Method for Starting an Internal Combustion Engine

Abstract

A method for starting or stopping an internal combustion engine which reduces starter loading and engine vibrations is provided. The method includes varying a valve stroke of at least one cylinder of the engine such that during the starting or stopping procedure the at least one cylinder undergoes decompression.

Claims

1. A method for starting or stopping an internal combustion engine, comprising the acts of: initiating a starting operation or a stopping operation, varying a valve stroke of an intake valve of at least one cylinder of the internal combustion engine such that the at least one cylinder is placed in a decompression state in which a reduced pressure is achieved relative to a pressure that would be present in the at least one cylinder when the valve stroke of the intake valve is a full valve stroke.

2. The method as claimed in claim 1, wherein the intake valve is closed before a piston assigned to the at least one cylinder reaches a bottom dead center.

3. The method as claimed in claim 1, wherein a decompression level is individually set for each of the at least one cylinders of the internal combustion engine.

4. The method as claimed in claim 1, wherein the valve stroke is between 0 mm and 2 mm.

5. The method as claimed in claim 1, wherein the valve stroke is between 0 mm and 1 mm.

6. The method as claimed in claim 1, wherein the varying of the valve stroke to obtain the decompression state is performed by setting a camshaft of the internal combustion engine in the direction of advanced intake spreads.

7. The method as claimed in claim 1, wherein the decompression state is obtained by setting the valve stroke to be a zero stroke in which the intake valve remains closed.

8. The method as claimed in claim 7, wherein a filling level of the at least one cylinder is set by positioning a crankshaft of the internal combustion engine in a predefined stationary position.

9. The method as claimed in claim 8, wherein the predefined stationary position of the crankshaft is set by at least one of a starter and an electric machine.

10. The method as claimed in claim, wherein all of the at least one cylinder are decompressed when the internal combustion engine is started.

11. The method as claimed in claim, wherein the varying the valve stroke of the inlet valve to obtain the decompression state of the at least one cylinder of the internal combustion engine is performed is obtained by varying the valve stroke of the inlet valve during an overrun operation.

12. The method as claimed in claim 1, wherein the varying of the valve stroke is based on at least one of a surrounding temperature and an operating temperature of the internal combustion engine.

13. A computer program product comprising: machine-readable code contained on a tangible medium, the machine-readable code being configured to be executable on a computer device to initiate a starting operation or a stopping operation, vary a valve stroke of an intake valve of at least one cylinder of the internal combustion engine such that the at least one cylinder is placed in a decompression state in which a reduced pressure is achieved relative to a pressure that would be present in the at least one cylinder when the valve stroke of the intake valve is a full valve stroke.

14. A control device for an internal combustion engine, comprising: a computer configured to initiate a starting operation or a stopping operation, vary a valve stroke of an intake valve of at least one cylinder of the internal combustion engine such that the at least one cylinder is placed in a decompression state in which a reduced pressure is achieved relative to a pressure that would be present in the at least one cylinder when the valve stroke of the intake valve is a full valve stroke.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0021] FIG. 1 shows a schematic illustration of an internal combustion engine which can be started by a method according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWING

[0022] FIG. 1 shows an internal combustion engine 1. The internal combustion engine 1 comprises a cylinder 4 in which a piston 3 can be moved. An intake valve 5 of the internal combustion engine 1 can be activated via a camshaft 2.

[0023] There is provision that all the cylinders 4 of the internal combustion engine 1 are decompressed if the internal combustion engine 1 is started. The decompression, in particular a level of the decompression, can be set to different degrees for this purpose. Thus, there is provision in particular that the inlet valve 5 is activated by a variable valve control mechanism in such a way that a valve stroke is set between 0 mm and 2 mm, preferably between 0 mm and 1 mm. Alternatively or in addition, there is provision that the camshaft 2 is adjusted in the direction of advanced intake spreads by a camshaft adjustment system, in particular by phase adjusters. In this way, the intake valve 5 closes before the piston 3 reaches a bottom dead center.

[0024] The decompression of the cylinder 4 ensures that the piston 3 has to perform only a small amount of compression work if it is moved from the bottom dead center to the top dead center in the compression cycle. In this way, a vibrational behavior and a noise emission of the internal combustion engine 1 during the starting operation is optimized, with at the same time a starter mechanism of the internal combustion engine 1 being relieved.

[0025] Furthermore, it is advantageous for a decompression to be present by setting a zero stroke of the intake valve 5. For this purpose, there is advantageously provision that the internal combustion engine 1 is shut off in a targeted manner. A crankshaft (not shown) of the internal combustion engine 1 has a predefined position due to a targeted shut-off. In the predefined position, a filling level of each cylinder 4 of the internal combustion engine 1 is predefined. Thus, it is possible by selecting the predefined position to determine which cylinder 4 is intended to have which filling level. If a filling level is selected in which the piston 3 is not situated at its bottom dead center, the filling level of the cylinder 4 is smaller than a maximum filling level. The maximum filling level corresponds to that volume which the cylinder 4 has if the piston 3 has arrived at the bottom dead center. A decompression of the cylinder 4 is present due to the smaller filling level. Thus, the piston 3 has to perform only a small amount of compression work if it is moved in the compression cycle from the bottom dead center to the top dead center.

[0026] At the end of the starting operation there is advantageously provision that the valve stroke of the intake valve 5 is increased in order to change to a conventional operation of the internal combustion engine 1. In addition, during the starting operation there is preferably provision that a valve stroke of the intake valve 5 and an adjustment of the camshaft 2 is undertaken on the basis of surrounding conditions, in particular on the basis of a surrounding temperature, and/or on the basis of an operating temperature of the internal combustion engine 1.

[0027] The above-described possibility of decompressing the cylinder 4 is advantageous not only in the case of a starting operation of the internal combustion engine 1. The decompression as described above can also occur if the internal combustion engine 1 is intended to be stopped. If the internal combustion engine 1 is used in a vehicle as a drive, it may be required, in particular in the case of hybrid vehicles, that an alternative drive is intended to move the vehicle. If it is intended in this case for the internal combustion engine 1 to be further rotated, a decompression of the cylinder 4, preferably of all the cylinders 4 of the internal combustion engine 1, is advantageously provided in order thereby to relieve the alternative drive.

[0028] If the internal combustion engine is started with the described decompressed cylinders 4, there results an advantage in respect of vibrational comfort and acoustics and a reduction in a power requirement to the starter system.

[0029] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

LIST OF REFERENCE SIGNS

[0030] 1 Internal combustion engine [0031] 2 Camshaft [0032] 3 Piston [0033] 4 Cylinder [0034] 5 Intake valve