JP2015124692A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arrange an EGR cooler without increasing a piping space, and to improve fuel consumption.SOLUTION: A cooling water outlet 26 and an inflow port 16a of a water pump 10 provided at a cylinder head 2 are connected by a return pipe 27, and an EGR cooler 30 is interposed in the middle of the return pipe 27. Therefore, the whole amount of cooling water passes through the EGR cooler 30. As the EGR cooler 30 does not require dedicated piping, even when there is no extra space in an engine room, the EGR cooler 30 is installed, and fuel consumption can be improved through the improvement of filling efficiency. By arranging the EGR cooler 30 between a catalyst converter 19 and the water pump 10, it can be suppressed that auxiliary machines such as the water pump 10 and the like are affected by heat damage of the catalyst converter 19.

Description

  The present invention relates to an internal combustion engine including a cooling device and an EGR device.

  An internal combustion engine for a vehicle is generally water-cooled, and cooling water is circulated by a water pump. In this case, when the cooling water passes through the radiator, the cooling water cooled by the radiator flows into the water pump. Therefore, the temperature of the cooling water is the lowest in the pipeline that returns to the water pump.

  On the other hand, recent vehicle internal combustion engines are often provided with an EGR device that recirculates a portion of the exhaust gas to the intake system in order to promote purification of exhaust gas, improve fuel efficiency, and the like. In many cases, a water-cooled EGR cooler that cools the water is provided. In this case, since the capacity of the EGR cooler is small, conventionally, as disclosed in Patent Document 1, for example, a bypass passage for an EGR cooler is provided in the cooling water passage, and the EGR cooler is installed with the cooling water in the bypass passage. It is cooling.

JP 2009-138558 A

  However, providing the bypass passage for cooling the EGR cooler requires providing a pipe dedicated to the EGR cooler, so that not only the structure becomes complicated and the cost increases, but also a space for arranging the bypass passage. Therefore, there is a problem that adjustment with the layout of other members becomes troublesome. In particular, in the case of an internal combustion engine for a vehicle, there is a possibility that the EGR cooler cannot be installed due to the limitation of the space in the engine room.

  The cooling device is provided with a thermo valve that controls the flow of water to the radiator according to the temperature of the cooling water. However, in an internal combustion engine, a timing chain is generally arranged on one end surface side of the cylinder block. Since this is covered with a chain case, an auxiliary machine such as a water pump is arranged on the side of the chain case, and a transmission is often attached to the other end surface of the cylinder block. Usually, the head is provided at a position opposite to the timing chain, and it can be said that the bypass passage for cooling the EGR cooler is often branched from the vicinity of the thermo valve.

  However, if the bypass passage and the EGR cooler are arranged close to the thermo valve, the catalytic converter may have to be shifted to the side of the auxiliary machine, and this causes the auxiliary machine to be easily damaged by the heat of the catalytic converter. There is.

  Furthermore, if a dedicated bypass passage is provided in the EGR cooler, the flow resistance of the cooling water is increased accordingly, so that the torque for driving the water pump is increased and the fuel consumption may be deteriorated.

  The present invention has been made to improve the current situation.

  The internal combustion engine of the present invention has a cooling device in which cooling water circulates by a water pump and an EGR passage for recirculating exhaust gas to an intake system, and the EGR passage is a water-cooled type. An EGR cooler is provided, and the EGR cooler is provided in a return pipe connected to an inlet of the water pump so that the entire amount of cooling water returns to the water pump via the EGR cooler. It has become.

  The present invention includes various configurations. As an example, in the invention of claim 2, in claim 1, the exhaust system is provided with a catalytic converter for purifying exhaust gas, and the EGR cooler is disposed at a portion between the catalytic converter and the water pump and the It is arranged closer to the cylinder block than the catalytic converter.

  In the invention of claim 3, in claim 1 or 2, the EGR cooler has an inflow pipe into which cooling water enters and an outlet pipe from which cooling water comes out fixed by welding or brazing, The end of the outlet pipe is connected to the inlet of the water pump by fitting, while the starting end of the inlet pipe is fixed to the engine body with screws.

  In the present invention, since a dedicated bypass passage is not necessary for the EGR cooler, the cost can be suppressed and the piping space is not increased, so that the freedom of layout of each member can be improved. In addition, the cooling performance of the EGR gas can be significantly improved, and the fuel efficiency can be improved by improving the charging efficiency.

  Even in a vehicle with a narrow engine room and no extra space, the EGR cooler can be arranged to contribute to improving the charging efficiency of the engine, and in this respect, it can also contribute to the improvement of fuel consumption. Furthermore, since an increase in the flow resistance of the cooling water can be prevented, the torque required for driving the water pump can be reduced, and this aspect can also contribute to an improvement in fuel consumption.

  While the water pump is generally driven by an auxiliary drive belt, the catalytic converter is provided in the exhaust passage, but there is often a dead space between the water pump and the catalytic converter. For this reason, when the EGR cooler is arranged between the catalytic converter and the water pump as in claim 2, the dead space can be effectively used to make the internal combustion engine compact.

  Further, since the EGR cooler plays a role of a heat shield member that blocks the heat of the catalytic converter, it is possible to suppress the auxiliary machinery such as the water pump from being damaged by the heat of the catalytic converter. Thereby, the performance of the auxiliary machine can be stabilized and the durability can be improved. Furthermore, since the EGR cooler is disposed on the cylinder block side with respect to the catalytic converter, the cylinder block can also be prevented from receiving the heat of the catalytic converter, which can also improve the charging efficiency and contribute to the improvement of fuel consumption. .

  If the structure of Claim 3 is employ | adopted, since the inflow pipe and the exit pipe are integrated with the EGR cooler, a connection member such as a flange for fixing the inflow pipe and the exit pipe to the EGR cooler becomes unnecessary. As a result, the cost can be reduced and water leakage can be prevented. Further, when the flange is joined, the flange acts as a weight and the pipe is easily damaged by vibration. However, in the invention of claim 3, since the flange is unnecessary, the weight can be reduced and the vibration can be suppressed and the durability can be improved. . In addition, since the outlet pipe is only fitted into the inlet of the water pump, it is easy to assemble, while the inflow pipe is fixed with screws, so that it can be firmly attached.

1 is an overall side view of an internal combustion engine. It is the II-II front view of FIG. FIG. 3 is a sectional view taken along line III-III in FIG. 1. FIG. 4 is an IV-IV view of FIG. 2. (A) is a cross-sectional view taken along the line VA-VA in FIG. 1, and (B) is a cross-sectional view taken along the line VB-VB in FIG. (A) is a sectional view taken along the line VIA-VIA in FIG. 2, (B) is a sectional view taken along the line VIB-VIB in FIG. 2, and (C) is a partially enlarged view of (B).

  Next, an embodiment of the present invention will be described with reference to the drawings. In the following description, the terms “upper”, “left”, “right”, “front” and “rear” are used to specify the direction, but the “upper” and “lower” directions are directions perpendicular to the crankshaft and the cylinder bore. It is the longitudinal direction of the shaft.

(1). Overview The internal combustion engine of the present embodiment includes an engine body having a cylinder block 1 and a cylinder head 2 fixed to the upper surface of the cylinder block 1. It is mounted on the vehicle in a horizontal direction (in FIG. 1, the crankshaft 3 is schematically indicated by a one-dot chain line). A cylinder head cover 4 is fixed to the upper surface of the cylinder head 2, and an oil pan 5 is fixed to the lower surface of the cylinder block 1.

  One chain case 6 is fixed to one of the left and right end surfaces (short side surfaces) of the cylinder block 1 and the cylinder head 2, and the chain case 6, the cylinder block 1, and the cylinder head 1 are connected to each other. A cam shaft drive mechanism such as a timing chain (not shown) is disposed in a space formed therebetween.

  One end of the crankshaft 3 protrudes to the outside of the chain case 6, and as shown in FIG. 2, an accessory driving pulley 7 is fixed to the protruding end, and the accessory driving belt 8 is wound around the accessory driving pulley 7. The alternator 9, the water pump 10, and the air conditioner compressor 11 are driven. The alternator 9, the water pump 10, and the air conditioner compressor 11 are close to the front side of the engine body. For this reason, the accessory drive belt 8 is hung on the back surface of the pulley 12 of the water pump 10. Reference numeral 13 shown in FIG. 2 is a tension pulley.

  The water pump 10 is fixed to the housing 14 that is a part of the chain case 6, the pump cover 15 that is fixed to the housing 10 from the pulley 12 side, and the housing 10 that is fixed to the housing 10 from the opposite side of the pulley 12. The inlet cover 16 is a main element, and cooling water is pumped from the discharge port provided inside to the main gallery provided in the cylinder block 1 by rotation of the built-in blade.

  The inlet cover 16 of the water pump 10 includes an inflow port 16 a parallel to the crankshaft 3, and the inflow port 16 a protrudes on the opposite side to the chain case 6. A transmission 17 is fixed to the other end surface 1 b of the cylinder block 1 opposite to the chain case 6.

  As shown in FIG. 1, an exhaust joint 18 is fixed to a substantially middle portion of the front surface 2 c of the cylinder head 2, and a catalytic converter 19 is integrally provided on the exhaust joint 18. In the present embodiment, the collecting passage (exhaust manifold portion) for collecting the exhaust ports provided for each cylinder is provided inside the cylinder head 2, and only one exhaust port is open on the outer surface of the cylinder head 2. It is.

  Tapered portions are provided at the upper and lower portions of the catalytic converter 19, a joint pipe 20 is connected to the lower end of the lower taper section, and an exhaust pipe 21 is connected to the joint pipe 20. A flange plate 22 is fixed to the joint pipe 20. The flange plate 22 is fixed to the cylinder block 1 via a bracket (shown in the drawing).

  As shown in FIG. 1, when viewed from a direction orthogonal to the crankshaft 3 and the cylinder bore, the catalytic converter 19 is inclined with respect to the vertical line so as to move away from the chain case 6 as it goes downward, and as shown in FIG. When viewed from the axial direction of the crankshaft 3, the crankshaft 3 is inclined with respect to a straight line so as to move away from the cylinder block 1. The catalytic converter 19 is covered from the front with a thin plate insulator (not shown) (covers about a half circumference).

(2). Cooling water piping / EGR device A thermo valve unit 25 for controlling the flow of cooling water is provided on the other end surface 2b of the cylinder head 2 on the side opposite to the chain case 6. Although illustration is omitted, piping is provided from a location of the thermo valve unit 25 to a radiator, a heater, or the like.

  A cooling water outlet 26 is opened at the end of the front surface 2 c of the cylinder head 2 near the thermo valve unit 25, and the cooling water outlet 26 and the inlet 16 a of the water pump 10 are connected by a return pipe 27. On the other hand, an EGR pipe 28 that recirculates exhaust gas to the intake system is connected to the joint pipe 20 of the catalytic converter 19, and the end of the EGR pipe 28 is directly below the cooling water outlet 26 in the front surface of the cylinder head 2. It is connected via a flange plate 29. The cylinder head 2 has an EGR internal passage communicating with the EGR pipe 28, and EGR gas is sent from the EGR internal passage to the intake system via the EGR valve.

  An EGR cooler 30 is inserted in the middle of the EGR pipe 28, and the EGR cooler 30 is also inserted in the return pipe 27. Therefore, the return pipe 27 is separated into an inflow pipe 27 a located on the upstream side of the EGR cooler 30 and an outlet pipe 27 b located on the downstream side of the EGR cooler 30.

  On the other hand, the EGR pipe 28 is also divided by the EGR cooler 30, but the portion upstream of the EGR cooler 30 is fixed to the first portion 28 a fixed to the joint pipe 20 of the catalytic converter 19 and the EGR cooler 30. The two parts 28b are separated from each other and are connected by fastening bolts 33 to the first and second flanges 31 and 32 fixed to the ends thereof. The first portion 28a has a slightly larger diameter than the second portion 28b.

  The portion of the EGR pipe 28 downstream of the EGR cooler 30 is composed of one third portion 28c, and the flange plate 29 is fixed to the end of the third portion 28c. It is fixed to the cylinder head 2 in a simplified manner).

  A flange plate 35 is also fixed to the start end of the inflow pipe 27 a in the return pipe 27, and the flange plate 35 is fixed to the cylinder head 2 with a bolt 36. As shown in FIGS. 3 and 4, the portion of the cylinder head 2 where the return pipe 27 and the EGR pipe 28 are fixed is stepped down to the rear side of the portion where the exhaust joint 18 is fixed ( For example, the portion where the return pipe 27 and the EGR pipe 28 are fixed is used as the reference front surface of the cylinder head 2, and the cover plate is fixed to the reference front surface to form the exhaust collecting passage, and the exhaust joint 18 is connected to the front surface of the cover plate. Fixed.)

  The EGR cooler 30 has an upper and lower surface, a front and rear surface, and a left and right surface, and has a substantially square shape, and is disposed between the catalytic converter 19 and the water pump 10 as shown in FIG. It is arranged so as to be closer to the catalytic converter 19 than 10. Further, as clearly shown in FIG. 5, the EGR cooler 30 is arranged closer to the cylinder block 1 than the catalytic converter 19. Further, the EGR cooler 30 is arranged in a posture closer to the cylinder block 1 as it is farther from the water pump 10 in a plan view.

  Inside the EGR cooler 30, a heat exchanging portion 37 made up of a large number of flat tube-like gas passages (fins) 37a is arranged, and cooling water passes between the adjacent gas passages 37a so that EGR gas Is cooled. In this case, the inflow pipe 27a and the outlet pipe 27b are moved closer to each other and connected to the EGR cooler 30 (that is, the inlet 30a and the outlet 30b are moved closer to each other), and the heat exchanging portion 37 is moved rearward. ing. For this reason, the escape passage 38 is vacant before the heat exchanging portion 37. In addition, escape passages 38 are open on both the left and right sides of the heat exchanging portion 37. The outlet pipe 27b is disposed slightly below the inflow pipe 27a.

  Therefore, some of the cooling water that has flowed into the EGR cooler 30 from the inflow pipe 27a passes through the heat exchanging portion 38 and functions to cool the EGR gas. There is a considerable proportion of cooling water that passes almost without any effect.

  As shown in FIG. 5A, the outlet pipe 27 b of the return pipe 27 has a connection structure that is simply inserted into the inlet 16 a of the water pump 10 from the inside. Therefore, the EGR cooler 30 is disposed on the axial center of the water pump 10.

  In this case, an inward annular protrusion 39 is provided at the opening edge of the inflow port 16a, while an outward annular groove 40 that fits the annular protrusion 39 is formed in the outlet pipe 27b. It is inserted into the inlet 16a by press fitting. Since the annular protrusion 39 and the annular groove 40 are fitted to each other, the outlet pipe 27b is allowed to be slightly inclined with respect to the inflow port 16a, and the sealing performance is secured even if it is slightly inclined.

  It is also possible to press-fit the outlet pipe 27b into the inflow port 16a from the outside. In addition, a seal structure using an O-ring can be employed regardless of whether it is fitted from the inside or from the outside. The inlet cover 16 is fixed to the chain case 6 with bolts (not shown). Therefore, the outlet pipe 27b may be press-fitted into the inlet cover 16 in advance. It is also possible to provide the inflow port 16a integrally with the housing part 14 of the chain case 6. In this case, the inlet 16a may be attached to the chain case 6 in advance.

  The inflow pipe 27a constituting the return pipe 27 is disposed behind the catalytic converter 19, but bends in a substantially square shape when viewed from the side in FIG. 1, and bends in a substantially Z shape when viewed from the front in FIG. Even in the plan view of FIG. Since the inflow pipe 27a is bent in the three-dimensional direction as described above, it can be easily bent and deformed in the vertical direction.

  The third portion 28c constituting the EGR pipe 28 is also bent in a crank shape in the side view of FIG. 1, bent in a substantially Z shape in the front view of FIG. 3, and bent in a square shape in the plan view of FIG. Yes. Accordingly, the third portion 28a is also easily bent and deformed in the vertical direction.

  As shown in FIG. 6A, the starting end of the first portion 28a of the EGR pipe 28 is fixed to the rear surface of the joint pipe 20 of the catalytic converter 19 (the surface facing the cylinder block 1) by welding. Accordingly, the first portion 28a has a substantially L-shaped form in plan view with the horizontally long portion and the longitudinally long portion. As shown in FIG. 6B, the left and right horizontally long portions of the first portion 28a are slightly inclined with respect to the horizontal so that the upstream side is lowered. The front and rear longitudinal portions are also inclined so as to become lower toward the front. Accordingly, the first portion 28a is inclined so as to become lower toward the joint pipe 20 of the catalytic converter 19 as a whole.

  The second portion 28b of the EGR pipe 28 is bent in a substantially L shape in a side view of FIG. 1 and is fixed to the EGR cooler 30 by welding (or brazing). The first flange 31 fixed by welding to the end of the first portion 28a and the second flange 32 fixed by welding to the starting end of the second portion 28b are fastened with bolts 33. The first flange 31 is formed with a female thread that is thicker than the second flange 32. As shown in FIGS. 3 and 4, the bolts 33 are positioned above and below the first portion 28a. For this reason, the rotation operation of the bolt 33 by a wrench (not shown) can be easily performed.

  Further, as clearly shown in FIG. 6C, the annular groove 41 is formed by the first flange 31 and the second flange 32 by scraping the inner peripheral surface of the terminal portion of the first flange 31. Therefore, even if condensed water is generated on the inner surface of the EGR cooler 30 after the operation of the engine is stopped, the condensed water W can be stored in the annular groove 41. The flanges 31 and 32 are preferably made of a highly rust-proof material such as a stainless steel plate.

(3) Summary In the above configuration, since the EGR cooler 30 is inserted in the middle of the return pipe 27, it is not necessary to provide a bypass passage. For this reason, while being able to suppress cost, it is free | released from the restrictions of space and the freedom of arrangement | positioning of this member can be improved. The portion between the catalytic converter 19 (or other auxiliary machine) is often a dead space where there is nothing to be arranged, but in this embodiment, the EGR cooler 30 is arranged in the dead space. The internal combustion engine can be made compact.

  Since there is not much cooling heat required for cooling the EGR gas, it is not necessary to pass the entire amount of cooling water flowing through the return pipe 27 through the heat exchanging portion 37. Therefore, if the escape passage 38 is provided inside the EGR cooler 30 as in the embodiment, it is preferable to prevent an increase in flow resistance. In this case, when the escape passage 38 is provided on the near side as in the embodiment, the heat (radiant heat) of the catalytic converter 19 is absorbed by the water in the escape passage 38, so that the heat shielding property is excellent.

  If the inflow pipe 27a of the return pipe 27 is arranged behind the catalytic converter 19 as in the embodiment, the heat of the catalytic converter 19 is also absorbed by the inflow pipe 27a, so that the cooling performance of the cylinder block 1 is improved. Contributes to improved fuel efficiency.

  When the internal combustion engine is started, the catalytic converter 19 receives the heat of the exhaust gas and greatly expands in the vertical direction, which is the longitudinal direction thereof. For this reason, the 1st part 28a and the 2nd part 28b of the EGR piping 28 move below, and the EGR cooler 30 is pulled downward in connection with this.

  As described with reference to FIG. 5A, the outlet pipe 27b of the return pipe 27 can incline while maintaining the sealing property with respect to the inlet 16a of the water pump 10, and the inflow of the return pipe 27 Since the pipe 27a is easily elastically deformed in the vertical direction, and the third portion 28c of the EGR pipe 28 is also easily deformed in the vertical direction, the EGR cooler 30 easily moves downward following the thermal expansion of the catalytic converter 19. To do. For this reason, the thermal expansion of the catalytic converter 19 does not cause thermal distortion in each pipe, and the durability of the pipe portion can be improved.

  Further, when the engine is stopped, the water remaining in the EGR cooler 30 is cooled by the cooling water, so that condensed water may be generated inside the EGR cooler 30 and drooping down. As described above, since the condensed water W accumulates in the annular groove 41 provided at the position of the mating surface of the first and second flanges 31 and 32, the first portion 28a and the exhaust pipe 21 include the condensed water W containing harmful components. Can be prevented from being attacked. Note that when the engine is started, the condensed water W evaporates due to the heat of the exhaust gas, so that it is not adversely affected after the start.

  In addition, since the first portion 28 a of the EGR pipe 28 has a larger diameter than the second portion 28 b, the condensed water W flows down toward the first portion 28 a without accumulating in the second portion and accumulates in the annular groove 41. That is, the condensed water W does not sag into the annular groove 41 and remains in the second portion 28b. For this reason, the 2nd part 28b is not attacked by the condensed water W, but the condensed water W accumulates in the annular groove 41 formed by the flange plates 31 and 32 having high corrosion resistance.

  The first portion 28a of the EGR pipe 28 can be connected to the front surface or the side surface of the joint pipe 20, but if it is provided on the rear surface of the joint pipe 20 as in the embodiment, the dead space behind the joint pipe 20 is effectively used. There is an advantage that it can be used and bending deformation due to thermal expansion of the catalytic converter 19 can be facilitated.

  In this embodiment, the start end of the return pipe 27 is fixed to the cylinder head 2 at a position opposite to the water pump 10 across the EGR cooler 30 and above the EGR cooler 30, and the start end of the EGR pipe 28 is In addition, it is fixed to the joint pipe 20 of the catalytic converter 19 at a position below the EGR cooler 30 and on the side opposite to the water pump 10. For this reason, the start end of the return pipe 27, the end of the return pipe 27, and the start end of the EGR pipe 28 are arranged to form a vertex of a triangle, and the EGR cooler 30 is arranged inside the triangle. For this reason, the EGR cooler 30 is stably supported without requiring a dedicated bracket. Therefore, it can contribute to cost reduction and weight reduction. In particular, since the return pipe 27 has a large diameter and high rigidity, the EGR cooler 30 can be firmly supported.

  Further, in the EGR cooler 30, the cooling water flows in from the opposite side of the water pump 10 and flows out to the water pump 10, so that the cooling water passes smoothly through the EGR cooler 30. For this reason, the cooling water flows toward the water pump 10 without resistance, and the return pipe 27 does not become long, so that the weight does not increase. In this case, since the end of the inflow pipe 27a is set to be higher than the start end of the outlet pipe 27b, the cooling water also flows from the top to the bottom inside the catalytic converter 19. For this reason, the cooling property of the heat exchange part 37 is high.

  Further, the end of the EGR pipe 28 is higher than the starting end, and there is no portion bent downward in the middle. For this reason, condensed water does not accumulate in the middle of the EGR pipe 28 when the engine is stopped.

  In a multi-cylinder internal combustion engine, it is preferable to provide the exhaust outlet at an intermediate portion of the cylinder row in order to smoothly exhaust the exhaust gas discharged from each exhaust port. In particular, when the exhaust manifold portion is built in the cylinder head 2 as in this embodiment, there is a space limitation. Therefore, it is preferable to simplify the exhaust passage by disposing the exhaust outlet at the middle portion of the cylinder row.

  Therefore, the exhaust joint 18 that is the upper end entrance of the catalytic converter 19 is preferably arranged at the middle part of the cylinder row as in the embodiment, but in this case, the catalytic converter 19 is in a vertical posture in a side view. If so, the arrangement space of the EGR cooler 30 is reduced, so the EGR cooler 30 must be downsized, and the cooling performance may be reduced. Further, when the catalytic converter 19 approaches the chain case 6, the heat received by the auxiliary machine such as the water pump 10 increases and there is a risk that the heat damage will increase.

  On the other hand, when the catalytic converter 19 is tilted away from the chain case 6 as it goes downward as in the embodiment, the exhaust port for exhaust gas is arranged in the middle part of the cylinder row, and the catalytic converter 19 and the chain are arranged. Since the space between the case 6 and the case 6 can be made as large as possible, the EGR cooler 30 can be made as large as possible while ensuring high cooling performance while smoothly discharging the exhaust gas, and the heat received by the auxiliary equipment such as the water pump 10. Harm can also be suppressed.

  Further, as described above, the catalytic converter 19 is inclined so as to move away from the cylinder block 1 as it goes down. However, by adopting such a posture, the EGR cooler 30 is enlarged as much as possible, and the catalytic converter 19 and the cylinder block are arranged. 1 can be arranged. As a result, it is possible to contribute to improving the cooling performance of the EGR gas and suppressing the flow resistance of the cooling water, and to improve the function of preventing the thermal damage of the catalytic converter 19 by the EGR cooler 30.

  In addition, the EGR cooler 30 is disposed close to the catalytic converter 19 between the catalytic converter 19 and the water pump 10. With this configuration, the amount of heat that the EGR cooler 30 receives from the catalytic converter 19 is reduced. Therefore, not only can the temperature of the cooling water be raised at an early stage during start-up to contribute to shortening the warm-up operation time, but also the heat shielding properties for auxiliary machinery can be improved.

  In the present embodiment, the third portion 28 c of the EGR pipe 28 passes toward the cylinder head 2 through the back of the inflow pipe 27 a in the return pipe 27. That is, the inflow pipe 27 a of the return pipe 27 is interposed between the third portion 28 c and the catalytic converter 19. For this reason, it is possible to suppress the EGR gas cooled by the EGR cooler 30 from being heated by the catalytic converter 19. This can also improve the fuel efficiency by improving the charging efficiency.

  The present invention can be embodied in various ways other than the above-described embodiment. For example, the start end of the inflow pipe constituting the return pipe can be connected to a thermo valve unit fixed to the cylinder head. Therefore, the thermo valve unit also constitutes the engine body. A normal exhaust manifold in which branch pipes are assembled may be fixed to the cylinder head.

  In the embodiment, the inflow pipe of the return pipe is fixed to the cylinder head by flange joining. However, while the screw cylinder is protruded from the cylinder head, the flange is bent at the end of the inflow pipe and fitted into the inflow pipe. It is also possible to connect by screwing the nut into the screw cylinder.

  The present invention can be embodied in an internal combustion engine. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Cylinder block 2 Cylinder head 3 Crankshaft 6 Chain case 8 Auxiliary machine drive belt 9 Alternator as an example of auxiliary machine 10 Water pump as an example of auxiliary machine 16 Water pump inlet cover 19 Catalytic converter (catalyst case)
20 Joint Pipe 25 Thermo Valve Unit 27 Return Pipe 27a Inflow Pipe 27b Outlet Pipe 28 EGR Pipe 28a First Part 28b Second Part 28c Third Part 30 EGR Cooler 31, 32 Flange 33 Bolt 37a Gas Passage 37 Heat Exchanger 38 Relief Passage 41 annular groove

Claims (3)

A cooling device in which cooling water is circulated by a water pump, and an EGR passage that recirculates exhaust gas to the intake system, and a water-cooled EGR cooler is provided in the EGR passage,
The EGR cooler is provided in a return line connected to the inlet of the water pump, and the entire amount of cooling water is returned to the water pump via the EGR cooler.
Internal combustion engine. The exhaust system is provided with a catalytic converter for purifying exhaust gas, and the EGR cooler is disposed at a portion between the catalytic converter and the water pump and closer to the cylinder block than the catalytic converter.
The internal combustion engine according to claim 1. In the EGR cooler, an inflow pipe into which cooling water enters and an outlet pipe from which cooling water comes out are fixed by welding or brazing, and the end of the outlet pipe is connected to the inflow port of the water pump by fitting. On the other hand, the starting end of the inflow pipe is fixed to the engine body with screws,
The internal combustion engine according to claim 1 or 2.

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