JP2024053131A - Fixing structure of exhaust manifold and exhaust manifold - Google Patents

Abstract

To provide a fixing structure of an exhaust manifold which can rigidly fix a joining part of members which repeat expansion and contraction by a temperature rise and cooling irrespective of whether or not an expensive alloy is used, and the exhaust manifold using the same.SOLUTION: In a fixing structure of an exhaust manifold which is fixed to a cylinder head with bolts, the fixing structure is composed of a fixing part 20 which is extended outward from the exhaust manifold. The fixing part 20 comprises a flange part 21 having insertion holes 22 into which bolts B are inserted, and a pair of wall face parts 23 which are formed so as to cover both-side faces of the inserted bolts, and separated from each other. The pair of wall face parts 23 are continued to the flange part 21 at their one-side ends, and contact with the cylinder head at the other ends.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exhaust manifold fixing structure and an exhaust manifold.

Exhaust system parts for internal combustion engines used in passenger cars, trucks, and other construction, industrial, and agricultural vehicles include turbo housings and exhaust manifolds. These exhaust system parts repeatedly expand and contract as they heat up and cool down, which can lead to gas leaks between parts at the joints between them due to the thermal expansion of the fastening parts. Furthermore, in recent years, exhaust gas temperatures have been rising in response to improved fuel efficiency due to environmental regulations, and exhaust system parts are subject to increasingly greater temperature changes, creating a demand for exhaust system parts that are less susceptible to gas leaks.

Therefore, in order to improve thermal deformation resistance and prevent gas leakage, for example, the invention described in Patent Document 1 uses ferritic spheroidal graphite cast iron in which V and the like are added to high SiMo cast iron for exhaust system parts, and the invention described in Patent Document 2 uses ferritic spheroidal graphite cast iron in which V, Nb, and W are added to high SiMo cast iron for exhaust system parts.

Patent No. 3936849 Patent No. 5232620

However, these spheroidal graphite cast irons are known to be prone to casting defects (e.g. shrinkage cavities), which have a significant impact on casting productivity. In addition, although they can improve thermal deformation resistance, they tend to be expensive because they require the addition of expensive alloys.

The object of the present invention is to solve the problems of the above-mentioned conventional technology and to provide an exhaust manifold fixing structure that can firmly fix the joints between components that repeatedly expand and contract due to heating and cooling, regardless of whether or not high-cost alloys are used.

The fixing structure of the exhaust manifold of the present invention is a fixing structure of an exhaust manifold fixed to a cylinder head by a bolt, the fixing structure being composed of a fixing portion extending outward from the exhaust manifold, the fixing portion being characterized in that it has a flange portion having an insertion hole into which the bolt is inserted, and a pair of wall portions spaced apart from each other, formed to cover both sides of the inserted bolt, one end of the pair of wall portions being continuous with the flange portion, and the other end being in contact with the cylinder head. In the present invention, the pair of wall portions of the fixing portion are not shaped to cover the entire circumference of the bolt, but are shaped to cover only a part of the bolt by being spaced apart from each other. This makes it possible to reduce the contact area of the fixing portion with the cylinder head compared to when the entire circumference of the bolt is covered, suppressing the temperature rise of the members constituting the fixing portion and suppressing the thermal expansion of the bolt, and as a result, it is possible to firmly fix the members together.

The pair of wall portions are preferably inclined so that their height decreases from the one end toward the cylinder head. By configuring in this way, the contact area of the fixing portion with the cylinder head is further reduced than described above, which further suppresses the temperature rise of the members constituting the fixing portion and suppresses the thermal expansion of the bolt, thereby firmly fixing the members together to prevent gas leakage.

It is preferable that the length of the flange portion in the thickness direction is shorter than the length of the wall portion. By making the thickness of the flange portion shorter than the length of the wall portion, thermal expansion of the bolt can be preferably suppressed, and the members can be firmly fixed to each other so that gas leakage does not occur.

The exhaust manifold of the present invention is characterized in that it has a plurality of the exhaust manifold fixing structures described above. By having a plurality of exhaust manifold fixing structures, the components can be firmly fixed together to prevent gas leakage.

Of the fixing parts, it is preferable that the insertion hole of the central fixing part located in the longitudinal center of the exhaust manifold has a smaller hole diameter than the insertion holes of the other fixing parts. By configuring it in this way, it is possible to perform positioning with high precision.

Of the fixing parts, the insertion holes of the left end fixing part and/or the right end fixing part located at both ends of the longitudinal direction of the exhaust manifold are preferably elliptical in shape, with the longitudinal width of the ellipse being longer than the hole diameter of the insertion holes of the other fixing parts. By configuring at least one of the insertion holes of the left end fixing part and the right end fixing part in this way, it is possible to position the fixing part vertically and horizontally using the insertion hole of this fixing part and the insertion hole of the central fixing part.

It is preferable that the exhaust manifold has a reduced-weight portion in the partition wall between the exhaust passages or between the EGR passage and the exhaust passage on the surface that contacts the cylinder head. This configuration makes the exhaust manifold itself less susceptible to direct thermal effects from the cylinder head, suppresses thermal expansion of the exhaust manifold, and suppresses misalignment between the cylinder head and the exhaust manifold.

The exhaust manifold fixing structure of the present invention allows the joints between components that repeatedly expand and contract due to heating and cooling to be firmly fixed so that gas leakage does not occur.

1A and 1B are a perspective view and a perspective view, respectively, of an exhaust manifold according to an embodiment of the present invention, respectively, as viewed from the opposite direction; 1 is a view of an exhaust manifold according to an embodiment as viewed from a cylinder head side. FIG. FIG. 2 is a perspective view showing a fixing structure of the exhaust manifold according to the embodiment. FIG. 2 is a top view showing the fixing structure of the exhaust manifold according to the embodiment. 1 is a cross-sectional view showing a fixing structure of an exhaust manifold according to an embodiment.

An exhaust manifold according to an embodiment of the present invention will be described with reference to Figures 1 to 5. However, this embodiment is merely an example, and the present invention is not limited to this embodiment. In addition, in the embodiment, the same reference numbers are used for the same components, but when distinguishing between the same components based on the installation position of the components, the reference numbers are distinguished by adding the letters a, b, ....

As shown in Figures 1 to 5, the exhaust manifold 10 of this embodiment includes an exhaust manifold body 11. The exhaust manifold body 11 has a base end 12 formed in one exhaust passage and a plurality of branch pipes 14 formed by branching off from each other. A base end flange portion 121 is provided on the base end portion 12, and the base end flange portion 121 and a flange portion of a turbocharger (not shown) are fixed with bolts.

An exhaust passage 15 is formed inside the branch pipe 14. Each of the exhaust passages 15 is connected to a corresponding exhaust port of a cylinder head (not shown). In addition, an EGR (Exhaust Gas Recirculation) (not shown) is connected to the exhaust manifold body 11, so an EGR exhaust passage 16 is formed to send exhaust gas to the EGR. A reduced-weight portion 17 is provided between the exhaust passage 15a adjacent to the EGR exhaust passage 16 and the EGR exhaust passage 16, and a reduced-weight portion 18 is provided between the exhaust passages 15b and 15c.

The exhaust manifold body 11 is provided with fixing parts 20 for fixing the cylinder head and the exhaust manifold. The fixing parts 20a to 20d are provided on the upper part of the exhaust passages 15a to 15d, respectively, and the fixing parts 20e to 20h are provided on the lower part of the exhaust passages 15a to 15d, respectively. In addition, fixing parts 20i and 20j are provided on the upper left side (above the end side of the exhaust manifold body 11) and the lower right side (below the exhaust passage 15a side adjacent to the exhaust manifold body 11) of the EGR exhaust passage 16 in FIG. 2. In this way, by providing the fixing parts 20 corresponding to the exhaust passage 15 and the EGR exhaust passage 16, gas leakage can be efficiently prevented.

Each fixing portion 20 extends toward the outside of the exhaust manifold body 11. Specifically, each fixing portion 20 has a flange portion 21 that is formed on the upper side of the exhaust manifold body 11 and extends upward, and that is formed on the lower side of the exhaust manifold body 11 and extends downward. The flange portion 21 has a bolt insertion hole 22 in its center.

As shown in FIG. 5, the fixing portion 20 is fixed to the cylinder head by a bolt B. The bolt B is inserted into the insertion hole 22 from the exhaust manifold 10 side toward the cylinder head side. In this embodiment, a stud bolt is used as the bolt B, and is fixed using both a collar K and a hexagonal nut N. The bolt B is inserted from the insertion hole 22, and the seat surface of the collar K contacts and is held by the flange portion 21. By providing the flange portion 21 in this manner, the axial force of the bolt B can be uniformly transmitted and held, and as a result, the seat surface of the flange portion 21 due to the bolt B, collar K, and hexagonal nut N can be prevented from collapsing, and the axial force of the bolt B can be maintained.

The fixing portion 20 also has a pair of wall portions 23 whose one end in the width direction is continuous with the flange portion 21. Each of the pair of wall portions 23 is shaped to cover only the sides of the inserted bolt. The pair of wall portions 23 are also spaced apart from each other, so an opening 24 is formed between the pair of wall portions 23. Therefore, when a bolt B is inserted through the insertion hole 22, the bolt B is exposed from the opening 24. In other words, the pair of wall portions 23 are not connected on the outer periphery side (upper part in FIG. 5) of the exhaust manifold main body 11 due to the opening 24, and when the bolt B is inserted into the insertion hole 22, the bolt B is exposed from the opening 24.

The pair of wall portions 23 contact the cylinder head at the end opposite the flange portion 21 (the other end in the width direction). In this embodiment, the wall portion 23 of the fixing portion 20 is shaped to cover only the side of the bolt rather than the entire periphery of the bolt at the portion where it connects to the cylinder head. This makes it possible to reduce the contact area of the fixing portion 20 with the cylinder head compared to when the entire surface of the bolt B is covered, suppressing the temperature rise of the components constituting the fixing portion 20 and reducing thermal expansion, thereby enabling the components to be firmly fixed.

If the wall portion were to be cylindrical and continuous from the flange portion and cover the entire circumference of the bolt, the higher the temperature of the heat transferred from the cylinder head, the lower the strength would be due to deformation caused by thermal expansion of the bolt and deterioration of the mechanical properties of the parts. In addition, there was a problem that the bolt would undergo plastic deformation due to the fastening axial force applied to the bolt, which would reduce the axial force and the fastening force. In contrast, in this embodiment, the contact area between the pair of wall portions 23 and the cylinder head is small, making it difficult for heat to be transferred to the fixing portion 20, so that deformation due to thermal expansion of the bolt B can be suppressed. As a result, the fixing portion 20 can maintain the strength of the bolt B itself and prevent plastic deformation, so that the exhaust manifold 10 can be firmly fixed to the cylinder head. And by providing such a fixing portion 20, it is possible to obtain an exhaust manifold 10 that does not leak exhaust gas, has few defects as a cast part, and is highly productive, using bolts (e.g., chrome molybdenum steel) and exhaust system part materials made of cost-reduced materials without changing the materials of the fastening parts and the exhaust manifold 10 themselves.

In addition, in the fixing portion 20, the pair of wall portions 23 do not cover the entire outer periphery of the bolt, but rather an open portion 24 is formed and the pair of wall portions 23 cover only a portion of the outer periphery of the bolt, thereby improving the heat dissipation of the bolt B. This makes it possible to suppress deformation of the bolt B due to thermal expansion. The fixing portion 20 can maintain the strength of the bolt B itself and prevent plastic deformation, allowing it to be firmly fixed.

In addition, the contact surface of the fixing part 20 that comes into contact with the cylinder head is a machined surface, which can lead to casting defects (e.g. shrinkage cavities) and reduce productivity. In the fixing part 20 of this embodiment, the wall part is cylindrical and continues from the flange part 21, and the area of the contact surface is reduced compared to when the wall part covers the entire circumference of the bolt. This reduces the impact of defects on productivity. Furthermore, the provision of the open part 24 reduces the material weight and the amount of processing, resulting in reduced costs.

The pair of wall portions 23 are provided so that one end in the width direction is continuous from the same height as the flange portion 21, and the other end, i.e., the cylinder head side, is lower than this one end. In other words, the pair of wall portions 23 are provided with an inclination so that they are lower toward the cylinder head side. By inclining the pair of wall portions 23 in this way, it is possible to further reduce the area of the contact surface between the wall portions 23 and the cylinder head, reducing the temperature rise of the members constituting the fixing portion 20 and reducing the range of thermal expansion and contraction, and as a result, the members can be firmly fixed.

The pair of wall portions 23 are preferably formed so that the height H1 of the other end in the width direction, i.e., the cylinder head side (height from the lower end of the insertion hole 22 to the upper end of the wall portion 23 at the cylinder head side end) is higher than the bolt center H2 of the bolt B inserted into the insertion hole 22, but lower than the height H3 of the flange portion 21 (height from the lower end of the insertion hole 22 to the upper end of the flange portion). If the height H1 on the cylinder head side is lower than the bolt center H2 of the inserted bolt B, sufficient surface pressure will not be applied between the cylinder head and the exhaust manifold 10, which may cause gas leakage. Furthermore, for example, the angle of inclination of the pair of wall portions 23 is preferably 110 to 130°.

The distance between the open portions 24, i.e., the distance between the pair of wall portions 23, is preferably 150 to 170% of the bolt diameter. If it is more than 170%, sufficient surface pressure cannot be applied between the cylinder head and the exhaust manifold, which may cause gas leakage, and if it is less than 150%, it is susceptible to the thermal effects of the cylinder head.

The length of the flange portion 21 in the thickness direction is preferably shorter than the length of the wall portion 23, for example, about 8 to 12 mm, preferably about 10 mm. If the thickness of the flange portion 21 is longer than the length of the wall portion, heat dissipation from the bolt may be insufficient. In particular, if the thickness is greater than about 12 mm, heat dissipation from the bolt may be insufficient, and if the thickness is less than 8 mm, the seat strength may not be maintained when the collar K or nut N comes into contact with the seat of the flange 21 and the seat of the bolt head, etc., and the seat may be deformed. The length of the flange portion 21 in the thickness direction does not necessarily have to be shorter than the length of the wall portion 23, but if it is, the thermal expansion of the bolt can be preferably suppressed and the members can be firmly fixed to each other without gas leakage.

Each insertion hole 22 also functions as a positioning hole when fixing the exhaust manifold 10. In this embodiment, the insertion hole 22b of the fixing part (central fixing part) 20b located on the longitudinal center side of the exhaust manifold 10 has a smaller hole diameter than the other insertion holes 22, and the clearance for the inserted bolt B is small. Therefore, the insertion hole 22b of the fixing part (central fixing part) 20b can be positioned in the up, down, left and right directions. When fixing the exhaust manifold 10 to the cylinder head, a bolt is first inserted into this insertion hole 22b and positioned up, down, left and right. In this embodiment, positioning is performed based on the insertion hole 22b, but it is possible to position using any of the insertion holes 22 in the longitudinal direction as a reference. In addition, the insertion hole 22d of the fixing part 20d located on the longitudinal end side of the exhaust manifold 10 is elliptical, and the longitudinal width of the ellipse is larger than the diameter of each of the other insertion holes 22. In this case, since the longitudinal width of the ellipse of the insertion hole 22d is long, even if the exhaust manifold undergoes significant thermal expansion, the hole can absorb the expansion, and misalignment between the cylinder head and the exhaust manifold 10 can be suppressed. In this embodiment, only the insertion hole 22d of the fixing part 20d, which is the right end fixing part, is elliptical, but the insertion hole 22i of the fixing part 20i, which is the left end fixing part, may also be elliptical.

In addition, by providing the recessed portions 17, 18 in the exhaust manifold 10, it is possible to prevent defects from occurring on the machined surface of the exhaust manifold body 11 and reduce the material weight and amount of processing.

The present invention is not limited to the above-described embodiment. The configuration of the exhaust manifold body 11 is an example, and the structure is not limited. The fastening parts are also an example, and the shape of the bolts, etc. are not limited.

REFERENCE SIGNS LIST 10 exhaust manifold 11 exhaust manifold body 12 base end 14 branch pipe 15 exhaust passage 16 EGR exhaust passage 17, 18 reduced thickness portion 20 fixing portion 21 flange portion 22 insertion hole 23 wall portion 24 open portion B bolt K collar N hexagonal nut

Claims (7)

An exhaust manifold fixing structure that is fixed to a cylinder head by bolts,
The fixing structure includes a fixing portion extending outward from the exhaust manifold,
The fixing portion includes a flange portion having an insertion hole into which the bolt is inserted, and a pair of wall portions formed to cover both side surfaces of the inserted bolt and spaced apart from each other,
The pair of wall portions have one end connected to the flange portion and the other end in contact with the cylinder head. The exhaust manifold fixing structure according to claim 1, characterized in that the pair of wall portions are inclined so that their height decreases from the one end toward the cylinder head side. The exhaust manifold fixing structure according to claim 1, characterized in that the length of the flange portion in the thickness direction is shorter than the length of the wall portion. An exhaust manifold characterized by having a plurality of exhaust manifold fixing structures according to any one of claims 1 to 3. The exhaust manifold according to claim 4, characterized in that the insertion hole of the central fixing part located in the longitudinal center of the exhaust manifold among the fixing parts has a smaller hole diameter than the insertion holes of the other fixing parts. The exhaust manifold according to claim 4, characterized in that the insertion holes of the left end fixing part and/or the right end fixing part located at both ends of the longitudinal direction of the exhaust manifold among the fixing parts are elliptical in shape, and the longitudinal width of the ellipse is longer than the hole diameter of the insertion holes of the other fixing parts. The exhaust manifold according to claim 4, characterized in that the exhaust manifold has a recessed portion in the partition between the exhaust passages or between the EGR passage and the exhaust passage on the surface that contacts the cylinder head.

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