Method for operating an internal combustion engine of a hybrid vehicle during a starting process

Description

[0001] The invention relates to a method for operating an internal combustion engine of a motor vehicle, in particular a hybrid vehicle, during a starting process of the internal combustion engine, in particular during a starting process from a standstill of the internal combustion engine to high torques. Furthermore, the invention relates to an engine control system for implementing the method according to the invention and to a motor vehicle with such an engine control system.

[0002] Hybrid vehicles typically have an internal combustion engine and an electric motor, each of which provides a drive torque as a proportion of the total torque. As described in DE 10 2007 055 740 A1 and DE 10 2013 004 033 A1, the individual torques of the internal combustion engine and the electric motor are coordinated.

[0003] In a vehicle with a parallel hybrid powertrain featuring a separating clutch between the internal combustion engine and the rest of the powertrain, a driver request may cause the internal combustion engine to operate immediately at high load. Due to a lack of lubrication or a delayed oil pressure buildup, the immediate load demand can lead to component damage to bearings, such as the crankshaft, connecting rods, or the turbocharging system due to solid or mixed lubrication.

[0004] To reduce such wear, the internal combustion engine can be lubricated (started) during electrical operation to fill the oil gallery or supply the internal combustion engine components with oil. However, there are situations in which lubrication of the internal combustion engine is not possible due to driving conditions. This can still lead to potential damage to the internal combustion engine.

[0005] DE 10 2011 005 803 A1 describes a method for operating a hybrid vehicle, wherein an internal combustion engine is only switched on if a requested desired torque is at least a difference higher than a maximum torque achievable by an electric motor.

[0006] DE 10 2012 009 481 A1 describes a method for controlling the connection of an internal combustion engine of a hybrid drive unit, wherein the internal combustion engine is operated in a first phase after starting at a torque which is reduced compared to a target torque and the torque is then increased to the target torque in a second phase as soon as an engine temperature has reached a predetermined temperature.

[0007] US 2012 / 067327 A1 describes a method in which a maximum torque is determined depending on engine temperature and engine speed. In addition, the maximum torque can depend on a pressure ratio between the air supply and the exhaust tract.

[0008] DE 10 2011 078 446 A1 describes a method in which a maximum torque during a cold start is determined depending on ambient conditions, for example an ambient temperature.

[0009] US 2011 / 0146622 A1 discloses a method for limiting a torque as a function of an engine temperature, a time since exceeding an engine speed or a time since exceeding an engine speed and an engine pressure.

[0010] However, the provision of a reduced torque by the internal combustion engine can lead to undesirable losses in driving comfort, as the desired torque cannot be provided immediately.

[0011] The object of the present invention is to provide a method and an engine control for operating an internal combustion engine of a motor vehicle during a starting process of the internal combustion engine, which at least partially overcome the above-mentioned disadvantages.

[0012] This object is achieved by the method according to the invention for operating an internal combustion engine of a motor vehicle during a starting process of the internal combustion engine according to claim 1 and the engine control according to the invention according to claim 6.

[0013] According to a first aspect, the invention relates to a method for operating an internal combustion engine of a motor vehicle during a starting process of the internal combustion engine, comprising: Obtaining a lubrication state variable that represents a lubrication state of the internal combustion engine; determining a maximum permissible torque of the internal combustion engine depending on the lubrication state variable; and operating the internal combustion engine at an operating torque that is equal to or less than the determined maximum permissible torque.

[0014] According to a second aspect, the invention relates to an engine control for operating an internal combustion engine of a motor vehicle during a starting process of the internal combustion engine, which is designed to carry out a method according to the first aspect.

[0015] Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred embodiments of the present invention.

[0016] The present invention relates to a method for operating an internal combustion engine of a motor vehicle during a starting process of the internal combustion engine, in particular during a starting process of the internal combustion engine from a standstill to high torques, preferably maximum torques. Such a starting process is also referred to as a critical start of the internal combustion engine. The method according to the invention is thus used when the internal combustion engine is operated directly at high load from a standstill.

[0017] In a hybrid vehicle with an electric drive motor and the internal combustion engine, which may be, for example, a gasoline engine or a diesel engine, the starting process can be a start of the internal combustion engine from a purely electric operating mode of the hybrid vehicle and / or a start during a hybrid operating mode of the hybrid vehicle. Alternatively or additionally, the starting process can be a start during coasting operation of the hybrid vehicle. In a vehicle with the internal combustion engine, for example, a gasoline engine or a diesel engine, as the sole drive element, the starting process can be a start during coasting operation of the vehicle.

[0018] According to the method according to the invention, a lubrication state variable is obtained that represents a lubrication state of the internal combustion engine. The lubrication state of the internal combustion engine can be a distribution of a lubricant, for example, engine oil, on one or more components of the internal combustion engine that are subject to a frictional force. The components of the internal combustion engine include, for example, one or more components of a crankshaft drive, such as a crankshaft, connecting rods (pistons), connecting rods, and / or the like, and / or one or more components of a charging system, such as an exhaust gas turbocharger, an exhaust flap, and / or the like.

[0019] The lubrication state variable can, for example, be detected by a sensor or generated and provided by an analysis unit, for example in the form of a processor, using one or more models, and then received, in particular, by an engine control unit. Examples of the lubrication state variable are listed and explained below.

[0020] Furthermore, according to the method according to the invention, a maximum permissible torque of the internal combustion engine (maximum permissible internal combustion engine torque) is determined depending on the obtained lubrication state variable. The maximum permissible torque is a torque limit dependent on the lubrication state variable. If exceeded, mixed friction occurs on the components of the internal combustion engine, leading to undesirable wear.

[0021] The maximum permissible torque can, for example, be determined using models and stored as a characteristic curve or map and / or calculated mathematically. Details on determining the maximum permissible torque are described in more detail below.

[0022] Subsequently, according to the method according to the invention, the internal combustion engine is operated, in particular started and operated, at an operating torque that corresponds to or is less than the determined maximum permissible torque.

[0023] By operating the internal combustion engine during the start-up process below full load, i.e., below the maximum possible torque or maximum available torque, lubrication can be initiated, reducing or preventing mixed friction and predominantly achieving the desired sliding friction. This provides the necessary protection for the internal combustion engine to prevent damage to the internal combustion engine or to an engine and engine components.

[0024] In some embodiments, the lubrication state variable may include a lubricant temperature of a lubricant in the internal combustion engine, a lubricant pressure of the lubricant in the internal combustion engine, a time after the end of a standstill of the internal combustion engine, a coolant temperature of the internal combustion engine, a coolant pressure of the internal combustion engine, a number of combustions and / or crankshaft revolutions since the end of the standstill of the internal combustion engine, a duration of a previous standstill of the internal combustion engine, a duration since a previous lubrication process of the internal combustion engine, a duration of a previous operation of the internal combustion engine, a duration of a previous lubrication process of the internal combustion engine, a property of a previous lubrication process and / or another lubrication state variable.

[0025] The lubricant temperature can be a temperature of the lubricant in a lubricant circuit of the internal combustion engine, for example, an oil temperature in an oil gallery or in an oil line of the lubricant circuit. The lubricant temperature can be detected by a temperature sensor in the lubricant circuit, for example, in the oil gallery or in the oil line, and / or provided by a model, in particular a lubricant temperature model. Accordingly, the lubricant pressure of the lubricant can be a pressure of the lubricant in the lubricant circuit and detected by a pressure sensor in the lubricant circuit and / or provided by a model, in particular a lubricant pressure model.

[0026] The coolant temperature of the internal combustion engine can be a temperature of a coolant, for example, cooling water, in a cooling circuit of the internal combustion engine and can be detected by a temperature sensor arranged in the cooling circuit and / or provided by a model, in particular a coolant temperature model. Accordingly, the coolant pressure of the coolant can be a pressure of the coolant in the cooling circuit and can be detected by a pressure sensor in the cooling circuit and / or provided by a model, in particular a coolant pressure model.

[0027] The time after the end of the standstill of the internal combustion engine, ie since the start of the starting process of the internal combustion engine, and / or the number of combustions and / or crankshaft revolutions since the end of the standstill of the internal combustion engine, ie since the start of the starting process of the internal combustion engine, can be derived, for example, from a signal of a crankshaft sensor.

[0028] The duration of the previous standstill of the internal combustion engine, for example a shutdown duration of the internal combustion engine, the duration since the previous lubrication process of the internal combustion engine, the duration of the previous operation of the internal combustion engine, the duration of the previous lubrication process of the internal combustion engine, ie a previous combustion runtime, can be recorded by means of time measurement, for example triggered by a stored crankshaft signal of a crankshaft sensor.

[0029] The property of the previous lubrication process may include, for example, a lubricant and / or coolant temperature or a lubricant and / or coolant pressure, a number of combustions and / or crankshaft revolutions during the previous lubrication process and / or another property.

[0030] In some embodiments, the maximum permissible torque of the internal combustion engine can increase with an increase in the lubrication state variable during the starting process of the internal combustion engine. The maximum permissible torque can preferably increase continuously, for example, linearly, quadratically, or exponentially. Thus, in situations in which a critical start-up of the internal combustion engine occurs, i.e., a start from standstill at high torques, the maximum permissible torque is limited and subsequently ramped or increased to a maximum available torque.

[0031] For example, a maximum permissible base torque value can be determined based on the lubricant temperature. Based on the maximum permissible base torque value, a maximum limited permissible torque can then increase with increasing time after the combustion engine starts. Depending on the relationship between the lubricant temperature and the coolant temperature, the maximum limited permissible base torque value can be adjusted. Additionally or alternatively, the maximum permissible torque can be increased to the maximum available torque after a specified number of combustion cycles since start-up.

[0032] In some embodiments, a maximum permissible base torque can be determined depending on the time after the end of the standstill of the internal combustion engine and depending on the lubricant temperature of the lubricant in the internal combustion engine or the lubricant pressure of the lubricant in the internal combustion engine.

[0033] Since there is only a slight change in the lubricant temperature in the internal combustion engine during the starting process, the maximum permissible basic torque value results from the lubricant temperature and the maximum permissible basic torque increases from the maximum permissible basic torque value with increasing time after the combustion engine start.

[0034] The maximum permissible base torque can be determined, for example, by means of a characteristic curve or a characteristic map, for example a characteristic map over the time after the combustion engine start and the lubricant temperature, and / or can be calculated mathematically.

[0035] In some embodiments, an adjustment factor may be determined depending on the lubricant temperature and / or the coolant temperature, and the maximum allowable base torque may be adjusted depending on the determined adjustment factor.

[0036] The adjustment factor can be read or derived from a characteristic curve or a characteristic map. The characteristic curve or characteristic map can preferably be generated using models based on experimental measurements. For example, the adjustment factor can be read from a characteristic map of the lubrication and coolant temperatures, which reflects a relationship between the lubrication and coolant temperatures on the one hand and the lubrication condition of the internal combustion engine on the other.

[0037] Thus, in the event of a critical start-up of the internal combustion engine, the maximum permissible combustion torque (maximum permissible torque) can be limited depending on the lubricant or coolant temperature and then ramped or increased to its maximum (maximum available torque) over time after the combustion engine starts. This significantly minimizes wear on the internal combustion engine during a critical start-up.

[0038] In some embodiments, the maximum permissible base torque or the adjusted maximum permissible base torque can be increased to the maximum available torque (maximum possible torque) after a predetermined number of combustion cycles and / or a predetermined number of crankshaft revolutions of the internal combustion engine since the end of the standstill of the internal combustion engine. The predetermined number of combustion cycles can be a number of combustion cycles after which the internal combustion engine is sufficiently lubricated so that sliding friction prevails even at high or maximum load. The predetermined number of combustion cycles can be determined experimentally or using a model. The same applies to the number of crankshaft revolutions.

[0039] This can prevent the combustion engine torque from being limited for an unnecessarily long period of time.

[0040] In some embodiments, an increase factor can be determined depending on the duration of the previous standstill of the internal combustion engine, the duration since the previous lubrication process of the internal combustion engine, the duration of the previous operation of the internal combustion engine, and / or the duration of the previous lubrication process of the internal combustion engine, and the maximum permissible base torque or the adjusted maximum permissible base torque can be adjusted depending on the determined increase factor. The increase factor can preferably be equal to or greater than 1.

[0041] The increase factor can be read or derived from a characteristic curve or a characteristic map. The characteristic curve or characteristic map can preferably be generated using models based on experimental measurements. For example, the increase factor can be read from a return flow characteristic curve, which reflects the dependence of a lubricant level of the internal combustion engine on a lubrication-free period or the duration of the internal combustion engine's downtime. The lubricant level preferably indicates how much of the lubricant has remained in an oil gallery and / or has flowed back into an oil reservoir of the internal combustion engine. Alternatively, a return flow characteristic map can also be used.

[0042] For example, a first factor can be determined based on the duration of the previous operation of the internal combustion engine and the duration of the previous lubrication process of the internal combustion engine. Additionally or alternatively, a second factor can be determined based on the duration of the previous downtime of the internal combustion engine and the duration since the previous lubrication process of the internal combustion engine. The first factor and the second factor can then be combined to form the increase factor. Alternatively, the first factor or the second factor can be used as the increase factor.

[0043] The critical start can therefore also be assessed based on the duration of the last lubrication process or the last combustion runtime. Additionally or alternatively, the critical start can also be assessed based on a long engine shutdown period or a lubrication process that occurred a long time ago. Long shutdown times lead to the lubricant flowing back into the oil pan and the oil gallery running dry.

[0044] In some embodiments, when a maximum possible torque is requested, the operating torque may correspond to the maximum allowable torque during the start-up process.

[0045] If it is necessary to set a maximum possible torque to meet a driver's desired torque, the maximum permissible torque of the internal combustion engine can be set, whereby the maximum permissible torque during the starting process approaches the maximum possible torque and corresponds to the maximum possible torque at the end of the starting process.

[0046] In some embodiments, the internal combustion engine, which is an internal combustion engine of a hybrid vehicle that further comprises an electric drive motor or other drive, can be started during operation of the electric drive motor or other drive. As already mentioned above, the starting process can only occur from a purely electric operating mode of the hybrid vehicle and / or during a hybrid operating mode of the hybrid vehicle. Alternatively or additionally, the starting process can be a start during coasting operation of the hybrid vehicle.

[0047] The method according to the invention for operating an internal combustion engine of a motor vehicle during a starting process enables needs-based protection of the internal combustion engine and associated components against damage, a reduction of mechanical wear on components and thus an increased service life of the components.

[0048] The present invention further relates to an engine control for operating an internal combustion engine of a motor vehicle during a starting process of the internal combustion engine, wherein the engine control is designed to carry out a method for operating an internal combustion engine of a motor vehicle during a starting process, as described above.

[0049] The engine control is designed to receive a lubrication state variable that represents a lubrication state of the internal combustion engine, to determine a maximum permissible torque of the internal combustion engine depending on the lubrication state variable, and to operate the internal combustion engine at an operating torque that corresponds to or is less than the determined maximum permissible torque of the internal combustion engine.

[0050] The engine control unit may comprise a processor, for example a microprocessor, designed to execute the described method according to the invention. The engine control unit may further comprise a data memory, in which a program is preferably stored containing instructions for the processor to control it according to the described method. Characteristic curves, characteristic maps, and / or other parameters necessary for executing the method, for example, the aforementioned models, characteristic curves, characteristic maps, and / or other parameters, may also be stored in the data memory.

[0051] The engine control unit can have a number of signal inputs and outputs. Data such as the lubrication status can be received via the signal inputs. The internal combustion engine can be controlled via the signal outputs.

[0052] The present invention relates to a motor vehicle with an internal combustion engine, for example a gasoline engine or a diesel engine, and an engine control system designed as described above.

[0053] The motor vehicle may be a hybrid vehicle with an internal combustion engine and an electric drive motor. For example, the hybrid vehicle may be a parallel hybrid vehicle.

[0054] Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings. Fig. 1 shows a schematic representation of a hybrid vehicle according to the invention; Fig. 2 shows a flowchart of a method for operating an internal combustion engine of a motor vehicle during a starting process from a standstill to high loads; Fig. 3 shows a representation of a curve of a maximum permissible torque of the internal combustion engine; Fig. 4 shows a flowchart of a method for determining the maximum permissible torque of the internal combustion engine; Fig. 5 shows a schematic representation of a maximum permissible base torque of the internal combustion engine as a function of an oil temperature and a time since the end of a standstill of the internal combustion engine; Fig. 6 shows a schematic representation of an adaptation factor as a function of the oil temperature and a cooling temperature; Fig. 7 shows a flowchart of a method for determining an increase factor; Fig.Fig. 8 shows a schematic representation of a first factor as a function of a duration of a previous operation of the internal combustion engine and a duration of a previous lubrication process of the internal combustion engine; and Fig. 9 shows a schematic representation of a second factor as a function of a duration of a previous standstill of the internal combustion engine and a duration since a previous lubrication process of the internal combustion engine.

[0055] An embodiment of a hybrid vehicle 1 is shown in Fig. 1 shown schematically. The hybrid vehicle 1 comprises a drive train with a drive device 2, which is connected to a drive axle 12 via a crankshaft 10 and a transmission 11 in order to move wheels of the hybrid vehicle 1 connected to the drive axle 12. The drive device 2 has, as drive units, an internal combustion engine 20 with a lubricant circuit 200 and a coolant circuit 201, and an electric machine 21 (electric machine).

[0056] The hybrid vehicle 1 has, as shown in Fig. 1 shown, also has an engine control unit 3. The engine control unit 3 is connected via a data line 40 to an oil temperature sensor 202 in the lubricant circuit 200, via a data line 41 to a cooling water temperature sensor 203 in the coolant circuit 201, and via a data line to a crankshaft angle sensor (not shown) in order to receive an oil temperature detected by the oil temperature sensor 202, a cooling water temperature detected by the cooling water temperature sensor 203, or a crankshaft signal detected by the crankshaft angle sensor. Furthermore, the engine control unit 3 is connected via a data line 42 to the internal combustion engine 20 and via a data line 43 to the electric motor 21 in order to control the internal combustion engine 20 and the electric motor 21, respectively. In addition, the engine control unit 3 is connected via a data line 44 to a sensor (not shown) on an accelerator pedal 5 in order to receive a control signal containing a driver command.

[0057] The engine control unit 3 contains a processor and a data memory. The processor is configured to control the drive device 2 with the aid of a program stored in the data memory. For this purpose, a target internal combustion engine torque and a target electromotive torque are determined depending on the driver's input and a current operating mode, such as a purely electric, hybrid, or purely internal combustion engine operating mode. The internal combustion engine 20 is then controlled such that it provides an internal combustion engine operating torque that essentially corresponds to the target internal combustion engine torque or is equal to a maximum available internal combustion engine torque.The electric motor 21 is controlled in such a way that it provides an electromotive operating torque that essentially corresponds to the desired electromotive torque or is equal to a maximum available electromotive torque.

[0058] In the event of a change from the purely electric operating mode to the hybrid or the purely combustion engine operating mode or in the hybrid operating mode while the internal combustion engine is at a standstill, the engine control is designed to carry out a method 6 for operating the internal combustion engine 30 during a starting process of the internal combustion engine 30 from a standstill, as described below with reference to Fig. 2 The starting process can be performed from electric driving mode in hybrid operating mode or from purely electric operating mode.

[0059] At 60 in Fig. 2 It is detected whether a start-up process of the internal combustion engine from a standstill to high loads is necessary, and such a start-up process is initiated if necessary. This process detects whether a driver requests a significantly increased total torque (driver request torque MF ) via a corresponding driver command, which requires the internal combustion engine to be switched on from a standstill to high loads.

[0060] An example of the curve of the driver's desired torque MF , which includes a strong increase in the driver's desired torque, is shown in Fig. 3 shown. Before a time t 1, the driver's desired torque MF is constant at a first value MF,0 , which can be provided solely by the electric motor. Accordingly, before t 1, a speed ne of the electric motor is constant at a value ne,max and the internal combustion engine is at a standstill. At time t 1, the driver's desired torque MF increases abruptly with a steep gradient to a second value MF,max, which remains constant until time t 2. Between t 1 and t 2, the speed ne of the electric motor is constant at the value ne,max and after a short delay, a speed nv of the internal combustion engine increases at t 3 to a value nv,max . After t 2, the driver's desired torque MF drops to a lower value. Accordingly, the speed nv of the internal combustion engine also decreases.

[0061] At 61, a maximum permissible internal combustion engine torque M v,z is determined continuously during the entire starting process of the internal combustion engine between t 1 and t 4. The determination of the maximum permissible internal combustion engine torque M v,z is described further below with reference to Fig. 4 explained.

[0062] At 62, the internal combustion engine is controlled as a function of the desired internal combustion engine torque and the maximum permissible internal combustion engine torque M v,z.

[0063] Fig. 4 explains the determination 61 of the maximum permissible combustion engine torque M v,z .

[0064] At 70, an oil temperature T ö , which is detected by the oil temperature sensor arranged in the lubricant circuit of the internal combustion engine, is received. Since the oil temperature T ö changes only imperceptibly during the start-up process of the internal combustion engine, the oil temperature is received at the beginning of the start-up process of the internal combustion engine.

[0065] At 71, a time t vs is continuously recorded since the end of the standstill of the internal combustion engine.

[0066] At 73, a maximum permissible base torque M v,g is determined depending on the oil temperature T ö and the time t vs since the end of the standstill or the beginning of the starting process of the internal combustion engine. For this purpose, a model is stored in the data memory of the engine control unit, for example, the one in Fig. 5 The map shows that the maximum permissible base torque M v,g is greater and increases more rapidly with time, the higher the oil temperature T ö1 , T ö2 , T ö3 is, with the oil temperature increasing from T ö1 to T ö3.

[0067] At 72, a coolant temperature TK is received, which is detected by the cooling water temperature sensor arranged in the coolant circuit of the internal combustion engine. The coolant temperature TK also changes only imperceptibly during the start-up process of the internal combustion engine and is therefore only received at the beginning of the start-up process of the internal combustion engine.

[0068] At 74, an adjustment factor Fa is determined based on the oil temperature Tö and the cooling water temperature TK. The adjustment factor Fa is read from a characteristic map of the oil temperature Tö and the coolant temperature TK, which reflects a relationship between the oil temperature Tö and the coolant temperature TK on the one hand and the lubrication state of the internal combustion engine on the other. Such a characteristic map, which is stored in the data memory of the engine control unit, is in Fig. 6 shown as an example. Fig. 6 shows that the adjustment factor Fa assumes values ​​around 1 and increases with increasing cooling water temperature TK. The adjustment factor Fa is lower at low oil temperatures T ö1 than at high oil temperatures T ö3 .

[0069] At 75, the maximum permissible base torque M v,g is adjusted depending on the specific adjustment factor Fa. The higher the oil temperature T ö and the coolant temperature TK, the greater the adjustment factor Fa and thus the adjusted permissible base torque. A limit on the maximum permissible torque is adjusted accordingly.

[0070] At 76, a crankshaft sensor signal is received and by evaluating the crankshaft sensor signal (cylinder counter) a number of combustions since the beginning of the starting process is determined.

[0071] At 77, if a predetermined number of combustions have been carried out since the start-up process began, the adjusted maximum permissible torque is ramped up or increased to the maximum available combustion engine torque M v,max.

[0072] At 78, the duration of the previous standstill of the internal combustion engine, the duration since the previous lubrication process of the internal combustion engine, the duration of the previous operation of the internal combustion engine, and / or the duration of the previous lubrication process of the internal combustion engine are determined by evaluating a stored crankshaft sensor signal. The stored crankshaft sensor signal is stored in the data memory and extends over a period of time that encompasses an interval from a previous start of the internal combustion engine to the beginning of the start process of the internal combustion engine.

[0073] At 79, an increase factor FE is determined depending on the duration of the previous standstill of the internal combustion engine, the duration since the previous lubrication process of the internal combustion engine, the duration of the previous operation of the internal combustion engine, and the duration of the previous lubrication process of the internal combustion engine. The increase factor FE is equal to or greater than 1. The determination 79 of the increase factor FE is described below with reference to the Fig. 7 explained.

[0074] At 790, a first factor F E1 is determined depending on the duration DB of the previous operation of the internal combustion engine and the duration DS of the previous lubrication process of the internal combustion engine. Fig. 8 shows, by way of example, two courses of the first factor F E1 as a function of the duration DB of the previous operation of the internal combustion engine for the durations D S1 , D S2 of the previous lubrication process of the internal combustion engine, where D S1 is shorter than D S2 .

[0075] At 791, a second factor F E2 is determined depending on the duration DR of the previous standstill of the internal combustion engine and the duration DO since the previous lubrication process of the internal combustion engine. Fig. 9 shows two exemplary courses of the second factor F E2 as a function of the duration DR of the previous standstill of the internal combustion engine and the duration DO since the previous lubrication process of the internal combustion engine, where D O1 is shorter than D O2 .

[0076] At 792, the first factor F E1 and the second factor F E2 are then combined to form the increase factor FE, whereby the increase factor is never less than 1. In the combination, the smaller of the first and second factors F E1, F E2 is adopted.

[0077] If the combustion engine has been idle for a very long time, i.e., not running, it can be assumed that the oil gallery has run dry. In this case, a factor of 1 is output, resulting in the limiting torque calculated above.

[0078] If the combustion engine has already started running and / or the engine has not been at a standstill for too long, the increase factor FE can be set to greater than 1. This means that the torque limitation is no longer as severe.

[0079] At 80 in Fig. 4 The maximum permissible combustion engine torque is determined by adjusting the adjusted maximum permissible base torque depending on the determined increase factor FE. If the increase factor FE is equal to 1, the maximum permissible base torque corresponds to the adjusted maximum permissible base torque, and if the increase factor FE is greater than 1, the adjusted maximum permissible base torque is increased.

[0080] The maximum permissible torque M v,z is in Fig. 3 shown. The maximum permissible torque M v,z rises steeply after t 3 to a value M v,z1 and then increases in a ramp to the maximum possible torque M v,max . As long as the requested driver torque MF requires the operation of the internal combustion engine and it does not come to a standstill, the maximum permissible internal combustion engine torque M v,z remains at the maximum possible torque M v,max . Bezugszeichenliste

[0081] 1Hybrid vehicle 10Crankshaft 11Gearbox 12Drive axle 2Drive device 20Internal combustion engine 200Lubricant circuit 201Coolant circuit 202Oil temperature sensor 203Cooling water temperature sensor 21E -machine 3Engine control 40, 41, 42, 43, 44Data lines 5Accelerator pedal 6Method for operating the internal combustion engine 60Detecting whether a starting process of the internal combustion engine from a standstill to high loads is required 61Determining a maximum permissible internal combustion engine torque 62Controlling the internal combustion engine 70Receiving the oil temperature 71Recording the time since the end of the standstill of the internal combustion engine 72Determining a maximum permissible base torque 73Receiving the coolant temperature 74Determining an adaptation factor 75Adjusting the maximum permissible Base torque 76Determining a number of combustions since the start-up process 77Increasing the adjusted maximum permissible base torque aftera predetermined number of combustions 78Evaluating a stored crankshaft sensor signal 79Determining an increase factor 790Determining a first factor 791Determining a second factor 792Combining the first and the second factor 80Determining the maximum permissible internal combustion engine torque DB Duration of the previous operation DS , D S1 , D S2 Duration of the previous lubrication process of the internal combustion engine DR Duration of the previous standstill of the internal combustion engine DO , D O1 , D O2 Duration since the previous lubrication process of the internal combustion engine F a Adaptation factor FE Increase factor F E1 first factor F E2 second factor MF Driver's desired torque MF,1 first value of the driver's desired torque MF,max second value of the driver's desired torque M v,max maximum retrievable internal combustion engine torque M v,z maximum permissible internal combustion engine torque M v,z1 maximum permissible torque directly after the start of theStarting process M v,g maximum permissible basic torque of the internal combustion engine ne speed of the electric motor ne,max maximum speed of the electric motor nv speed of the internal combustion engine nv,max maximum speed of the internal combustion engine t 1 time of an increase in the driver's desired torque t 2 time of a reduction in the driver's desired torque t 3 time of an increase in speed and an increase in the maximum permissible torque of the internal combustion engine t 4 time of an end of a starting process of the internal combustion engine t vs time since the start of the starting process T ö , T ö1 , T ö2 , T ö3 oil temperature TK coolant temperature

Claims

1. Method for operating an internal combustion engine (20) of a hybrid vehicle during a starting-up process of the internal combustion engine (20), comprising: obtaining a lubrication state variable which represents a lubrication state of the internal combustion engine (20), the lubrication state variable comprising a lubricant temperature (Tö) of lubricant in the internal combustion engine (20) or a lubricant pressure of the lubricant in the internal combustion engine (20), determining (72) a maximum permissible basic torque (Mv,g) of the internal combustion engine (20) depending on the lubricant temperature (Tö) of the lubricant in the internal combustion engine (20) or on the lubricant pressure of the lubricant in the internal combustion engine (20), determining (79) an increase factor (FE) depending on a duration (DR) of a previous standstill of the internal combustion engine (20), a duration (DB) of a previous operation of the internal combustion engine (20) and / or a duration (Ds) of a previous lubrication process of the internal combustion engine (20), determining (80) a maximum permissible torque by adjusting the maximum permissible basic torque (Mv,g) depending on the determined increase factor (FE), and operating (62) the internal combustion engine (20) at an operating torque which corresponds to or is less than the determined maximum permissible torque (Mv,z), the operating torque corresponding to the maximum permissible torque (Mv,z) during the starting-up process if the maximum possible torque (Mv,max) is requested, characterized in that the internal combustion engine is switched on in order to fill an oil gallery and / or to supply components of the internal combustion engine with oil, and in that the increase factor (FE) depends additionally on a duration (Do) since a previous lubrication process of the internal combustion engine (20), the increase factor (FE) being equal to or greater than 1, and the maximum permissible torque corresponding to the maximum permissible basic torque if the increase factor (FE) is equal to 1, and the maximum permissible basic torque being increased if the increase factor (FE) is greater than 1.

2. Method according to claim 1, wherein the maximum permissible torque (Mv,z) of the internal combustion engine (20) is increased as time goes on after starting up the internal combustion engine (20) or is increased as the number of combustions increases since the start up of the internal combustion engine (20).

3. Method according to claim 1 or claim 2, wherein an adjustment factor (Fa) is determined depending on the lubricant temperature (Tö) and / or a coolant temperature (TK); and the maximum permissible basic torque (Mv,g) is adjusted depending on the determined adjustment factor (Fa).

4. Method according to any of claims 1 to 3, wherein the maximum permissible basic torque (Mv,g) is increased to a maximum possible torque (Mv,max) of the internal combustion engine (20) after a predetermined number of combustions and / or crankshaft revolutions of the internal combustion engine (20) since the end of a standstill of the internal combustion engine (20).

5. Method according to any of claims 1 to 4, wherein the internal combustion engine (20), which is an internal combustion engine of a hybrid vehicle (1) which further comprises an electric machine (21) or another drive, is started up during operation of the electric machine (21) or the other drive.

6. Engine controller (3) for operating an internal combustion engine (20) of a hybrid vehicle during a starting-up process of the internal combustion engine (20), which engine controller comprises a processor, a data memory and the means for limiting the requested operating torque of the internal combustion engine (20), wherein the internal combustion engine can be switched on in order to fill the oil gallery and / or supply the components of the internal combustion engine with oil; and wherein the engine controller (3) is designed to carry out a method according to any of the preceding claims.