JP2020063684A - Exhaust emission recirculation device of internal combustion engine - Google Patents

Abstract

To provide an exhaust emission recirculation device of an internal combustion engine which can suppress the corrosion of an EGR cooler.SOLUTION: A boiling point of an alkaline component contained in condensed water produced from an EGR gas is set as a first boiling point, a boiling point of an acid component contained in the condensed water being a temperature higher than the first boiling point is set as a second boiling point, a temperature equal to the first boiling point or higher, and lower than the second boiling point is set as a first temperature, and a temperature equal to the second boiling point or higher, and lower than a temperature of the EGR gas before being cooled by an EGR cooler is set as a second temperature. An exhaust emission recirculation device 200 comprises a first EGR cooler 40 which can cool an EGR gas down to the first temperature, and in which a flow passage of the EGR gas is formed of an acid resistance material, and a second EGR cooler 41 which can cool the EGR gas down to the second temperature.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine.

  An EGR cooler is provided in the exhaust gas recirculation device of the internal combustion engine. For example, the exhaust gas recirculation device described in Patent Document 1 includes a first EGR cooler having high cooling efficiency and a second EGR cooler having low cooling efficiency, and each EGR cooler is formed of an aluminum alloy having high thermal conductivity. .

JP, 2010-185351, A

  Condensed water generated from the EGR gas may include acidic components such as hydrochloric acid and sulfuric acid and alkaline components such as ammonium hydroxide, which are derived from the fuel components. Here, when the EGE gas is cooled to a temperature lower than the boiling point of the alkaline component in the first EGR cooler having a high cooling efficiency, the alkaline component comes to be contained in the condensed water. The gas passage of the first EGR cooler may be corroded.

  An exhaust gas recirculation device for an internal combustion engine that solves the above problem includes an EGR cooler that cools EGR gas. The boiling point of the alkaline component contained in the condensed water generated from the EGR gas is the first boiling point, and the boiling point of the acidic component contained in the condensed water which is higher than the first boiling point is the second boiling point. A temperature that is equal to or higher than 1 boiling point and lower than the second boiling point is a first temperature, and a temperature that is equal to or higher than the second boiling point and lower than the temperature of the EGR gas before being cooled by the EGR cooler is the second temperature. When the temperature is set to the temperature, the EGR cooler is capable of cooling the EGR gas to the first temperature, and the EGR gas has a flow path formed of an acid resistant material, and the EGR gas up to the second temperature. And a second EGR cooler that can be cooled. An EGR gas cooled by the first EGR cooler and an EGR gas cooled by the second EGR cooler are supplied to the intake passage of the internal combustion engine, and an exhaust gas flowing through the exhaust passage of the internal combustion engine. And an exhaust side EGR passage for independently supplying the first EGR cooler and the second EGR cooler with each part as EGR gas.

  According to this configuration, when the EGR gas passes through the first EGR cooler, the temperature of the EGR gas decreases to the first temperature, so that the alkaline component is in a vaporized state and the condensed water has an acidic component. Will remain. Here, since the flow path of the EGR gas in the first EGR cooler is made of an acid resistant material, even if the acidic component remains in the condensed water generated in the first EGR cooler, the corrosion of the flow path is suppressed. Become.

  Further, when the EGR gas passes through the second EGR cooler, the temperature of the EGR gas drops to the second temperature, so that both the alkaline component and the acidic component are vaporized, and the respective components are condensed water. Is hard to be included in. Therefore, when condensed water is generated in the second EGR cooler, it is possible to prevent the generated condensed water from corroding the gas passage of the second EGR cooler.

The schematic diagram which shows the exhaust gas recirculation apparatus of the internal combustion engine in one embodiment. The figure which shows the cooling capacity of the EGR cooler of the same embodiment. The schematic diagram which shows the exhaust gas recirculation apparatus in the modification of the embodiment.

Hereinafter, an embodiment of an exhaust gas recirculation device for an internal combustion engine will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the internal combustion engine 10 includes an intake passage 13 having a throttle valve 14 and an exhaust passage 15 through which exhaust gas flows.

  A three-way catalyst 17, which is a catalyst for purifying exhaust gas, is provided in the exhaust passage 15. Exhaust gas flowing into the three-way catalyst 17 may contain hydrochloric acid, sulfuric acid, etc. due to the fuel component, and exhaust gas upstream of the three-way catalyst 17 may contain a large amount of such acidic components. is there. The acidic component contained in the exhaust gas is reduced by the catalytic action when passing through the three-way catalyst 17. Further, due to the catalytic action and the fuel component when the exhaust gas passes through the three-way catalyst 17, the exhaust gas that has passed through the three-way catalyst 17 may contain ammonium hydroxide or the like, and such alkaline components may When it is contained, the exhaust gas on the downstream side of the three-way catalyst 17 contains more alkaline components than acidic components.

The internal combustion engine 10 includes an exhaust gas recirculation device 200 that returns a part of exhaust gas to the intake passage 13 as EGR gas.
The exhaust gas recirculation device 200 includes a water-cooled first EGR cooler 40 that exchanges heat between engine cooling water and EGR gas, and a water-cooled second EGR cooler 41. The first EGR cooler 40 is formed of an acid resistant material (for example, an aluminum alloy), so that the gas flow path of the EGR gas in the first EGR cooler 40 is also formed of an acid resistant material. On the other hand, the second EGR cooler 41 is made of an alkali resistant material (for example, stainless steel), and thus the gas flow path in which the EGR gas flows in the second EGR cooler 41 is also made of an alkali resistant material.

  As shown in FIG. 2, the boiling point of the alkaline component contained in the condensed water generated from the EGR gas when cooled by the EGR cooler is the first boiling point BTa, and the temperature is higher than the first boiling point BTa and becomes the condensed water. The boiling point of the contained acidic component is referred to as the second boiling point BTs. The first boiling point BTa may be, for example, 37.7 degrees, which is the boiling point of ammonium hydroxide contained in condensed water. In addition, examples of the second boiling point BTs include 290 degrees, which is the boiling point of sulfuric acid contained in condensed water.

  Further, a temperature that is equal to or higher than the first boiling point BTa and lower than the second boiling point BTs is set as a first temperature TH1, and a temperature THegr of the EGR gas that is a temperature equal to or higher than the second boiling point BTs and that is not cooled by the EGR cooler (for example, A temperature lower than 450 to 500 degrees is referred to as a second temperature TH2.

  The cooling structure CA of the first EGR cooler 40 is configured such that the cooling capacity CA of the first EGR cooler 40 has a capacity capable of cooling the EGR gas flowing into the first EGR cooler 40 to the first temperature TH1. There is.

  In addition, the cooling structure of the second EGR cooler 41 is configured such that the cooling capacity CB of the second EGR cooler 41 has a capacity capable of cooling the EGR gas flowing into the second EGR cooler 41 to the second temperature TH2. There is. The temperature of the engine cooling water flowing in the first EGR cooler 40 and the second EGR cooler 41 is lower than the second boiling point BTs which is the boiling point of the acidic component.

  As shown in FIG. 1, the exhaust gas recirculation device 200 includes an exhaust side EGR passage 30 that supplies a part of the exhaust gas flowing in the exhaust passage 15 as EGR gas to the first EGR cooler 40 and the second EGR cooler 41, respectively. There is.

  The exhaust side EGR passage 30 includes an exhaust side branch passage 31 branched from the exhaust passage 15 on the downstream side of the three-way catalyst 17, and a first exhaust side passage 32 connecting the exhaust side branch passage 31 and the first EGR cooler 40. And a second exhaust side passage 33 that connects the exhaust side branch passage 31 and the second EGR cooler 41. In the exhaust gas recirculation device 200 of the present embodiment, the condensed water LQ1 generated in the first EGR cooler 40 and the condensed water LQ2 generated in the second EGR cooler 41 are introduced into the exhaust passage 15 via the exhaust side EGR passage 30. Is configured.

  Further, the exhaust gas recirculation device 200 includes an intake-side EGR passage 50 that supplies the EGR gas cooled by the first EGR cooler 40 and the EGR gas cooled by the second EGR cooler 41 to the intake passage 13.

  The intake-side EGR passage 50 includes an intake-side branch passage 51 that branches from the intake passage 13, a first intake-side passage 52 that connects the intake-side branch passage 51 and the first EGR cooler 40, an intake-side branch passage 51, and a first intake-side branch passage 51. The second intake-side passage 53 that connects the 2EGR cooler 41 is provided.

  The exhaust gas recirculation device 200 also includes a first EGR valve 60 that is provided in the first intake-side passage 52 and adjusts the flow rate of EGR gas that passes through the first EGR cooler 40 (EGR gas flow rate). When the first EGR valve 60 is open, the EGR gas flows through the first EGR cooler 40.

  The exhaust gas recirculation device 200 includes a second EGR valve 61 that is provided in the second intake-side passage 53 and adjusts the flow rate of EGR gas (EGR gas flow rate) that passes through the second EGR cooler 41. When the second EGR valve 61 is open, the EGR gas flows through the second EGR cooler 41. In the present embodiment, the second EGR valve 61 is the same as the first EGR valve 60.

  As shown in FIG. 1, the control device 100 includes a central processing unit (hereinafter referred to as CPU) 110 and a memory 120 in which a control program and data are stored. Then, the CPU 110 executes the programs stored in the memory 120 to execute various controls.

  The control device 100 includes a crank angle sensor 70 that detects the rotation angle of the crankshaft of the internal combustion engine 10, an air flow meter 71 that detects the intake air amount GA of the internal combustion engine 10, and a cooling water temperature that is the temperature of the cooling water of the internal combustion engine 10. A water temperature sensor 72 for detecting THW and the like are connected. Then, output signals from these various sensors are input to the control device 100. The control device 100 calculates the engine speed NE based on the output signal Scr of the crank angle sensor 70. The control device 100 also calculates the engine load factor KL based on the engine speed NE and the intake air amount GA.

  Then, the control device 100 performs various controls of the internal combustion engine 10 based on the detection results of those sensors. As one of such various controls, for example, the control device 100 performs exhaust gas recirculation control by adjusting the opening degree of the first EGR valve 60 and the second EGR valve 61 based on the engine rotation speed NE, the engine load factor KL, and the like. When performing such exhaust gas recirculation control, the first EGR valve 60 and the second EGR valve 61 are controlled at the same opening degree.

Next, the operation and effect of this embodiment will be described.
(1) As described above, when the exhaust gas downstream of the three-way catalyst 17 contains an acidic component or an alkaline component, the exhaust gas containing such various components flows into the exhaust side EGR passage 30 as EGR gas. The EGR gas flows into the first EGR cooler 40 and the second EGR cooler 41.

  Here, when the EGR gas passes through the first EGR cooler 40, the temperature of the EGR gas drops to the first temperature TH1, so that the alkaline component becomes vaporized and the acidic component remains in the condensed water. Like Here, since the gas passage of the first EGR cooler 40 is formed of an acid resistant material, even if the acidic component remains in the condensed water generated in the first EGR cooler 40, the corrosion of the gas passage can be suppressed. become.

  (2) Further, when the EGR gas passes through the second EGR cooler 41, the temperature of the EGR gas decreases to the second temperature TH2, so that both the alkaline component and the acidic component are vaporized, It becomes difficult for each component to be included in the condensed water. Therefore, even if condensed water is generated in the second EGR cooler 41, it is possible to prevent the condensed water from corroding the gas passage of the second EGR cooler 41.

  (3) As described above, when the EGR gas passes through the first EGR cooler 40, the temperature of the EGR gas decreases to the first temperature TH1, so that the alkaline component becomes vaporized while the acidic component is acidic. The components will remain in the condensed water. Therefore, the EGR gas GS1 (see FIG. 1) that has passed through the first EGR cooler 40 contains a large amount of alkaline components.

  On the other hand, when the EGR gas passes through the second EGR cooler 41, the temperature of the EGR gas decreases to the second temperature TH2, so that both the alkaline component and the acidic component are vaporized. Therefore, the EGR gas GS2 (see FIG. 1) that has passed through the second EGR cooler 41 contains an alkaline component and an acidic component.

  Therefore, when the EGR gas GS1 containing a large amount of alkaline components and the EGR gas GS2 containing an alkaline component and an acidic component merge in the intake side branch passage 51, the respective components are neutralized by a certain amount. Therefore, the amounts of alkaline components and acidic components contained in the EGR gas supplied from the intake side branch passage 51 to the intake passage 13 are reduced. Therefore, even if condensed water is generated in the intake passage 13, the condensed water is less likely to contain an alkaline component or an acidic component derived from the EGR gas. Therefore, it is possible to suppress corrosion of the intake system when condensed water is generated in the intake passage 13.

  (4) The exhaust gas recirculation device 200 includes the EGR passage including the first EGR cooler 40 (the first exhaust side passage 32 and the first intake side passage 52) and the EGR passage including the second EGR cooler 41 (the second exhaust side passage 33 and the second exhaust side passage 33. The second intake side passage 53) and the EGR gas flows through the EGR passages of these two systems, respectively. The first EGR valve 60 and the second EGR valve 61 ensure that the EGR gas flow rates in each system are the same. Therefore, in order to secure the same EGR gas flow rate as compared with the case where only one EGR passage is provided and one EGR valve is provided to adjust the EGR gas flow rate in the EGR passage of that one system. The opening degree of the first EGR valve 60 and the second EGR valve 61 required for the above is approximately halved, and the time required from the open state to the closed state is shortened.

  Therefore, in the present embodiment, the first EGR valve 60 and the second EGR valve 61 can be promptly closed, and as a result, the occurrence of misfire due to the closing delay of the EGR valve during deceleration can be suppressed. Since the occurrence of misfire due to the closing delay of the EGR valve is suppressed as described above, it becomes possible to recirculate a large amount of EGR gas before the start of deceleration, thereby improving the fuel efficiency. it can.

The present embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
Although the first EGR cooler 40 is formed of an aluminum alloy, it may be formed of another acid resistant material.

  -The condensed water generated in the second EGR cooler 41 does not easily contain an alkaline component or an acidic component. Therefore, the second EGR cooler 41 may be made of a material other than the alkali resistant material.

  The second EGR valve 61 was the same valve as the first EGR valve 60, but the second EGR valve 61 has a different flow rate characteristic from the first EGR valve 60 (that is, the correspondence between the valve opening degree and the gas flow rate is different). Different valves). Even in this case, the time required for the first EGR valve 60 and the second EGR valve 61 to change from the open state to the closed state is shorter than that in the case where only one system of EGR passages is provided. The same effect as 4) can be obtained.

  When executing the exhaust gas recirculation control, the first EGR valve 60 and the second EGR valve 61 are set to have the same opening, but they may be controlled to have different opening. Even in this case, the time required for the first EGR valve 60 and the second EGR valve 61 to change from the open state to the closed state is shorter than that in the case where only one system of EGR passages is provided. The same effect as 4) can be obtained.

  As an example of the second boiling point BTs which is the boiling point of the acidic component, 290 degrees which is the boiling point of sulfuric acid is mentioned, but the boiling point of other acidic components, for example, 110 degrees which is the boiling point of hydrochloric acid may be used as the second boiling point BTs. Good.

The first EGR cooler 40 and the second EGR cooler 41 were water-cooled, but any other method (such as an air-cooled type) may be used as long as the cooling capacities CA and CB can be satisfied.
As shown in FIG. 3, the exhaust side EGR passage 30 and the exhaust side branch passage 31 are omitted. Then, the first exhaust side passage 32 connected to the first EGR cooler 40 is connected to the exhaust passage 15 on the downstream side of the three-way catalyst 17, and the second exhaust side passage 33 connected to the second EGR cooler 41 is connected to the third exhaust side passage 33. It may be connected to the exhaust passage 15 on the upstream side of the original catalyst 17. In this case, the EGR gas containing a large amount of acidic components flows into the second EGR cooler 41, and since the acidic components pass through the second EGR cooler 41 in a vaporized state, the EGR gas that has passed through the second EGR cooler 41. A large amount of acidic components are contained in GS2. On the other hand, the EGR gas containing a large amount of alkaline components flows into the first EGR cooler 40, and since the alkaline components pass through the first EGR cooler 40 in a vaporized state, the EGR gas GS1 passing through the first EGR cooler 40 becomes Will contain alkaline components. As described above, in this modification, it becomes more clear whether the acidic component or the alkaline component is dominant in the components contained in the EGR gas after passing through the EGR cooler, and the same as in the above-described embodiment. The effect can be obtained.

  When the engine is cold, the second EGR cooler 41 may be preferentially used to introduce the EGR gas having a relatively high temperature into the intake air to stabilize the combustion of the air-fuel mixture. Further, the EGR gas having a relatively low temperature may be introduced into the intake air to lower the temperature of the combustion gas by preferentially using the first EGR cooler 40 when the engine is warm.

  10 ... Internal combustion engine, 13 ... Intake passage, 14 ... Throttle valve, 15 ... Exhaust passage, 17 ... Three way catalyst, 30 ... Exhaust side EGR passage, 31 ... Exhaust side branch passage, 32 ... First exhaust side passage, 33 ... 2nd exhaust side passage, 40 ... 1st EGR cooler, 41 ... 2nd EGR cooler, 50 ... intake side EGR passage, 51 ... intake side branch passage, 52 ... 1st intake side passage, 53 ... 2nd intake side passage, 60 ... 1st EGR valve, 61 ... 2nd EGR valve, 70 ... crank angle sensor, 71 ... air flow meter, 72 ... water temperature sensor, 100 ... control device, 110 ... central processing unit (CPU), 120 ... memory, 200 ... exhaust gas recirculation device.

Claims (1)

An exhaust gas recirculation device for an internal combustion engine, comprising an EGR cooler for cooling EGR gas,
The boiling point of the alkaline component contained in the condensed water generated from the EGR gas is the first boiling point, and the boiling point of the acidic component contained in the condensed water which is higher than the first boiling point is the second boiling point. A temperature that is equal to or higher than the second boiling point is defined as a first temperature, and a temperature that is equal to or higher than the second boiling point and lower than the temperature of the EGR gas before being cooled by the EGR cooler is defined as a second temperature. When I did
As the EGR cooler, a first EGR cooler capable of cooling the EGR gas to the first temperature and having a channel for the EGR gas formed of an acid resistant material, and a second EGR cooler capable of cooling the EGR gas to the second temperature And with
An intake side EGR passage for supplying the EGR gas cooled by the first EGR cooler and the EGR gas cooled by the second EGR cooler to an intake passage of an internal combustion engine;
An exhaust gas recirculation device for an internal combustion engine, comprising: an exhaust side EGR passage that supplies a part of exhaust gas flowing through an exhaust passage of the internal combustion engine as EGR gas independently to the first EGR cooler and the second EGR cooler.