Electrodeposition paint replenishment system and method

Abstract

To provide an electrodeposition paint supply system that makes it possible to stabilize the NV concentration of an electrodeposition coating solution. [Solution] The system includes an electrodeposition tank 31 containing an electrodeposition paint solution, a pump that operates in a timely manner to replenish the paint into the electrodeposition tank 31, an ammeter 36 that measures the current when the product W is electrodeposited in the electrodeposition tank 31, and a control unit 37 that operates a pump 47 based on the current value measured by the ammeter 36 to restore the NV concentration of the solution in the electrodeposition tank 31.

Description

[Technical Field]

[0001] The present invention relates to an electrodeposition paint replenishment system and method for use in electrodeposition coating of products. [Background technology]

[0002] A conventional electrodeposition coating apparatus is shown in Patent Document 1. In this electrodeposition coating apparatus, the workpiece is sent to a drying process after passing through a degreasing process, a water rinsing process, a chemical conversion coating formation process, a water rinsing process, an electrodeposition process, and a water rinsing process in this order, and the electrodeposition coating is cured in the drying process.

[0003] In such an apparatus, in the electrodeposition process, for example, there is a method of replenishing paint by operating a metering pump for a fixed period of time after each electrodeposition.

[0004] At this time, a fixed amount of paint is replenished regardless of the amount of NV (non-volatile), which is a solid or non-volatile component, consumed in one electrodeposition, so the NV concentration (concentration of solid or non-volatile components) in the electrodeposition tank may vary.

[0005] Such variations in NV concentration have led to the problem that the thickness of the electrodeposited film is unstable, and the film thickness of the finished product cannot be made constant. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-28579 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved is the variation in NV concentration of the electrodeposition coating solution. [Means for solving the problem]

[0008] The electrodeposition paint replenishment system of the present invention includes an electrodeposition tank containing an electrodeposition paint solution, a pump that operates in a timely manner to replenish the paint to the electrodeposition tank, an ammeter that measures the current when a product is electrodeposited in the electrodeposition tank, and a control unit that operates the pump based on the current value measured by the ammeter to restore the NV concentration of the solution in the electrodeposition tank.

[0009] The electrodeposition paint replenishment method of the present invention integrates the current when electrodeposition coating a product in the electrodeposition tank, and replenishes paint to the electrodeposition tank according to the integrated current value to restore the NV concentration of the solution in the electrodeposition tank. [Effects of the Invention]

[0010] According to the present invention, the NV concentration of the electrodeposition coating solution can be stabilized. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a conceptual diagram of an entire electrodeposition coating line according to an embodiment of the present invention. [Figure 2] FIG. 2 is a conceptual diagram of the electrodeposition process of the electrodeposition coating line of FIG. 1, which employs the electrodeposition paint replenishment system according to an embodiment of the present invention. [Figure 3] FIG. 3 is a flow chart showing the supply of paint by the PLC in the electrodeposition process of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] The electrodeposition paint replenishment system of one embodiment includes an electrodeposition tank 31, a pump 47, an ammeter 36, and a control unit 37. The electrodeposition tank 31 contains an electrodeposition paint solution (electrodeposition solution) 33. The pump 47 operates in a timely manner to replenish the electrodeposition tank 31 with paint. The ammeter 36 measures the current during electrodeposition coating of the product W in the electrodeposition tank 31. The control unit 37 operates the pump 47 based on the current value measured by the ammeter 36, thereby restoring the NV concentration of the electrodeposition solution 33 in the electrodeposition tank 31. NV refers to solids or non-volatile components dispersed in the electrodeposition solution 33.

[0013] The control unit 37 preferably controls the operation of the pump 47 so as to recover the NV concentration that has decreased due to the use of the electrodeposition solution 33 in accordance with the integrated value of the measured current value.

[0014] The operation of the pump 47 can be controlled either by detecting the amount of paint supplied to the electrodeposition tank 31 by operation of the pump 47 using the flow meter 36 and adjusting the amount of paint supplied to correspond to the current value, or by storing a time setting for the amount of paint supplied to correspond to the current value as a map in advance and controlling the pump 47 according to the current value.

[0015] A plurality of products W of different sizes are electrocoated in the electrocoating tank 31 one after another, and the control unit 37 may control the operation of the pump 47 according to the integrated value of the current value measured for each product W.

[0016] This method can also be applied when the size of the products W is uniform. The recovery of the NV concentration can be performed for each product W, for multiple products W, or at the end of each day's work.

[0017] The electrodeposition paint replenishment method of the present invention accumulates the current when electrodeposition coating the product W in the electrodeposition tank 31, replenishes the paint to the electrodeposition tank 31 according to the accumulated current value, and sets the NV concentration of the electrodeposition solution 33 in the electrodeposition tank 31. [Example]

[0018] FIG. 1 is a conceptual diagram of an entire electrodeposition coating line according to one embodiment of the present invention.

[0019] As shown in Figure 1, unpainted workpieces W (see Figure 2), which are products that have been pressed or otherwise processed, are transported to the electrocoating line by an overhead conveyor 1. Note that a general overhead conveyor 1 can be used, and is only conceptually indicated by arrows in the figure.

[0020] The workpieces W range from large and small truck frames to other small parts, and multiple types of products of different sizes and shapes are transported in sequence and electrocoated on the same line. In the figure, the workpieces W are also shown only conceptually.

[0021] This workpiece W goes through a preliminary degreasing process 3, a degreasing 1 process 5, and a degreasing 2 process 7 in order to remove press oil, iron powder from welding, and other dust. Next, the workpiece W goes through a water washing 1 process 9 and a water washing 2 process 11 to be washed.

[0022] After cleaning, the workpiece W is treated with a chemical conversion treatment solution in a chemical conversion treatment step 13, and then passes through a water washing 3 step 15, a water washing 4 step 17, and a pure water washing step 19 before reaching an electrodeposition step 21. In the electrodeposition step 21, electrodeposition coating is performed on the surface of the workpiece. The electrodeposition step 21 will be described in more detail below.

[0023] From the electrodeposition process 21, excess paint is recovered through UF water washing 1 process 23, UF water washing 2 process 25, and UF water washing 3 process 27.

[0024] Finally, a drying process is carried out in the drying step 29, and the electrodeposition coated product is discharged.

[0025] [Electrodeposition process] FIG. 2 is a conceptual diagram of the electrodeposition process of the electrodeposition coating line of FIG. 1, which employs the electrodeposition paint replenishment system according to an embodiment of the present invention.

[0026] As shown in Fig. 2, the electrodeposition process 21 includes an electrodeposition tank 31. An electrodeposition solution 33 having a paint dispersed therein is contained in the electrodeposition tank 31. The electrodeposition tank 31 includes an electrodeposition electrode 35, and the electrode 35 is connected to a PLC (control panel) 37 serving as a control unit via an ammeter 36.

[0027] The PLC 37 is a computer having a processor, memory, etc., and controls the electrodeposition onto the workpiece W and the supply of paint to the electrodeposition tank 31 by executing a program in the memory on the processor. This PLC 37 is electrically connected to a paint hanger 41 via a power supply 39. The ammeter 36 is also provided to measure the current converted from AC to DC. However, a dedicated ammeter can also be used.

[0028] A workpiece W is loaded on the paint hanger 41. The paint hanger 41 is transported on the electrodeposition coating line by the overhead conveyor 1, and the paint hanger 41 is lowered into the electrodeposition tank 31, where the workpiece W is immersed in the electrodeposition solution 33.

[0029] Paint is supplied to the electrodeposition tank 31 from a paint tank 43 via a pipe 45. A pump 47 and a flow meter 49 are installed in the pipe 45. The pump 47 and the flow meter 49 are electrically connected to the PLC 37.

[0030] The pump 47 is driven under the control of the PLC 37 and supplies paint from the paint tank 43 to the electrodeposition tank 31. The flow meter 49 measures the flow rate of the paint supplied from the paint tank 43 to the electrodeposition tank 31 by driving the pump 47, and inputs the measured flow rate to the PLC 37.

[0031] Therefore, in the electrodeposition process, the PLC 37 controls as described below to replenish the electrodeposition solution 33 in the electrodeposition tank 31 with paint for each electrodeposition coating of the workpiece W, thereby restoring the NV concentration of the electrodeposition solution 33 and performing the electrodeposition coating.

[0032] [Electrodeposition paint replenishment control] FIG. 3 is a flow chart showing the supply of paint by the PLC in the electrodeposition process of FIG.

[0033] In the PLC 37, a signal from the start switch or the like is used as a trigger to execute the program in the memory in the processor, and the flowchart in Figure 3 is started.

[0034] In step S1, the paint supply amount corresponding to the current value is read from the memory by the process of "reading the supply amount for the current value." The paint supply amount for the current value correlates with the amount of paint used during electrodeposition coating and the applied current value, so the paint supply amount is calculated from the current value based on this correlation.

[0035] For example, if the applied current value during electrodeposition coating is 20 KAh, the amount of paint replenished will be 1 L. The correlation between the amount of paint used and the applied current value can be calculated in advance and stored in memory. The applied current value is the cumulative current value during one electrodeposition coating.

[0036] The read paint supply amount can be corrected using a correction coefficient. Changes in the painting environment, such as temperature, cause changes in the thickness of the paint film due to electrodeposition, which in turn causes fluctuations in the amount of paint used. To accommodate this change in the amount of paint used, a correction coefficient based on the change in the painting environment is set in the PLC 37.

[0037] The correction coefficient can be set based on the correlation between the coating environment and the coating film thickness. Alternatively, the NV concentration of the coating material may be measured after a test run of electrodeposition coating is performed and the coating material is supplied to the electrodeposition tank 31, and the correction coefficient may be set based on the measured value.

[0038] The NV concentration is measured by drying a sample of the electrodeposition solution 33 obtained from the electrodeposition tank 31, measuring the weight before and after drying, and determining the NV concentration from the measurement results.

[0039] The correction coefficient is set so that, for example, when the current value applied during electrodeposition coating is 20 KAh, the paint supply amount changes from the set value of 1 L to a corrected value of 1.1 L. As a result, for example, when the allowable range of the NV ratio in the electrodeposition solution 33 is 20 to 23%, the NV ratio is set to approximately 21 to 22% rather than the upper or lower limit.

[0040] In step S2, the "electrodeposition coating" process is executed. That is, the overhead conveyor 1 is driven by the PLC 37, and the paint hanger 41 carrying the workpiece W is transported sequentially from the entrance of the line. In response to this transport, the paint hanger 41 repeatedly rises and falls, and the workpiece W is sequentially subjected to the preliminary degreasing process 3 to the drying process 29.

[0041] In the electrodeposition step 21 of the electrodeposition coating, a current is passed between the workpiece W and an electrode 35 in an electrodeposition tank 31 shown in FIG. 2, and the workpiece W is electrodeposited with an electrodeposition solution 33 .

[0042] In step S3, a "current value detection" process is executed. That is, when current is applied to the single workpiece W in step S2, the current value to the electrode 39 during electrodeposition coating of the single workpiece W is detected. The detected current values ​​are sequentially input to the PLC 37, which stores them in its internal memory. Note that step S3 is performed in parallel with step S2, but for convenience, it is shown in FIG. 3 as being immediately subsequent to step S2.

[0043] In step S4, the "current value accumulation" process is executed. That is, the PLC 37 accumulates the current values ​​stored sequentially until the end of energizing the single workpiece W in step S2. The accumulation method includes a method of storing the current values ​​detected in step S3 while adding them up, and a method of summing the sequentially stored current values. As a result, the total of the current values ​​applied to the electrodeposition coating of the single workpiece W during electrodeposition coating is obtained as the accumulated current value.

[0044] In step S5, the process of "calculating the amount of paint to be supplied" is executed. That is, the PLC 37 calculates the amount of paint to be supplied from the integrated current value obtained in step S4. In this case, the amount of paint to be supplied is calculated based on the amount of paint to be supplied corresponding to the integrated current value from the supply amount for the current value read in step S1.

[0045] In step S6, the "pump operation" process is executed. That is, the PLC 37 controls the pump 47 to supply the paint from the paint tank 43 to the electrodeposition tank 31.

[0046] In step S7, the process of "detecting paint flow rate" is executed. That is, the flow rate in the pipe 45 when replenishing the electrodeposition tank 31 is successively measured by the flow meter 49. The detected flow rate is input to the PLC 37, which stores it in its internal memory.

[0047] In step S8, the process "Does the paint flow rate match the calculated paint value?" is executed. That is, the PLC 37 integrates the flow rate detected in step S7 and determines whether the integrated flow rate matches the paint supply amount calculated in step S5. The flow rate is preferably integrated by storing the flow rate detected in step S7 while adding it up. If the integrated flow rate does not match the paint supply amount (NO), step S7 is repeated, and if they match (YES), the process ends. With the completion of this process, the NV concentration of the electrodeposition solution 33 in the electrodeposition tank 31 is restored. Restoring the NV concentration means bringing the NV concentration of the electrodeposition solution 33 within the allowable range.

[0048] Therefore, in this embodiment, based on the correlation between the current value and the amount of paint replenished, paint can be replenished according to the integrated current value used in electrodeposition coating of the workpieces W. This allows paint to be replenished to the electrodeposition tank 31 appropriately according to the amount of paint used for the workpieces W of different sizes and shapes that are randomly coated, and the NV concentration of the electrodeposition solution 33 in the electrodeposition tank 31 can be stabilized. As a result, in this embodiment, a stable film thickness can be obtained for the workpieces W.

[0049] By employing such an electrodeposition paint supply system in the electrodeposition process, an electrodeposition paint supply method can be realized in which paint is supplied to the electrodeposition tank 31 containing the electrodeposition solution 33.

[0050] In this electrodeposition paint replenishment method, the current used when electrodeposition coating the product workpiece W in the electrodeposition tank 31 is accumulated by the PLC 37 as described above. According to the accumulated current value, paint is replenished from the paint tank 43 to the electrodeposition tank 31, and the NV concentration of the electrodeposition solution 33 in the electrodeposition tank 31 is restored. [Explanation of symbols]

[0051] double work 21 Electrodeposition process 31 Electroplating bath 33 Electrodeposition solution 35 electrodes 36 Ammeter 37 PLC (control unit) 47 Pump

Claims

1. an electrodeposition tank containing an electrodeposition paint solution; a pump that operates in a timely manner to supply paint to the electrodeposition tank; an ammeter for measuring the current when the product is electrodeposited in the electrodeposition bath; a control unit that operates the pump in accordance with a current integrated value obtained by integrating the current used for electrodeposition coating based on the current value measured by the ammeter, and restores the NV concentration of the solution in the electrodeposition tank; The products are electrodeposited in the electrodeposition bath in succession in a number of different sizes, the control unit controls the operation of the pump so as to replenish paint in an amount corresponding to an integrated current value of the current measured for each product during one electrodeposition coating. Electrodeposition paint replenishment system.

2. 2. The electrodeposition paint replenishment system of claim 1, the control unit sets a correction coefficient based on the correlation between the coating thickness and the coating environment in which the coating thickness changes due to electrodeposition coating, and controls the operation of the pump to correct the amount of paint replenishment relative to the current integrated value using the correction coefficient. Electrodeposition paint replenishment system.

3. An electrodeposition paint replenishment method for replenishing an electrodeposition tank containing a solution of electrodeposition paint, comprising: The current is accumulated when multiple types of products of different sizes are electrodeposited in succession in the electrodeposition tank, The electrodeposition tank is replenished with paint in an amount corresponding to the integrated current value during one electrodeposition coating operation, which is integrated for each product, to restore the NV concentration of the solution in the electrodeposition tank. Electrodeposition paint replenishment method.

4. The electrodeposition paint replenishment method according to claim 3, The supply of paint to the electrodeposition tank according to the current integrated value is corrected based on the correlation between the coating film thickness and the coating environment in which the coating film thickness changes due to electrodeposition coating. Electrodeposition paint replenishment method.

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