JP5730916B2 - Electrostatic coating equipment - Google Patents

Description

  The present invention relates to an electrostatic coating facility for performing electrostatic coating on a resin molded product such as a resin bumper.

In the electrostatic coating method, one of the paint fine particles and the work is kept positive, the other is kept negative, and the paint fine particles are sprayed onto the work. The paint can be efficiently attached to the workpiece by the electrical coupling action.
Since the resin molded product is basically an insulator, it is necessary to add conductivity in carrying out electrostatic coating.

  One method for adding conductivity is a method in which a conductive filler such as carbon black is mixed into the resin molded product itself (see, for example, Patent Document 1 (paragraph number [0051])).

  The conductivity is required on the surface, but in the technique of Patent Document 1, the conductive filler is mixed into the inside other than the surface, and the required amount of the conductive filler increases, which is uneconomical in terms of cost. Carbon black is literally black and has a dark surface. As a result, there are some problems such as affecting the paint color.

  Then, the method of providing electroconductivity, without using an electroconductive filler has been proposed (for example, refer patent document 2 (FIG. 1, FIG. 3)).

Patent document 2 is demonstrated based on the following figure.
FIG. 12 is a diagram for explaining the basic principle of the conventional technique. As shown in FIG. 12A, a pedestal 102 is placed on a carriage 101, and a resin bumper 103 is placed on the pedestal 102. Then, an earth clip 104 attached to the gantry 102 is attached to the resin bumper 103.

As shown in FIG. 12B, which is a cross-sectional view taken along the line bb in FIG. 12A, the resin bumper 103 is preliminarily provided with a conductive coating film 105. By attaching the earth clip 104 to the conductive coating film 105, the conductive performance necessary for electrostatic coating is ensured.
However, in addition to the resin molding process, a coating process for imparting conductivity is required, so that the number of processes and the manufacturing cost increase.

  While reductions in manufacturing costs and equipment costs are required, there is a need for electrostatic coating technology that can be implemented without using conductive fillers and conductive coatings, and electrostatic coating technology that can prevent the occurrence of coating defects. It is done.

JP 2002-45734 A JP 2003-117441 A

  This invention makes it a subject to provide the electrostatic coating technique which can prevent generation | occurrence | production of a coating defect while it can implement without using a conductive filler and a conductive coating film.

The invention according to claim 1 is an electrostatic coating facility in which a non- conductive resin molded product is used as a workpiece to be coated, and a water-based paint is electrostatically coated on the workpiece.
Comprising a jig mounting placing the workpiece transfer, placing the workpiece before described jig with the work mounting stage, to the next ground confirmation stage and coating stages, the described jig before carrying the workpiece in sequence A workpiece transfer device,
An earth clip attached to the mounting table and detachably attached to the workpiece to ground the workpiece;
An earth confirmation device installed on the earth confirmation stage to confirm that the earth clip is attached in a predetermined state;
Ri Do and a coating apparatus which is installed in the coating stage performing electrostatic painting to the workpiece,
The ground clip is attached in a range of 10 cm to 40 cm from the applied voltage mechanism,
The coating apparatus includes a coating gun for spraying the water-based paint, and a gun movement for directing the coating gun toward the earth clip at the start of painting and then moving along the workpiece so as to gradually move away from the earth clip. Means and
After applying the voltage with the applied voltage mechanism, measure the charged potential with the charge measuring mechanism a plurality of times within 1 to 5 seconds, and compare the measured charged potential with a predetermined reference potential with the earth determination unit characterized in that it was.

In the invention which concerns on Claim 1, the electrostatic confirmation installation is equipped with the earth confirmation apparatus which confirms that the earth clip is attached in the predetermined state.
If the ground confirmation device determines that there is an abnormality, electrostatic coating can be omitted. That is, electrostatic coating is performed on a workpiece that is properly grounded. As a result, the occurrence of poor coating can be prevented.

In addition, in the invention according to claim 1 , the ground confirmation device is arranged at a predetermined distance from the end face of the workpiece. In this state, the ground performance can be determined, and it can be determined whether or not the ground clip is securely attached to the workpiece.
Also, if an applied voltage mechanism or a charge measuring mechanism is brought into contact with the workpiece, contact marks or scratches may be generated on the workpiece surface, leading to quality degradation.
In this regard, in the present invention, since the applied voltage mechanism and the charge measuring mechanism are not brought into contact with the workpiece, there is no fear that contact marks or scratches are generated on the workpiece surface.

In addition, in the invention according to claim 1, toward the ground clip spray gun at the start painting, and then to cause as gradually away from the earth clip is moved along the workpiece. The paint before drying contains moisture, and this moisture exhibits conductivity.
Therefore, electrostatic coating can be carried out without using a conductive filler or a conductive coating film. As a result, it is not necessary to further enhance disaster prevention / explosion proof facilities, and equipment costs can be greatly reduced.

It is a principle figure of the experimental apparatus which investigates the reference electric potential provided to a ground confirmation apparatus. It is a graph which shows the correlation of the elapsed time from an application stop, and a charging potential. It is a layout figure of the electrostatic painting equipment concerning the present invention. It is a front view of a workpiece conveyance apparatus. It is a side view of a workpiece conveyance apparatus. It is sectional drawing of an earth confirmation stage. It is a 7-7 arrow line view of FIG. It is an effect | action figure in a workpiece | work mounting stage. It is an effect | action figure in an earth clip attachment stage. It is an effect | action figure in an earth confirmation stage. It is the block diagram of a coating device, and the operation | movement figure in a coating stage. It is a figure explaining the basic principle of the prior art.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.

  As shown in FIG. 1, an experimental apparatus 10 includes a polypropylene material 11 made of the same material as a resin bumper, a ground clip 12 that is detachably attached to the polypropylene material 11, a ground wire 13 extending from the ground clip 12, and a polypropylene material. 11 includes an applied voltage mechanism 56 and a charge measuring mechanism 59 disposed at a position facing the 11.

  As shown in the figure, the applied voltage mechanism 56 is disposed at a distance La perpendicularly from the surface of the polypropylene material 11. The charge measuring mechanism 59 is disposed at a position at a distance Lb perpendicularly from the surface of the polypropylene material 11 and is disposed at a position at a distance Lc from the applied voltage mechanism 56 along the longitudinal direction of the polypropylene material 11.

  The point where the axis of the applied voltage mechanism 56 (axis perpendicular to the surface of the polypropylene material 11) intersects the polypropylene material 11 is defined as the origin P0, and the first point separated from this P0 in the longitudinal direction of the polypropylene material 11 by P1, A second point a2 away from P1 in the longitudinal direction is P2, a third point a away from this P2 in the longitudinal direction is P3, a fourth point away from this P3 in the longitudinal direction is P4, and from this P4 in the longitudinal direction. The fifth point separated by a is called P5.

  In the experiment, a was 10 cm. The distance La was 20 cm, the distance Lb was 20 cm, and the distance Lc was 10 cm.

Then, −40 kV was applied by the applied voltage mechanism 56.
This application charges the polypropylene material 11 with static electricity. The charging potential due to this charging decreases as time passes after the application is stopped. Therefore, the charge measurement mechanism 59 is used to examine the correlation between time and the charged potential.

○ Without ground:
The charging potential was examined in a state where the earth clip 12 was not attached to the polypropylene material 11. The results are shown in Table 1.

  Immediately after the application was stopped, what was 27.4 kV became 15.4 kV after 1 second, and rapidly decreased to 9.5 kV after 5 seconds. The voltage was 8.3 kV after 10 seconds and 6.1 kV after 40 seconds.

○ With ground (Ground clip 12 is attached to point P1):
The earth clip 12 was attached to the point P1 of the polypropylene material 11, and the charging potential was examined in this state. The results are shown in Table 2.

○ With ground (Ground clip 12 is attached to point P2):
The earth clip 12 was attached to the point P2 of the polypropylene material 11, and the charging potential was examined in this state. The results are shown in Table 3.

○ With ground (Ground clip 12 is attached to point P3):
The earth clip 12 was attached to the point P3 of the polypropylene material 11, and the charging potential was examined in this state. The results are shown in Table 4.

○ With ground (Ground clip 12 is attached to point P4):
The earth clip 12 was attached to the point P4 of the polypropylene material 11, and the charging potential was examined in this state. The results are shown in Table 5.

○ With ground (Ground clip 12 is attached to point P5):
The earth clip 12 was attached to the point P5 of the polypropylene material 11, and the charging potential was examined in this state. The results are shown in Table 6.

  Although a large difference was observed in the charging potentials in Tables 6 and 5, the charging potentials in Tables 2 to 5 were almost the same. Therefore, Tables 2 to 5 (points P1 to P4 are grounded) all together, and together with the other Table 1 (no grounding) and Table 6 (points to P5 grounded), the correlation between elapsed time and charged potential is graphed. Decided to do.

  FIG. 2 is a semilogarithmic graph in which the horizontal axis is a logarithmic scale and the vertical axis is a normal scale. Then, when the application was stopped, the time was assumed to be 0.01 seconds after allowing for a time delay.

As shown in FIG. 2, the attenuation of the charging potential was gentle when there was no ground.
On the other hand, when grounding to the point P1 to the point P4, the static electricity escapes smoothly through the ground, so the attenuation of the charging potential became abrupt.
However, when grounded at the point P5, the attenuation of the charged potential was an intermediate value between when there was no ground and when grounded at the points P1 to P4.

  Excluding no ground and P5 ground, it is recommended that the ground clip 12 be mounted between the first point P1 to the fourth point P4, that is, in the range of 10 cm to 40 cm from the applied voltage mechanism 56.

Further, according to FIG. 2, the rate of change of the charging potential is large until the elapsed time is 1 second, and the rate of change of the charging potential is small from 1 second to 5 seconds, and the rate of change of the charging potential is minimal after 5 seconds. It is.
It is recommended to eliminate the erroneous measurement due to noise at the initial stage of measurement, and to evaluate the charging potential within 1 to 5 seconds, which has a large difference from the charging potential without ground in order to protect the cycle time in the workpiece production line .

In FIG. 2, for example, when attention is paid after 1 second, it is 6.3 kV when grounded to the point P1 to the point P4, and 15.4 kV when there is no ground, (15.4-6.3) According to the calculation of = 9.1, the potential difference is 9.1 kV.
Therefore, if the charged potential difference with no grounding is 8.1 kV or more in anticipation of an error, the ground clip is normally attached and “pass”, and the next process electrostatic coating is applied. If the voltage is 8.1 kV or less, the ground clip is not properly attached or has been forgotten to be “failed” and the electrostatic coating of the next process is not performed.

Further, when attention is paid after 5 seconds, the voltage is 1.9 kV when grounded to the points P1 to P4, 9.5 kV when there is no ground, and the potential difference is 7.6 kV.
Therefore, if the difference in charging potential from the case of no grounding is 6.6 kV or more in consideration of an error, the attachment of the earth clip is normal and “pass”, and the next process electrostatic coating is performed.
If it is 6.6 kV or less, the ground clip is abnormally attached or forgotten to be attached, and it is “failed”, and electrostatic coating in the next process is not performed.
Of course, the reference charging potential difference is not limited to the above, and may be determined in consideration of various conditions such as the size, shape, and cycle time of the workpiece. Note that the charged potential in the absence of ground is measured in advance and stored in a ground determination unit described later.

  Although the experimental results are omitted, the tendency shown in FIG. 2 can be confirmed if the distance La shown in FIG. 1 is in the range of 10 to 40 cm. Moreover, if the distance Lb was in the range of 20 to 30 cm, the tendency shown in FIG. 2 could be confirmed. Therefore, the distances La and Lb are not limited to 20 cm in the experiment.

  In addition, the distance Lc is at least 10 cm in order to avoid interference between the applied voltage mechanism 56 and the charge measuring mechanism 59, and is 40 cm or less so as to be within the range of the first point P1 to the fourth point P4. Accordingly, the distance Lc is preferably in the range of 10 to 40 cm.

Based on the above knowledge, we decided to improve the electrostatic coating equipment. The structure of the improved electrostatic coating equipment will be described below.
As shown in FIG. 3, the electrostatic coating equipment 20 includes a workpiece placement stage 21, an earth clip attachment stage 22, an earth confirmation stage 23, and a painting stage 24 arranged in series in this order. The devices described below are arranged at -24. Since the earth clip mounting stage 22 can be included in the workpiece placement stage 21, it is indicated by an imaginary line. Hereinafter, the devices arranged on the stages 21 to 24 will be described in detail.

In the workpiece placement stage 21, a placement jig (reference numeral 25) described below is a main element, and in the earth clip attachment stage 22, the earth clip 12 is a main element.
As shown in FIG. 4, rails 27, 27 are laid on the floor 26 and provided with wheels 28, 28 that run on the rails 27, 27, the carriage 29 can be moved in the front and back direction of the drawing. A mounting jig 25 that supports the workpiece W is provided on the carriage 29. The number of workpieces W may be one, two (first and second workpieces W1 and W2) as described later, or three or more, and the number to be processed is arbitrary.

  The mounting jig 25 includes, for example, a support bar 31 that extends upward from the carriage 29, a horizontal bar 32 that is fixed to the upper end of the support bar 31 and extends in a direction perpendicular to the traveling direction (the horizontal direction in the drawing), U-bars 33 and 33 (the shape will be described in FIG. 5) that are fixed to one end and the other end of the horizontal bar 32 and extend upward, and a mounting bar 34 that is fixed on the U-bars 33 and 33 and extends in the direction of the front and back of the drawing. It consists of.

The ground wires 13 and 13 are extended from one end and the other end of the horizontal bar 32, and the ground clips 12 and 12 are connected to the tips of the ground wires 13 and 13, respectively. That is, the ground clip 12 is grounded to the floor 26 via the ground wire 13, the horizontal bar 32, the support bar 31, the carriage 29, the wheel 28 and the rail 27.
On the floor 26, two U-shaped rails 35, 35 are arranged facing each other so as to form a mouth shape, and a pair of rolling rollers 36, 36 are rotatably accommodated.

As shown in FIG. 5, a transfer conveyor 38 is laid in the floor 26. On the conveyer 38, drive protrusions 39 protruding upward are provided at a predetermined pitch.
An engagement trolley 41 is provided on the side of the carriage 29, and an engagement claw 42 that is lowered from the engagement trolley 41 engages with the drive protrusion 39, whereby the carriage 29 is horizontally conveyed.

  The engaging trolley 41 is provided with side rollers 43 and 43 that rotate horizontally, and the side rollers 43 and 43 come into contact with the U-shaped rail 35, whereby the rolling of the engaging trolley 41 (movement in the front and back direction in the drawing) is restricted. Is done.

Further, standing pieces 44, 44 extending obliquely upward are provided at the end portion of the mounting bar 34 that is horizontally passed to the upper end of the U-shaped U-bar 33.
When the first work (front bumper) W1 and the second work (rear bumper W2) are placed on the mounting bar 34, the standing pieces 44 and 44 prevent these deviations and drops.

The workpiece transfer device 30 of the present invention includes a transfer conveyor 38, a carriage 29, a placement jig 25, and the like.
In FIG. 3, the workpiece transfer device 30 plays a role of transferring the workpiece to the earth clip attachment stage 22, the earth confirmation stage 23, and the coating stage 24 after the workpiece is placed on the workpiece placement stage 21.

Next, the configuration of the ground confirmation device disposed on the ground confirmation stage 23 will be described.
As shown in FIG. 6, two sets of the ground confirmation devices 50 are arranged so as to sandwich the workpiece W.
As shown in FIG. 7, one ground confirmation device 50 includes support columns 51, 51 standing on a floor or the like, support bars 52, 53 horizontally provided to these support columns 51, 51, and one support bar 52. , An applied voltage mechanism 56 attached via a rodless cylinder 54 and a slider 55, a charge measuring mechanism 59, 59 attached to the other support bar 53 via vertical rails 57, 57 and sliders 58, 58, and FIG. The earth determination unit 60 shown in FIG.

With the above-described configuration, the applied voltage mechanism 56 faces the end surface of the rear bumper W2 placed on the placement bar 34 of the transport carriage 29 that has been transported from the previous process to the earth check stage 23 by the work transport device 30 and stopped at a fixed position. Then, the slider 55, to which the applied voltage mechanism 56 is attached, is moved by the rodless cylinder 54, and the applied voltage mechanism 56 is directly opposed to the end surface of the front bumper W1, so that the voltage can be applied.
That is, with the above configuration, the applied voltage mechanism 56 can be shared by a plurality of workpieces W1 and W2, and the cost can be reduced.

  As shown in FIG. 6, the earth determination unit 60 is connected to the applied voltage mechanism 56 and the charge measurement mechanism 59, acquires charge potential information, performs pass / fail determination, and uses the alarm device 61 to output the sound information and optical information. The content is displayed on the display 62 in the form of character information or graph information.

From the above-described experiment, in FIG. 6, the distance LLa between the end face 63 of the workpiece W and the applied voltage mechanism 56 is in the range of 10 to 40 cm, preferably 20 to 30 cm, and more preferably 25 cm.
The distance LLb between the end face 63 of the workpiece W and the charge measuring mechanism 59 is set in the range of 20 to 30 cm, preferably 25 cm.

  Further, the applied voltage mechanism 56 and the charge measuring mechanism 59 are arranged in a region having a radius LLc of 40 cm with the ground clip 12 as the center. The positions of the applied voltage mechanism 56 and the charge measuring mechanism 59 can be changed by the sliders 55 and 58 described in FIG. 7 so that the arrangement position can be adjusted.

Next, the operation of the electrostatic coating equipment having the above configuration will be described.
As shown in FIG. 8, the workpiece W is placed on the placement jig 25 on the workpiece placement stage (FIG. 3, reference numeral 21).
Next, as shown in FIG. 9, the earth clips 12, 12 are attached to the lower end of the work W in the earth clip attachment stage (FIG. 3, reference numeral 22).

Next, an example in which the workpiece W is the workpiece W1 and the workpiece W2 will be described with reference to FIG.
In FIG. 10, for example, a voltage of −40 kV is applied to the end face 63 of the workpiece W1 by the applied voltage mechanism 56 in the ground confirmation stage (FIG. 3, reference numeral 23). After the application is stopped, the charging potential at the workpiece W1 is measured by the charge measuring mechanism 59.
Next, the applied voltage mechanism 56 is moved in the drawing front / back direction by the rodless cylinder (FIG. 7, reference numeral 54) and faces the workpiece W2. A voltage is applied to the end face 63 of the workpiece W2 by the applied voltage mechanism 56. After the application is stopped, the charging potential at the workpiece W2 is measured by the charge measuring mechanism 59.

For example, if the difference in charging potential from the absence of ground is 8.1 kV or more after 1 second, the ground determination unit 60 is normally attached to the ground clip and “passed”, and performs the next process electrostatic coating.
If the voltage is 8.1 kV or less, the ground clip is not properly attached or has been forgotten to be “failed” and the electrostatic coating of the next process is not performed.

Or, after 5 seconds, if the charged potential difference is 6.6 kV or more, the attachment of the ground clip is normal and “pass”, and the next process electrostatic coating is applied.
If it is 6.6 kV or less, the ground clip is abnormally attached or forgotten to be attached, and it is “failed”, and electrostatic coating in the next process is not performed.

  It is optional to determine either after 1 second or 5 seconds, or to determine after both 1 second and 5 seconds. If it is determined to pass in a case where both pass after 1 second and after 5 seconds, the reliability of the pass determination is greatly increased. Moreover, since it is an illustration, the determination timing is also arbitrary.

  As shown in FIG. 11A, the coating device 65 arranged on the coating stage (FIG. 3, reference numeral 24) includes a coating gun 67 that sprays the coating 66, and a gun moving means 68 that moves the coating gun 67. Consists of. The gun moving means 68 is preferably a robot that can move the coating gun 67 three-dimensionally.

  At the start of painting, the gun moving means 68 directs the painting gun 67 toward the ground clip 12 as shown in FIG. Spraying is started in this state. The paint 66 and the earth clip 12 are electrically connected, and electrostatic coating is started.

After the start of painting, the painting gun 67 is moved by the gun moving means 68 as indicated by the arrow (1).
In FIG.11 (b), although the workpiece | work W is an insulator, the coating film 69 contains the water | moisture content before drying. Therefore, the coating film 69 achieves electrical continuity between the paint 66 and the earth clip 12. Therefore, electrostatic coating can be continued by moving the coating gun 67 by the gun moving means 68 so as to gradually move away from the ground clip 12 as indicated by the arrow (2).

  According to FIG. 11, electrostatic coating can be applied to a non-conductive workpiece without adding a conductive coating film and without mixing carbon black.

  The present invention is suitable for electrostatic coating of resin front bumpers and resin rear bumpers, but may be used for electrostatic coating of other resin molded products.

  The present invention is suitable for electrostatic coating of resin front bumpers and resin rear bumpers.

  DESCRIPTION OF SYMBOLS 12 ... Earth clip, 20 ... Electrostatic coating equipment, 21 ... Work placement stage, 22 ... Ground clip attachment stage, 23 ... Ground confirmation stage, 24 ... Painting stage, 25 ... Placement jig, 30 ... Work transfer device, DESCRIPTION OF SYMBOLS 50 ... Ground confirmation apparatus, 56 ... Applied voltage mechanism, 59 ... Charge measuring mechanism, 60 ... Ground determination part, 63 ... End surface of workpiece | work, 65 ... Coating apparatus, 67 ... Coating gun, 68 ... Gun moving means, 105 ... Conductivity Coating film, W ... work, W1 ... first work (front bumper), W2 ... second work (rear bumper).

Claims (1)

An electrostatic coating facility that uses a non- conductive resin molded product as a workpiece to be coated, and electrostatically coats the workpiece with water-based paint .
Comprising a jig mounting placing the workpiece transfer, placing the workpiece before described jig with the work mounting stage, to the next ground confirmation stage and coating stages, the described jig before carrying the workpiece in sequence A workpiece transfer device,
An earth clip attached to the mounting table and detachably attached to the workpiece to ground the workpiece;
An earth confirmation device installed on the earth confirmation stage to confirm that the earth clip is attached in a predetermined state;
Ri Do and a coating apparatus which is installed in the coating stage performing electrostatic painting to the workpiece,
The ground clip is attached in a range of 10 cm to 40 cm from the applied voltage mechanism,
The coating apparatus includes a coating gun for spraying the water-based paint, and a gun movement for directing the coating gun toward the earth clip at the start of painting and then moving along the workpiece so as to gradually move away from the earth clip. Means and
After applying the voltage with the applied voltage mechanism, measure the charged potential with the charge measuring mechanism a plurality of times within 1 to 5 seconds, and compare the measured charged potential with a predetermined reference potential with the earth determination unit Electrostatic coating equipment characterized by that.

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