CYLINDER HEAD FOR AN INTERNAL COMBUSTION ENGINE, INTERNAL COMBUSTION ENGINE, AND METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE

Abstract

A cylinder head (4) for an internal combustion engine has a first inlet duct (8) that is configured to bring about a first tumbling movement and a second inlet duct (9) that is configured to bring about a second tumbling movement of the air quantities that flow through the cylinder head (4) and into a cylinder of the internal combustion engine (1). An internal combustion engine and a method for operating an internal combustion engine also are provided.

Claims

1. A cylinder head for an internal combustion engine that has a crankcase with a cylinder having a piston that moves in the cylinder in an oscillating manner, the cylinder head comprising at least one outlet duct that is selectively openable and closeable and first and second inlet ducts that are selectively openable closeable, the cylinder head, the cylinder and the piston forming a combustion chamber, wherein the first inlet duct is configured to generate a first tumbling movement of an air quantity that flows through the first inlet duct and into the cylinder, and the second inlet duct being configured to generate a second tumbling movement of the air quantity that flows through the second inlet duct and into the cylinder.

2. The cylinder head of claim 1, wherein the first inlet duct is a tangential duct and is configured to bring about a directional change of the air quantity in comparison with the first inlet duct.

3. The cylinder head of claim 2, wherein the second inlet duct has a planar face section to bring about the directional change of the air quantity.

4. The cylinder head of claim 1, wherein the first inlet duct has a first inlet valve with a first lift and the second inlet duct has a second inlet valve.

5. The cylinder head of claim 4, wherein the first lift is greater than the second lift.

6. The cylinder head of claim 4, wherein the first lift is equal to the second lift.

7. The cylinder head of claim 4, wherein the valve lifts are adjustable.

8. The cylinder head of claim 1, further comprising a cover face in a region of first or second inlet openings of the first and second inlet ducts respectively and has a mask facing toward or away from the combustion chamber.

9. The cylinder head of claim 8, wherein the mask is configured in a region of the second inlet opening that faces away from the first inlet duct.

10. The cylinder head of claim 8, wherein the mask is configured, starting from a cylinder edge that extends from the second inlet opening to the second outlet duct and between the second inlet opening and the second outlet duct.

11. The cylinder head of claim 1, wherein the internal combustion engine has a stroke/bore ratio with a value of less than or equal to 1.0.

12. An internal combustion engine, having a crankcase and the cylinder head of claim 1.

13. A method for operating an internal combustion engine, the internal combustion engine having a crankcase that has a cylinder with a piston that moves in the cylinder in an oscillating manner, and a cylinder head that has at least one outlet duct and two inlet ducts, an outlet valve for selectively opening and closing the outlet duct and inlet valves for selectively opening and closing the inlet ducts, the cylinder head, the cylinder and the piston defining a combustion chamber, and each valve having a valve lift, an overall air quantity for the combustion of a fuel quantity in the cylinder being sucked in via the inlet ducts, and the overall air quantity consisting of an air quantity that is sucked in via the first inlet duct and an air quantity that is sucked in from the second inlet duct, and the two air quantities that are sucked in having a certain movement in the cylinder, the method comprising: using the first inlet duct for generating a tumbling movement of the air quantity that is sucked in via the first inlet duct, and using the second inlet duct for generating a reverse tumbling movement of the air quantity that is sucked in via the second inlet duct.

14. The method of claim 13, wherein the valve lifts of the valves of the inlet ducts are set differently.

15. The method of claim 14, wherein in a lower and medium part load range and rotational speed range of the internal combustion engine, the valve lift of the valve of the first inlet duct (8) is set to be greater than the valve lift of the valve of the second inlet duct.

16. The method of claim 15, wherein in a load range of from 0% to 30% of a full load of the internal combustion engine, the second inlet duct remains closed in a gas exchange phase.

17. The method of claim 13, wherein in a load range of from 20 to 60% of a full load of the internal combustion engine, the valve lifts of the valves of the inlet ducts are set differently.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a plan view of a detail of a cylinder head of an internal combustion engine according to the invention.

[0026] FIG. 2 is a perspective view of a detail of the cylinder head of FIG. 1.

[0027] FIG. 3 is a perspective view of flow lines of a flow simulation in the cylinder head of FIG. 2.

[0028] FIG. 4 is a crank angle/valve lift diagram showing valve lifts of the internal combustion engine according to the invention.

DETAILED DESCRIPTION

[0029] An internal combustion engine 1 according to the invention is illustrated in FIG. 1 and has a crankcase 2 with at least one cylinder 3. A piston can be moved in an oscillating manner in the cylinder 3. The piston is mounted in the crankcase 2 on a crankshaft. An end of the cylinder 3 that faces away from the crankshaft has a cylinder head 4, and a combustion chamber 5 is defined in the cylinder 3 between the piston and the cylinder head 4.

[0030] The cylinder head 4 comprises a first outlet duct 6, a second outlet duct 7, a first inlet duct 8 and a second inlet duct 9.

[0031] The ducts 6, 7, 8, 9 can be opened and closed with the aid of valves, such as those in the patent documents identified above. The valves are disk valves and each has a defined valve lift based on the possible axial movement along a longitudinal axis of the respective valve. The first outlet valve is assigned to the first outlet duct 6 and has an outlet valve lift HA that corresponds to the valve lift of the second outlet valve, which is assigned to the second outlet duct 7.

[0032] The first inlet valve is assigned to the first inlet duct 8 and has a first inlet valve lift HE1 that can differ from the second inlet valve lift HE2 of the second inlet valve 9 to achieve an asymmetry of the valve lifts of the inlet valves 8, 9. A reduced valve lift HE2 of the second inlet valve 9 and a further reduced valve lift HE2 of the second inlet valve 9 are illustrated in the crank angle/valve lift diagram of FIG. 4. It is not absolutely necessary that the internal combustion engine 1 has only one of the valve lifts HE2, HE2, HE2. For example, a variable valve lift might be realized with the aid of a variable camshaft or with the aid of a camshaft adjuster.

[0033] The first inlet duct 8 is configured as a tumbling duct or a tangential duct to bring about a tumbling movement of the air quantity that flows through the first inlet duct 8 and into the cylinder 3. Thus, a tumbling movement is imparted to the air quantity that flows through the first inlet duct 8 during the compression phase in the combustion chamber. The tumbling movement is a circulating movement that is in contrast to a swirl movement that is orientated in a rotational manner about a cylinder axis. Rather the tumbling movement takes place about a cylinder transverse axis 11 that is transverse to the cylinder axis 10.

[0034] The second inlet duct 9 is configured to form a reverse tumbling movement of the air quantity that flows through the second inlet duct 9 into the cylinder 3. This means that the direction of the reverse tumbling movement is opposed to the tumbling movement. Therefore, two tumbling movements can be brought about with the aid of the cylinder head 4 based on the corresponding design of the inlet ducts 8, 9.

[0035] As illustrated in FIGS. 1 and 2, the second inlet duct 9 is configured as a reverse tumble duct starting from an inlet opening 12 upstream of a duct inlet opening 13 of the second inlet duct 9 for streaming the air quantity the flows through it in a direction opposed from a cylinder center. Thus, the air quantity that flows through the first inlet duct 8 flows in a direction of the cylinder center, and the air quantity that flows through the second inlet duct 9 is conducted substantially in the opposite direction. To bring about the directional change, the second inlet duct 9 has a planar face section 18 close to the inlet opening 12. The planar face section 18 extends along an extent axis 19 that is approximately parallel to the cylinder axis 10. The extent axis 19 also could start from a surface point of the face section 18 that lies on the extent axis 19 in a manner that faces away from the inlet opening 12, so as to be inclined in the direction of a cylinder edge 17 of the cylinder 3, where the cylinder edge 17 faces away from the second outlet duct 7.

[0036] In principle, the inflow direction of the air quantity of the reverse tumble duct 9 into the combustion chamber 5 can be described as being directed counter to the tumble duct 8. That air quantity of the first inlet duct 8 that has the tumbling movement and that air quantity of the second inlet duct 9 which has the reverse tumbling movement meet one another in the combustion chamber 5, and further movements are initiated on account of the movements that are directed in an opposed manner. Substantially three movement forms or flows occur with different directions, namely: a tumbling movement that is configured obliquely in the combustion chamber 5, a pure tumbling movement that rotates about the cylinder transverse axis 11, and a resulting swirl movement of the air quantity that moves in the combustion chamber 5.

[0037] That air quantity proportion of the air quantity that is present in the combustion chamber 5 that has a swirl component or a swirl movement is fundamentally in the region of a piston crown of the piston. The piston crown is configured to face the combustion chamber 5, and on a cylinder head face of the cylinder head 4, where the cylinder head face delimits the combustion chamber 5. The tumbling movement of oblique configuration is present substantially on a cylinder wall of the cylinder 3, and the pure tumbling movement is present substantially in the center of the combustion chamber 5, as shown by way of example in FIG. 3.

[0038] An air movement that is substantially more stable than the tumbling movement in the form of a swirl movement, as is achieved with the combination of the tumbling movement and the reverse tumbling movement, can be improved in the low to medium load range and rotational speed range of the internal combustion engine 1 with the aid of an asymmetry of the valve lifts HE1, HE2 of the inlet valves.

[0039] The boosting of the resulting swirl movement is achieved if the first inlet valve lift HE1 of the valve of the first inflow duct 8 that is configured as a tangential duct is of greater configuration than the second inlet valve lift HE2 of the valve of the second inflow duct 9 which is configured to bring about a reverse tumbling movement. Therefore, the air quantity with the tumbling movement is greater than the air quantity that has the reverse tumbling movement, and the resulting swirl movement is boosted in comparison with equally great air quantities which flow through the inflow ducts 8, 9.

[0040] What is known as a zero lift of the valve of the second inflow duct 9 leads in a lowermost load range of the internal combustion engine 1 to a preferred resulting swirl movement in the combustion chamber 5. This is to be substantiated by the fact that the air quantity that flows through the first inflow duct 8 into the combustion chamber 5 has the tumbling movement and an increased propagation volume is available to it in the combustion chamber 5 on account of the closed second inflow duct 9, and a vacuum relative to the pressure in the region of the inlet opening 12 is present, as a result of which the tumbling movement is converted into the resulting swirl movement.

[0041] A mask 15 is configured in the region of the further inlet openings 14 in the combustion chamber 5 generates boosting of the resulting swirl movement, in particular in the case of reduced valve lifts of the valve of the second inlet duct 9. The mask 15 is in the form of a lug that protrudes into the combustion chamber 5. Additionally, the mask is configured on a cover face 16 of the combustion chamber 5 and particularly a cover face 16 assigned to the cylinder head 4. Starting from a cylinder edge 17, the mask 15 extends between the second outlet duct 7 and the second inlet duct 9. More particularly, starting from the cylinder edge 17 that extends from the further inlet opening 14 to the second outlet duct 7, the mask 15 is configured to extend between the further inlet opening 14 and the second outlet duct 7.

[0042] The method according to the invention and the internal combustion engine 1 according to the invention are advantageous, in particular, in the case of a stroke/bore ratio of the internal combustion engine 1 having a value of less than or equal to 1.0.

[0043] The method according to the invention for operating the internal combustion engine 1 is distinguished by the fact that a tumbling movement of the air quantity that is sucked in via the first inlet duct 8 is generated with the aid of the first inlet duct 8, and a reverse tumbling movement of the air quantity that is sucked in is generated with the aid of the second inlet duct 9. This preferably takes place by way of the correspondingly shaped inlet ducts 8, 9, but might also be brought about in a different way.

[0044] To achieve advantageous reduced emissions in the low to medium part load range and rotational speed range of the internal combustion engine 1, the valve lifts HE1, HE2 of the valves of the inlet ducts 8, 9 are set differently. In particular, the first valve lift HE1 of the first inlet duct 8 has a greater value than the second valve lift HE2 of the second inlet duct 9. This means that, in the lower and medium part load range and rotational speed range of the internal combustion engine 1, the first valve lift HE1 of the valve of the first inlet duct 8 is set to be greater than the second valve lift HE2 of the valve of the second inlet duct 9. The second valve lift HE2 might correspond to a reduced valve lift HE2 or a further-reduced valve lift HE2.

[0045] The first valve lift HE1 might also be a maximum valve lift of the valve of the first inlet duct 8 and its value might remain unchanged, the value of the second valve lift HE2 being reduced, however. That is to say, in other words, that, in the lower and medium load range and/or rotational speed range, the first valve lift HE1 does not necessarily have to be the maximum possible valve lift of the first inlet valve. A difference between the valve lifts of the inlet valves is necessary to achieve the advantages of the method according to the invention, it being necessary for the valve lift of the first inlet valve to be greater than the valve lift of the second inlet valve.

[0046] In a further embodiment of the method according to the invention, the second inlet duct 9 remains closed in the gas exchange phase in a load range of from 0 to 30% of a full load of the internal combustion engine 1. That is to say, that exclusively the first inlet duct 8 is opened and no air quantity can be sucked in by the cylinder 3 via the second inlet duct 9.

[0047] The valve lifts HE1, HE2 of the valves of the inlet ducts 8, 9 might likewise be set differently, in particular in a load range of from 20 to 60% of a full load of the internal combustion engine 1.

LIST OF DESIGNATIONS

[0048] 1 Internal combustion engine

[0049] 2 Crankcase

[0050] 3 Cylinder

[0051] 4 Cylinder head

[0052] 5 Combustion chamber

[0053] 6 First outlet duct

[0054] 7 Second outlet duct

[0055] 8 First inlet duct

[0056] 9 Second inlet duct

[0057] 10 Cylinder axis

[0058] 11 Cylinder transverse axis

[0059] 12 Inlet opening

[0060] 13 Duct inlet opening

[0061] 14 Further inlet opening

[0062] 15 Mask

[0063] 16 Cover face

[0064] 17 Cylinder edge

[0065] 18 Face section

[0066] 19 Extent axis

[0067] HA Outlet valve lift

[0068] HE1 First inlet valve lift

[0069] HE2 Second inlet valve lift

[0070] HE2 Reduced valve lift, second inlet valve

[0071] HE2 Further-reduced valve lift, second inlet valve