JP2010174647A - Internal combustion engine with egr device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine with a more compact EGR device than ever before, allowing quick warming-up in cold-start of an engine. <P>SOLUTION: The engine includes the EGR device for taking out part of exhaust from an exhaust system of the engine as EGR gas to recirculate it in an intake system. In the EGR device, an EGR passage recirculating the EGR gas therein is formed between a cylinder bore wall face and a cylinder block outer wall face, and can exchange heat between the EGR gas flowing therein and the cylinder bore wall face, and includes an internal passage covering the cylinder wall face while approaching the cylinder bore wall face and being extended in an axial direction of a cylinder bore. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine provided with an EGR device.

  Conventionally, as a technique for reducing the emission of nitrogen oxides (NOx) from an internal combustion engine, an exhaust gas recirculation device (EGR device) for an internal combustion engine that extracts a part of the exhaust gas flowing through the exhaust system and recirculates it to the intake system as EGR gas Is known. As described above, when the EGR gas is recirculated to the intake system, combustion of the internal combustion engine becomes slow, so that the amount of nitrogen oxide (NOx) generated can be reduced.

  Patent Document 1 discloses an exhaust gas recirculation apparatus in which an internal passage is formed in a cylinder block along a cylinder row below and adjacent to a water jacket formed in a cylinder block, and this is used as a main part of an exhaust gas recirculation path. Has been proposed.

JP 2008-082307 A JP 2006-291821 A

  By the way, when the internal combustion engine is cold-started, it is required to quickly warm up the engine. Here, when the internal passage as the main portion of the exhaust gas recirculation path is disposed only in the lower vicinity of the water jacket as in the above configuration, the recirculation exhaust gas (EGR gas) flowing through the internal passage and the cooling water in the water jacket The heat exchange with is limited to local ones. If it does so, it became difficult to warm up the whole cylinder bore efficiently at the time of a cold start, and there existed the actual situation that early warming up of an internal combustion engine became difficult.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an internal combustion engine that can be quickly warmed up at the time of cold start and includes a more compact EGR device. There is to do.

  In order to achieve the above object, an internal combustion engine equipped with an EGR device according to the present invention employs the following means. That is, an internal combustion engine including an EGR device that extracts a part of exhaust gas from the exhaust system of the internal combustion engine as EGR gas and recirculates it to the intake system, and the EGR passage through which the EGR device recirculates EGR gas includes a cylinder bore wall surface and A passage formed between the outer wall surface of the cylinder block and capable of exchanging heat between the EGR gas flowing through the cylinder block wall surface and the cylinder bore wall surface, covering the cylinder bore wall surface while being close to the cylinder bore wall surface, and the cylinder bore axial direction It is characterized by including the internal passage extended in this.

In this configuration, a part of the exhaust gas flowing through the exhaust system of the internal combustion engine is recirculated to the intake system after passing through the internal flow path formed in the cylinder block. In the present invention, when the internal combustion engine is cold-started, the high-temperature exhaust immediately after being discharged from the internal combustion engine is led to the internal flow path as EGR gas, and heat exchange is performed between the EGR gas and the cylinder bore. Here, since the internal flow path extends in the axial direction of the cylinder bore, it can be said that the internal flow path extends in the vertical direction of the cylinder bore. Therefore, according to this configuration, the entire outer periphery of the cylinder bore is EG
It is possible to exchange heat with the R gas. Therefore, since the temperature of the entire cylinder bore can be efficiently raised at the time of cold start, early warm-up is possible. The vertical direction of the cylinder bore wall surface coincides with the sliding direction of the piston in the cylinder bore and coincides with the axial direction of the cylinder bore.

  Further, according to this configuration, a part of the EGR passage through which the EGR device recirculates the EGR gas is configured by an internal passage formed in the cylinder block, so that the EGR passage can be saved in space and compact. can do.

  In the present invention, the EGR passage is further formed inside the cylinder head and the cylinder block, communicates the upper end edge of the internal passage or its vicinity and the exhaust port, and part of the exhaust flowing through the exhaust port. An EGR gas introduction port to be introduced into the internal passage as EGR gas, and a lower end edge portion of the internal passage or a portion in the vicinity thereof and an intake pipe of the internal combustion engine communicate with each other through a hole opened in a side wall on the intake side of the cylinder block. And an introduction pipe for introducing the EGR gas in the internal passage into the intake pipe.

  According to this configuration, the exhaust gas flowing through the exhaust port is introduced into the internal passage through the EGR gas introduction port formed in the cylinder head, not the external passage formed outside the cylinder block. Therefore, further downsizing of the EGR device can be achieved. Further, since the EGR gas introduction port is opened on the side surface on the intake side of the cylinder block, the piping structure of the introduction pipe can be simplified. Even when a cooling device (EGR cooler) for cooling the EGR gas flowing through the introduction pipe is separately provided in the introduction pipe, the EGR gas is introduced into the introduction pipe after exchanging heat with the cylinder bore in the internal passage. . That is, since the cooling effect of the EGR gas can be expected when passing through the internal passage, it is not necessary to increase the cooling capacity of the cooling device so much. Therefore, the cooling device can be made more compact, so that the EGR device can be miniaturized and a reduction in manufacturing cost can be expected.

  By the way, the cylinder block wall surface forming the internal flow path is often made of a material having relatively low corrosion resistance. In contrast to this situation, when the EGR gas is cooled by heat exchange with the cylinder bore, condensed water (exhaust condensed water) is generated. If this condensed water is maintained in a state where it has been accumulated in the internal flow path for a long time, the cylinder block may be corroded.

  Therefore, in the present invention, at the connection point between the introduction pipe and the internal passage, the lowest part of the edge of the hole and the lower end edge of the internal passage are equal in height, and the inside at the connection part with the introduction pipe The height of the lower end edge of the passage may be made lower than the height of the lower end edge of the internal passage at the connection point with the EGR gas introduction port.

  According to this configuration, the condensed water generated inside the internal passage can be easily collected at the connection portion between the internal passage and the introduction pipe, and the condensed water is smoothly discharged to the introduction pipe. be able to. Thereby, the condensed water does not accumulate in the internal passage for a long time, and corrosion of the member forming the internal passage (that is, the inner wall surface of the cylinder block) is reliably suppressed. The introduction pipe is preferably made of a material having higher corrosion resistance than the internal passage. According to this, the introduction pipe is not corroded by the condensed water discharged from the internal passage. Moreover, the lower end edge part of the internal passage may be inclined so that its height gradually decreases from the connection point with the EGR gas introduction port toward the connection point with the introduction pipe. Thereby, the condensed water in an internal channel can be led to an introduction pipe more suitably.

Further, the internal combustion engine according to the present invention includes a condensed water discharge pipe for discharging condensed water in the internal flow path to the outside of the cylinder block through a hole opened in a side wall on the exhaust side of the cylinder block, and a condensed water discharge pipe. A condensate collecting unit connected to store condensed water via the condensed water discharge pipe, and a heat exchanger for recovering heat of exhaust flowing through the exhaust system of the internal combustion engine and evaporating the condensed water in the condensate collecting unit And may be further provided.

  According to this configuration, the condensed water collected in the condensed water collecting part via the condensed water discharge pipe is heated using the exhaust heat of the exhaust flowing through the exhaust system. Thereby, the condensed water collected in the condensed water collecting portion can be positively evaporated, so that the condensed water does not accumulate in the internal passage for a long time, and corrosion of the inner wall surface of the cylinder block can be suppressed. Here, when the turbine of the turbocharger is arranged in the exhaust system of the internal combustion engine, the heat exchanger may recover the exhaust heat of the exhaust gas flowing into the turbine. As in this configuration, the condensate drain pipe is connected to a hole opened in the side wall on the exhaust side of the cylinder block, so that the condensate collection part is close to the heat source (exhaust pipe, turbocharger turbine, etc.). In doing so, the piping structure of the condensed water discharge pipe does not become complicated, which is preferable.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  According to the present invention, it is possible to provide an internal combustion engine that can be quickly warmed up during a cold start and that includes a more compact EGR device.

1 is a diagram illustrating a schematic configuration of a longitudinal section of an engine according to Embodiment 1. FIG. 1 is a schematic configuration diagram of a horizontal cross section of an engine according to Embodiment 1. FIG. It is explanatory drawing for demonstrating the EGR internal channel | path in the 1st modification of Example 1. FIG. It is explanatory drawing for demonstrating the EGR internal channel in the 2nd modification of Example 1. FIG. FIG. 6 is a diagram illustrating a schematic configuration of a longitudinal section of an engine according to a third modification of the first embodiment. It is a figure which shows schematic structure of the longitudinal cross-section of the engine which concerns on Example 2. FIG. FIG. 10 is an explanatory diagram for explaining a connection location with each EGR gas introduction port and a connection location with an introduction pipe in an EGR internal passage in an engine horizontal cross section according to Embodiment 2; FIG. 6 is a diagram illustrating a schematic configuration of a longitudinal section of an engine according to a third embodiment.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the component parts described in the present embodiment are not intended to limit the technical scope of the invention only to those unless otherwise specified.

  FIG. 1 is a diagram illustrating a schematic configuration of a longitudinal section of an engine according to the present embodiment. In FIG. 1, an engine 1 is an engine in which four cylinders are arranged in series, and includes a cylinder block 2 and a cylinder head 4 fastened on the cylinder block 2. The cylinder block 2 is formed with four cylinder bores 2a arranged in series. Here, in the cylinder block 2, the inner peripheral surface (inner peripheral wall) forming the cylinder bore 2a is referred to as “cylinder bore wall surface 2b”, and the outer wall surface is referred to as “cylinder block outer wall surface 2c”. The longitudinal section of the engine 1 refers to a section when the engine 1 is cut along the axial direction of the cylinder bore 2a.

  In the cylinder bore 2a, a piston 3 is slidably provided along the cylinder bore wall surface 2b. The piston 3 is connected to the crankshaft via a connecting rod, and the crankshaft rotates as the piston 3 reciprocates. Hereinafter, when used as the vertical direction of the cylinder bore wall surface 2b and the vertical direction of the cylinder block 2, the axial direction of the cylinder bore 2a, that is, the sliding direction of the piston 3, unless otherwise specified.

  An intake port 11 and an exhaust port 12 are formed in the cylinder head 4, and an intake valve 13 and an exhaust valve 14 are respectively provided in these. Further, an intake manifold 15 and an exhaust manifold 16 are connected to the intake port 11 and the exhaust port 12, respectively. An intake pipe 17 is connected to the intake manifold 15, and an exhaust pipe 18 is connected to the exhaust manifold 16. An exhaust gas purification device (not shown) is provided in the middle of the exhaust pipe 18, and a muffler is further connected downstream.

The engine 1 is provided with an ECU (Electronic Control Unit) 10 which is an electronic control unit for controlling the driving state according to the driving conditions of the engine 1 and the driver's request. The ECU 10 includes a CPU that executes various arithmetic processes related to the control of the engine 1, a ROM that stores programs and data necessary for the control, a RAM that temporarily stores the arithmetic results of the CPU, and a signal between the outside. It is configured with input / output ports for inputting / outputting.

  The engine 1 includes an exhaust gas recirculation device (EGR device) 20 that extracts part of the exhaust gas flowing through the exhaust system of the engine 1 as EGR gas and recirculates it to the intake system. The EGR gas recirculated (recirculated) to the intake system by the EGR device 20 is sucked (introduced) into each cylinder bore 2 a while being mixed with the air flowing through the intake pipe 17. The EGR gas contains an inert gas component that does not burn itself and has a high heat capacity unlike water and carbon dioxide. Therefore, when the EGR gas is contained in the air-fuel mixture, the combustion temperature of the air-fuel mixture is lowered, thereby reducing the amount of nitrogen oxide (NOx) generated.

  Next, an EGR passage (reflux passage) that is a flow path of the EGR gas when the EGR device 20 recirculates the EGR gas will be described. As shown in the drawing, an EGR internal passage 22 to be described later is formed in the cylinder block 2 between the cylinder bore wall surface 2b and the cylinder block outer wall surface 2c so as to extend in the axial direction of the cylinder bore 2a. FIG. 2 is a schematic configuration diagram of a horizontal cross section of the engine according to the present embodiment. The horizontal section is a section orthogonal to the longitudinal section of the engine. Specifically, FIG. 2 schematically shows a cylinder block cross section in a direction perpendicular to the axis of the cylinder bore. As shown in the figure, the EGR internal passage 22 covers (encloses) the cylinder bore wall surface 2b along the cylinder bore row (cylinder row) while being close to the cylinder bore wall surface 2b inside the cylinder block 2.

  Further, since the EGR internal passage 22 extends in the axial direction of the cylinder bore 2a (the vertical direction of the cylinder bore wall surface 2b) as shown in FIG. 1, it is formed in a cylindrical shape along the cylinder bore row. Further, the upper end edge portion 22a of the EGR internal passage 22 has a height that is substantially the same as the upper end edge portion of the cylinder bore wall surface 2b in the vertical direction of the cylinder bore wall surface 2b (the axial direction of the cylinder bore 2a). The lower end edge 22b is formed so that its height coincides with a portion relatively close to the lower end edge of the cylinder bore wall surface 2b. Therefore, the EGR internal passage 22 extends in the axial direction of the cylinder bore wall surface 2b so as to cover most of the lower end edge portion from the upper edge portion of the cylinder bore wall surface 2b.

The cylinder head 4 and the cylinder block 2 are formed with an EGR gas introduction port 23 that is a communication hole that communicates the upper end edge 22 a of the EGR internal passage 22 and the exhaust port 12. Specifically, the EGR gas introduction port 23 passes through the fastening portion between the cylinder head 4 and the cylinder block 2. Further, as shown in FIG. 2, the EGR gas introduction port 23 is formed corresponding to each cylinder bore 2a, and the exhaust port 12 and the EGR internal passage 22 are connected to each other at the upper end edge portion 22a. Communicate.

  The side wall surface of the cylinder block outer wall surface 2c on the intake side (the side where the intake pipe 17 is disposed) is denoted by reference numeral 2c 'and is referred to as "cylinder block intake side outer wall surface". Referring to FIG. 1, a through-hole 24 is formed in the cylinder block intake side outer wall surface 2 c ′ to communicate the vicinity of the lower end edge portion 22 b in the EGR internal passage 22 and the outside of the cylinder block. The through hole 24 is connected to the other end of an introduction pipe 25 having one end connected to the intake pipe 17. That is, the introduction pipe 25 communicates the intake pipe 17 with the vicinity of the lower end edge 22 b in the EGR internal passage 22 through the through hole 24.

  In the middle of the introduction pipe 25, an EGR cooler 26 that cools the EGR gas that flows through the introduction pipe 25 and an EGR valve 27 that adjusts the flow rate of the EGR gas that flows through the introduction pipe 25 are provided from the side close to the through hole 24. In order. The EGR valve 27 is connected to the ECU 10 via electrical wiring, and the amount of EGR gas is adjusted by controlling the opening degree of the EGR valve 27 by the ECU 10.

  In the EGR device 20 configured as described above, a part of the exhaust gas flowing through each exhaust port 12 flows into each EGR gas introduction port 23 and is introduced as EGR gas into the EGR internal passage 22 from the upper end edge 22a. Is done. The EGR gas guided to the EGR internal passage 22 flows toward the through hole 24 opened in the cylinder block intake side outer wall surface 2c ′ while directly exchanging heat with the cylinder bore 2a. It flows out to the introduction pipe 25 through the through hole 24. Thereafter, the EGR gas that has flowed into the EGR cooler 26 is cooled in the EGR cooler 26, and the flow rate is adjusted by the EGR valve 27, and then introduced into the intake pipe 17.

  Therefore, the EGR passage (reflux passage) when the EGR gas recirculates is, in this embodiment, the EGR gas introduction port 23, the EGR internal passage 22, (through hole 24), the introduction pipe 25, the EGR cooler 26, and the EGR valve. 27. In this embodiment, the EGR internal passage 22 corresponds to the internal passage in the present invention.

  By the way, when the engine 1 is quickly warmed up at the time of cold start, in the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 2008-082307), the internal passage is disposed only below the water jacket, Heat exchange was performed between the cooling water flowing through the water jacket and the EGR gas. For this reason, a portion where heat exchange between the EGR gas and the cooling water is performed locally, which may hinder the rapid performance of warming up of the engine 1 at the time of cold start.

  On the other hand, according to the structure of the engine 1 according to the present embodiment, the EGR internal passage 22 is in the axial direction of the cylinder bore 2a so as to cover most of the region from the upper end edge to the lower end edge of the cylinder bore wall surface 2b. Therefore, it is possible to efficiently raise the temperature of the entire cylinder bore 2a. Therefore, the engine 1 can be quickly warmed up at the cold start, and the friction loss can be reduced.

Further, since the EGR gas is cooled by direct heat exchange with the cylinder bore 2a, the generation of NOx in the engine 1 can be reduced. In this embodiment, since the cooling effect of the EGR gas can be expected when passing through the EGR internal passage 22, it is not necessary to increase the cooling capacity of the EGR cooler 26 so much. That is, since the EGR cooler 26 does not require a large cooling capacity, the EGR cooler 36 can be made more compact. Therefore, it is possible to reduce the size of the EGR device 20 and reduce the manufacturing cost.

  Further, in this embodiment, a part of the EGR passage is constituted by the EGR internal passage 22 formed in the cylinder block 2, so that space saving and compactness of the piping structure of the EGR device 20 are realized. Further, the exhaust gas flowing through the exhaust port 12 is introduced into the EGR internal passage 22 through each EGR gas introduction port 23 formed inside the cylinder head 4 instead of the external passage disposed outside the cylinder block 2. The piping structure of the EGR device 20 can be made simpler. Further, by opening the through-hole 24 to which the introduction pipe 25 is connected to the cylinder block intake side outer wall surface 2c ′ (compared to the case of opening to the exhaust side outer wall surface), the piping structure of the introduction pipe 25 is complicated. Therefore, the EGR device can be made compact.

  Next, a modified example of the present embodiment will be described. FIG. 3 is an explanatory diagram for explaining an EGR internal passage in the first modification. Specifically, like FIG. 2, a cylinder block cross section in a direction orthogonal to the axis of the cylinder bore is schematically shown. Reference numerals 2a # 1 to 2a # 4 in the drawing are shown separately from the first cylinder to the fourth cylinder. 3, the EGR internal passage 32 covers the cylinder bore wall surface 2b along the cylinder bore row (cylinder row) while being close to the cylinder bore wall surface 2b, like the EGR internal passage 22 shown in FIGS. In addition, the cylinder bore 2a extends in the axial direction.

  Here, the difference will be mainly described. A partition wall 33 extending in the vertical direction of the cylinder bore 2a is provided at a boundary portion between 2a # 2 and 2a # 3 in the EGR internal passage 32. The EGR internal passage 32 is divided into a region on the 2a # 1 and 2a # 2 side and a region on the 2a # 3 and 2a # 4 side with the partition wall 33 as a boundary. Here, if the former is the first EGR internal passage 32a, a part of the exhaust discharged from the cylinder bores 2a # 1 and 2a # 2 is introduced into the first EGR internal passage 32a as EGR gas. On the other hand, if the latter is the second EGR internal passage 32b, a part of the exhaust discharged from the cylinder bores 2a # 3 and 2a # 4 is introduced into the second EGR internal passage 32b as EGR gas.

  In the EGR device according to the first embodiment, the EGR gas in the EGR internal passage 24 is introduced into the intake pipe 17 through the single through hole 24 and the introduction pipe 25. On the other hand, in the first modified example, the inside of the EGR is constituted by two introduction pipes 35a and 35b, specifically, a cooler non-installation introduction pipe 35a in which the EGR cooler 26 is not installed and a cooler installation introduction pipe 35b in which the EGR cooler 26 is installed. The EGR gas in the passage 32 is returned to the intake pipe 17.

  In FIG. 3, a through hole 34a similar to the through hole 24 shown in FIG. 1 is opened in the cylinder block intake side outer wall surface 2c 'in the vicinity of the boundary between 2a # 1 and 2a # 2. Similarly, a through hole 34b equivalent to the through hole 24 is opened in the intake side outer wall surface 2c 'in the vicinity of the boundary between 2a # 3 and 2a # 4. The arrangement positions of the through holes 34 a and 34 b in the vertical direction of the cylinder bore wall surface 2 b are the same as those of the through hole 24. Here, the cooler non-installation introduction pipe 35a communicates the intake pipe 17 with the vicinity of the lower edge portion of the first EGR internal passage 32a through the through hole 34a. Further, the cooler installation introducing pipe 35b communicates the intake pipe 17 with the vicinity of the lower edge portion of the second EGR internal passage 32b through the through hole 34b.

The respective opening degrees of the EGR valve 27a arranged in the cooler non-installation introduction pipe 35a and the EGR valve 27b arranged in the cooler installation introduction pipe 35b are controlled by the ECU 10 in accordance with the operating state, operating conditions, etc. of the engine 1. Is done. That is, the ratio of the EGR gas that bypasses the EGR cooler 26 in the EGR gas recirculated to the engine 1 is adjusted according to the operating state, operating conditions, and the like of the engine 1.

  By the way, the purpose of introducing the EGR gas into the intake pipe 17 without passing the EGR cooler 26 (after bypassing) is to suppress the temperature of the intake gas sucked into the engine 1 from becoming excessively low. be able to. This is because if the temperature of the intake gas becomes excessively low, the amount of HC emissions from the engine 1 increases. In this first modification, the EGR gas introduced into the intake pipe 17 via the cooler non-installation introduction pipe 35a (bypassing the EGR cooler 26) is the cylinder bore 2a when flowing through the first EGR internal passage 32a. The EGR gas flowing through the first EGR internal passage 32a is kept warm. Specifically, a heat insulating layer is provided on the wall surface of the cylinder block 2 forming the first EGR internal passage 32 so that the first EGR internal passage 32 has a heat insulating structure. In the figure, the heat insulating layer formed along the wall surface of the cylinder block 2 is represented by oblique hatching. According to this, it is possible to keep the temperature of the EGR gas flowing through the first EGR internal passage 32a, and the temperature of the EGR gas introduced into the intake pipe 17 via the cooler non-installation introduction pipe 35a does not become too low. . Accordingly, the temperature of the intake gas sucked into the engine 1 is suppressed from becoming excessively low, and the amount of HC emissions from the engine 1 can be reduced.

  The EGR gas introduced into the intake pipe 17 after passing through the EGR cooler 26 undergoes heat exchange with the cylinder bores 2a # 3 and 2a # 4 when passing through the second EGR internal passage 32b. Of course, early warm-up of the engine 1 at the time of cold start is secured. In the present modification, the EGR internal passage 32 constituted by the first EGR internal passage 32a and the second EGR internal passage 32b corresponds to the internal passage in the present invention.

  Moreover, in this modification, although the heat insulation layer is formed in the 1st EGR internal channel | path 32a which covers cylinder bore 2a # 1 and 2a # 2, you may form a heat insulation layer in another part. For example, the cylinder bores 2a # 1 and 2a # 4 located at both ends in the arrangement direction of the cylinder bores 2a are more easily cooled from the outside than the 2a # 2 and 2a # 3 located inside. Therefore, in the EGR internal passage, a heat insulating layer is formed in a portion that covers the cylinder bores 2a # 1 and 2a # 4 that are easily cooled by the cold air from the outside, and other portions (portions that cover the cylinder bores 2a # 2 and 2a # 3). It is also possible not to form a heat insulating layer. According to this, it becomes possible to reduce the temperature difference between the cylinder bores 2a, and the occurrence of problems such as deformation of the cylinder bore 2a is suppressed.

  FIG. 4 is an explanatory diagram for explaining an EGR internal passage in the second modification. Here, it demonstrates centering on difference with the 1st modification shown in FIG. In this modification, the EGR internal passage is formed so as to surround only the cylinder bores 2a # 1 and 2a # 4 that are easily cooled by the external cold air. Reference numerals 42a and 42b denote EGR internal passages that cover the cylinder bores 2a # 1 and 2a # 4, respectively. That is, each of the EGR internal passages 42a and 42b is close to the wall surface forming each of the cylinder bores 2a # 1 and 2a # 4 and covers this, and extends in the axial direction of the cylinder bore 2a.

A part of the exhaust gas flowing through the exhaust port 12 is introduced into the EGR internal passages 42a and 42b via the EGR gas introduction ports 23 corresponding to the cylinder bores 2a # 1 and 2a # 4. Further, as illustrated, the through hole 34a to which the cooler non-installation introduction pipe 35a is connected is formed in a portion corresponding to the cylinder bore 2a # 1 in the intake side outer wall surface 2c ′ of the cylinder block. Further, the through hole 34b to which the cooler installation introduction pipe 35b is connected is formed in a portion corresponding to the cylinder bore 2a # 4 in the intake side outer wall surface 2c ′ of the cylinder block. Here, since the EGR gas that has passed through the EGR internal passage code 42a is introduced into the intake pipe 17 without being cooled by the EGR cooler 26, in this modification, the cylinder block 2 that forms the EGR internal passage 42a. A heat insulating layer (represented by oblique hatching as in FIG. 3) is formed on the wall surface. As a result, the temperature of the intake gas sucked into the engine 1 is suppressed from becoming excessively low, and an increase in the HC emission amount is suppressed.

  Reference numeral 46 in the figure indicates a so-called water jacket (represented by lattice hatching in the figure). In this figure, the water jacket 46 is formed along the cylinder bores 2a # 2 and 2a # 3, and the cooling water circulates in the inside thereof. In the present modification, the cylinder bores 2a # 2 and 2a # 3 located on the inner side in the arrangement direction of the cylinder bores 2a tend to be relatively high in temperature, so that heat exchange is performed with the cooling water circulating in the water jacket 46. Make it. Thereby, it can suppress that the temperature difference between cylinder bores 2a # 1-2a # 4 becomes large too much. Reference numerals 43a and 43b in the drawing are partition walls that partition the EGR internal passages 42a and 42b from the water jacket 46.

  FIG. 5 is a diagram illustrating a schematic configuration of a longitudinal section of an engine according to a third modification. As illustrated, in this modification, the EGR valve 27 is provided (incorporated) inside the cylinder block 2 instead of the introduction pipe. This configuration is advantageous from the viewpoint of space saving of the EGR device 20. Further, in this configuration, the EGR valve 27 can be installed upstream of the EGR passage (a position closer to the EGR gas introduction port 23 that is an EGR gas outlet is defined as the upstream side). Therefore, for example, the exhaust system volume of the engine 1 in a state where the EGR valve 27 is closed by the ECU 10 can be reduced. Here, the smaller the exhaust system volume in the state where the EGR valve 27 is closed, the larger the pulsation of exhaust gas generated by the opening operation of the exhaust valve 14, that is, the fluctuation range of the exhaust pressure. Therefore, when the configuration according to this modification is applied to an engine equipped with a turbocharger, it is preferable because the supercharging pressure of intake air can be increased using the pulsation effect of exhaust gas.

  Next, Example 2 in the present embodiment will be described. FIG. 6 is a diagram illustrating a schematic configuration of a longitudinal section of the engine according to the present embodiment. Components that are the same as those in FIGS. 1 and 2 are given the same reference numerals, and detailed description thereof is omitted. The exhaust pipe 18 is provided with an NOx storage reduction catalyst (hereinafter referred to as “NOx catalyst”) 52. The NOx catalyst 52 occludes NOx in the exhaust when the oxygen concentration of the inflowing exhaust gas is high, and occludes when the oxygen concentration of the inflowing exhaust gas decreases and a reducing agent (for example, fuel) is present. It has a function of reducing NOx.

  The cylinder head 4 is provided with a fuel addition valve 53 that adds fuel as a reducing agent into the exhaust gas flowing through the exhaust port 12. In the fuel addition valve, an injection hole for injecting fuel faces the exhaust port 12. In this embodiment, the fuel addition valve 53 is provided only in the exhaust port 12 connected to the cylinder bore 2a # 4, but it may be provided in another exhaust port. The fuel addition valve 53 is connected to the ECU 10 through electrical wiring, and the ECU 10 performs control related to fuel addition. The fuel addition from the fuel addition valve 53 is performed, for example, when NOx reduction processing for reducing NOx stored in the NOx catalyst 52 and sulfur poisoning recovery processing for recovering sulfur poisoning by releasing SOx. Since these processing contents themselves are well-known matters, a detailed description thereof is omitted here.

The fuel addition valve 53 in the exhaust port 12 is disposed downstream of the connection position between the exhaust port 12 and the EGR gas introduction port 23. As a result, the added fuel added to the exhaust when adding fuel from the fuel addition valve 53 is suppressed from flowing into the EGR gas introduction port 23 together with the exhaust. That is, the added fuel is introduced into the intake pipe 17 together with the EGR gas, and the deterioration of the combustion of the engine 1 due to this is suppressed. Further, according to this configuration, the fuel addition valve 53 can be attached to the cylinder head 4 while preventing the added fuel from entering the intake system. Therefore, the added fuel can be sufficiently dispersed in the exhaust gas before the added fuel is introduced into the NOx catalyst 52. In this embodiment, the fuel addition valve 53 is provided in the exhaust port 12 in relation to the NOx catalyst 52. However, for example, when a selective reduction type NOx catalyst is disposed in the exhaust pipe 18, the fuel addition valve 53 is provided. Instead of this, a urea addition valve may be installed.

  Next, the EGR internal passage 22 according to the present embodiment will be described. Since the EGR gas flowing through the EGR internal passage 22 is cooled by heat exchange with each cylinder bore 2a, condensed water (exhaust condensed water) may be generated. In the present embodiment, the wall surface of the cylinder block 2 forming each cylinder bore 2a is made of aluminum, and the corrosion resistance is not so high in terms of material characteristics. On the other hand, the introduction pipe 25 is made of stainless steel and has excellent corrosion resistance compared to the cylinder block 2. Here, if the condensed water generated in the EGR internal passage 22 accumulates in the EGR internal passage 22 for a long time, the cylinder block 2 may be corroded.

  Therefore, in the present embodiment, the lower end edge portion 22b (hereinafter referred to as “bottom portion”) of the EGR internal passage 22 is provided so that the condensed water generated in the EGR internal passage 22 is reliably discharged from the through hole 24 to the introduction pipe 25. (Also referred to as FIG. 6). Here, the “height” represents a level of height in the vertical direction of the cylinder bore wall surface 2b, that is, the axial direction of the cylinder bore 2a.

  FIG. 7 illustrates the connection locations (reference characters A to D) with the respective EGR gas introduction ports 23 and the connection locations (reference symbol E) to the introduction pipes 24 in the EGR internal passage 22 in the engine horizontal cross section according to the present embodiment. It is explanatory drawing for doing. That is, exhaust gas is introduced into the EGR internal passage 22 from each of the connection points A to D from the EGR gas introduction port 23 corresponding to the cylinder bores 2a # 1 to 2a # 4. The EGR gas in the EGR internal passage 22 is discharged from the connection point E to the introduction pipe 25 connected to the through hole 24. Here, when the height of the bottom part of the EGR internal passage 22 at the connection points A to E is represented by Ah to Eh, in the present embodiment, the height Eh of the bottom part related to the connection point E corresponds to the bottom part related to the other part. It is set to be lower than any of the heights (Ah, Bh, Ch, Dh).

  More specifically, the EGR internal passage 22 is formed such that the height of the bottom of the EGR internal passage 22 is higher at a location (point) farther from the connection location E in the horizontal cross section of the cylinder. When comparing the height of the bottom of the EGR internal passage 22 in each of Ah, Bh, Ch, and Dh, since the connection points B and C are farthest from the connection point E, the height of the bottom in these Bh and Ch. Is the highest. Moreover, since the connection location A is located between the connection locations B and E, Ah is lower than Bh and higher than Eh. Here, it inclines so that the height of a bottom part may become low gradually toward E from the connection location B. FIG. Similarly, since the connection point D is located between the connection points C and E, Dh is lower than Ch and higher than Eh. In the present embodiment, the bottom portion is inclined from the connection point D to E so that the height of the bottom portion gradually decreases.

  From the above, the connection point E with the introduction pipe 25 in the EGR internal passage 22 has the lowest bottom height in the EGR internal passage 22, and therefore the condensed water generated in the EGR internal passage 22. Can be led to the connection point E.

Further, in this embodiment, at the connection point E between the introduction pipe 25 and the EGR internal passage 22, the lowest portion of the edge 24 a of the through hole 24 (hereinafter referred to as “edge lowest part”) and the EGR internal passage 22. The positional relationship in the vertical direction of both cylinder bores 2a is set so that the height with the lower end edge 22b (bottom) is equal. According to this, the lowermost edge portion of the through hole 24 and the lower end edge portion 22b (bottom portion) of the EGR internal passage 22 in the vertical direction of the cylinder bore wall surface 2b.
Therefore, the condensed water collected at the connection point E can be smoothly discharged to the introduction pipe 25. Therefore, it is possible to prevent the condensed water from being accumulated at the lower end edge portion 22b (bottom portion) of the EGR internal passage 22 for a long period of time, and to prevent the cylinder block 2 from corroding. In addition, since the introduction pipe 25 in the present embodiment is made of stainless steel having excellent corrosion resistance, there is no possibility that the introduction pipe 25 is corroded by the condensed water discharged to the introduction pipe 25.

  Next, Example 3 in the present embodiment will be described. FIG. 8 is a diagram illustrating a schematic configuration of a longitudinal section of the engine according to the present embodiment. The engine 1 in this embodiment is a turbocharged engine having a turbocharger. Reference numeral 51 denotes a turbocharger turbine, which is disposed in the exhaust pipe 18. The engine 1 according to the present embodiment is different from the second embodiment in that the engine 1 includes a condensed water evaporation mechanism 60 that evaporates condensed water generated in the EGR internal passage 22 by using exhaust heat.

  On the side wall surface on the exhaust side of the cylinder block outer wall surface 2c, that is, the surface facing the cylinder block intake side outer wall surface 2c ′ (hereinafter referred to as “cylinder block exhaust side outer wall surface” and denoted by reference numeral 2c ″) A through hole (hereinafter referred to as “condensate drain hole”) 61 is opened. The condensed water discharge hole 61 opens in the cylinder block exhaust-side outer wall surface 2 c ″ so as to pass through the lower end edge 22 b (bottom) of the EGR internal passage 22 and the outside of the cylinder block 2. More specifically, the cylinder bores 2a of both the cylinder bores 2a are equal so that the lowest part of the edge of the condensed water discharge hole 61 and the lower end edge 22b (bottom part) of the EGR internal passage 22 are equal. A positional relationship with respect to the axial direction is set. Further, in the horizontal cross section of the engine 1, the condensed water discharge hole 61 is disposed in the vicinity of the boundary between the cylinder bores 2 a # 2 and 2 a # 3 in the EGR internal passage 22.

  Further, one end of a condensed water discharge pipe 62 is connected to the condensed water discharge hole 61. As described above, since the lower end edge portion 22b of the EGR internal passage 22 and the lowermost edge portion of the condensed water discharge hole 61 have the same height, the condensed water generated in the EGR internal passage 22 passes through the condensed water discharge hole 61. It is smoothly discharged to the condensed water discharge pipe 62. A condensed water collecting part 63 is connected to the other end side of the condensed water discharging pipe 62, and condensed water collected through the condensed water discharging pipe 62 is stored in the condensed water collecting part 63. Yes.

  Reference numeral 64 denotes a heat exchanger that recovers exhaust heat of the exhaust gas flowing into the turbine 51 and evaporates the condensed water in the condensed water collecting unit 63. The heat exchanger 64 includes a heat medium circulation path 65 and is configured to be able to exchange heat between the heat medium flowing in the heat medium circulation path 65 and the exhaust gas flowing into the turbine 51. Furthermore, the heat medium circulation path 65 is connected to the condensed water collecting portion 63 so as to be able to exchange heat.

  The condensed water evaporation mechanism 60 in this embodiment is configured by the condensed water discharge hole 61, the condensed water discharge pipe 62, the condensed water collecting portion 63, the heat exchanger 64, and the heat medium circulation path 65 described above. According to the condensate evaporation mechanism 60 configured as described above, the condensate accumulated in the condensate collection unit 63 is heated and evaporated using the exhaust heat of the exhaust flowing into the turbine 51. Therefore, the condensed water is not accumulated in the lower end edge portion 22b of the EGR internal passage 22 over a long period of time, and corrosion of the cylinder block 2 can be suppressed.

  In this configuration, the gas generated by the evaporation of the condensed water stored in the condensed water collecting portion 63 is returned again into the EGR internal passage 22 via the condensed water discharge pipe 62. The gas may be returned to the EGR internal passage 22 through a communication passage connecting the condensed water collecting portion 63 and the EGR internal passage 22 separately from the discharge pipe 62.

1 Engine 2 Cylinder block 2a Cylinder bore 2b Cylinder bore wall surface 2c Cylinder block outer wall surface 4 Cylinder head 11 Intake port 12 Exhaust port 17 Intake pipe 18 Exhaust pipe 20 EGR device 22 EGR internal passage 23 EGR gas introduction port 24 Through hole 25 Intake pipe 27 EGR valve

Claims (4)

An internal combustion engine comprising an EGR device that extracts a part of exhaust gas from an exhaust system of the internal combustion engine as EGR gas and recirculates the exhaust gas to an intake system,
The EGR passage through which the EGR device recirculates EGR gas is a passage formed between the cylinder bore wall surface and the cylinder block outer wall surface and capable of exchanging heat between the EGR gas flowing through the cylinder block wall surface and the cylinder bore wall surface, An internal combustion engine provided with an EGR device, characterized in that it includes an internal passage that is close to the cylinder bore wall surface and covers the cylinder bore wall surface and extends in the cylinder bore axial direction. The EGR passage further includes:
EGR gas that is formed inside the cylinder head and cylinder block, communicates the upper end edge of the internal passage or its vicinity and the exhaust port, and introduces a part of the exhaust gas flowing through the exhaust port into the internal passage as EGR gas. Introduction port,
The lower end edge of the internal passage or its vicinity is communicated with the intake pipe of the internal combustion engine via a hole opened in the intake side wall of the cylinder block, and the EGR gas in the internal passage is introduced into the intake pipe. An introduction tube;
An internal combustion engine comprising the EGR device according to claim 1, comprising: In the connection part of the introduction pipe and the internal passage, the height of the lowest part of the edge of the hole and the lower edge of the internal passage is equal,
And the height of the lower end edge of the internal passage at the connection location with the introduction pipe is made lower than the height of the lower end edge of the internal passage at the connection location with the EGR gas introduction port. An internal combustion engine comprising the EGR device according to claim 2. A condensed water discharge pipe for discharging condensed water in the internal flow path to the outside of the cylinder block through a hole opened in a side wall on the exhaust side of the cylinder block;
A condensed water collecting part connected to the condensed water discharge pipe, in which condensed water is stored via the condensed water discharge pipe;
A heat exchanger that recovers heat of exhaust flowing through the exhaust system of the internal combustion engine and evaporates the condensed water in the condensed water collecting section;
An internal combustion engine comprising the EGR device according to any one of claims 1 to 3, further comprising:

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