Method for Starting an Internal Combustion Engine of a Motor Vehicle

Abstract

A method for starting an internal combustion engine of a motor vehicle includes detecting before a direct starting of the internal combustion engine that a piston which is disposed translationally moveably in a start cylinder of the internal combustion engine is in an upper half of, or in a middle of, a stroke of the piston. In response to the detecting, rotating an output shaft of the internal combustion engine in a direction of rotation of the output shaft such that the piston is in a lower half of the stroke of the piston and in an intermediate position. The method further includes rotating the output shaft in a second direction of rotation before and/or during fuel being first directly injected into the start cylinder such that the piston is moved out of the intermediate position in a direction of an upper dead center of the piston.

Claims

1.-9. (canceled)

10. A method for starting an internal combustion engine (10) of a motor vehicle, comprising the steps of: detecting before a direct starting of the internal combustion engine (10), wherein an output shaft (14) of the internal combustion engine (10) rotates in a direction of rotation during fired operation for driving the motor vehicle and wherein a fuel is first directly injected into a start cylinder of the internal combustion engine in the direct starting, and while the output shaft (14) is stationary, that a piston which is disposed translationally moveably in the start cylinder is in an upper half of, or in a middle of, a stroke of the piston; rotating the output shaft (14) by an auxiliary drive device (26) in the direction of rotation in response to the detecting such that the piston is in a lower half of the stroke of the piston and in an intermediate position; and rotating the output shaft (14) by the auxiliary drive device (26) in a second direction of rotation that is opposed to the direction of rotation before and/or during the fuel being first directly injected into the start cylinder such that the piston is moved out of the intermediate position in a direction of an upper dead center of the piston.

11. The method according to claim 10, wherein the rotating of the output shaft (14) by the auxiliary drive device (26) in the direction of rotation is less than 360°.

12. The method according to claim 10, wherein the intermediate position is different from a position of a lower dead center of the piston.

13. The ethod according to claim 12, wherein a translational movement of the piston from the intermediate position into the position of the lower dead center of the piston results in a rotation of the output shaft (14) in the direction of rotation.

14. The method according to claim 10, wherein the rotating of the output shaft (14) by the auxiliary drive device (26) in the second direction of rotation is less than 360 °.

15. The method according to claim 10, wherein the auxiliary drive device (26) is an electric motor.

16. The method according to claim 10, wherein the output shaft (14) is rotated by the auxiliary drive device (26) depending on at least one rotational position of the output shaft (14) which is detected by a sensor (28).

Description

BRIEF DESCRIPTION OF THE DRAWING

[0021] The drawing shows a schematic side view of an internal combustion engine of a motor vehicle in the only FIGURE, the internal combustion engine of which is started by means of a method according to the invention.

DETAILED DESCRIPTION OF THE DRAWING

[0022] The one FIGURE shows an internal combustion engine 10 of a motor vehicle, formed as a reciprocating piston engine and also referred to as a combustion engine, motor or combustion motor, in a schematic side view. This means that the motor vehicle, preferably configured as a motor car, in particular as a passenger motor car, has the internal combustion engine 10 in its fully manufactured state and can be powered by means of the internal combustion engine 10. Therefore, the internal combustion engine 10 comprises a housing element 12 which can be a cylinder housing, in particular a cylinder crank housing. In addition, the internal combustion engine 10 comprises an output shaft 14 that is formed as a crankshaft, which is mounted on the housing element 12 rotatably around an axis of rotation 16 relative to the housing element 12. The housing element 12 has several cylinders, which each partially define a respective combustion chamber of the internal combustion engine 10. A respective piston is translationally moveably included in the respective cylinder. The internal combustion engine 10 also has a further housing element 19, for example formed as a cylinder head, which has or forms one combustion chamber roof per cylinder. The respective combustion chamber is thereby defined or formed in part by the respective cylinder, in part by the respective piston that is translationally moveably included in the respective cylinder, and in part by the associated combustion chamber roof.

[0023] The pistons included translationally moveably in the cylinders are pivotably connected to the output shaft 14 by respective connecting rods, so that the respective translational movement of the respective cylinder, which occurs relative to the housing element 12, can be or is converted into a rotation of the output shaft 14 that occurs around the axis of rotation 16, relative to the housing element 12. During fired operation, combustion processes occur in the respective combustion chamber and this in the respective cylinder, in each of which a mixture of fuel and air, also simply referred to as the mixture, is burnt. Exhaust gas results from this, which can flow out of the respective combustion chamber and flow into an exhaust system 18 or the internal combustion engine 10 and subsequently flow through the exhaust system 18.

[0024] The pistons are lubricated, for example by means of a lubricant, in particular by means of an oil, which can gather in an oil pan 20 of the internal combustion engine 10, in particular after the lubrication of the pistons. The internal combustion engine 10 here has a temperature sensor 22, also simply referred to as a sensor, by means of which a temperature of the lubricant, in particular in the oil pan 20, can be detected or is detected. An electronic computing device 24, also referred to as a control unit or engine control unit, is additionally provided, by means of which the internal combustion engine 10 is operated, in particular controlled or regulated.

[0025] Fired operation is configured to power the motor vehicle, since the internal combustion engine 10 provides at least one torque via the output shaft 14 during its fired operation, by means of which the motor vehicle can be or is driven. During the fired operation of the internal combustion engine 10, provided or configured to drive the motor vehicle, the output shaft 14 rotates around the axis of rotation 16 relative to the housing element 12 in a direction of rotation that is also referred to as the first direction of rotation or as the normal direction of rotation.

[0026] In the following, a method for starting the initially deactivated internal combustion engine 10 is described by means of the FIGURE. As is explained in even more detail, exactly one of the several cylinders of the internal combustion engine 10 is referred to as the start cylinder. In the method, the initially deactivated internal combustion engine 10 is started by direct starting. In direct starting, a fuel, for example a liquid or gaseous fuel, is first introduced into the start cylinder, out of all the cylinders of the internal combustion engine 10, and to this end is directly injected. Only after the injection of the fuel into the start cylinder is the fuel also introduced and thereby directly injected into the other cylinder or other cylinders of the internal combustion engine 10. It is preferably provided that, during direct starting, the fuel is injected into the start cylinder, while a rotation of the output shaft 14 in the direction of rotation is omitted. By means of a direct injection of the fuel into the start cylinder, which occurs in direct starting, a mixture of fuel and air is formed in the start cylinder, from the fuel injected into the start cylinder and from air that is in the start cylinder.

[0027] In order to now be able to carry out direct starting especially advantageously and reliably, it is determined whether, before the direct starting and while the output shaft is stationary, the piston arranged translationally moveably in the start cylinder is in the upper half or in the middle of its piston stroke, the initially stationary output shaft respectively rotated so far in the direction of rotation (normal direction of rotation) out of its standstill by means of an auxiliary drive device 26 that is provided in addition to the internal combustion engine and is, for example, formed as an electric motor, in such a way that, as a result of the rotation of the output shaft 14 effected by means of the auxiliary drive device 26 and occurring in the direction of rotation, the piston arranged in the start cylinder is in the lower half of its piston stroke, whereupon the fuel is first directly injected into the start cylinder to start the internal combustion engine 10. Because the pistons are pivotably connected with the output shaft 14 by the connecting rods, a rotation of the output shaft 14 occurring around the axis of rotation 16 relative to the housing element 12 leads to the pistons in the cylinders being translationally moved relative to the housing element. This is used in the method, in that the output shaft 14 is rotated by means of the auxiliary drive device 26 in such a way that the piston included in the start cylinder and also referred to as the start piston comes into an intermediate position which is between the lower dead center and the middle of the piston stroke of the start piston and this is preferably one of the positions of the start cylinder that is different from the lower dead center.

[0028] From the FIGURE it can be identified that the auxiliary drive device 26, also referred to as the auxiliary drive, is arranged on an in particular forward end of the output shaft 14. The auxiliary drive is dimensioned appropriately to rotate the output shaft 14 into a desired and, for example, specifiable or predetermined position. The position is also referred to as the rotational position or crankshaft angle and causes the start piston to be in the intermediate position as a result of the rotation of the output shaft 14 that occurs in the direction of rotation. A sensor 28, for example configured as a rotational angle senor, is provided here, by means of which an angular position and thus the rotational position of the output shaft 14 can be detected or is detected. The output shaft 14 is thereby powered by means of the auxiliary drive device 26 in accordance with the rotational position detected by means of the sensor 28, in particular in such a way that the auxiliary drive device 26 rotates the output shaft 14 in the direction of rotation around the axis of rotation 16 relative to the housing element 12 as long as the start piston is in the intermediate position or in the lower half of its piston stroke.

[0029] If, for example, the initially activated internal combustion engine 10 is deactivated, i.e., switched off, then the output shaft 14 runs out, which as part of its run-out or running out comes to a standstill. The powering down of the internal combustion engine 10, in particular the reaching of the standstill of the output shaft, is also referred to as an engine stop. For example, immediately after the engine stop, the sensor 28 detects or identifies a stopped position of the output shaft 14. Stopped position is to be understood as a rotational position of the output shaft 14, wherein the output shaft 14 occupies the stopped position at its standstill or is in the stopped position during its standstill. The sensor 28 provides, for example, a signal, in particular an electrical one, that characterizes the stopped position, which is received by the electronic computing device 24. Depending on the received signal and in particular depending on the detected or identified stopped position, the electronic computing device detects whether the start piston is in the upper half of its piston stroke. In other words, the electronic computing device 24 detects whether the stopped position leads to such a position of the start piston that the start piston is in the upper half of a piston stroke. If it is detected by means of the electronic computing device 24 that the start piston is in the upper half of its piston stroke, then the output shaft 14 is rotated further in the direction of rotation around the axis of rotation 16 relative to the housing element 12 by means of the auxiliary drive device 26, until the start piston is in the lower half of its piston stroke or until the start piston comes to rest or comes to a standstill in the lower half of its piston stroke. It is preferably provided that the start piston, after it has been moved into the lower half of its piston stroke by means of the rotation of the output shaft 14 that was effected by the auxiliary drive device 26, remains in the lower half of its piston stroke at least for a period of time and stays stationary, wherein the period of time is preferably at least 5 seconds, in particular at least 10 seconds and highly preferably at least 30 seconds or several minutes.

[0030] Because the start piston is in the lower half of its piston stroke, an especially large volume of the combustion chamber that is partially defined by the start cylinder can be implemented, so that an especially large volume of air or an especially large amount of air can be accommodated in the start cylinder. In this way, an especially large amount of the fuel can be directly injected into the start cylinder during direct starting, so that a reliable ignition and combustion in the start cylinder can be ensured. After the start piston has been moved into the lower half of its piston stroke, i.e., into the previously mentioned intermediate position, the output shaft 14 is for example rotated in a second direction of rotation, that is opposite to the direction of rotation, around the axis of rotation 16 relative to the housing element 12, by means of the auxiliary drive device 26, and is thus rotated back, wherein the start piston is moved out of its intermediate position in the direction of its upper dead center, while the injection of the fuel into the start cylinder as well as an ignition in the start cylinder is preferably omitted and while the start cylinder is free of fuel. Air accommodated in the start cylinder is hereby compressed, wherein after the compression and/or during the compression, i.e., after and/while the start piston is being moved out of the intermediate position in the direction of its upper dead center by means of the auxiliary drive, the fuel is directly injected into the start cylinder and is subsequently ignited in the start cylinder, whereby the internal combustion engine 10 is started by direct starting.

LIST OF REFERENCE CHARACTERS

[0031] 10 Internal combustion engine

[0032] 12 Housing element

[0033] 14 Output shaft

[0034] 16 Axis of rotation

[0035] 18 Exhaust system

[0036] 19 Housing element

[0037] 20 Oil pan

[0038] 22 Temperature sensor

[0039] 24 Electronic computing device

[0040] 26 Auxiliary drive device

[0041] 28 Sensor