JP5768502B2 - Corrosion detection system for fluid flow components - Google Patents

Description

  The present invention relates to a corrosion detection system for a fluid circulation member mounted on a vehicle, and more particularly to a fluid circulation member caused by condensed water generated in an EGR cooler or an intercooler of an EGR (Exhaust Gas Recirculation) system of an internal combustion engine. The present invention relates to a corrosion detection system for a fluid circulation member that detects the strength and degree of corrosion.

  Along with the increasing demand for exhaust purification performance of internal combustion engines for vehicles, internal combustion engines equipped with an EGR system that performs exhaust gas recirculation that is effective in reducing NOx have become widespread. In recent years, as an effect of the EGR system, attention has been focused on improving fuel efficiency by reducing pumping loss in addition to NOx reduction.

  In the EGR system, when a large amount of high-temperature EGR gas is mixed into the intake air, there is a possibility that the intake charging efficiency is lowered and the output of the internal combustion engine is reduced. For this reason, EGR coolers that reduce the temperature of the recirculated exhaust gas are frequently used.

  The EGR cooler is generally configured by providing a stainless steel cooling pipe in a case. Then, the exhaust gas recirculated through the exhaust pipe is circulated inside the cooling pipe, and the cooling water is circulated outside the cooling pipe. Then, heat exchange is performed between the exhaust gas and the cooling water through the wall portion of the cooling pipe, whereby the exhaust gas recirculated to the intake side is cooled.

The exhaust gas contains a lot of water vapor (H ₂ O) and carbon dioxide gas (CO ₂ ), and also contains sulfurous acid gas (SO ₂ ), nitrogen oxides (NO _x ), and the like. When the high-temperature exhaust gas is cooled in the cooling pipe, the water vapor in the exhaust gas may be condensed to become condensed water and adhere to the inner wall portion of the cooling pipe.

When sulfurous acid gas is dissolved in the condensed water adhering to the inner wall, sulfuric acid (H ₂ SO ₄ ) and sulfuric anhydride (SO ₃ ) are generated. Alternatively, when nitrogen oxides are dissolved in condensed water, nitric acid (NHO ₃ ) is generated.

Further, although gasoline (Cl ₂ ) is not included in principle as a fuel for an internal combustion engine, gasoline may contain chlorine depending on the country or region. Engine oil and air contain chlorine. For this reason, gasoline, engine oil, and atmospheric chlorine remain in the exhaust gas in the combustion chamber of the internal combustion engine, which may contain chlorine in the exhaust gas. When chlorine in the exhaust gas is dissolved in the condensed water in the EGR cooler, hydrochloric acid (HCl) is generated.

  The strongly acidic condensate such as sulfuric acid, nitric acid and hydrochloric acid adheres to the inner wall portion of the cooling pipe, which may corrode the inner wall portion of the cooling pipe.

  In order to prevent corrosion of the cooling pipe, a system for detecting the degree of corrosion of the inner wall of the cooling pipe has been developed (see, for example, Patent Document 1). In this corrosion detection system, the inner wall portion of the cooling pipe is formed by a laminated structure of a core material and a covering material. And the coating | covering material is provided so that exhaust gas may be contacted. In addition, a potentiometer for measuring a potential difference between the covering material and the core material is installed.

  When the exhaust gas is cooled and acidic condensed water is generated and adheres to the coating material, the coating material may be corroded. In this case, the potential difference between the coating material and the core material is reduced by thinning the coating material due to corrosion. By detecting this decrease in potential difference with a potentiometer, corrosion of the coating material can be detected.

  Further, when the measured potential difference becomes smaller than a preset threshold value, it is determined that the corrosion of the covering material has reached a predetermined level, and a warning is issued to the driver. This makes it possible to take measures such as replacing the cooling pipe before the corrosion progresses greatly.

JP 2009-185673 A

  However, in the conventional corrosion detection system as described above, the potential difference between the coating material and the core material is measured, and the potential difference between the coating material and the core material is independent of the presence or absence of condensed water at the time of measurement. It is determined. For this reason, in the conventional corrosion detection system, although the degree of corrosion of the coating material at the time of measurement can be detected, it is difficult to detect the strength of corrosion by the condensate at the time of measurement. For this reason, even if corrosion progresses rapidly, for example, when strongly acidic condensate is generated, the driver is not warned unless corroded to a preset level, and the driver cannot be warned early. There was a problem.

  Further, considering that the corrosion of the cooling pipe proceeds rapidly due to the strongly acidic condensate having a high corrosion strength, it is preferable that the warning be issued early. However, if the warning is set to be issued early, if the corrosion of the cooling pipe progresses slowly due to the condensed water with low corrosion strength, it can be used for a long period of time, but it will be dealt with earlier than necessary. There was also the problem of becoming.

  The present invention has been made to solve the above-described conventional problems, and detects the strength of corrosion of condensed water generated in a fluid circulation member such as a cooling pipe of an EGR cooler or a cooling pipe of an intercooler. An object of the present invention is to provide a corrosion detection system for a fluid flow member.

  In order to achieve the above object, the corrosion detection system for a fluid circulation member of an internal combustion engine according to the present invention is (1) provided inside an electrically conductive fluid circulation member that circulates exhaust gas or intake gas of the internal combustion engine. A first conductive member made of the same material as the fluid flow member, a second conductive member made of a material having a different ionization tendency from the fluid flow member, the first conductive member, and the second conductive material A sensor unit comprising an insulating means for insulating the members from each other, and the condensed water generated inside adheres across the first conductive member and the second conductive member, so that the first A current measurement unit that measures a current flowing between the conductive member and the second conductive member, and the current value obtained by the current measurement unit exceeds a preset current threshold, or the current value On condition that the integrated value exceeds the cumulative threshold set in advance, characterized in that the inner wall portion of the fluid flow member is provided with a determination unit that determines that the corrosive environment by the condensed water.

  With this configuration, when the exhaust gas or the suction gas is cooled inside the fluid circulation member to generate acidic condensed water, and the condensed water adheres across the first conductive member and the second conductive member A current flows between the first conductive member and the second conductive member. Here, as a form in which the condensed water adheres across the first conductive member and the second conductive member, the first conductive member and the second conductive member are in the form of water droplets of condensed water as a liquid. As a matter of course, it also includes the case where mist-like condensed water comes into contact with the first conductive member and the second conductive member as water vapor and conducts.

  And the electric current which flowed between the 1st electroconductive member and the 2nd electroconductive member is measured by an electric current measurement part, and an electric current value is obtained. When the obtained current value exceeds a preset current threshold value, the determination unit determines that the strength of the condensed water corrosion is greater than a predetermined threshold value. Further, when the integrated value of the measured current value exceeds a preset integration threshold, the determination unit determines that the corrosion of the inner wall portion by the condensed water is greater than a predetermined degree. The determination unit determines whether or not the inner wall portion is easily corroded by the condensed water from the strength of corrosion of the condensed water or the degree of corrosion of the inner wall portion.

  As a result, the current measuring unit detects the current between the first conductive member and the second conductive member that accompanies the adhesion of the generated condensed water, so that the corrosion strength of the condensed water or the inner wall portion The determination unit can detect the degree of corrosion. For this reason, it is possible to detect with higher accuracy whether or not the inner wall portion is easily corroded by the condensed water as compared with the case where only the degree of corrosion of the inner wall portion is detected as in the prior art.

  In the fluid flow member corrosion detection system according to (1) above, (2) the first conductive member is preferably the inner wall portion. With this configuration, the first conductive member can also be used as the inner wall portion that is the object of corrosion detection, so the first conductive member can be placed in an actual corrosive environment. As a result, the number of parts can be reduced and detection with higher accuracy is possible.

  In the fluid flow member corrosion detection system according to the above (1) or (2), (3) the material of the second conductive member is less ionized than the material of the first conductive member. It is preferable.

  With this configuration, when acidic condensed water straddles and contacts the first conductive member and the second conductive member, the first conductive member having a large ionization tendency dissolves in the condensed water and has an ionization tendency. The second conductive member having a small size does not dissolve in the condensed water. For this reason, the first conductive member made of the same material as the inner wall portion is corroded, and the current value generated thereby is measured, so that the corrosion of the inner wall portion can be detected with higher accuracy. .

  In the fluid flow member corrosion detection system according to the above (1) to (3), (4) on the condition that the determination unit has determined that the inner wall portion is in an environment susceptible to corrosion by the condensed water, It is preferable to have a warning part that warns that the inner wall part is in an environment susceptible to corrosion by the condensed water.

  With this configuration, when the warning unit issues a warning, the user of the internal combustion engine can recognize that the inner wall portion is in an environment that is susceptible to corrosion. For this reason, for example, when the internal combustion engine is an engine mounted on a vehicle, an appropriate measure can be taken, such as a user bringing the vehicle into a repair shop.

  In the corrosion detection system for a fluid circulation member according to (1) to (4) above, (5) on the condition that the determination unit has determined that the inner wall portion is in an environment that is easily corroded by the condensed water, It is preferable to have an avoidance processing unit that performs processing to avoid the inner wall portion from being in an environment that is easily corroded by the condensed water. With this configuration, since the avoidance processing unit performs the avoidance processing, it is possible to escape from an environment in which the inner wall portion is easily corroded by condensed water.

  In the corrosion detection system for a fluid circulation member according to (5) above, (6) the avoidance processing unit is preferably a heating unit that heats the condensed water. With this configuration, since the heating unit heats the condensed water on the condition that the determining unit determines that the inner wall portion is easily corroded by the condensed water, the condensed water evaporates and corrosion of the inner wall portion is prevented. Alternatively, when chlorine is contained in the condensed water, chlorine is vaporized from the condensed water, and the strength of corrosion of the condensed water is reduced. Thereby, it can escape from the environment where an inner wall part is easy to corrode with condensed water.

  In the corrosion detection system for a fluid circulation member according to (1) to (6) above, (7) the fluid circulation member is preferably a pipe member that circulates the exhaust gas provided in an EGR cooler. With this configuration, it is determined whether the inner wall portion of the pipe member through which the exhaust gas of the EGR cooler is easily corroded by condensed water.

  According to the present invention, the inner wall portion of the fluid circulation member is condensed on the condition that the measured current value exceeds a preset current threshold value or the integrated value of the current values exceeds a preset integration threshold value. Corresponding to the fluid circulation member that can detect the strength of the corrosion of the condensed water generated in the fluid circulation member such as the cooling pipe of the EGR cooler because it is provided with a judgment unit that judges that the environment is easily corroded by water. A detection system can be provided.

It is the schematic which shows the internal combustion engine by which the corrosion detection system of the fluid circulation member which concerns on embodiment of this invention is mounted. It is a longitudinal cross-sectional view which shows the EGR cooler with which the corrosion detection system of the fluid distribution member which concerns on embodiment of this invention was mounted | worn. It is the schematic which shows the principal part of the corrosion detection system of the fluid distribution | circulation member which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the corrosion detection system of the fluid distribution | circulation member which concerns on embodiment of this invention. It is a graph which shows the change of the electric current value in the corrosion detection system of the fluid distribution | circulation member which concerns on embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a fluid flow member corrosion detection system of the present invention will be described with reference to the drawings. In the present embodiment, the corrosion detection system for a fluid circulation member detects the strength and degree of corrosion caused by condensed water generated in an EGR cooler of an EGR system of an internal combustion engine mounted on a vehicle.

  First, the configuration of an internal combustion engine (hereinafter simply referred to as an engine) according to the present embodiment will be described. The engine of the present embodiment is constituted by a four-cycle gasoline engine that performs a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while the piston reciprocates twice.

  As shown in FIG. 1, the engine 1 includes an engine body 2, an intake device 3, an exhaust device 4, and an EGR system 5.

  The engine body 2 includes a plurality of cylinders (not shown) and a water jacket (not shown). The water jacket is provided around each cylinder, and cools the engine body 2 by circulating cooling water 20 therein.

  The intake device 3 includes an intake pipe 30, an air cleaner 31, a throttle valve 32, and an intake manifold 33. The air cleaner 31 purifies the intake air with a filter. The throttle valve 32 is provided downstream of the intake pipe 30 and adjusts the intake air amount of the intake air supplied to each cylinder by an electronic control method.

  The intake manifold 33 connects the intake pipe 30 and each cylinder. The intake air flows from the intake pipe 30 through the air cleaner 31 and the intake manifold 33 into each cylinder. Further, the engine body 2 and the intake device 3 are connected by the connection of the intake manifold 33 and each cylinder.

  The exhaust device 4 is configured by sequentially connecting an exhaust manifold 40, a catalytic converter 41, an exhaust pipe 42, an exhaust muffler 43, and a tail pipe 44.

  The exhaust manifold 40 circulates the exhaust gas 45 exhausted from each cylinder. The engine body 2 and the exhaust device 4 are connected by connecting the exhaust manifold 40 and each cylinder.

The catalytic converter 41 includes a three-way catalyst composed of an oxidation catalyst, a reduction catalyst, and a promoter. For example, the catalytic converter 41 reduces NOx of the exhaust gas 45 to NO ₂ or NO and further reacts with hydrocarbons or carbon monoxide to form nitrogen gas, or converts the hydrocarbons or carbon monoxide of the exhaust gas 45 into nitrogen gas. It can be oxidized to water or carbon dioxide. Thus, the catalytic converter 41 purifies harmful substances such as carbon monoxide, nitrogen oxides, and hydrocarbons of the exhaust gas 45.

  The exhaust muffler 43 includes a variable valve (not shown) that can adjust the passage area of the exhaust gas 45 by the pressure of the exhaust gas 45. The variable valve is closed when idling or when the engine 1 is running at a low speed, and the passage of the exhaust gas 45 is reduced to enhance the silencing effect. The variable valve is opened when the engine 1 is rotating at a high speed, and the passage of the exhaust gas 45 is enlarged to lower the back pressure and increase the exhaust efficiency.

  The downstream end of the tail pipe 44 is open to the atmosphere. For this reason, the exhaust gas 45 discharged from the exhaust muffler 43 is discharged to the atmosphere via the tail pipe 44.

  The EGR system 5 includes an upstream pipe 50, an EGR cooler 51, a corrosion detection system 52, an intermediate pipe 53, an EGR valve 54, and a downstream pipe 55. The upstream pipe 50, the EGR cooler 51, the intermediate pipe 53, the EGR valve 54, and the downstream pipe 55 are connected in order.

  The upstream pipe 50 is connected to the exhaust pipe 42 of the exhaust device 4. Further, the downstream pipe 55 is connected to the intake manifold 33 of the intake device 3. That is, the EGR system 5 functions as an exhaust gas recirculation device that recirculates a part of the exhaust gas 45 of the exhaust device 4 to the intake device 3.

  As shown in FIG. 2, the EGR cooler 51 includes a case 60, a cooling medium inflow pipe 61, a cooling medium outflow pipe 62, an exhaust gas cooling pipe 63, an exhaust gas inflow pipe 64 as a fluid circulation member and a pipe member. And an exhaust gas outflow pipe 65. As the cooling medium, the cooling water 20 of the engine 1 is used.

  The EGR cooler 51 is provided so as to be inclined so that the exhaust gas outflow pipe 65 is positioned above the exhaust gas inflow pipe 64. In the present embodiment, an inclination angle θ is inclined with respect to the horizontal line H. The inclination angle θ is appropriately set according to the vehicle type.

  The case 60 includes a substantially cylindrical case body 70, an upstream support plate 71, and a downstream support plate 72. Inside the case main body 70, the cooling water 20 flows along the axial direction (indicated by white arrowheads in FIG. 2).

  The upstream support plate 71 is provided at the end of the case body 70 on the upstream side in the flow direction of the cooling water 20 so as to close the end. The upstream support plate 71 has a plurality of through holes 71a. The downstream support plate 72 is provided at the end of the case body 70 on the downstream side in the flow direction of the cooling water 20 so as to close the end. The downstream support plate 72 has a plurality of through holes 72a. The same number of through-holes 71a in the upstream support plate 71 and the through-holes 72a in the downstream support plate 72 are provided at positions facing each other across the case main body 70.

  The exhaust gas cooling pipe 63 is made of stainless steel, and includes an upstream end 73, a downstream end 74, and a wall 75. The exhaust gas cooling pipe 63 allows the exhaust gas 45 to flow (indicated by a black arrowhead in FIG. 2). The exhaust gas cooling pipe 63 is passed through the through hole 71 a of the pair of upstream support plates 71 and the through hole 72 a of the downstream support plate 72 that face each other. The upstream end 73 is press-fitted into the through hole 71 a of the upstream support plate 71 and is supported by the upstream support plate 71. The exhaust gas 45 is supplied from the exhaust gas inflow pipe 64 to the upstream end 73. The downstream end 74 is press-fitted into the through hole 72 a of the downstream support plate 72 and supported by the downstream support plate 72. The exhaust gas 45 is discharged from the downstream end 74 to the exhaust gas outflow pipe 65.

  The wall 75 is provided between the upstream end 73 and the downstream end 74 and is formed in an annular shape extending in the direction in which the exhaust gas 45 is circulated. In the exhaust gas cooling pipe 63, the exhaust gas 45 flowing inside is cooled by heat exchange with the cooling water 20 flowing outside. Further, when the exhaust gas 45 is cooled inside the exhaust gas cooling pipe 63, the condensed water 21 may be generated inside the exhaust gas cooling pipe 63. Since the EGR cooler 51 is provided with the exhaust gas outflow pipe 65 inclined so as to be positioned above the exhaust gas inflow pipe 64, the condensed water 21 generated inside the exhaust gas cooling pipe 63 is removed from the exhaust gas inflow pipe 63. It flows in the direction of 64.

  The cooling medium inflow pipe 61 is provided in the lower part of the case body 70 near the upstream end in the flow direction of the cooling water 20. The cooling medium inflow pipe 61 allows the cooling water 20 to flow into the case 60. The upstream end of the cooling medium inflow pipe 61 is connected to the cooling medium supply pipe 76. An upstream end of the cooling medium supply pipe 76 is connected to a supply pump (not shown) of the cooling water 20 through a water jacket of the engine body 2.

  The cooling medium outflow pipe 62 is attached to the upper portion of the case body 70 near the downstream end in the flow direction of the cooling water 20. The cooling medium outflow pipe 62 allows the cooling water 20 to flow out from the case 60. The downstream end of the cooling medium outlet pipe 62 is connected to the cooling medium discharge pipe 77. The downstream end of the cooling medium discharge pipe 77 is connected to, for example, a radiator (not shown).

  The exhaust gas inflow pipe 64 is made of stainless steel, is attached to an upstream end of the case main body 70 in the flow direction of the exhaust gas 45, and is connected to the exhaust gas cooling pipe 63. The upstream end of the exhaust gas inflow pipe 64 is connected to the upstream pipe 50. The upstream end of the exhaust gas inflow pipe 64 is formed to be thinner than the downstream end of the exhaust gas inflow pipe 64. Thereby, the condensed water 21 flowing from the exhaust gas cooling pipe 63 is stored in the lower part of the exhaust gas inflow pipe 64 without flowing into the upstream pipe 50.

  The exhaust gas outflow pipe 65 is made of stainless steel, is attached to an end portion of the case body 70 on the downstream side in the flow direction of the exhaust gas 45, and is connected to the exhaust gas cooling pipe 63. The downstream end of the exhaust gas outflow pipe 65 is connected to the intermediate pipe 53.

  As shown in FIG. 3, the corrosion detection system 52 includes a sensor unit 80, a current measurement unit 81, an ECU (Electronic Control Unit) 82, and a warning unit 83. As shown in FIG. 2, the sensor portion 80 is provided on the inner wall portion 64 a below the exhaust gas inflow pipe 64, and includes a first conductive member 90, a second conductive member 91, and an insulating means 92. It is comprised including.

  The first conductive member 90 includes an inner wall portion 64 a of the exhaust gas inflow pipe 64. That is, the first conductive member 90 is made of stainless steel made of the same material as the exhaust gas inflow pipe 64. The insulating means 92 is made of a substantially square rubber sheet having a side of about 10 mm. The insulating means 92 is fixed to the inner wall portion 64a below the exhaust gas inflow pipe 64 by adhesion. The insulating means 92 insulates the first conductive member 90 and the second conductive member 91 from each other.

  The second conductive member 91 is made of a substantially square silver (Ag) plate material having a side of about 8 mm. Here, since the first conductive member 90 is made of stainless steel and the second conductive member 91 is made of silver, the ionization tendency of the first conductive member 90 is the ionization of the second conductive member 91. Greater than the trend.

  As shown in FIG. 3, the current measuring unit 81 is connected to the first conductive member 90 and the second conductive member 91. Here, the acidic condensate 21 generated inside the EGR cooler 51 adheres across the first conductive member 90 and the second conductive member 91, and the current measuring unit 81 is the first conductive member. By conducting the current 90 and the second conductive member 91, a current flows between the first conductive member 90 and the second conductive member 91.

At this time, chemical changes that occur between the first conductive member 90 and the condensed water 21 are as follows.
Fe → Fe ²⁺ + 2e ⁻

Moreover, the chemical change which arises between the 2nd electroconductive member 91 and the condensed water 21 is as follows.
2H ⁺ + 2e ⁻ → H ₂ ↑

  Furthermore, since the current measuring unit 81 connects the first conductive member 90 and the second conductive member 91, electrons pass through the current measuring unit 81. The current measuring unit 81 measures the current flowing between the first conductive member 90 and the second conductive member 91 by measuring electrons passing through the current measuring unit 81.

  The ECU 82 includes a determination unit 82a. The determination unit 82a acquires the current value obtained by the current measurement unit 81 and calculates the integrated value by integrating the current value. The determination unit 82a sets a current threshold value and an integration threshold value in advance. The current threshold value and the integration threshold value are set in consideration of the corrosion resistance of the exhaust gas inflow pipe 64 and the exhaust gas cooling pipe 63 with which the condensed water 21 can come into contact.

  When the current value obtained by the current measurement unit 81 exceeds the current threshold value, the determination unit 82a has a large number of electrons flowing instantaneously through the sensor unit 80, so is the acidity of the condensed water 21 high? Alternatively, it is determined that a large amount of condensed water 21 is generated. As a result, it is determined that the inner wall portion 64 a of the exhaust gas inflow pipe 64 is in an environment that is easily corroded by the condensed water 21.

  In addition, when the integrated value of the current values obtained by the current measuring unit 81 exceeds the integration threshold, the determination unit 82a has a large number of electrons flowing in the sensor unit 80, and therefore, for a long period of time. It is determined that condensed water 21 is generated. As a result, it is determined that the inner wall portion 64 a of the exhaust gas inflow pipe 64 is in an environment that is easily corroded by the condensed water 21.

  The warning unit 83 includes a warning lamp provided on the instrument panel. When determining that the inner wall portion 64a of the exhaust gas inflow pipe 64 is in an environment that is easily corroded by the condensed water 21, the determining portion 82a causes the warning portion 83 to emit light. The driver is warned that the inner wall 64a of the exhaust gas inflow pipe 64 is easily corroded by the condensed water 21 by the light emitted from the warning section 83.

  As shown in FIG. 1, the EGR valve 54 includes a stepping motor 54a and a valve main body (not shown). The valve body is opened and closed by driving a stepping motor 54a. The opening degree of the EGR valve 54 is adjusted according to the number of rotation steps of the stepping motor 54a, and the flow rate of the exhaust gas 45 from the exhaust pipe 42 to the intake pipe 30 is adjusted. The adjustment of the flow rate of the exhaust gas 45 in the EGR valve 54 is determined by a map based on the engine speed and the engine load factor.

  The ECU 82 is rewritable with a central processing unit (CPU) as a central processing unit, a ROM (Read Only Memory) that stores fixed data, and a RAM (Random Access Memory) that temporarily stores data An EEPROM (Electrically Erasable and Programmable Read Only Memory) composed of a non-volatile memory and an input / output interface circuit are included.

  Next, the operation of the fluid flow member corrosion detection system 52 in the present embodiment will be described with reference to the flowchart shown in FIG. This flowchart represents the execution contents of the operation program of the fluid flow member corrosion detection system 52 executed by the CPU of the ECU 82 using the RAM as a work area. The fluid flow member corrosion detection system 52 can be executed as long as the corrosion detection system 52 is energized and operated, and can be executed not only while the engine 1 is operating but also when the engine 1 is stopped. Yes.

  When the process is started, the ECU 82 operates the current measuring unit 81, and the current measuring unit 81 measures the current between the first conductive member 90 and the second conductive member 91 (step S1). Here, the acidic condensed water 21 adheres across the first conductive member 90 and the second conductive member 91, so that the gap between the first conductive member 90 and the second conductive member 91 is reached. Current flows. The current flowing between the first conductive member 90 and the second conductive member 91 is measured by the current measuring unit 81. The current value obtained by the current measurement unit 81 is transmitted to the determination unit 82a of the ECU 82.

  The determination unit 82a compares the current value with a preset current threshold value (step S2). When the determination unit 82a determines that the current value exceeds the current threshold (step S2; YES), it is determined that the acidity of the condensed water 21 is high or a large amount of the condensed water 21 is generated. Is done.

  As a result, the determination unit 82a determines that the inner wall portion 64a of the exhaust gas inflow pipe 64 is in an environment that is easily corroded by the condensed water 21, and causes the warning unit 83 to issue a warning (step S3). Specifically, the determination unit 82a turns on a warning lamp on the instruments panel. The driver who has confirmed the warning of the warning unit 83 can quickly bring the vehicle to a dealer or a repair shop, receive an inspection, and replace the fuel or replace the EGR cooler 51 as necessary.

  When the determination unit 82a determines that the current value does not exceed the current threshold (step S2; NO), the determination unit 82a compares the integrated value of the current value with a preset integration threshold (step S4). ). When the determination unit 82a determines that the integrated value exceeds the integration threshold (step S4; YES), it is determined that condensed water 21 has been generated over a long period of time. As a result, the determination unit 82a determines that the inner wall portion 64a of the exhaust gas inflow pipe 64 is in an environment that is easily corroded by the condensed water 21, and causes the warning unit 83 to issue a warning (step S3). Specifically, the determination unit 82a turns on a warning lamp on the instruments panel.

  When the determination unit 82a determines that the integrated value does not exceed the integration threshold (step S4; NO), or after the warning unit 83 issues a warning (step S3), the processing is terminated, and if necessary. The process is performed again.

  As described above, according to the corrosion detecting system 52 for a fluid circulation member according to the present embodiment, it is generated between the first conductive member 90 and the second conductive member 91 due to the adhesion of the condensed water 21. The current measuring unit 81 detects the current. And the judgment part 82a judges the strength of the corrosion of the condensed water 21 from the obtained electric current value, and the corrosion of the inner wall part 64a of the exhaust gas inflow pipe 64 which the condensed water 21 contacts from the integrated value of the electric current value. The degree can be detected.

  Furthermore, the determination unit 82a can determine whether or not the inner wall portion 64a is in an environment where the inner wall portion 64a is easily corroded, based on the strength of the corrosion of the condensed water 21 or the degree of corrosion of the inner wall portion 64a. For this reason, the corrosion detection system 52 for the fluid circulation member determines whether or not the inner wall portion 64a with which the condensed water 21 is in contact is more likely to corrode than in the conventional case where only the degree of corrosion is detected. It can be detected with high accuracy.

  Further, according to the fluid flow member corrosion detection system 52 according to the present embodiment, the first conductive member 90 includes the inner wall portion 64a of the exhaust gas inflow pipe 64, and therefore the first conductive member 90 is corroded. This can also be used as the exhaust gas inflow pipe 64 that is a detection target. For this reason, the number of parts can be reduced. And since the 1st electroconductive member 90 can be arrange | positioned in an actual corrosive environment, it can be detected more accurately whether the inner wall part 64a which the condensed water 21 contacts exists in the environment which is easy to corrode.

  Further, according to the fluid flow member corrosion detection system 52 according to the present embodiment, since the material of the second conductive member 91 is silver and the material of the first conductive member 90 is stainless steel, The ionization tendency of the second conductive member 91 is smaller than the ionization tendency of the first conductive member 90. For this reason, when the condensed water 21 adheres across the first conductive member 90 and the second conductive member 91, only the first conductive member 90 is corroded. Therefore, it is possible to detect with high accuracy whether or not the exhaust gas inflow pipe 64 is actually in an environment where it is easily corroded by corroding only the first conductive member 90 also used as the exhaust gas inflow pipe 64. Can do.

  Further, according to the fluid flow member corrosion detection system 52 according to the present embodiment, the determination unit 82a has the warning unit 83 that warns that the inner wall portion 64a of the exhaust gas inflow pipe 64 is in an environment where corrosion is likely to occur. Therefore, the driver can take appropriate measures after the warning.

  Further, according to the fluid flow member corrosion detection system 52 according to the present embodiment, the exhaust gas cooling pipe 63 is inclined so that the exhaust gas outflow pipe 65 side is positioned above the exhaust gas inflow pipe 64 side. Is provided. For this reason, the condensed water 21 generated inside the exhaust gas cooling pipe 63 flows down and is stored in the exhaust gas inflow pipe 64 due to the inclination of the exhaust gas cooling pipe 63. Since the EGR valve 54 is connected to the exhaust gas outlet pipe 65 side of the EGR cooler 51 (see FIG. 1), the condensed water 21 can be prevented from flowing into the EGR valve 54.

  In the fluid flow member corrosion detection system 52 of the present embodiment described above, the determination unit 82a compares the current value with the current threshold value to determine the corrosion strength of the condensed water 21, and integrates the current value. The degree of corrosion of the inner wall portion 64a with which the condensed water 21 is in contact is determined by comparing the value with the integrated threshold value. However, in the fluid flow member corrosion detection system according to the present invention, the determination is not limited to this, and the determination unit 82a only determines the strength of corrosion of the condensed water 21 by, for example, comparing a current value with a current threshold value. Therefore, the integrated value of the current value may not be compared with the integrated threshold value. Alternatively, the determination unit 82a compares, for example, the integrated value of the current value with the integrated threshold value, and only determines the degree of corrosion of the inner wall portion 64a with which the condensed water 21 contacts, and does not compare the current value with the current threshold value. You may do it.

  Further, in the fluid flow member corrosion detection system 52 according to the present embodiment described above, the first conductive member 90 is also used as the exhaust gas inflow pipe 64. However, in the corrosion detection system for a fluid circulation member according to the present invention, the present invention is not limited to this, and the first conductive member 90 may be a member separate from the exhaust gas inflow pipe 64.

  In addition, according to the fluid flow member corrosion detection system 52 according to the present embodiment, the material of the second conductive member 91 is silver. However, in the fluid flow member corrosion detection system according to the present invention, the material of the second conductive member 91 is not limited to this, and any material that is smaller than the ionization tendency of the first conductive member 90 may be used. Gold or platinum may be used. Also in these cases, it is possible to detect with higher accuracy whether or not the inner wall portion 64a with which the condensed water 21 comes into contact is actually in an environment that is easily corroded.

  In addition, according to the fluid flow member corrosion detection system 52 according to the present embodiment, the ionization tendency of the material of the second conductive member 91 is smaller than the ionization tendency of the material of the first conductive member 90. Yes. However, in the corrosion detection system for a fluid circulation member according to the present invention, the ionization tendency of the material of the second conductive member 91 is greater than the ionization tendency of the material of the first conductive member 90. Also good. Also in this case, the current measuring unit 81 detects the current generated between the first conductive member 90 and the second conductive member 91 due to the adhesion of the condensed water 21, and the inner wall portion with which the condensed water 21 comes into contact is detected. It can be determined whether or not 64a is in a corrosive environment.

  Moreover, according to the corrosion detection system 52 of the fluid distribution member according to the present embodiment, the warning unit 83 that warns that the inner wall portion 64a is in an environment where corrosion is likely to occur is provided. However, in the fluid flow member corrosion detection system according to the present invention, the present invention is not limited to this, and instead of the warning unit 83, the exhaust gas inflow pipe 64 and the exhaust gas cooling pipe 63 in contact with the condensed water 21 are easily corroded. Therefore, an avoidance processing unit that performs an avoidance process may be provided. In this case, the avoidance processing unit performs a process for avoiding the exhaust gas inflow pipe 64 and the exhaust gas cooling pipe 63 in contact with the condensed water 21 from an environment that is easily corroded.

  Here, the avoidance processing unit can be a heating unit that heats the condensed water 21. An example of the heating means is a high-temperature exhaust gas 45. In this case, the EGR valve 54 is opened and the exhaust gas 45 is circulated through the EGR cooler 51. At this time, the cooling water 20 is not circulated through the EGR cooler 51. As a result, the high temperature exhaust gas 45 flows in order from the exhaust gas inflow pipe 64 through the exhaust gas cooling pipe 63 and the exhaust gas outflow pipe 65, so that the condensation that has adhered to the exhaust gas inflow pipe 64 and the exhaust gas cooling pipe 63. The water 21 is heated to 100 ° C. or more and evaporated. Or when chlorine is contained in the condensed water 21, even if the condensed water 21 does not evaporate, chlorine vaporizes from the heated condensed water 21 and the strength of corrosion of the condensed water 21 is reduced. As a result, the exhaust gas inflow pipe 64 and the exhaust gas cooling pipe 63 that come into contact with the condensed water 21 are released from the environment that is easily corroded.

  Or as a heating means, the heating apparatus which heats the adhesion site | part of the condensed water 21 from the outside is mentioned, for example. In this case, the exhaust gas 45 and the cooling water 20 are not circulated through the EGR cooler 51, and the exhaust gas inflow pipe 64 and the exhaust gas cooling pipe 63 are heated by a heating device. Thereby, the condensed water 21 adhering to the exhaust gas inflow pipe 64 and the exhaust gas cooling pipe 63 is heated to 100 ° C. or more and evaporated. Or when chlorine is contained in the condensed water 21, even if the condensed water 21 does not evaporate, chlorine vaporizes from the heated condensed water 21 and the strength of corrosion of the condensed water 21 is reduced. As a result, the exhaust gas inflow pipe 64 and the exhaust gas cooling pipe 63 that come into contact with the condensed water 21 are released from the environment that is easily corroded.

  Further, according to the fluid flow member corrosion detection system 52 according to the present embodiment, the sensor unit 80 is provided on the lower inner wall 64 a of the exhaust gas inflow pipe 64. However, in the corrosion detection system for a fluid flow member according to the present invention, the present invention is not limited to this, and the installation location of the sensor unit 80 may be a portion where the condensed water 21 may come into contact. For example, the exhaust gas cooling pipe 63 When the EGR cooler 51 is installed horizontally, it may be provided on the inner wall part below the exhaust gas outflow pipe 65.

  Further, according to the corrosion detection system 52 for a fluid circulation member according to the present embodiment, the insulating means 92 is a substantially square having a side of about 10 mm, and the second conductive member 91 is a substantially square having a side of about 8 mm. To be. However, in the corrosion detection system for a fluid circulation member according to the present invention, the size and shape of the insulating means 92 and the second conductive member 91 are not limited to this, and the size and shape of the EGR cooler 51 or the sensor unit 80 are used. It can set suitably according to the installation position.

  Further, in the fluid flow member corrosion detection system 52 of the present embodiment described above, as shown in FIG. 2, the exhaust gas cooling pipe 63 has an exhaust gas outflow pipe 65 side above the exhaust gas inflow pipe 64 side. Inclined so as to be positioned. However, the corrosion detection system for a fluid circulation member according to the present invention is not limited to this. For example, the exhaust gas cooling pipe 63 is horizontal or the exhaust gas outflow pipe 65 side is positioned below the exhaust gas inflow pipe 64 side. It may be provided so as to be inclined. In any case, the installation location of the sensor unit 80 may be a portion where the condensed water 21 may come into contact, and can be set as appropriate.

  Further, according to the corrosion detection system 52 for a fluid circulation member according to the present embodiment, the corrosion detection system 52 is mounted on the EGR cooler 51. However, in the fluid flow member corrosion detection system according to the present invention, the present invention is not limited to this, as long as it is a conductive fluid flow member that circulates exhaust gas or intake gas of an internal combustion engine and that contacts condensed water. You may make it mount | wear with another member. For example, a corrosion detection system for a fluid circulation member may be attached to a pipe member that is in contact with intake gas inside the intercooler.

  Further, in the fluid flow member corrosion detection system 52 of the present embodiment described above, the EGR cooler 51 includes a large number of exhaust gas cooling pipes 63 as shown in FIG. The heat exchange between the cooling water 45 and the cooling water 20 is performed. However, in the corrosion detection system for a fluid circulation member according to the present invention, the present invention is not limited to this. For example, an EGR cooler includes tubes and fins, and heat exchange between exhaust gas and cooling water is performed in the tubes and fins. Also good. Here, the tube is composed of a partition wall that separates the exhaust gas and the cooling water, and the fins are sandwiched between the tubes to increase the cooling area of the exhaust gas.

  As described above, the fluid flow member corrosion detection system according to the present invention detects the strength and degree of corrosion of the fluid flow member due to condensed water generated in the EGR cooler or intercooler of the EGR system of the internal combustion engine. It is useful in a suitable fluid flow member corrosion detection system.

  The current between the first conductive member 90 and the second conductive member 91 was measured using the fluid flow member corrosion detection system 52 described above. The results are shown in FIG. 5 as a graph in which the horizontal axis represents the measurement time (unit seconds) and the vertical axis represents the current value (unit logA).

Example 1
After the engine 1 was started, the EGR valve 54 was closed. After the elapse of a predetermined time, the EGR valve 54 was opened. After the elapse of the predetermined time, the EGR valve 54 was closed. The change in the current value between the first conductive member 90 and the second conductive member 91 at this time is shown by a solid line in FIG.

  When the EGR valve 54 was closed immediately after the engine was started (reference CL1), the EGR cooler 51 was at a relatively low temperature. For this reason, the exhaust gas 45 that has entered the EGR cooler 51 from the exhaust device 4 is cooled, and the humidity around the sensor unit 80 increases, or the condensed water 21 is slightly generated in part. As a result, when the EGR valve 54 is closed immediately after starting the engine (reference numeral CL1), the current value gradually increased as shown by the solid line in FIG.

  When the EGR valve 54 is opened (reference OP), a large amount of condensed water 21 is generated by introducing a large amount of exhaust gas into the EGR cooler 51 and cooling it. As a result, when the EGR valve 54 is opened (reference OP), the current value rapidly increased as shown by the solid line in FIG.

  Further, when the EGR valve 54 is subsequently closed (reference CL2), the EGR cooler 51 has residual heat. For this reason, the humidity around the sensor unit 80 has decreased, or the condensed water 21 has evaporated. As a result, when the EGR valve 54 is subsequently closed (reference CL2), the current value gradually decreased as shown by the solid line in FIG.

(Comparative Example 1)
After the engine 1 was started, the EGR valve 54 was kept closed. A change in current value between the first conductive member 90 and the second conductive member 91 is shown by a broken line in FIG.

  As in Example 1, immediately after the engine was started (reference CL1), the EGR cooler 51 was relatively low temperature. For this reason, the exhaust gas 45 that has entered the EGR cooler 51 from the exhaust device 4 is cooled, and the humidity around the sensor unit 80 increases, or the condensed water 21 is slightly generated in part. As a result, immediately after starting the engine (reference numeral CL1), the current value gradually increased as indicated by the broken line in FIG.

  Thereafter, the heat of the engine 1 was transmitted to the EGR valve 54, and the EGR cooler 51 was heated (reference numeral CL2). For this reason, the humidity around the sensor unit 80 has decreased, or the condensed water 21 has evaporated. As a result, after heating the EGR cooler 51 (reference CL2), the current value gradually decreased as shown by the solid line in FIG.

  From the above, it was confirmed that when the exhaust gas 45 is cooled and condensed water 21 is generated, a large current may flow between the first conductive member 90 and the second conductive member 91. Further, when a large current flows between the first conductive member 90 and the second conductive member 91, the large current can be detected by the corrosion detection system 52 of the fluid flow member, and the driver can be warned. It was confirmed that there was.

1 engine (internal combustion engine)
5 EGR system 21 Condensed water 45 Exhaust gas 51 EGR cooler 52 Corrosion detection system 64 Exhaust gas inflow pipe (fluid distribution member, pipe member)
64a Inner wall (first conductive member)
80 Sensor part 81 Current measurement part 82 ECU
82a Judgment unit 83 Warning unit 90 First conductive member 91 Second conductive member 92 Insulating means

Claims (7)

A first conductive member made of the same material as that of the fluid circulation member and an ionization tendency different from that of the fluid circulation member is provided inside the conductive fluid circulation member for circulating exhaust gas or intake gas of the internal combustion engine. A sensor unit comprising: a second conductive member made of a material; and insulating means for insulating the first conductive member and the second conductive member from each other;
The condensed water generated in the inside flows between the first conductive member and the second conductive member by adhering across the first conductive member and the second conductive member. A current measuring unit for measuring current;
On the condition that the current value obtained by the current measuring unit exceeds a preset current threshold value, or the integrated value of the current value exceeds a preset integrated threshold value, the inner wall portion of the fluid circulation member A determination unit that determines that the environment is susceptible to corrosion by the condensed water;
A fluid flow member corrosion detection system comprising:   The corrosion detection system for a fluid circulation member according to claim 1, wherein the first conductive member is the inner wall portion.   The corrosion detection system for a fluid circulation member according to claim 1 or 2, wherein the material of the second conductive member has a smaller ionization tendency than the material of the first conductive member.   Provided with a warning unit that warns that the inner wall is in an environment susceptible to corrosion by the condensed water, provided that the determination unit determines that the inner wall is in an environment susceptible to corrosion by the condensed water. The corrosion detection system for a fluid circulation member according to any one of claims 1 to 3, wherein the corrosion detection system is a fluid distribution member.   On the condition that the determination unit determines that the inner wall portion is susceptible to corrosion by the condensed water, an avoidance processing portion that performs processing to avoid the inner wall portion from being in an environment susceptible to corrosion by the condensed water. 5. The fluid flow member corrosion detection system according to any one of claims 1 to 4, characterized by comprising:   The said avoidance process part is a heating means which heats the said condensed water, The corrosion detection system of the fluid distribution | circulation member of Claim 5 characterized by the above-mentioned.   The said fluid circulation member is a pipe member which distribute | circulates the said exhaust gas provided in the EGR cooler, The corrosion detection system of the fluid circulation member as described in any one of Claim 1 thru | or 6 characterized by the above-mentioned.

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