Patent Application
20080035127
Preferred exemplary embodiments of the present invention are illustrated in the drawings and explained in greater detail in the following description, where the same reference numerals are used to refer to the same or similar or functionally identical components.
The figures each show in schematic diagrams
According to
The engine block 2 contains multiple cylinders 5; three cylinders 5 are shown in this example without restricting the general scope in any way. Each cylinder 5 encloses a combustion chamber 6 and guides a piston (not shown) in a known manner. At least one intake valve 7 and at least one exhaust valve 8 are allocated to each cylinder 5. The intake valves 7 are designed and arranged in such a way that they are able to open and close a fresh gas intake, not discussed further here, of the respective combustion chamber 6 in the usual manner. In a corresponding manner, the exhaust valves 8 are designed and arranged in such a way that they are able to open and close an exhaust outlet (not shown) of the respective combustion chamber 6. The respective valve control is not shown. The charge cycle valves 7, 8 may be controlled by means of camshafts in the traditional manner, which can be implemented in a comparatively inexpensive manner. It is likewise possible to provide an electromagnetic valve control.
In addition, a fuel injector 9 is assigned to each cylinder 5, capable of injecting fuel into the respective combustion chamber 6 when controlled accordingly. The fuel injectors 9 are connected to a joint fuel supply line 15, for example, which supplies fuel under a high pressure.
The fresh gas system 3 comprises at least one joint fresh gas line 10 which is connected to a plurality of individual fresh gas pipes 11 so they communicate, each fresh gas pipe 11 leading to one of the combustion chambers 6, i.e., to one of the cylinders 5. In the present case the fresh gas line 10 and the fresh gas pipes 11 are interconnected by a fresh gas distributor 12. In another embodiment, the fresh gas pipes 11 may also be connected directly to the fresh gas line 10.
Each fresh gas pipe 11 contains a clocked valve 13 that is designed so that it can open and close the respective fresh gas pipe 11. For actuating the clocked valves 13 and the fuel injectors 9, a controller 14 is provided. This controller 14 has access to signals or to information in general that makes it possible for the controller to determine the prevailing load state of the internal combustion engine 1. The term “load state” comprises in particular the prevailing load and power output as well as the prevailing rotational speed of the internal combustion engine 1. For example, the controller 14 is connected to an engine control unit (not shown here). Likewise, the controller 14 may be integrated in terms of hardware and/or implemented in the software in such an engine control unit.
The exhaust system 4 comprises individual exhaust pipes 16 in the usual way, these pipes being connected to a joint exhaust line 18 either directly or, as is the case here, via an exhaust collector 17.
The internal combustion engine 1 and/or its fresh gas system 3 is/are dethrottled. This means that the internal combustion engine 1 and/or its fresh gas system 3 does not contain any device for load-dependent throttling of the fresh gas supply to the individual combustion chambers 6. However, the internal combustion engine 1, e.g., in the engine block 2, may have a throttle mechanism basically for safety reasons, e.g., for emergency running properties, although it does not have any throttle function in the traditional sense during normal operation. In particular, the internal combustion engine 1 and/or its fresh gas system 3 does not have a throttle valve in the fresh gas line 10. Consequently, essentially ambient pressure prevails in the line system of the fresh gas system 3, optionally throttled slightly by an air filter (not shown) and/or an intake pressure generated by the intake of the individual cylinders 5 during an intake stroke or intake cycle of the respective piston prevails in the line system of the fresh gas system 3 if this pressure is allowed through by the clocked valves 13 into the remaining line system of the fresh gas system 3. The slight vacuum optionally prevailing due to said slight throttling is at any rate definitely lower in amount than a vacuum prevailing with a conventional throttle system, i.e., with a throttled combustion engine, at least in partial-load operation.
The closed clocked valve 13 and the deactivated fuel injector 9 are each represented by a zero-line in the diagram, while the opened clocked valve 13 and the activated fuel injector 9 are each represented by a one-line. The clocked valves 13 thus have only two switch states “open” and “closed” during operation, which differentiates the clocked valves 13 from traditional throttle valves. The behavior of the fuel injector 9 is also represented here by the states “active” and “inactive” for simplification. It is clear that more complex injection processes can be implemented for the actual course of fuel injection.
The controller 14 is designed so that it can control the clocked valves 13 and the fuel injector 9 to implement an operating method for the internal combustion engine 1 as explained in greater detail below.
During operation of the internal combustion engine 1, each piston executes an intake stroke cyclically during its intake cycle, beginning at top dead center TDC and ending at bottom dead center BDC. The respective intake valve 7 is linked to the piston movement, e.g., via a camshaft control. During the intake stroke, the respective intake valve 7 has an intake time window T, which is indicated by a curly bracket in
During the intake stroke of the piston, the respective combustion chamber 6 must be loaded with fresh gas. The quantity of fresh gas, i.e., the fresh gas charge to be introduced into the combustion chamber 6, depends on the prevailing load state and the rotational speed of the internal combustion engine 1.
The present invention now proposes controlling the quantity of fresh gas to be supplied to the respective combustion chamber 8 with the help of the respective clocked valve 13.
The fresh gas is metered not by throttling the respective fresh gas pipe 11 but instead by appropriate adjustment of the time during which both the intake valve 7 and the respective clocked valve 13 are open. Essentially, the clocked valve 13 may thus open within the intake time window T, remain open for a predetermined charging time and then close again. In addition, it is fundamentally possible to implement two or more opening phases of the clocked valve 13 that are separated from one another in time but are still within the intake time window T, at least during partial-load operation of the internal combustion engine 1. However, the embodiment shown in
The actual fresh gas charging takes place in the preferred embodiment shown here during an overlap between the opening phases of the clocked valve 13 on the one hand and the opening phase of the intake valve 7 on the other hand. This overlap is represented as hatched areas in
It is noteworthy that metered addition of unthrottled quantities of fresh gas to the individual cylinders 5 and/or combustion chambers 6 is implemented here through selected control of the clocked valves 13. Pulse charging is not implemented here regularly, at least in partial-load operation. However, in full-load operation, the clocked valves 13 may be controlled for implementation of pulse charging.
According to
In the example shown here, a separate fuel injection is provided for each of the two charging phases A, B which occur at different points in time. Accordingly, the first injection quantity F1 is injected during the first charging phase A and the second injection quantity F2 is injected during the second charging phase B. Injection of fuel during the time within which fresh gas also flows into the respective combustion chamber 6 improves the formation of the mixture in the respective combustion chamber 6. An embodiment in which the chronological position of the respective injection time is selected so that the velocity of flow of the fresh gas reaches its maximum during this injection time is especially advantageous.
The interval between the two charging phases A, B depends on the prevailing load state of the internal combustion engine 1. In idling operation, i.e., at minimal partial load, said distance is at its maximum. With an increase in load, in particular with an increase in rotational speed, the distance decreases. This is achieved by either shifting the closing point in time TS of the first charging phase A toward later or shifting the opening point in time TO of the second charging phase B toward early. Likewise, the distance between the two charging phases A and B can be reduced by shifting both the closing point in time TS of the first charging phase A in the direction of late and shifting the opening point in time TO of the second charging phase B in the direction of early. The injection times for the respective fuel injector 9 are then adapted accordingly, i.e., adjusted and/or shifted with respect to their position in time.
In certain operating states, it may be desirable to provide a third charging phase chronologically in time between the first charging phase A and the second charging phase B. Fundamentally, it is then also possible to allocate an injection operation to this third charging phase.
The controller 14 and/or the programs, algorithms and engine characteristics maps stored in it and other controllers optionally connected thereto represent the equipment that makes it possible to perform the operating method described above for the internal combustion engine 1. In particular, this equipment adjusts the chronological position of the injection time of the fuel as a function of the point in time of the change in the switch position of the respective clocked valve 13 and control the clocked valves 13 for the respective cylinder 5 for metering fresh gas.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 023 853.2 | May 2006 | DE | national |
