JPH108954A - Exhaust manifold mounting structure for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform positioning while permitting extension/contraction of an exhaust manifold without using oblong hole. SOLUTION: Eight stud bolts 21 are implanted in a cylinder head side, to be arranged on the same straight line M, N. In flanges 8 to 11 of an exhaust manifold, bolt insertion holes 12 to 19 are formed. Each bolt insertion hole 12 to 19 is formed all in a true circle of equal diameter, to be set to a diameter having a sufficient margin relating to a diameter of the stud bolt 21. An upper part bolt insertion hole 14 of a #2 cylinder is eccentrically formed upward as a first reference hole, an upper part bolt insertion hole 16 of a ξ3 cylinder is eccentrically formed downward as a second reference hole. Since the center of gravity of the exhaust manifold is placed in a rear part, the stud bolt 21 is brought into contact with a lower edge of the first reference hole 14, the stud bolt 21 is brought into contact with an upper edge of the second reference hole 16, the exhaust manifold is positioned in a prescribed position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for mounting an exhaust manifold of an internal combustion engine to a cylinder head.
In particular, the present invention relates to an exhaust manifold mounting structure in which a part of a plurality of bolt insertion holes provided in a flange is used as a reference hole to perform positioning with respect to a cylinder head when mounting the exhaust manifold.

[0002]

2. Description of the Related Art Generally, an exhaust manifold of an internal combustion engine typified by an automobile engine is formed by fitting a bolt insertion hole in a flange portion at a branch end with a stud bolt provided on a side surface of a cylinder head and tightening a nut. Fixed. Here, the exhaust manifold, through which the high-temperature exhaust gas flows, expands and contracts as the engine starts and stops.
There is a problem that the shrinkage is repeated and the shrinkage occurs along the engine front-rear direction (cylinder row direction) with time due to the thermal deformation. Therefore, the bolt insertion hole through which the stud bolt penetrates has a large diameter with a sufficient margin for the diameter of the stud bolt, and is configured to allow expansion and contraction of the exhaust manifold along the longitudinal direction of the engine. In addition, during the above-mentioned nut tightening operation, the operator naturally hooks the bolt insertion hole of the exhaust manifold to the stud bolt so that the exhaust manifold is naturally positioned at a predetermined position so that the exhaust manifold is accurately positioned with respect to the cylinder head. A device for positioning is conventionally used.

A typical example is Japanese Utility Model Laid-Open No. 3-1297.
As disclosed in Japanese Patent Application Laid-Open No. 16-224, Japanese Unexamined Patent Publication No. Hei 4-224224, etc., one of a plurality of bolt insertion holes is formed as a positioning reference hole having a relatively small diameter substantially equal to the bolt diameter, and This is a method in which another bolt insertion hole is formed as an elongated hole along the engine front-rear direction. The width of the elongated hole in the vertical direction is relatively small, which is substantially equal to the diameter of the stud bolt.

In this configuration, since the movement of the exhaust manifold, which attempts to rotate about the positioning reference hole, is restricted by the elongated hole, the exhaust manifold is accurately positioned at the stage before the nut is tightened, and at the same time,
Expansion and contraction in the longitudinal direction of the engine are allowed.

[0005]

However, in the conventional configuration in which the exhaust manifold is positioned by combining the small-diameter reference hole and the long hole as described above, the processing of the long hole is required, so that the processing steps become complicated. This is not preferable in terms of work efficiency and cost.

Further, the branches of a plurality of cylinders are divided into two branch groups, and the branches included in each branch group are gathered together on the upstream side, and both branch groups are gathered together on the downstream side. In the case of the exhaust manifold having the configuration described above, thermal contraction occurs with time in such a manner that the two branch groups approach each other in the inside, but in the above-described conventional configuration, the flange having the reference hole for positioning is not provided. Since it is strongly restrained by the cylinder head, stress is likely to be generated in the forked portion where both branch groups are gathered, and there is a possibility that the durability may be reduced.

[0007]

An exhaust manifold mounting structure for an internal combustion engine according to the present invention has independent cylinder head mounting flanges for each cylinder branch, and two studs above and below each flange. It has a bolt insertion hole having a diameter with a margin for the bolt diameter, and has a first branch group at the front of the engine assembled at the upstream position and a rear branch at the engine also assembled at the upstream position. An upper manifold bolt insertion hole selected from the first branch group in the exhaust manifold of the internal combustion engine, wherein the second branch group is integrated with each other via a forked-shaped gathering portion; One upper bolt insertion hole selected from the second branch group constitutes a pair of reference holes, and a first reference hole is provided for each center of the stud bolt attached to the cylinder head. The center of the second reference hole is eccentric downward and the center of the second reference hole is downward, and a stud is provided at the lower edge of the first reference hole in a non-tightened state by a moment due to the center of gravity located outside the both reference holes. The exhaust manifold is positioned at a predetermined position by abutment of the bolt and a stud bolt at the upper edge of the second reference hole. The bolt insertion holes are characterized in that each center is located at the same height position as the center of the corresponding stud bolt and that a gap is maintained between the inner periphery of each stud bolt and the stud bolt. I have.

[0008] The bolt insertion hole may be formed as follows.
Each can be a perfect circle, and can be set to the same diameter including the reference hole.

In the above configuration, the exhaust manifold tries to rotate in a predetermined direction by the center of gravity located outside the pair of reference holes. At this time, the stud bolt is in contact with the lower edge of the first reference hole and the stud bolt is in contact with the upper edge of the second reference hole due to the rotational moment. In this state, the exhaust manifold is positioned at a predetermined position. Is done. Therefore, the diameters of these reference holes can provide a sufficient margin for the diameter of the stud bolt, similarly to other bolt insertion holes. In this positioning state, the other bolt insertion holes are kept out of contact with the stud bolts, so that the stud bolts are positioned substantially at the center of the bolt insertion holes. Therefore, the expansion and contraction of the exhaust manifold along the engine front-rear direction (cylinder row direction) is allowed, and the assembly portion between the two branch portions is not forced.

The above-mentioned reference holes can be appropriately selected from the first branch group and the second branch group. However, in order to perform predetermined positioning, the center of gravity of the exhaust manifold is located outside the both reference holes. There must be. In claim 3, the bolt insertion hole above the flange located at the rearmost position in the first branch group and the bolt insertion hole above the flange located at the frontmost position in the second branch group. , The reference hole. That is, a pair of reference holes is provided at a position sandwiching the gathering portion between the two branch groups.

According to a fourth aspect of the present invention, a plurality of stud bolts corresponding to the bolt insertion holes at the upper portion of each flange are arranged on the same straight line on the side surface of the cylinder head, and the centers of the pair of reference holes are aligned. It is eccentric upward and downward with respect to this straight line, respectively. The center of the other upper bolt insertion hole is on this straight line. Therefore,
When machining the bolt insertion hole, the center position of the bolt insertion hole to be the reference hole may be decentered, and the machining is extremely simple.

[0012]

As is apparent from the above description, according to the exhaust manifold mounting structure for an internal combustion engine according to the present invention, the exhaust manifold can be positioned via the stud bolt without the need for machining a long hole. And the processing becomes extremely simple. In addition, the bolt insertion hole serving as the reference hole can be set to a diameter with a sufficient margin to the diameter of the stud bolt, and the flange provided with the reference hole has some movement due to expansion and contraction of the exhaust manifold. Is acceptable. Therefore, a large stress does not act on the gathering portion between the two branch groups, and the durability is improved.

According to the second aspect, machining of the bolt insertion hole including the reference hole becomes extremely simple.

According to the third aspect of the present invention, since the reference hole is provided so as to sandwich the central portion of the expansion and contraction of the entire exhaust manifold, the expansion and contraction of the exhaust manifold can be more smoothly absorbed.

According to the fourth aspect, since the center position of the bolt insertion hole serving as the reference hole only needs to be decentered without changing the position of the stud bolt, machining and assembly are further facilitated.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a mounting structure of an exhaust manifold 1 for an in-line four-cylinder internal combustion engine shown in FIG. The exhaust manifold 1 is integrally cast as a whole with cast iron, and has four branches 2 to 2 connected to exhaust ports of the respective cylinders opened to the side of the cylinder head.
5, the branch 2 of the # 1 cylinder and the branch 3 of the # 2 cylinder assemble as a first branch group at an upstream position as shown in FIG.
The cylinder branch 4 and the # 4 cylinder branch 5 assemble with each other at a position on the upstream side as a second branch group. The # 1 branch group located at the front of the engine and the # 2 branch group located at the rear of the engine are integrally connected to each other via a bifurcated collecting portion 6 at the center of the engine. The collecting portion 6 extends long toward the rear of the engine, and an exhaust outlet 7 having a flange 7a is provided at a tip end thereof. At the tip of the branches 2 to 5,
Flanges 8 to 1 for mounting on side of cylinder head
1 are provided. These flanges 8-1
Numeral 1 is formed integrally with each of the branches 2 to 5, is separated and independent for each cylinder, and has a substantially elliptical shape. A bolt insertion hole is provided in each of the flanges 8 to 11 so as to sandwich the exhaust outlet 24 at the tip of the branch 2 to 5 at two places separated by 180 °. For more information,
The # 1 cylinder flange 8 has an upper bolt insertion hole 12 located above the branch 2 and a lower bolt insertion hole 13 located below the branch 2.
Similarly, the # 2 cylinder flange 9 has an upper bolt insertion hole 14 and a lower bolt insertion hole 15, and the # 3 cylinder flange 10 has an upper bolt insertion hole 16 and a lower bolt insertion hole 1.
The upper bolt insertion hole 18 and the lower bolt insertion hole 19 are formed in the flange 11 for the # 4 cylinder. These eight bolt insertion holes 12 to 19
Are all circular and have the same diameter.

A total of eight stud bolts 21 are planted on the side of the cylinder head to which the exhaust manifold 1 is attached, corresponding to the respective bolt insertion holes 12 to 19. Here, the four stud bolts 21 located above the cylinder head and the four stud bolts 21 located below are respectively provided at the same height. That is, as shown in FIG. 1, the upper four stud bolts 21 are arranged side by side on the same straight line M, and the lower four stud bolts 21 are arranged on the same straight line N. Are arranged side by side. The straight line M and the straight line N are, of course, parallel.

The bolt insertion holes 12 to 12 of the flanges 8 to 11
19 is set to a diameter having a sufficient margin with respect to the diameter of the stud bolt 21. For example, JIS standard M10
For each stud bolt 21, each bolt insertion hole 12-1
9 is machined into a hole having a diameter of 16 mm.

FIG. 1 shows the positional relationship between each of the flanges 8 to 11 and the stud bolt 21.
The relationship between each of the bolt insertion holes 12 to 19 and the stud bolt 21 is shown in an enlarged manner.

In this embodiment, of the upper bolt insertion hole 12 for the # 1 cylinder and the upper bolt insertion hole 14 for the # 2 cylinder, the upper bolt insertion hole 14 closer to the collecting portion 6 is a reference hole. Specifically, it is selected as the first reference hole. Also#
Of the three cylinder upper bolt insertion holes 16 and the # 4 cylinder upper bolt insertion holes 18, the upper bolt insertion hole 16 which is also closer to the collecting portion 6 is selected as a reference hole, specifically, a second reference hole. Have been. The upper bolt insertion hole 14 of the # 2 cylinder, which is the first reference hole, is compared with the positions of the upper bolt insertion holes other than the reference hole, that is, the formation positions of the bolt insertion hole 12 of the # 1 cylinder and the upper bolt insertion hole 18 of the # 4 cylinder. The upper bolt insertion hole 16 of the # 3 cylinder, which is the second reference hole, is formed eccentrically downward and open. Specifically, it is eccentric upward and downward by a predetermined amount L1 with respect to the reference height position corresponding to the above-described reference line M on the cylinder head side. The eccentric amount L1 is equal to the difference between the radius of the bolt insertion holes 14 and 16 and the radius of the stud bolt 21. Then, the remaining two upper bolt insertion holes 12,
An opening 18 is formed at a height position corresponding to the reference line M. Also, four lower bolt insertion holes 13, 15, 1
7 and 19 are each formed with an opening at a height position coinciding with the reference line N on the cylinder head side.

In other words, as shown in FIG. 1, the stud bolt 21 contacts the lower edge of the upper bolt insertion hole 14 serving as the first reference hole, and the upper bolt insertion hole 16 serving as the second reference hole. With the stud bolt 21 in contact with the edge, the remaining six bolt insertion holes 12, 13, 15, 1
7, 18, 19 are located at the same height position as the center O1 of the center O2 of the corresponding stud bolt 21,
The gap 23 is left over the entire circumference.
The center of gravity 22 of the entire exhaust manifold 1 is located outside the reference holes 14 and 16 as shown in FIG.
More specifically, the second reference hole is located behind a vertical line passing through the upper bolt insertion hole 16 of the # 3 cylinder, that is, on the # 4 cylinder side.

Therefore, when mounting the exhaust manifold 1,
If the operator fits the bolt insertion holes 12 to 19 of the exhaust manifold 1 to the stud bolts 21 on the side of the cylinder head, the exhaust manifold 1 tries to rotate in the clockwise direction in FIG. As a result, as shown in FIG. 1, the stud bolt 21 is pressed against the lower edge of the upper bolt insertion hole 14 serving as the first reference hole, and the stud bolt 21 is pressed against the upper edge of the upper bolt insertion hole 16 serving as the second reference hole. Are in pressure contact with each other. That is,
The exhaust manifold 1 is automatically positioned at a predetermined position shown in FIG. Then, in this state, each stud bolt 2
The exhaust manifold 1 is fixed by tightening a nut (not shown) on the exhaust manifold 1.

In this positioning state, the center O1 of the upper bolt insertion hole 14 serving as the first reference hole and the center O2 of the stud bolt 21 are at the same position in the engine front-rear direction. Similarly, the center O1 of the upper bolt insertion hole 16 serving as the second reference hole and the center O2 of the stud bolt 21 are located at the same front-back position.

In the upper bolt insertion hole 12 and the lower bolt insertion hole 13 of the # 1 cylinder and in the lower bolt insertion hole 15 of the # 2 cylinder, the center O1 of the bolt insertion holes 12, 13, 15 is shown in FIG. As shown, the center O2 of the stud bolt 21 is slightly eccentric to the front of the engine. Also#
The center O1 of the lower bolt insertion hole 17 of the three cylinders and the center O1 of the upper bolt insertion hole 18 and the lower bolt insertion hole 19 of the # 4 cylinder are slightly eccentric toward the rear of the engine with respect to the center O2 of the stud bolt 21. This takes into account the thermal contraction of the exhaust manifold 1 over time. That is, in the exhaust manifold 1 including the two branch groups as described above, each of the front and rear branch groups contracts with time toward the central gathering portion 6 as shown by an arrow A in FIG.
Therefore, in consideration of this, the center O1 of the bolt insertion hole is previously eccentric in the engine front-rear direction by a predetermined amount L2. The eccentricity L2 is, for example, 1 mm.

As described above, in the configuration of the above embodiment,
The exhaust manifold 1 can be accurately positioned at a predetermined position by using the pair of reference holes 14 and 16. Here, each of the reference holes 14 and 16 is a bolt insertion hole 12 other than the reference hole.
13, 15, 17, 18, and 19 may be the same true circular holes, and a sufficient margin can be given to the diameter of the stud bolt 21. Therefore, drilling becomes extremely easy as compared with a conventional drill that involves slotting. Also, reference hole 1
Since the diameters of the stud bolts 21 and 4 also have a sufficient margin, all of the flanges 8 to 11 can move with the expansion and contraction of the exhaust manifold 1, so that stress concentration in the collecting portion 6 is avoided. Is done.

When the flanges 8 to 11 are displaced, the exhaust inlet 24 at the tip of each of the branches 2 to 5 is made to be smaller than the exhaust port opening so that the cross sectional area of the exhaust port is not reduced. It is formed one size larger.

Next, FIG. 3 shows a different embodiment of the exhaust manifold 1 to which the mounting structure of the present invention is applied.
The exhaust manifold 1 is also for an in-line four-cylinder internal combustion engine, and two branch groups are constituted by two front and rear cylinders, and these branch groups are connected in the collecting part 6. Further, a catalytic converter 25 is integrally provided on the downstream side of the collecting section 6, and the catalytic converter 25 is provided in a state inclined backward. Thus, the center of gravity of the exhaust manifold 1 as a whole is located behind the reference holes 14 and 16.

The exhaust manifold 1 also undergoes thermal contraction toward the central gathering portion 6 over time, as indicated by the arrow A, as described above.

The embodiment in which the present invention is applied to the exhaust manifold 1 for an in-line four-cylinder internal combustion engine has been described. However, the exhaust manifold to which the present invention is applied is limited to the one for the in-line four-cylinder internal combustion engine. Not in-line five-cylinder,
The present invention can be applied to exhaust manifolds of various internal combustion engines such as an in-line six-cylinder engine and a V-type eight-cylinder engine.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of an exhaust manifold mounting structure of the present invention.

FIG. 2 is a front view showing one embodiment of an exhaust manifold.

FIG. 3 is a front view showing a different embodiment of the exhaust manifold.

[Explanation of symbols]

 8-11 Flange 12-19 Bolt insertion hole 14 First reference hole 16 Second reference hole 21 Stud bolt

Claims (4)

[Claims] An independent cylinder head mounting flange is provided for each branch of each cylinder.
The first branch group at the front of the engine, which has a bolt insertion hole with a diameter larger than the diameter of the stud bolt at the upstream position, and also gathers at the upstream position. And a second branch group at the rear of the engine is integrated with each other via a forked-shaped gathering portion, and the upper bolt selected from the first branch group in the exhaust manifold of the internal combustion engine. The insertion hole and one upper bolt insertion hole selected from the second branch group constitute a pair of reference holes, and a first reference hole is provided for each center of the stud bolt attached to the cylinder head. The center of the hole is eccentric upward and the center of the second reference hole is eccentric downward, and the moment of the center of gravity located outside both reference holes causes the lower edge of the first reference hole to be in the non-tightened state. S The exhaust manifold is positioned at a predetermined position by the stud bolt contacting the upper edge of the second reference hole and the upper edge of the second reference hole. The center of each bolt insertion hole is located at the same height position as the center of the corresponding stud bolt, and is configured so as to maintain a gap between the inner periphery of each stud bolt and the stud bolt. Exhaust manifold mounting structure for an internal combustion engine. 2. The exhaust manifold mounting structure for an internal combustion engine according to claim 1, wherein each of said bolt insertion holes is a perfect circle and has the same diameter including a reference hole. 3. A bolt insertion hole above a flange located at the rearmost position in the first branch group and a bolt insertion hole above a flange located at the foremost position in the second branch group, 3. The exhaust manifold mounting structure for an internal combustion engine according to claim 1, wherein the reference hole is selected as a reference hole. 4. A plurality of stud bolts corresponding to the bolt insertion holes at the top of each flange are arranged on the same straight line on the side of the cylinder head, and the center of the pair of reference holes is located above the straight line. The exhaust manifold mounting structure for an internal combustion engine according to any one of claims 1 to 3, wherein the center of the other upper bolt insertion hole is eccentric downward and downward, and the center of the other upper bolt insertion hole is on this straight line.