JP3584724B2 - Method of measuring electrodeposition film thickness - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for measuring an electrodeposition film thickness in an electrodeposition coating line of an automobile body, and more particularly, to an electrode capable of measuring and managing the electrodeposition film thickness on the inner surface of a bag structure with high accuracy without dismantling an actual vehicle in an actual line. The present invention relates to a method for measuring a deposited film thickness.
[0002]
[Prior art]
For the coating of automobile bodies, a three-coat coating system consisting of undercoating, intermediate coating, and topcoating is used. Among these, the undercoating process includes water washing, degreasing, surface conditioning, chemical conversion, electrodeposition coating, etc. It consists of various steps.
[0003]
The electrodeposition coating employs a so-called full-dip method in which an automobile body is continuously immersed in an electrodeposition tank filled with an electrodeposition coating liquid, and is subjected to a subsequent washing step and a drying step to form an inner and outer plate of the automobile body. An electrodeposition coating film is formed on the surface.
[0004]
Of the electrodeposited coating film formed on the automobile body, the electrodeposition film thickness of the outer plate surface and other visible portions can be measured using a thickness gauge, but the body sill B1 of the automobile body B shown in FIG. Since the probe of the film thickness meter cannot be inserted into the inner surface B2 of the bag structure portion such as various members, the electrodeposition film thickness cannot be measured unless the body B is disassembled.
[0005]
For this reason, the electrodeposited film thickness of the inner surface B2 of such a bag structure portion is measured on an actual line in a state where a strip-shaped steel plate 11 (hereinafter also referred to as a searcher) as shown in FIG. The electrodeposition coating is performed, the searcher 11 is extracted after the electrodeposition coating, and the electrodeposition film thickness formed on the searcher 11 is measured with a film thickness meter, thereby indirectly controlling the quality of the electrodeposition coating process. Was.
[0006]
[Problems to be solved by the invention]
However, with the method of inserting the searcher 11 into the actual bag structure, the inserted state cannot be visually confirmed. In particular, since such a searcher 11 is inserted into a bag structure having a complicated shape, which is considered to have the worst electrodeposition, it is uncertain whether or not it is set in a predetermined position. There is a problem that the thickness value is also unstable, has a large variation, and the measurement accuracy is low.
[0007]
Further, even when the searcher 11 is inserted into a bag structure part with poor electrodeposition, the searcher 11 tends to be thicker than the actual vehicle. For this reason, there is a problem in the accuracy of the correspondence between the change in the film thickness of the actual vehicle and the film thickness of the searcher, and as a result, it has been inevitably used to roughly manage the tendency of the electrodeposition film thickness.
[0008]
The present invention has been made in view of such problems of the prior art, and is capable of measuring and managing the electrodeposition film thickness on the inner surface of the bag structure with high accuracy without dismantling the actual vehicle. The aim is to provide a method.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a method for measuring an electrodeposited film thickness according to claim 1 is a method for measuring an electrodeposited film thickness of an object to be electrodeposited in an actual line. A searcher having a lower turning property with electrodeposition than the turning property with electrodeposition at a target portion is set on the object to be coated, and an electrodeposition coating film is formed on the searcher together with the object to be coated by the actual line, The thickness of the electrodeposited coating film formed on the object to be measured is determined based on the thickness of the electrodeposited coating film formed on the substrate .
[0010]
Regarding the throwing power of the electrodeposition paint, the coulomb amount of the current flowing through the object to be coated is Q (c), the total surface area of the outer and inner plates of the object is S (m ² ), Assuming that the film thickness is M (μm), the specific gravity of the electrodeposited coating is ρ, and the Coulomb efficiency of the electrodeposition coating is C (mg / c),
(Equation 1)
Q / S = kMρ / C (k is a constant) (1)
Is known to hold. In the equation (1), the specific gravity ρ of the electrodeposition coating film and the coulomb efficiency C of the electrodeposition coating material are constant depending on the type of the electrodeposition coating material. , Q / S. That is, since the surface area S of the vehicle body is constant, the electrodeposition film thickness M is eventually proportional to the Coulomb amount Q of the current flowing through the body.
[0011]
However, with respect to the turning performance with electrodeposition when the car body is electrodeposited on a real line, the energization time, that is, the time during which the car body is immersed in the electrodeposition tank is finite, and the car body is complicated. Due to the structure, a portion where the current easily flows (for example, the door outer panel) and a portion where the current does not easily flow (for example, the inner surface of the side sill bag structure) are relatively generated.
[0012]
For this reason, as shown in FIG. 5, in the initial stage of entering a tank, electric energy concentrates on a portion such as a door outer where an electric current easily flows, and an electrodeposition coating film is formed thereon, as shown in FIG. Is done. Since the total amount of electric energy supplied from the electrode plate provided in the electrodeposition tank is constant, almost no electric energy is supplied to a portion where current does not easily flow, such as the inner surface of the body sill bag structure, Therefore, an electrodeposition coating film is hardly formed on such a portion.
[0013]
After a certain amount of time has passed after entering the tank and an electrodeposition coating film is formed on a part where current flows easily such as a door outer, the electric resistance value of the part gradually increases due to the formed coating film, The electric energy supplied to these parts also gradually decreases. Then, the electric energy is supplied to the portion where the current easily flows next, and finally the electric energy is supplied to the portion where the current hardly flows, and the electrodeposition coating film is formed here, The tank comes out in the middle of the film formation process.
[0014]
In other words, when an actual vehicle is electrodeposited on an actual line, a portion having good turning properties with electrodeposition has obtained a sufficient amount of electricity, and the formed film thickness is in a state of being asymptotic to a saturated state. Even if the electrodeposition conditions are slightly different, the amount of change in the formed film thickness is extremely small. In other words, the thickness of the electrodeposited film at a portion excellent in the electrodeposition-related turning property is insensitive to changes in the electrodeposition conditions.
[0015]
On the other hand, the portion having poor turning property with electrodeposition comes out of the tank before a sufficient amount of current is supplied, and the film thickness formed here is far from the saturated state. Therefore, if the electrodeposition conditions are different, the formed film thickness reacts sharply. That is, by measuring the amount of change in the electrodeposition film thickness in a portion having poor electrodeposition turning properties, it is possible to appropriately manage changes in the electrodeposition conditions.
[0016]
From such a viewpoint, the present inventor sets a searcher having a lower turning property with electrodeposition than the turning property with electrodeposition at a measurement target portion of the coating object on the coating object, and sets the searcher together with the coating object with the actual line by a real line. An electrodeposition coating film was formed, the film thickness of the electrodeposition coating film formed on the searcher was measured, and the electrodeposition film thickness of the measurement target portion of the object to be coated was determined based on the film thickness .
[0017]
In the method for measuring the thickness of an electrodeposited film according to the present invention, a change in the thickness of a portion to be measured can be accurately recognized only by measuring the thickness of the electrodeposited film formed on the searcher using a film thickness meter. In other words, by using the thickness of the searcher that is most sensitive to changes in the electrodeposition conditions, it is possible to more accurately control the thickness of the measurement target portion.
[0018]
In the invention according to claim 1, the means for lowering the electrodeposited turning property of the searcher than the electrodepositioned turning property of the measurement target portion is not particularly limited, but in the method of measuring the electrodeposited film thickness according to claim 2, And determining the turnability of the searcher with the electrodeposition so that at least a non-electrodeposited portion is formed on the searcher.
[0019]
The boundary between the electrodeposited part and the undeposited part is the most sensitive to changes in electrodeposition conditions, so if a searcher is configured to form such an undeposited part, more accurate measurement will be possible. It can be performed.
[0020]
In the invention according to the second aspect, there is no particular limitation on how to determine the state of formation of the electrodeposition coating film using a searcher in which an undeposited portion of the electrodeposition is formed. In the method of measuring the film thickness, the determination is made based on the length of the undeposited portion of the electrodeposition formed on the searcher.
[0021]
The electrodeposited paint usually contains a pigment, and the electrodeposited portion and the undeposited portion can be clearly distinguished visually. Changes in the wearing conditions can be measured with high accuracy.
[0022]
In the present invention, the specific structure of the searcher is not particularly limited, but in the method for measuring an electrodeposition film thickness according to claim 4, the searcher is a strip-shaped steel plate having substantially the same potential as the object to be coated, And a nonconductive pipe into which the strip-shaped steel plate is inserted.
[0023]
By using a strip-shaped steel plate, it is easy to obtain and inexpensive, and the measurement sensitivity of the length of the undeposited portion is improved. In addition, if the pipe used to reduce the turnability with electrodeposition is formed from a non-conductor, the conduction state between the strip-shaped steel sheet and the pipe can be maintained constant during the film formation process. Further, since the electrodeposition coating film is not formed on the nonconductive pipe, the pipe can be used semipermanently. Therefore, it is possible to minimize variations due to searcher manufacturing errors.
[0024]
In the present invention, the measurement target site of the object to be coated is not particularly limited, but a bag structure portion that cannot be measured with a film thickness meter, among them, a body sill inner surface where a rust environment is severe, an inner surface of various members around a foot, etc. Can be mentioned.
[0025]
【The invention's effect】
According to the first aspect of the present invention, since the coating film formation state of the searcher, which is most sensitive to changes in electrodeposition conditions, is used, the inner surface of the bag structure and other measurement target sites can be measured without dismantling the actual vehicle. The film thickness can be controlled more accurately.
[0026]
According to the second aspect of the present invention, the boundary between the electrodeposited portion and the non-deposited portion has the highest sensitivity to the change in the electrodeposition condition, and the searcher is configured to form such a non-deposited portion. With the configuration, more accurate measurement can be performed.
[0027]
According to the third aspect of the present invention, since the electrodeposited portion and the non-deposited portion of the searcher can be clearly distinguished visually, only by measuring the length of the non-deposited portion, the electrodeposition can be performed. Changes in conditions can be measured with high accuracy, and the measurement operation is simple.
[0028]
According to the fourth aspect of the present invention, since the strip-shaped steel plate is employed, it is easy to obtain and inexpensive, and the measurement sensitivity of the length of the electrodeposited portion is improved. In addition, since a nonconductive pipe is employed, the conductive state between the strip-shaped steel plate and the pipe can be maintained constant during the film forming process. Further, since the electrodeposited coating film is not formed on the nonconductive pipe, the pipe is formed. Can be used semi-permanently. Therefore, it is possible to minimize variations due to searcher manufacturing errors.
[0029]
According to the fifth aspect of the present invention, the thickness of the inner surface of the body sill, in which the rust environment is particularly severe, can be accurately controlled, and the reliability of the rust prevention quality of the automobile body is improved.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of an automobile body showing a mounting portion of a searcher according to the present invention, FIG. 2 is a perspective view showing an embodiment of the searcher, FIG. 3 is a sectional view taken along line III-III of FIG. It is a perspective view showing a searcher after painting.
[0031]
First, the searcher 1 used in the present embodiment includes a strip-shaped steel plate 11 and a nonconductive pipe 12. As the belt-shaped steel plate 11, for example, a body steel plate (for example, a cold-rolled steel plate) having a thickness of about 1.4 mm, a width of about 20 mm, and a length of about 1000 mm is used. Holes 111 are formed at both ends of the strip-shaped steel plate 11 for fixing the inside of the body B to the room. This fixing is performed in order to set the same potential as the inner surface B2 of the sill by grounding the belt-shaped steel plate 11 (in the case of cationic electrodeposition). Note that the direction in which the strip-shaped steel plate 11 is fixed in the room is not limited to the present embodiment, but may be a method of fixing (earthing) using a dedicated jig.
[0032]
On the other hand, the pipe 12 is a tubular body formed of, for example, a non-conductive vinyl chloride resin and having both ends opened, and has an inside diameter into which the above-described strip-shaped steel plate 11 can be inserted. Then, the band-shaped steel plate 11 is inserted into the pipe 12, and the searcher 1 is fixed in the room of the body B using the holes 111 of the band-shaped steel plate 11 as shown in FIG. At this time, the pipe 12 itself may be fixed or may be left inserted in the strip-shaped steel plate 11.
[0033]
It is desirable that the fixed position of the searcher 1 be as close as possible to the part to be measured for the electrodeposition film thickness (in this embodiment, the inner surface B2 of the side sill B1 of the body B).
[0034]
Further, the inner diameter of the pipe 12 is at least large enough to insert the strip-shaped steel plate 11 and is smaller than the inner surface B2 of the sill B1, which is the site to be measured for the electrodeposition film thickness, with a lower turning property.
[0035]
Here, the turning property with electrodeposition will be described.
In a bag structure, for example, a box body formed of a steel plate, a plurality of holes for introducing an electrodeposition coating liquid are formed, and the box body is immersed in an electrodeposition tank to perform electrodeposition coating, and the outer surface of the box body is formed. Since the voltage from the electrode plate acts directly on the substrate and a large current flows, an electrodeposition coating film is formed by electrophoresis immediately after immersion. On the other hand, although the electrodeposition coating liquid introduced from the introduction hole comes into contact with the inner surface of the box body, the current initially flows only in the vicinity of the introduction hole. Therefore, the electrodeposited coating film is gradually formed on the inner surface of the box body from around the introduction hole, and when the coating film resistance increases as the film thickness increases, the range of the coating film gradually increases.
[0036]
As described above, since the electrodeposition coating film is formed on the inner surface of the bag structure from the vicinity of the opening through which the current flows, holes for electrodeposition and rotation are formed in the sill B1 of the body B at a predetermined pitch. Is common. In this case, a thicker electrodeposited coating film can be formed in a shorter time as long as the diameter of the hole for electrodeposition is large.
[0037]
Also in the searcher 1 used in the present embodiment, the current flows from only the openings at both ends of the pipe 12, so that the electrodeposition coating film is gradually formed on both ends of the strip-shaped steel plate 11.
[0038]
Therefore, as in the present invention, when deciding a searcher 1 having a lower turning property with electrodeposition than the inner surface B2 of the target sill B1, the inner diameter and length of the pipe 12, the fixing place in the body B chamber, etc. Should be considered. For example, the smaller the inner diameter of the pipe 12 and the longer the length of the pipe 12, the lower the turning property of the strip-shaped steel sheet 11 with electrodeposition. Further, even in the room of the same body B, the turnability with electrodeposition is low in the center and near the floor.
[0039]
In consideration of these points, before actually performing the measurement, the shape of the searcher 1 having a lower turnability with electrodeposition than the inner surface B2 of the sill B1 of the actual vehicle is determined in advance. In this case, as shown in FIG. 4, the shape of the searcher 1 is determined so that an undeposited portion of the electrodeposition near the center of the belt-like steel plate 11 of the searcher 1 appears, for example, about 100 mm. In addition, since the film thickness formed on the inner surface B2 of the sill is substantially the same for the same vehicle type, it is desirable to determine the shape of the searcher 1 for each vehicle type.
[0040]
In order to measure the film thickness of the sill inner surface B2 in the actual line using the searcher 1 thus formed, first, an unpainted steel strip 11 is inserted into a PVC pipe 12, and the searcher 1 is placed in a white body. In the room B, fix it with a conductor (such as wire) and ground it. It is desirable that the fixed position of the searcher 1 be near the sill inner surface B2, as shown in FIGS.
[0041]
In this state, the white body B is put into a pretreatment step, an electrodeposition coating step, and an electrodeposition drying step to perform electrodeposition coating on a real line, and an electrodeposition coating film is formed on the strip-shaped steel sheet 11 together with the body B. .
[0042]
The searcher 1 is removed from the body B that has exited from the electrodeposition drying furnace, and the length L of the non-electrodeposited portion of the steel strip 11 is measured as shown in FIG. As shown in FIG. 6, a portion having relatively poor electrodeposition turning sensitivity reacts sensitively to changes in electrodeposition conditions (electrodeposition voltage in the example shown in FIG. 6). By controlling the length L of the deposited portion, it is possible to accurately control the electrodeposited film thickness of the inner surface B2 of the sill having a better surrounding environment for electrodeposition.
[0043]
The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.
[0044]
In particular, the specific dimensions of the strip-shaped steel plate 11 and the PVC pipe 12 of the searcher 1 and the fixing position of the searcher 1 are merely examples for understanding the present invention, and are not limited thereto.
[Brief description of the drawings]
FIG. 1 is a perspective view of an automobile body showing a mounting portion of a searcher according to the present invention.
FIG. 2 is a perspective view showing an embodiment of a searcher according to the present invention.
FIG. 3 is a sectional view taken along line III-III in FIG. 1;
FIG. 4 is a perspective view showing a searcher after painting.
FIG. 5 is a graph showing the amount of energization with respect to the electrodeposition time.
FIG. 6 is a graph showing a relationship between an applied voltage and a film thickness.
FIG. 7 is a side view showing an example of an automobile body.
FIG. 8 is a sectional view taken along the line VIII-VIII in FIG. 7;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Searcher 11 ... Strip-shaped steel plate 12 ... PVC pipe (nonconductive pipe)
B: car body B1: body sill B2: body sill inner surface

Claims (5)

In a method for measuring the electrodeposition film thickness of an object to be electrodeposited on an actual line, the method comprises applying a searcher having an electrodeposition-turning property lower than the electrodeposition-turning property at a measurement target portion of the object to be coated. Set on the coating material, form an electrodeposition coating film on the searcher together with the object to be coated by the actual line , measure the thickness of the electrodeposition coating film formed on the searcher, and based on this film thickness, A method for measuring an electrodeposited film thickness, comprising determining an electrodeposited film thickness at a measurement target portion of an object to be coated. The method for measuring the thickness of an electrodeposited film according to claim 1, wherein the turnability with electrodeposition of the searcher is determined such that at least a non-electrodeposited portion is formed on the searcher. The electrodeposition film thickness according to claim 2, wherein an electrodeposition film thickness of a measurement target portion of the object to be coated is determined based on a length of an undeposited portion of the electrodeposition formed on the searcher. Measuring method. The said searcher, The strip | belt-shaped steel plate made into the substantially same electric potential as the said to-be-coated material, and the non-conductive pipe in which the said strip | belt-shaped steel plate is inserted, The Claims any one of Claims 1-3 characterized by the above-mentioned. Method for measuring electrodeposition film thickness. The method for measuring the thickness of an electrodeposited film according to any one of claims 1 to 4, wherein a measurement target portion of the object to be coated is an inner surface of a body sill.

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