove 36 that connects the outer peripheral surface 34 of the core 30 (main body portion 31) and the end surface 33 is provided in the core 30 (FIGS. 2 and 3).

  Therefore, the high-pressure paint 41 supplied to the outer peripheral surface 34 of the core 30 (main body portion 31) is tapered from the opening 37 provided in the end surface 33 of the core 30 (main body portion 31) by the groove 36. It can be guided in a direction along the inner wall surface 26a.

  (3) The end surface 33 on the downstream side of the core 30 (main body portion 31) is configured by a circular plane. The groove 36 extends from the outer peripheral surface 34 of the core 30 (main body portion 31) along the tangent line of the end surface 33, and the opening 37 is positioned on the outer peripheral portion of the end surface 33 (FIGS. 4 and 5).

Therefore, a strong swirl flow can be generated in the chamber 35 by causing the paint 41 to flow along the tapered inner wall surface 26 a of the housing 24.
(4) As the coating material 41, a coating material for metallic coating including a metal flake 42 is used. The paint 41 is atomized into paint particles 43 having a particle size that can include several pieces (for example, five or less) of metal flakes 42. When water is used instead of the paint 41, the water is atomized into water particles having an average particle diameter of 20 μm or less during flight.

  Therefore, the coating particles 44 containing the above-mentioned several pieces of metal flakes 42 and having an average particle diameter of 35 μm or less are adhered to the surface of the article CM to be coated (FIG. 8). Can be formed (FIG. 9).

  (5) The inner diameter of the orifice 27 so that the ratio Y of the diameter D1 at the most upstream part of the chamber 35 to the depth D2 of the chamber 35 is not less than the value obtained by Equation 1 and not more than 5.0. D3, the supply pressure of the paint 41, the total area SA of the openings 37 in the groove 36, the diameter D1 and the depth D2 of the chamber 35 are set (FIG. 7). With this setting, the paint 41 is atomized into paint particles 43 having an average particle diameter of 35 μm or less after adhering to the article CM.

Therefore, several pieces of metal flakes 42 having an average particle diameter of about 20 μm can be included in the paint particles 43 after atomization, and the effect (4) can be obtained.
(6) The airless coating apparatus 10 of the present embodiment is superior to the air spray coating apparatus in the following points, like the type of airless coating apparatus using the fan spray nozzle 51.

  In the air spray coating apparatus, the atomized paint particles are conveyed by the force of compressed air. Therefore, the speed of the paint particles is not easily lowered and is likely to be scattered. There are relatively many paint particles that do not adhere (coating) to the object to be coated, and the coating efficiency is low. The coating efficiency is the ratio between the amount of paint used for painting and the amount of paint actually attached (coated) to the object.

  On the other hand, in the airless coating apparatus 10 of the present embodiment, unlike the air spray coating apparatus, the force of compressed air does not act on the paint particles, so that the paint particles are quickly decelerated after atomization and are not easily scattered. As a result, few of the paint particles are wasted without adhering to the workpiece CM. The coating efficiency is high and the amount of paint used can be reduced.

In addition, the said embodiment can also be implemented as a modification which changed this as follows.
The number of grooves 36 may be changed to a number different from that in the above embodiment.

  FIG. 10 shows a modification in which the grooves 36 are provided at two locations of the core 30 (main body portion 31). FIG. 11 shows a modification in which the grooves 36 are provided at three locations of the core 30 (main body portion 31). Each groove 36 in FIGS. 10 and 11 extends from the outer peripheral surface 34 of the main body 31 in the tangential direction of the downstream end surface 33 when the core 30 is viewed from one side in the direction along the central axis L2. The downstream end of each groove 36 has an opening 37 at the outer peripheral portion of the end surface 33, that is, at the boundary portion with the annular contact surface 32 of the end surface 33.

  However, in FIG. 10, the pair of grooves 36 are located at locations that are point-symmetric with respect to the central axis L <b> 2 of the core 30. In FIG. 11, the three grooves 36 are provided every 120 ° or approximately every 120 ° around the central axis L <b> 2 of the core 30.

  10 and 11, the coating material 41 flowing through the groove 36 is guided to the chamber 35 from a plurality of openings 37 provided at equal or substantially equal angles on the end surface 33, and thereafter. As shown by arrows in FIGS. 10 and 11, the gas flows along the inner wall surface 26 a to generate a swirling flow.

  FIG. 12 shows a modification in which the groove 36 is formed at a plurality of locations of the core 30 (main body portion 31) in a form different from that of the above embodiment, FIG. 10 and FIG. The groove 36 in this case extends in a direction along the tangent line of the end face 33, more specifically, a direction inclined with respect to the tangential line when the core 30 is viewed from one side along the central axis L2. Each groove 36 is inclined with respect to the generatrix of the annular contact surface 32 having a tapered shape. Even when the shape of the groove 36 is changed in this way, it is possible to guide the paint from the opening 37 in a direction along the inner wall surface 26 a of the tapered portion 26, thereby generating a swirl flow of the paint in the chamber 35.

  The inner wall surface 26a of the chamber 35 may be formed in a shape different from the tapered shape that decreases in diameter as it approaches the orifice 27, for example, a cylindrical shape having a constant inner diameter in the direction along the central axis L1. However, the chamber 35 has a portion (corner portion) where the bottom surface and the inner wall surface 26a are orthogonal to each other, and dust or the like in the paint 41 may accumulate here. In response to this, the corners are formed in a curved shape, a tapered shape, or the like so that dust or the like is not easily collected.

  In this regard, when the inner wall surface 26a of the chamber 35 is formed in a tapered shape that decreases in diameter as it approaches the orifice 27 (the embodiment corresponds to this), the orthogonal corner portion does not occur as described above. For this reason, the phenomenon that dust or the like in the paint 41 accumulates hardly occurs.

Further, when the inner wall surface 26a is tapered, there is an advantage that the tapered inner wall surface 26a can be easily formed by drilling.
The core 30 may be attached to the adherend portion 25 of the housing 24 not only at the downstream end portion but also at a portion upstream from the end portion.

The nozzle 23 includes the housing 24 and the core 30 as essential constituent members, but may be configured by adding other members thereto.
The airless painting apparatus and the airless painting method can also be applied to a case where a specific type of paint is supplied from a single paint tank to the nozzle of the airless gun through a low pressure pump, a high pressure pump and a regulator.

An article different from the interior / exterior product of the vehicle may be the article CM to be coated by the airless painting apparatus and the airless painting method.
・ The above-mentioned airless painting equipment and airless painting method can be applied to paint that uses a highly viscous fluid as a paint, atomizes it and adheres to the object to be coated, for example, a release agent sprayed onto a mold. is there.

  DESCRIPTION OF SYMBOLS 10 ... Airless coating apparatus, 23 ... Nozzle, 24 ... Housing, 24a, 24b, 33 ... End surface, 25 ... Adhered part, 26 ... Tapered part, 26a ... Inner wall surface, 27 ... Orifice, 30 ... Core, 34 ... Outer peripheral surface 35 ... chamber, 36 ... groove, 37 ... opening, 40 ... flow path, 41 ... paint, 42 ... flake, 43 ... paint particle, CM ... substrate, D1 ... chamber diameter, D2 ... chamber depth, D3: the inner diameter of the orifice, D4: the length of the opening, SA: the total area of the openings, W: the width of the opening, X: the supply pressure of the paint, Y: the ratio of the diameter and depth of the chamber.

Claims (7)

An airless coating apparatus comprising a nozzle having a paint flow path and an orifice provided at a downstream end of the flow path, pressurizing the paint and spraying from the orifice,
A chamber is provided in the nozzle on the upstream side of the orifice of the flow path,
In the nozzle, pressurized paint is supplied to the upstream side of the chamber of the flow path, and is connected to the chamber at an opening at the downstream end of the nozzle, and the paint is applied to the inner wall surface of the chamber from the opening. An airless coating apparatus, characterized in that a groove is provided for guiding in a direction along the direction. At least a part of the nozzle is configured by a combination of a housing and a core,
The housing is provided at an upstream end face of the housing and to which at least the downstream end of the core is attached, and a downstream side of the attached part. A tapered portion that is reduced in diameter as it moves away from the downstream portion, and an orifice that extends from the inner bottom portion of the tapered portion to the downstream side and opens at the downstream end surface of the housing,
The chamber is constituted by a space surrounded by an end face on the downstream side of the core attached to the adherent part and an inner wall surface of the tapered part,
2. The airless coating apparatus according to claim 1, wherein the groove is provided at a location connecting the outer peripheral surface of the core and the end surface on the downstream side in the core. The downstream end surface of the core is configured by a circular plane,
The airless coating apparatus according to claim 2, wherein the groove extends in a direction along a tangent line of the end surface from an outer peripheral surface of the core, and has the opening in an outer peripheral portion of the end surface. The paint supplied to the nozzle includes metal flakes,
The paint particles sprayed from the orifice of the nozzle and atomized have a size such that the average particle diameter becomes 35 μm or less after adhering to the object to be coated. Airless painting equipment. 5. When water is sprayed from the orifice of the nozzle in place of the paint and atomized, the water particles have a mean particle size of 20 μm or less during flight. The airless painting device described in 1. The inner diameter of the orifice is in the range of 0.1 mm to 0.4 mm, the supply pressure of the paint supplied to the groove is in the range of 5 MPa to 15 MPa, and the total area of the openings in the groove is 0.1 mm. If it is in the range of ^ 2 ("^" represents a power) to 0.6mm ^ 2,
When the supply pressure of the paint supplied to the groove is X and the ratio of the diameter at the most upstream part of the chamber to the depth of the chamber is Y, the ratio Y is equal to or greater than the value obtained by the following equation: And the inner diameter of the orifice, the supply pressure of the paint, the sum of the areas of the openings, the diameter at the most upstream part of the chamber, and the depth of the chamber are set to be 5.0 or less. The airless coating apparatus according to claim 4 or 5.
Formula: Y = 0.005X + 0.175 An airless coating method in which pressurized paint is supplied to a nozzle flow path and sprayed from an orifice at a downstream end of the flow path,
As the nozzle, a chamber is provided on the upstream side of the orifice of the flow path, and an upstream side of the chamber is provided with a groove connected to the chamber at the opening of its downstream end,
An airless coating method, wherein the paint that is pressurized and flows through the groove of the flow path is guided from the opening in a direction along the inner wall surface of the chamber.