JP2017203684A - Defect inspection device and defect inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a defect inspection device with which it is possible to detect a defect of a component with high accuracy.SOLUTION: A defect inspection device 1 comprises: a storage tank 16 capable of storing an electrolyte 8 flowing on the inner wall surface 911 of a membrane 91; electrodes 21, 22 electrically connectable to the membrane 91; a power supply 31 capable of applying voltage that is sufficient to electrolyze the electrolyte 8 to the electrodes 21, 22; a current detection unit 32 capable of detecting the magnitude of a current flowing in the electrode 21; a resistance calculating unit 33 for calculating the electric resistance of the membrane 91; and a flow velocity control unit 17 capable of controlling the flow velocity of the electrolyte 8 flowing on the inner wall surface 911. The resistance calculation unit 33 calculates the electric resistance of the membrane 91 when the electrolyte 8 is flowing on the inner wall surface 911 on the basis of the magnitude of a voltage applied to the electrodes 21, 22 by the power supply 31 and the magnitude of a current detected by the current detection unit 32. The flow velocity control unit 17 pours the electrolyte 8 at a flow velocity at which air bubbles sticking to the inner wall surface 911 can be separated from the inner wall surface 911.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a defect inspection apparatus and a defect inspection method for detecting a defect of a member.

  There is known a defect inspection apparatus capable of detecting a defect of a member by calculating an electric resistance of the member. For example, in Patent Document 1, a conductive liquid provided on both surfaces of a ceramic substrate to be inspected, an electrode capable of applying a voltage to the conductive liquid, and a voltage applied to the conductive liquid via the electrode A defect inspection apparatus including a current detection unit capable of detecting a current that sometimes flows in a conductive liquid is described.

JP 09-304324 A

In the defect inspection apparatus described in Patent Document 1, the electrical resistance of the ceramic substrate is calculated based on the voltage applied to the conductive liquid and the detected current. However, since the S / N ratio of the resistance change is small in the insulating film thinner than the ceramic substrate, it is difficult to detect a minute defect detected as a small change in electric resistance.
In order to increase the change in electrical resistance for the purpose of detecting minute defects, a method of increasing the applied voltage can be considered. However, when the applied voltage is increased, the conductive liquid may be electrolyzed. When the conductive liquid is electrolyzed, bubbles are generated in the conductive liquid. When bubbles are generated, the electric resistance changes, so that there is a possibility that a defect detection error may occur, and the defect detection accuracy decreases.

  An object of the present invention is to provide a defect inspection apparatus capable of detecting a defect of a member with high accuracy.

The present invention is a defect inspection apparatus for detecting a defect of a member formed of an insulating material, and includes a storage tank, a first electrode, a second electrode, a voltage application unit, a current detection unit, a resistance calculation unit, and And a flow rate control unit.
The voltage application unit is electrically connected to the first electrode that can be electrically connected to the member and the second electrode that can be electrically connected to the member at a position different from the first electrode. A voltage capable of electrolyzing the flowing conductive liquid can be applied to the first electrode and the second electrode.
The current detection unit can detect the magnitude of the current flowing through the first electrode.
The resistance calculation unit can calculate the electrical resistance of the member when the conductive liquid is flowing on the surface based on the magnitude of the voltage applied by the voltage application unit and the magnitude of the current detected by the current detection unit.
The flow rate control unit can control the flow rate of the conductive liquid flowing on the surface to a flow rate capable of separating bubbles attached to the surface from the surface.

In the defect inspection apparatus of the present invention, the conductive liquid is applied to the surface by detecting the magnitude of the current flowing through the first electrode when the voltage application unit applies a voltage to the first electrode and the second electrode. The electric resistance of the flowing member is calculated. At this time, since the voltage application unit applies a relatively high voltage such that the conductive liquid can be electrolyzed, bubbles may be generated and adhered to the surface near the defect. In the defect inspection apparatus of the present invention, the flow rate control unit can control the flow rate of the conductive liquid flowing on the surface to a flow rate at which bubbles can be separated from the surface. Thereby, since bubbles on the surface are removed, it is possible to prevent erroneous detection of defects due to the bubbles.
As described above, the defect inspection apparatus according to the present invention can detect a relatively small defect by applying a relatively high voltage capable of electrolyzing the conductive liquid, and can prevent a detection error due to a bubble. can do. Thereby, the defect of a member can be detected with high accuracy.

Further, the present invention is a defect inspection method for detecting a defect of a member formed of an insulating material, and includes a liquid flow process, a voltage application process, a current detection process, and a resistance calculation process.
In the liquid flowing step, a conductive liquid is flowed on the surface of the member.
In the voltage application step, the first electrode electrically connected to the member and the second electrode are controlled while controlling the flow rate of the conductive liquid flowing on the surface to be a flow rate capable of separating bubbles attached to the surface from the surface. A voltage capable of electrolyzing the conductive liquid is applied to the second electrode that is electrically connected to the member at a position different from the one electrode.
In the current detection step, the magnitude of the current flowing through the first electrode is detected.
In the resistance calculation step, the electric current of the member when the conductive liquid flows on the surface based on the magnitude of the voltage applied to the first electrode and the second electrode in the voltage application step and the magnitude of the current detected in the current detection step. Calculate the resistance.

  In the defect inspection method of the present invention, in the voltage application step, a voltage capable of electrolyzing the conductive liquid is applied to the first electrode and the second electrode. At this time, bubbles generated and attached to the surface in the vicinity of the defect due to electrolysis of the conductive liquid are removed by the conductive liquid that is controlled to have a flow rate at which the bubbles can be separated from the surface. Thereby, the detection mistake of the defect by a bubble can be prevented. Therefore, the defect inspection method of the present invention prevents detection errors due to bubbles while enabling detection of relatively small defects by applying a relatively high voltage capable of electrolyzing the conductive liquid. Therefore, the defect of the member can be detected with high accuracy.

It is a mimetic diagram of a defect inspection device by a first embodiment of the present invention. It is the II section enlarged view of FIG. It is a flowchart of the defect inspection method by 1st embodiment of this invention. It is a schematic diagram of the defect inspection apparatus by 2nd embodiment of this invention. It is a flowchart of the defect inspection method by 2nd embodiment of this invention. It is a flowchart of the defect inspection method by 3rd embodiment of this invention. It is a schematic diagram of the defect inspection apparatus by 4th embodiment of this invention. It is a flowchart of the defect inspection method by 4th embodiment of this invention.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
A defect inspection apparatus and a defect inspection method according to a first embodiment of the present invention will be described with reference to FIGS. The defect inspection apparatus 1 according to the first embodiment can detect defects in the film 91 as a “member” formed on the inner wall of an EGR cooler 90 provided in an engine system mounted on a vehicle or the like.

  The EGR cooler 90 is provided in an exhaust gas recirculation pipe that connects an intake system and an exhaust system included in the engine system. The exhaust gas recirculation pipe has a function of recirculating a part of the exhaust gas flowing through the exhaust system to the intake system as recirculated exhaust gas. Reflux exhaust is exhaust immediately after being exhausted by combustion in the engine, so it is not only relatively hot, but also contains chlorine ions, sulfate ions, nitrate ions, etc. in addition to water vapor, and is condensed and concentrated. It shows strong acidity. For this reason, the film 91 provided on the inner wall of the EGR cooler 90 is a ceramic having a relatively high corrosion resistance and heat resistance so that the EGR cooler 90 formed of stainless steel does not corrode under such environmental conditions where the reflux exhaust flows. Formed from material.

  The defect inspection apparatus 1 includes a support unit 10, an electrolyte solution supply unit 15, an electrode 21 as a “first electrode”, an electrode 22 as a “second electrode”, a control unit 30, and the like. The defect inspection apparatus 1 applies a voltage to the membrane 91 while flowing the electrolytic solution 8 as the “conductive liquid” on the inner wall surface 911 as the “surface” of the hollow cylindrical membrane 91. In the defect inspection apparatus 1, the defect of the film 91 is determined from the value of the electrical resistance calculated based on the relationship between the voltage applied to the film 91 and the current flowing through the electrode 21 when the electrolytic solution 8 flows through the inner wall surface 911. The presence or absence of the defect is inspected and the size of the defect is determined. FIG. 1 shows the defect inspection apparatus 1 in a state where the electrolytic solution 8 is flowing in the flow path 910 formed by the inner wall surface 911 of the film 91.

  The support unit 10 includes a support base 11 that can support the EGR cooler 90. The support part 10 has connection parts 12 and 13 that can be connected to two openings 92 and 93 of the EGR cooler 90. The connection port 120 included in the connection unit 12 is formed so as to communicate with the opening 920 included in the opening 92. The connection part 12 is connected to the electrolyte solution supply part 15 via the pipe 121. The connection port 130 included in the connection portion 13 is formed so as to be able to communicate with the opening 930 included in the opening portion 93. The connecting portion 13 is connected to a suction pump 19 capable of sucking the electrolytic solution 8 in the flow path 910 through a pipe 131.

  The electrolyte supply unit 15 includes a storage tank 16 and a flow rate control unit 17. The storage tank 16 is formed so as to be able to store the electrolyte 8 supplied to the flow path 910. The electrolytic solution 8 in the present embodiment is a mixture of water, an electrolyte, and ethanol as a “surfactant”, and its electric resistance is smaller than that of the ceramic material forming the film 91.

  The flow rate control unit 17 is provided between the storage tank 16 and the pipe 121. The flow rate control unit 17 is configured to be able to supply the electrolyte solution 8 in the storage tank 16 to the flow path 910 while controlling the flow rate of the electrolyte solution 8 on the inner wall surface 911.

  The electrode 21 is provided on the outer wall of the pipe 121 so as to be electrically connected to the membrane 91. The electrode 21 is electrically connected to the control unit 30. A part of the electrode 21 protrudes into the flow path 122 included in the pipe 121 (see FIG. 2).

  The electrode 22 is provided on the outer wall of the EGR cooler 90 so as to be electrically connected to the film 91. The electrode 22 is electrically connected to the control unit 30. Thus, when the electrolytic solution 8 is supplied to the flow path 910, the electrode 21 and the electrode 22 are electrically connected via the electrolytic solution 8 in the flow path 910.

The control unit 30 includes a power supply 31 as a “voltage application unit”, a current detection unit 32, and a resistance calculation unit 33.
The power source 31 is electrically connected to the electrodes 21 and 22. The power source 31 is formed so as to be able to apply to the electrodes 21 and 22 a DC voltage of a certain magnitude that can electrolyze the electrolytic solution 8.
The current detection unit 32 is provided in a current path that passes through the power supply 31, the electrode 21, the electrolytic solution 8 in the flow path 910, and the electrode 22. The current detector 32 can detect the current flowing through the electrode 21, that is, the magnitude of the current flowing through the power source 31, the electrode 21, the electrolytic solution 8 in the flow path 910, and the current path passing through the electrode 22.
The resistance calculator 33 can calculate the electrical resistance based on the magnitude of the voltage applied by the power supply 31 and the magnitude of the current detected by the current detector 32.

  The control unit 30 is electrically connected to the electrolytic solution supply unit 15 and the suction pump 19. The control unit 30 controls driving of the electrolytic solution supply unit 15 and the suction pump 19 in the inspection process in the defect inspection apparatus 1.

  Next, an inspection process of the film 91 as a “defect inspection method” according to the first embodiment will be described with reference to FIGS.

  First, in step (hereinafter simply referred to as “S”) 101, the EGR cooler 90 is attached to the defect inspection apparatus 1. In S101, the EGR cooler 90 in which the film 91 is formed on the inner wall is set on the support base 11, and the connection portion 12 and the opening portion 92, and the connection portion 13 and the opening portion 93 are connected.

  Next, in S <b> 102 as the “liquid flowing step”, the electrolytic solution 8 is supplied into the EGR cooler 90. In S <b> 102, the electrolyte solution 8 stored in the storage tank 16 is supplied to the flow path 910 by the flow rate control unit 17. Thereby, the electrolyte solution 8 flows along the inner wall surface 911. In S102, the electrolytic solution 8 supplied to the flow path 910 is sucked by the suction pump 19 via the pipe 131 while the electrolytic solution 8 is supplied to the flow path 910. As a result, bubbles generated when the electrolyte solution 8 is caused to flow through the membrane 91 in a dry state before the electrolyte solution 8 is supplied are removed from the flow path 910.

  Next, in S <b> 103 as the “voltage application step”, a voltage is applied to the electrodes 21 and 22 while flowing the electrolyte solution 8 at a predetermined flow rate. In S <b> 103, a voltage is applied to the electrodes 21 and 22 by the power supply 31. When a voltage is applied to the electrodes 21 and 22, a current path passing through the electrode 21, the electrolytic solution 8 flowing through the inner wall surface 911, and the electrode 22 is formed. At this time, as shown in FIG. 2, if the film 91 has a defect Df1 due to film formation failure or the like, the comparison is made by the electrode 21, the electrolytic solution 8 flowing through the inner wall surface 911, the electrolytic solution 8 in the defect Df1, and the electrode 22. A current path Ri1 in which the static current easily flows is formed.

  In step S103, a voltage is applied to the electrodes 21 and 22 such that the electrolytic solution 8 can be electrolyzed. As a result, the electrolytic solution 8 is electrolyzed, and bubbles Bb1 are generated on the inner wall surface 911 in the vicinity of the defect Df1, as shown in FIG. In S103, the electrolyte 8 flowing through the inner wall surface 911 flows at a predetermined flow rate (open arrow F1 in FIG. 2). Here, the “predetermined flow rate” is a flow rate when the acting force on the bubble Bb1 mainly due to the inertial force of the electrolytic solution 8 colliding with the bubble Bb1 becomes larger than the adhesion force between the bubble Bb1 and the film 91. As a result, the bubbles Bb1 adhering to the inner wall surface 911 are separated from the inner wall surface 911, and are discharged to the outside of the EGR cooler 90 along the flow of the electrolytic solution 8.

  Next, in S104 as the “current detection step”, the magnitude of the current is detected. In S <b> 104, the current detection unit 32 detects the value of the current flowing through the electrode 21 when a voltage to the extent that the electrolytic solution 8 can be electrolyzed is applied to the electrodes 21 and 22.

Next, in S105 as the “resistance calculation step”, the electric resistance is calculated. In S105, the resistance calculator 33 calculates the electrical resistance of the EGR cooler 90 when the electrolyte 8 is flowing in the flow path 910 based on the magnitude of the voltage applied in S103 and the magnitude of the current detected in S104. To do. At this time, if the calculated electrical resistance is larger than the reference value, it is determined that the film 91 has a defect having a size equal to or smaller than a specified value. If the calculated electrical resistance is smaller than the reference value, it is determined that the film 91 has a defect larger than the specified value.
Finally, in S106, the EGR cooler 90 is removed from the defect inspection apparatus 1.
In the inspection process of the film 91 according to the first embodiment, defects in the film 91 are detected in this way.

In the defect inspection apparatus 1 according to the present embodiment, when the power source 31 applies a voltage to the electrodes 21 and 22, the electrical resistance of the EGR cooler 90 in which the film 91 is formed by detecting the magnitude of the current flowing through the electrode 21. Is calculated. At this time, since the power supply 31 applies a relatively high voltage to the electrodes 21 and 22 so that the electrolytic solution 8 can be electrolyzed, bubbles due to the electrolysis of the electrolytic solution 8 are generated on the inner wall surface 911 near the defect Df1. In the defect inspection apparatus 1, the flow rate of the electrolytic solution 8 is controlled so that bubbles attached to the inner wall surface 911 can be separated from the inner wall surface 911. Thereby, since the bubbles adhering to the inner wall surface 911 are removed, it is possible to prevent the detection error of the defect due to the bubbles.
As described above, the defect inspection apparatus 1 can detect a relatively small defect by applying a relatively high voltage capable of electrolyzing the electrolytic solution 8 and can prevent a detection error of the defect due to the bubble. Can do. Thereby, the defect inspection apparatus 1 by 1st embodiment can detect the defect of the film | membrane 91 with high precision.

  In the present embodiment, the electrolytic solution 8 contains ethanol. Since the surface tension is lowered by mixing water and ethanol, the electrolytic solution 8 easily enters a minute defect. As a result, it is possible to reliably prevent detection of defects from being detected.

  In the inspection process of the film 91 according to the first embodiment, a voltage capable of electrolyzing the electrolytic solution 8 is applied to the electrodes 21 and 22 in S103. At this time, the bubbles Bb1 that are generated and adhered to the surface in the vicinity of the defect Df1 due to the electrolysis of the electrolyte solution 8 are removed by the electrolyte solution 8 that is controlled to have a flow velocity at which the bubble Bb1 can be separated from the inner wall surface 911. Thereby, the detection mistake of the defect by a bubble can be prevented. Therefore, the inspection process of the film 91 according to the first embodiment can prevent detection of defects due to bubbles while enabling detection of minute defects by applying a relatively high voltage capable of electrolyzing the electrolyte solution 8. Therefore, the defect of the member can be detected with high accuracy.

(Second embodiment)
Next, a defect inspection apparatus and a defect inspection method according to the second embodiment of the present invention will be described with reference to FIGS. The second embodiment is different from the first embodiment in that a pressure control unit capable of controlling the pressure of the electrolytic solution 8 is provided. In addition, the same code | symbol is attached | subjected to the site | part substantially the same as 1st embodiment, and description is abbreviate | omitted.

  The defect inspection apparatus 2 according to the second embodiment includes a support unit 10, an electrolyte solution supply unit 35, electrodes 21 and 22, a control unit 30, and the like.

The electrolyte supply unit 35 includes a storage tank 16, a flow rate control unit 17, and a pressure control unit 38.
The pressure control unit 38 is provided between the storage tank 16 and the flow rate control unit 17. The pressure control unit 38 can control the pressure of the electrolyte 8 supplied to the flow path 910.

  Next, an inspection process of the film 91 as a “defect inspection method” according to the second embodiment will be described with reference to FIGS.

  First, in S201, the EGR cooler 90 is attached to the defect inspection apparatus 2 in the same manner as in S101 in the first embodiment, and then in S202 as the “liquid flowing step”, in the same manner as in S102 in the first embodiment, EGR. The electrolyte solution 8 is supplied into the cooler 90.

  Next, in S <b> 203 as the “voltage application step”, a voltage is applied to the electrodes 21 and 22 while flowing the pressurized electrolyte 8 at a predetermined flow rate. In step S <b> 203, when a voltage is applied to the electrodes 21 and 22 by the power supply 31, the pressure control unit 38 supplies the electrolyte solution 8 to the flow path 910 while applying pressure. Thereby, the bubbles adhering to the inner wall surface 911 in the vicinity of the defect Df1 of the film 91 are separated from the inner wall surface 911 and are discharged to the outside of the EGR cooler 90 along the flow of the electrolyte solution 8.

Next, in S204 as the “current detection step”, the magnitude of the current is detected as in S104 of the first embodiment, and in S205 as the “resistance calculation step”, as in S105 of the first embodiment. Calculate the electrical resistance.
Finally, in S206, the EGR cooler 90 is removed from the defect inspection apparatus 2 as in S106 of the first embodiment.
In the inspection process for the film 91 according to the second embodiment, defects in the film 91 are detected in this way.

  The defect inspection apparatus 2 according to the present embodiment can supply the pressurized electrolyte 8 to the flow path 910. Thereby, since the size of the bubbles generated by the electrolysis of the electrolytic solution 8 becomes smaller than that in the first embodiment, the noise due to the bubbles in the calculated electric resistance becomes relatively small. Therefore, the second embodiment has the same effect as the first embodiment, and can detect even smaller defects.

(Third embodiment)
Next, a defect inspection method according to the third embodiment of the present invention will be described with reference to FIG. The third embodiment is different from the second embodiment in that the pressure control unit lowers the pressure of the electrolytic solution 8. In addition, the same code | symbol is attached | subjected to the site | part substantially the same as 2nd embodiment, and description is abbreviate | omitted.

  The defect inspection apparatus according to the third embodiment includes a support unit 10, an electrolyte supply unit 35, electrodes 21, 22 and a control unit 30. That is, the defect inspection apparatus according to the third embodiment has the same configuration as the defect inspection apparatus 2 according to the second embodiment.

An inspection process of the film 91 as a “defect inspection method” according to the third embodiment will be described with reference to FIG.
First, in S301, similar to S201 in the second embodiment, after the EGR cooler 90 is attached to the defect inspection apparatus according to the third embodiment, in S302 as the “liquid flowing step”, S202 of the second embodiment and Similarly, the electrolytic solution 8 is supplied into the EGR cooler 90.

  Next, in S303 as the “voltage application step”, a voltage is applied to the electrodes 21 and 22 while the decompressed electrolyte 8 is allowed to flow at a predetermined flow rate. In step S <b> 303, when a voltage is applied to the electrodes 21 and 22 by the power supply 31, the pressure control unit 38 supplies the electrolytic solution 8 to the flow path 910 while reducing the pressure to near the vapor pressure of the electrolytic solution 8. Thereby, the bubbles adhering to the inner wall surface 911 in the vicinity of the defect Df1 of the film 91 are separated from the inner wall surface 911 and discharged to the outside of the EGR cooler 90 by the flow of the electrolytic solution 8.

Next, in S304 as the “current detection step”, the magnitude of the current is detected as in S204 of the second embodiment, and in S305 as the “resistance calculation step”, as in S205 of the second embodiment. Calculate the electrical resistance.
Finally, in S306, as in S206 of the second embodiment, the EGR cooler 90 is removed from the defect inspection apparatus according to the third embodiment.
In the inspection process of the film 91 according to the third embodiment, defects in the film 91 are detected in this way.

  In the inspection process of the film 91 according to the present embodiment, the electrolytic solution 8 whose pressure has been reduced to near the vapor pressure is supplied to the flow path 910. Thereby, since the size of bubbles generated by electrolysis of the electrolytic solution 8 is larger than that in the first embodiment, the acting force on the bubbles due to the inertial force of the electrolytic solution 8 is larger than that in the first embodiment. Thereby, bubbles adhering to the inner wall surface 911 are easily separated from the inner wall surface 911. Therefore, the third embodiment has the same effect as the first embodiment, and can reliably prevent erroneous detection of defects due to bubbles.

  Further, in the inspection process of the film 91 according to the present embodiment, when the electrolyte solution 8 is decompressed, the gas dissolved in the electrolyte solution 8 can be degassed. Thereby, the volume of bubbles generated in the electrolyte 8 is reduced. Therefore, noise due to bubbles in the calculated electrical resistance is relatively small, and thus even smaller defects can be detected.

(Fourth embodiment)
Next, a defect inspection apparatus and defect inspection method according to a fourth embodiment of the present invention will be described with reference to FIGS. The fourth embodiment is different from the second embodiment in that it includes a deaeration processing unit. In addition, the same code | symbol is attached | subjected to the site | part substantially the same as 2nd embodiment, and description is abbreviate | omitted.

  The defect inspection apparatus 4 according to the fourth embodiment includes a support unit 10, an electrolyte supply unit 45, electrodes 21, 22 and a control unit 30.

The electrolyte supply unit 45 includes a storage tank 16, a flow rate control unit 17, and a deaeration processing unit 49.
The deaeration processing unit 49 is provided in the storage tank 16. The deaeration processing unit 49 can deaerate the electrolyte 8 stored in the storage tank 16 by heating, for example.

Next, an inspection process of the film 91 as a “defect inspection method” according to the fourth embodiment will be described with reference to FIGS.
First, in S401, the EGR cooler 90 is attached to the defect inspection apparatus 4 as in S101 of the first embodiment.

  Next, in S <b> 402 as “a degassing process step”, the electrolytic solution 8 stored in the storage tank 16 is degassed. In S <b> 402, the gas dissolved in the electrolytic solution 8 is removed from the electrolytic solution 8 by heating the electrolytic solution 8. Note that S402 may be performed before S401 or may be performed in parallel with S401.

Next, in S403 as the “liquid flowing step”, the electrolytic solution 8 is supplied into the EGR cooler 90 as in S102 of the first embodiment.
Next, in S404 as the “voltage application step”, similarly to S103 in the first embodiment, a voltage is applied to the electrodes 21 and 22 while flowing the electrolyte 8 at a predetermined flow rate, and the “current detection step” is performed. In S405, the magnitude of the current is detected as in S104 of the first embodiment.
Next, in S406 as the “resistance calculation step”, the electrical resistance is calculated as in S105 of the first embodiment, and in S407, the EGR cooler 90 is connected to the defect inspection apparatus 4 as in S106 of the first embodiment. Remove from.
In the inspection process of the film 91 according to the fourth embodiment, defects in the film 91 are detected in this way.

  The defect inspection apparatus 4 according to the present embodiment can deaerate the electrolytic solution 8 stored in the storage tank 16. Thereby, since the gas dissolved in the electrolyte solution 8 decreases, the amount of bubbles generated by the dissolved gas decreases. Therefore, the fourth embodiment has the same effect as the first embodiment, and can reliably prevent a detection error due to bubbles.

(Other embodiments)
In the above-described embodiment, the defect inspection apparatus can detect a defect of a hollow cylindrical film as a “member” formed on the inner wall of the EGR cooler. However, the “member” that the defect inspection apparatus can detect a defect is not limited to this. What is necessary is just to be formed from the insulating material with large resistance compared with the electroconductive liquid which flows on the surface. Therefore, it does not have to be a hollow cylindrical member as in the above-described embodiment.

  In the above-described embodiment, the electrolytic solution as the “conductive liquid” is a mixture of water, an electrolyte, and ethanol as the “surfactant”. However, the conductive liquid is not limited to this. Any liquid may be used as long as it is easier to conduct electricity than the member. Further, the surfactant may not be contained.

  One of the two electrodes described above is provided in a pipe connecting the electrolyte supply unit and the EGR cooler. However, the two electrodes may be provided so as to be electrically connected to the membrane at different positions.

  In the third embodiment, the pressure controller supplies the flow path while reducing the electrolyte solution to near the vapor pressure of the electrolyte solution. However, the degree of pressure reduction of the electrolyte controlled by the pressure control unit is not limited to this. It only needs to be higher than the vapor pressure of the electrolyte.

  The defect inspection apparatus according to the fourth embodiment may include a pressure control unit included in the defect inspection apparatus according to the second and third embodiments.

  In the above-described embodiment, the voltage application unit applies a constant DC voltage to the two electrodes. However, the magnitude and time change of the voltage applied to the two electrodes by the voltage application unit are not limited to this. For example, the voltage may be gradually increased, and the state of the defect may be determined from a change in current with respect to the changing voltage. Moreover, you may determine the state of a defect by applying an alternating voltage.

  In the above-described embodiment, the current detection unit detects the current flowing through the electrode 21 as the “first electrode”. However, the current flowing through the electrode 22 may be detected using the electrode 22 as the “first electrode”. That is, the electrode 21 and the electrode 22 differ only in the positions provided with respect to the film 91, and the electrode 21 may be a “first electrode” or a “second electrode”. Also good.

  As mentioned above, this invention is not limited to such embodiment, It can implement with a various form in the range which does not deviate from the summary.

1, 2, 4 ... Defect inspection device 8 ... Electrolyte (conductive liquid)
17 ... Flow rate control unit 21 ... Electrode (first electrode)
22 ... Electrode (second electrode)
31 ... Power supply (voltage application unit)
32 ... Current detection part 33 ... Resistance calculation part 91 ... Membrane (member)
911 ... Inner wall surface (surface)

Claims (10)

A defect inspection apparatus for detecting a defect of a member (91) formed of an insulating material,
A storage tank (16) capable of storing the conductive liquid (8) flowing on the surface (911) of the member;
A first electrode (21) electrically connectable to the member;
A second electrode (22) electrically connectable to the member at a position different from the first electrode;
A voltage application that is electrically connected to the first electrode and the second electrode and that can apply a voltage capable of electrolyzing the conductive liquid flowing on the surface to the first electrode and the second electrode. Part (31);
A current detector (32) capable of detecting the magnitude of the current flowing through the first electrode;
A resistance calculation unit capable of calculating the electrical resistance of the member when the conductive liquid is flowing on the surface based on the magnitude of the voltage applied by the voltage application unit and the magnitude of the current detected by the current detection unit (33)
A flow rate controller (17) capable of controlling the flow rate of the conductive liquid flowing on the surface to a flow rate capable of separating the bubbles (Bb1) attached to the surface from the surface;
A defect inspection apparatus comprising:   The defect inspection apparatus according to claim 1, further comprising a pressure control unit (38) capable of controlling a pressure of the conductive liquid flowing on the surface.   The defect inspection apparatus according to claim 2, wherein the pressure control unit can reduce the pressure of the conductive liquid to near the vapor pressure of the conductive liquid.   The defect inspection apparatus according to claim 1, wherein the conductive liquid includes a surfactant.   The defect inspection apparatus as described in any one of Claims 1-4 further equipped with the deaeration process part (49) which can deaerate the said conductive liquid before flowing through the said surface. A defect inspection method for detecting a defect of a member (91) formed of an insulating material,
A liquid flow step of flowing a conductive liquid (8) over the surface (911) of the member;
A first electrode that is electrically connected to the member while controlling the flow rate of the conductive liquid flowing on the surface to a flow rate at which bubbles (Bb1) adhering to the surface can be separated from the surface ( 21) and a voltage applying step of applying a voltage capable of electrolyzing the conductive liquid to the second electrode (22) electrically connected to the member at a position different from the first electrode;
A current detection step of detecting the magnitude of the current flowing through the first electrode;
Based on the magnitude of the voltage applied to the first electrode and the second electrode in the voltage application step and the magnitude of the current flowing through the first electrode detected in the current detection step, the conductive material is applied to the surface. A resistance calculating step of calculating the electrical resistance of the member when the ionic liquid is flowing;
Including defect inspection method.   The defect inspection method according to claim 6, wherein, in the voltage application step, a voltage is applied to the first electrode and the second electrode while flowing the reduced conductive liquid on the surface.   The defect inspection method according to claim 7, wherein in the voltage application step, the pressure of the conductive liquid flowing on the surface is reduced to near the vapor pressure of the conductive liquid.   The defect inspection method according to claim 6, wherein in the voltage application step, a voltage is applied to the first electrode and the second electrode while flowing the pressurized conductive liquid on the surface.   The defect inspection method according to any one of claims 6 to 9, further comprising a deaeration process step of degassing the conductive liquid before flowing on the surface before the liquid flow step.

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