JP2003269158A - Exhaust manifold for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent degradation in durability due to thermal expansion by minimizing thermal capacity with a collecting part of four passages positioned on the upstream side. <P>SOLUTION: An exhaust manifold of an in-line four-cylinder engine consists of an upstream manifold 1 and a downstream manifold. The downstream manifold comprises a pair of downstream exhaust pipes of semicircular cross section. The upstream manifold 1 comprises a pair of end exhaust pipes 11, 12 which are formed out of metallic pipes for the #1, #4 cylinders, and a center exhaust pipe 13 of sheet metal for the #2, #3 cylinders. An outlet part 18 of the center exhaust pipe 13 is formed into a semicircle and connected to the other downstream exhaust pipe. The downstream ends 11a, 12a of the end exhaust pipes 11, 12 are formed into a quadrant shape and connected to the other downstream exhaust pipe with a half form in the mass. Thus, the conventional restriction of curvature with a branch part of #2, #3 cylinders made of pipe can be avoided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 4-cylinder internal combustion engine such as an in-line 4-cylinder internal combustion engine or a V-type 8-cylinder internal combustion engine.
TECHNICAL FIELD The present invention relates to improvement of an exhaust manifold used for a cylinder head having two cylinders.

[0002]

2. Description of the Related Art Exhaust gas from an in-line four-cylinder internal combustion engine is preferably combined in a so-called 4-2-1 format in order to avoid exhaust interference. Therefore, the downstream side portion of the exhaust manifold is provided in one exhaust pipe. Is divided into two flow paths by a partition having a Z-shaped cross section or an S-shaped cross section, and the branch portion of the upstream side portion is composed of four independent metal pipes, and the downstream end portion of this metal pipe is formed. In many cases, a configuration in which two of these are connected to each flow path of the exhaust pipe is adopted. The exhaust pipe provided with the partition wall may be configured as a so-called front tube integral with the catalytic converter.

Further, in Japanese Unexamined Patent Publication No. 2001-65340, four branch parts are constituted by an outer cylinder member made of a sheet metal, which is formed by joining two press-formed metal plates in a so-called centering manner. Further, inside thereof, the same sheet metal inner cylinder member corresponding to only the # 2 cylinder and the # 3 cylinder is provided, and the exhaust of the # 1 and # 4 cylinders flowing outside the inner cylinder member and the inner side of the inner cylinder member are provided. An exhaust device is disclosed in which the flowing exhaust gases of the # 2 and # 3 cylinders are separately guided to the inside of the front tube on the downstream side.

[0004]

In order to comply with severe exhaust emission regulations in recent years, it is necessary to activate the catalyst of the catalytic converter located downstream of the exhaust manifold at an early stage when the internal combustion engine starts cold. Therefore, there is a tendency to reduce the heat capacity of the exhaust manifold and, at the same time, to shorten the pipe length of the exhaust manifold as much as possible. Therefore, 4-
In the configuration of assembling with 2-1 in order to reduce the heat capacity and shorten the pipe length, it is preferable to arrange the position of the gathering portion where the four branch portions gather in the two flow paths on the upstream side as much as possible. It will be preferable.

However, in the exhaust manifold in which each of the four branch portions on the upstream side is made of a metal pipe as in the conventional case, the position of the collecting portion is restricted by the limit of bending work of each metal pipe. . In particular, since the passage length from each exhaust port to the collecting portion needs to be substantially equal in each cylinder, the branch portions of the # 2 and # 3 cylinders near the center of the cylinder row have the # 1 and # 4 cylinders on both sides. Compared with the branch part of No. 2, the bending of the branch parts of the # 2 and # 3 cylinders is practically limited by the bending of the branch parts of the # 2 and # 3 cylinders. You will be restricted.

Further, when the inside of one exhaust pipe is divided into two flow passages by a partition having a Z-shaped section or an S-shaped section as in the conventional downstream portion, this partition locally becomes hot. Therefore, a high thermal stress is generated between the exhaust pipe on the outer periphery and the partition wall, so that it is necessary to use a material having sufficient high temperature strength.

Further, as in the above publication, in the structure in which the entire exhaust manifold is made of sheet metal, the whole including the four flow passages becomes one large metal member, so that the stress due to the thermal expansion and thermal contraction is large. However, there is a problem in that sufficient durability cannot be ensured. Moreover, with this one, # 1,
Since the exhaust of the # 4 cylinder and the exhaust of the # 2 and # 3 cylinders are separated from each other, the outer cylinder member and the inner cylinder member have a double structure, so that there is a problem that the weight increases and welding spatter remains inside. In order not to do so, there is a problem that a high-cost spatterless method such as TIG welding has to be adopted.

[0008]

According to a first aspect of the present invention, there is provided a first head portion on the cylinder head side and a second flange portion on the downstream end side, which are arranged in series. Four
Of the internal combustion engine that guides the exhaust gas of the four cylinders to the position of the second flange portion while separating the exhaust gas of the first cylinder and the fourth cylinder and the exhaust gas of the second cylinder and the third cylinder. The exhaust manifold includes an upstream manifold including the first flange portion and a downstream manifold including the second flange portion.

The downstream manifold is composed of two adjacent flow passages.

Further, the upstream side manifold is formed of independent metal pipes so as to respectively configure the flow paths of the first cylinder and the fourth cylinder, and the downstream end of the flow path of the downstream side manifold. A pair of end exhaust pipes that are collectively connected to one side, and metal plates that are halved so as to form a flow path of the second cylinder and a flow path of the third cylinder are welded to each other. A downstream outlet portion that is configured and has both flow paths joined in a Y shape is configured by a central exhaust pipe that is connected to the other flow path of the downstream side manifold.

That is, among the four upstream flow paths, the flow paths of the two cylinders located in front of and behind the cylinder row are made of metal pipes, and are located in the center of the cylinder row.
The flow paths of the two cylinders are made of sheet metal. Therefore, the flow paths of the two cylinders located in the center of the cylinder row are not restricted by the bending process as in the case where the flow paths of the two cylinders are made of metal pipes, and they can be assembled relatively upstream. As a result, the upstream manifold can be downsized and the heat capacity can be reduced. Further, since the sheet metal portion is only the portion of two cylinders, the problem of stress concentration due to thermal expansion is significantly reduced compared to the case where all the cylinders are made of sheet metal. It should be noted that the flow paths of the two cylinders formed of the end exhaust pipes are joined to each other by being connected to one flow path of the downstream side manifold.

In the invention of claim 2, the end exhaust pipe is
Each is bent inward so as to be gathered near the center of the cylinder row, and its downstream end is opened adjacent to above or below the outlet of the central exhaust pipe, and the central exhaust pipe is The flow passage of the second cylinder and the flow passage of the third cylinder join at a position closer to the first flange portion than the downstream end of the end exhaust pipe. That is, in the portion near the cylinder head, the central exhaust pipe made of sheet metal is located inside the pair of end exhaust pipes made of metal pipes, and at the downstream end side, both are vertically stacked. However, by merging the two flow paths of the Y-shaped central exhaust pipe at a position closer to the cylinder head, the bifurcated portion does not vertically overlap with the end exhaust pipe but is arranged inside thereof. It becomes possible to do. As a result, the entire size is reduced. In addition,
It is desirable that the four passages have substantially the same passage length as the inner passage.

Further, more specifically, as in claim 3, the openings at the downstream ends of the pair of end exhaust pipes each have a quadrant shape, and the outlet of the central exhaust pipe is a semicircle. The upstream end of the upstream manifold constituted by these has an outer shape that is generally circular.
As a result, the two flow paths of the downstream side manifold are each formed in a semicircular shape so as to have a circular cross section as a whole,
A pair of end exhaust pipes can be connected to one of them, and a central exhaust pipe can be connected to the other.

Preferably, the two flow paths of the downstream side manifold are each constituted by a downstream side exhaust pipe made of a metal pipe and having a semicircular cross section.
Further, a pair of downstream side exhaust pipes are arranged adjacent to each other so as to form a circular cross section as a whole.

More preferably, as in claim 5, the pair of downstream exhaust pipes of the downstream manifold are separated and independent from each other except the second flange portion.

A pair of end exhaust pipes is connected to one of the pair of downstream exhaust pipes, and a central exhaust pipe is connected to the other. Therefore, over the entire length from the first flange portion to the second flange portion, both can be individually displaced without being constrained to each other. Therefore, generation of local stress due to thermal expansion is suppressed.

More preferably, a gap is provided between the adjacent wall portions of the pair of downstream side exhaust pipes. As a result, the wall portions of the respective downstream side exhaust pipes adjacent to each other are also cooled, and uneven temperature in the circumferential direction does not occur.

Further, in the invention of claim 7, in the connecting portion between the upstream side manifold and the downstream side manifold, the downstream ends of the pair of end exhaust pipes are the inner circumference of one of the downstream side exhaust pipes of the downstream side manifold. Side, the outlet of the central exhaust pipe is fitted to the outer peripheral side of the other downstream exhaust pipe of the downstream manifold, and is welded at different positions in the axial direction of the pipe. In other words, the fitting relationship of the downstream manifold to the pair of downstream exhaust pipes is different,
Moreover, the respective welding positions do not overlap each other in the axial direction. As a result, the welded part does not bulge significantly in the radial direction, and the connecting part between the upstream side manifold and the downstream side manifold is downsized.

[0019]

According to the exhaust manifold of the internal combustion engine of the present invention, the four flow passages are not limited to the conventional bending process of the metal pipe forming the branch portion of the cylinder near the center of the cylinder row. Can be combined into two flow paths at a relatively upstream position, the path length to the downstream catalytic converter can be shortened, and the heat capacity of the entire exhaust manifold can be reduced. At the same time, the stress generated by repeated thermal expansion and thermal contraction can be reduced, and sufficient durability can be secured.

In particular, when a pair of downstream exhaust pipes each made of a metal pipe are made independent from each other as the downstream manifolds, the stress due to thermal expansion can be further alleviated, and the damage can be caused. Can be reliably prevented.

Further, by providing the gap as in claim 6, it is possible to avoid locally increasing the temperature of the adjacent wall portions of the pair of downstream side exhaust pipes, and to prevent their deterioration and strength reduction.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the entire exhaust manifold for an in-line four-cylinder internal combustion engine according to the present invention. This exhaust manifold includes an upstream manifold 1 and a downstream manifold 2
Is roughly divided into The upstream side manifold 1 is for gathering four flow paths into substantially two flow paths as described later, and the downstream side manifold 2 is like a single pipe in appearance. It has two channels while maintaining its shape.
The upstream side manifold 1 has a first flange portion 3 at the upstream end, and the first flange portion 3 is fixed to a side surface of a cylinder head (not shown). Further, the downstream side manifold 2 has a second flange portion 4 at the downstream end.
The flange portion 4 is connected to a catalytic converter (not shown). That is, the four flow passages of each cylinder become two flow passages at the connecting portion with the downstream side manifold 2, and finally become one flow passage at the inlet side of the catalytic converter. Reference numeral 5 denotes a bolt through hole (see FIG. 2) provided in the first flange portion 3, and 6 denotes a bolt through hole (see FIG. 3) provided in the second flange portion 4.

FIG. 2 shows only the upstream manifold 1. Although the cylinder head is not shown, the left side of the drawing is the front of the engine, and the # 1 cylinder, # 2 cylinder, # 3 cylinder, and # 4 cylinder are arranged in order from this front. The upstream manifold 1 is provided with four flow passages for each cylinder, but the flow passages of the # 1 cylinder and the flow passages of the # 4 cylinders located at the front and rear ends of the cylinder row are paired independently of each other. Exhaust pipes 11 and 12
It is composed by. This end exhaust pipe 11, 12
Is a metal pipe, for example, a stainless pipe bent by a means such as hydraulic forming. As shown in FIG. 2, the pair of end exhaust pipes 11 and 12 are assembled near the center of the cylinder row. , Are bent inward with respect to each other, and are bent downward from the first flange portion 3 as shown in FIG. Further, the downstream end portions 11a and 12a of the pair of end exhaust pipes 11 and 12 are arranged adjacent to each other so as to be continuous with the downstream manifold 2, but at the end portions 11a and 12a, The metal pipe is formed so that the cross section has a quadrant shape, that is, a 90 ° fan shape, and a semicircular shape is formed by arranging two openings at the downstream end of the quadrant shape adjacent to each other. Is configured. In the upstream portion close to the first flange portion 3, the metal pipes forming the end exhaust pipes 11 and 12 have a circular cross section. In addition, since the thermal expansion is absorbed in the branch portion constituted by the independent metal pipe as described above, the stress is less likely to be concentrated due to the thermal expansion.

On the other hand, the flow paths of the # 2 cylinder and the # 3 cylinder located at the center of the cylinder row are constituted by a central exhaust pipe 13 made of so-called sheet metal. 4 to 6 show only the central exhaust pipe 13. This central exhaust pipe 13
Is a two-piece metal plate 14, 15 formed in a half-divided form, which is so-called centered and integrated, and each metal plate 14, 15 is formed by pressing a steel plate, for example. These metal plates 14 are formed in a predetermined shape having flanges for welding at the edges and the intermediate portion thereof, respectively.
15 are welded together. As is clear in FIG.
The central exhaust pipe 13 has a pair of circular inlet portions 1 connected to the exhaust ports of the # 2 cylinder and the # 3 cylinder, respectively.
6 and 17, and a single outlet section 18 on the downstream side
And a Y-shaped flow path is formed inside. That is, the flow paths of the # 2 cylinder and the # 3 cylinder join each other inside the central exhaust pipe 13. As is apparent from FIGS. 5 and 1, the central exhaust pipe 13 is bent downward from the first flange portion 3 similarly to the end exhaust pipes 11 and 12, and particularly, the downstream end is Exhaust pipe 1
It extends so that it may overlap with the lower side of 1, 12. Further, the metal plate 14 on the upper surface side is gradually flattened toward the outlet portion 18, and finally, as shown in FIG. 6, the outlet portion 18 has a semicircular shape. This semi-circular shape has the downstream end portions 11a, 1 of the pair of end exhaust pipes 11, 12 described above.
It has a radius substantially equal to the semicircular shape formed by combining 2a.

As shown in FIG. 2, the central exhaust pipe 13 is provided.
The outlet portion 18 and the downstream end portions 11a and 12a of the pair of end exhaust pipes 11 and 12 are gathered at one location near the center of the cylinder row, and by combining the respective semicircular shapes, As a whole, it has a circular outer shape. Here, the downstream end portions 11 a and 12 a of the end exhaust pipes 11 and 12 project slightly longer than the outlet portion 18 of the central exhaust pipe 13. In addition, the central exhaust pipe 13
Is sandwiched between the pair of end exhaust pipes 11 and 12, and the joining portion of the Y-shaped flow passage is formed inside the pair of end exhaust pipes 11 and 12. It is located in a substantially triangular space. Therefore, the portion of the central exhaust pipe 13 that bulges upward close to the inlets 16 and 17 is just accommodated in the space, and the end exhaust pipes 11 and 12 and the central exhaust pipe 13 are extremely closed. Can be compactly combined.

The first flange portion 3 attached to the cylinder head is integrally continuous with the four cylinders in the illustrated example, but may be divided into a plurality of parts.

Next, the downstream manifold 2 has a pair of downstream exhaust pipes 19 and 2 made of independent metal pipes.
It is composed of 0s. These two downstream exhaust pipes 1
Reference numerals 9 and 20 are obtained by bending a stainless pipe into a predetermined curved shape by, for example, hydraulic forming and shaping the cross-section into a semicircular shape. As shown in FIG. 3 and FIG. Wall portions 19a, 20a along
Are placed back-to-back and adjacent to each other, and generally have the appearance of a single circular tube. Here, although each of the downstream side exhaust pipes 19 and 20 is integrated with each other by the second flange portion 4, the portions other than the second flange portion 4 are not constrained to each other and can be freely respectively. It is separate and independent so that it can be displaced.
Further, as shown in FIG. 7, a sufficient gap 21 through which outside air can flow is secured between the wall portions 19a and 20a adjacent to each other. By securing this gap 21, the wall portions 19a and 20a between the two flow paths are cooled, so that the local temperature rise is suppressed. The second flange portion 4 has a circular opening, and the pair of downstream side exhaust pipes 19 and 20 are collectively inserted and welded therein (see FIG. 3).

One of the downstream exhaust pipes 19 and 20 is connected to the downstream end portions 11a and 12a of the end exhaust pipes 11 and 12, and the other downstream exhaust pipe 20 is connected.
Is connected to the outlet 18 of the central exhaust pipe 13. Figure 8
Shows the details of this connection part.
Downstream end portions 11a, 12 of the pair of end portion exhaust pipes 11, 12
a is fitted to the inner peripheral side of the downstream side exhaust pipe 19 and is welded to each other along the tip edge of the downstream side exhaust pipe 19 (welded portion is indicated by reference numeral 21). Also, the central exhaust pipe 1
The outlet portions 18 of 3 are fitted to the outer peripheral side of the downstream side exhaust pipe 20 and are welded to each other along the tip edge thereof (welded portion is indicated by reference numeral 22). The welded portion 21 and the welded portion 22 are located apart from each other in the axial direction of the pipe so that they do not overlap each other. In particular, the welded portion 22 is located closer to the first flange portion 3 so that the downstream exhaust pipe 19 and the central exhaust pipe 13 located on the outer peripheral side do not overlap in the axial direction. In addition, even in this connection part,
The pair of downstream exhaust pipes 19 and 20 are not bound to each other.

Now, according to the configuration of the above embodiment, the end exhaust pipe 1 of the # 1 and # 4 cylinders, which has a relatively gentle curvature, is used.
Upstream manifold 1 within the range where bending of 1 and 12 is possible
It is possible to shorten the pipe length of the exhaust gas, and it is possible to shorten the flow path length to the catalytic converter while avoiding the interference between the exhaust gases of the # 1, # 4 cylinders and the exhaust gases of the # 2, # 3 cylinders. Get smaller. Therefore, it is advantageous for early activation of the catalyst. Moreover, as described above, the entire exhaust manifold can be downsized. In addition, with respect to thermal expansion, the central exhaust pipe 13 made of sheet metal is a small size corresponding only to the # 2 and # 3 cylinders, and the total length from the first flange portion 3 to the second flange portion 4 is increased. The exhaust pipes (the end exhaust pipes 11 and 12 and the downstream exhaust pipe 19) of the # 1 and # 4 cylinders
The exhaust pipes of the second and # 3 cylinders (the central exhaust pipe 13 and the downstream exhaust pipe 20) are structurally separated and independent of each other, and can be displaced independently of each other, thereby suppressing local stress concentration. be able to. Therefore, even if the thermal expansion and the thermal contraction are repeated, breakage does not occur and good durability can be secured.

In the downstream side exhaust pipes 19 and 20, the wall portions 19a and 20 are formed by the gap 21 as described above.
Since a is cooled, the temperature in the circumferential direction becomes uniform, and it is possible to avoid a decrease in strength and deterioration due to a local temperature increase.

By welding the upstream side manifold 1 and the downstream side manifold 2 with the connecting structure as shown in FIG. 8, the outer diameter of the connecting portion can be kept to a minimum, and the exhaust manifold can be further miniaturized. can do. Since each part including the welded parts 21 and 22 is externally welded,
High-cost spatterless welding is not particularly necessary.

[Brief description of drawings]

FIG. 1 is a sectional view of the entire exhaust manifold according to the present invention.

FIG. 2 is a front view of an upstream side manifold.

FIG. 3 is a front view of a second flange portion.

FIG. 4 is a side view showing only a central exhaust pipe.

5 is a view seen from the direction of arrow B in FIG. 4.

FIG. 6 is a view of the outlet portion viewed from the direction of arrow C in FIG.

7 is a cross-sectional view taken along the line AA of FIG.

FIG. 8 is a cross-sectional view of a connecting portion between the upstream side manifold and the downstream side manifold.

[Explanation of symbols]

1 ... Upstream manifold 2 ... Downstream manifold 3 ... 1st flange part 4 ... Second flange 11, 12 ... Exhaust pipe at the end 13 ... Central exhaust pipe 19, 20 ... Downstream exhaust pipe

Claims (7)

[Claims] 1. Exhaust gas from four cylinders, first to fourth cylinders, which are arranged in series and are provided with a first flange portion on the cylinder head side and a second flange portion on the downstream end side, Four
In the exhaust manifold of the internal combustion engine which guides the exhaust to the position of the second flange portion while being divided into the exhaust of the cylinder and the exhaust of the second cylinder and the exhaust of the third cylinder, the exhaust manifold includes The upstream manifold includes a downstream manifold including the second flange portion, the downstream manifold includes two adjacent flow passages, and the upstream manifold includes a first manifold. A pair of end exhaust pipes, each of which is formed of an independent metal pipe so as to respectively configure the flow paths of the cylinder and the fourth cylinder, and whose downstream ends are collectively connected to one of the flow paths of the downstream manifold; A downstream of which the flow paths of the second cylinder and the flow path of the third cylinder are formed by welding metal plates that are halved so as to form the flow path inside thereof and both flow paths merge in a Y shape Exit of , An exhaust manifold of an internal combustion engine, characterized in that it is composed of a central portion exhaust pipe connected to the other of the flow path of the downstream-side manifold. 2. The end exhaust pipes are each bent inward so as to gather near the center of the cylinder row, and the downstream end thereof is adjacent to the upper or lower side of the outlet of the central exhaust pipe. And the flow passage of the second cylinder and the flow passage of the third cylinder of the central exhaust pipe merge at a position closer to the first flange portion than the downstream end of the end exhaust pipe. The exhaust manifold of the internal combustion engine according to claim 1, wherein 3. A pair of end exhaust pipes each have an opening at a downstream end of a quadrant shape, and an outlet portion of the central exhaust pipe has a semicircular shape. The exhaust manifold for an internal combustion engine according to claim 1 or 2, wherein the outer shape of the downstream end is circular as a whole. 4. The two flow passages of the downstream manifold are
4. A pair of downstream side exhaust pipes each having a semicircular cross section and formed of a metal pipe, and a pair of downstream side exhaust pipes being adjacent to each other so as to have a circular cross section as a whole. Exhaust manifold for an internal combustion engine as described. 5. The exhaust manifold for an internal combustion engine according to claim 4, wherein the pair of downstream side exhaust pipes are separated and independent from each other except the second flange portion. 6. The exhaust manifold for an internal combustion engine according to claim 4, wherein a gap is provided between adjacent wall portions of the pair of downstream side exhaust pipes. 7. The downstream end of the pair of end exhaust pipes is fitted to the inner peripheral side of one of the downstream side exhaust pipes of the downstream side manifold at a connecting portion between the upstream side manifold and the downstream side manifold. The outlet of the central exhaust pipe is fitted to the outer peripheral side of the other downstream exhaust pipe of the downstream manifold, and is welded at different positions in the axial direction of the pipe. An exhaust manifold for an internal combustion engine according to any one of 1.