JP2009264339A - Exhaust recirculation device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust recirculation device of an internal combustion engine capable of preventing the occurrence of cavitation by restraining the introduction of a condensate into a compressor. <P>SOLUTION: This exhaust recirculation device 15 is applied to the internal combustion engine 1 having a turbocharger 6, and introduces exhaust gas taken out of an exhaust passage to the upstream side of the compressor 6A after cooling. The compressor 6A has an impeller 21, a casing 22 forming a main passage 24 for introducing gas to the impeller 21, and a casing treatment 23 arranged in the casing 22 and forming a sub-passage 25 merging again into the main passage 24 by branching off from the main passage 24. The sub-passage 25 is provided with an adsorbent 26 capable of capturing moisture and capable of drying the captured moisture by the gas flowing in the sub-passage 25. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas recirculation device for an internal combustion engine that is applied to an internal combustion engine equipped with a turbocharger and takes out a part of exhaust gas from an exhaust passage and cools it to introduce it into an intake passage.

  As an exhaust gas recirculation device for an internal combustion engine, there is known an exhaust gas recirculation device that takes out a part of exhaust gas from a downstream side of a turbine of a turbocharger, cools it, and introduces it to an upstream side of a compressor of the turbocharger (Patent Document 1). In addition, Patent Documents 2 to 4 exist as prior art documents related to the present invention.

Japanese Patent Laid-Open No. 10-68358 JP 2003-106299 A JP 2007-224789 A JP 2001-263091 A

  Since the exhaust gas recirculation device of Patent Document 1 cools part of the exhaust gas taken out from the exhaust passage, condensed water is generated due to the temperature drop, and the condensed water is also introduced upstream of the compressor together with the extracted exhaust gas. When condensed water is introduced into the compressor, bubbles are generated when the impeller stirs the condensed water, and cavitation that causes impact occurs when the bubbles reach the high-pressure field on the back of the impeller blade and disappear. . Depending on the degree of cavitation, the impeller of the compressor may be damaged by the impact of cavitation.

  Therefore, an object of the present invention is to provide an exhaust gas recirculation device for an internal combustion engine that can prevent the occurrence of cavitation by suppressing the introduction of condensed water into the compressor.

  The exhaust gas recirculation device according to the present invention is applied to an internal combustion engine including a turbocharger having a turbine provided in an exhaust passage and a compressor provided in an intake passage, and exhaust gas from the exhaust passage on the downstream side of the turbine. In the exhaust gas recirculation apparatus for an internal combustion engine that is introduced into the intake passage upstream of the compressor after the part is taken out and cooled, the compressor includes an impeller, a casing that forms a main passage that guides gas to the impeller, and the casing And a casing treatment that forms a sub-passage that branches off from the main passage and merges with the main passage again, and the sub-passage formed by the casing treatment can capture moisture and An adsorbent capable of drying the trapped moisture by the gas flowing through the sub-passage is provided. By Rukoto, to solve the problems described above (Claim 1).

  According to this exhaust gas recirculation device, even when the condensed water generated by cooling the exhaust gas taken out from the exhaust passage is led upstream of the compressor, the condensed water is removed by the adsorbent provided in the compressor casing treatment. Can be captured. Thereby, since the introduction of condensed water to the compressor is suppressed, the occurrence of cavitation can be prevented. Then, after the adsorbent captures the condensed water, the condensed water is released by drying by the gas flowing through the secondary passage of the casing treatment, so that the function of the adsorbent can be maintained. That is, the function of the adsorbent can be naturally recovered by continuing the operation of the internal combustion engine without performing a special operation for releasing the condensed water captured by the adsorbent. For example, when the internal combustion engine is in a low rotation light load state, the amount of EGR is large and the amount of condensed water generated is large. In such an operating state, the condensed water can be captured by the adsorbent. When the internal combustion engine is in a high rotation and high load state, the amount of EGR is small, the amount of condensed water generated is small, and the flow rate of gas flowing through the casing treatment is large, so that the adsorbent can be dried.

  In one aspect of the exhaust gas recirculation apparatus of the present invention, the sub-passage extends in a direction toward the impeller, and has an upstream opening that opens to the main passage on a side far from the impeller, and a side close to the impeller The adsorbent may be provided in the upstream opening portion (Claim 2). According to this aspect, when condensed water enters the main passage, the condensed water can be captured by the adsorbent on the upstream side far from the impeller, so that the condensed water can be prevented from approaching the impeller.

  In this aspect, the adsorbent may be provided in a state of blocking a part of the upstream opening (Claim 3). In this case, the entire upstream opening is not blocked by the adsorbent. Therefore, since the gas flow in the sub passage is not completely restricted, the function of the casing treatment is not impaired.

  In these aspects, the compressor may be provided in the intake passage such that the upstream side opening is oriented vertically upward in the main passage (claim 4). Since the condensed water guided to the intake passage gathers vertically below the main passage due to gravity, the condensed water can be effectively guided to the upstream opening that opens vertically upward. Thereby, condensed water can be efficiently captured by the adsorbent provided in the upstream opening.

  As described above, according to the present invention, it is possible to suppress the introduction of condensed water into the compressor by capturing the condensed water with the adsorbent provided in the casing treatment of the compressor, thereby preventing the occurrence of cavitation. Can do.

  FIG. 1 shows a main part of an internal combustion engine to which an exhaust gas recirculation apparatus of the present invention is applied. The internal combustion engine 1 is mounted on a vehicle (not shown) as a driving power source, and is configured as an in-line four-cylinder diesel engine in which four cylinders 2 are arranged in a row. An intake passage 3 and an exhaust passage 4 are connected to each cylinder 2. The intake passage 3 is provided with a throttle valve 5, a compressor 6A of a turbocharger 6, and an intercooler 7. In the exhaust passage 4, a turbine 6 </ b> B of the turbocharger 6 and an exhaust purification device 8 are provided. The internal combustion engine 1 includes a fuel injection valve 9 provided in each cylinder 2 and a common rail 10 that stores high-pressure fuel supplied to each fuel injection valve 9, and the common rail 10 includes a fuel pump (not shown). The fuel is supplied in a high pressure state.

  The exhaust purification device 8 includes a casing 11 that forms part of the exhaust passage 4, and an oxidation catalyst 12 and a filter 13 that are accommodated in the casing 11. The filter 13 has a base material (not shown) that can collect particulates in the exhaust. By coating the base material of the filter 13 with the NOx storage reduction catalyst material, the filter 13 can be given a function of purifying NOx in the exhaust gas. When the amount of particulates collected by the filter 13 reaches the limit, fuel is injected into the exhaust passage 4 by the fuel addition valve 14 provided in the exhaust passage 4, and the injected fuel is oxidized. A PM regeneration process is performed in which the particulates collected by the filter 13 are burned using heat generated by oxidation (combustion) by the catalyst 10 to restore the function of the filter 13.

  The internal combustion engine 1 is provided with an exhaust gas recirculation device 15 that recirculates exhaust gas to the intake system. The exhaust gas recirculation device 15 includes an EGR passage 16 that connects the exhaust passage 4 on the downstream side of the turbine 6B and the intake passage 3 on the upstream side of the compressor 6A, an EGR cooler 17 that cools EGR gas, and an EGR gas to the intake passage 3 And an EGR valve 18 for adjusting the introduction amount. Thereby, the exhaust gas recirculation device 15 takes out a part of the exhaust gas from the exhaust passage 4 on the downstream side of the turbine 6B, cools the EGR gas by the EGR cooler 17, and then introduces the EGR gas into the intake passage 3 on the upstream side of the compressor 6A. be able to. The exhaust gas recirculation device 15 takes out the exhaust gas from the downstream side of the turbine 6B and introduces it to the upstream side of the compressor 6A. Therefore, the exhaust gas recirculation device 15 may be called a low pressure loop type exhaust gas recirculation device.

  As the EGR gas is cooled by the EGR cooler 17, condensed water is generated due to moisture in the exhaust. Condensed water is a liquid in which various substances contained in exhaust gas are dissolved in water. This condensed water is guided upstream of the compressor 6A through the EGR passage 16. When the condensed water is guided to the compressor 6A, the above-described cavitation occurs, which may cause damage to the impeller of the compressor 6A. Therefore, the exhaust gas recirculation device 15 of the present embodiment is provided with a measure for suppressing the introduction of the condensed water to the compressor 6A.

  FIG. 2 schematically shows details of the internal structure of the compressor 6A. As shown in FIG. 2, the compressor 6 </ b> A includes an impeller 21, a casing 22 that forms a main passage 24 that guides gas to the impeller 21, a casing 22, a branch from the main passage 24, and a branch to the main passage 24 again. And a casing treatment 23 that forms a sub-passage 25 that merges. The main passage 24 functions as a part of the intake passage 3. The sub passage 25 extends in a direction toward the impeller 21. The auxiliary passage 25 has an upstream opening 25a that opens to the main passage 24 on the side far from the impeller 21 (left side in FIG. 2), and a downstream opening that opens to the main passage 24 on the side close to the impeller 21 (right side in FIG. 2). Part 25b. As is well known, the casing treatment 23 has a function of circulating gas in the direction of the arrow in FIG. 2 using the auxiliary passage 25 in order to prevent surging at a low flow rate.

  The sub-passage 25 of the casing treatment 23 is provided with an adsorbent 26 that can trap water and dry the water trapped by the gas flowing through the sub-passage 25. As a material of the adsorbent 26, silica gel, zeolite, or the like can be selected. In this embodiment, the adsorbent 26 is provided in a state where a part of the upstream opening 25a of the sub passage 25 is closed. Therefore, as shown in FIG. 2, when condensed water W enters the main passage 24, the condensed water W can be captured by the adsorbent 26 on the upstream side far from the impeller 21, so that the condensed water W enters the impeller 21. It can prevent approaching. The adsorbent 26 only blocks a part of the upstream opening 25a but does not block all of it. For this reason, since the gas flow in the sub passage 25 is not completely restricted, the function of the casing treatment 23 is not impaired.

  The compressor 6A is provided in the intake passage 3 so that the upstream opening 25a of the sub-passage 25 is oriented vertically upward to the main passage 24. Since the condensed water guided to the intake passage 3 gathers vertically below the main passage 24 due to gravity, the condensed water can be effectively guided to the upstream opening 25a that opens vertically upward. As a result, the condensed water can be efficiently captured by the adsorbent 26 provided in the upstream opening 25a.

  FIG. 3 is an explanatory diagram for explaining the function of the adsorbent 26 in relation to the operating state of the internal combustion engine 1. Each amount is shown. Each curve shown in the figure shows the operating state at the same intake flow rate. In general, the amount of EGR increases because the EGR amount increases as the internal combustion engine 1 has a lower rotation and light load. Therefore, as shown in FIG. 3, the amount of condensed water generated increases as the intake flow rate decreases. Therefore, the condensed water stops in the region where the intake flow rate indicated by hatching is small, and the condensed water is captured by the adsorbent 26. On the other hand, in a region where the intake air flow rate is large, the amount of EGR is small and the amount of condensed water generated is small, so that the condensed water captured by the adsorbent 26 is dried by the gas flow in the auxiliary passage 25 of the casing treatment 23, 26 functions are restored. Since the adsorbent 26 has such a function, the function of the adsorbent 26 is naturally recovered by continuing the operation of the internal combustion engine 1 without performing a special operation to release the captured condensed water. be able to.

  This invention is not limited to the above form, It can implement with a various form. The sub-passage formed by the casing treatment may have a tubular shape surrounded by the periphery, or may have a groove shape opened to the main passage. Further, the direction in which the sub passage extends is also arbitrary. Furthermore, the secondary passage may be an annular passage that makes a circuit in the circumferential direction of the main passage. In short, it is only necessary that an adsorbent capable of capturing condensed water is provided at any position of the sub-passage formed by the casing treatment.

  What is necessary is just to set the material and magnitude | size of an adsorbent suitably according to the specifications of internal combustion engines, such as the generation amount of condensed water, and the operating area | region normally used. The type of the internal combustion engine that can be applied to the present invention is not limited to a diesel engine, but may be a spark ignition type internal combustion engine.

The figure which showed the principal part of the internal combustion engine to which the exhaust gas recirculation apparatus which concerns on one form of this invention was applied. The figure which showed the detail of the internal structure of a compressor typically. Explanatory drawing explaining the function of an adsorbent in relation to the driving | running state of an internal combustion engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Intake passage 4 Exhaust passage 6 Turbocharger 6A Compressor 6B Turbine 15 Exhaust gas recirculation device 21 Impeller 22 Casing 23 Casing treatment 24 Main passage 25 Sub passage 25a Upstream opening 25b Downstream opening 26 Adsorbent

Claims (4)

The invention is applied to an internal combustion engine including a turbocharger having a turbine provided in an exhaust passage and a compressor provided in an intake passage, and after a part of exhaust gas is taken out from the exhaust passage on the downstream side of the turbine and cooled, the In the exhaust gas recirculation device for an internal combustion engine to be introduced into the intake passage on the upstream side of the compressor,
The compressor includes an impeller, a casing that forms a main passage that guides gas to the impeller, and a casing treatment that is provided in the casing and that forms a sub-passage that branches from the main passage and merges with the main passage again. Have
The sub-passage formed by the casing treatment is provided with an adsorbent capable of trapping moisture and drying the trapped moisture by gas flowing through the sub-passage. Exhaust gas recirculation device. The sub-passage extends in a direction toward the impeller, and has an upstream opening that opens to the main passage on a side far from the impeller, and a downstream opening that opens to the main passage on a side close to the impeller And
The exhaust gas recirculation apparatus according to claim 1, wherein the adsorbent is provided in the upstream opening.   The exhaust gas recirculation apparatus according to claim 2, wherein the adsorbent is provided in a state of blocking a part of the upstream opening.   4. The exhaust gas recirculation apparatus according to claim 2, wherein the compressor is provided in the intake passage such that the upstream opening is oriented vertically upward in the main passage. 5.

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