JP2023037197A - Electrodeposition coating device and electrodeposition coating method - Google Patents

Abstract

To control a film thickness of a paint in electrodeposition coating properly.SOLUTION: An electrodeposition coating device for electrodepositing a paint to a coated object comprises: an electrodeposition tank that is filled with an electrodeposition liquid dissolved with the paint and in which the coated object is immersed; an electrode that is arranged in the electrodeposition tank; a voltage application device that applies a voltage between the electrode and the coated object; a current measurement device that measures a current flowing between the electrode and the coated object; an electrical quantity calculation device that time-integrates current values having flowed to the coated object to calculate an electrical quantity having flowed to the coated object during an energization time; and a controller that controls the voltage application device so as to apply a first voltage between the electrode and the coated object in electrodeposition coating to the coated object in the electrodeposition tank, and controls a voltage to be applied between the electrode and the coated object to turn it into a second voltage between zero and the first voltage for a remaining energization time when an electrical quantity having flowed to the coated object during a predetermined energization time reaches an electrical quantity reference value by which a film thickness of the paint on the coated object is determined to have reached a reference film thickness.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an electrodeposition coating apparatus and an electrodeposition coating method.

BACKGROUND ART For example, cationic electrodeposition coating is performed when coating automobile parts such as suspension arms. At this time, it is desired to control the coating film thickness to an appropriate value, but the coating film thickness is affected by the concentration and temperature of the electrodeposition liquid, the energization time, the set voltage, the state of the equipment, and the like. Among these, the concentration of the electrodeposition liquid becomes thinner as the coating is formed by energization. Therefore, there is a problem that it is difficult to control the coating film thickness. Patent Literature 1 discloses an electrodeposition coating apparatus that controls the voltage applied to an electrode or a group of electrodes based on the amount of coulombs that flowed to an object to be coated when the object to be coated is conveyed in an electrodeposition liquid. It is

JP 2006-097119 A

After electrodeposition coating, for example, drying and baking of the paint are performed in the next step. In general, the object to be coated is immersed in the electrodeposition bath until just before drying and baking the paint. However, after the amount of coulombs that flowed into the object to be coated reached the reference value corresponding to the film thickness, the application of the voltage was stopped to prevent the film from becoming thicker and the voltage was reduced to 0 V. There is a problem that the film becomes thin due to melting during contact with the liquid.

The present disclosure can be implemented as the following forms.

(1) According to one aspect of the present disclosure, there is provided an electrodeposition coating apparatus that electrodeposits a coating material on an object to be coated. This electrodeposition coating apparatus includes an electrodeposition tank filled with an electrodeposition liquid in which the paint is dissolved and in which the object to be coated is immersed, electrodes arranged in the electrodeposition tank, the electrodes and the object to be coated. a voltage application device that applies a voltage between the electrode and the object to be coated; a current measuring device that measures the current flowing between the electrode and the object; an electricity quantity calculating device for calculating the quantity of electricity that has flowed to the object to be coated during time; Control is performed to apply a first voltage across the object to be coated, and the amount of electricity flowing to the object to be coated during a predetermined energization time determines the film thickness of the paint on the object to be coated as a reference film thickness. is reached, the voltage applied between the electrode and the object to be coated is changed from zero to the first a controller for controlling to a second voltage between the one voltage. According to this electrodeposition coating apparatus, the electrodeposition is performed with the applied voltage as the first voltage, and thereafter, when the film thickness of the object to be coated reaches the standard value of the quantity of electricity for determining that the film thickness has reached the standard film thickness, Since the applied voltage is the second voltage, it is possible to suppress the thickness of the coating material on the object to be coated from increasing. In addition, since the applied voltage is not zero, it is less likely that the paint on the object to be coated will dissolve and the film thickness will be reduced.
(2) In the electrodeposition coating apparatus of the above aspect, the current measuring device may be provided between the object to be coated and the voltage applying device. According to this form, the current flowing through the object to be coated can be accurately measured.
(3) In the electrodeposition coating apparatus of the above aspect, the voltage application device may apply a positive voltage to the electrode and a negative voltage to the object to be coated. According to this aspect, the electrodeposition coating apparatus can cationically electrodeposit the paint.
(4) In the electrodeposition coating apparatus of the above aspect, a plurality of electrodeposition tanks are provided as the electrodeposition tanks, the electrodes are respectively arranged in the plurality of electrodeposition tanks, and the voltage applying device includes a plurality of and the first voltage may be applied between the objects to be coated. According to this form, a plurality of objects to be coated can be continuously coated by the number of electrodeposition tanks.
(5) In the electrodeposition coating apparatus of the above aspect, the voltage application devices arranged in the plurality of electrodeposition tanks may apply the first voltages of different magnitudes.
(6) In the electrodeposition coating apparatus of the above aspect, the reference value of the quantity of electricity may be obtained from previously measured correlation data between the film thickness of the paint of the object to be coated and the quantity of electricity. According to this aspect, it is possible to correctly determine when the film thickness reaches the target.
(7) In the electrodeposition coating apparatus of the above aspect, the second voltage is determined by the speed at which the film thickness of the coating material increases due to electrodeposition, and It may be a voltage at which the rate of thickness reduction and the equilibrium state are achieved. According to this aspect, the film thickness of the object to be coated can be kept constant from the time the film thickness of the object to be coated reaches the target until the object is removed from the electrodeposition tank.
(8) In the electrodeposition coating apparatus of the above aspect, the second voltage may be determined by the concentration of the paint in the electrodeposition tank. According to this embodiment, the solubility of the electrodeposited paint in the electrodeposition solution varies depending on the concentration of the paint in the electrodeposition tank, so the second voltage should be appropriately determined based on the concentration of the paint in the electrodeposition tank. can be done.
(9) According to one aspect of the present disclosure, there is provided an electrodeposition coating method for electrodepositing paint on an object to be coated. This electrodeposition coating method comprises the steps of immersing the object to be coated in an electrodeposition bath filled with an electrodeposition solution in which the paint is dissolved and having electrodes arranged therein; applying a first voltage between the electrode and the object to be coated; measuring a current flowing between the electrode and the object to be coated; a step of calculating the amount of electricity during the energization time by temporally integrating the value of the current that flowed through; The voltage applied between the electrode and the object to be coated is set to zero for at least part of the remaining time of the energization time when the electric quantity reference value determined to have reached the reference film thickness is reached. and controlling to a second voltage between the first voltage. According to the electrodeposition coating method of this aspect, since the applied voltage is the second voltage, the film thickness of the paint on the object to be coated is less likely to increase, while the paint on the object to be coated dissolves and the film thickness increases. It is also possible to reduce the occurrence of thinning.
(10) The present disclosure can also be implemented in various forms other than the electrodeposition coating apparatus. For example, it can be realized in the form of an electrodeposition coating method or the like.

1 is an explanatory diagram showing a schematic configuration of an electrodeposition coating apparatus; FIG. 4 is a graph showing the relationship between the film thickness of a paint formed by electrodeposition and the amount of electricity flowing to an object to be coated. FIG. 2 is an explanatory diagram showing the relationship between applied voltage, current, and film thickness in electrodeposition processing. FIG. 4 is an explanatory diagram showing the relationship between the concentration of paint in the electrodeposition liquid and the film thickness; It is explanatory drawing which shows the component which is a to-be-coated object, and the relationship of a film thickness. FIG. 5 is an explanatory diagram showing a schematic configuration of an electrodeposition coating apparatus according to a second embodiment; FIG. 9 is an explanatory diagram showing the relationship between applied voltage, current and film thickness in the electrodeposition process in the second embodiment.

・First embodiment:
FIG. 1 is an explanatory diagram showing a schematic configuration of an electrodeposition coating apparatus 100. As shown in FIG. In FIG. 1, the x direction is the direction in which the object 90 to be coated is conveyed, the z direction is the vertical direction, and the y direction is the direction crossing the x and z directions. The electrodeposition coating apparatus 100 is an apparatus for electrodeposition-coating a paint onto an object 90 to be coated while moving the object 90 immersed in an electrodeposition tank 40 in the x direction. The electrodeposition coating apparatus 100 includes an electrodeposition tank 40 , an electrode 20 , a voltage application device 10 , a current measurement device 70 and a control device 60 . The electrodeposition tank 40 is filled with an electrodeposition liquid 50 in which paint to be coated on an object 90 is dissolved. Electrodes 20 are arranged on the bottom (−z direction) and side surfaces (±y directions) of the electrodeposition bath 40 . The electrodes 20 are connected to the voltage application device 10 . The number of electrodes 20 arranged on the bottom surface and the side surface is not limited to one, and a plurality of electrodes may be provided.

The object 90 to be coated is placed on the conductive electrodeposition pallet 26 , and the electrodeposition pallet 26 is placed on the conductive electrodeposition hanger 22 . The number of objects to be coated 90 placed on the electrodeposition pallet 26 may be one or a plurality of two or more. The electrodeposited hanger 22 is lifted by a lifting chain 30 . The electrodeposited hanger 22 is vertically moved by a motor 28 connected to an elevating chain 30 . In the first embodiment, there is one electrodeposition tank 40, and when the electrodeposition hanger 22 is lowered most, the object to be coated 90 is electrodeposited in the electrodeposition tank 40 together with the electrodeposition hanger 22 and the electrodeposition pallet 26. It is immersed in liquid 50 . When the electrodeposition hanger 22 is raised to the maximum, the object 90 to be coated is lifted above the electrodeposition solution 50 in the electrodeposition bath 40 together with the electrodeposition hanger 22 and the electrodeposition pallet 26 .

The electrodeposition hanger 22 is connected to a current collector 32 by a ground cable 24 . A current measuring device 70 is arranged between the ground cable 24 and the current collector 32 . The current collector 32 is in contact with an earth bar 34 , and the earth bar 34 is connected to the voltage application device 10 by an earth cable 36 .

In the first embodiment, the voltage applying device 10 is controlled by the control device 60 to apply a voltage so that the electrode 20 is positive and the object 90 to be coated is negative. The voltage application device 10 includes a rectifier board 12 , a rectifier 14 , and a distribution board 16 . The rectifier board 12 is controlled by the control device 60 and instructs the rectifier 14 about the applied voltage. The rectifier 14 is connected to the distribution board 16 and the ground cable 36 , generates a DC voltage indicated by the rectifier board 12 , and applies it between the distribution board 16 and the ground cable 36 . The distribution board 16 is connected to a plurality of power cables 18 , and each power cable 18 is connected to the electrodes 20 arranged on the bottom and side surfaces of the electrodeposition tank 40 . That is, the distribution board 16 distributes the current flowing through the electrodes 20 . The ground cable 36 is electrically connected to the object 90 to be coated via the ground bar 34 , the current collector 32 , the electrodeposition pallet 26 and the electrodeposition hanger 22 . As a result, the voltage application device 10 can apply a voltage so that the electrode 20 becomes positive and the earth bar 34 becomes negative.

When the voltage application device 10 applies a positive voltage to the electrode 20 and a negative voltage to the earth bar 34 , current flows from the electrode 20 to the earth bar 34 via the object 90 to be coated. At this time, the paint is electrodeposited on the surface of the object 90 to be coated. Hereinafter, the flow of current from the electrode 20 to the object 90 to be coated to the earth bar 34 is also referred to as "the flow of current from the electrode 20 to the object 90 to be coated".

Controller 60 includes PLC 62 and monitor 64 . The PLC 62 acquires the current flowing from the electrode 20 to the object 90 to be coated using the current measuring device 70, integrates it over time, and calculates the amount of electricity that flows from the electrode 20 to the object 90 to be coated. It works as a device. The PLC 62 calculates the film thickness of the electrodeposited paint on the object 90 from the amount of electricity flowing from the electrode 20 to the object 90 and instructs the voltage application device 10 to apply voltage. The monitor 64 graphs and displays the applied voltage, the current flowing from the electrode 20 to the object 90 to be coated, and the energization time. The control device 60 drives and controls the motor 28 to move the electrodeposition hanger 22 up and down.

FIG. 2 is a graph showing the relationship between the film thickness of the paint formed by electrodeposition and the amount of electricity flowing through the object 90 to be coated. In FIG. 2, the dashed line PA, the solid line PB, and the one-dot chain line PC respectively indicate the film thickness of the paint formed by electrodeposition and the It shows the relationship with the amount of electricity that has flowed. Part A, part B, and part C have different surface areas. Specifically, the surface area of the part A is the largest, and the surface area of the part B and the part C decreases in this order. As can be seen from this graph, there is a substantially direct proportional relationship between the film thickness of the paint formed by electrodeposition and the amount of electricity flowing through the object 90 to be coated, regardless of the part. Therefore, the control device 60 can know the film thickness of the paint electrodeposited on the object 90 to be coated from the amount of electricity supplied to the object 90 to be coated. Here, the amount of electricity when it is judged that the film thickness of the electrodeposited paint on the object 90 has reached the reference film thickness is defined as the reference value of the amount of electricity. do. In FIG. 2, 40 μm was used as the reference film thickness. At this time, the reference electric quantities QA, QB, and QC of the parts A, B, and C decrease in this order. The control device 60 causes the voltage applying device 10 to stop applying the voltage between the electrode 20 and the earth bar 34 when the amount of electricity flowing from the electrode 20 to the object 90 to be coated reaches the reference value of the amount of electricity. For example, the coating film thickness of the object 90 to be coated can be set to the reference film thickness. On the other hand, when the control device 60 causes the voltage application device 10 not to apply a voltage between the electrode 20 and the earth bar 34 and the object 90 to be coated is immersed in the electrodeposition tank 40, The film thickness of the paint on the object 90 to be painted becomes thin. It is considered that this is because the paint electrodeposited on the object 90 to be coated dissolves in the electrodeposition liquid 50 .

FIG. 3 is an explanatory diagram showing the relationship between applied voltage, current and film thickness in the electrodeposition process. In the first embodiment indicated by J1, the control device 60 uses the voltage applying device 10 to apply the first voltage V1 between the electrode 20 and the earth bar 34 from time t0 to time t3, which is a predetermined time. Apply voltage to perform electrodeposition coating. At time t3, the object 90 to be coated is moved to the end point of the electrodeposition bath 40, and the object 90 to be coated is pulled up from the electrodeposition bath 40. As shown in FIG. The predetermined time is the time from when the object to be coated 90 is started to be electrocoated until the object to be coated 90 is pulled up from the electrodeposition tank 40 . The predetermined time may be determined according to the magnitude of the voltage applied in the electrodeposition coating and the conveying speed of the object 90 to be coated. Here, at time t2 before time t3, the amount of electricity flowing from the electrode 20 to the object to be coated 90 reaches the reference value of the amount of electricity. The control device 60 applies the second voltage V2 between the electrode 20 and the earth bar 34 from time t2. In the example of FIG. 3, the first voltage V1 is between 250V and 300V, and the second voltage V2 is between 0V and the first voltage V1, for example 50V.

Reference example 1 indicated by R1 is an example in which the application of the first voltage V1 between the electrode 20 and the earth bar 34 is continued even after time t2. Reference example 2 indicated by R2 is an example in which the applied second voltage V2 is zero after time t2.

In the example of FIG. 3, the current value temporarily drops at time t1. This is for the following reasons. Depending on the shape of the object 90 to be coated, an air pocket may be formed on the surface of the object 90 to be coated. Since the electrodeposition liquid 50 does not come into contact with these air pockets, portions that are not electrodeposition coated are generated. In order to avoid this, at time t1, the control device 60 uses the motor 28 to once pull up the object 90 to be coated together with the electrodeposition hanger 22 from the electrodeposition tank 40, and then electrodeposit the object 90 together with the electrodeposition hanger 22 again. It is immersed in liquid 50 . When the object 90 to be coated and the electrodeposition hanger 22 are not immersed in the electrodeposition liquid 50, the current path from the electrodeposition solution 50 to the object 90 to be coated is cut off, so that no current flows. Therefore, the current value temporarily drops at time t1. Depending on the object 90 to be coated, such a process of once lifting the object 90 together with the electrodeposition hanger 22 from the electrodeposition bath 40 may not be necessary.

In the first embodiment, the amount of electricity flowing from the electrode 20 to the object 90 to be coated reaches the reference value of the amount of electricity at time t2. The amount of electricity can be calculated by integrating the current flowing from the electrode 20 to the object 90 to be coated from time t0 to the present. The film thickness of the object 90 to be coated monotonously increases from time t0 to time t2, and remains substantially unchanged from time t2 to time t3. In Reference Example 1, the film thickness of the object 90 to be coated monotonically increases from time t0 to time t3 after time t2. In Reference Example 2, the film thickness of the object 90 to be coated monotonically increases from time t0 to time t2, and decreases from time t2 to time t3. Therefore, after time t2, when the control device 60 causes the voltage applying device 10 to apply the second voltage V2 between the electrode 20 and the ground bar 34, which is between 0 V and the first voltage V1, The film thickness of the paint electrodeposited on the object to be painted 90 can be prevented from increasing or decreasing. The second voltage V2, for example, has a magnitude in the range of 10% to 30% of the first voltage V1.

FIG. 4 is an explanatory diagram showing the relationship between the concentration of paint in the electrodeposition liquid 50 and the film thickness when the same voltage is applied. HC, MC, and LC in the figure indicate the relationships at high, medium, and low concentrations, respectively. Also, R1 and R2 indicate Reference Examples 1 and 2, respectively, at medium density. As indicated by MC, when the concentration of the paint in the applied voltage electrodeposition liquid 50 is medium, the case is the same as the example shown in FIG. At time t2, the amount of electricity flowing through the object to be coated 90 reaches the reference value of the amount of electricity. After time t2, the control device 60 causes the voltage application device 10 to apply a second voltage V2 between 0 V and the first voltage V1 between the electrode 20 and the earth bar 34. FIG. As a result, after time t2, the coating film thickness of the object 90 to be coated does not increase or decrease, and remains substantially constant. In the case of medium concentration, the graph of current and film thickness is also shown in the case of Reference Example 1.

As indicated by HC, when the concentration of the paint in the electrodeposition solution 50 is higher than medium concentration, the current flowing is greater than that of medium concentration even with the same applied voltage. This is because the higher the concentration, the higher the ionic conductivity of the paint in the electrodeposition liquid 50 . Therefore, when the concentration is high, the amount of electricity flowing through the object to be coated 90 reaches the reference value of the amount of electricity at time t4, which is earlier than time t2. After time t4, the control device 60 causes the voltage application device 10 to apply the second voltage V2, which is between 0 V and the first voltage V1, between the electrode 20 and the earth bar . As a result, after time t4, the film thickness does not increase or decrease and becomes substantially constant.

As indicated by LC, when the concentration of the paint in the electrodeposition liquid 50 is lower than medium concentration, the ionic conductivity of the paint in the electrodeposition liquid 50 is low, so the current is small. Therefore, when the concentration is low, the amount of electricity flowing through the object to be coated 90 at time t5, which is later than time t2, reaches the reference value of the amount of electricity. After time t5, the control device 60 causes the voltage application device 10 to apply a second voltage V2 between 0 V and the first voltage V1 between the electrode 20 and the earth bar 34. FIG. As a result, after time t5, the film thickness does not increase or decrease, and becomes substantially constant.

As described above, regardless of the concentration of the paint in the electrodeposition liquid 50, the control device 60 controls the voltage application device 10 after the amount of electricity flowing through the object 90 reaches the reference value of the amount of electricity. By applying a second voltage V2 between 0 V and the first voltage V1 between the electrode 20 and the ground bar 34, the film thickness can be kept substantially constant with respect to the target film thickness. Variation in thickness can be reduced.

By controlling the film thickness of the coating, it is possible not only to suppress the occurrence of defective products, but also to improve the workability of the post-process. For example, by making the coating film thickness uniform, the number of thin portions is reduced, the corrosion resistance is uniform, and the failure rate in the market is reduced. A thick coating film is not formed on the screw part, etc., and workability such as screwing is improved.

Setting of the second voltage V2 will be described. Various settings are possible for the second voltage V2. Examples (1) to (3) are given below, but other methods may be used for setting.

(1) The second voltage V2 may be constant regardless of the concentration of paint in the electrodeposition liquid 50 . This makes it easy to set the second voltage V2.

(2) When the concentration of the paint in the electrodeposition liquid 50 is low, the coating film of the object 90 to be coated may be more easily dissolved in the electrodeposition liquid 50 than when the concentration is high. In this case, the control device 60 may set the second voltage V2 according to the concentration of the paint in the electrodeposition liquid 50 . Specifically, the control device 60 sets the second voltage V2 higher at low densities than at medium densities, and sets the second voltage V2 higher at high densities than at medium densities. can also be set lower.

(3) The controller 60 sets the second voltage V2 to an equilibrium state in which the speed at which the coating film thickness increases due to electrodeposition and the speed at which the coating film dissolves in the electrodeposition liquid 50 and decreases in thickness are equal. It is good also as a voltage which becomes. The relationship between the concentration of the paint in the electrodeposition liquid 50 and the rate at which the coating film dissolves in the electrodeposition liquid 50 and the film thickness decreases may be determined in advance by experiments and acquired as correlation data.

FIG. 5 is an explanatory diagram showing the relationship between parts A, B, and C, which are objects to be coated, and film thickness. The symbols of PA, PB, PC, R1 and R2 in the figure are the same as in FIGS. Regarding the surface area, the surface area of part A is the largest, followed by parts B and C, which decrease in this order. Part B is the same as the example shown in FIG.

In the component A, compared to the component B, the current is larger when the same first voltage V1 is applied. This is probably because the surface area of the component A is larger than that of the component B, so that the contact area with the electrodeposition liquid 50 is large and the contact resistance is small. In the part A, the amount of electricity flowing through the object to be coated 90 reaches the reference value of the amount of electricity at time t7, which is later than time t2. After time t7, the control device 60 causes the voltage application device 10 to apply a second voltage V2 between 0 V and the first voltage V1 between the electrode 20 and the earth bar 34. FIG. As a result, after time t7, the film thickness does not increase or decrease and becomes substantially constant.

In the component C, compared to the component B, the current is smaller when the same first voltage V1 is applied. This is probably because the surface area of the component C is smaller than that of the component B, so that the contact area with the electrodeposition liquid 50 is small and the contact resistance is large. In the part C, the amount of electricity flowing through the object to be coated 90 reaches the reference value of the amount of electricity at time t6, which is earlier than time t2. After time t6, the control device 60 causes the voltage application device 10 to apply a second voltage V2 between 0 V and the first voltage V1 between the electrode 20 and the earth bar 34. FIG. As a result, after time t6, the film thickness does not increase or decrease and becomes substantially constant.

Regardless of the size of the surface area of the object 90 to be coated, the control device 60 controls the voltage applying device 10 to apply voltage to the electrode 20 and the earth bar 34 after the amount of electricity flowing through the object 90 reaches the reference value for the amount of electricity. Between them, a second voltage V2 between 0 V and the first voltage V1 may be applied. Therefore, the control device 60 can carry out the electrodeposition coating by placing the objects 90 having approximately the same surface area on one electrodeposition pallet 26 . If the object 90 to be coated includes parts with different surface areas, the controller 60 may control the parts with an average surface area.

In the above embodiment, the control device 60 instructs the voltage application device 10 to apply the second voltage V2 from time t2 to time t3. The second voltage V2 may be applied at least partially, and then the object 90 to be coated may be pulled up from the electrodeposition tank 40 using the motor 28 when the application of the second voltage V2 is completed. It is preferable to immerse the object to be coated 90 in the electrodeposition tank 40 until immediately before the drying and baking of the paint in the next step, because the conditions from electrodeposition to drying and baking can be made uniform.

・Second embodiment:
FIG. 6 is an explanatory diagram showing a schematic configuration of the electrodeposition coating apparatus 101 of the second embodiment. In FIG. 6 as well, the x direction is the direction in which the object 90 to be coated is conveyed, the z direction is the vertical direction, and the y direction is the direction crossing the x and z directions. The electrodeposition coating apparatus 101 includes a control device 60 , an electrodeposition bath 40 and a transport unit 80 . The electrodeposition bath 40 has four electrodeposition baths 40a to 40d arranged in the x direction from a first electrodeposition bath 40a to a fourth electrodeposition bath 40d. The first electrodeposition bath 40a to the fourth electrodeposition bath 40d are arranged in four zones 41a, 41b, 41c and 41d from a first zone 41a on the inlet side to a fourth zone 41d on the outlet side, respectively. An electrode 20a is arranged in the first electrodeposition tank 40a, an electrode 20b in the second electrodeposition tank 40b, an electrode 20c in the third electrodeposition tank 40c, and an electrode 20d in the fourth electrodeposition tank 40d. Voltage applying devices 10a to 10d and earth bars 34a to 34d are provided corresponding to the electrodes 20a to 20d, respectively.

The conveying unit 80 is immersed in the electrodeposition liquid 50 in the first electrodeposition tank 40a, and thereafter, the conveyance unit 80 moves through the electrodeposition liquid 50 through the second electrodeposition tank 40b, the third electrodeposition tank 40b, and the third electrodeposition tank 40b by a motor (not shown). The tank 40c and the fourth electrodeposition tank 40d are moved in the x direction in this order. The transport unit 80 is pulled up from the fourth electrodeposition tank 40d. The transport unit 80 includes an electrodeposition hanger 22 , an earth cable 24 , an electrodeposition pallet 26 , an elevating chain 30 , a current collector 32 and a current measuring device 70 . When the transport unit 80 is placed in the first zone 41a, the current collector 32 of the transport unit 80 is placed in contact with the earth bar 34a. Further, when the transport unit 80 is arranged in the second zone 41b, the current collector 32 of the transport unit 80 is arranged so as to contact the earth bar 34b. The same applies when the transport unit 80 is arranged in the third zone 41c and the fourth zone 41d.

The object to be coated 90 transported by the conveying unit 80 is immersed in the electrodeposition liquid together with the electrodeposition hanger 22 and the electrodeposition pallet 26 in the first zone 41a. After that, the transport unit 80 moves from the first zone 41a to the fourth zone 41d via the second zone 41b and the third zone 41c, and is pulled up from the electrodeposition liquid 50 in the fourth zone 41d. In addition, in the second zone 41b, the object 90 is temporarily pulled up from the electrodeposition liquid 50 in order to suppress the occurrence of non-coated portions due to air pockets on the object 90 to be coated.

When the transport unit 80 exists in the first zone 41a, the control device 60 causes the voltage applying device 10a to apply a voltage between the electrode 20a and the earth bar 34a. Similarly, when the transport unit 80 is in the second zone 41b, the control device 60 causes the voltage applying device 10b to apply a voltage between the electrode 20b and the earth bar 34b so that the transport unit 80 is in the third zone 41b. 41c, the voltage application device 10c is caused to apply a voltage between the electrode 20c and the earth bar 34c. A voltage is applied between the electrode 20d and the earth bar 34d. The voltage applying devices 10a to 10d can apply different voltages.

When the transport unit 80 in the first zone 41a is moved to the second zone 41b, a new transport unit 80 is arranged in the first zone 41a. When the transport unit 80 in the second zone 41b is moved to the third zone 41c, the transport unit 80 in the first zone 41a can be moved to the second zone 41b. Thus, a maximum of one transport unit 80 can be arranged in each of the first zone 41a to the fourth zone 41d.

The electrodes 20a to 20d are arranged at certain intervals. By spacing the electrodes, when the voltage applying device 10a applies a voltage between the electrode 20a and the earth bar 34a, the electrodeposition liquid 50 from the electrode 20a and the earth bar 34b via the transport unit 80 34d to increase the electrical resistance of the path to reduce the current in this path.

FIG. 7 is an explanatory diagram showing the relationship between the applied voltage, the current and the film thickness in the electrodeposition process in the second embodiment. J2 indicates the second embodiment, and R3 and R4 indicate reference examples 3 and 4, respectively. The controller 60 of the second embodiment controls the voltage application device 10a from time t0 when the workpiece 90 of the transport unit 80 is submerged in the electrodeposition liquid 50 in the first zone 41a of the electrodeposition tank 40. On the other hand, a first voltage V1a is applied between the electrode 20a and the earth bar 34a to perform electrodeposition coating.

From time t11 to time t13, as described below, the transport unit 80 moves from the first zone 41a to the second zone 41b. That is, at time t11, the control device 60 causes the voltage application device 10b to apply the first voltage V1b between the electrode 20b and the earth bar 34b. However, at time t11, the current collector 32 of the transport unit 80 is not in contact with the earth bar 34b, so no current flows from the electrode 20b to the earth bar 34b. Also, the current flowing from the electrode 20b to the earth bar 34a via the transport unit 80 is extremely small due to the high electrical resistance as described above. The current flowing from the electrode 20b to the earth bar 34a via the transport unit 80 is the sum of the current flowing from the electrode 20a to the earth bar 34a via the transport unit 80, which can be measured using the current measuring device 70. . The amount of electricity obtained by integrating the total current is the current flowing through the object 90 to be coated, and the film thickness of the electrodeposited paint on the object 90 to be coated can be calculated.

At time t12, the current collector 32 of the transport unit 80 leaves the earth bar 34a and contacts the earth bar 34b. Therefore, after time t12, current flows from the electrode 20b to the earth bar 34b via the transport unit 80. FIG. Until time t13 when the control device stops voltage application to the voltage application device 10a, current flows from the electrode 20a to the earth bar 34b via the transport unit 80. However, as described above, since the electrical resistance is large, this current It is very small and can be measured using the current measuring device 70 .

As in the first embodiment, at time t1, the electrodeposition liquid 50 is pulled up from the transport unit 80 to change the position of the object 90 to be coated in the transport unit 80 supported by the electrodeposition hanger 22. Temporarily no current flows.

From time t14 to time t16, the transport unit 80 moves from the second zone 41b to the third zone 41c, similarly to the time from time t11 to time t13.

At time t2, the amount of electricity flowing from the electrodes 20a, 20b, and 20c to the object to be coated 90 reaches the reference value of the amount of electricity. The control device 60 applies the second voltage V2c between the electrode 20 and the earth bar 34 to the voltage application device 10c. The second voltage V2c is a voltage between the first voltage V1c and zero.

From time t1 to time t19, the transport unit 80 moves from the third zone 41c to the fourth zone 41d in the same manner as from time t11 to time t13. At this time, the applied voltage between the electrode 20c and the earth bar 34c is the second voltage V2c, and the applied voltage between the electrode 20d and the earth bar 34d is the second voltage V2d.

In Reference Example 3, as in Reference Example 1, the applied voltage between the electrode 20c and the ground bar 34c is the first voltage V1c, and the applied voltage between the electrode 20d and the ground bar 34d is the first voltage V1d after time t2. It is something to do. In Reference Example 3, after time t2, as in Reference Example 1, the film thickness of the object to be coated 90 monotonically increases from time t0 to time t3 after time t2.

In Reference Example 4, as in the second embodiment, after time t2, the voltage applied between the electrode 20c and the ground bar 34c is set to the second voltage V2c, and the voltage applied between the electrode 20d and the ground bar 34d is set to the second voltage V2d. However, the second voltages V2c and V2d are substantially zero. In Reference Example 4, after time t2, as in Reference Example 2, the film thickness of the object to be coated 90 monotonously increases from time t0 to time t2, and decreases from time t2 to time t3. .

As described above, also in the second embodiment, the amount of electricity flowing from the electrodes 20a, 20b, and 20c to the object 90 to be coated reaches the reference value of the amount of electricity. After time t2, the control device 60 applies voltages between 0 V and first voltages V1c and V1d to the voltage application devices 10c and 10d between the electrode 20c and the earth bar 34c and between the electrode 20d and the earth bar 34d. Since certain second voltages V2c and V2d are applied, the film thickness of the paint electrodeposited on the object to be coated 90 can be prevented from increasing or decreasing.

In the above description, it is assumed that the amount of electricity flowing from the electrodes 20a, 20b, and 20c to the object 90 to be coated reaches the reference value of the amount of electricity while the transport unit 80 is moving in the third zone 41c. However, depending on the surface area and number of the objects 90 to be coated, the amount of electricity flowing from the electrodes 20a and 20b to the objects 90 to be coated while moving in the second zone 41b may reach the reference value for the amount of electricity, or the fourth zone 41d may The amount of electricity flowing from the electrodes 20a, 20b, 20c, and 20d to the object 90 to be coated may reach the reference value of the amount of electricity. When the amount of electricity flowing through the object 90 to be coated while moving in the second zone 41b reaches the reference value for the amount of electricity, the control device 60 causes the voltage application devices 10b, 10c, and 10d to connect the electrode 20b and the earth bar 34b. Second voltages V2c, V2c, V2d between 0 V and first voltages V1b, V1c, V1d are applied between the electrode 20c and the ground bar 34c and between the electrode 20d and the ground bar 34d. Further, when the amount of electricity flowing through the object 90 to be coated while moving in the fourth zone 41d reaches the reference value for the amount of electricity, the control device 60 causes the voltage applying device 10d to set the voltage between the electrode 20d and the earth bar 34d. is applied with a second voltage V2d between 0 V and the first voltage V1d.

In the second embodiment, when the transport unit 80 moves from the first zone 41a to the second zone 41b, a new transport unit 80 can be placed in the first zone 41a. Therefore, electrodeposition of paint can be carried out on the object to be coated in parallel by the number of zones.

In addition, in the second embodiment, since the current amount is integrated for each transport unit 80, even if the types and numbers of the objects to be coated 90 placed on the transport units 80 of the zones 41a to 41d are different, good. Also, the control device 60 can apply different voltages to the voltage application devices 10a, 10b, 10c, and 10d. That is, the control device 60 can apply an appropriate voltage according to the type and number of the objects 90 to be coated placed on each transport unit 80 .

In each of the above embodiments, cationic electrodeposition is described as an example, in which the electrode 20 is positive and the object 90 to be coated is negative. can also be applied. Anion electrodeposition may be adopted when the object 90 to be coated is made of, for example, aluminum.

In each of the above embodiments, the current measuring device 70 is provided on the object 90 side, for example, the transport unit 80, but may be provided on the electrodes 20, 20a, 20b, 20c, and 20d side. When the electrode 20 is provided with a current measuring device 70 for each of the electrode 20 on the side surface and the electrode on the bottom surface of the electrodeposition tank 40, the detected values may be added up, and one current measurement may be performed on the main electrode 20. A device 70 may be provided. The same is true when the current measuring devices 70 are provided on the electrodes 20a, 20b, 20c, and 20d.

The present disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from the scope of the present disclosure. For example, the technical features of the embodiments corresponding to the technical features in each form described in the Summary of the Invention column are used to solve some or all of the above problems, or to achieve some of the above effects. Or in order to achieve all, it is possible to perform substitution and combination suitably. Also, if the technical features are not described as essential in this specification, they can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10, 10a, 10b, 10c, 10d... Voltage application apparatus, 12... Rectifier board, 14... Rectifier, 16... Distribution board, 18... Electric cable, 20, 20a, 20b, 20c, 20d... Electrode, 22... Electrodeposition Hanger 24 Earth cable 26 Electroplated pallet 28 Motor 30 Lifting chain 32 Current collector 34, 34a, 34b, 34c, 34d Earth bar 36 Earth cable 40, 40a, 40b, 40c, 40d...Electrodeposition tank 41a, 41b, 41c, 41d...Zone 50...Electrodeposition liquid 60...Control device 62...PLC (Electrical quantity calculator) 64...Monitor 70...Current measuring device 80 ... Conveying unit 90 ... Object to be coated 100, 101 ... Electrodeposition coating device

Claims (9)

An electrodeposition coating apparatus for electrodepositing paint on an object to be coated,
an electrodeposition tank filled with an electrodeposition liquid in which the paint is dissolved and in which the object to be coated is immersed;
an electrode placed in the electrodeposition tank;
a voltage applying device that applies a voltage between the electrode and the object to be coated;
a current measuring device that measures the current flowing between the electrode and the object to be coated;
an electricity quantity calculating device for calculating the quantity of electricity flowing to the object to be coated during the current application time by integrating the value of the current flowing through the object to be coated over time;
When electrodeposition coating is applied to the object to be coated in the electrodeposition tank, the voltage application device is controlled to apply a first voltage between the electrode and the object to be coated, and a predetermined voltage is applied between the electrode and the object to be coated. If the amount of electricity flowing to the object to be coated during the energization time reaches the reference value for the amount of electricity determined that the film thickness of the paint on the object to be coated has reached the reference film thickness, the energization time a control device for controlling the voltage applied between the electrode and the object to be a second voltage between zero and the first voltage during at least part of the remaining time of
An electrodeposition coating device. The electrodeposition coating apparatus according to claim 1,
The electrodeposition coating apparatus, wherein the current measuring device is provided between the object to be coated and the voltage applying device. The electrodeposition coating apparatus according to claim 1 or claim 2,
The electrodeposition coating apparatus, wherein the voltage application device applies a positive voltage to the electrode and applies a negative voltage to the object to be coated. The electrodeposition coating apparatus according to any one of claims 1 to 3,
Having a plurality of electrodeposition tanks as the electrodeposition tanks,
The electrodes are respectively arranged in a plurality of the electrodeposition tanks,
The voltage applying device is arranged corresponding to the electrodes of the plurality of electrodeposition tanks, and applies the first voltage between the objects to be coated. The electrodeposition coating apparatus according to claim 4,
The electrodeposition coating apparatus according to claim 1, wherein the voltage application devices respectively arranged in the plurality of electrodeposition tanks apply the first voltages of different magnitudes. The electrodeposition coating apparatus according to any one of claims 1 to 5,
The electrodeposition coating apparatus, wherein the reference value of the quantity of electricity is obtained from previously measured correlation data between the film thickness of the paint of the object to be coated and the quantity of electricity. The electrodeposition coating apparatus according to any one of claims 1 to 6,
The second voltage is a state in which the rate at which the film thickness of the coating material increases due to electrodeposition and the rate at which the electrodeposited coating material dissolves in the electrodeposition liquid and the film thickness decreases are in equilibrium. Electrodeposition coating equipment with a voltage that is The electrodeposition coating apparatus according to any one of claims 1 to 7,
The electrodeposition coating apparatus, wherein the second voltage is determined by the concentration of the coating material in the electrodeposition bath. An electrodeposition coating method for electrodepositing a paint on an object to be coated,
a step of immersing the object to be coated in an electrodeposition tank filled with an electrodeposition liquid in which the paint is dissolved and electrodes are arranged;
a step of applying a first voltage between the electrode and the object to be coated when electrodeposition coating is applied to the object to be coated in the electrodeposition tank;
measuring a current flowing between the electrode and the object to be coated;
a step of calculating the amount of electricity during the energization time by temporally integrating the value of the current flowing through the object to be coated;
When the amount of electricity flowing through the object to be coated during a predetermined energization time reaches an amount of electricity reference value for determining that the film thickness of the object to be coated has reached the reference film thickness, the energization time is terminated. controlling the voltage applied between the electrode and the object to be a second voltage between zero and the first voltage for at least part of the remaining time;
An electrodeposition coating method comprising:

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