EXHAUST MANIFOLD FOR A MULTICYLINDER INTERNAL COMBUSTION ENGINE

Abstract

The present invention relates to a manifold for receiving exhausts from a multi-cylindrical internal combustion engine. The internal combustion engine has such a firing order that the riser in the manifold receives exhausts from two cylinders during an overlapping stage, simultaneously via an inlet opening arranged upstream and from an inlet opening arranged downstream in the riser. The riser comprises a substantially constant cross sectional area, except in one area, which is located in a position in connection with the inlet opening arranged downstream of the two inlet openings, receiving exhausts simultaneously. Said area has a geometry facilitating receipt and flow of exhausts in the predetermined direction in the riser, on occasions when the two inlet openings receive exhausts simultaneously.

Claims

1. A manifold for receiving exhausts from a multi-cylindrical internal combustion engine, wherein the manifold comprises at least three branch lines, each of which is adapted to receive exhausts from one of the cylinders of the internal combustion engine, and a riser adapted to lead exhausts in a predetermined direction, and inlet openings in various positions located downstream in the riser in order to receive exhausts from the respective branch lines, wherein the internal combustion engine has such a firing order that the riser receives exhausts from two cylinders during an overlapping stage, simultaneously via an inlet opening arranged upstream and from an inlet opening arranged downstream in the riser, wherein the riser comprises a flow passage with a substantially constant cross sectional area, except in one area located in a position in connection with the inlet opening arranged downstream of the two inlet openings, which receive exhausts simultaneously, wherein said area has a geometry which facilitates the receipt and the flow of exhausts in the predetermined direction in the riser on occasions when the two inlet openings receive exhausts simultaneously.

2. A manifold according to claim 1, wherein said area is located in a position immediately upstream of the inlet opening arranged downstream.

3. A manifold according to claim 1, wherein said area has a successively subsiding cross sectional area, from an inlet up to an outlet.

4. A manifold according to claim 1, wherein the riser comprises an internal wall surface, which defines the flow passage through said area.

5. A manifold according to claim 1, wherein the riser comprises a first wall side, comprising said inlet openings and a second opposite wall side, which is arranged on an opposite side of said inlet openings.

6. A manifold according to claim 1, wherein the internal combustion engine has such a firing order that the riser already receives an existing exhaust flow, via the inlet opening arranged downstream, at a time when an initial exhaust flow is received in the riser via the inlet opening arranged upstream.

7. A manifold according to claim 6, wherein the riser comprises a first wall side, comprising said inlet openings, and a second, opposite wall side, which is arranged on an opposite side of said inlet openings and in that the riser's first wall side has an angle in said area, in relation to the primary flow direction of the exhausts in other parts of the riser, which defines a successive subsiding of the cross sectional area of the flow passage in the area.

8. A manifold according to claim 7, wherein the manifold, which leads exhausts to the riser via the inlet opening, comprises an internal wall surface with a tapered portion giving the inlet opening an expanding cross sectional area.

9. A manifold according to claim 1, wherein the internal combustion engine has such a firing order that the riser already receives an existing exhaust flow, via the inlet opening arranged upstream, at a time when an initial exhaust flow is received in the riser via the inlet opening.

10. A manifold according to claim 9, wherein the riser comprises a first wall side, which comprises said inlet openings, and a second opposite wall side, arranged on an opposite side of said inlet openings, and in that the riser's second wall side has, in said area, a wedge-shaped portion comprising a first wall surface, with such a gradient that it reduces the flow passage's cross sectional area in the riser and a subsequent, second wall section with such a gradient that it expands the flow passage's cross sectional area in the riser, wherein the wedge-shaped portion is arranged in such a position that the exhaust flow led into the riser, via the inlet opening arranged downstream, hits the second wall surface.

11. A manifold according to claim 10, wherein the wedge-shaped portion has a height in the range of 3-10% of the diameter of the flow passage in the riser.

12. A manifold according to claim 10, wherein the first wall surface has a smaller angle in relation to the primary flow direction in the riser than has the second wall surface.

13. An internal combustion engine comprising at least one manifold for receiving exhausts from a multi-cylindrical internal combustion engine, wherein the manifold comprises at least three branch lines, each of which is adapted to receive exhausts from one of the cylinders of the internal combustion engine, and a riser adapted to lead exhausts in a predetermined direction, and inlet openings in various positions located downstream in the riser in order to receive exhausts from the respective branch lines, wherein the internal combustion engine has such a firing order that the riser receives exhausts from two cylinders during an overlapping stage, simultaneously via an inlet opening arranged upstream and from an inlet opening arranged downstream in the riser, wherein the riser comprises a flow passage with a substantially constant cross sectional area, except in one area located in a position in connection with the inlet opening arranged downstream of the two inlet openings, which receive exhausts simultaneously, wherein said area has a geometry which facilitates the receipt and the flow of exhausts in the predetermined direction in the riser on occasions when the two inlet openings receive exhausts simultaneously.

14. An internal combustion engine according to claim 13, comprising two of said manifolds as claimed in claim 13, wherein one of said manifolds is arranged on a first side of the internal combustion engine in order to receive exhausts from several cylinders, and said other of said manifolds is arranged on an opposite wall side of the internal combustion engine, in order to receive exhausts from a remaining number of cylinders.

15. A vehicle comprising an internal combustion engine comprising at least one manifold for receiving exhausts from a multi-cylindrical internal combustion engine, wherein the manifold comprises at least three branch lines, each of which is adapted to receive exhausts from one of the cylinders of the internal combustion engine, and a riser adapted to lead exhausts in a predetermined direction, and inlet openings in various positions located downstream in the riser in order to receive exhausts from the respective branch lines, wherein the internal combustion engine has such a firing order that the riser receives exhausts from two cylinders during an overlapping stage, simultaneously via an inlet opening arranged upstream and from an inlet opening arranged downstream in the riser, wherein the riser comprises a flow passage with a substantially constant cross sectional area, except in one area located in a position in connection with the inlet opening arranged downstream of the two inlet openings, which receive exhausts simultaneously, wherein said area has a geometry which facilitates the receipt and the flow of exhausts in the predetermined direction in the riser on occasions when the two inlet openings receive exhausts simultaneously.

16. A vehicle according to claim 15 comprising an internal combustion engine comprising two of said manifolds as claimed in claim 15, wherein one of said manifolds is arranged on a first side of the internal combustion engine in order to receive exhausts from several cylinders, and said other of said manifolds is arranged on an opposite wall side of the internal combustion engine, in order to receive exhausts from a remaining number of cylinders.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0019] Below is a description, as an example, of preferred embodiments of the invention with reference to the enclosed drawings, on which:

[0020] FIG. 1 shows a first manifold and a second manifold, each of which receives exhausts from four cylinders in an internal combustion engine,

[0021] FIG. 2 shows a cross sectional view of the first manifold in an area A-A in FIG. 1, and

[0022] FIG. 3 shows a cross sectional view of the second manifold in an area B-B in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0023] FIG. 1 shows an internal combustion engine 1 with eight cylinders c.sub.1-8. The internal combustion engine 1 in this case is a V8 engine. Each one of the cylinders c.sub.1-8 is connected with a branch line 2a.sub.1-4, 2b.sub.1-4 that ejects exhausts from the respective cylinders c.sub.1-8. The exhausts from the cylinders c.sub.1-4 on one of the sides of the internal combustion engine 1 are led, via branch lines 2a.sub.1-4 and inlet openings 3a.sub.1-4, to a first riser 4a. The exhausts from the cylinders c.sub.5-8 on the other side of the internal combustion engine 1 are led, via branch lines 2b.sub.1-4 and inlet openings 3b.sub.1-4, to a second riser 4b. The branch lines 2a.sub.1-4 and the riser 4a define a first manifold 5a. The first manifold 5a transitions into a first exhaust conduit 6a, which leads the exhausts to a non-displayed turbo charger. The manifolds 2b.sub.1-4 and the riser 4b define a second manifold 5b. The second manifold 5b transitions into a second exhaust conduit 6b, which leads the exhausts to a non-displayed turbo charger.

[0024] The exhaust flow from each one of the cylinders c.sub.1-8 is controlled by at least one exhaust valve, which is arranged in such a manner that it may be shifted between a closed state and an open state. Usually, each one of the cylinders c.sub.1-8 is equipped with two exhaust valves to facilitate the ejection of the exhausts. When the exhaust valves open, initially an exhaust flow with a high pressure is ejected from the cylinders c.sub.1-8, via the respective branch lines 2a.sub.1-4, 2b.sub.1-4 and the inlet opening 3a.sub.1-4, 3b.sub.1-4 to the risers 4a, 4b. For the remainder of the duration when the cylinders c.sub.1-8 are open, the exhausts are ejected with a lower pressure to the risers 4a, 4b. This lower pressure is substantially defined by the movements of the piston in the cylinders c.sub.1-8, when it presses the exhausts out into the respective branch lines 2a.sub.1-4, 2b.sub.1-4 Since each of the manifold's risers 4a, 4b receives exhausts from four cylinders cats, it is substantially impossible to avoid that the opening times of the exhaust valves of at least two cylinders c.sub.1-8 overlap. The risers 4a, 4b will thus receive exhausts from more than one cylinder c.sub.1-8 during a certain part of the internal combustion engine's working cycle.

[0025] The firing order for the internal combustion engine's cylinders c.sub.1-8 is in this case c.sub.1, c.sub.5, c.sub.4, c.sub.2, c.sub.6, c.sub.3, c.sub.7, c.sub.8. With such a firing order the exhaust valves of the cylinders c.sub.2, c.sub.4 will be open simultaneously. The exhaust valve of the cylinder c.sub.2 opens when the exhaust valve of the cylinder c.sub.4 is already open. When this happens, exhausts with a high pressure are ejected from the branch line 2a.sub.2, while exhausts with a lower pressure are ejected from the branch line 2a.sub.4. In a conventional manifold, in this case a part of the exhausts flowing through the first riser 4a with a high pressure will be led into the branch line 2a.sub.4. Accordingly, the pressure rises in the branch line 2a.sub.4, where exhausts are ejected with a lower pressure. Accordingly, the piston in the cylinder c.sub.4 must work harder to pump out the exhausts. With the above mentioned firing order the opening times of the exhaust valves of the cylinders c.sub.7, c.sub.8 will also overlap. In this case, the exhaust valve of the cylinder c.sub.8 opens, when the exhaust valve of the cylinder c.sub.7 is already open. When this happens, exhausts with a high pressure are ejected from the branch line 2b.sub.4, while exhausts with a lower pressure are ejected from the branch line 2b.sub.3. In a conventional manifold a part of the exhausts that flows through the manifold 2b.sub.4 with a high pressure will be led in the wrong direction in the second riser 4b. Thus, the pressure in the branch line 2b.sub.3 rises when exhausts are ejected with a lower pressure. Accordingly, the piston in the cylinder c.sub.7 must work harder to pump out the exhausts.

[0026] FIG. 2 shows a cross sectional view through the connecting area, where the branch line 2a.sub.4 ejects exhausts into the first riser 4a. The first riser 4a has an inner wall side 4a.sub.1 located on the same side as the branch lines 2a.sub.1-4 and the inlet openings 3a.sub.1-4. The first riser 4a has an external wall side 4a.sub.2 located on an opposite side of the branch lines 2a.sub.1-4 and the inlet openings 3a.sub.1-4. The first riser 4a has an area A, with an extension from an inlet A.sub.1 to an outlet A.sub.2. The outlet A.sub.2 is located in connection with the inlet opening 3a.sub.4, where the riser 4a receives exhausts from the branch line 2a.sub.4. The first riser 4a comprises a flow passage with a substantially constant cross sectional area upstream and downstream of the area A, with respect to the intended flow direction of the exhausts in the riser 4a. In the area A, the inner wall side 4a.sub.1 of the first riser 4a has an angle in relation to the primary flow direction of the exhaust flow in the first riser 4a. Upstream and downstream of the first area A, the first riser's 4a inner wall side 4a.sub.1 has a linear extension, which is substantially parallel with the primary flow direction of the exhaust flow in the first riser 4a. The second riser's 4a external wall side 4a.sub.2 has a substantially linear extension in the entire riser 4a. The first riser's inner wall side 4a.sub.1 has a gradient, such that the distance between the inner wall side 4a.sub.1 and the outer wall side 4a.sub.2 subsides continuously from the inlet A.sub.1 to the outlet A.sub.2 in the first area A. In this case the distance subsides linearly. Thus, a successively narrowing cross sectional area is created for the exhaust flow in the first area A. The branch line 2a.sub.4, which leads exhausts to the riser 4a via the inlet opening 3a.sub.4, comprises a wall surface with a tapered portion 2a.sub.41, providing the inlet opening 3a.sub.4 with an expanding cross sectional area. With such a tapered portion, the inlet opening 3a.sub.4 obtains a funnel-like shape. In an inlet opening 3a.sub.4 with such a shape, an exhaust vortex is formed. It may be noted that the inward bend in the area A has been exaggerated in the figures, in order to more clearly exemplify the invention.

[0027] On occasions when the exhaust valves in the cylinder c.sub.4 are open and when the exhaust valves in the cylinder c.sub.2 open, a powerful initial exhaust flow is provided from the cylinder c.sub.2, via the second branch line 2a.sub.2 and the inlet opening 3a.sub.2, to the riser 4a. When this exhaust flow reaches the area A, the exhaust flow provides an acceleration through the subsiding cross sectional area. The first riser 4a may have a reduced cross sectional area in the range of 10-40%, for example 30%, at the outlet A.sub.2 in relation to at the inlet A.sub.1 of the area A. Accordingly, the exhausts that leave the first area A obtain a reduced static pressure in connection with the inlet opening 3a.sub.4. Accordingly, the propensity of the exhaust flow leaving the area A to penetrate into the branch line 2a.sub.4 is counteracted. The inner wall side 4a.sub.1 thus has an angle in relation to the exhaust flow's primary flow direction in the first area A. The inner wall side 4a.sub.1 has an angle, such that the exhaust flow obtains a relatively soft directional change in connection with the first wall side 4a.sub.1 in the area A. The inner wall side 4a.sub.1 reduces the exhaust flow in the area A on the side where the first riser 4a receives exhausts via the inlet opening 3a.sub.4. The directional change, which the exhaust flow obtains in the first area A, in connection with the inner wall side 4a.sub.1, means that the exhaust flow is led in a direction partly away from the inlet opening 3a.sub.4. This makes it even more difficult for the exhausts leaving the area A to penetrate into the branch line 2a.sub.4. At the same time, an area is created in the riser 4a into which the exhausts with the lower pressure, leaving the branch line 2a.sub.4, may be led. The exhaust vortex formed in the funnel shaped area of the branch line 2a.sub.4 in connection with the inlet opening 3a.sub.4 also makes it difficult for the exhausts leaving the area A to penetrate into the branch line 2a.sub.4.

[0028] FIG. 3 shows a cross sectional view through the connecting area, where the second riser 4b receives exhausts from the branch line 2b.sub.4 via the inlet opening 3b.sub.4. The second riser 4b has an inner wall side 4b.sub.1, located on the same side as the branch line 2b.sub.4 and the inlet opening 3b.sub.4. The second riser 4b has an outer wall side 4b.sub.2, located on an opposite side of the branch line 2b.sub.4 and the inlet opening 3b.sub.4. The second riser 4b has an area B, which extends from an inlet B.sub.1 to an outlet B.sub.2. The first riser 4b comprises a flow passage with a substantially constant cross sectional area upstream and downstream of the area B, with respect to the intended flow direction of the exhausts in the riser 4b.

[0029] The second riser's 4b outer wall side 4b.sub.2 has a wedge-shaped portion in the second area B, comprising a first wall surface 4b.sub.21 with a gradient, such that it reduces the cross sectional area of the flow passage in the riser 4b, and a subsequent second wall surface 4b.sub.22 with a gradient, such that it expands the flow passage's cross sectional area in the riser 4b. It may be noted that the inward bend in the area B has been exaggerated in the figures, in order to exemplify the invention more clearly

[0030] The first wall surface 4b.sub.21 and the second wall surface 4b.sub.22 have a breaking point 4b.sub.23. The wedge-shaped portion is arranged in such a position that the exhaust flow led into the riser 4b, via the inlet opening 3b.sub.4 arranged downstream, only hits the second wall surface 4b.sub.22. The entire exhaust flow from the branch line 2b.sub.4 thus hits to the right of the breaking point 4b.sub.23. The exhaust flow from the branch line 2b.sub.4 should, however, hit as close to the breaking point 4b.sub.23 as possible.

[0031] The wedge-shaped portion has a height in the range of 3-10% of the flow passage's diameter in the riser 4b. The wedge-shaped portion may have a height of approximately 5% of the diameter of the flow passage. Thus, the wedge-shaped portion protrudes a relatively small distance into the second riser 4b. The flow losses in the area are accordingly relatively minor. The first wall surface 4b.sub.21 has an angle of approximately 1° in relation to the primary flow direction in the riser, and the second wall surface 4b.sub.22 has an angle of approximately 5° in relation to the primary flow direction in the riser 4b. It is thus sufficient that the second wall surface has a sufficiently small angle to direct the exhausts are leaving the branch line 2b.sub.4 and hitting the surface in a desired direction in the riser 4b. The second riser's 4b outer wall side 4b.sub.2 has, upstream and downstream of the area B, a linear extension that is parallel with the primary flow direction of the exhaust flow in the second riser 4b. The second riser's 4b inner wall side 4b.sub.1 has a substantially linear extension.

[0032] On occasions when the exhaust valves of the cylinder c.sub.7 are open and when the exhaust valves of the cylinder c.sub.8 open, a powerful initial exhaust flow is provided from the cylinder c.sub.8, via the branch line 2b.sub.4 and the inlet opening 3b.sub.4, to the second riser 4b. At the same time, exhausts with a lower pressure are led from the cylinder c.sub.7, via the branch line 2b.sub.3 and the inlet opening 3b.sub.3, to the second riser 4b. The first wall surface 4b.sub.21 of the wedge-shaped portion directs the exhaust flow with the lower pressure toward the exhausts with the higher pressure, which flow out of the inlet opening 3b.sub.4 arranged downstream. The second wall surface 4b.sub.22 of the wedge-shaped portion has a gradient, such that it leads the exhausts with the higher pressure in the intended flow direction in the riser 4b. The wedge-shaped portion prevents substantially any part of the exhausts with the higher pressure from being led into an incorrect counterflow direction in the riser 4b. Said areas A, B which are located in the risers 4a, 4b, have geometries which may be created in a casting process relatively easily. The manifolds 5a, 5b are thus advantageously made in a casting process.

[0033] The internal combustion engine 1 thus has two manifolds 5a, 5b, which receive exhausts from two different sides of the internal combustion engine 1. With knowledge about the internal combustion engine's firing order both the manifolds 5a, 5b have been equipped with areas A, B in connection with the inlet opening 2a.sub.4, 2b.sub.4 arranged downstream, for supply of exhausts from two cylinders c.sub.2, c.sub.4, c.sub.7, c.sub.8 having overlapping opening times of the exhaust valves. The areas A, B have sections with different geometries, in order to receive and lead the exhausts in a predetermined direction in the respective risers 4a, 4b on the different sides of the internal combustion engine 1, depending on if the inlet opening arranged downstream 2a.sub.4, 2b.sub.4 supplies exhausts with the higher pressure or the lower pressure.

[0034] The invention is in no way limited to the embodiment described above, but may be varied freely within the framework of the claims. The manifold may receive exhausts from a varying number of cylinders in an internal combustion engine.