JP2021116741A - Air inlet pipe connecting structure of internal combustion engine and intake manifold - Google Patents

Abstract

To provide an inlet pipe connecting structure of an internal combustion engine and an intake manifold in which a sealability of a connecting part between the internal combustion engine and the inlet pipe can be suitably improved.SOLUTION: In an aspect of connecting an inlet pipe 23 to an intake port of the internal combustion engine 30, an attachment flange 24 of the intake manifold 20 is fixed by a screw to the internal combustion engine 30. Between the internal combustion engine 30 and the attachment flange 24, a gasket 40 made of an elastic material is interposed in a compressed state in an aspect of surrounding the inlet passage composed of the inlet port and the inlet pipe 23. Among the parts of the attachment flange 24, a small compression part 56 which forms at least a part of a high rigidity part having a high rigidity has a smaller compression level of the gasket 40 compared to a low rigidity part having a lower rigidity than the high rigidity part.SELECTED DRAWING: Figure 8

Description

The present invention relates to an intake pipe connecting structure of an internal combustion engine that connects an intake pipe to the internal combustion engine via a gasket, and an intake manifold including an intake pipe.

The intake manifold, specifically the connection end of the intake pipe, is fastened and fixed to the internal combustion engine with bolts. As a result, the intake pipe of the intake manifold is connected to the intake port of the internal combustion engine.

Further, between the internal combustion engine and the intake pipe, a gasket made of an elastic material is interposed in a compressed state so as to surround the periphery of the intake passage including the intake port and the intake pipe of the internal combustion engine. The gasket seals the inside and outside of the intake passage at the connection portion between the internal combustion engine and the intake pipe.

In recent years, intake manifolds made of synthetic resin have been put into practical use (see, for example, Patent Document 1).

Jikkenhei No. 7-35751

Since the intake pipe of the intake manifold is fastened and fixed to the internal combustion engine, the connection end of the intake pipe is in a state where a high surface pressure (load) is applied. Further, since the internal combustion engine becomes hot during operation, the connection end of the intake pipe connected to the internal combustion engine also becomes hot due to heat transfer from the internal combustion engine. As described above, the connection end of the intake pipe is arranged in an environment in which a high load acts as the temperature rises, that is, in an environment in which creep deformation is likely to occur.

The intake manifold made of synthetic resin is more likely to undergo creep deformation than the intake manifold made of metal. When such an intake manifold made of synthetic resin is used, the connection end of the intake pipe is in a state where a high load is applied at a high temperature, so that the connection end of the intake pipe may be creep-deformed. In this case, the gap between the internal combustion engine and the connection end of the intake pipe may be partially increased, and the sealing performance of the gasket in the gap may be deteriorated.

In order to suppress such deterioration of sealing performance, it is conceivable to increase the contact surface pressure between the gasket and the connection end of the intake pipe in advance when using the intake manifold made of synthetic resin. As a result, even when the contact surface pressure decreases due to the occurrence of creep deformation, it is possible to prevent the absolute value of the contact surface pressure from falling below a predetermined level. However, in this case, the load applied from the gasket to the connection end of the intake pipe increases as the contact surface pressure increases, which acts to increase the amount of deformation in creep deformation. Therefore, it can be said that a configuration in which the contact surface pressure between the gasket and the connection end of the intake pipe is increased in advance cannot be an effective means for improving the sealing performance.

The present invention has been made in view of such circumstances, and an object of the present invention is an intake pipe connection structure of an internal combustion engine capable of suitably improving the sealing performance of a connection portion between the internal combustion engine and the intake pipe, and an intake manifold. Is to provide.

The intake pipe connection structure of the internal combustion engine for solving the above problems is such that the intake pipe is connected to the intake port of the internal combustion engine, and the connection end of the intake pipe is screwed and fixed to the internal combustion engine, and the internal combustion is fixed. The intake air of an internal combustion engine formed by interposing a gasket made of an elastic material in a compressed state between the engine and the connection end of the intake pipe so as to surround the intake passage including the intake port and the intake pipe. In the pipe connection structure, among the parts of the connection end of the intake pipe, the small compression part forming at least a part of the high-rigidity high-rigidity part is compared with the low-rigidity part having a lower rigidity than the high-rigidity part. , The degree of compression of the gasket is small.

According to the above configuration, in each part of the connection end of the intake pipe, in the low-rigidity part where there is a risk of creep deformation due to low rigidity, the degree of compression of the gasket is increased to increase the contact surface pressure with the gasket. By setting it high in advance, it is possible to prevent the sealing performance from falling below a predetermined level due to creep deformation.

Moreover, in the high-rigidity part (specifically, the small compression part) where creep deformation is unlikely to occur due to the high rigidity of each part of the connection end of the intake pipe, the degree of compression of the gasket is reduced to make contact with the gasket. The surface pressure can be lowered. As a result, the total amount of force applied from the gasket to the connection end of the intake pipe is increased as compared with the case where the degree of compression of the gasket at each portion of the connection end of the intake pipe is made uniform according to the degree of compression of the low-rigidity portion. Since it can be reduced, the amount of creep deformation at the connection end of the intake pipe can be reduced.

As described above, according to the above configuration, the sealing performance of the connecting portion between the internal combustion engine and the intake pipe is suitably improved by giving a distribution in the degree of compression of the gasket according to the rigidity of each portion of the connecting end of the intake pipe. Can be made to.

The intake manifold for solving the above problems has an intake pipe, and a gasket made of an elastic material is interposed between the intake pipe and the internal combustion engine, and the connection end of the intake pipe is connected to the internal combustion engine. In the intake manifold having a structure of being screwed and fixed, a groove into which the gasket is fitted is provided at the connection end of the intake pipe, and among the respective parts of the connection end of the intake pipe, a highly rigid portion having high rigidity. In the small compression portion forming at least a part thereof, the depth of the groove is deeper than that of the low-rigidity portion having lower rigidity than the high-rigidity portion.

According to the above configuration, among the parts of the connection end of the intake pipe, in the low-rigidity part where there is a risk of creep deformation due to low rigidity, the connection end between the internal combustion engine and the intake pipe at the intermediate portion of the gasket (details). Can shorten the distance from the bottom of the groove). As a result, in the low-rigidity portion, the degree of compression of the gasket in the fixed state in which the intake manifold is fixed to the internal combustion engine can be increased and the contact surface pressure with the gasket can be increased in advance, resulting in creep deformation. As a result, it is possible to prevent the sealing performance from falling below a predetermined level.

Moreover, since the interval can be lengthened in the high-rigidity portion (specifically, the small compression portion) that has high rigidity and is unlikely to cause creep deformation among the respective portions of the connection end of the intake pipe, the gasket in the fixed state is provided. The degree of compression of the gasket can be reduced to reduce the contact surface pressure with the gasket. As a result, the total amount of force applied from the gasket to the connection end of the intake pipe is increased as compared with the case where the degree of compression of the gasket at each portion of the connection end of the intake pipe is made uniform according to the degree of compression of the low-rigidity portion. Since it can be reduced, the amount of creep deformation at the connection end of the intake pipe can be reduced.

As described above, according to the above configuration, the degree of compression of the gasket can be distributed according to the rigidity of each portion of the connection end of the intake pipe, so that the sealing performance of the connection portion between the internal combustion engine and the intake pipe is preferable. Can be improved.

The side view which shows one Embodiment of the intake pipe connection structure of an internal combustion engine. The schematic which shows the intake system of the internal combustion engine schematicly. An exploded perspective view of the intake pipe connection structure of the internal combustion engine. Side view of the mounting flange of the intake manifold as seen from the internal combustion engine side. FIG. 5 is a cross-sectional view showing a cross-sectional structure of a groove of the mounting flange along line 5-5 of FIG. FIG. 6 is a cross-sectional view showing a cross-sectional structure of a groove of the mounting flange along the line 6-6 of FIG. Side view of the mounting flange as seen from the internal combustion engine side. An enlarged cross-sectional view showing a connection portion between an internal combustion engine and an intake manifold. An exploded perspective view showing another embodiment of an intake pipe connection structure of an internal combustion engine. An enlarged cross-sectional view showing a connection portion between the internal combustion engine and the intake manifold. A side view of the mounting flange of the intake manifold of another embodiment as viewed from the internal combustion engine side. FIG. 5 is a cross-sectional view showing a cross-sectional structure of the mounting flange along line 12-12 of FIG. An enlarged cross-sectional view showing a connection portion between an internal combustion engine and an intake manifold.

Hereinafter, an intake pipe connection structure of an internal combustion engine and an embodiment of an intake manifold will be described.
As shown in FIGS. 1 and 2, the intake manifold 20 is provided in a surge tank 21 as a volume chamber, an introduction port 22 for introducing air into the surge tank 21, and from the surge tank 21 to each cylinder 31 of the internal combustion engine 30. It has a plurality of intake pipes 23 for distributing air, and a mounting flange 24 used for mounting each intake pipe 23 to the internal combustion engine 30. The intake manifold 20 is made of a hard synthetic resin material.

As shown in FIG. 2, the intake manifold 20 is attached to a three-cylinder internal combustion engine 30 and has three intake pipes 23. As shown in FIG. 1, each intake pipe 23 is curved and extends so as to involve the outside of the surge tank 21 in a manner in which the intake pipes 23 are arranged in the cylinder alignment direction (hereinafter, predetermined direction D) of the internal combustion engine 30.

As shown in FIGS. 1 to 3, one end of each intake pipe 23 (specifically, the end on the upstream side in the intake flow direction) is connected to the surge tank 21. Each intake pipe 23 has a main pipe wall portion 25 having a tubular shape, and a branch wall portion 27 that branches the inside of the main pipe wall portion 25 into two branch passages 26. The intake pipe 23 has a structure in which a portion downstream in the intake flow direction (left side in FIG. 2) is branched into two branch passages 26 by the branch wall portion 27.

The mounting flange 24 is provided at the downstream end of each intake pipe 23. The mounting flange 24 integrally connects the ends of the three intake pipes 23.
In the end surface 24A of the mounting flange 24 on the internal combustion engine 30 side, three sets of branch passages 26 corresponding to the three cylinders 31 are opened in a predetermined direction D at intervals. Further, in the end surface 24A of the mounting flange 24, two branch passages 26 corresponding to the same cylinder 31 are opened so as to be lined up in a predetermined direction D with the branch wall portion 27 sandwiched between them.

As shown in FIG. 3, when the intake manifold 20 is attached to the internal combustion engine 30, the attachment flange 24 is fixed to the internal combustion engine 30 with a gasket 40 made of an elastic material (for example, silicon rubber) sandwiched between them. NS. In the present embodiment, the mounting flange 24 includes a connection end of the intake pipe 23, a connection end of the main pipe wall portion 25, and a connection end of the branch wall portion 27.

As shown in FIGS. 3 and 4, a groove 50 into which the gasket 40 is fitted is formed in the end surface 24A of the mounting flange 24. The groove 50 is extended with the same width. Further, the groove 50 is branched from the outer peripheral groove portion 51 extending in an annular shape (specifically, a square annular shape with rounded corners) along the entire circumference of the main pipe wall portion 25 along the portion corresponding to the end portion of the main pipe wall portion 25. The portion corresponding to the end portion of the wall portion 27 has a branch groove portion 52 extending in a manner of connecting the opposing portions of the outer peripheral groove portion 51. The end surface 24A of the mounting flange 24 is provided with grooves 50 composed of an outer peripheral groove portion 51 and a branch groove portion 52 at three locations corresponding to the three intake pipes 23, respectively.

As shown in FIGS. 4 and 5, the outer peripheral groove portion 51 extends to a certain depth. Further, as shown in FIGS. 4 and 6, the depth of the branch groove portion 52 is deeper than the depth of the outer peripheral groove portion 51. The branch groove portion 52 has a shape in which a step is not formed on the bottom surface at the boundary with the outer peripheral groove portion 51, and is formed in a shape that gradually becomes shallower as it approaches the outer peripheral groove portion 51. In the present embodiment, the depth of the outer peripheral groove portion 51 and the depth of the branch groove portion 52 are shorter than the thickness of the gasket 40 in the inelastically deformed state in the fastening and fixing direction.

As shown in FIGS. 3 and 4, through holes 53 are formed in the mounting flange 24 at four locations, both ends (two locations) in the predetermined direction D and the portions (two locations) between the adjacent intake pipes 23. Has been done. These through holes 53 extend in a circular cross section in the thickness direction of the mounting flange 24. A bolt 32 (see FIG. 3) for fastening and fixing is inserted into each through hole 53 when the intake manifold 20 is attached to the internal combustion engine 30. In this embodiment, the through hole 53 corresponds to the fastening and fixing portion.

The through hole 53 is provided at a position so as to sandwich each main pipe wall portion 25 (specifically, two branch passages 26 corresponding to the same cylinder 31). Specifically, one of the pair of through holes 53 corresponding to the same main pipe wall portion 25 is provided at the end portion of the mounting flange 24 inside the intake pipe 23 in the bending direction (lower side in FIG. 4). The other is provided at the end of the intake pipe 23 on the outside in the bending direction (upper side in FIG. 4).

As shown in FIG. 3, the gasket 40 has a branch seal portion 42 having an annular shape that fits into the outer peripheral groove portion 51 and a branch seal portion 42 that connects the facing portions of the outer peripheral seal portion 41 so as to fit into the branch groove portion 52. It has three seal portions 43 made of. The gasket 40 has a structure in which three seal portions 43 are arranged at intervals, and a connecting portion 44 having a shape for connecting the outer peripheral seal portions 41 to each other is provided between the adjacent seal portions 43. In the gasket 40 in the inelastically deformed state, the thickness of each part in the fastening and fixing direction is the same. On the side surface of the gasket 40, convex portions 45 are formed so as to be arranged at intervals in the stretching direction. When the gasket 40 is fitted into the groove 50 of the mounting flange 24, the tip of each convex portion 45 comes into contact with the inner surface of the groove 50.

The cylinder head 33 of the internal combustion engine 30 is provided with three intake ports 34. Each intake port 34 has two branch ports 35. As shown in FIG. 2, the internal combustion engine 30 of the present embodiment has a structure in which two branch ports 35 are connected to one cylinder 31. Then, during low-load operation of the internal combustion engine 30 having a small amount of intake air, the flow velocity of the air flowing into the cylinder 31 can be increased by closing the on-off valve (not shown) and closing one of the branch ports 35. There is.

As shown in FIG. 3, on the side surface 33A of the cylinder head 33 on the intake manifold 20 side, three sets of branch ports 35 corresponding to the three cylinders 31 are opened in a predetermined direction D at intervals. .. Further, on the side surface 33A of the cylinder head 33, two branch ports 35 corresponding to the same cylinder 31 are opened in a manner of being arranged at intervals in a predetermined direction D.

On the side surface 33A of the cylinder head 33, female threads 36 are formed at four locations, a portion (two locations) sandwiching the three intake ports 34 in a predetermined direction D and a portion (two locations) between adjacent intake ports 34. There is. Bolts 32 for fastening and fixing are fitted into these female threads 36 when the intake manifold 20 is attached to the internal combustion engine 30.

In the present embodiment, when the end surface 24A of the mounting flange 24 of the intake manifold 20 is aligned with the side surface 33A of the cylinder head 33, each through hole 53 and each female screw 36 communicate with each other, and each branch passage 26 and each branch port 35. The through hole 53, the female screw 36, the branch passage 26, and the branch port 35 are arranged so as to communicate with each other.

The intake manifold 20 is attached to the internal combustion engine 30 as follows.
First, the gasket 40 is fitted into the groove 50 of the mounting flange 24 of the intake manifold 20. Then, in that state, the end surface 24A of the mounting flange 24 of the intake manifold 20 is aligned with the side surface 33A of the cylinder head 33. After that, the fastening and fixing bolt 32 is inserted into the through hole 53 of the mounting flange 24 of the intake manifold 20 and fitted into the female screw 36 of the cylinder head 33. As a result, the intake manifold 20 is screwed and fixed to the internal combustion engine 30 in such a manner that the six branch ports 35 and the six branch passages 26 communicate with each other separately.

Further, the outer peripheral seal portion 41 of the gasket 40 surrounds the periphery of the intake passage including the intake port 34 and the intake pipe 23, in a compressed state between the side surface 33A of the cylinder head 33 and the end surface 24A of the mounting flange 24. It will be installed. Further, the branch seal portion 42 of the gasket 40 is compressed between the side surface 33A of the cylinder head 33 and the end surface 24A of the mounting flange 24 in a manner of partitioning between the pair of branch passages including the branch port 35 and the branch passage 26. It is installed in the state. In the present embodiment, the gasket 40 seals the inside and outside of the intake passage at the connection portion between the internal combustion engine 30 and the intake manifold 20.

Hereinafter, the operation according to the present embodiment will be described.
As shown in FIG. 7, in the intake manifold 20, a pair of fastening and fixing portions (specifically, specifically, fastening and fixing portions) of the mounting flanges 24, which are fastened and fixed to the internal combustion engine 30 with the connection end of the intake pipe 23 sandwiched between them. The rigidity is highest in the portion arranged on the line segment L connecting the through holes 53). Then, the rigidity of the mounting flange 24 decreases as the distance from the line segment L increases.

For this reason, among the portions of the mounting flange 24 that correspond to the connection ends of the intake pipe 23, the portion farthest from the line segment L, specifically, the portion on the side where the through holes 53 are not provided at both ends in the predetermined direction D (low). It can be said that the rigidity of the rigid portion 55) is the lowest. In the intake manifold 20 of the present embodiment, it can be said that creep deformation is likely to occur in such a low-rigidity portion 55.

In the present embodiment, based on the results of various experiments and simulations by the inventor and the like, the depth of the groove 50 in the low-rigidity portion 55, specifically, the outer circumference including the portion arranged in the low-rigidity portion 55 in the groove 50. An appropriate length is defined as the depth of the groove 51. Specifically, the depth of the outer peripheral groove 51 is the same contact surface pressure even when the contact surface pressure at the contact portion between the gasket 40 and the mounting flange 24 of the intake manifold 20 decreases due to the occurrence of creep deformation. Is stipulated so that it does not fall below a predetermined level at which proper sealing performance is maintained.

According to the present embodiment, in the low-rigidity portion 55 and its surroundings, the distance between the bottom surface of the groove 50 and the side surface 33A of the cylinder head 33 is shortened in advance by making the depth of the groove 50 appropriately shallow. Can be kept. As a result, as shown in FIG. 8, the degree of compression of the outer peripheral seal portion 41 of the gasket 40 can be appropriately increased, and the surface pressure at the contact portion between the outer peripheral seal portion 41 and the mounting flange 24 can be increased in advance. can. Therefore, even when the interval is increased due to creep deformation, the surface pressure at the contact portion and the sealing performance by the gasket 40 can be suppressed from falling below a predetermined level.

On the other hand, as shown in FIG. 7, among the portions of the mounting flange 24 that correspond to the connection ends of the intake pipe 23, the portions other than the low-rigidity portion 55 are high-rigidity portions having higher rigidity than the low-rigidity portion 55. There is. The portion (small compression portion 56) corresponding to the connection end of the branch wall portion 27 forming a part of such a high rigidity portion has high rigidity because it is arranged inside the main pipe wall portion 25, and creep deformation occurs. Hard to occur. Therefore, in the small compression portion 56, the contact surface pressure is unlikely to decrease due to creep deformation, and the groove 50 (specifically, the branch groove portion 52) can be deepened to reduce the degree of compression of the gasket 40. It can be said.

Based on this point, in the intake manifold 20 of the present embodiment, the depth of the branch groove portion 52 formed at the connection end (small compression portion 56) of the branch wall portion 27 of the mounting flange 24 is the depth of the outer peripheral groove portion 51. It is deeper than the depth. As a result, as shown in FIG. 8, the distance between the bottom surface of the branch groove portion 52 and the side surface 33A of the cylinder head 33 is longer than the distance between the bottom surface of the outer peripheral groove portion 51 and the side surface 33A of the cylinder head 33. Therefore, the degree of compression of the branch seal portion 42 of the gasket 40 can be appropriately reduced, and the surface pressure at the contact portion between the branch seal portion 42 and the mounting flange 24 can be appropriately reduced.

Therefore, in the high-rigidity portion (specifically, the small compression portion 56) where creep deformation is unlikely to occur due to the high rigidity, the degree of compression of the gasket 40 can be reduced to reduce the contact surface pressure with the gasket 40. can. As a result, the total amount of force applied from the gasket 40 to the mounting flange 24 is reduced as compared with the case where the degree of compression in each portion of the gasket 40 is made uniform according to the degree of compression of the gasket 40 in the low-rigidity portion 55. be able to. The larger the total amount of the above forces, the larger the amount of deformation in creep deformation. According to the intake manifold 20 of the present embodiment, the total amount of such force can be reduced, so that the creep deformation amount of the mounting flange 24 can be reduced. Therefore, it is possible to suppress a decrease in sealing performance due to creep deformation.

Since the small compression portion 56 has high rigidity and is difficult to creep deform, even if the contact surface pressure is lowered in the initial state where creep deformation does not occur as described above, the creep deformation occurs. It is possible to prevent the absolute value of the contact surface pressure from falling below a predetermined level. For these reasons as well, according to the intake manifold 20 of the present embodiment, it is possible to suppress a decrease in sealing performance due to creep deformation.

As described above, according to the present embodiment, the internal combustion engine 30 and the intake manifold 20 are connected by giving a distribution to the degree of compression of the gasket 40 and the contact surface pressure according to the rigidity of each part of the mounting flange 24. The sealing performance of the portion can be suitably improved.

As described above, according to the present embodiment, the effects described below can be obtained.
(1) Of the portions of the mounting flange 24 that correspond to the connection ends of the intake pipe 23, the small compression portion 56, which forms a part of the high-rigidity high-rigidity portion, has a low-rigidity portion 55 having a lower rigidity than the high-rigidity portion. The degree of compression of the gasket 40 was reduced as compared with the above. Therefore, the sealing performance of the connection portion between the internal combustion engine 30 and the intake manifold 20 can be suitably improved.

(2) In the small compression portion 56, the distance between the internal combustion engine 30 and the mounting flange 24 in the intermediate portion of the gasket 40 is longer than that in the low rigidity portion 55. As a result, the degree of compression of the branch seal portion 42 of the gasket 40 arranged in the small compression portion 56 can be made smaller than the degree of compression of the outer peripheral seal portion 41 of the gasket 40 arranged in the low rigidity portion 55. can.

(3) A branch groove 52 and an outer peripheral groove 51 are formed as a groove 50 into which the gasket 40 is fitted in a portion of the mounting flange 24 corresponding to the connection end of the intake pipe 23. Then, the depth of the branch groove portion 52 formed in the small compression portion 56 is made deeper than the depth of the outer peripheral groove portion 51 formed in the low rigidity portion 55. As a result, among the intervals between the internal combustion engine 30 and the mounting flange 24 in each portion of the gasket 40, the same interval in the small compression portion 56 can be made longer than the same interval in the low rigidity portion 55.

(4) The bottom of the branch groove portion 52 formed in the small compression portion 56 has a depth of the branch groove portion 52 as it approaches the outer peripheral groove portion 51 at the boundary with the outer peripheral groove portion 51 formed in the other portion. It has a shape that gradually becomes shallower. As a result, it is possible to prevent a step from being formed at the boundary between the branch groove portion 52 and the outer peripheral groove portion 51. Therefore, even though the gasket 40 is pressed against the bottom of the groove 50 when the intake manifold 20 is fastened and fixed to the internal combustion engine 30, stress is suppressed from being concentrated on the portion corresponding to the boundary of the gasket 40. Will be able to. Therefore, the reliability of the gasket 40 can be improved.

The above embodiment can be modified and implemented as follows. The above embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

-Compared to the outer peripheral groove portion 51, the entire branch groove portion 52 is not limited to be deepened, and only a part of the branch groove portion 52 may be deepened. For example, the intermediate portion of the branch groove portion 52 in the extending direction (vertical direction of FIG. 4) may be deeper than both end portions, or the central portion of the branch groove portion 52 in the extending width direction (horizontal direction of FIG. 4) may be deeper than both side portions. It can be deepened. Even with such a configuration, the degree of compression of the gasket 40 can be reduced in at least a part of the high-rigidity portion of the portion corresponding to the connection end of the intake pipe 23 of the mounting flange 24 as compared with the low-rigidity portion 55.

Instead of making the depth of the branch groove 52 formed on the end surface 24A of the mounting flange 24 of the intake manifold 20 deeper than the depth of the outer peripheral groove 51, or in combination with this, as shown in FIGS. 9 and 10. In addition, the facing groove 37 may be formed in the portion of the side surface 33A of the cylinder head 33 facing the branch groove portion 52. In the examples shown in FIGS. 9 and 10, the depth of the branch groove 52 formed on the end surface 24A of the mounting flange 24 and the depth of the outer peripheral groove 51 are the same, and the facing groove 37 is formed on the side surface 33A of the cylinder head 33. Is formed. Even with such a configuration, as shown in FIG. 10, of the distance between the internal combustion engine 30 and the mounting flange 24 in each portion of the intermediate portion of the gasket 40, the portion corresponding to the branch groove portion 52 in which the facing groove 37 is formed is the same. The interval can be made larger than the same interval of the portion corresponding to the outer peripheral groove portion 51.

Instead of making the depth of the branch groove 52 formed on the end surface 24A of the mounting flange 24 of the intake manifold 20 deeper than the depth of the outer peripheral groove 51, or in combination with it, the branch seal of the gasket 40 in the inelastically deformed state. The thickness of the portion 42 in the fastening and fixing direction may be smaller than the thickness of the outer peripheral sealing portion 41 in the inelastically deformed state in the fastening and fixing direction. With such a configuration, the degree of compression in each part of the gasket 40 can be adjusted. When such a gasket is applied to an intake manifold having a uniform depth of the grooves 50 (specifically, the outer peripheral groove portion 51 and the branch groove portion 52), the degree of compression of the outer peripheral seal portion 41 fitted in the outer peripheral groove portion 51 and the degree of compression. In comparison, the degree of compression of the branch seal portion 42 fitted in the branch groove portion 52 can be reduced.

The small compression portion, which is a portion that reduces the degree of compression of the gasket 40 as compared with the low-rigidity portion 55, is not limited to setting a range including the entire branch groove portion 52, and only a part of the branch groove portion 52 is used. An arbitrary range can be set, such as setting a range to be included or setting a range including a part of the outer peripheral groove portion 51.

-The intake pipe connection structure and the intake manifold of the internal combustion engine according to the above embodiment can be applied to an internal combustion engine having a structure in which each intake pipe is not branched. In the same configuration, among the parts of the connection end of the intake pipe, the small compression part that forms at least a part of the high-rigidity high-rigidity part of the gasket is compared with the low-rigidity part that is less rigid than the high-rigidity part. The degree of compression may be reduced. According to such a configuration, the sealing performance of the connecting portion between the internal combustion engine and the intake pipe can be suitably improved by giving a distribution in the degree of compression of the gasket according to the rigidity of each part of the connecting end of the intake pipe. can.

An example of the above configuration is shown in FIGS. 11 to 13. Note that, in FIGS. 11 to 13, the same configurations as those in the above embodiments (see FIGS. 1 to 8) are shown with the same reference numerals or corresponding reference numerals, and the configurations thereof are duplicated below. The description is omitted.

As shown in FIG. 11, each intake pipe 63 of the intake manifold 60 has a tubular main pipe wall portion 65, but does not have a branch wall portion 27 (see FIG. 4). Further, the mounting flange 64 has the outer peripheral groove portion 71, but does not have the branch groove portion 52 (see FIG. 4). The gasket (not shown) provided on the intake manifold 60 has an outer peripheral seal portion 41 and a connecting portion 44, but does not have a branch seal portion 42.

Normally, in the intake manifold 60, a large number of wall portions such as an outer wall of a surge tank and reinforcing ribs are arranged on the inner portion of the intake pipe 63 in the bending direction, whereas a large number of wall portions such as the outer wall of the surge tank and the reinforcing ribs are arranged on the outer portion of the intake pipe 63 in the bending direction. The wall portion is hardly arranged. Therefore, the rigidity of the mounting flange 64 provided at the end of the intake pipe 63 is such that the portion corresponding to the inside of the intake pipe 63 in the bending direction (lower side of FIG. 11) is more rigid than the portion corresponding to the outside of the intake pipe 63 in the bending direction (upper side of FIG. 11). Is higher.

In the intake manifold 60, the portion of the mounting flange 64 outside in the bending direction is made into a low-rigidity portion 75, while the portion of the mounting flange 64 other than the low-rigidity portion 75 has higher rigidity than the low-rigidity portion 75. It is in the department. Further, the portion of the high-rigidity portion that corresponds to the inside in the bending direction is formed as the small compression portion 76. Then, as shown in FIGS. 11 and 12, the depth of the inner portion 71A arranged in the small compression portion 76 of each portion of the outer peripheral groove portion 71 is larger than the depth of the outer portion 71B which is the other portion. It's getting deeper. As a result, as shown in FIG. 13, the distance between the bottom surface of the inner portion 71A of the outer peripheral groove portion 71 and the side surface 33A of the cylinder head 33 becomes longer than the distance between the bottom surface of the outer portion 71B and the side surface 33A of the cylinder head 33. ing.

According to the above configuration, in the low-rigidity portion 75 and its surroundings, the distance between the bottom surface of the outer peripheral groove portion 71 and the side surface 33A of the cylinder head 33 is shortened in advance by appropriately making the depth of the outer peripheral groove portion 71 shallow. Can be kept. As a result, the degree of compression of the gasket 40 can be appropriately increased, and the surface pressure at the contact portion between the gasket 40 and the mounting flange 64 can be increased in advance. Therefore, even when the interval is increased due to creep deformation, it is possible to prevent the surface pressure at the contact portion and the sealing performance by the gasket 40 from falling below a predetermined level.

Moreover, in the high-rigidity portion (specifically, the small compression portion 76) where creep deformation is unlikely to occur due to the high rigidity, the degree of compression of the gasket 40 can be reduced to reduce the contact surface pressure with the gasket 40. can. As a result, the total amount of force applied from the gasket 40 to the mounting flange 64 is reduced as compared with the case where the degree of compression in each portion of the gasket 40 is made uniform according to the degree of compression of the gasket 40 in the low-rigidity portion 75. be able to. Therefore, the creep deformation amount of the mounting flange 64 can be reduced, and the deterioration of the sealing performance due to the creep deformation can be suppressed.

-The intake pipe connection structure and intake manifold of the internal combustion engine according to the above embodiment shall also be applied to the intake pipe connection structure and intake manifold of a single-cylinder internal combustion engine, a two-cylinder internal combustion engine, and an internal combustion engine of four or more cylinders. Can be done.

20, 60 ... Intake manifolds 23, 63 ... Intake pipes 24, 64 ... Mounting flanges 25, 65 ... Main pipe wall 26 ... Branch passage 27 ... Branch wall 30 ... Internal combustion engine 32 ... Bolt 34 ... Intake port 36 ... Female screw 37 ... Facing groove 40 ... Gasket 41 ... Outer peripheral seal portion 42 ... Branch seal portion 50 ... Grooves 51, 71 ... Outer groove portion 71A ... Inner portion 71B ... Outer portion 52 ... Branch groove portion 53 ... Through holes 55, 75 ... Low rigidity portions 56, 76 … Small compression section

Claims (8)

The connection end of the intake pipe is screwed and fixed to the internal combustion engine in a manner in which the intake pipe is connected to the intake port of the internal combustion engine, and the intake port is connected between the internal combustion engine and the connection end of the intake pipe. In the intake pipe connection structure of an internal combustion engine in which a gasket made of an elastic material is interposed in a compressed state in a manner surrounding the intake passage composed of the intake pipe and the intake pipe.
Of the respective parts of the connection end of the intake pipe, the small compression part forming at least a part of the high-rigidity high-rigidity part compresses the gasket as compared with the low-rigidity part having a lower rigidity than the high-rigidity part. The intake pipe connection structure of an internal combustion engine, which is characterized by a small degree. The internal combustion engine according to claim 1, wherein in the small compression portion, the distance between the internal combustion engine and the connection end of the intake pipe in the intermediate portion of the gasket is longer than that in the low rigidity portion. Intake pipe connection structure. The connection end of the intake pipe has a groove into which the gasket fits.
The intake pipe connection structure of an internal combustion engine according to claim 2, wherein the small compression portion has a deeper groove as compared with the low rigidity portion. The internal combustion engine according to claim 3, wherein the bottom of the groove has a shape in which the depth of the groove gradually becomes shallower as it approaches the same portion at the boundary between the small compression portion and the other portion. Intake pipe connection structure. The intake pipe has a tubular main pipe wall portion, a branch wall portion that branches the inside of the main pipe wall portion into two passages, and a connection end of the intake pipe at a position sandwiching the branch wall portion between them. It has a pair of fastening and fixing portions for screwing and fixing to the internal combustion engine.
The gasket has an outer peripheral seal portion extending along the entire circumference along the connection end of the main pipe wall portion, and a branch seal portion extending along the connection end of the branch wall portion.
The intake pipe connection structure of an internal combustion engine according to any one of claims 1 to 4, wherein the small compression portion is a connection end of the branch wall portion. In an intake manifold having an intake pipe and having a structure in which a connecting end of the intake pipe is screwed and fixed to the internal combustion engine with a gasket made of an elastic material interposed between the intake pipe and the internal combustion engine. ,
A groove into which the gasket is fitted is provided at the connection end of the intake pipe.
Of the respective parts of the connection end of the intake pipe, the small compression part forming at least a part of the high-rigidity high-rigidity part has a depth of the groove as compared with the low-rigidity part having a lower rigidity than the high-rigidity part. Intake manifold characterized by a deeper rigidity. The intake manifold according to claim 6, wherein the bottom of the groove has a shape in which the depth of the groove gradually becomes shallower as it approaches the same portion at the boundary between the small compression portion and the other portion. .. The intake pipe has a tubular main pipe wall portion, a branch wall portion that branches the inside of the main pipe wall portion into two passages, and a connection end of the intake pipe at a position sandwiching the branch wall portion between them. It has a pair of fastening and fixing portions for screwing and fixing to the internal combustion engine.
The groove has an outer peripheral groove portion extending over the entire circumference at the connection end of the main pipe wall portion, and a branch groove portion extending at the connection end of the branch wall portion.
The intake manifold according to claim 6 or 7, wherein the small compression portion is a connection end of the branch wall portion.

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