JP2007203194A - Coating method of frame in construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid problems such that air pollution, sanitary environment, concern of ignition and treatment of waste water generated by the use of a solvent coating when a frame such as a rotation frame constitution an upper rotation body of a hydraulic shovel is coated, and further to apply coating of a high quality without being peeled off for a long period of time even when the frame is a black steel plate. <P>SOLUTION: The rotation frame 1 is coated with a powder coating using a polymer resin based powder coating and is coated with an adhesion treating agent as a pre-treatment of the powder coating after production of a chemical film in order to enhance adhesion property of the chemical film and the coating film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of a method of painting a frame in a construction machine such as a hydraulic excavator.

Some frames constituting construction machines such as hydraulic excavators are formed by integrally fixing a plurality of steel plates having different thicknesses, such as a revolving frame, by welding or the like. In general, coating is applied to improve durability and appearance.
Conventionally, a solvent paint in which a coating film forming component such as a pigment is dissolved in a solvent is used as a paint for coating the frame. However, the solvent coating using such a solvent paint eventually volatilizes the solvent, so that air pollution due to the volatile solvent becomes a problem. Further, when an organic solvent is used as a solvent, there is a problem of a worker's sanitary environment and there is a risk of ignition, and when water is used as a solvent, there is a problem of wastewater treatment. Furthermore, since it is virtually impossible to recover the oversprayed solvent paint, there is a problem that the paint loss is large.
Therefore, in order to cope with the problem in the case of using the solvent paint, a technique has been proposed in which a thermal spray coating of an aluminum-containing zinc alloy is applied to a large part constituting a hydraulic excavator (see, for example, Patent Document 1). .).
JP 2002-88806 A

  However, since the sprayed coating of the aluminum-containing zinc alloy is porous, corrosion resistance is likely to deteriorate due to water immersion. Therefore, in Patent Document 1, after the thermal spraying of the aluminum-containing zinc alloy, the sealing treatment is performed with a highly permeable coating. However, when a solvent coating is used as the coating for the sealing treatment, This problem still arises and there is a problem to be solved by the present invention.

The present invention has been created in view of the above-described circumstances in order to solve these problems, and the invention of claim 1 is formed by integrally fixing a plurality of black leather plates. In order to improve the adhesion between the chemical conversion film and the coating film after the formation of the chemical conversion film, as a pretreatment of the powder coating, the frame is applied by powder coating using a polymer resin powder coating. A method of painting a frame in a construction machine, characterized by applying an adhesion treatment chemical.
In this way, as in the case of using solvent paints, there is no problem of air pollution due to solvents, sanitary environment problems, fear of ignition, wastewater treatment, etc. It can be carried out. Furthermore, since the powder paint can be recovered and reused, paint loss can be almost eliminated. In addition, polymer resin powder coatings can form high-quality coatings with excellent corrosion resistance and weather resistance, so it is possible to apply coatings suitable for construction machines that often operate under severe conditions. it can. Furthermore, as a pretreatment for powder coating, the adhesion between the chemical conversion film and the coating film can be improved by applying an adhesion treatment agent after the formation of the chemical conversion film. It is possible to apply a high-quality coating that does not peel off.
The invention according to claim 2 is the method for coating a frame in the construction machine according to claim 1, wherein the chemical conversion treatment agent for generating the chemical conversion film is an iron phosphate solution.
And by doing in this way, wastewater containing zinc is not generated like zinc phosphate which is widely used as a chemical conversion treatment chemical, and it is excellent in environmental conservation and does not require large-scale wastewater treatment equipment. Thus, it is possible to reduce the cost and space of the wastewater treatment facility.
According to a third aspect of the present invention, there is provided the frame painting method for the construction machine according to the first or second aspect, wherein the frame is a revolving frame that constitutes a frame of the upper revolving structure of the excavator.
By doing so, it is possible to apply a high-quality coating that can contribute to environmental conservation on the revolving frame that constitutes the base of the upper revolving structure of the excavator.

Next, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a revolving frame that constitutes a frame for an upper revolving structure of a hydraulic excavator, which includes a side frame 1a that forms an outer shell, a turntable 1b to which a revolving bearing (not shown) is attached, and a work (not shown). The swivel frame includes left and right main frames 1c to which the machine is mounted and supported, a support frame 1d to which a counterweight (not shown) is supported, a cab (not shown) and a mounting frame 1e for mounting various member devices. 1 is formed by welding a plurality of black skin steel plates (steel plates with oxide scales attached) of different thicknesses integrally by welding, and in order to improve durability and appearance, a powder described later Painting is applied.
Of the components constituting the revolving frame 1, the turntable 1b, the left and right main frames 1c, and the support frame 1d are generally formed using thick steel plates (for example, 25 mm to 35 mm). The side frame 1a and the mounting frame 1f are formed using thin steel plates (for example, 5 mm to 10 mm).

  Regarding the equipment and procedure for the painting process of the swivel frame 1, first, the overall flow will be briefly described based on the whole painting equipment diagram shown in FIG. 2. The workpiece 1 carried in from the carry-in entrance A (the swivel frame in the painting process). 1 is referred to as a work 1. Hereinafter, the same) is guided by the traveling rail 3 in a state of being hung by a transfer device 2 to be described later, whereby a pretreatment process area B, an air blow process area C, a draining and drying area. D, the first cooling process area E, the main coating process area F, the baking and drying process area G, the second cooling process area H, and the stock area I are sequentially moved and carried out from the carry-out port J.

  As shown in FIG. 3, the transport device 2 uses a traveling rail 3, a cart 4 traveling on the traveling rail 3, a suspension device 5 provided on the cart 4, a traveling drive mechanism 6 that causes the cart 4 to travel. Configured. And it is comprised so that the workpiece | work 1 can be automatically conveyed by making the cart 4 drive | work in the state which suspended the workpiece | work 1 on the said suspension apparatus 5. FIG.

  The work 1 is first transported to the pretreatment process area B by the transport device 2, and the pretreatment process area B is, as shown in FIG. 4, a degreasing chemical tank 7, a first water washing tank 8, and a chemical conversion treatment. A chemical tank 9, a second rinsing tank 10, and a contact treatment chemical tank 11 are sequentially arranged along the work conveyance path, and as shown in FIG. 5, the liquid in each of the tanks 7, 8, 9, 10, and 11 is supplied to the work. 1 is equipped with a pump 12, a pipe 13, a nozzle 14 and the like for spraying.

  And in the said pre-processing process area B, the pre-processing before performing powder coating is performed, but as this pre-processing, degreasing of the workpiece | work 1, chemical conversion film production | generation, and adhesion treatment chemical | medical agent application are performed sequentially.

  In the degreasing step, the degreasing agent (alkaline or acid degreasing agent) stored in the degreasing agent tank 7 is sprayed onto the workpiece 1 to remove oil adhering to the workpiece 1. Thereafter, the water stored in the first washing tank 8 is sprayed and sprayed to wash the workpiece 1 with water.

In the chemical conversion film generation step, the chemical conversion chemical stored in the chemical conversion chemical tank 9 is sprayed onto the workpiece 1 to generate a chemical conversion film on the surface of the workpiece 1. Thereafter, the water stored in the second rinsing tank 10 is sprayed and sprayed to wash the workpiece 1 with water.
Here, iron phosphate is used as the chemical conversion treatment agent. The iron phosphate does not generate waste water containing zinc unlike zinc phosphate, which is widely used as a chemical conversion treatment chemical. Therefore, the iron phosphate is excellent in environmental conservation and does not require a large-scale waste water treatment facility. In addition, it is possible to reduce the cost and space of the wastewater treatment facility.

In the adhesion treatment chemical application step, the adhesion treatment chemical stored in the adhesion treatment chemical tank 11 is sprayed onto the workpiece 1 to apply the adhesion treatment chemical to the surface of the workpiece 1.
Here, in this Embodiment, the trivalent chromium solution (For example, 1-5% aqueous solution of chromium fluoride) is used as a contact | adherence treatment chemical | medical agent. And by apply | coating an adhesion | attachment processing chemical | medical agent in this way, between the chemical conversion film formed in the surface of the workpiece | work 1 in the process of chemical conversion film production | generation mentioned above, and the coating film formed in this coating process mentioned later Interlayer adhesion can be improved, and even a workpiece 1 formed from a black skin steel plate can be coated with high quality that does not peel off over a long period of time.
In addition, the chromium fluoride aqueous solution used in the present embodiment is excellent as an adhesion treatment agent for improving interlayer adhesion between the chemical conversion film and the coating film, but is not limited thereto. For example, a solution containing a trivalent chromium compound (or a metal compound such as titanium, iron, or copper) and an aminated phenol polymer is also known as an adhesion treatment agent, and such an adhesion treatment agent may be used. it can.

  Next, the workpiece 1 is conveyed to the air blow process area C, where draining by air blow is performed.

  Next, the work 1 is transported to a draining drying process area D. In the draining drying process area D, as shown in FIG. 6, a draining drying furnace provided with a burner 15, an air supply fan 16, an exhaust fan 17, and the like. 18 is installed. Then, the draining drying furnace 18 performs draining drying by an indirectly heated hot air circulation system.

  Next, the workpiece 1 is transported to the first cooling process area E. The first cooling process area E is equipped with a blower 19 and an exhaust fan 20 as shown in FIG. And here, cooling by the ventilation from the air blower 19 is performed.

  Next, the workpiece 1 is conveyed to the main coating process area F. The main coating process area F includes an automatic coating process area F1 in which automatic coating using the automatic coating machine 21 is performed, and manual coating correction by an operator. Is divided into a correction coating process area F2 in which is performed.

  As shown in FIG. 8, the automatic painting process area F1 is equipped with an automatic painting machine 21 including a paint tank 22, a friction charging gun 23, a branch nozzle 24, a paint collection hopper 25, a dust collector 26 and the like. Then, the automatic coating machine 21 applies electrostatic powder coating using a polymer resin powder coating to the workpiece 1. Further, in the correction coating process area F2, the operator performs hand coating correction with the polymer resin powder coating using an electrostatic hand gun (not shown).

Here, in the present embodiment, a polyester / urethane powder coating is used as the polymer resin-based powder coating. Then, by performing powder coating using such a polymer resin-based powder coating, the solvent coating is used for sealing treatment in the case of solvent coating using a solvent coating or after thermal spraying of an aluminum-containing zinc alloy. As in the case of using it, it is possible to perform coating excellent in environmental conservation without causing problems such as air pollution due to solvents, sanitary environment problems, fear of ignition, and wastewater treatment. Furthermore, since the oversprayed powder coating material can be recovered and reused by the coating material recovery hopper 25, the loss of the coating material can be almost eliminated.
The polyester / urethane powder coating used in the present embodiment is a polymer resin powder coating excellent in corrosion resistance and weather resistance, and is suitable as a coating used for the turning frame 1 of construction machinery. However, the present invention is not limited to this, and various polymer resin powder coating materials such as polyester powder coating material, epoxy powder coating material, epoxy / polyester powder coating material, and acrylic / polyester powder coating material can also be used.

  Next, the workpiece 1 is conveyed to the baking / drying process area G. In the baking / drying area G, as shown in FIGS. 9 and 10, a baking / drying furnace 31 including an infrared burner 27, a gas burner 28, an air supply fan 29, a circulation fan 30 and the like is installed. The burner 27 is disposed at the upper end of the work transfer side in the baking / drying furnace 31.

  The workpiece 1 carried into the baking / drying furnace 31 is first heated by the radiation of the infrared burner 27. The surface of the workpiece 1 is heated for a short time (for example, several minutes) by the radiation heating of the infrared burner 27. ) To raise the temperature at once. Thereafter, the surface temperature of the workpiece 1 is kept at a substantially constant appropriate temperature (for example, 150 degrees to 200 degrees) by indirect heating by a hot air circulation method using the gas burner 28, whereby the applied powder coating is baked and dried. Do. And by using together the radiant heating by the infrared burner 27 and the hot air circulation type heating by the gas burner 28 as described above, even the workpiece 1 formed from a plurality of steel plates having different thicknesses is insufficiently heated. Baking and drying in a uniform state can be performed without generating excessive heating, and a high-quality coating film can be formed.

  Next, the work 1 is conveyed to the second cooling process area H. In the second cooling process area H, as in the first cooling process area E, as shown in FIG. It is equipped with 20 mag. And here, the workpiece | work 1 heated up in the said baking drying process is cooled by the ventilation from the air blower 19, and the coating film of a polymer resin type powder coating material is completed.

  Next, the work 1 is transported to the stock area I. In the stock area I, as shown in FIG. 2, a stock conveyor 32 that stocks the transported work 1 and sequentially transports it to the discharge port J is arranged. Has been. And the workpiece | work 1 carried out from this carrying-out exit J is conveyed to the next process (for example, assembly process) of a coating process.

In the present embodiment configured as described, the revolving frame 1 serving as a base for the upper revolving body of the excavator is formed by integrally fixing black leather plates having different thicknesses by welding. The swivel frame 1 is coated by powder coating using a polymer resin powder coating.
As a result, in the case of solvent coating using solvent paint, or when solvent paint is used for sealing after thermal spraying of an aluminum-containing zinc alloy, there is a risk of air pollution, sanitary environment problems, and flammability. In addition, it is possible to perform coating excellent in environmental conservation without causing problems such as wastewater treatment. Furthermore, since the powder coating material can be recovered and reused, the coating material loss can be almost eliminated, which is advantageous in terms of cost. In addition, high-polymer resin-based powder coatings can form high-quality coatings with excellent corrosion resistance and weather resistance, so it is possible to apply coatings suitable for construction machines that often operate under severe conditions. it can.

  Further, as a pretreatment of the powder coating, degreasing, chemical conversion film generation, and adhesion treatment chemical application are performed. In this case, iron phosphate is used as the chemical conversion chemical for forming the chemical conversion film. This eliminates the generation of wastewater containing zinc unlike zinc phosphate, which is widely used as a chemical conversion treatment chemical, and is excellent in environmental conservation and eliminates the need for a large-scale wastewater treatment facility. Processing equipment costs and space can be reduced. Furthermore, by applying an adhesion treatment chemical after the formation of the chemical conversion film, the interlayer adhesion between the chemical conversion film and the coating film can be improved. However, it is possible to apply a high-quality coating that does not peel off over a long period of time.

  Of course, the present invention is not limited to the above embodiment, and the frame of the construction machine to be coated by powder coating using a polymer resin powder coating is limited to the revolving frame 1. For example, the present invention can be applied to various frames such as a truck frame that forms a traveling body of a construction machine, a frame that forms a driver's cab, and a frame that forms a vehicle body.

It is a perspective view of a turning frame. FIG. It is a figure which shows a conveying apparatus. It is a figure which shows the whole pre-processing process area. It is a figure which shows a pre-processing process area. It is a figure which shows the drainage drying process area. It is a figure which shows a 1st, 2nd cooling process area. It is a figure which shows an automatic painting process area. It is a figure which shows the whole bake drying process area. It is a figure which shows the baking drying process area.

Explanation of symbols

1 Turning frame (work)
B Pretreatment process area F Main coating process area

Claims (3)

  A frame formed by integrally fixing a plurality of black skin steel plates is coated by powder coating using a polymer resin powder coating, and as a pretreatment of the powder coating, A coating method for a frame in a construction machine, wherein an adhesion treatment chemical is applied to improve adhesion between the chemical conversion film and the coating film.   The method for coating a frame in a construction machine according to claim 1, wherein the chemical conversion treatment agent for generating the chemical conversion film is an iron phosphate solution.   The method of painting a frame in a construction machine according to claim 1 or 2, wherein the frame is a revolving frame that constitutes a frame for an upper revolving unit of a hydraulic excavator.

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