JP3455930B2 - Steel pipe exhaust manifold for multi-cylinder engine - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates are those which relate to structure of an exhaust manifold of a multi-cylinder engine using steel pipes.

[0002]

2. Description of the Related Art Generally, an exhaust manifold of a multi-cylinder engine in which an exhaust pipe for each cylinder is integrally formed is often made of cast iron from the viewpoint of heat resistance, but a cast iron type is considerably heavy. , Impairs the weight reduction of the engine itself.
Also, the fluid resistance on the inner surface is large.

Therefore, as disclosed in Japanese Utility Model Laid-Open No. 5-1819, for example, the exhaust pipe for each cylinder is formed of a steel pipe, that is, a steel pipe material such as stainless steel does not cause exhaust interference. It has been proposed that the exhaust manifold including the above exhaust pipes is formed by bending into a hollow shape to reduce the weight and the fluid resistance. In this way, when each exhaust pipe of the exhaust manifold is made of steel pipe, the structure of the exhaust downstream side collecting part is generally such that the exhaust downstream side end part of each steel pipe exhaust pipe is converged integrally and this collecting part Will be joined to one collecting pipe in a fitted state.

An example of the structure of a steel pipe exhaust manifold in the conventional multi-cylinder engine is shown in FIGS.

In this example, as a multi-cylinder engine, for example, an in-line 4-cylinder engine (not shown) is adopted, and correspondingly, a non-interference type exhaust manifold 1 having a structure as shown in FIG. 5 is provided. ing.

The exhaust manifold 1 has first to fourth exhaust pipes 11 to 14 corresponding to the first to fourth cylinders No1 to No4 of the in-line four-cylinder engine, and the exhaust pipes 11 to 14 are provided. Flange portions 2 for joining to the exhaust port portion on the engine body side are integrally formed on the exhaust upstream side end portions 11a to 14a, while the exhaust downstream side end portion 11b to
14b is converged and integrated as shown in FIGS. Each of the exhaust downstream side end portions 11b to 14b of the exhaust pipes 11 to 14 in the converging portion 3 has a substantially fan-shaped cross section as shown in FIG. 6, and the corner portions in the XY axial directions intersect with each other. The two pieces are fitted together so as to form a substantially circular cross section as a whole, and are welded to each other to be joined and integrated. Then, a bracket 4 for connecting with one downstream collecting pipe is fitted to the integrated cylindrical converging portion 3.

Then, the welded portions of the converged exhaust pipe downstream end portions 11b to 14b are arranged in parallel on the left and right sides of the first exhaust pipe 11 and the first exhaust pipe 11 having a long pipe length, as is apparent from FIG. 4 are arranged in parallel to the lower walls of the four exhaust pipes 14 and to the lower left and right, and are arranged vertically to the left and above the joining line LX with the upper wall portions of the second exhaust pipe 12 and the third exhaust pipe 13 having short pipe lengths. The first exhaust pipe 11 and the second exhaust pipe 12 having a large pipe length difference are vertically arranged in parallel with each other on the vertical wall portions of the fourth exhaust pipe 14 and the third exhaust pipe 13 having a large pipe length difference. Each of the joining lines L and the joining line LY with each vertical wall
The LY side of X and LY is welded first, and then the LX side is welded, and as a result, the weld beads BX and BY of LX and LY of the formed joining lines are joined.
Has a structure in which the welding bead BY on the joining line LY side is located on the exhaust upstream side of the welding bead BX on the joining line LX side and crosses at the center O point of the focusing portion 3.

[0008]

However, in the case of a steel pipe exhaust manifold for a multi-cylinder engine as shown in FIG. 5, as described above, the exhaust pipes 11 to 11 up to the converging portion 3 are related to the cylinder position. 14 length and bending state are different,
Correspondingly, the amount of thermal expansion in each axial direction during engine operation also differs considerably.

As a result, the first and fourth exhaust pipes 11 and 14 located on the upper left and right sides and having a long pipe length have the thermal expansion amounts located on the lower left and right sides, and the second and third exhaust pipes having a short pipe length. The weld bead BY of the first and fourth exhaust pipes 11 and 14 is also restrained by the weld bead BX at the central O point, which is considerably larger than the thermal elongation of 12 and 13. Therefore, cracks due to stress strain are generated especially in the weld bead BY at the point P ₁ which is the boundary point between the extension deformation side and the restraint.
There is a problem that (folding on the front side of the drawing) occurs. As a result, the sealing property is impaired.

The present invention aims to solve such a problem.

[0011]

Steel pipe exhaust manifold of a multi-cylinder engine SUMMARY OF THE INVENTION The present invention, in order to achieve the above object, is constituted respectively provided with an effective means for solving the problems as follows.

That is, first, in the steel pipe-made exhaust manifold of the multi-cylinder engine of the present invention, at least three steel pipe-made exhaust pipes having different amounts of thermal expansion in the axial direction are made to converge with each other at the exhaust downstream side end portion. Is a steel pipe exhaust manifold of a multi-cylinder engine that is integrated by welding between mutually adjacent pipe wall portions of the exhaust pipe of the section, the difference in the amount of thermal expansion in the axial direction at the center of the focusing portion is The weld bead between the pipe walls of the large exhaust pipes is formed by being superposed on the exhaust upstream side of the weld bead between the pipe walls of the exhaust pipes with a small difference in the amount of thermal expansion in the axial direction. There is.

Further, in that case, the welding direction of the exhaust bead on the downstream side of the exhaust gas at the weld bead overlapping portion at the center of the converging portion is from the side between the pipe wall portions of the exhaust pipes having a large thermal expansion in the axial direction to the axial direction. It is formed by welding in a direction between pipe wall portions of exhaust pipes having a small amount of thermal expansion, or in the opposite direction.

Further, in the steel pipe exhaust manifold of the multi-cylinder engine of the present invention, the first and fourth exhaust pipes have the pipe lengths longer than the pipe lengths of the second and third exhaust pipes. Steel pipe exhaust of in-line 4-cylinder engine in which four exhaust pipes are bundled together at the exhaust downstream side end and the exhaust pipes of the converging part are integrated by welding between mutually adjacent pipe wall portions In the manifold, the weld bead between the pipe walls of the first exhaust pipe and the fourth exhaust pipe and the second exhaust pipe and the third exhaust pipe at the center of the focusing portion has the first exhaust pipe. The pipe and the second exhaust pipe and the fourth exhaust pipe and the third exhaust pipe are formed by being superposed on the exhaust upstream side of the weld bead between the pipe wall portions.

[0015]

[0016]

[0017]

[Action] steel pipe exhaust Maniho <br/> Lumpur de multi-cylinder engine of the present invention exhibits an effect as each next in correspondence with the configuration.

That is, first, in the structure of the steel pipe exhaust manifold of the multi-cylinder engine of the present invention, as described above,
By concentrating at least three steel pipe exhaust pipes having different amounts of thermal expansion in the axial direction at the exhaust downstream end, and by welding the mutually adjacent pipe wall portions of the exhaust pipes of the converging portion. In a steel pipe exhaust manifold of a multi-cylinder engine integrated, the welding bead between the pipe wall portions of the exhaust pipes having a large difference in the amount of thermal expansion in the axial direction at the center of the converging portion has a thermal expansion in the axial direction. Exhaust pipes that have a small difference in the amount of heat and are formed so as to be in a superposed state on the exhaust upstream side of the weld bead between the pipe walls of the exhaust pipes, and that have a small difference in the amount of thermal expansion in the axial direction. The restraining force of the weld bead between the pipe wall portions is reduced, and the stress due to the difference in the thermal elongation amount can be absorbed by the bending of the weld bead, and the crack suppressing action is realized.

Further, in this case, the welding direction of the exhaust downstream side welding bead in the weld bead overlapping portion in the center of the converging portion is such that the axial direction from the pipe wall portion side of the exhaust pipes is large in the axial direction. When the exhaust pipes having a small amount of thermal expansion toward the pipe wall portions are welded in the direction between the pipe wall portions or in the opposite direction, the action is more effectively realized.

Further, in the steel pipe exhaust manifold of the multi-cylinder engine of the present invention, the first and fourth exhaust pipes have the pipe lengths longer than the pipe lengths of the second and third exhaust pipes. Steel pipe exhaust of in-line 4-cylinder engine in which four exhaust pipes are bundled together at the exhaust downstream side end and the exhaust pipes of the converging part are integrated by welding between mutually adjacent pipe wall portions In the manifold, the weld bead between the pipe walls of the first exhaust pipe and the fourth exhaust pipe and the second exhaust pipe and the third exhaust pipe at the center of the focusing portion has the first exhaust pipe. The in-line four-cylinder is formed by being overlapped and formed on the exhaust upstream side of the weld bead between the pipe wall portions of the pipe and the second exhaust pipe and the fourth exhaust pipe and the third exhaust pipe. In the case of an engine steel pipe exhaust manifold, Ku can achieve similar effects.

[0021]

[0022]

[0023]

[Effect of the Invention] As a result, according to the steel pipe exhaust manifold of the multi-cylinder engine of the present invention, to absorb the stress between the difference in thermal expansion amount in the axial direction is large exhaust pipe by bending deformation of the weld bead As a result, cracks due to strain stress as in the conventional case can be prevented. Therefore, the sealing property is not lost. As a result, durability is improved.

[0024]

EXAMPLES 1 to 3 show the structure of steel pipe exhaust manifold of a multicylinder engine according to an embodiment of the present invention.

In this embodiment, as the multi-cylinder engine, for example, an in-line four-cylinder engine similar to that of the conventional example is adopted, and correspondingly, for example, the exhaust manifold 1 having the same structure as the conventional one shown in FIG. It is provided.

The exhaust manifold 1 has first to fourth exhaust pipes 11 to 14 corresponding to the first to fourth cylinders of the in-line four-cylinder engine, and the exhaust pipes 11 to 14 are provided.
The exhaust upstream side ends (engine body side end portions) 11a to 14a are integrally formed with a flange portion 2 for joining to an engine body side exhaust port portion, while the other is exhaust downstream side end portions. 11b to 14b are converged and integrated as shown in FIG. Each of the exhaust downstream side end portions 11b to 14b of the exhaust pipes 11 to 14 in the converging portion 3 has a substantially fan-shaped cross section, and has a substantially circular cross section as a whole with corner surfaces having two flat joint walls in the vertical and horizontal directions. As they are formed, they are fitted together and integrated.

The fitting is performed by the first (No1) and fourth (No4) cylinders on both ends of the in-line four-cylinder engine, which have long pipe lengths and large thermal expansion amounts. , 14b on the left and right on the upper side, and on the middle side of the same in-line 4-cylinder engine
(No2), the third (No3) cylinder has a short pipe length and a small amount of thermal expansion. The second and third exhaust pipe downstream end portions 12b, 13b are arranged side by side on the lower left and right sides, respectively. As a result, the two welding joint lines LX and LY in the XY directions which are orthogonal to each other between the first to fourth exhaust pipes 11 to 14 formed in a cross shape by the fitting are formed in the X-axis direction. The first joining line LX is a second joining line having a large difference in thermal expansion amount, and the joining line LY in the Y-axis direction is a joining line having a small difference in thermal expansion amount.

Then, the exhaust pipes 11 to 1 each of which is focused as described above.
The two first and second joining lines LX and LY in the XY direction of the downstream end portions 11b to 14b of No. 4 are welded in the following relationship as shown in FIG.

That is, first, welding is performed along the first joining line LX in the X-axis direction in the arrow (a) direction (from the left side to the right side). As a result, a weld bead as indicated by reference numeral BX in FIG. 1 is formed, and as a result, the downstream side end portion 11b of the first exhaust pipe 11 and the second exhaust pipe 11 having a large difference in the amount of thermal expansion located between the upper and lower sides. 12 and the downstream end 14b of the fourth exhaust pipe 14 and the third exhaust pipe 1
The welding and joining with the downstream end portion 13b of 3 is realized first.

Next, welding is carried out along the second joining line LY in the Y-axis direction in the arrow (B) direction (from the upper side to the lower side). As a result, the first weld bead BX shown in FIG. 1 to FIG. 3 and the second weld bead that is cross-polymerized in a mountain shape at the center O point of the focusing portion 3 are formed. Located at the lower end of the first exhaust pipe 11 having a small difference in thermal expansion amount, the downstream end 14b of the fourth exhaust pipe 14 and the downstream end 1 of the second exhaust pipe 12.
2b and the downstream end portion 13b of the third exhaust pipe 13 are reliably welded and joined together.

[0031] As a result, the P ₁ where difference in thermal extension amount is large, cracks due to strain stress at the time of thermal expansion is likely to occur
The point is firmly fixed by the joining force of the first and second weld beads BX and BY, while the strain due to the thermal elongation stress is located on the downstream side of the exhaust gas and the restraining force is reduced. Since it is absorbed by the bending deformation of the second weld bead BY, the conventional crack is unlikely to occur at the point P ₁ .

In the above embodiment, the first joining line LX in the X-axis direction is in the right arrow (a) direction from the left, and the second joining line LY in the Y-axis direction is from the top to the bottom arrow. (B)
We adopted the welding method of welding in each direction, but the two welding directions are right to left (direction C in the figure) and from bottom to top (direction D in the figure) opposite to the above. Not to mention good things.

In the above embodiments, the case of the exhaust manifold of the in-line 4-cylinder engine has been described as an example.
For example, in the case of an exhaust manifold having three exhaust pipes 11 to 13 in each of the left and right banks, such as a V-type 6-cylinder engine, if the configuration shown in FIG.

That is, in this case, for example, the first, third, fifth cylinder or the first, second, fifth, and sixth cylinders corresponding to the first, second, fifth, and sixth cylinders of the second, fourth, and sixth cylinders, for example. , Second, fifth,
The sixth exhaust pipes 11, 12, 15, 16 have a long pipe length and a large thermal expansion amount, while the third and fourth exhaust pipes 13, 14 corresponding to the third and fourth cylinders between them have the same pipe length. Is short and thermal expansion is small. And each of these exhaust pipes 11, 12,
13, 14, 15, 16 downstream end portions 11b, 12b, 1
If the fitting state of the focusing portions 3 of 3b, 14b, 15b and 16b is as shown in the drawing (the exhaust pipe focusing portions on both the left and right banks are also shown in the figure), Similar to the case of the embodiment, the first, second, fifth, and sixth exhaust pipe downstream-side end portions 11b, 12b, 15b, 16b having large differences in thermal expansion amount.
First, the V-shaped joining line LA between the third and fourth exhaust pipe downstream end portions 13b, 14b is welded in the arrow (e) direction (or the opposite direction) to join. As a result, illustrated BA
A continuous welding bead is formed in a V shape.

After that, the first and second exhaust pipe downstream end portions 11b and 12b and the fifth and sixth exhaust pipes having a small difference in the amount of thermal expansion are subsequently.
A straight joining line LB with the exhaust pipe downstream side end portions 15b, 16b is welded and joined in the arrow (f) direction (or the opposite direction).

As a result, a second weld bead is formed such that the lower end side thereof as shown in BB overlaps with the apex P ₂ of the first V-shaped weld bead BA.

Therefore, also with this configuration, the second welding bead BB, which has a large difference in thermal expansion amount and is susceptible to cracks due to strain stress, is located on the downstream side of the exhaust gas, and the binding force is lowered to bend. Since it becomes easier, the occurrence of cracks at the point P ₂ is prevented.

[Brief description of drawings]

FIG. 1 is an enlarged front view showing a structure after joining of a steel pipe exhaust manifold converging portion of a multi-cylinder engine according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

3 is a sectional view taken along line BB of FIG.

FIG. 4 is an enlarged front view showing the structure of the multi-cylinder engine according to another embodiment of the present invention after joining the steel pipe exhaust manifold converging portion.

FIG. 5 is a front view showing an overall structure of an exhaust manifold of a multi-cylinder engine common to a conventional example and an embodiment of the present invention.

FIG. 6 is an enlarged front view of the exhaust manifold of FIG. 5 in a state before joining the exhaust downstream side focusing portion.

FIG. 7 is an enlarged front view of the state after joining the steel pipe exhaust manifold converging portion of the conventional multi-cylinder engine.

[Explanation of symbols]

1 is an exhaust manifold, 3 is a focusing part, 11 is a first exhaust pipe, 12 is a second exhaust pipe, 13 is a third exhaust pipe, 14 is a fourth exhaust pipe, and LX and LA are first joints. Line, LY,
LB is the second joining line, BX and BY are the first weld beads, and BY and BB are the second weld beads.

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) F01N 7/10 B23K 9/00 501 B23K 9/028 F01N 7/18

Claims (3)

(57) [Claims] 1. At least three steel pipe-made exhaust pipes having different amounts of thermal expansion in the axial direction are mutually focused at an end portion on the exhaust downstream side, and the exhaust pipes of the converging portion are located between mutually adjacent pipe wall portions. A steel pipe exhaust manifold for a multi-cylinder engine, which is integrated by welding, where the weld bead between the pipe wall portions of the exhaust pipes having a large difference in the amount of thermal expansion in the axial direction at the center of the converging portion is the shaft. An exhaust manifold made of steel pipe for a multi-cylinder engine, wherein the exhaust pipe is superposed and formed on the exhaust upstream side of a weld bead between the pipe wall portions of the exhaust pipe with a small difference in the amount of thermal expansion in the direction. 2. The welding direction of the exhaust bead on the downstream side of the exhaust gas in the weld bead overlapping portion at the center of the focusing portion is such that the amount of thermal expansion in the axial direction is large in the axial direction from the side between pipe wall portions of exhaust pipes. 2. A steel pipe exhaust manifold for a multi-cylinder engine according to claim 1, wherein the exhaust pipes are formed by welding in a direction between pipe walls of small exhaust pipes or in a direction opposite thereto. 3. The pipe lengths of the first and fourth exhaust pipes are second,
The first to fourth four exhaust pipes, which are longer than the pipe length of the third exhaust pipe, are focused on each other at the exhaust downstream end, and the exhaust pipes of the focusing portion are connected to each other between adjacent pipe wall portions. A steel pipe exhaust manifold for an in-line 4-cylinder engine integrated by welding, comprising: the first exhaust pipe, the fourth exhaust pipe, the second exhaust pipe, and the third exhaust gas at the center of the focusing portion. The weld bead between the pipe and the pipe wall is on the exhaust upstream side of the weld bead between the pipe walls of the first exhaust pipe and the second exhaust pipe and the fourth exhaust pipe and the third exhaust pipe. An exhaust manifold made of a steel pipe for a multi-cylinder engine, characterized in that the exhaust manifold is formed at the position of the cylinder.