Electrodeposition paint recovery system for changing filtrate volume by NV detection

Abstract

To control the NV value of a rinse tank to be constant in a rinsing process of a collection system after electrocoating.SOLUTION: An electrodeposition paint collection system 1 according to the present invention comprises: an electrodeposition tank 10 for electrocoating a to-be-coated object; multiple rinse tanks 21-23 for rinsing the to-be-coated object after the electrocoating, and collecting the electrodeposition paint adhered excessively to the to-be-coated object; a film filtration device 40 for filtrating the electrodeposition paint in the electrodeposition tank 10, and supplying a filtrate to the rinse tank 23, the final stage one of the multiple rinse tanks 21-23; a flow volume controller 50 for controlling the flow rate of a filtrate to be supplied to the final-stage rinse tank 23 from the film filtration device 40; and a density sensor 70, which is arranged in either of the multiple rinse tanks 21-23, for detecting the density of rinse water in the rinse tank. The flow volume controller 50 estimates the NV value of the rinse water in the rinse tank having the density sensor 70 arranged inside, on the basis of the density value of the rinse water, and controls the filtrate flow rate based on the estimated NV value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrodeposition paint recovery system that changes the amount of filtrate by detecting NV. [Background technology]

[0002] Electrodeposition coating has been widely used as a technique for coating objects such as automobile bodies.

[0003] Usually, a water washing tank is installed after the electrodeposition tank, and a water washing process is performed in the water washing tank to wash off excess electrodeposition paint from the object to be coated. The water washing process is often performed in sequence as a recovery water washing process for recovering the electrodeposition paint and a non-recovery water washing process for not recovering the electrodeposition paint. For example, Patent Document 1 discloses an electrodeposition coating apparatus having a first water washing system for performing the recovery water washing process and a second water washing system for performing the non-recovery water washing process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-235195 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the water washing process of the recovery system, it is desirable to control the NV value of the water washing tank to a constant value. Here, the NV value is the mass percentage of the residue when the target liquid is heated to evaporate the volatile components, and is a value defined by the following formula. The NV value is also called the "heating residue". NV = (residual mass of object after heating) / (mass of target liquid before heating) x 100

[0006] In the water washing process of the recovery system, if the fluctuating NV value of the water washing tank can be controlled to a constant low value, the recovery rate of the electrodeposition paint can be improved. Also, if the NV value of the water washing tank can be controlled to a constant value, the secondary sagging of the electrodeposition paint can be reduced and the coating quality can be improved.

[0007] However, it usually takes a long time to measure the NV value of a washing tank. For example, it takes about 1 to 3 hours to sample the washing water from the washing tank and measure the NV value. Therefore, it is difficult to measure the NV value of the washing tank and control the NV value of the washing tank to a constant value by varying the amount of filtrate in real time based on the measured NV value of the washing tank.

[0008] The object of the present disclosure, made in consideration of the above circumstances, is to provide an electrodeposition paint recovery system that makes it possible to control the NV value of the water washing tank to a constant value in the water washing process of the recovery system after electrodeposition coating. [Means for solving the problem]

[0009] That is, the present invention is as follows. [1] an electrodeposition tank for performing electrodeposition coating on the object to be coated; A plurality of water washing tanks for washing the workpiece after the electrodeposition coating with water and recovering excess electrodeposition paint attached to the workpiece; a membrane filtration device that filters the electrodeposition paint in the electrodeposition tank and supplies the filtrate to a final washing tank of the plurality of washing tanks; a flow rate control device for controlling a flow rate of the filtrate supplied from the membrane filtration device to the final stage water washing tank; a density sensor that is installed in any one of the plurality of washing tanks and detects the density of the washing water in the washing tank; Equipped with The flow rate control device estimates the NV value of the wash water in the wash tank in which the density sensor is installed based on the density value of the wash water, and controls the flow rate of the filtrate based on the estimated NV value. [2] In the electrodeposition paint recovery system according to [1], The flow rate control device controls the flow rate of the filtrate so that the NV value approaches a set NV value, in an electrodeposition paint recovery system. [3] In the electrodeposition paint recovery system according to [1] or [2], The flow control device, an electrocoating paint recovery system, feedback controls the flow rate of the filtrate using PID control to increase or decrease it when the difference between the NV value and the set NV value deviates from the set NV value by more than a predetermined percentage. [4] In the electrodeposition paint recovery system according to any one of [1] to [3], The flow rate control device includes: A function representing the relationship between the density of the washing water and the NV value, which is created based on previously measured data, is stored; The electrodeposition paint recovery system estimates the NV value based on the value of the density of the washing water by referring to the function. [5] [1] to [4], the electrodeposition paint recovery system according to any one of the above, The electrodeposition paint recovery system, wherein the function is a linear function. [6] [1] to [5], the electrodeposition paint recovery system according to any one of the above, An electrodeposition paint recovery system, wherein the density sensor is installed in the final stage water washing tank. [7] [1] to [6], the electrodeposition paint recovery system according to any one of the above, When the plurality of water washing tanks includes at least one dip tank, An electrocoating paint recovery system, wherein the density sensor is installed in a final dip tank among the at least one dip tank. [8] [1] to [7], the electrodeposition paint recovery system according to any one of the above, The membrane filtration device is provided with an ultrafiltration membrane or a microfiltration membrane. [9] [1] to [8], the electrodeposition paint recovery system according to any one of the above, The membrane filtration device is provided with an ultrafiltration membrane.

[10] [1] to [9], the electrodeposition paint recovery system according to any one of the above, The electrodeposition paint recovery system, wherein the density sensor is a vibration type density sensor. Effect of the Invention

[0010] According to the electrodeposition paint recovery system of the present disclosure, the NV value of the water washing tank in the water washing process of the recovery system after electrodeposition coating can be controlled to a constant value. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of an electrodeposition paint recovery system according to one embodiment. [Diagram 2] FIG. 1 is a diagram showing an example of the relationship between density and NV value. [Diagram 3] FIG. 2 is a schematic diagram of an electrodeposition paint recovery system according to a comparative example. [Figure 4A] FIG. 4 is a diagram showing an example of fluctuations in NV value in an electrodeposition paint recovery system according to a comparative example. [Figure 4B] FIG. 2 is a diagram showing an example of fluctuations in NV value in an electrodeposition paint recovery system according to one embodiment. [Diagram 5] FIG. 2 is a schematic diagram of an electrodeposition paint recovery system according to a first modified example. [Figure 6] FIG. 11 is a schematic diagram of an electrodeposition paint recovery system according to a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0013] Fig. 1 is a schematic diagram of an electrodeposition paint recovery system 1 according to one embodiment. The configuration and functions of the electrodeposition paint recovery system 1 according to one embodiment will be described with reference to Fig. 1.

[0014] The electrodeposition paint recovery system 1 includes an electrodeposition tank 10, a first rinsing tank 21, a second rinsing tank 22, a third rinsing tank 23, a first pure water rinsing tank 31, a second pure water rinsing tank 32, a membrane filtration device 40, a flow control device 50, a flow sensor 60, and a density sensor 70.

[0015] The electrodeposition tank 10 is a tank for performing electrodeposition coating on a coating object. The coating object is, for example, an automobile body. The coating object is not limited to an automobile body, and may be, for example, an automobile part, an electrical product, a building material, etc. The electrodeposition tank 10 contains an electrodeposition paint.

[0016] A first rinsing tank 21, a second rinsing tank 22, and a third rinsing tank 23 are installed downstream of the electrodeposition tank 10. The first rinsing tank 21, the second rinsing tank 22, and the third rinsing tank 23 rinse the workpiece that has been electrodeposition-coated in the electrodeposition tank 10, in that order, and recover any excess electrodeposition paint adhering to the workpiece. In other words, the first rinsing tank 21, the second rinsing tank 22, and the third rinsing tank 23 are multiple rinsing tanks that perform the rinsing process of the recovery system.

[0017] The first rinsing tank 21 is a spray tank. A spray tank is a type of rinsing tank that rinses the object by spraying rinsing water onto the object. A pump 81 is installed in the first rinsing tank 21. The pump 81 pumps up rinsing water from the bottom of the first rinsing tank 21 and sprays the pumped rinsing water from above the first rinsing tank 21 to rinse the object.

[0018] The second rinsing tank 22 is a dipping tank. A dipping tank is a type of rinsing tank in which the object to be coated is completely immersed in the rinsing water to rinse the object. A pump 82 is installed in the second rinsing tank 22. The pump 82 pumps up the rinsing water from the bottom of the second rinsing tank 22 and returns the pumped up rinsing water to the top of the second rinsing tank 22. In this way, the pump 82 circulates the rinsing water in the second rinsing tank 22.

[0019] The third washing tank 23 is a spray tank. A pump 83 is installed in the third washing tank 23. The pump 83 pumps up washing water from the lower part of the third washing tank 23, and sprays the pumped washing water from above the third washing tank 23 to wash the object to be coated.

[0020] 1 shows a configuration in which the washing step of the recovery system includes three washing tanks, namely, the first washing tank 21, the second washing tank 22, and the third washing tank 23, but this is just an example. The washing step of the recovery system may include any number of washing tanks, which may be one or more.

[0021] Also, the case where the first water washing tank 21 and the third water washing tank 23 are spray tanks and the second water washing tank 22 is a dip tank has been described, but this is just one example. The first water washing tank 21, the second water washing tank 22 and the third water washing tank 23 may each be either a spray tank or a dip tank.

[0022] A first pure water rinsing tank 31 and a second pure water rinsing tank 32 are installed downstream of the third rinsing tank 23. The first pure water rinsing tank 31 and the second pure water rinsing tank 32 rinse the workpiece with pure water in this order after it has been rinsed in the third rinsing tank 23. The first pure water rinsing tank 31 and the second pure water rinsing tank 32 do not recover the electrodeposition paint. In other words, the first pure water rinsing tank 31 and the second pure water rinsing tank 32 are multiple rinsing tanks that perform a non-recovery rinsing process.

[0023] The first pure water rinsing tank 31 is a dip tank, and the second pure water rinsing tank 32 is a spray tank.

[0024] 1, the non-recovery washing step is shown to have two washing tanks, the first pure water washing tank 31 and the second pure water washing tank 32, but this is just an example. The non-recovery washing step may have any number of washing tanks, which may be one or more.

[0025] In addition, the first pure water rinsing tank 31 is a dip tank and the second pure water rinsing tank 32 is a spray tank in the above description, but this is merely an example. Each of the first pure water rinsing tank 31 and the second pure water rinsing tank 32 may be either a spray tank or a dip tank.

[0026] The membrane filtration device 40 includes an ultrafiltration membrane or a microfiltration membrane. An ultrafiltration membrane is also called a UF membrane. A microfiltration membrane is also called a MF membrane.

[0027] The membrane filtration device 40 filters the electrodeposition paint in the electrodeposition tank 10. The membrane filtration device 40 supplies the filtrate after filtering the electrodeposition paint to the third water washing tank 23, which is the final water washing tank in the water washing process of the recovery system, via a flow rate control device 50.

[0028] As described above, since the filtrate is supplied from the membrane filtration device 40, the washing water in the third washing tank 23 contains the filtrate supplied from the membrane filtration device 40. The washing water in the third washing tank 23 overflows in turn into the second washing tank 22 and the first washing tank 21, and further overflows from the first washing tank 21 into the electrodeposition tank 10. In this way, the first washing tank 21, the second washing tank 22, and the third washing tank 23, which perform the washing steps of the recovery system, can recover the electrodeposition paint.

[0029] The membrane filtration device 40 is connected to the electrodeposition tank 10 via a flow path 101 and a flow path 102. In addition, the membrane filtration device 40 is connected to the flow rate control device 50 via a flow path 103.

[0030] The electrodeposition paint in the electrodeposition tank 10 is supplied to the membrane filtration device 40 via a flow path 101. The membrane filtration device 40 filters the supplied electrodeposition paint using an ultrafiltration membrane or a microfiltration membrane. The membrane filtration device 40 supplies the filtered filtrate to the flow control device 50 via a flow path 103. The membrane filtration device 40 returns the concentrated water that did not permeate the ultrafiltration membrane or the microfiltration membrane to the electrodeposition tank 10 via a flow path 102.

[0031] The flow rate control device 50 controls the flow rate of the filtrate supplied from the membrane filtration device 40 to the third washing tank 23. The flow rate control device 50 may include a valve for controlling the flow rate of the filtrate. The flow rate control device 50 may also include a processor for controlling the valve, and a memory. The control of the flow rate of the filtrate by the flow rate control device 50 will be described in detail later.

[0032] The flow rate sensor 60 detects the flow rate of the filtrate supplied from the membrane filtration device 40 to the third washing tank 23. The flow rate sensor 60 may be a flow rate sensor of any configuration capable of detecting the flow rate of the filtrate.

[0033] The density sensor 70 is installed in any one of the first washing tank 21, the second washing tank 22, and the third washing tank 23, which are washing tanks in the washing step of the recovery system. Fig. 1 shows a case where the density sensor 70 is installed in the third washing tank 23. Hereinafter, an example where the density sensor 70 is installed in the third washing tank 23 will be described.

[0034] The density sensor 70 detects the density of the wash water in the third wash tank 23. The density sensor 70 is not limited to this, but may be, for example, a vibration type density sensor. When the density sensor 70 is a vibration type density sensor, the density sensor 70 can accurately detect the density of the wash water in the third wash tank 23 in real time.

[0035] The density sensor 70 is capable of communicating with the flow rate control device 50. When the density sensor 70 detects the density of the water washing tank of the third water washing tank 23, the density sensor 70 transmits the detected density value to the flow rate control device 50.

[0036] Next, a process in which the flow rate control device 50 controls the flow rate of the filtrate supplied from the membrane filtration device 40 to the third washing tank 23 will be described.

[0037] The density sensor 70 constantly detects the density of the wash water in the third wash tank 23. The density sensor 70 transmits the detected value of the density of the wash water in the third wash tank 23 to the flow rate control device 50.

[0038] When the flow control device 50 acquires the density value of the washing water in the third washing tank 23 from the density sensor 70, it estimates the NV value of the washing water in the third washing tank 23 in which the density sensor 70 is installed based on the acquired density value.

[0039] Here, the NV value is the mass percentage of the residue when the target liquid is heated to evaporate the volatile components, and is defined by the following formula. The NV value is also called the "heating residue". NV = (residual mass of object after heating) / (mass of target liquid before heating) x 100

[0040] The flow rate control device 50 stores in a memory a function that represents the relationship between the density of the wash water and the NV value, which is created based on previously measured data.

[0041] FIG. 2 shows an example of the relationship between the density of wash water and the NV value. FIG. 2 is a diagram showing a state in which a function 201 expressing the relationship between the density of wash water and the NV value is created based on measurement data of four points that are actually measured. In the example shown in FIG. 2, the function 201 expressing the relationship between the density of wash water and the NV value is a linear function. In FIG. 2, the linear function is created based on measurement data of four points, but a linear function may be created based on measurement data of two or more points. Note that approximation with a linear function is just one example, and the relationship between the density of wash water and the NV value may be approximated with any function based on measurement data that is actually measured.

[0042] The flow rate control device 50 may store a function that indicates the relationship between the density of the washing water and the NV value for each type of electrodeposition paint.

[0043] When estimating the NV value of the wash water based on the density value obtained from the density sensor 70, the flow rate control device 50 estimates the NV value by referring to a stored function that represents the relationship between the density of the wash water and the NV value.

[0044] Based on the estimated NV value, the flow rate control device 50 controls the flow rate of the filtrate supplied from the membrane filtration device 40 to the third washing tank 23. The flow rate control device 50 may automatically control a valve to control the flow rate of the filtrate.

[0045] The recovery rate of the electrodeposition paint can be improved if the NV value of the third washing tank 23, which is the final washing tank in the washing process of the recovery system, is close to a set NV value. The set NV value is, for example, about 0.6%. For example, if the NV value of the third washing tank 23 can be maintained at about 0.6%, the recovery rate of the electrodeposition paint can be about 97%. This is an improved recovery rate compared to the 95 to 96% recovery rate of electrodeposition paint in a normal electrodeposition paint recovery system.

[0046] The flow rate control device 50 controls the flow rate of the filtrate supplied from the membrane filtration device 40 to the third water washing tank 23 so that the NV value approaches a set NV value. The set NV value may be, for example, 0.6%. This allows the electrodeposition paint recovery system 1 to improve the recovery rate of the electrodeposition paint.

[0047] The flow control device 50 may control the flow rate of the filtrate so that the NV value approaches the set NV value by, for example, increasing or decreasing the flow rate of the filtrate through feedback control using PID control. In this case, for example, the flow control device 50 may start feedback control when the difference between the estimated NV value and the set NV value deviates from the set NV value by a predetermined ratio or more. In this case, when the difference between the estimated NV value and the set NV value is less than the predetermined ratio to the set NV value, the flow control device 50 does not increase or decrease the flow rate of the filtrate, and when the difference between the estimated NV value and the set NV value becomes a predetermined ratio or more to the set NV value, the flow control device 50 increases or decreases the flow rate of the filtrate. The predetermined ratio may be, for example, 1%.

[0048] If the estimated NV value is greater than the set NV value, the flow control device 50 increases the flow rate of the filtrate to lower the NV value. If the estimated NV value is less than the set NV value, the flow control device 50 decreases the flow rate of the filtrate to raise the NV value.

[0049] As described above, in the electrodeposition paint recovery system 1 according to the present embodiment, the flow control device 50 estimates the NV value of the wash water based on the density value of the wash water detected by the density sensor 70, and automatically controls the flow rate of the filtrate supplied from the membrane filtration device 40 to the third wash tank 23, which is the final wash tank, based on the estimated NV value. As a result, the electrodeposition paint recovery system 1 according to the present embodiment can control the NV value of the wash tank to a constant value in the wash process of the recovery system after the electrodeposition coating. In this way, by controlling the NV value of the wash tank to a constant value, the electrodeposition paint recovery system 1 according to the present embodiment can improve the recovery rate of the electrodeposition paint. In addition, the electrodeposition paint recovery system 1 according to the present embodiment can reduce the loss of the electrodeposition paint in the wash process of the non-recovery system, which is the process subsequent to the wash process of the recovery system, by improving the recovery rate of the electrodeposition paint.

[0050] (Comparative Example) FIG. 3 is a schematic diagram of an electrodeposition paint recovery system 300 according to a comparative example.

[0051] The electrodeposition paint recovery system 300 according to the comparative example includes an electrodeposition tank 10, a first water washing tank 21, a second water washing tank 22, a third water washing tank 23, a first pure water washing tank 31, a second pure water washing tank 32, a membrane filtration device 40, a flow rate sensor 60, and a valve 310. The electrodeposition paint recovery system 300 according to the comparative example may include an intermediate tank between the membrane filtration device 40 and the third water washing tank 23. When the intermediate tank is included, the intermediate tank may be installed either before or after the valve 310. When the intermediate tank is included, the intermediate tank may be installed either before or after the flow rate sensor 60.

[0052] The electrodeposition paint recovery system 300 of the comparative example differs from the electrodeposition paint recovery system 1 shown in FIG. 1 in that it has a valve 310 instead of the flow control device 50 and does not have a density sensor 70.

[0053] The valve 310 is a valve for manually controlling the flow rate of the filtrate supplied from the membrane filtration device 40 to the third washing tank 23 .

[0054] In the electrodeposition paint recovery system 300 according to the comparative example, the flow rate of the filtrate cannot be controlled based on the estimated NV value, so the valve 310 is manually set to allow a constant amount of filtrate to flow. The constant amount of filtrate is, for example, about 60 [L / min].

[0055] With reference to Figs. 4A and 4B, the fluctuation of the NV value in the electrodeposition paint recovery system 300 according to the comparative example will be compared with the fluctuation of the NV value in the electrodeposition paint recovery system 1 according to the embodiment.

[0056] Fig. 4A is a diagram showing a typical variation in NV value over a week in the electrodeposition paint recovery system 300 according to the comparative example. Fig. 4B is a diagram showing a typical variation in NV value over a week in the electrodeposition paint recovery system 1 according to the embodiment shown in Fig. 1.

[0057] First, referring to FIG. 4A, a description will be given of the fluctuation of the NV value over one week in the electrodeposition paint recovery system 300 according to the comparative example.

[0058] The electrodeposition paint recovery system 300 according to the comparative example operates from 7:00 to 24:00 from Monday to Friday, and does not operate on Saturday and Sunday. Also, the electrodeposition paint recovery system 300 according to the comparative example has a filtrate flow rate set to a constant amount of 60 [L / min].

[0059] In the electrodeposition paint recovery system 300 according to the comparative example, when operation is started at 7:00 on Monday, the NV value gradually increases. Then, when operation is stopped at midnight on Monday, the NV value gradually decreases until 7:00 on Tuesday. However, the NV value at 7:00 on Tuesday is greater than the NV value at 7:00 on Monday. Then, when operation is started at 7:00 on Tuesday, the NV value gradually increases again.

[0060] If this process is repeated during the weekdays, the NV value will increase to close to 1.0% by midnight on Friday. As described above, the electrodeposition paint recovery system 300 according to the comparative example has large fluctuations in the NV value.

[0061] During such an operation, the recovery rate of the electrodeposition paint in the electrodeposition paint recovery system 300 according to the comparative example is about 95 to 96%.

[0062] Next, a description will be given of the fluctuation of the NV value over one week in the electrodeposition paint recovery system 1 according to the embodiment shown in FIG. 1, with reference to FIG. 4B.

[0063] The electrodeposition paint recovery system 1 according to one embodiment also operates from 7:00 to 24:00 from Monday to Friday, and does not operate on Saturday and Sunday. In addition, the electrodeposition paint recovery system 1 according to one embodiment controls the flow rate of the filtrate based on the estimated NV value, so the flow rate of the filtrate increases and decreases between 30 and 90 [L / min].

[0064] In the electrodeposition paint recovery system 1 according to one embodiment, when operation is started at 7:00 on Monday, the NV value increases slightly but remains close to 0.6%. Then, when operation is stopped at midnight on Monday, the NV value gradually decreases until 7:00 on Tuesday. As a result, the NV value at 7:00 on Tuesday is approximately the same as the NV value at 7:00 on Monday.

[0065] In this way, in the electrodeposition paint recovery system 1 according to one embodiment, the NV value is maintained close to the set NV value from Monday to Friday.

[0066] During such operation, the recovery rate of electrodeposition paint in the electrodeposition paint recovery system 1 according to one embodiment is about 97%. This recovery rate is higher than the recovery rate of electrodeposition paint in the electrodeposition paint recovery system 300 according to the comparative example, which is 95 to 96%.

[0067] (First Modification) Fig. 5 is a schematic configuration diagram of an electrodeposition paint recovery system 2 according to a first modified example. The configuration and function of the electrodeposition paint recovery system 2 according to the first modified example will be described with reference to Fig. 5.

[0068] The electrodeposition paint recovery system 2 of the first modified example includes an electrodeposition tank 10, a first water washing tank 21, a second water washing tank 22, a third water washing tank 23, a first pure water washing tank 31, a second pure water washing tank 32, a membrane filtration device 40, a flow control device 50, a flow sensor 60, and a density sensor 70.

[0069] The electrodeposition paint recovery system 2 according to the first modified example differs from the electrodeposition paint recovery system 1 shown in FIG.

[0070] Regarding the electrodeposition paint recovery system 2 relating to the first modified example, the differences from the electrodeposition paint recovery system 1 shown in Figure 1 will be mainly explained, and explanations of points in common or similar to the electrodeposition paint recovery system 1 shown in Figure 1 will be omitted as appropriate.

[0071] In the electrodeposition paint recovery system 2 according to the first modified example, the first water rinsing tank 21 and the third water rinsing tank 23 are spray tanks, and the second water rinsing tank 22 is a dip tank.

[0072] In the electrodeposition paint recovery system 2 according to the first modification, the density sensor 70 is installed in the final dip tank among the dip tanks included in the water washing process of the recovery system. In the electrodeposition paint recovery system 2 according to the first modification shown in Fig. 5, only the second water washing tank 22 is a dip tank, and the first water washing tank 21 and the third water washing tank 23 are spray tanks, so that the second water washing tank 22 is the final dip tank.

[0073] For example, when the first washing tank 21 and the second washing tank 22 are dip layers and the third washing tank 23 is a spray tank, the second washing tank 22 is the final dip layer, so the density sensor 70 is installed in the second washing tank 22. Also, when the first washing tank 21 is a spray tank and the second washing tank 22 and the third washing tank 23 are dip layers, the third washing tank 23 is the final dip layer, so the density sensor 70 is installed in the third washing tank 23.

[0074] Thus, in the electrodeposition paint recovery system 2 of the first modified example, when the water washing process of the recovery system includes at least one dip tank, the density sensor 70 is installed in the final dip tank of the at least one dip tank.

[0075] Then, the flow rate control device 50 can control the flow rate of the filtrate supplied from the membrane filtration device 40 to the third washing tank 23 so that the NV value of the washing water in the final stage dip tank approaches the set NV value. The set NV value may be, for example, about 1.0%.

[0076] By bringing the NV value of the washing water in the final dipping tank closer to the set NV value in this way, the electrodeposition paint recovery system 2 according to the first modified example can reduce secondary dripping of the electrodeposition paint on the workpiece and improve the coating quality. This is because the NV value of the washing water in the final dipping tank affects the coating quality, and so by maintaining the NV value of the final dipping tank close to the set NV value, the variation in coating quality can be reduced. In this way, in order to improve the coating quality, it is necessary to install a density sensor 70 at least in the final dipping tank.

[0077] (Second Modification) Fig. 6 is a schematic diagram of an electrodeposition paint recovery system 3 according to a second modified example. The configuration and functions of the electrodeposition paint recovery system 3 according to the second modified example will be described with reference to Fig. 6.

[0078] The electrodeposition paint recovery system 3 of the second modified example includes an electrodeposition tank 10, a first water washing tank 21, a second water washing tank 22, a third water washing tank 23, a first pure water washing tank 31, a second pure water washing tank 32, a membrane filtration device 40, a flow control device 50, a flow sensor 60, and an intermediate tank 90.

[0079] The electrodeposition paint recovery system 3 according to the second modified example differs from the electrodeposition paint recovery system 1 shown in FIG.

[0080] Regarding the electrodeposition paint recovery system 3 relating to the second variant example, the differences from the electrodeposition paint recovery system 1 shown in Figure 1 will be mainly explained, and explanations of points in common or similar to the electrodeposition paint recovery system 1 shown in Figure 1 will be omitted as appropriate.

[0081] In the electrodeposition paint recovery system 3 according to the second modification, the membrane filtration device 40 does not directly supply the filtrate to the third washing tank 23. Instead, the membrane filtration device 40 temporarily supplies the filtrate to the intermediate tank 90. ​​The filtrate stored in the intermediate tank 90 is then supplied to the third washing tank 23. At this time, the intermediate tank 90 supplies the filtrate to the third washing tank 23 by a pump 84 installed in the intermediate tank 90.

[0082] Although the above-mentioned embodiment has been described as a representative example, it is obvious to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present disclosure. Therefore, the present invention should not be interpreted as being limited by the above-mentioned embodiment, and various modifications or changes are possible without departing from the scope of the claims.

[0083] For example, in the electrodeposition paint recovery system 1 according to one embodiment shown in FIG. 1, the density sensor 70 is installed in the third water washing tank 23, and in the electrodeposition paint recovery system 2 according to the first modified example shown in FIG. 5, the density sensor 70 is installed in the second water washing tank 22. However, the water washing tanks in which the density sensor 70 is installed are not limited to these. The density sensor 70 may be installed in any of the water washing tanks in the water washing step of the recovery system. Furthermore, the number of density sensors 70 is not limited to one, and the density sensor 70 may be installed in multiple water washing tanks in the water washing step of the recovery system. [Explanation of symbols]

[0084] 1, 2, 3 Electrochemical Paint Recovery System 10 Electroplating bath 21 First washing tank 22 Second washing tank 23 Third washing tank 31 First pure water washing tank 32 Second pure water washing tank 40 Membrane filtration equipment 50 Flow Control Device 60 Flow Sensor 70 Density Sensor 81, 82, 83, 84 Pumps 90 Intermediate Tank 101, 102, 103 Flow path 300 Electrochemical Paint Recovery System 310 Valve

Claims

1. an electrodeposition tank for performing electrodeposition coating on the object to be coated; a plurality of water washing tanks for washing the workpiece after the electrodeposition coating with water and recovering excess electrodeposition paint adhering to the workpiece; a membrane filtration device that filters the electrodeposition paint in the electrodeposition tank and supplies a filtrate to a final washing tank of the plurality of washing tanks; a flow rate control device for controlling a flow rate of the filtrate supplied from the membrane filtration device to the final stage water washing tank; a density sensor that is installed in any one of the plurality of washing tanks and detects the density of the washing water in the washing tank; Equipped with The flow rate control device estimates the NV value of the wash water in the wash tank in which the density sensor is installed based on the density value of the wash water, and controls the flow rate of the filtrate based on the estimated NV value.

2. The electrodeposition paint recovery system according to claim 1, The flow rate control device controls the flow rate of the filtrate so that the NV value approaches a set NV value, in an electrodeposition paint recovery system.

3. In the electrodeposition paint recovery system according to claim 2, The flow control device, in an electrocoating paint recovery system, increases or decreases the flow rate of the filtrate by feedback control using PID control when the difference between the NV value and the set NV value deviates from the set NV value by more than a predetermined percentage.

4. The electrodeposition paint recovery system according to claim 1, The flow rate control device includes: a function representing the relationship between the density of the washing water and the NV value, the function being created based on previously measured data; The electrodeposition paint recovery system estimates the NV value based on the density of the washing water by referring to the function.

5. In the electrodeposition paint recovery system according to claim 4, The electrodeposition paint recovery system, wherein the function is a linear function.

6. The electrodeposition paint recovery system according to claim 1, An electrodeposition paint recovery system, wherein the density sensor is installed in the final stage water washing tank.

7. The electrodeposition paint recovery system according to claim 1, When the plurality of water washing tanks includes at least one dip tank, An electrodeposition paint recovery system, wherein the density sensor is installed in a final stage dip tank among the at least one dip tank.

8. The electrodeposition paint recovery system according to claim 1, The membrane filtration device is provided with an ultrafiltration membrane or a microfiltration membrane.

9. The electrodeposition paint recovery system according to claim 1, The membrane filtration device is provided with an ultrafiltration membrane.

10. The electrodeposition paint recovery system according to claim 1, The electrodeposition paint recovery system, wherein the density sensor is a vibration type density sensor.

Images