Method for starting an internal combustion engine using a pinion starter and a starter-generator

Abstract

Method for starting an internal combustion engine (2) of an internal combustion engine (1) with • at least one combustion chamber (3) of the internal combustion engine (2), • a fuel supply device for introducing fuel into the at least one combustion chamber (3), • an output shaft (11) of the internal combustion engine (2), • a pinion starter (19) which can be coupled to the output shaft (11), and • a starter-generator (23) which is connected to the output shaft (11) for drive purposes, wherein • the output shaft (11) during a first start-up phase from a standstill by means of at least the pinion starter (19) until a transfer speed (n) is reached U ) is accelerated, • the output shaft during a second start-up phase, which follows the first start-up phase, exclusively by means of the starter-generator (23) until a start-up speed (n) is reached S), which is greater than the transfer speed (n U ) is and is at least 500 rpm, is accelerated and • only once the starting speed has been reached (n S ) Fuel is introduced into the at least one combustion chamber (3) to initiate self-running of the internal combustion engine.

Description

[0001] The invention relates to a method for starting an internal combustion engine of an internal combustion engine, in particular an internal combustion engine intended for driving a motor vehicle.

[0002] To start, an internal combustion engine usually requires the assistance of a starter, which accelerates an output shaft of the internal combustion engine until it reaches a minimum speed at which sufficient power can be generated for self-running through combustion processes in the combustion chamber(s) of the internal combustion engine.

[0003] Such a starter can be designed in the form of a so-called pinion starter. This comprises an electric motor with a gear that can be coupled, for starting purposes, to a gear that is non-rotatably connected to the output shaft of the internal combustion engine. Such coupling is often achieved by meshing the teeth of the pinion starter gear with the teeth of the output shaft gear. A pinion starter accelerates the output shaft of an internal combustion engine, such as one used to power a small (land) vehicle (car or small truck), typically to a speed of approximately 200 rpm. From this starting speed, fuel is then supplied to the combustion chamber(s) of the internal combustion engine and burned, thus causing the internal combustion engine to run independently.A further run-up of the internal combustion engine, starting from the starting speed up to a designated idle speed, which in the case of an internal combustion engine intended for driving a small (land) motor vehicle is usually between 700 rpm and 1000 rpm, is then carried out by the combustion processes in the internal combustion engine.

[0004] Particularly after a cold start of the combustion engine, such a run-up of the combustion engine can lead to relatively large raw pollutant emissions, whereby these raw pollutant emissions are also converted to a relatively small extent due to a correspondingly cold and thus ineffective exhaust gas aftertreatment device, which consequently leads to relatively large pollutant emissions into the environment.

[0005] An internal combustion engine, at least one designed to drive a motor vehicle, typically also includes a generator that is drivingly connected to the output shaft of the internal combustion engine. The generator converts the drive power of the internal combustion engine into electrical power, which is used to supply electrical consumers of the internal combustion engine and the motor vehicle as a whole.

[0006] It is known to implement the functions of both starter and generator using a single electric machine. Such an electric machine is called a starter-generator. A common design of such a starter-generator provides a drive connection between the output shaft of the internal combustion engine and the rotor of the starter-generator using a traction device, often in the form of a V-ribbed belt. In addition to functional integration, one advantage of a starter-generator is a relatively fast starting process with relatively low noise emissions, because this does not require the engagement of two gears, as is the case with a pinion starter. A starter-generator also offers advantages in implementing an automatic start-stop function for the internal combustion engine, because it allows the internal combustion engine to be restarted even when the internal combustion engine is being trailed with a rotating output shaft.

[0007] Due to its design, a starter-generator may not be able to transfer sufficient torque to the output shaft of the internal combustion engine during a cold start, especially at temperatures well below freezing, to ensure reliable starting of the internal combustion engine. In particular, a belt coupling the starter-generator to the internal combustion engine can limit the transmission of sufficiently high torque. In such a case, a pinion starter and a starter-generator can be used in combination. Such combinations are known from DE 10 2017 214 041 A1 and DE 10 2015 215 550 A1.

[0008] In this regard, DE 10 2017 214 041 A1 discloses using the pinion starter to overcome the breakaway torque of the internal combustion engine in a first starting phase. In a transition phase, the output shaft of the internal combustion engine can then be rotated by both the pinion starter and the starter-generator. In a second starting phase, which extends until the initiation of combustion processes in the internal combustion engine, the output shaft of the internal combustion engine is rotated exclusively by the starter-generator.

[0009] The invention is based on the object of minimizing the pollutant emissions of an internal combustion engine as well as the entry of fuel into engine oil via the combustion chamber walls of the internal combustion engine of the internal combustion engine immediately after a start, in particular a cold start.

[0010] This object is achieved by implementing a method according to patent claim 1. Advantageous embodiments of such a method are the subject matter of the further patent claims and emerge from the following description of the invention.

[0011] According to the invention, a method for starting an internal combustion engine of an internal combustion engine is provided, wherein the internal combustion engine comprises at least one combustion chamber, preferably a plurality of combustion chambers, of the internal combustion engine, a fuel supply device for introducing fuel into the at least one combustion chamber, an output shaft of the internal combustion engine, an electromotive pinion starter that can be coupled to the output shaft and thus, as needed, temporarily brought into a drive connection with the output shaft, and a starter-generator configured as an electric machine that is drive-connected to the output shaft of the internal combustion engine at least permanently during the entire starting process. The drive connection of the starter-generator to the output shaft of the internal combustion engine can be permanent or non-coupleable, or can also be coupled.The starter-generator is an electric machine designed for both motor and generator operation. In motor operation, power is output and thus the output shaft of the combustion engine is driven by the starter-generator. In generator operation, power is input and thus the starter-generator is driven by the output shaft of the combustion engine. Generator operation generates electrical power by converting mechanical power, which is tapped at the output shaft of the combustion engine.

[0012] During a first starting phase, starting from a standstill of the output shaft, the output shaft is accelerated by at least the pinion starter until a transfer speed is reached. During a second starting phase, which follows the first starting phase, the output shaft is then accelerated exclusively by the starter generator until a starting speed is reached that is greater than the transfer speed and is at least 500 rpm, preferably at least 700 rpm, particularly preferably at least 800 rpm or at least 1000 rpm. Only when the starting speed is reached is fuel introduced into the at least one combustion chamber in order to initiate self-running of the internal combustion engine, during which the fuel is burned in the at least one combustion chamber.

[0013] According to the invention, the output shaft of the internal combustion engine is accelerated to a relatively high speed by introducing fuel into the at least one combustion chamber before initiating self-running. The correspondingly high number of compression cycles carried out in the at least one combustion chamber before the fuel is introduced leads to a relatively extensive preheating of the at least one combustion chamber and thus to improved conversion of the subsequently introduced fuel. This, in turn, leads to an improvement in the raw pollutant emissions of the internal combustion engine. The unwanted ingress of fuel, which has condensed on the walls of the at least one combustion chamber, into the lubricant of the internal combustion engine can also be minimized by reducing such condensation.Since in the compression cycles air in the at least one combustion chamber is highly compressed and thus heated, wherein this air is subsequently expelled into an exhaust system of the internal combustion engine, a relatively extensive preheating of an exhaust gas aftertreatment device integrated into the exhaust system of the internal combustion engine can also be achieved until the start of the self-running of the internal combustion engine, so that according to the invention not only a reduction of the pollutant raw emissions can be achieved, but also a reduced heat-up time for the exhaust gas aftertreatment device, based on the start of the self-running of the internal combustion engine, until a conversion of these pollutant raw emissions begins.

[0014] Accelerating the output shaft of the internal combustion engine (at least also) by means of the pinion starter during the first starting phase and exclusively by means of the starter-generator during the second starting phase takes into account the respective functional advantages of these two types of starters. One such advantage with a pinion starter is, in particular, the generation of a sufficiently high torque (at the output shaft of the internal combustion engine), which ensures reliable starting of the internal combustion engine even during a cold start. The starter-generator may not be able to provide a sufficiently high torque at the output shaft of the internal combustion engine for this purpose. This applies at least if a technically relatively simple and thus cost-effective design of the starter-generator is possible, in particular one in which the starter-generator is driven by a traction device (e.g.a belt, in particular a V-belt) is drivingly connected to the output shaft. Despite such a simple design, the starter-generator, however, can enable acceleration of the output shaft up to the relatively high starting speed provided by the invention, something for which the pinion starter cannot be designed in a conventional, technically relatively simple and thus cost-effective design. The method according to the invention therefore advantageously achieves the relatively low pollutant raw emissions of the internal combustion engine and thus also the pollutant emissions of the internal combustion engine.

[0015] Starting the internal combustion engine by initially accelerating the output shaft (at least also) using the pinion starter can, as described, be particularly advantageous if the starter-generator may not be able to provide a sufficiently high torque at the output shaft of the internal combustion engine for a cold start of the internal combustion engine. At the same time, the torque provided by the starter-generator at the output shaft can be sufficient for a reliable warm start of the internal combustion engine, so that the advantages, particularly with regard to noise emissions and starting time, that can be realized by starting using only the starter-generator can be advantageously utilized for such a warm start of the internal combustion engine.Accordingly, it can be provided that during a cold start of the internal combustion engine, in which at least one temperature of the internal combustion engine is below a limit value, the starting of the internal combustion engine is carried out as described by a combined use of the pinion starter and the starter generator, whereas during a warm start, in which at least one temperature of the internal combustion engine is above the limit value, rotation of the output shaft, starting from a standstill until a starting speed is reached, is carried out exclusively by means of the starter generator, wherein only when the starting speed is reached is fuel introduced into the at least one combustion chamber in order to initiate the self-running of the internal combustion engine. The starting speed during the warm start can essentially correspond to the starting speed during the cold start (deviation of a maximum of ± 25 rpm) or can be lower or higher than the starting speed during the cold start.

[0016] The at least one temperature can, for example, be a temperature of a coolant that is determined (in particular measured) at a point in a cooling circuit (e.g., at an inlet of a cooling channel of the internal combustion engine). The at least one temperature can also be a temperature of a lubricant used to lubricate at least the internal combustion engine. The limit temperature can, for example, correspond to a value between 15°C and 25°C, in particular 20°C. However, the limit temperature can also be selected to be lower, in particular 0°C or even lower.

[0017] Preferably, it can be provided that the starting speed corresponds at most to a starting idle speed of the internal combustion engine (e.g. 1000 rpm or 1100 rpm). Acceleration of the output shaft by means of the starter generator to unnecessarily high speeds can be avoided. The “starting idle speed” is understood to be a defined idle speed of the internal combustion engine, which should be established during self-running immediately after the internal combustion engine has started. The starting idle speed can also be variable and, in particular, depend on the temperature of the internal combustion engine. The starting idle speed can be higher at a relatively low internal combustion engine temperature than at a relatively high internal combustion engine temperature.

[0018] The relatively long period of time required to accelerate the output shaft of the internal combustion engine to the relatively high starting speed can be advantageously used to increase the fuel pressure in the fuel supply device and / or the fresh gas pressure in a fresh gas line of the internal combustion engine to a relatively large extent, in order to achieve the most advantageous operation of the internal combustion engine immediately upon the start of self-running. Such an increase in the fuel pressure and / or such an increase in the fresh gas pressure can be provided during the first starting phase and / or during the second starting phase.An increase in fuel pressure can be achieved by appropriately operating a fuel pump of the fuel supply device. An advantageous, relatively high fuel pressure at the beginning of the internal combustion engine's self-running operation can be achieved simply by operating the fuel pump for a correspondingly long time due to the relatively long acceleration of the output shaft by means of the starter motor. The same can apply to an increase in fresh gas pressure, whereby a charging device, for example an exhaust gas turbocharger, can be operated for this purpose. Such a charging device can also be actively driven, in particular by an electric motor.

[0019] During the initial starting phase, the engine's output shaft can only be accelerated using the pinion starter. Accelerating the output shaft simultaneously using both the pinion starter and the starter-generator is not possible in this case.

[0020] However, it can also be advantageous if the output shaft is accelerated at least temporarily by the pinion starter and the starter-generator during the first starting phase. For this purpose, it can be provided that acceleration by the pinion starter and the starter-generator is only provided during a portion of the first starting phase, which in particular extends until the end of the first starting phase. This allows for the most smooth transition possible from acceleration solely by the pinion starter during a preceding portion of the first starting phase to further acceleration solely by the starter-generator during the second starting phase.

[0021] Alternatively, it can be provided that during the first starting phase, the output shaft is always accelerated by means of the pinion starter and the starter generator, which can in particular make it possible to design the pinion starter with relatively low power and thus cost-effective.

[0022] The combustion engine of an internal combustion engine according to the invention can be, for example, a (self-igniting and quality-controlled) diesel engine or a (spark-ignition and quantity-controlled) gasoline engine, or a combination thereof, e.g., a homogeneous compression ignition engine. The combustion engine can be operated with liquid fuel (e.g., diesel or gasoline) and / or with a gaseous fuel (in particular, natural gas, LNG, or LPG).

[0023] The invention also relates to a control device with a memory, wherein a computer program is stored in the memory, during the execution of which a method according to the invention can be carried out.

[0024] The invention also relates to a computer program with a program code for executing a method according to the invention when the computer program is executed on a computer.

[0025] An internal combustion engine to be started according to the invention and the internal combustion engine comprising it can in particular be part of a motor vehicle, in particular a wheel-based and non-rail-bound motor vehicle (preferably a car or a truck).

[0026] The method according to the invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings. The drawings show, partly in simplified form: Fig. 1: a motor vehicle with an internal combustion engine comprising an internal combustion engine that can be started according to a method according to the invention; Fig. 2: starting the internal combustion engine according to a first embodiment; Fig. 3: starting the internal combustion engine according to a second embodiment; Fig. 4: starting the internal combustion engine according to a third embodiment; and Fig. 5: starting the internal combustion engine according to a fourth embodiment.

[0027] The Fig. 1 shows a motor vehicle with an internal combustion engine 1. The internal combustion engine 1 comprises an internal combustion engine 2, which can in principle be designed in any known manner, but preferably as a reciprocating piston engine, in particular as a four-stroke reciprocating piston engine. To carry out combustion processes in at least one combustion chamber 3 of the internal combustion engine 2, fresh gas, which can consist at least partially of ambient air, can be supplied to it via a fresh gas line 4. Exhaust gas produced during the combustion of the fresh gas together with fuel in the at least one combustion chamber 3 is discharged into the environment via an exhaust line 5. An exhaust gas aftertreatment device 6 with at least one exhaust gas aftertreatment unit is integrated into the exhaust line 5 in order to remove pollutants from the exhaust gas and / or convert them into harmless components.The fuel can be supplied to the at least one combustion chamber 3 by means of a fuel supply device, which can comprise, for example, a fuel tank 7, a fuel pump 8, a fuel collecting line 9 and a fuel injector 10 (per combustion chamber 3) for introducing the fuel directly into the at least one combustion chamber 3.

[0028] The internal combustion engine 2 further comprises an output shaft 11, which, if the internal combustion engine 2 is configured as a reciprocating piston engine, may be a crankshaft. The output shaft 11 can be coupled to an input shaft 14 of a manual transmission 13 via a clutch 12. An output shaft 15 of the manual transmission is connected to drive shafts 16 of wheels 17 of the motor vehicle.

[0029] The output shaft 11 of the internal combustion engine 2 is further connected in a rotationally fixed manner to a gear 18. A gear 20 of a pinion starter 19 can be meshed into this gear 18. The pinion starter 19 has a corresponding meshing system (not shown) for this purpose, by means of which at least the gear 20 of the pinion starter 19 can be displaced in the longitudinal axial direction. The pinion starter 19 further comprises an electric motor 21 for rotating the gear 20 of the pinion starter 19.

[0030] The output shaft 11 of the internal combustion engine 2 is further permanently connected via a traction means 22 to a starter generator 23, which comprises an electric machine 24 which can be operated as a motor and as a generator.

[0031] At least the fuel pump 8, the pinion starter 19, and the starter-generator 23 can be controlled by a control device 27. This device includes a memory 28 in which a computer program for controlling at least these components is stored.

[0032] For starting the internal combustion engine 2 from a non-operation with a stationary output shaft 11, it is provided that the output shaft 11 is rotated during a first starting phase from the standstill by means of at least the pinion starter 19 until a transfer speed n U to accelerate. A further acceleration of the output shaft 11 until a starting speed n is reached S During a second starting phase, however, the engine is driven exclusively by the starter generator 23. When the starting speed n SThe introduction of fuel into at least one combustion chamber 3 of the internal combustion engine 2 begins, and this fuel is converted within the framework of combustion processes in order to cause the internal combustion engine 2 to run automatically. As soon as such automatic operation of the internal combustion engine 2 is ensured, the operation of the starter-generator 23 is also terminated.

[0033] The Fig. 2 to 5 show various possibilities for such a combined use of the pinion starter 19 and the starter-generator 23 for starting the internal combustion engine 2. In each case, the bar 25 shows the use of the pinion starter 19 and the bar 26 shows the use of the starter-generator 23.

[0034] According to the Fig. 2, it may be provided to accelerate the output shaft 11 of the internal combustion engine 2 during the first starting phase exclusively by means of the pinion starter 19. Its operation is terminated with the activation of the starter-generator 23 (in its function as a starter). The transfer speed n U can, as shown, a maximum speed n Rmax the output shaft (e.g. approx. 200 rpm), which can be realized by means of the pinion starter 19 and / or which is permissible for the pinion starter 19.

[0035] According to the Fig. 3 to 5, it can also be provided that the starter generator 23 is used in addition to the pinion starter 19 during the first starting phase. Fig. 3 and Fig. 4, it is provided that the starter generator 23 is operated only in a second section of the first starting phase, while in a first section of the first starting phase, the acceleration of the output shaft 11 of the internal combustion engine 2 is effected exclusively by means of the pinion starter 19. The embodiments according to the Fig. 3 and Fig. 4 differ in that according to the Fig. 3 the transfer speed n U the maximum speed n Rmax while the transfer speed n U in the embodiment according to the Fig. 4 less than this maximum speed n Rmax is.

[0036] According to the Fig. 5, it can also be provided that the starter generator 23 is operated together with the pinion starter 19 during the entire first starting phase. In this case, the transfer speed n U , as shown, again the maximum speed n RmaxHowever, this may also be lower.

[0037] When using only the pinion starter 19 during the first starting phase according to the Fig. 2, the transfer speed n U also lower than the maximum speed n Rmax be.

[0038] Starting the internal combustion engine 2 using both the pinion starter 19 and the starter generator 23 according to, for example, the Fig. 2 to 5 can be provided only for a cold start of the internal combustion engine 2, in which the temperature of the internal combustion engine 1 is below a limit value. For a warm start, in which this temperature is above this limit value, however, the internal combustion engine 2 can be started exclusively by means of the starter-generator 23. List of reference symbols 1 internal combustion engine 2 combustion engine 3 combustion chamber 4 Fresh gas line 5 Exhaust system 6 Exhaust aftertreatment device 7 Fuel tank 8 Fuel pump 9 Fuel manifold 10 Fuel injector 11 Output shaft of the combustion engine 12 Clutch 13 manual transmissions 14 Input shaft of the manual transmission 15 Output shaft of the manual transmission 16 Drive shaft 17 wheels 18 Output shaft gear 19 pinion starter 20 Pinion starter gear 21 Electric motor of the pinion starter 22 traction devices 23 Starter generator 24 Electric machine of the starter generator 25 Using the pinion starter 26 Using the starter generator 27 Control device 28 Control device memory n Speed ​​of the output shaft n U Transfer speed nRmax Maximum speed n S Starting speed QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2017 214 041 A1 [0007, 0008] DE 10 2015 215 550 A1

[0007]

Claims

[1] Method for starting an internal combustion engine (2) of an internal combustion engine (1) with • at least one combustion chamber (3) of the internal combustion engine (2), • a fuel supply device for introducing fuel into the at least one combustion chamber (3), • an output shaft (11) of the combustion engine (2), • a pinion starter (19) which can be coupled to the output shaft (11), and • a starter generator (23) which is drivingly connected to the output shaft (11), wherein • the output shaft (11) during a first starting phase starting from a standstill by means of at least the pinion starter (19) until a transfer speed (n U ) is accelerated, • the output shaft (11) during a second starting phase, which follows the first starting phase, is rotated exclusively by means of the starter generator (23) until a starting speed (n S) which is greater than the transfer speed (n U ) and which is at least 500 rpm, is accelerated and • only when the starting speed (n S ) Fuel is introduced into the at least one combustion chamber (3) in order to initiate self-running of the internal combustion engine (2). [2] Method according to claim 1, characterized by that the starting speed (n S ) corresponds to a maximum starting idle speed of the combustion engine (2). [3] Method according to claim 1 or 2, characterized by that the output shaft (11) is accelerated at least temporarily by the pinion starter (19) and the starter generator (23) during the first starting phase. [4] Method according to one of the preceding claims, characterized bythat during the first starting phase and / or the second starting phase, an increase in a fuel pressure in the fuel supply device and / or an increase in a fresh gas pressure in a fresh gas line (4) of the internal combustion engine (1) is carried out. [5] Method for starting an internal combustion engine (2) of an internal combustion engine (1) with • at least one combustion chamber (3) of the internal combustion engine (2), • a fuel supply device for introducing fuel into the at least one combustion chamber (3), • an output shaft (11) of the combustion engine (2), • a pinion starter (19) which can be coupled to the output shaft (11), and • a starter generator (23) which is drive-connected to the output shaft (11), characterized by , that • for a cold start in which a temperature of the internal combustion engine (1) is below a limit value, the starting of the internal combustion engine (2) is carried out according to one of the preceding claims and • for a warm start, in which the temperature of the internal combustion engine is above the limit value, an acceleration of the output shaft (11) starting from a standstill until a starting speed is reached is carried out exclusively by means of the starter generator (23), wherein only when this starting speed is reached is fuel introduced into the at least one combustion chamber (3) in order to initiate self-running of the internal combustion engine (2). [6] Method according to claim 5, characterized by that the starting speed during the warm start of the starting speed (n S ) during the cold start. [7] Method according to claim 5, characterized bythat the starting speed during the warm start is lower or higher than the starting speed (nS) during the cold start. [8] Method according to one of the preceding claims, characterized by that the starter generator (23) is drive-connected to the output shaft (11) via a traction means (22). [9] Control device (27) with a memory (28), wherein a computer program is stored in the memory (28), during the execution of which a method according to one of the preceding claims can be carried out. [10] Computer program with a program code for carrying out a method according to one of claims 1 to 8 when the computer program is executed on a computer.

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