INTERNAL COMBUSTION ENGINE HAVING A CYLINDER HEAD AND A SECONDARY AIR SYSTEM

Abstract

An internal combustion engine has a cylinder head having an integrated exhaust manifold which has multiple exhaust ducts; and a secondary air system for supplying ambient air that is additionally supplied through an inlet as secondary air into the exhaust manifold into the exhaust gas flow downstream from the exhaust valves of the internal combustion engine during the cold-start phase. For fresh air supply, the secondary air system has a plurality of supply ducts that connect a distributor block of the secondary air system to an exhaust duct and are arranged in the integrated exhaust manifold and each provided with a valve assembly. Each valve assembly has a blocking means in the form of a closure flap that is pivotable about a pivot axis at a distance from the center of mass of the blocking means. According to the installation position of the internal combustion engine in a motor vehicle, and owing to this eccentric arrangement of the pivot axis, the blocking means assumes a defined closed position under the influence of gravity when there is no pressure difference between the exhaust manifold and the secondary air system and opens automatically under the influence of a relative overpressure in the gas pressure on the side of the secondary air system in relation to the gas pressure on the side of the exhaust manifold.

Claims

1. An internal combustion engine, comprising: a cylinder head having an integrated exhaust manifold which has multiple exhaust ducts, and a secondary air system, at least one valve assembly for restricting a fluid flow of the exhaust gas from the exhaust manifold to the secondary air system, wherein the exhaust manifold and the secondary air system are designed as integral components of the cylinder head, and wherein the secondary air system has a plurality of supply ducts that are connected to a respective exhaust duct in the integrated exhaust manifold with at least one valve assembly.

2. The internal combustion engine as set forth in claim 1, wherein each supply duct is equipped with a valve assembly.

3. The internal combustion engine as set forth in claim 1, wherein the valve assembly has a movable blocking means, particularly a closing flap.

4. The internal combustion engine as set forth in claim 1, wherein the blocking means is arranged so as to be pivotable about a pivot axis from the center of mass of the blocking means.

5. The internal combustion engine as set forth in claim 1, wherein, apart from the acting compressive forces, the blocking means is acted upon exclusively by gravity.

6. The internal combustion engine as set forth in claim 1, wherein the blocking means has a closed position that is configured so as to be inclined relative to the cross-sectional plane of the supply duct, and wherein the cross-sectional shape of the blocking means deviates from the cross-sectional area on the cross-sectional plane of the supply duct.

7. The internal combustion engine as set forth claim 1, wherein, in the absence of pressure difference, the blocking means assumes a parallel orientation relative to the main extension of the supply duct in a portion enclosing the blocking means.

8. The internal combustion engine as set forth in claim 1, wherein the blocking means is adjustable.

9. The internal combustion engine as set forth in claim 1, wherein the valve assembly is arranged within the internal combustion engine below a plane of the exhaust manifold.

10. A cylinder head for such an internal combustion engine as set forth in claim 1.

11. The internal combustion engine as set forth in claim 8, wherein the blocking means is adjustable by means of an actuator.

Description

[0026] The invention allows numerous embodiments. To further clarify its basic principle, one of them is illustrated in the drawing and will be described below. In the drawing:

[0027] FIG. 1 shows a perspective view of a cylinder head with an integrated exhaust manifold and with a secondary air system with a butterfly valve;

[0028] FIG. 2 shows a high-load operating state of the internal combustion engine with inactive secondary air system;

[0029] FIG. 3 shows a low-load operating state of the internal combustion engine with active secondary air system;

[0030] FIG. 4 shows an enlarged perspective view of the butterfly valve that is visible in FIG. 1; and

[0031] FIG. 5 shows a side view of the butterfly valve shown in FIG. 2.

[0032] The internal combustion engine according to the invention will be explained in greater detail below with reference to FIGS. 1 to 5. The internal combustion engine has a cylinder head 1 with an integrated exhaust manifold 2 that has multiple exhaust ducts 3. Furthermore, the internal combustion engine is equipped with a secondary air system 4 for supplying ambient air that is additionally supplied through an inlet 5 as secondary air into the exhaust manifold 2 into the exhaust gas flow downstream from the exhaust valves of the internal combustion engine during the cold-start phase. For fresh air supply, the secondary air system 4 has a plurality of supply ducts 7 that connect a distributor block 6 of the secondary air system 4 to an exhaust duct 3 and are arranged in the integrated exhaust manifold 2 and each provided with a valve assembly 8.

[0033] Each valve assembly 8 has a blocking means 10 in the form of a closure flap that is pivotable about a pivot axis 9, the pivot axis 9 being at a distance a from the center of mass of the blocking means 10. According to the installation position of the internal combustion engine as shown in FIG. 2 in a motor vehicle (not shown), and owing to this eccentric arrangement of the pivot axis, the blocking means assumes a defined closed position under the influence of gravity when there is no pressure difference between the exhaust manifold (2) and the secondary air system (4) or the gas pressure P1 on the side of the exhaust manifold 2 is greater than the gas pressure P2 on the side of the secondary air system 4.

[0034] As can be seen in FIG. 3, the blocking means 10 pivots automatically into the open position oriented parallel to the main extension of the supply duct 7 under the influence of a relative overpressure of the gas pressure P1 on the side of the secondary air system 4 relative to the gas pressure P2 of the side of the exhaust manifold 2, so that the fresh air can flow almost unimpeded through the supply duct 7.

[0035] In order to achieve a defined closed position of an orientation that is inclined relative to the cross-sectional plane of the supply duct 7 in the closed position, the blocking means 10 has an oval shape that is greater than the cross-sectional area in the supply duct 7 and therefore cannot be pivoted further, as can be seen in FIGS. 4 and 5.

LIST OF REFERENCE SYMBOLS

[0036] 1 cylinder head [0037] 2 exhaust manifold [0038] 3 exhaust duct [0039] 4 secondary air system [0040] 5 inlet [0041] 6 distribution block [0042] 7 supply duct [0043] 8 valve assembly [0044] 9 pivot axis [0045] 10 blocking means [0046] P1 gas pressure [0047] P2 gas pressure [0048] a distance