JP4258357B2 - Engine exhaust gas recirculation system - Google Patents

Description

  The present invention relates to an exhaust gas recirculation device for an engine that recirculates a part of exhaust gas discharged from an engine to an intake passage side. The present invention relates to an exhaust gas recirculation device for an engine.

  The vehicle engine is equipped with an exhaust gas recirculation device that lowers the combustion temperature by recirculating a part of the exhaust gas to the intake passage side and reduces the intake load to reduce NOX in the exhaust gas and reduce fuel consumption. There is something. In this exhaust gas recirculation device (EGR device), a part of the exhaust manifold on the exhaust path side of the engine body and a position near the branch portion of the intake manifold on the intake path side in order to recirculate a part of the exhaust gas as EGR gas to the intake path. And an exhaust gas introduction path. Here, an EGR valve is provided in the exhaust gas introduction path, and the EGR valve is controlled to be opened and closed by a controller so that the EGR gas flows to the intake side by a flow rate corresponding to the engine operating region.

  When such an exhaust gas recirculation device is attached to the engine body, the EGR gas flows from the exhaust path side of one side wall formed along the longitudinal direction of the engine body to the intake path side of the other side wall through the exhaust gas introduction path. Will be allowed to. In this case, the exhaust gas introduction path is arranged so as to traverse the vicinity of the longitudinal end of the engine body in the width direction of the engine body. It is necessary to secure it.

  For example, in the engine exhaust gas recirculation device shown in FIG. 13, the exhaust gas is taken out as EGR gas from the exhaust passage 120 of the end cylinder 110 located on one end side in the longitudinal direction X of the engine body 100, and this is taken as the cylinder head. 130 is introduced to the intake passage 190 side through an EGR pipe 170 provided with a gas passage 150 in the cylinder head and an EGR valve 160 formed in the lower wall 140. Here, the cylinder head gas passage 150 is branched and extended from the exhaust port 180, is bent and then extends in the width direction Y of the engine body 100 and communicates with the EGR pipe 160 on the outside of the cylinder head. The width direction extending portion 150a is formed at the tip portion 130a of the cylinder head on the tip side of the head bolt 200 provided for the end cylinder 110.

In addition, an outflow opening 220 is formed in the end outer wall 230 of the cylinder head tip portion 130a, and this communicates with the water jacket 210 in the cylinder head and the thermostat 240 for switching the cooling water flow path fixed to the end outer wall 230. is doing. In this case, the flow path member for the exhaust gas recirculation device outside the engine main body 130 can be reduced and the number of parts can be reduced. Japanese Patent Laid-Open No. 2001-200762 (Patent Document 1) is provided with a diesel engine cooling water circulation path for cooling. A thermostat for switching the flow direction of water is housed in a box-shaped case and fixed to one end in the longitudinal direction of the engine body, and a part of the exhaust gas recirculation passage of the exhaust gas recirculation device is provided at the bottom of the case The structure which formed integrally the gas path (pipe) which comprises this is disclosed. Here, the gas passage has a pipe-like portion that extends straight in the width direction of the engine body at the front portion of the engine body and a portion that curves upward on the intake passage side, one end of which is an EGR pipe on the exhaust passage side through a flange. The other end is connected to the EGR pipe on the intake passage side through a flange. Here, the EGR gas is cooled by the cooling water in the case 11 at a pipe-like portion extending straight, so that the intake efficiency can be increased by suppressing the rise in the intake air temperature.

Japanese Patent Laid-Open No. 2001-200762

  By the way, in the exhaust gas recirculation device disclosed in FIG. 13, the length in the longitudinal direction X of the cylinder head 130, that is, the engine main body 100 is increased by forming the width direction extending portion 150a in the cylinder head front end portion 130a. There is a problem of becoming. On the other hand, when the exhaust gas recirculation device of Patent Document 1 is used, there is no problem in the length of the engine body in the longitudinal direction, but the exhaust gas introduction path extends from the exhaust manifold side to the intake manifold side. The entire exhaust gas introduction path is provided in the outer portion of the engine body.

  For this reason, in particular, the EGR pipes on the exhaust path and the intake path side are disposed on the outer side in the width direction of the engine body, and the installation space for the engine as a whole becomes relatively large, and there is a problem in securing the installation space. In addition, the pipe-like gas path is formed only by integrally forming the upper wall portion at the lower portion of the case, and the portions other than the upper wall are formed to protrude. In this respect, the installation space becomes large, and the cooling action of the EGR gas by the cooling water cannot be sufficiently obtained, and the cooling efficiency is low. Furthermore, since the pipe-like gas passage here does not provide a sufficient cooling action, the gas temperature of the EGR gas is not sufficiently lowered, and the intake efficiency is liable to be lowered. Need to lower. In particular, when a resin manifold is employed, the necessity of a cooler for EGR gas is particularly increased, and this also causes a problem that the installation space is increased.

  The present invention has been made on the basis of the above-described problems, and the object is to reduce the installation space, to make the engine body compact, and, secondarily, the cooling action of the EGR gas by the cooling water. It is an object of the present invention to provide an exhaust gas recirculation device for an engine that can be obtained sufficiently.

An exhaust gas recirculation device for an engine according to claim 1 of the present invention is a water-cooled engine in which an exhaust passage is formed on one side wall formed along the longitudinal direction of the engine body and an intake passage is formed on the other side wall. In an exhaust gas recirculation device for an engine that is mounted and introduces a part of the exhaust gas in the exhaust passage as EGR gas to the intake passage through the exhaust gas introduction passage, it is integrally attached to the side wall at the end of the engine body in the longitudinal direction. comprising a thermostat inlet chamber for flowing cooling water from the engine body through the outlet port of said end side wall is formed on said base and having a base portion that is, the exhaust gas introduction passage is branched from the exhaust passage and the engine body gas path reaching the longitudinal ends end opening formed in the sidewall of the extending out the engine body, groups of the thermostat communicating with the end opening Comprising a thermostat in the gas path having a thermostat-side opening formed in the mounting surface to the end side wall, an intake path side flow path member for introducing the EGR gas from the thermostat within the gas passage to the intake passage, the thermostat The inner gas passage is formed so as to extend in the longitudinal direction of the engine body from the thermostat side opening communicating with the end opening, and a main portion of the cross section of the flow path forms a pipe-like wall portion and swells into the inflow chamber. An extension path formed, a curved path for deflecting the flow of EGR gas from the longitudinal direction of the engine body in the width direction, an end outflow opening connecting the curved path to the intake path side flow path member extending to the intake path, It is characterized by having.

According to the first aspect of the present invention, a gas passage in the engine body is provided which extends from the exhaust passage and extends to the engine body so as to reach an end opening formed in an end wall in the longitudinal direction of the engine body. A gas passage in the thermostat is formed in the inside, and an intake passage side flow passage member for introducing EGR gas from the gas passage in the thermostat into the intake passage is provided. The gas passage in the thermostat uses the EGR gas from the gas passage in the engine body to the engine body. In the exhaust gas introduction path, a flow path portion for flowing the exhaust gas from the exhaust path side to the intake path side is formed at the end in the longitudinal direction of the engine body. Instead, it can be replaced with a gas path in the thermostat in the casing of the thermostat. In particular, when it passes through the extension path of the base of the thermostat, it is formed so as to protrude along the inflow chamber that is the cooling water flow path, so that the EGR gas is cooled by the cooling water through the flow path wall of the extension path with the cooling water of the inflow chamber. It is cooled efficiently. Further, even when passing through the curved path or the width direction extending path, the cooling is efficiently performed by the cooling water in the discharge chamber and the return chamber in the thermostat, and the cooling efficiency of the EGR gas is further increased. For this reason, the length of the engine body in the longitudinal direction can be shortened. In addition, since the EGR gas cooling efficiency is increased, the exhaust gas introduction path can be made relatively short. In this respect as well, the engine can be made compact. Further, since the EGR gas is cooled by the cooling water, the EGR gas intake system can be reduced. The amount of inhalation of fuel increases relatively, and the fuel efficiency in the lean burn operation area is improved.

1 and 2 show an exhaust gas recirculation device for an engine as an embodiment of the present invention.
This engine exhaust gas recirculation device 1 is provided in a water-cooled engine 2 mounted on an automobile (not shown). In the engine 2, a lower water jacket 5 and an upper water jacket 6 are formed in each of a cylinder block 3 that forms a main part of the engine body 201 and a cylinder head 4 on the upper side.

  The cylinder block 3 sequentially arranges a plurality of cylinders S in the longitudinal direction X at predetermined intervals, and forms a lower water jacket 5 around the outer periphery of the cylinder S at a portion covered by the upper wall wb and the outer wall wc. . Moreover, the cylinder block 3 is formed with a lower pump side opening 7 through which the cooling water from the water pump 9 flows into the lower water jacket 5 via the branch path R1 at one end in the longitudinal direction X of the outer wall wc. 5 is formed on the other end side of the upper wall wb. The end communication port 8 for guiding the cooling water 5 to the upper water jacket 5 of the cylinder head 4 is formed.

  The cylinder head 4 is formed with a lower wall wh that overlaps the upper wall wb of the cylinder block 3, and an outer peripheral wall wr is formed so as to rise from the periphery. Further, as shown in FIG. 2, the intake port 11 on the intake path IN side extending in the width direction Y of the cylinder head 4, that is, toward the left and right outer peripheral wall sides wr, is provided at each cylinder facing portion of the lower wall wh. And the exhaust port 12 on the exhaust path EX side are formed so as to extend away from each other. Moreover, the upper water jacket 6 is formed at a position where it does not interfere with the intake and exhaust ports 11 and 12. The cylinder head 4 is mounted with a valve system (not shown), and then a head cover (not shown) is superimposed on the upper portion of the outer peripheral wall and integrally coupled.

  Further, the cylinder head 4 has an upper pump side opening through which cooling water from the water pump 9 flows into the upper water jacket 6 via the upper branch path R2 on the end side wall 401 which is one end side in the longitudinal direction X of the outer peripheral wall. 13 and the upstream outlet 14 through which the cooling water of the upper water jacket 6 flows out from the end side wall 402 which is the outer peripheral wall of the other end of the cylinder head 4 is formed. Here, the cylinder block 3 and the cylinder head 4 are integrally fastened by a plurality of head bolts 15. In this case, communication auxiliary holes 16 are formed at a plurality of locations across the upper wall wb and the lower wall wh of both, and the cooling water of the lower water jacket 5 is supplied to the upper water jacket 6 in the same manner as the end communication port 8. Works to introduce.

  An exhaust manifold 17 is integrally coupled to the outer wall surface on the side wall 403 side (lower side wall in FIG. 1) formed along the longitudinal direction (same as the longitudinal direction of the engine body) X of the cylinder head 4, and the other side wall 404 side. An intake manifold 18 is integrally coupled to the outer wall surface (the upper side wall in FIG. 1). The exhaust manifold 17 joins the exhaust gas from the exhaust port 12 of each cylinder at the junction and flows out to the exhaust pipe side (not shown). The intake manifold 18 draws intake air from the intake pipe (not shown) to the intake port of each cylinder. It branches to 19 and is supplied. A joint portion 211 of an EGR pipe 21 that forms a part of an exhaust gas introduction path Rg described later is formed in the branch section 181 of the intake manifold 18, and EGR gas that is exhaust gas from the exhaust gas introduction path Rg is branched into the branch section 181. It is formed so that it can flow into the intake air inside.

As shown in FIG. 1, the casing 23 of the thermostat 22 is integrally attached to the end side wall 402 of the cylinder head 4.
As shown in FIG. 1, the casing 23 has a base portion 231 having a flange that overlaps the end side wall 402 and a lid portion 232 that is integrally coupled to the projecting end side thereof, and the upstream outlet 14 on the end side wall 402 side therein. Are formed in this order by arranging an inflow chamber 24 opposite to the discharge chamber 26, a discharge chamber 26 that houses the temperature-sensitive switching valve 25, and a return chamber 28 into which cooling water from the radiator 27 in the vicinity of the engine 2 flows. Moreover, the thermostat gas passage 29 is formed without interfering with these chambers.

A first valve seat 31 is formed between the inflow chamber 24 and the discharge chamber 26 of the thermostat 22, and a second valve seat 32 is formed between the return chamber 28 and the discharge chamber 26.
The temperature-sensing switching valve 25 includes a core shaft 34 supported on the casing 23 side via a mounting bracket 33, a temperature-sensing portion 35 that is externally fitted so as to be movable relative thereto, and an outer shaft 36 that is integrally coupled to the temperature-sensing portion 35. First and second valve bodies 37 and 38 to be supported, and a spring 39 for closing and energizing the outer shaft 36 and the second valve seat 328 side are provided.

Here, at the normal temperature, the temperature sensing switching valve 25 is held at the cold position P0, the first valve body 37 opens the first valve seat 31, and the inflow chamber 24 and the discharge chamber 26 are communicated. On the other hand, when the temperature of the cooling water exceeds a predetermined temperature (for example, 85 ° C.), the second valve body 38 opens the second valve seat 32, and the cooling water returned to the return chamber 28 is discharged from the cooling path 43 including the radiator 27. The switching operation is performed so as to flow into the chamber 26.
Further, a discharge port 42 for discharging the cooling water reaching the discharge chamber 26 to the cooling water suction passage 41 is formed in the base portion 231 of the casing 23 at a portion facing the discharge chamber 26, and a radiator is formed at the portion facing the inflow chamber 24. An introduction port 44 for introducing cooling water is formed in the cooling path 43 communicating with 27.

Next, the exhaust gas recirculation device 1 constituting the main part of the present invention will be described.
An exhaust gas recirculation device 1 for an engine takes out exhaust gas as EGR gas from an exhaust passage EX of an end cylinder s located on one end side in the longitudinal direction X of the engine body, and the inside of the cylinder head forming the exhaust gas introduction passage Rg The gas passage 45, the thermostat gas passage 29, and the EGR pipe 21 provided with the EGR valve 46 are introduced into the intake passage IN side.

Here, the cylinder head gas passage 45 formed in the lower wall wh (see FIG. 3) of the cylinder head 4 branches off from the exhaust port 12 and extends in the engine body longitudinal direction X, and the end opening 47 of the end side wall 402. To reach.
A base 231 of the thermostat 22 is fastened to the end side wall 402 with a bolt (not shown). At this time, the upstream outlet 14 of the end side wall 402 is formed to communicate with the inflow chamber 24 of the thermostat 22, and the end opening 47 communicates with the thermostat side opening 48 formed in the base 231.

  A thermostat gas passage 29 is formed in the base 231 of the thermostat 22. The gas path 29 in the thermostat has an extended path 491 extending in the engine body longitudinal direction X from the thermostat side opening 48, a curved path 492 for deflecting EGR gas from the engine body longitudinal direction X to the width direction X, and a curve. A width extending passage 493 extending from the passage 492 toward the intake passage IN which is the engine body width direction X, and an end outflow opening 494 connected to the EGR pipe 21 extending the EGR gas from the width extending passage 493 to the intake passage IN Is provided.

  As shown in FIG. 4, the extension path 491 is formed in a straight shape along the inflow chamber 24 in the base portion 231, and most of the cross section of the flow path is covered with a pipe-shaped wall portion so as to swell into the inflow chamber 24. Formed. For this reason, since the EGR gas in the extension passage 491 that is the gas passage in the thermostat is formed in the vicinity of the inflow chamber 24 that forms the cooling water passage, the EGR gas is cooled by the cooling water and the cooling efficiency of the EGR gas is increased.

The EGR pipe 21 serves as an intake passage side flow path member, and includes an EGR valve 46 in the middle, and is formed so that the end outlet opening 494 and the joint portion 211 of the branch portion 181 of the intake manifold 18 can communicate with each other. The EGR valve 46 adjusts the flow rate of the EGR gas by the control means 51 according to the engine operating state.
The operation of such an engine exhaust gas recirculation device will be described.
When the water pump 9 is driven during the cold start of the engine 2, the low-temperature cooling water flows into the lower water jacket 5 of the cylinder block and the upper water jacket 6 of the cylinder head 3, and enters the thermostat inflow chamber via the upstream outlet 14. Reach 24.

At this time, since the inflow chamber 24 and the discharge chamber 26 communicate with each other, the cooling water returns to the water pump 9 from the cooling water suction passage 41 as it is, and the warming-up operation is performed. When the warm-up is completed, the inflow chamber 24 and the discharge chamber 26 are shut off, the return chamber 28 and the discharge chamber 26 communicate with each other, the cooling water in the inflow chamber 24 flows to the radiator 27 in the cooling path 43, and the cooled cooling water The return chamber 28 passes through the discharge chamber 26 and returns to the water pump 9 from the cooling water suction passage 41 to perform a heat radiation operation.
While such cooling water is circulated, a part of the exhaust gas in the exhaust passage EX passes through the exhaust gas introduction passage Rg, the flow rate is regulated by the EGR valve 46, and the joint of the branch portion 181 of the intake manifold 18 is connected. From the portion 211 to the intake passage IN, contributing to NOx reduction and fuel efficiency improvement.

  At this time, the control means 51 takes in the engine rotational speed signal and the engine load signal, calculates the EGR gas supply rate corresponding to the operating range according to the map, etc., and calculates the EGR valve 46 corresponding to the calculated EGR gas supply rate. The EGR valve 46 is controlled so as to maintain the opening degree. At this time, EGR gas corresponding to the opening degree of the EGR valve 46 passes through the exhaust gas introduction passage Rg, and particularly protrudes along the inflow chamber 24 which is a cooling water flow passage when passing through the extension passage 491 at the base of the thermostat. Therefore, the EGR gas is efficiently cooled by the cooling water in the inflow chamber 24 via the flow path wall of the extension passage 491. Further, even when passing through the curved path 492 and the width direction extending path 493, the cooling is efficiently performed by the cooling water in the discharge chamber 26 and the return chamber 28 in the thermostat, and the cooling efficiency of the EGR gas is further increased. For this reason, the exhaust gas introduction path Rg can be made relatively short, the engine can be made compact in this respect, the intake amount of the EGR gas into the intake system is relatively increased, and the fuel consumption in the lean burn operation region is further improved. The

  In addition, the gas path 29 in the thermostat is formed with a curved path 492 and a width direction extending path 493 for deflecting the EGR gas from the gas path in the engine body from the longitudinal direction X to the width direction X of the engine body. Of the introduction passage Rg, a flow passage portion (for example, the gas passage 150 in the cylinder head in FIG. 13) for flowing the exhaust gas from the exhaust passage EX side to the intake passage IN side is not formed at the end in the engine body longitudinal direction X. The gas path 29 in the thermostat in the thermostat can be replaced. For this reason, the length of the engine body in the longitudinal direction X can be shortened.

  In the engine 2 described above, all of the cooling water in the lower water jacket 5 of the cylinder block 3 flows to the upper water jacket 6 of the cylinder head 4, but in some cases, as shown by a two-dot chain line in FIG. A configuration may be adopted in which the lower outflow opening 60 is formed in the block 3 and the cooling water from the same portion is joined to the cooling path 43 via the second thermostat 70 and the bypass path 43a (see FIGS. 2 and 7).

Note that FIG. 2 schematically shows a view in which the lower outflow opening 60 opens directly to the side end of the cylinder block 3. Here, in the thermostat 61 as the second embodiment, specifically, as shown in FIG. 5, the end communication port 8a extends to the cylinder head 4 side through a flow path (not shown), and flows out downward at the tip. The opening 60a is formed, and the second thermostat 70 on the cylinder head 4 side is provided there.
Such a thermostat 61 including the second thermostat 70 is attached to the engine 2 of FIG. 1 in place of the thermostat 22 described above, so that the redundant description on the engine body side is omitted.

  As shown in FIGS. 5, 7, and 8, the thermostat 61 according to the second embodiment has a base portion 611 that is fastened to an end side wall 402 by a bolt (not shown). A lid 612 is integrally coupled to the protruding end side of the base 611, and an inflow chamber 24a, a discharge chamber 26a, and a return chamber 28a (see FIG. 7) are arranged in this order. The inflow chamber 24 a communicates with the cooling path 43 on the radiator 27 side via the introduction port 44 a, the discharge chamber 26 a communicates with the suction path 41 on the pump 9 side via the discharge port 42 a, and the return chamber 28 a always communicates with the cooling path 43. To do.

As shown in FIG. 5, the upstream outlet 14 of the end side wall 402 communicates with the inflow chamber 24 a of the thermostat 61, and the end opening 47 communicates with a thermostat side opening 48 a formed in the base 611.
A thermostat internal gas passage 49 a is formed in the base 611 of the thermostat 61. The gas path 49a in the thermostat includes an extension path 491a extending from the thermostat side opening 48a in the engine body longitudinal direction X, a curved path 492a for deflecting EGR gas from the engine body longitudinal direction X to the width direction X, and a curved path A width direction extension passage 493a extending from the air passage 492a toward the intake passage IN which is the engine body width direction X, and an end outflow opening 494a connected to the EGR pipe 21 extending from the EGR gas of the width direction extension passage 493a to the intake passage IN Prepare.

  As shown in FIG. 8, the extension path 491a is formed in a straight shape along the inflow chamber 24a in the base 611, and is formed so that most of the flow path wall portion in the cross section of the flow path bulges out the inflow chamber 24a. . For this reason, the EGR gas in the extension passage 491a which is the gas passage 49a in the thermostat is cooled by the cooling water in the inflow chamber 24a forming the cooling water passage, and the cooling efficiency of the EGR gas is increased.

The EGR pipe 21a is an intake passage side flow path member, and is provided with an EGR valve 46a in the middle to communicate the end outlet opening 494a and the joint portion 211 of the intake manifold 18. The EGR valve 46 adjusts the flow rate of the EGR gas by the control means 51 according to the engine operating state.
In addition, in order to display the whole shape and three-dimensional shape of the thermostat 61, each cross-sectional shape was specifically displayed from FIG. 7 to FIG. In FIG. 5, reference numeral 65 denotes a heater pipe connection end, and reference numerals 66 and 67 denote a heater pipe return end.

The operation of the engine exhaust gas recirculation device 1a will be described.
At the time of cold start of the engine 2, the cooling water returns to the water pump 9 from the cooling water suction passage 41 through the inflow chamber 24a and the discharge chamber 26a and is warmed up. When the warming is completed, the cooling water in the inflow chamber 24 is supplied to the radiator 27, It returns to the water pump 9 from the cooling water suction passage 41 through the return chamber 28a and the discharge chamber 26a, and is radiated.

  While such cooling water is circulated, a part of the exhaust gas in the exhaust passage EX is regulated in flow rate by the EGR valve 46 via the exhaust gas introduction passage Rg provided with the thermostat gas passage 49a. 181 flows into the intake passage IN from the joint portion 211 and contributes to NOx reduction and fuel consumption improvement.

  At this time, the control means 51 obtains the opening degree of the EGR valve 46 corresponding to the EGR gas supply rate corresponding to the operating region, and controls the EGR valve 46 so as to maintain the opening degree. At this time, since the EGR gas passes through the exhaust gas introduction path Rg, and particularly when passing through the extension path 491a of the thermostat gas path 49a, the flow path wall of the extension path 491a projects along the inflow chamber 24a. The EGR gas is efficiently cooled by the cooling water in the inflow chamber 24a. Further, even when passing through the curved path 492a and the width direction extending path 493a, the cooling is efficiently performed by the cooling water in the discharge chamber 26a and the return chamber 28a in the thermostat, and the cooling efficiency of the EGR gas is further increased. For this reason, the exhaust gas introduction path Rg can be made relatively short, the engine can be made compact in this respect, the intake amount of the EGR gas into the intake system is relatively increased, and the fuel consumption in the lean burn operation region is further improved. The

  In the above description, the exhaust gas recirculation device of the engine is used for a gasoline engine, but it can be similarly applied to a diesel engine.

1 is an overall schematic configuration diagram of an exhaust gas recirculation device for an engine as one embodiment of the present invention. 1 is an overall schematic configuration diagram of an engine including an exhaust gas recirculation device for an engine as an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view in the flow channel direction in the vicinity of the upper outlet opening of FIG. 1. FIG. 2 is an enlarged cross-sectional view in the flow path cross-sectional direction near the upper outflow opening of FIG. 1. It is a top view of the thermostat used by the modification of this invention. It is a front view of the thermostat of FIG. It is the EE sectional view taken on the line of the thermostat of FIG. FIG. 7 is a cross-sectional view of the thermostat of FIG. 6 taken along the line FF. It is CC sectional view taken on the line of the thermostat of FIG. It is the DD sectional view taken on the line of the thermostat of FIG. It is the GG sectional view taken on the line of the thermostat of FIG. It is a reverse view of the thermostat of FIG. It is a principal part schematic block diagram of the exhaust-gas recirculation apparatus of the conventional engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine cooling device 2 Engine 21 Intake path side flow path member 22, 61 Thermostat 23 Casing 29 Thermostat gas path 492 Curved path 402 End wall surface 45 Engine main body gas path EX Exhaust path IN Intake path Rg Exhaust gas introduction path X Engine main body Longitudinal direction Y width direction

Claims (1)

It is mounted on a water-cooled engine in which an exhaust passage is formed on one side wall formed along the longitudinal direction of the engine body and an intake passage is formed on the other side wall, and a part of the exhaust gas in the exhaust passage is exhausted as EGR gas. In the exhaust gas recirculation device of the engine that is introduced into the intake passage through the gas introduction passage,
Comprising a thermostat inlet chamber for flowing cooling water from the engine body through the outlet port of said end side wall is formed on said base and having a base portion which is integrally attached to the longitudinal end side wall of the engine body ,
The exhaust gas introduction path is branched from the exhaust path, extends to the end opening formed in the side wall in the longitudinal direction of the engine body, and communicates with the end opening. A thermostat gas passage having a thermostat side opening formed at a base portion of the thermostat to be tightly coupled to an end side wall; and an intake passage side flow path member for introducing EGR gas from the thermostat gas path into the intake passage. ,
The gas path in the thermostat is formed to extend in the longitudinal direction of the engine body from the thermostat side opening communicating with the end opening, and the main part of the flow passage section forms a pipe-like wall portion and bulges into the inflow chamber. An extension path formed to flow, a curved path for deflecting the flow of EGR gas from the longitudinal direction of the engine body in the width direction, and an end outflow connecting the curved path to the intake path side flow path member extending to the intake path An exhaust gas recirculation device for an engine having an opening.

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