JP2010084581A - Structure for cooling egr gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide structure for cooling EGR, cooling EGR gas with more compact structure, without any additional heat exchanger for cooling EGR gas. <P>SOLUTION: In the structure for cooling EGR, a pipe connection member which is attached to a cylinder head of an engine and to which a pipe for cooling water is connected, forms a cooling water flow passage extending from the cylinder head to the pipe. The EGR gas passes through the pipe connection member so that the EGR gas is cooled. A groove forming a passage in which EGR gas passes is formed to at least one of joint faces of the cylinder head and the pipe connection member to surround the cooling water flow passage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cooling structure for EGR gas.

  Exhaust gas recirculation (EGR) is known in which a part of the exhaust gas is recirculated to the intake passage. The EGR suppresses the combustion temperature and has an effect of reducing nitrogen oxide (NOx) in the exhaust gas, for example. Here, it is desirable to cool the EGR gas in order to prevent a reduction in intake charge efficiency. In cooling EGR gas, for example, it is known to add a separate heat exchanger using engine cooling water. However, when heat exchangers are added, there are problems that the number of parts increases and engine assembly workability decreases.

  Therefore, a configuration in which an EGR gas cooling function is added to a part of the configuration of the engine cooling system has been proposed. For example, Patent Literature 1 discloses a gas cooler housing in which a part for connecting a cylinder head and a cooling water pipe is formed in a case shape. The gas cooler housing has an EGR gas passage and cools the EGR gas with engine coolant.

JP 2000-248936 A

  However, the gas cooler housing of Patent Document 1 integrally has a tubular portion that penetrates the gas cooler housing and forms a chamber for introducing cooling water around the tubular portion. The gas cooler housing becomes larger. This leads to an increase in the size of the engine.

  An object of the present invention is to provide an EGR gas cooling structure capable of cooling the EGR gas with a more compact configuration without requiring an additional heat exchanger for cooling the EGR gas.

  According to the present invention, the EGR gas is passed through the pipe connecting member that is attached to the cylinder head of the engine and is connected to a pipe for cooling water to form a cooling water flow passage extending between the cylinder head and the pipe. In the EGR gas cooling structure that cools the EGR gas, a groove that forms a passage through which the EGR gas passes is formed in at least one of the mating surfaces of the cylinder head and the pipe connection member. An EGR gas cooling structure characterized by being formed so as to surround a water circulation passage is provided.

  In this cooling structure, the groove forms a space through which the EGR gas passes around the cooling water circulation passage, and the EGR gas is cooled by heat exchange with the cooling water. Therefore, the EGR gas can be cooled without requiring an additional heat exchanger for cooling the EGR gas. Further, by forming the space around the cooling water circulation passage in the mating surface between the cylinder head and the pipe connection member, the EGR gas passage inside the pipe connection member can be shortened, There is no need to provide a cooling water chamber in the pipe connecting member, and the pipe connecting member can be made more compact.

  In the present invention, the groove is formed in both the mating surface of the cylinder head and the mating surface of the pipe connecting member, and the groove of each of the cylinder head and the pipe connecting member is formed in the groove. A plurality of wall portions protruding from the bottom portion may be provided, and the wall portion on the cylinder head side and the wall portion on the pipe connection member side may be alternately provided in a manner spaced apart in the EGR gas flow direction. According to this configuration, since the EGR gas flows in a meandering manner, the effective length of the space through which the EGR gas formed by the groove passes can be increased, and the compactness can be achieved while improving the cooling performance.

  In the present invention, an EGR valve is attached to the pipe connecting member, and the pipe connecting member has a sub-circulation passage that branches from the cooling water circulation passage and guides the cooling water to the EGR valve. May be. According to this configuration, the EGR valve can be cooled more compactly.

  In the present invention, an EGR gas exhaust port communicating with the exhaust port in the cylinder head may be formed on the mating surface of the cylinder head, and the groove may communicate with the EGR gas exhaust port. . According to this configuration, the EGR gas can be introduced into the groove without requiring a separate pipe.

  As described above, according to the present invention, it is possible to provide an EGR gas cooling structure that can cool the EGR gas with a more compact configuration without requiring an additional heat exchanger for cooling the EGR gas.

  FIG. 1 is a block diagram of an engine 100 to which an EGR gas cooling structure A according to an embodiment of the present invention is applied. The engine 100 includes a cylinder block 110 and a cylinder head 120. In FIG. 1, a solid line arrow indicates the flow direction of the cooling water, and a broken line arrow indicates the flow direction of the EGR gas.

  The engine 100 is an in-line four-cylinder gasoline engine in which four cylinders # 1 to # 4 are arranged in a line. In the present embodiment, an in-line four-cylinder gasoline engine is taken as an example, but the present invention can be applied to other types of gasoline engines having different numbers of cylinders and different cylinder arrangements, or other types of engines such as diesel engines. The engine 100 is an engine provided with a valve mechanism in which two intake valves and two exhaust valves are provided per cylinder.

  A water pump 112 is provided at the front of the cylinder block 110 in the cylinder row direction. The water pump 112 is driven by power transmitted from a crankshaft (not shown) of the engine 100 via a power transmission mechanism, and pumps cooling water to the water jacket 111 in the cylinder block 110 and the water jacket 121 in the cylinder head 120. To do. The water pump 112 may be an electric type.

  A pipe connecting member 10 is attached to a rear portion of the cylinder head 120 in the cylinder row direction. The pipe connecting member 10 is a member that connects the cylinder head 120 and the cooling water pipe 115 to form a cooling water circulation passage extending from the cylinder head 120 to the pipe 115. The cooling water flowing through the water jacket 121 in the cylinder head 120 is discharged to the pipe connecting member 10 and flows out to the pipe 115. The pipe 115 branches off in the middle, one being connected to the thermostat 113 and the other being connected to the thermostat 113 via the radiator 114. The thermostat 113 allows the cooling water to flow to the water pump 112 without passing through the radiator 114 when the engine 100 is cold, and allows the cooling water to flow to the water pump 112 via the radiator 114 when the engine 100 is warm. In addition, the structure which attaches the thermostat 113 to the piping connection member 10 is also employable.

  Thus, in the case of the present embodiment, the cooling water flows through the water pump 112 → the water jackets 111 and 121 → the pipe connecting member 10 → (the radiator 114) → the thermostat 113 → the water pump 112 and circulates in the engine 100. Cooling.

  Next, among the exhaust ports 123 in the cylinder head 120, the EGR gas passage 124 communicates with the exhaust port 123 of the cylinder # 4. A part of the exhaust gas flowing through the exhaust port 123 of the cylinder # 4 is introduced into the EGR gas passage 124. In this embodiment, a part of the exhaust gas of the cylinder # 4 is used as the EGR gas, but another cylinder or a part of the exhaust gas of the cylinder may be used as the EGR gas.

  The EGR gas flowing through the EGR gas passage 124 flows from the cylinder head 120 to the pipe connecting member 10 and is cooled by a cooling structure A described later. The EGR gas that has passed through the pipe connecting member 10 is returned to the intake system via the EGR valve 30 and the pipe 126. In the case of this embodiment, the EGR valve 30 is attached to the pipe connection member 10. In this embodiment, the pipe 126 is connected to the intake manifold 125, and EGR gas is introduced from the intake manifold 125 to each intake port 122.

  Next, the EGR gas cooling structure A will be described with reference to FIGS. 2A is a plan view of the vicinity of the pipe connection member 10 in the rear part of the engine 100 in the cylinder row direction, and FIG. 2B is a front view of the vicinity of the pipe connection member 10 in the rear part of the engine 100 in the cylinder row direction. 3A is a front view of the rear part of the cylinder head 120 in the cylinder row direction, and FIG. 3B is a view of the pipe connecting member 10 as viewed from the mating surface 14 side. 4A is a cross-sectional view taken along line XX in FIG. 2B, and FIG. 4B is a cross-sectional view taken along line YY in FIG. 2B.

  A mating surface 20 to which the pipe connecting member 10 is attached is formed at the rear of the cylinder head 120. In the present embodiment, the mating surface 20 of the cylinder head 120 and the mating surface 14 of the pipe connecting member 10 are flat with each other, but may have undulations as long as the shapes of the two match each other.

  The mating surface 20 has a cooling water drain port 21 communicating with the water jacket 121, an EGR gas exhaust port 22 communicating with the EGR gas passage 124, a bottomed groove 23, and a plurality of screw holes 25. Is formed. The groove 23 has a plurality of wall portions 24 (two in this case) protruding from the bottom thereof, and is partitioned into three grooves 23a to 23c.

  The pipe connecting member 10 includes a cylindrical connecting part 11 to which a pipe 115 (FIG. 1) is connected, a cylindrical exhaust part 12 for discharging EGR gas to the EGR valve 30, and cooling water to the EGR valve 30. A sub-drainage 13 for supplying a part and a mating surface 14 serving as a mating surface with the mating surface 20 of the cylinder head 120 are provided.

  A plurality of holes 18 through which a plurality of bolts 41 (FIGS. 2A and 2B) are inserted are formed in the mating surface 14. The bolts 41 are inserted into the holes 18 and screw holes 25 of the mating surface 20. The pipe connection member 10 can be attached to the cylinder head 120 by being screwed to the cylinder head 120.

  The mating surface 14 is also formed with an inlet 15 for cooling water that communicates with the drain 21 at the time of attachment. The inlet 15 and the internal space of the connection portion 11 communicate with each other to form a cooling water circulation passage extending from the cylinder head 120 to the pipe 115 (FIG. 1).

  The sub drainage portion 13 branches from the cooling water circulation passage, and forms a sub circulation passage for guiding the cooling water to the EGR valve 30 as shown in FIG. A return pipe 40 is connected to the EGR valve 30, and the cooling water supplied to the EGR valve 30 is guided to the pipe 115 (FIG. 1) through the return pipe 40. The EGR valve 30 is an electromagnetic control valve that opens and closes according to a command from an ECU (not shown). By supplying cooling water to the EGR valve 30, the actuator can be cooled to obtain a stable operation. In this embodiment, the EGR valve 30 can be cooled with a more compact configuration by attaching the EGR valve 30 to the pipe connection member 10 and supplying the cooling water in this manner.

  Next, a bottomed groove 16 is also formed in the mating surface 14. The groove 16 has a plurality of wall portions 17 (three in this case) protruding from the bottom thereof, and is divided into four grooves 16a to 16d. The groove 16a has, at its end, an EGR gas introduction portion 16a ′ that faces the exhaust port 22 when attached. The groove 16d is formed at its end with a communication hole 16d 'communicating with the internal space in the exhaust part 12.

  As will be described later, the groove 16 and the groove 23 form a space through which EGR gas passes, and the EGR gas exhausted from the exhaust port 22 passes through the exhaust part 12 as shown in FIG. Guided to the EGR valve 30. The EGR valve 30 is an electromagnetic control valve that opens and closes according to a command from an ECU (not shown). When the EGR valve 30 is opened, the EGR gas supplied from the exhaust unit 12 is returned to the intake system via the pipe 126.

  Next, a space (hereinafter also referred to as an EGR gas cooling passage) formed by the groove 16 and the groove 23 through which the EGR gas passes will be described. FIG. 5 is a cross-sectional view taken along line ZZ in FIG. 3A in a state where the pipe connecting member 10 is attached to the cylinder block 120, and is a plan development view of the EGR gas cooling passage. In FIG. 5, the arrow indicates the flow direction of EGR gas.

  The groove 16a communicates with the exhaust port 22, and the EGR gas discharged from the exhaust port 22 is first introduced into the groove 16a. The groove 16a communicates with the groove 23a, the groove 16b communicates with the groove 23a and the groove 23b, the groove 16c communicates with the groove 23b and the groove 23c, and the groove 16d communicates with the groove 23c. For this reason, the EGR gas discharged from the exhaust port 22 flows out from the exhaust part 12 to the EGR valve 30 through the EGR gas cooling passage formed by these grooves.

  Here, as shown in FIGS. 3A and 3B, the groove 16 and the groove 23 are formed so as to surround the cooling water circulation passage formed by the drain port 21 and the inlet 15. Flows around the cooling water. For this reason, heat is exchanged with the cooling water through the cylinder head 120 and the wall of the pipe connecting member 10 to be cooled.

  As described above, in the present embodiment, the grooves 16 and 23 form an EGR gas cooling passage around the cooling water circulation passage, and the EGR gas is cooled by heat exchange with the cooling water. Therefore, the EGR gas can be cooled without requiring an additional heat exchanger for cooling the EGR gas. Further, the EGR gas cooling passage around the cooling water circulation passage is formed on the mating surfaces 20 and 14 between the cylinder head 120 and the pipe connection member 10, so that an EGR gas passage (for example, communication) inside the pipe connection member 10 is formed. The passage in the exhaust part 12 from the hole 16d ′ can be shortened, and it is not necessary to provide a cooling water chamber in the pipe connection member 10, and the pipe connection member 10 can be made more compact.

  In addition, a plurality of wall portions 17 and 24 are provided alternately in the grooves 16 and 23, respectively, in the EGR gas flow direction as shown in FIG. The gas will flow in a meandering manner. As a result, the effective length of the EGR gas cooling passage can be increased, and the size can be reduced while improving the cooling performance.

  The EGR gas cooling passage formed by the groove 16 and the groove 23 surrounds substantially the entire circumference around the cooling water circulation passage as in the present embodiment, so that the cooling performance of the EGR gas can be maximized. However, it is not always necessary to enclose the entire circumference, and it is sufficient to enclose it within a range where necessary cooling performance can be obtained. Moreover, although the cylinder head 120 and the pipe connection member 10 are made of, for example, an aluminum alloy, a material having good thermal conductivity is preferable in terms of heat exchange efficiency.

  In this embodiment, the grooves 16 and 23 are formed in both the cylinder head 120 and the pipe connection member 10, respectively. However, if the groove is formed in one of them and the other is formed in a planar shape that closes the groove, EGR A gas cooling passage can be formed. However, if the grooves are formed on both sides, the volume of the EGR gas cooling passage can be increased, and more EGR gas can be cooled.

  In the present embodiment, the exhaust port 22 is formed on the mating surface 20 of the cylinder head 120 and communicated with the exhaust port 123 via the EGR gas passage 124 in the cylinder head 120. Alternatively, the configuration using an external pipe may lead the EGR gas from the exhaust port 123 or an exhaust manifold (not shown) to the EGR gas cooling passage. However, with the configuration of the present embodiment, EGR gas can be guided to the EGR gas cooling passage without the need for separate external piping, and the number of parts can be reduced and assembly workability can be improved.

1 is a block diagram of an engine 100 to which an EGR gas cooling structure A according to an embodiment of the present invention is applied. FIG. FIG. 2A is a plan view of the vicinity of the pipe connection member 10 in the rear part of the engine 100 in the cylinder row direction, and FIG. 2B is a front view of the vicinity of the pipe connection member 10 in the rear part of the engine 100 in the cylinder row direction. (A) The front view of the cylinder row direction rear part of the cylinder head 120, (b) is the figure which looked at the piping connection member 10 from the mating surface 14 side. (A) is sectional drawing in alignment with line XX of FIG.2 (b), (b) is sectional drawing in alignment with line YY of FIG.2 (b). FIG. 4 is a cross-sectional view taken along line ZZ in FIG. 3A in a state in which a pipe connecting member 10 is attached to a cylinder block 120.

Explanation of symbols

A Cooling structure 10 Piping connection members 14, 20 Mating surfaces 16, 23 Groove 100 Engine 115 Piping 120 Cylinder head

Claims (4)

Cooling the EGR gas by passing the EGR gas through a pipe connecting member that is attached to the cylinder head of the engine and is connected to a pipe for cooling water to form a cooling water circulation passage between the cylinder head and the pipe. In the EGR gas cooling structure
A groove forming a passage through which EGR gas passes is formed on at least one of the mating surfaces of the cylinder head and the pipe connecting member so as to surround the cooling water circulation passage. EGR gas cooling structure. Forming the groove on both the mating surface of the cylinder head and the mating surface of the pipe connecting member;
A plurality of wall portions protruding from the bottom of the groove are provided in the groove of each of the cylinder head and the pipe connecting member,
2. The cooling of EGR gas according to claim 1, wherein the wall portion on the cylinder head side and the wall portion on the pipe connection member side are alternately provided separated in the EGR gas flow direction. Construction. An EGR valve is attached to the pipe connection member,
3. The EGR gas cooling structure according to claim 1, wherein the pipe connecting member has a sub-circulation passage that branches from the cooling water circulation passage and guides the cooling water to the EGR valve. 4. An EGR gas exhaust port communicating with an exhaust port in the cylinder head is formed on the mating surface of the cylinder head.
4. The EGR gas cooling structure according to claim 1, wherein the groove communicates with the EGR gas exhaust port. 5.

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