JP2002195031A - Structure of exhaust manifold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce thermal stress on a mounting bolt, to prevent reduction of strength of the periphery of a bolt boss portion and prevent degradation of sealing performance of exhaust manifold, to dispense with changing the type of the exhaust manifold, and to reduce a cost and reduce man-hours, in structure of the exhaust manifold. SOLUTION: A bolt hole into which the mounting bolt is inserted for installing the exhaust manifold is formed to be a long hole. The major axis of the long hole for the bolt is arranged on the crossline of the center of expansion of the exhaust manifold and the center of the long hole for the bolt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an exhaust manifold, and more particularly to a structure of an exhaust manifold capable of reducing a thermal stress applied to a mounting bolt.

[0002]

2. Description of the Related Art As shown in FIG. 12, an exhaust manifold 104 is provided with a gasket (not shown) on a cylinder head 102 of an engine for a multi-cylinder (for example, three cylinders: # 1, # 2, # 3) of a vehicle. Mounted through. The exhaust manifold 104 is provided with first to third port holes corresponding to the first to third exhaust ports of the cylinder head 102, a manifold mounting flange 106 joined to the cylinder head 102, and one end of each of the first to third exhaust ports. First to third exhaust branch pipes 110-1 to 110-3 connected to the manifold mounting flange 106 corresponding to the third port holes and connected to the exhaust manifold 108 at the other end. ing. The manifold mounting flange 106 has a first
First to third flange portions 11 corresponding to third to third port holes
2-1 to 112-3.

The first flange 112-1 has a circular first hole formed as a bolt hole around the first port hole.
First upper bolt boss 114 having an upper bolt hole formed therein
-1U and a first lower bolt boss portion 114-1D in which a first lower bolt hole having a circular shape is formed.
A second upper bolt boss 114-2U formed with a circular second upper bolt hole as a bolt hole around the second port hole is formed in the second flange 112-2. A second lower bolt boss 114-2D in which a second lower bolt hole is formed is provided. The third flange portion 112-3 has a third upper bolt boss portion 114-3U formed with a circular third upper bolt hole as a bolt hole around the third port hole, and a circular shape. Third
Third lower bolt boss 114 having a lower bolt hole formed therein
-3D. The exhaust manifold 104 includes first upper and first lower mounting bolts 116-1U and 116-1 inserted through the first upper and first lower bolt holes.
-1D and the second upper and second lower bolt holes
Upper, second lower mounting bolts 116-2U, 116-2D
And the third upper side, the third upper side inserted through the third lower bolt hole,
The third lower mounting bolts 116-3U and 116-3D are mounted on the cylinder head 102 via a gasket.

In this case, the exhaust manifold 10
4, the thermal expansion of the exhaust manifold 104 is restrained by the mounting bolts 116. That is, in the case of the exhaust manifold 104 made of a metal material having a relatively small linear expansion coefficient, the amount of thermal expansion is not so large. Since it was not large, it was possible to suppress the deformation of the exhaust manifold 104 by restraining the thermal expansion by each mounting bolt 116.

[0005] The structure of such an exhaust manifold is described in, for example, Japanese Utility Model Laid-Open Publication No. 1994-14434.
It is disclosed in Japanese Utility Model Publication No. 7-32899. Actual opening 1
Japanese Patent Application Laid-Open No. 994-14434 has at least one slit which passes through a bolt hole of a manifold mounting flange. 7-3289
No. 9 discloses a lightening portion provided to separate the manifold mounting flange from the exhaust manifold.

[0006]

In recent years, regarding the structure of an exhaust manifold, fuel efficiency and exhaust gas purification performance (increase in the catalytic reaction temperature at the time of cold start) have been studied.
The exhaust gas temperature is on the rise, with the aim of improving
The situation is getting tougher for strength.

As a method for improving the high-temperature strength of the exhaust manifold, it is conceivable to use a metal material having excellent high-temperature strength. However, when the metal material has a large linear expansion coefficient (for example, a metal of austenitic casting). ), The exhaust manifold has a large thermal expansion amount, so that a large load is applied to the restraining portion of the mounting bolt, and when the mounting bolt is configured to suppress the deformation of the bolt boss, the mounting bolt may be damaged.

As a general technique for solving the above problem, there is a method of increasing the diameter of the bolt boss to release the in-plane deformation of the mating surface between the cylinder head and the manifold mounting flange. In the method of increasing the diameter of the manifold, unnecessary portions of the meat that are not related to the thermal expansion of the manifold mounting flange will also be removed.If the manifold mounting flange does not have enough space, it is necessary to secure the sealing performance. In such a case, it is necessary to change the type of the exhaust manifold, and the cost and man-hours are disadvantageously increased.

[0009]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned disadvantages, the present invention provides a multi-cylinder engine having a plurality of port holes corresponding to respective exhaust ports of a cylinder head. A manifold mounting flange to be joined to the head is provided, and one end side is connected to the manifold mounting flange corresponding to each port hole, and an exhaust branch pipe is connected to the other end side to which an exhaust manifold is connected, The manifold mounting flange is provided with a plurality of bolt bosses each having a bolt hole formed therein. In the structure of the exhaust manifold attached to the cylinder head by a mounting bolt inserted through the bolt hole, the bolt hole is formed by a bolt elongated hole. And the major axis of the bolt slot is defined as the center of expansion of the exhaust manifold and the center of the bolt slot. Characterized by being disposed on connection through.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a bolt hole through which a mounting bolt for mounting an exhaust manifold is inserted is formed in an elongated bolt hole, and the major diameter of the elongated bolt hole is defined as the expansion center of the exhaust manifold and the center of the elongated bolt hole. , The manifold mounting flange is not removed unnecessarily, the heat of the exhaust manifold can be released, the thermal stress on the mounting bolts can be reduced, and the bolt boss can be removed. Without reducing the peripheral strength of the exhaust manifold and the sealing performance of the exhaust manifold, eliminating the need to change the type of exhaust manifold, etc.
Costs and man-hours can be reduced.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; 1 to 6 show a first embodiment of the present invention. In FIG. 5, reference numeral 2 denotes a cylinder head of an engine for a multi-cylinder (three cylinders: # 1, # 2, # 3) mounted on a vehicle, and reference numeral 4 denotes a side of the cylinder head 2 via a gasket (not shown). It is an exhaust manifold that can be attached by mounting.

The exhaust manifold 4 is provided with an odd number of first to third port holes 6-1 to 6-3 corresponding to first to third exhaust ports (not shown) of the cylinder head 2. A manifold mounting flange 8 having a mating surface joined to the head 2, and one end connected to the manifold mounting flange 8 corresponding to the first to third port holes 6-1 to 6-3 and the other end And a first to third exhaust branch pipes 12-1 to 12-3 to which an exhaust manifold 10 is connected. The exhaust manifold 10 is disposed to face the longitudinal direction of the manifold mounting flange 8 and has an exhaust pipe mounting portion 14 at an end portion. The first to third port holes 6-1 to 6-3 have first to third port centers C1 to C3.

In the manifold mounting flange 8, a flat first flange portion 16-1 is provided corresponding to the first port hole 6-1 on one end side, and the first flange portion 16-1 is provided.
Adjacent to the second port hole 6-2.
A flange portion 16-2 is provided.
A flat third flange portion 16-3 corresponding to the third port hole 6-3 is provided adjacent to 6-2, and a first flange portion 16-1 and a second flange portion 16-2 are provided. Is provided, and the other-side connecting member 18-2 for connecting the second flange portion 16-2 and the third flange portion 16-3 is provided.

The first flange portion 16-1 is provided with a first upper bolt boss portion 20-1U above the first port hole 6-1 and is provided with respect to the first port hole 6-1. A first lower bolt boss 20-1D is provided diagonally below the end.
Is provided.

The second flange portion 16-2 is provided with a second upper bolt boss portion 20-2U diagonally above the first upper bolt boss portion 20-1U with respect to the second port hole 6-2. In addition, a second lower bolt boss 20-2D is provided diagonally below the second port hole 6-2 and away from the first lower bolt boss 20-1D.

The third flange portion 16-3 is provided with a third upper bolt boss portion 20-3U diagonally above the second upper bolt boss portion 20-2U side with respect to the third port hole 6-3. In addition, a third lower bolt boss 20-3D is provided diagonally below the third port hole 6-3 and away from the second lower bolt boss 20-2D.

In this exhaust manifold 4, as shown in FIG. 1, a second upper bolt boss 20-2U and a second lower bolt boss 20-2D at substantially central portions are provided.
A second upper bolt hole 22-2U and a second lower bolt hole 22-2D having a minimum tolerance to be assembled with the bolt diameter, and the second upper bolt boss portion 20 is formed.
-2U and the second lower bolt boss 20-2D are used as reference bolt bosses. A reference connection BL passing through the center P-2U of the second upper bolt boss portion 20-2U and the center P-2D of the second lower bolt boss portion 20-2D is drawn, and the second upper bolt boss portion 20- of the reference connection BL is drawn. 2U center P-2U
A center point between the center P-2D of the second lower bolt boss 20-2D and the center P-2D of the second lower bolt boss portion 20-2D is defined as an expansion center O of the exhaust manifold 4.
That is, the portion forming the port hole 6 is the flange portion 16.
In the case of the shape of the exhaust manifold that is not directly or indirectly connected to the flange portion 16 except for the opening of the stainless steel material, for example, a stainless steel material (SUS
In the exhaust manifold or the like, the two reference bolt bosses are formed in a circular shape so as to minimize the tolerance, thereby restraining the expansion in the plane of the flange portion 16, and as described above, the expansion center of the exhaust manifold 4 is increased. O is replaced with a second upper bolt boss 20-
It is set at the midpoint between 2U and the second lower bolt boss 20-2D.

Further, in the exhaust manifold 4, as shown in FIG. 6, the amount of thermal expansion varies depending on each part. That is, when it is considered that the second upper bolt boss portion 20-1U and the second lower bolt boss portion 20-2D at the central portion as the reference bolt boss portions are fixed without thermal expansion (indicated by ●), The part of the exhaust manifold 10 at the second exhaust branch pipe 12-2 slightly expands (X
), And the portion of the exhaust manifold 10 between the first exhaust branch pipe 12-1 and the second exhaust branch pipe 12-2 expands a little more (indicated by △). -1U and the first lower bolt boss portion 20-1D expand further (shown by □), while the exhaust manifold 10 at the third exhaust branch pipe 12-3 expands slightly (△).
), And further expand at each of the third upper bolt boss 20-3U and the third lower bolt boss 20-3D (indicated by □).

In the second upper bolt boss portion 20-2U and the second lower bolt boss portion 20-2D, which are the reference for thermal expansion of the exhaust manifold 4, the center P-2U of the second upper bolt boss portion 20-2U is As a bolt hole,
A circular second upper bolt hole 22-2U having a predetermined radius R is formed on the reference connection BL, and a center hole P-2D of the second lower bolt boss 20-2D is formed as a bolt hole. A circular second lower bolt hole 22-2D having a predetermined radius R is formed on the reference connection BL.

On the other hand, in each of the other bolt bosses, each bolt elongated hole (ellipse) is formed as a bolt hole in order to reduce thermal stress applied to each mounting bolt.

That is, the first upper connection L-1 passing through the expansion center O and the center P-1U of the first upper bolt boss 20-1U.
U, and the first upper bolt boss 20-1U has a focal point FU-1A and a focal point F on the first upper connection L-1U.
An elliptical first upper bolt slot 22-1U having a focal length M-1U with U-1B is formed. This first
The major diameter of the upper bolt elongated hole 22-1U is a length that allows for the shift due to thermal expansion of the first upper bolt boss portion 20-1U.

A first lower connection L-1 passing through the expansion center O and the center P-1D of the first lower bolt boss 20-1D.
D, the first lower bolt boss 20-1D has a focal point FD-1A and a focal point F on the first lower connection L-1D.
An oval first lower bolt slot 22-1D having an inter-focal distance M-1D with D-1B is formed. This first
The major axis of the lower bolt elongated hole 22-1D is a length that allows for a shift due to thermal expansion of the first lower bolt boss portion 20-1D.

Further, a first upper connection L-3 passing through the center of expansion O and the center P-3U of the third upper bolt boss 20-3U.
U, and the third upper bolt boss 20-3U has a focal point FU-3A and a focal point F on the third upper connection L-3U.
An elliptical third upper bolt slot 22-3U having a focal length M-3U with U-3B is formed. This third
The major diameter of the upper bolt elongated hole 22-3U is a length that allows for a shift due to thermal expansion of the third upper bolt boss portion 20-3U.

A third lower connection L-3 passing through the center of expansion O and the center P-3D of the third lower bolt boss 20-3D.
D, and the third lower bolt boss 20-3D has a focal point FD-3A and a focal point F on the third lower connection L-3D.
An elliptical third lower bolt slot 22-3D having an inter-focal distance M-3D with D-3B is formed. This third
The major axis of the lower bolt elongated hole 22-3D is a length that allows for the shift due to the thermal expansion of the third lower bolt boss portion 20-3D.

As shown in FIG. 1, the major axis of each of the bolt long holes is formed so as to correspond to the distance from the expansion center O.

A first upper mounting bolt 24-1U whose center coincides with the focal point FU-1A at the initial stage of tightening is inserted into the first upper bolt slot 22-1U. Further, the first lower mounting bolt 24-1D whose center coincides with the focal point FD-1A at the initial stage of tightening is inserted into the first lower bolt long hole 22-2U. The first upper mounting bolt 24-1U and the first lower mounting bolt 24-1D are inserted into the side surface of the cylinder head 2.

A second upper mounting bolt 24-2U is inserted into the second upper bolt hole 22-2U. The second lower mounting bolt 24-2 is provided in the second lower bolt hole 22-2D.
D is inserted. These second upper mounting bolts 24-2U
The second lower mounting bolt 24-2D is inserted into the side surface of the cylinder head 2.

A third upper mounting bolt 24-3U whose center coincides with the focal point FU-3A at the initial stage of tightening is inserted into the third upper bolt slot 22-3U. In addition, a third lower mounting bolt 24-3D whose center coincides with the focal point FD-3A at the time of initial tightening is inserted into the third lower bolt long hole 22-3D. The third upper mounting bolt 24-3U and the third lower mounting bolt 24-3D are inserted into the side surface of the cylinder head 2.

Next, the operation of the first embodiment will be described.

The second part of the central part which is the reference bolt boss part
Upper bolt boss 20-2U and second lower bolt boss 2
Except for 0-2D, the first upper side of the other bolt boss portion, the first
The lower bolt bosses 20-1U and 20-1D and the third upper and third lower bolt bosses 20-3U and 20-3D have first upper and first lower bolt slots 22-1U and 22-, respectively.
1D and third upper and third lower bolt slots 22-3U, 2
2-3D is formed, and the major axis of each bolt long hole 22 is arranged on each connection L passing through the center of expansion O and each center P of each bolt boss portion 20, so that when the manifold mounting flange 8 is thermally expanded, Each focal point FB of the bolt elongated hole 22 is located at the center of each mounting bolt 24, so that thermal stress applied to each mounting bolt 24 due to thermal expansion of the manifold mounting flange 8 can be reduced. That is, since the above-described bolt elongated holes 22 are not uniformly formed to relieve the thermal stress, the unnecessary expansion of the manifold mounting flange 8 is not performed, and the expansion of the exhaust manifold 4 due to heat is prevented. The bolts 20 can be relieved, so that the peripheral strength of each bolt boss portion 20 and the exhaust manifold 4
Of the exhaust manifold 4 without changing the sealing performance of the exhaust manifold 4 and the cost and man-hours can be reduced. In this configuration, the manifold mounting flange 8 is separated from the pipe portion (after the pipe portion comes out of the manifold mounting flange 8),
Applies mainly to sheet metal exhaust manifolds.

Further, as shown in FIG. 1, since the major axis of each of the above-described bolt elongated holes 22 is formed to be larger as the distance from the expansion center O is increased, each of the mounting bolts 24 is shifted in accordance with the direction of displacement of each of the bolt bosses 20. Can be effectively reduced.

Further, since the expansion center O is provided at the central portion of the exhaust manifold 4 having the odd-numbered port holes 6, the long bolt holes 22 can be formed with good left-right balance.

FIG. 7 shows a second embodiment of the present invention.

In the following embodiments, portions having the same functions as those in the above-described first embodiment will be described with the same reference numerals.

The features of the second embodiment are as follows. That is, except for the second upper bolt boss portion 20-2U and the second lower bolt boss portion 20-2D in the central portion which are the reference bolt boss portions, the other bolt boss portions 20 are formed with the respective bolt elongated holes 22, The long diameter of the bolt long hole 22 was arranged in accordance with the direction of thermal deviation of the bolt boss portion 20.

That is, the first upper bolt boss 20-1U
And the center P-1 of the first upper bolt boss 20-1U.
U and a first upper connection L passing through the first upper expansion center O-1U.
-1U, and on the first upper connection line L-1U, a focal distance M-1 between the focal points FU-1A and FU-1B.
An oval first upper bolt slot 22-1U having a U is formed.

In the case of an exhaust manifold in which the portion forming the port hole is directly or indirectly connected to the flange except at the opening of the flange,
For example, in an exhaust manifold or the like made of cast iron, a plurality of expansion centers are formed at positions deviated from the midpoint of the reference bolt. In this case, the long-diameter direction of the bolt long hole is formed in accordance with the thermal transition direction of each bolt boss, and free extension of the flange in the in-plane direction of the flange is ensured. Here,
The expansion center is a point at which the total sum becomes minimum when considering a vector U in which each part of the exhaust manifold is deformed by thermal expansion. In the present invention, since the restraint of the bolt for fixing the exhaust manifold is discussed, the center of the bolt is the center point in the vector direction in which the bolt moves due to thermal expansion. The thermal expansion Ui is obtained by multiplying a minute volume Δv by a linear expansion coefficient α and a temperature difference Δt with respect to a reference temperature when the exhaust manifold is subdivided, that is, Ui = α * Δv * Δt. Desired. By the way, when the temperature of the exhaust manifold is constant,
The center of expansion is the center of gravity of the exhaust manifold. However, since the actual temperature of the exhaust manifold has a complicated distribution, and the coefficient of linear expansion changes with the temperature change, it has been conventionally difficult to find the center of expansion. However, in recent years, analysis methods using the finite element method have been developed, and with this, it has become possible to easily determine the direction of thermal displacement and the amount of displacement (the amount of expansion). Then, based on the direction of thermal displacement and the amount of displacement (the amount of expansion), the center of expansion can be easily made. Therefore, in the present invention, the center of expansion is obtained from this method and set at a predetermined location.

The first lower expansion center O-1D is drawn in the direction of thermal deviation of the first lower bolt boss portion 20-1D, and the center P-1D of the first lower bolt boss portion 20-1D is drawn.
And a first lower connection L- passing through the first lower expansion center O-1D.
1D, and focuses on the first lower connection L-1D.
Inter-focal distance M-1D between D-1A and focal point FD-1B
The first lower bolt elongated hole 22-1D of an elliptical shape having the following is formed.

Further, the third upper expansion center O-3U is drawn in the direction of thermal deviation of the third upper bolt boss 20-3U, and the center P-3U of the third upper bolt boss 20-3U is drawn.
Upper connection L- passing through the third upper expansion center O-3U.
3U, and the focus F on the third upper connection L-3U.
The focal distance M-3 between U-3A and focal FU-3B
An oval third upper bolt slot 22-3U having a U is formed.

Further, the third lower expansion center O-3D is drawn in the direction of thermal deviation of the third lower bolt boss portion 20-3D, and the center P-3D of the third lower bolt boss portion 20-3D is drawn.
And a third lower connection L- passing through the third lower expansion center O-3D.
3D is drawn, and on this third lower connection L-3D, the focus F
Distance between focal points M-3D between D-3A and focal point FD-3B
The third lower bolt elongated hole 22-3D having an elliptical shape is formed.

According to the structure of the second embodiment, the second upper bolt boss portion 20 at the center portion which is the reference bolt boss portion is provided.
Except for -2U and the second lower bolt boss portion 20-2D, each of the other bolt boss portions 20 has a bolt elongated hole 22 formed therein. The mounting bolt 2 due to thermal expansion
4 can be reduced. That is, since the long bolt holes 22 are not uniformly formed to relieve the thermal stress, the bolt boss portions 20 are not unnecessarily deleted, and the peripheral strength of each bolt boss portion 20 and the sealing performance are reduced. Can be prevented. Further, in such a configuration, the present invention is applied to the shape of the exhaust manifold in which the manifold mounting flange and each pipe portion are in close contact.

FIGS. 8 and 9 show a third embodiment of the present invention.

The features of the third embodiment are as follows. That is, the exhaust manifold 4 is 4
It is attached to an engine for a cylinder (# 1, # 2, # 3, # 4), and includes a manifold mounting flange 8, four first to fourth exhaust branch pipes 12-1 to 12-4, and an exhaust assembly. And a tube 10. The fourth exhaust branch pipe 12-4 is
It is substantially continuous with the exhaust manifold 10. An even number of first to fourth port holes 6-1 to 6-4 are formed in the manifold mounting flange 8, and the first port hole 6-1 is formed.
A first upper bolt boss 20-1U and a first lower bolt boss 20-1D are provided around the
-2, a second upper bolt boss portion 20-2U and a second lower bolt boss portion 20-2D are provided, and a third upper bolt boss portion 20-3U and a third upper bolt boss portion 20-3U are provided around the third port hole 6-2. A lower bolt boss 20-3D is provided, and a fourth upper bolt boss 20-4U is provided around the fourth port hole 6-3.
And a fourth lower bolt boss portion 20-4D, and an end upper bolt boss portion 20-E is provided on the fourth port hole 6-3 side.

In consideration of the overall balance of the thermally expanding manifold mounting flange 8, the third upper bolt boss 20-3U and the third lower bolt boss 20-3D, which are the center bolt bosses, are used as reference bolt bosses. Reference connection BL connecting center P-3U of third upper bolt boss 20-3U and center P-3D of third lower bolt boss 20-3D.
And a third port hole between the center P-3U of the third upper bolt boss 20-3U and the center P-3D of the third lower bolt boss 20-3D on the reference connection BL. The expansion center O is extracted in 6-3. Therefore, as shown in FIG. 8, the expansion center O is disposed substantially at the center of the manifold mounting flange 8 in consideration of the overall balance of the manifold mounting flange 8.

Then, the first upper connection L- passing through the center of expansion O and the center P-1U of the first upper bolt boss 20-1U.
1U is drawn, and the first upper bolt boss 20-1U includes:
On the first upper connection line L-1U, an elliptical first upper bolt elongated hole 22-1U having a focal length M-1U between the focal points FU-1A and FU-1B is formed. The major diameter of the first upper bolt elongated hole 22-1U is a length that allows for the shift due to thermal expansion of the first upper bolt boss portion 20-1U.

A first lower connection L-1 passing through the center of expansion O and the center P-1D of the first lower bolt boss 20-2D.
D, and the first lower bolt boss 20-2D has a focal point FD-1A and a focal point F on the first lower connection L-1D.
An oval first lower bolt slot 22-2D having an inter-focal distance M-1D with respect to D-1B is formed. This first
The major axis of the lower bolt elongated hole 22-2D is a length that allows for a shift due to thermal expansion of the first lower bolt boss portion 20-2D.

Further, a second upper connection L-2U passing through the center of expansion O and the center P-2U of the second upper bolt boss 20-2U.
The second upper bolt boss 20-2U has a focal point FU-2A and a focal point FU on the second upper side connection L-2U.
2B of the elliptical second upper bolt hole 22-2U having a focal length M-2U between the second upper bolt hole 22-2U. The major diameter of the second upper bolt elongated hole 22-2U is a length that allows for the shift due to thermal expansion of the second upper bolt boss portion 20-2U.

A second lower connection L-2 passing through the center of expansion O and the center P-2D of the second lower bolt boss 20-2D.
D, and the second lower bolt boss 20-2D has a focal point FD-2A and a focal point F on the second lower connection L-2D.
An oval second lower bolt slot 22-2D having an inter-focal distance M-2D with respect to D-2B is formed. This second
The major axis of the lower bolt elongated hole 22-2D is a length that allows for a shift due to thermal expansion of the second lower bolt boss portion 20-2.

A fourth upper connection L-4 passing through the center of expansion O and the center P-4U of the fourth upper bolt boss 20-4U.
U, and the fourth upper bolt boss 20-4U has a focus FU-4A and a focus F on the fourth upper connection L-4U.
An elliptical fourth upper bolt slot 22-4U having a focal length M-4U with U-4B is formed. This fourth
The major diameter of the upper bolt elongated hole 22-4U is a length that allows for the displacement due to thermal expansion of the fourth upper bolt boss portion 20-2U.

Further, a fourth lower connection L-4 passing through the expansion center O and the center P-4D of the fourth lower bolt boss portion 20-4D.
D, and the fourth lower bolt boss 20-4D has a focal point FD-4A and a focal point F on the fourth lower connection L-4D.
An elliptical fourth lower bolt elongated hole 22-4D having a focal length M-4D with respect to D-4B is formed. This fourth
The major axis of the lower bolt elongated hole 22-4D is a length that allows for the displacement due to thermal expansion of the fourth lower bolt boss portion 20-4D.

The expansion center O and the upper end bolt boss 2
The upper end connection line LE passing through the center PE of 0-E is drawn, and the upper end bolt boss portion 20-E has a focal point FU-EA and a focal point FU-EB on the upper end connection line LE. And an oval end upper bolt slot 22-E having an inter-focal distance ME between them. The major axis of the end upper bolt slot 22-E is a length that allows for the shift due to thermal expansion of the end upper bolt boss portion 20-E.

According to the configuration of the third embodiment, an even number of port holes 6 are formed in the manifold mounting flange 8.
Even if the expansion center O is arranged between the port holes 6 on the center side,
Since the long bolt holes 22 are not uniformly formed to relieve thermal stress, unnecessary removal of the manifold mounting flange 8 is not performed, and the exhaust manifold 4 is not required.
Of the bolt boss 20
Of the exhaust manifold 4 and the sealing performance of the exhaust manifold 4 are not reduced, the type of the exhaust manifold 4 is not required to be changed, and costs and man-hours can be reduced.

FIG. 10 shows a fourth embodiment of the present invention.

The features of the fourth embodiment are as follows. That is, the bolt long hole 22 was formed in an arc shape in the direction of deviation of thermal expansion.

According to the configuration of the fourth embodiment, even if the bolt boss portion 20 is not linear but thermally expanded so as to expand around the expansion center O, it can be dealt with even if it is shifted.
Elongation due to heat can be effectively released.

FIG. 11 shows a fifth embodiment of the present invention.

The features of the fifth embodiment are as follows. That is, in the bolt long hole 22, the radius R1 about the front focal point FA and the radius R2 about the rear focal point FB in the direction in which the bolt boss portion 20 is thermally expanded and shifted. Formed slightly larger than At this time, the radius R1 is set slightly larger than the radius of the mounting bolt 24, and the radius R2 is set slightly smaller than the radius of the mounting bolt 24.

According to the structure of the fifth embodiment, when the bolt boss portion 20 is thermally expanded and shifted (shown by a broken line), the radius R2 side behind the long bolt hole 22 is fitted to the mounting bolt 24. The contact area between the bolt seating surface of the mounting bolt 24 and the manifold mounting flange 8 increases, and the tightening force is stabilized.
The manifold mounting flange 8 is firmly supported,
The exhaust manifold 4 can be firmly supported.

[0059]

As is apparent from the above detailed description, according to the present invention, a bolt hole through which a mounting bolt for mounting an exhaust manifold is inserted is formed in an elongated bolt hole.
By arranging the long diameter of the bolt long hole on the wire passing through the center of expansion of the exhaust manifold and the center of the long hole of the bolt, unnecessary removal of the manifold mounting flange is not performed, and expansion of the exhaust manifold due to heat is achieved. To reduce the thermal stress applied to the mounting bolts, to prevent the peripheral strength of the bolt boss and the sealing performance of the exhaust manifold from deteriorating, eliminating the need for changing the exhaust manifold type, reducing costs and man-hours. I can do it.

[Brief description of the drawings]

FIG. 1 is a side view of an exhaust manifold illustrating each bolt elongated hole.

FIG. 2 is a plan view of an exhaust manifold.

FIG. 3 is a side view from the port hole side indicated by an arrow III in FIG. 2;

FIG. 4 is a sectional view taken along arrow IV-IV in FIG. 3;

FIG. 5 is a side view of an exhaust manifold attached to a cylinder head.

FIG. 6 is a side view showing a thermal expansion state of the exhaust manifold.

FIG. 7 is a partial side view of an exhaust manifold illustrating each bolt elongated hole in the second embodiment.

FIG. 8 is a side view of an exhaust manifold illustrating each bolt elongated hole in the third embodiment.

FIG. 9 is a plan view of an exhaust manifold according to a third embodiment.

FIG. 10 is a view of a bolt elongated hole in a fourth embodiment.

FIG. 11 is a view of a bolt elongated hole in the fifth embodiment.

FIG. 12 is a side view of an exhaust manifold conventionally mounted on a cylinder head.

[Description of Signs] 2 Cylinder head 4 Exhaust manifold 6 Port hole 8 Manifold mounting flange 10 Exhaust collecting pipe 12 Exhaust branch pipe 20 Bolt boss portion 22 Bolt long hole 24 Mounting bolt

Claims (5)

[Claims] 1. A manifold mounting flange provided with a plurality of port holes corresponding to respective exhaust ports of a cylinder head of a multi-cylinder engine, and joined to the cylinder head, and one end of each of the port holes is provided with each of the port holes. An exhaust branch pipe connected to the manifold mounting flange and connected to an exhaust manifold at each other end is provided correspondingly to the manifold mounting flange, and the manifold mounting flange is provided with a plurality of bolt bosses formed with bolt holes. In the structure of the exhaust manifold attached to the cylinder head by a mounting bolt inserted into the bolt hole, the bolt hole is formed in a long bolt hole, and the major diameter of the long bolt hole is defined by the expansion center of the exhaust manifold and the expansion center of the exhaust manifold. Exhaust manifold structure characterized by being arranged on a wire passing through the center of the bolt boss Build. 2. A multi-cylinder engine having a plurality of port holes corresponding to respective exhaust ports of a cylinder head, a manifold mounting flange which is joined to the cylinder head, and one end of each of which is provided with the respective port holes. An exhaust branch pipe connected to the manifold mounting flange and connected to an exhaust manifold at each other end is provided correspondingly to the manifold mounting flange, and the manifold mounting flange is provided with a plurality of bolt bosses formed with bolt holes. In the structure of an exhaust manifold attached to the cylinder head by a mounting bolt inserted into the bolt hole, the bolt hole is formed as a long bolt hole, and the major axis of the long bolt hole is oriented in the direction of thermal deviation of the bolt boss. The structure of the exhaust manifold, which is arranged in conformity with the above. 3. The exhaust manifold structure according to claim 1, wherein a major axis of the elongated bolt hole is formed to be larger as the distance from the expansion center of the exhaust manifold increases. 4. The exhaust manifold, wherein an odd-numbered port hole is formed in the manifold mounting flange, and the expansion center of the exhaust manifold is arranged in a central port hole. The structure of the exhaust manifold described in 1. 5. The exhaust manifold, wherein an even-numbered port hole is formed in the manifold mounting flange, and the expansion center of the exhaust manifold is disposed at a substantially central portion of the manifold mounting flange. Item 2. The structure of the exhaust manifold according to item 1.