JP2009127557A - Exhaust structure of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust structure for an internal combustion engine capable of avoiding a situation in which abnormal noise is generated by pressure of exhaust gas flowing in an Ai port even if a secondary air supply device is not equipped when a cylinder head is shared between an engine equipped with the secondary air supply device and an engine not equipped with the same. <P>SOLUTION: When the cylinder head 1 having an Ai port opening part 51 formed adjacently to an exhaust port opening part 41, a gasket 2 including a first opening zone corresponding to the exhaust port opening part 41, a second opening zone corresponding to the Ai port opening part 51, and a continuous opening zone over these opening zones is applied. Consequently, exhaust gas flowing through the Ai port can be discharged toward a branch pipe 31 through each opening zone, and vibration of the gasket 2 due to pressure of exhaust gas can be prevented. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust structure of an internal combustion engine mounted on an automobile or the like. In particular, the present invention relates to an improvement in structure for enhancing versatility of a cylinder head having a passage for introducing secondary air into an exhaust system.

  2. Description of the Related Art Conventionally, in an internal combustion engine (hereinafter sometimes referred to as an engine) mounted on an automobile or the like, a catalyst (for example, a three-way catalyst) is disposed in an exhaust passage, and CO (carbon monoxide), HC in exhaust gas is disposed. There is provided an exhaust purification device that purifies exhaust gas by reducing (hydrocarbon) and NOx (nitrogen oxide) components. Further, among engines equipped with such an exhaust purification device, a secondary air supply device (AI (Air Injection) system) that supplies secondary air to the exhaust system of the engine in order to promote the exhaust purification function of the catalyst. Is also known (for example, see Patent Document 1 and Patent Document 2 below).

  Examples of the secondary air supply device include a secondary air supply passage for supplying secondary air into the exhaust port of the cylinder head, and an air pump for supplying air to the secondary air supply passage. And an on-off valve disposed on the downstream side of the air pump for switching the open / close state of the secondary air supply passage. Then, air (secondary air) from the air pump is supplied into the exhaust port through the secondary air supply passage, and the oxygen concentration in the exhaust system is increased to oxidize HC and CO in the exhaust gas. It is designed to promote exhaust gas purification.

  By the way, depending on the type of engine, there are those equipped with the secondary air supply device and those not equipped with the secondary air supply device. This is for the purpose of complying with, for example, exhaust gas regulations for automobiles, and an engine equipped with the secondary air supply device is required in areas where exhaust gas regulations are severe.

  As described above, it is necessary to manufacture an engine equipped with a secondary air supply device and a non-equipped engine according to the exhaust gas regulations. In this case, these different types of engines are installed on the secondary air supply device. Manufacturing with completely different parts depending on the presence or absence leads to an increase in production cost. For this reason, it is common practice to share components even in different engines. For example, common use of cylinder heads.

  When the cylinder head is to be shared in this way, first, considering that the secondary air supply device is mounted, an exhaust port and a secondary air supply passage (hereinafter referred to as Ai port) are connected to the exhaust system of the cylinder head. May be called). Then, if the cylinder head provided with two types of ports in the exhaust system is applied to an engine not equipped with a secondary air supply device in order to share parts, the Ai port is blocked. It is necessary to keep.

As a method for closing the Ai port, for example, a configuration in which the Ai port is closed by a flange portion of an exhaust manifold connected to the cylinder head can be cited. Moreover, the structure which obstruct | occludes Ai port with the gasket interposed between a cylinder head and the flange part of an exhaust manifold is also mentioned. That is, in the case where the secondary air supply device is mounted, the Ai port is not closed by the flange portion or gasket of the exhaust manifold. Allows the introduction of air. On the other hand, in the case where the secondary air supply device is not mounted, the Ai port is not used because the Ai port is closed by the flange portion or gasket of the exhaust manifold. Thereby, the said cylinder head can be made common with respect to each engine (an engine which mounts a secondary air supply apparatus, and an engine which is not mounted) from which a kind differs.
JP-A-7-119454 JP 2004-76588 A

  However, as described above, when the Ai port is closed by the flange portion or gasket of the exhaust manifold, the pressure (exhaust pulsation) of the exhaust gas flowing into the Ai port during the exhaust stroke of each cylinder is the exhaust manifold. It acts on the flanges and gaskets of these parts and may cause the flanges and gaskets to vibrate. In particular, it is remarkable for those in which the flange portion and the gasket are made thin in order to reduce the weight of the engine.

  Thus, when vibration occurs in the flange portion or gasket, an abnormal noise is generated due to the vibration, which leads to an increase in engine noise, which is not preferable.

  As a method for avoiding such a situation, it is conceivable to increase the thickness of the flange portion and gasket of the exhaust manifold, but this leads to an increase in the weight of the entire engine and the fuel consumption rate deteriorates. In addition, it is conceivable to increase the rigidity by integrally forming a rib or the like on the flange portion of the exhaust manifold, but not only the shape of the flange portion becomes complicated and the production cost increases, but also the rib is formed. It is difficult to secure the space. Further, if the individual cylinder heads are manufactured according to the engine equipped with the secondary air supply device and the engine not equipped with the same, the above problem does not occur, but as described above, the production cost is greatly increased. .

  The present invention has been made in view of such a point, and an object of the present invention is to provide a component (cylinder head) that is shared between an engine on which a secondary air supply device is mounted and an engine on which the secondary air supply device is not mounted. An object of the present invention is to provide an exhaust structure for an internal combustion engine that can avoid a situation in which abnormal noise is generated due to the pressure of exhaust gas flowing into the Ai port even when the secondary air supply device is not installed.

-Solving principle-
The solution principle of the present invention devised to achieve the above object is that when a cylinder head in which an exhaust passage and a secondary air passage are formed is applied to an internal combustion engine not equipped with the secondary air supply device, The shapes of the gasket and the exhaust manifold are improved so that the exhaust gas flowing through the secondary air passage merges with the exhaust gas flowing through the exhaust passage outside the cylinder head. As a result, the pressure of the exhaust gas in the secondary air passage is released to the exhaust passage side, so that the generation of noise due to the pressure of the exhaust gas in the secondary air passage can be suppressed.

-Solution-
Specifically, the present invention relates to an internal combustion engine in which a flange portion of an exhaust manifold is connected via a gasket to a cylinder head in which an air introduction opening of a secondary air passage is formed adjacent to a downstream end opening of the exhaust passage. The exhaust structure is assumed. For the exhaust structure of the internal combustion engine, the gasket includes a first opening region corresponding to the downstream end opening of the exhaust passage, a second opening region corresponding to the air introduction opening of the secondary air passage, and these A continuous opening region for forming a continuous opening between the first opening region and the second opening region is formed.

  When the cylinder head provided with the exhaust passage and the secondary air passage is applied to an internal combustion engine not equipped with a secondary air supply device so as to be applicable to the internal combustion engine equipped with the secondary air supply device due to this specific matter. For the above, the gasket in which the first opening region, the second opening region, and the continuous opening region are formed is used. According to this, when the internal combustion engine is driven, a part of the exhaust gas discharged from the cylinder flows toward the downstream end opening of the exhaust passage, and the other exhaust gas flows to the air introduction opening of the secondary air passage. It will flow towards. In this case, the exhaust gas that has flowed toward the air introduction opening of the secondary air passage flows from the air introduction opening into the first opening region through the second opening region and the continuous opening region of the gasket. The exhaust gas flowing out from the downstream end opening merges. That is, the exhaust gas that has flowed toward the air introduction opening of the secondary air passage is discharged toward the exhaust pipe, for example, through the passage (the second opening region, the continuous opening region, and the first opening region) inside the gasket. Will be. For this reason, the pressure (exhaust pulsation) applied to the gasket from the exhaust gas flowing into the secondary air passage is reduced, and the flange and the gasket vibrate due to the pressure from the exhaust gas. It is suppressed and the generation of abnormal noise due to the vibration of the gasket is suppressed.

  Other solutions for achieving the above object include the following. First, assuming an exhaust structure of an internal combustion engine in which a flange portion of an exhaust manifold is connected via a gasket to a cylinder head in which an air introduction opening of a secondary air passage is formed adjacent to a downstream end opening of the exhaust passage. To do. With respect to the exhaust structure of the internal combustion engine, a communication space for communicating the downstream end opening of the exhaust passage and the air introduction opening of the secondary air passage is formed between the flange portion of the exhaust manifold and the cylinder head. In this way, a recessed portion is formed that is retracted with respect to the cylinder head.

  When the cylinder head provided with the exhaust passage and the secondary air passage is applied to an internal combustion engine not equipped with a secondary air supply device so as to be applicable to the internal combustion engine equipped with the secondary air supply device due to this specific matter. For this, the exhaust manifold having the concave portion formed in the flange portion is used. According to this, when the internal combustion engine is driven, a part of the exhaust gas discharged from the cylinder flows toward the downstream end opening of the exhaust passage, and the other exhaust gas flows to the air introduction opening of the secondary air passage. It will flow towards. In this case, the exhaust gas flowing toward the air introduction opening of the secondary air passage flows from the air introduction opening into the recessed portion formed in the flange portion of the exhaust manifold, and flows out from the downstream end opening of the exhaust passage. It will join the exhaust gas that has been. In other words, the exhaust gas that has flowed toward the air introduction opening of the secondary air passage passes through a communication space formed between the flange portion of the exhaust manifold and the cylinder head (the inner space of the recessed portion), for example, an exhaust pipe. It will be discharged towards. For this reason, the pressure (exhaust pulsation) applied to the flange portion of the exhaust manifold from the exhaust gas flowing into the secondary air passage is reduced, and the flange portion vibrates due to the pressure from the exhaust gas. This suppresses the generation of abnormal noise associated with the vibration of the flange portion.

  The above solutions can be combined with each other. Specific examples of the combination of these include the following. First, assuming an exhaust structure of an internal combustion engine in which a flange portion of an exhaust manifold is connected via a gasket to a cylinder head in which an air introduction opening of a secondary air passage is formed adjacent to a downstream end opening of the exhaust passage. To do. For the exhaust structure of the internal combustion engine, the gasket includes a first opening region corresponding to the downstream end opening of the exhaust passage, a second opening region corresponding to the air introduction opening of the secondary air passage, and these A continuous opening region for forming a continuous opening between the first opening region and the second opening region is formed. Further, the cylinder head is formed such that a communication space for communicating the downstream end opening of the exhaust passage and the air introduction opening of the secondary air passage is formed between the flange portion of the exhaust manifold and the cylinder head. Recesses that recede are formed.

  According to this configuration, the exhaust gas flowing through the secondary air passage flows through each opening region formed in the gasket and also flows through the inner space of the recessed portion formed in the flange portion of the exhaust manifold. It will be discharged towards the pipe. For this reason, a large path for releasing the pressure of the exhaust gas flowing through the secondary air passage to the exhaust passage side can be secured, and the effect of suppressing the occurrence of abnormal noise can be exhibited more remarkably.

  Further, in contrast to the gasket having an improved shape, the shape of the bead for ensuring sealing performance in the gasket is as follows. That is, a bead shape is formed along the outer peripheral edge of the opening continuously formed by the first opening region, the second opening region, and the continuous opening region. As a result, both the exhaust gas flowing through the first opening region of the gasket and the exhaust gas flowing from the second opening region of the gasket through the continuous opening region into the first opening region can be discharged toward the exhaust pipe without leakage. Is possible.

  In the present invention, when the cylinder head in which the secondary air passage is formed is applied to an internal combustion engine not equipped with the secondary air supply device, the exhaust gas flowing through the secondary air passage flows through the exhaust passage. The shape of the flange part of the gasket and exhaust manifold is improved so that the exhaust gas is merged outside the cylinder head, and the pressure of the exhaust gas in the secondary air passage is released to the exhaust passage side. Yes. Thereby, generation | occurrence | production of the abnormal noise by the pressure of exhaust gas can be suppressed, and the noise at the time of the drive of an internal combustion engine can be reduced, improving the versatility of a cylinder head.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. This embodiment demonstrates the case where this invention is applied to the exhaust system of a motor vehicle engine. Further, in each of the following embodiments, the cylinder head formed with the Ai port is used as a secondary in order to be applicable to an engine equipped with a secondary air supply device that supplies secondary air into the exhaust port. A configuration when applied to an engine not equipped with an air supply device will be described.

(First embodiment)
FIG. 1 is an exploded perspective view of the cylinder head 1, the gasket 2, and the exhaust manifold 3 in the present embodiment. FIG. 2 is a cross-sectional view showing the connection portion between the exhaust manifold 3 and the cylinder head 1 and the configuration around it. Specifically, it is a longitudinal sectional view of a connection portion of one branch pipe 31 to the cylinder head 1.

  As shown in these drawings, the engine according to the present embodiment is a four-cylinder engine, and openings 41, 41,... Of exhaust ports 4 are formed at four positions on the side surface of the cylinder head 1. The cylinder head 1 is made of an aluminum alloy, and a cylinder block is attached to the lower part and a head cover is attached to the upper part.

  Further, the cylinder head 1 according to the present embodiment has an Ai port 5 formed to cope with a case where a secondary air supply device that supplies secondary air into the exhaust port 4 is mounted. Therefore, the openings (secondary air introduction openings) 51, 51,... Of the Ai port 5 are formed adjacent to the openings 41, 41,. The openings 51, 51,... Of the Ai port 5 are smaller in diameter than the openings 41, 41,... Of the exhaust port 4, and are adjacent to the diagonally upper portions of the openings 41, 41,. And each is formed.

  Although not mounted on the engine according to the present embodiment, an outline of a general secondary air supply device will be described below. This secondary air supply device increases the oxygen concentration in the exhaust system by supplying secondary air upstream from an exhaust purification device (catalyst) (not shown) provided in the exhaust system of the engine. Thus, the purification of the exhaust gas is promoted by oxidizing HC and CO in the exhaust gas. Therefore, this secondary air supply device opens and closes an air introduction pipe connected to the openings 51, 51,... Of the Ai port 5, an air pump for sending secondary air to the air introduction pipe, and an air introduction pipe. A valve unit (both not shown) is provided.

For example, when the amount of carbon monoxide (CO) or hydrocarbon (HC) in the exhaust gas is large, such as when the engine is cold-started, the air discharged from the air pump is supplied to the air introduction pipe and the Ai port. 5 is supplied as secondary air into the exhaust port 4. As a result, in the exhaust port 4, oxygen in the supplied secondary air reacts with carbon monoxide and hydrocarbons in the exhaust, which are oxidized to carbon dioxide (CO ₂ ) and water (H ₂ O). As a result, the exhaust gas is purified.

  In this embodiment, since this secondary air supply device is not mounted, the exhaust gas flowing through the Ai port 5 (flowing in the direction opposite to the flow direction of the original secondary air) is directed to the branch pipe 31. The structure for flowing is adopted. The configuration for that will be described later.

  The exhaust manifold 3 is made of a stainless steel plate and includes four branch pipes 31, 31,... Corresponding to each cylinder, and a junction pipe 32 that joins the downstream ends of the branch pipes 31, 31,. Yes. Further, a flange portion 33 is integrally attached to the upstream end of each branch pipe 31, 31,... By means such as welding. This flange portion 33 is formed on the side surface of the cylinder head 1 (the side surface on which the openings 41, 41,... Of the exhaust port 4 and the openings 51, 51,... Of the Ai port 5 are formed: Are attached by bolting or the like, and bolt insertion holes 34, 34,... Are formed corresponding to the bolt holes 12, 12,.

  The gasket 2 is sandwiched between the exhaust manifold mounting surface 11 of the cylinder head 1 and the flange portion 33 of the exhaust manifold 3, thereby preventing exhaust gas from leaking between the cylinder head 1 and the exhaust manifold 3. It functions as a seal member. The gasket 2 is formed by laminating a plurality of (for example, two) plate members made of metal (for example, stainless steel), and has a peripheral portion (the exhaust port 4 described above) in an area where it is necessary to prevent leakage of exhaust gas. When a bent portion called a bead is formed at a position corresponding to the peripheral edge of the opening 41 and the peripheral edge of the opening 51 of the Ai port 5 and is sandwiched between the cylinder head 1 and the exhaust manifold 3, By compressing and deforming the bead, the degree of adhesion is increased, thereby obtaining a high sealing property.

  Further, the gasket 2 has exhaust openings 21, 21,... At positions corresponding to the openings 41, 41,... Of the exhaust port 4 and the openings 51, 51,. .. Are formed, and bolt insertion holes 22, 22,... Corresponding to the bolt holes 12, 12,.

  As shown in FIGS. 1 and 2, a flange 33 welded to the outer peripheral portion of the upstream end of the branch pipe 31 of the exhaust manifold 3 is bolted to the exhaust manifold mounting surface 11 of the cylinder head 1 via the gasket 2. It is attached by means of

  Further, at the connection portion between the exhaust manifold 3 and the cylinder head 1, the inner diameter of the branch pipe 31 is reduced in order to reduce pressure loss when the exhaust gas flows into the branch pipe 31 from the exhaust port 4 of the cylinder head 1. Is set slightly larger than the inner diameter of the opening 41 of the exhaust port 4.

  The feature of this embodiment is the shape of the exhaust openings 21, 21,. This will be specifically described below.

  FIG. 3 is a front view showing one exhaust opening 21 and its peripheral part in the gasket 2.

  As a feature of the gasket 2, the exhaust opening 21 formed in the gasket 2 includes a first opening region 23, a second opening region 24, and a continuous opening region 25. Hereinafter, each opening area | region 23,24,25 is demonstrated.

  The first opening region 23 is a substantially circular opening corresponding to the opening 41 of the exhaust port 4. The inner diameter dimension of the first opening area 23 is larger than the inner diameter dimension of the opening 41 of the exhaust port 4 in order to reduce the pressure loss when the exhaust gas flows out from the exhaust port 4 to the first opening area 23. It is set slightly larger.

  The second opening region 24 is a substantially circular opening corresponding to the opening 51 of the Ai port 5. The inner diameter dimension of the second opening area 24 is also larger than the inner diameter dimension of the opening 51 of the Ai port 5 in order to reduce the pressure loss when the exhaust gas flows out from the Ai port 5 to the second opening area 24. It is set slightly larger.

  The continuous opening region 25 is formed from the first opening region 23 to the second opening region 24 in order to configure the first opening region 23 and the second opening region 24 as continuous openings. . That is, the opening 41 of the exhaust port 4 and the opening 51 of the Ai port 5 are configured to communicate with each other via the continuous opening region 25. In other words, the opening 41 of the exhaust port 4 is open to the first opening area 23, and the opening 51 of the Ai port 5 is open to the second opening area 24. The opening region 24 is configured as a continuous opening portion by a continuous opening region 25. As a result, the opening 41 of the exhaust port 4 and the opening 51 of the Ai port 5 are communicated via the continuous opening region 25.

  As will be described later, the flow of the exhaust gas in the exhaust opening 21 is a flow from the second opening region 24 to the first opening region 23 through the continuous opening region 25. At this time, the second opening region Each of the opening regions is controlled so as to suppress the disturbance of the flow lines of the exhaust gas when the exhaust gas flows into the continuous opening region 25 from 24 and when the exhaust gas flows into the first opening region 23 from the continuous opening region 25. The outer edges of 24, 25, and 23 are connected by a smooth curved surface.

  Further, the beads in the gasket 2 are formed in a deformed annular shape so as to surround the outer periphery of the first opening region 23, the second opening region 24, and the continuous opening region 25. In FIG. 3, the shape of this bead (seal line shape) is indicated by a one-dot chain line.

  Since the gasket 2 is configured as described above, the flow of exhaust gas during engine driving is as follows. When the engine is driven, exhaust gas is discharged from the cylinder in the exhaust stroke toward the exhaust port 4. A part of the exhaust gas discharged through the exhaust port 4 passes through the first opening region 23 of the gasket 2 from the opening 41 and is discharged to the branch pipe 31 (arrow A in FIG. 2). See).

  On the other hand, a part of the exhaust gas once discharged into the exhaust port 4 from the inside of the cylinder passes through the Ai port 5 as shown by an arrow B in FIG. It passes through the opening area 24 and further flows through the continuous opening area 25 of the gasket 2 to reach the first opening area 23. In the first opening region 23, the exhaust gas passes through the exhaust port 4 and the first opening region 23, and then is discharged to the branch pipe 31. That is, the exhaust gas flowing toward the opening 51 of the Ai port 5 is outside the cylinder head 1 and inside the gasket 2 (second opening area 24, continuous opening area 25, first opening area 23). ) To be discharged to the branch pipe 31.

  For this reason, the pressure of the exhaust gas in the Ai port 5 is released to the branch pipe 31 side, and the exhaust gas flowing through the Ai port 5 collides with the gasket 2 to vibrate the gasket 2. Therefore, the generation of abnormal noise accompanying the vibration of the gasket 2 is suppressed. Further, vibration of the flange portion 33 of the exhaust manifold 3 is also suppressed. For this reason, while increasing the versatility of the cylinder head 1 (while enabling it to be used for both an engine equipped with a secondary air supply device and an engine not equipped with a secondary air supply device), the sound during engine driving Can be reduced.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the first embodiment described above, the exhaust gas flowing through the Ai port 5 can be discharged to the branch pipe 31 by improving the shape of the gasket 2. In the present embodiment, instead, the shape of the flange portion 33 of the exhaust manifold 3 is improved so that the exhaust gas flowing through the Ai port 5 can be discharged to the branch pipe 31. Since the configuration of the cylinder head 1 is the same as that of the first embodiment described above, only the configuration of the gasket 2 and the configuration of the flange portion 33 of the exhaust manifold 3 will be described here.

  FIG. 4 is an exploded perspective view (corresponding to FIG. 1) of the cylinder head 1, the gasket 2, and the exhaust manifold 3 in the present embodiment. FIG. 5 is a cross-sectional view (corresponding to FIG. 2 above) showing the connection portion between the exhaust manifold 3 and the cylinder head 1 and the configuration around it. Further, FIG. 6 is a perspective view showing one branch pipe connecting portion and its peripheral portion in the flange portion 33 of the exhaust manifold 3. In FIG. 6, the branch pipe 31 is omitted.

  As shown in these drawings, as a feature of the flange portion 33 of the exhaust manifold 3, a communication space for allowing the opening portion 41 of the exhaust port 4 and the opening portion 51 of the Ai port 5 to communicate with the flange portion 33. A recessed portion 35 that recedes from the cylinder head 1 is formed so as to form C (see FIG. 5) with the cylinder head 1. That is, the opening 41 of the exhaust port 4 and the opening 51 of the Ai port 5 communicate with each other outside the cylinder head 1 by forming a recess 35 in a part of the flange 33 of the exhaust manifold 3. It has been configured.

  On the other hand, the shape of the gasket 2 in the present embodiment is a first opening 26 (corresponding to the first opening region 23 in the first embodiment) which is a substantially circular opening corresponding to the opening 41 of the exhaust port 4. ) And a second opening 27 (corresponding to the second opening region 24 in the first embodiment) that is a substantially circular opening corresponding to the opening 51 of the Ai port 5. Opening).

  Since the flange portion 33 of the exhaust manifold 3 is configured as described above, the flow of exhaust gas during engine driving is as follows. When the engine is driven, exhaust gas is discharged from the cylinder in the exhaust stroke toward the exhaust port 4. A part of the discharged exhaust gas is discharged to the branch pipe 31 as it is through the exhaust port 4 and the first opening 26 of the gasket 2 (see arrow A in FIG. 5).

  On the other hand, a part of the exhaust gas once discharged from the cylinder to the exhaust port 4 passes through the Ai port 5 and the second opening 27 of the gasket 2 as shown by an arrow B in FIG. It flows into the communication space C inside the recessed portion 35 formed in the flange portion 33 of the manifold 3. The exhaust gas flowing into the communication space C joins the exhaust gas that has passed through the exhaust port 4 and the first opening 26 and is then discharged to the branch pipe 31. That is, the exhaust gas flowing toward the opening 51 of the Ai port 5 is outside the cylinder head 1 and passes through the communication space C between the flange portion 33 of the exhaust manifold 3 and the gasket 2, and the branch pipe. It will be discharged to 31.

  Therefore, also in this embodiment, the pressure of the exhaust gas in the Ai port 5 is released to the branch pipe 31 side, and the exhaust gas flowing through the Ai port 5 collides with the flange portion 33 of the exhaust manifold 3. The vibration of the flange portion 33 is suppressed, and the generation of noise due to the vibration of the flange portion 33 is suppressed. For this reason, while increasing the versatility of the cylinder head 1 (while enabling it to be used for both an engine equipped with a secondary air supply device and an engine not equipped with a secondary air supply device), the sound during engine driving Can be reduced.

  The configuration of the second embodiment can be combined with the configuration of the first embodiment described above. That is, as the gasket 2, the one in which the exhaust opening 21 is formed by the first opening region 23, the second opening region 24, and the continuous opening region 25 is employed as in the first embodiment. Further, as the exhaust manifold 3, as in the second embodiment, a flange portion 33 having a recessed portion 35 that is retracted with respect to the cylinder head 1 is employed.

  According to this configuration, the exhaust gas flowing through the Ai port 5 flows through each opening region (second opening region 24, continuous opening region 25, first opening region 23) formed in the gasket 2, and the exhaust manifold 3. It flows through the communication space C in the recessed portion 35 formed in the flange portion 33 and is discharged to the branch pipe 31. For this reason, a large path for releasing the pressure of the exhaust gas in the Ai port 5 toward the branch pipe 31 can be secured, and the effect of suppressing the occurrence of abnormal noise can be exhibited more remarkably.

-Other embodiments-
Although the engine according to each of the embodiments described above has a four-cylinder engine, the present invention is not limited to this, and the present invention can be applied to an engine having three or less cylinders or an engine having five or more cylinders. .

  In each of the above embodiments, the formation position of the opening 51 of the Ai port 5 in the cylinder head 1 is obliquely above the opening 41 of the exhaust port 4 and is the central side in the cylinder row direction. The formation position is not limited to this. In the case where the formation position of the opening 51 of the Ai port 5 is different from that in each of the above embodiments, the second opening region 24 and the continuous opening region of the gasket 2 are correspondingly corresponding to the case of the first embodiment. In the case of the second embodiment, the position of the recessed portion 35 formed in the flange portion 33 of the exhaust manifold 3 is changed.

  In each of the above embodiments, the cylinder head 1 is made of an aluminum alloy. However, the present invention is not limited to this and may be applied to a cylinder head made of cast iron.

It is a disassembled perspective view of the cylinder head in the 1st embodiment, a gasket, and an exhaust manifold. It is sectional drawing which shows the connection part of the exhaust manifold and cylinder head in 1st Embodiment, and the structure of the periphery. It is a front view which shows one opening for exhaust_gas | exhaustion in the gasket which concerns on 1st Embodiment, and its peripheral part. It is a disassembled perspective view of the cylinder head, a gasket, and an exhaust manifold in 2nd Embodiment. It is sectional drawing which shows the connection part of the exhaust manifold and cylinder head in 2nd Embodiment, and the structure of the periphery. It is a perspective view which shows one branch pipe connection part and its peripheral part in the flange part of the exhaust manifold which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Gasket 21 Exhaust opening 23 1st opening area 24 2nd opening area 25 Continuous opening area 3 Exhaust manifold 33 Flange part 35 Recessed part 4 Exhaust port (exhaust passage)
41 Exhaust port opening (opening downstream end of exhaust passage)
5 Ai port (secondary air passage)
51 Ai port opening (secondary air passage air inlet opening)

Claims (4)

In an exhaust structure of an internal combustion engine in which a flange portion of an exhaust manifold is connected via a gasket to a cylinder head in which an air introduction opening of a secondary air passage is formed adjacent to a downstream end opening of the exhaust passage.
The gasket includes a first opening region corresponding to the downstream end opening of the exhaust passage, a second opening region corresponding to the air introduction opening of the secondary air passage, the first opening region and the second opening region. An exhaust structure for an internal combustion engine, wherein a continuous opening region for forming a continuous opening with the opening region is formed. In an exhaust structure of an internal combustion engine in which a flange portion of an exhaust manifold is connected via a gasket to a cylinder head in which an air introduction opening of a secondary air passage is formed adjacent to a downstream end opening of the exhaust passage.
In the flange portion of the exhaust manifold, a communication space for connecting the downstream end opening of the exhaust passage and the air introduction opening of the secondary air passage is formed between the cylinder head and the cylinder head. An exhaust structure for an internal combustion engine, characterized in that a recessed portion that is retracted is formed. In an exhaust structure of an internal combustion engine in which a flange portion of an exhaust manifold is connected via a gasket to a cylinder head in which an air introduction opening of a secondary air passage is formed adjacent to a downstream end opening of the exhaust passage.
The gasket includes a first opening region corresponding to the downstream end opening of the exhaust passage, a second opening region corresponding to the air introduction opening of the secondary air passage, the first opening region and the second opening region. A continuous opening region for forming a continuous opening with the opening region of
In the flange portion of the exhaust manifold, a communication space for connecting the downstream end opening of the exhaust passage and the air introduction opening of the secondary air passage is formed between the cylinder head and the cylinder head. An exhaust structure for an internal combustion engine, characterized in that a recessed portion that is retracted is formed. In the exhaust structure of the internal combustion engine according to claim 1 or 3,
The shape of the bead for ensuring sealing performance in the gasket is a shape along the outer peripheral edge of the opening continuously formed by the first opening region, the second opening region, and the continuous opening region. An exhaust structure for an internal combustion engine.

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