DE102007059879B3 - Method and device for operating an internal combustion engine - Google Patents

Abstract

An internal combustion engine is operable with a fuel (52) comprising gasoline and an alternative fuel. For operating the internal combustion engine, a proportion value of the alternative fuel in the fuel (52) is determined. Correlating with determining the proportion value of the alternative fuel, a temperature value (TOIL) of an engine oil, which is located in a crankshaft housing of the internal combustion engine, is determined. A fractional value (FUEL_PERC) of the fuel in the engine oil is determined. A current load of the internal combustion engine is determined. An uncertainty value (VAR_BIT) representative of the uncertainty of the determined fractional value of the alternative fuel is given if the determined temperature value (TOIL) of the engine oil is within a predetermined temperature range if the determined value of fuel (FUEL_PERC) in the engine oil is greater than a predetermined threshold and if the determined load of the internal combustion engine is in a lower load range of the internal combustion engine.

Description

The The invention relates to a method and an apparatus for operating an internal combustion engine. The internal combustion engine is operable with a fuel, includes gasoline and an alternative fuel.

One Flexible Fuel Vehicle (FFV) is a vehicle that both with pure Gasoline as well as with a mixture of gasoline and an alternative fuel, for example, an ethanol-gasoline mixture, can be operated.

From the US 5,182,942 A For example, a method for determining an ethanol content in a fuel is known. For this purpose, a sample of the fuel is heated and recorded their evaporation temperature. Depending on the evaporation temperature is closed to the ethanol content of the fuel.

From the US 2003/0075119 A1 For example, a method is disclosed for checking accuracy of oxygen sensor based determination of the alcohol content of the fuel of a flexible fuel vehicle. After adding fuel, two alcohol concentration options are calculated. These two alcohol concentration options are then used to calculate thresholds for determining whether the alcohol level determined by the oxygen sensor-based determination falls within these thresholds. If this is not the case, measures are taken to meet an inaccurate determination of the alcohol concentration.

The The object of the invention is based, a method and to provide an apparatus for operating an internal combustion engine, which is fuel-fueled, gasoline and an alternative fuel includes, a fold to a reliable operation of the internal combustion engine contribute, even if a share value of the alternative fuel is not certainly known.

The Task is solved by the characteristics of the independent Claims. Advantageous embodiments are specified in the subclaims.

The Invention is characterized according to a First aspect by a method and an apparatus for operating an internal combustion engine. The internal combustion engine is fueled operable comprising gasoline and an alternative fuel. One Proportion value of the alternative fuel in the fuel is determined. Correlating to determine the percentage value of the alternative fuel a temperature value of an engine oil is determined. The engine oil is located in a crankcase the internal combustion engine. Furthermore, to determine the unit value of the alternative fuel correlates a share value of the fuel in the engine oil and determines a current load of the internal combustion engine. It will given an uncertainty value that is representative of that the calculated share value of the alternative fuel is uncertain, if the determined temperature value of the engine oil within a predetermined Temperature range is, if the determined share value of the fuel in the engine oil bigger than one predetermined threshold and if the determined load in a lower load range of the internal combustion engine is located.

This just wear to a particularly reliable Operation of the internal combustion engine, since under the conditions mentioned there is a high probability that the determined share value of the alternative fuel, not the actual share value of the alternative fuel corresponds in the fuel tank of the internal combustion engine. Determining the share value of the alternative fuel may in this context also referred to as adapting the percentage value of the alternative fuel become. That the determined share value of the alternative fuel is insecure means in this context that the determined Share value of the alternative fuel is not known for sure and in other words can be incorrectly determined and / or adapted. That the temperature value of the engine oil correlates to determine the share value of the alternative fuel is determined in this context, that the temperature value of the engine oil in time correlating and thus during or promptly to determine the proportional value of the alternative fuel is determined.

Of the Uncertainty value can during or immediately after determining the fair value of the alternative fuel or at a later time Time can be specified if necessary. For example, appropriate Measurement data for determining the temperature value of the engine oil, the Proportion of the fuel in the engine oil and the load of the internal combustion engine while of adapting the fractional value of the alternative fuel and the corresponding farm sizes can be determined immediately become. Alternatively, you can the measurement data first only be stored and later if necessary depending on the stored measured data, the corresponding operating variables determined become. Furthermore, the corresponding operating sizes, too be determined directly after the acquisition of the measurement data and the Uncertainty value is only specified when needed. Preferably is at a driving cycle following the driving cycle, in the the uncertainty value has been specified, the predetermined uncertainty value used at a start of the internal combustion engine to check if the determined, in particular adapted share value of the alternative fuel certainly known.

The Invention is characterized according to a second aspect by a method and an apparatus for operating the internal combustion engine. The internal combustion engine is with the fuel operable comprising gasoline and alternative fuel. At the Start of the internal combustion engine is checked if the current share value the alternative fuel is safely known in the fuel. If the current share value of the alternative fuel is not safe is known, the share value at the start of the internal combustion engine of the alternative fuel automatically varies until the internal combustion engine automatic is working.

This allows even if the share value of the alternative fuel is not known to start the engine safely. This is easy to the reliable one Operation of the internal combustion engine. The current share value of the Alternative fuel is preferably the last determined, in particular in a given operating point adapted share value of the alternative fuel, for example, the last determined in the previous drive cycle Proportional value of the alternative fuel in the corresponding predetermined Operating point. That the internal combustion engine works automatically, in this context means that the internal combustion engine due the internal combustion processes works and no longer with an example electric starter must be driven.

In an advantageous embodiment is checked whether the current share value certainly known. The proportional value of the alternative fuel becomes varies if the uncertainty value is given. This makes possible, easy to determine if the proportional value of the alternative fuel certainly known.

In In another advantageous embodiment, the current share value of the alternative fuel classified as not safe if a Number of false starts immediately before the start of the internal combustion engine greater than is a predetermined threshold. This allows, especially easy to recognize whether the share value of the alternative fuel is known for sure is.

In a further advantageous embodiment, if the current Share value of the alternative fuel is not known for certain at the start of the internal combustion engine in a first predetermined start cycle range the internal combustion engine based on the uncertain determined Share value of the alternative fuel operated. If the internal combustion engine during the first start cycle does not work automatically is in one second predetermined starting cycle range based on the internal combustion engine at a predetermined first extreme value of the fraction of the alternative fuel operated. this makes possible easy to vary the proportion of alternative fuel. The predetermined start cycle ranges preferably include multiple startup cycles. A start cycle encompasses half a turn of the crankshaft Internal combustion engine while she is driven by the starter. At a start of the internal combustion engine Preferably, several start cycles occur.

Of the Extreme value can be, for example, the extreme value of the unit value of the Be alternative fuel, with the engine straight can still be operated. This extreme value can be fixed be. Alternatively, an estimate may be made, such as strong the share value of the alternative fuel from the last determined share value of the alternative fuel. The dependent from this estimate The calculated value can then be specified as an extreme value.

In a further advantageous embodiment is in a third Starting cycle range of the internal combustion engine based on a predetermined second Extreme value of proportion of alternative fuel operated if the internal combustion engine during the second start cycle range does not work automatically. This allows easy to vary the share value of the alternative fuel if under Use of the first extreme value of the start of the internal combustion engine not happened.

In According to a further advantageous embodiment, the first and / or second extreme value of the share value of the alternative fuel one Maximum value and / or a minimum value of the share value of the alternative fuel. This can be the reliable one Operation of the internal combustion engine contribute.

embodiments The invention are explained in more detail below with reference to schematic drawings.

It demonstrate:

1 an internal combustion engine,

2 a flowchart of a first program for operating the internal combustion engine,

3 a flowchart of a second program for operating the internal combustion engine,

4 a flowchart of a third program for operating the internal combustion engine.

elements same construction or function are cross-figurative with the same Reference number marked.

An internal combustion engine ( 1 ) comprises an intake tract 1 , an engine block 2 , a cylinder head 3 and an exhaust tract 4 ,

The intake tract 1 preferably comprises a throttle valve 5 , a collector 6 and a suction tube 7 leading to a cylinder Z1 via an inlet channel into a combustion chamber 9 of the engine block 2 is guided. The engine block 2 further comprises a crankshaft 8th , which has a connecting rod 10 with the piston 11 of the cylinder Z1 is coupled. The internal combustion engine comprises at least one cylinder Z1, but preferably further cylinders Z2, Z3, Z4, but may also comprise any larger number of cylinders. The internal combustion engine is preferably arranged in a motor vehicle.

The cylinder head 3 includes a valvetrain 14 . 15 that with a gas inlet valve 12 or a gas outlet valve 13 is coupled. The valve train 14 . 15 includes at least one camshaft with the crankshaft 8th is coupled. Further, in the cylinder head 3 preferably an injection valve 18 and a spark plug 19 arranged. Alternatively, the injection valve 18 also in the intake manifold 7 be arranged. In the exhaust tract 4 is an exhaust gas catalyst 21 arranged, which is preferably designed as a three-way catalyst.

Further, a fuel tank 50 provided, at least partially with a fuel 52 is filled. The fuel 52 gets to the combustion chamber 9 the internal combustion engine for a combustion process metered. The metering is preferably carried out via the injection valve 18 , The fuel 52 preferably includes gasoline and an alternative fuel, for example alcohol, especially ethanol.

A control device 25 is provided, the sensors are assigned, which detect different measured variables and each determine the measured value of the measured variable. The control device 25 determined depending on at least one of the measured variables manipulated variables, which are then converted into one or more control signals for controlling the actuators by means of appropriate actuators. The control device 25 can also determine depending on the measured variables or derived variables operating variables of the internal combustion engine. The measured variables and / or the operating variables of the internal combustion engine specify, for example, operating points of the internal combustion engine. The control device 25 may also be referred to as a device for operating the internal combustion engine.

The sensors are, for example, a pedal position transmitter 26 , the accelerator pedal position of an accelerator pedal 27 detected, an air mass sensor 28 containing a mass air flow MAF ( 2 ) upstream of the throttle 5 detected, a throttle position sensor 30 , an opening degree of the throttle valve 5 detected, an intake air temperature sensor 32 sensing an intake air temperature, an intake manifold pressure sensor 34 that produces a manifold pressure in the collector 6 detected, a crankshaft angle sensor 36 which detects a crankshaft angle, which is then assigned a rotational speed N of the internal combustion engine. Furthermore, there is a lambda probe 42 provided upstream of the catalytic converter 21 is arranged and detects, for example, the residual oxygen content of the exhaust gas and the measurement signal is characteristic of the air / fuel ratio in the combustion chamber 9 of the cylinder Z1. An exhaust gas temperature sensor 44 may be provided for detecting an exhaust gas temperature and an ambient air temperature sensor 46 may be provided for detecting an ambient air temperature.

ever according to embodiment The invention may be any subset of said sensors be present or it can also additional Sensors be present.

The actuators are, for example, the throttle 5 , the gas inlet and outlet valves 12 . 13 , the injection valve 18 and / or the spark plug 19 ,

The fuel 52 may be composed differently of the gasoline and the alternative fuel, for example the ethanol. For example, an actual fractional value of the alternative fuel may vary depending on which mixture the last visited gas station offered, when only how much ethanol or gasoline was being charged, or how long the engine was shut down. Depending on the actual share value of the alternative fuel, the internal combustion engine can be operated differently in one operating point, for example in order to ensure perfect functioning of the internal combustion engine and / or preferably optimal efficiency of the internal combustion engine. For example, depending on the proportion of the alternative fuel, an ignition point and / or an injection mass may vary at the predetermined operating point. Therefore, a share value of the alternative fuel is regularly determined during operation of the internal combustion engine. However, there are conditions in which the calculated value of the alternative fuel is unlikely to correspond to the actual value of the alternative fuel. For example, at a cold start of the engine fuel 52 from the combustion chamber 9 between the piston 11 and the cylinder wall of the cylinder Z1 in a crankcase of the engine block 2 to crawl. There, the fuel mixes 52 with engine oil. The more cold starts that occur over a given period of time, the higher the amount of fuel in the crankcase and the higher is a share value FUEL_PERC of the fuel 52 in the engine oil. Therefore, the fuel fraction in the crankshaft housing can be determined, for example, by counting the cold starts in a given period of time. If the fuel evaporates from the engine oil during operation of the internal combustion engine, this may lead to the detection of the wrong proportion value of the alternative fuel. The evaporation of the fuel from the engine oil is especially large in a predetermined temperature range, for example between 50 and 80 degrees Celsius, and at low load of the internal combustion engine.

On a storage medium of the control device 25 is preferably stored a first program for operating the internal combustion engine ( 2 ). The first program for operating the internal combustion engine serves to detect whether the current share value of the alternative fuel is known for certain. The current share value of the alternative fuel is preferably the last adapted share value of the alternative fuel for the corresponding operating point of the internal combustion engine. In other words, the first program is to check whether, during the adaptation of the share value of the alternative fuel, the conditions exist that suggest that the adapted share value of the alternative fuel was wrongly determined.

The first program is preferably during the determination of the unit value of the alternative fuel is started in a step S1, where appropriate Variables are initialized.

alternative can do this the necessary ones Readings during of adapting the fractional value of the alternative fuel only be captured and stored. The first program can then be later if needed be started and processed. This is what the first program takes then to the corresponding stored measured values.

In a step S2, the rotational speed N of the internal combustion engine and the mass air flow MAF determined. The mass air flow MAF is representative of a current Load of the internal combustion engine. Alternatively, for determining the load, for example, also determines an intake manifold pressure of the internal combustion engine become.

In Step S3 checks whether an alternative fuel detection function, In particular, an ethanol detection function ETH_FCT is active. is satisfies the condition of step S3, the processing becomes continued in a step S4. Is the condition of the step S3 not met, the processing is continued in a step S7.

In step S4, a temperature value T_OIL of the engine oil is determined, for example by means of a corresponding temperature sensor. In addition, it checks whether the Temperature value T_OIL within the specified temperature range lies. Further, in the step S4, a share value FUEL_PERC of the Fuel in the engine oil determined, for example, by determining a number of cold starts within the given time period. In addition, it checks whether the Proportion value FUEL_PERC of the fuel greater than a predetermined share threshold is. If the conditions of step S4 are satisfied, then the processing continued in a step S5. Are the condition of the step S4 not fulfilled, the processing is continued in step S7.

In Step S5 checks whether the determined air mass flow MAF less than a predetermined air mass flow threshold MAF_THD is. If the condition of step S5 is not met, then the processing continues in a step S8. Is the condition of step S5, so this means that the engine at the time of Adapting the proportion of the alternative fuel in one lower load range was operated, and the processing is in a step S6 continued.

In step S6, an uncertainty value VAR_BIT is specified. Preferably, this is done, for example, on the storage medium of the control device 25 set or set a bit representative of the fact that the determined fractional value of the alternative fuel may be incorrect and thus uncertain. Alternatively, an accurate probability value may be determined representative of the probability that the fractional value of the alternative fuel is incorrect.

In Step S7 checks whether a Time T after a start of the internal combustion engine is greater than is a predetermined first time threshold T_THD_1. Is the condition of step S7 not met, so the processing is continued in a step S9. Is the Condition of step S7 is met, so the processing is continued in a step S8.

In step S8, the uncertainty value VAR_BIT is deleted by means of a deletion instruction DEL. For example, the corresponding bit on the storage medium of the controller 25 reset.

In a step S9, an error message ERROR which is representative of a false start can be generated. For example, the ERROR error message may be an entry in an error memory cher of the internal combustion engine lead. Alternatively or additionally, a Fehlstartzähler ERR_CTR can be increased by one unit.

In In a step S10, the first program for operating the internal combustion engine to be ended. Preferably, the program for operating the Internal combustion engine, however, always processed when the share value of the alternative fuel is re-adapted or checked should, whether the current share value of the alternative fuel safe is known.

If the internal combustion engine does not start in one or more start attempts, this can also be an indication that the share value of the alternative fuel is unsafe and thus incorrectly determined and / or adapted. Therefore, on the storage medium of the control unit 25 preferably a second program for operating the internal combustion engine is stored ( 3 ). The second program for operating the internal combustion engine is used to decide, depending on one or more false starts, whether the currently known share value of the alternative fuel is known for certain.

The second program for operating the internal combustion engine, for example at the start of the internal combustion engine, preferably in one step S11 is started in which variables are initialized if necessary.

In In a step S12, it is checked whether the rotational speed N greater than is a start-end speed N_FIN of the internal combustion engine. The start-end speed N_FIN of the internal combustion engine is the speed of the internal combustion engine, at least having the internal combustion engine when the starting process is finished and the internal combustion engine works automatically. Means automatically in this regard, that the internal combustion engine without a starter works due to their internal combustion processes. Is the condition of step S12, so the processing is continued in a step S13. Is the condition of step S12 not satisfied, so the processing is continued in a step S16.

In In step S13, it is checked whether the internal combustion engine parked due to an operator request of an operator of the internal combustion engine was, and thus a final engine stop ENG_STOP was intended. Further, it is checked in step S13 whether the Time T after engine start smaller than a predetermined threshold is. If the condition of step S13 is not met, then the processing is continued in a step S17. Is the condition of step S13, so processing is continued in a step S14.

In Step S14 checks if the Time T after engine start greater than a predetermined second Time threshold T_THD_2 is. Is the condition of step S14 Fulfills, so the processing is continued in a step S15. Is the Condition of step S14 is not satisfied, so the processing continued in a step S20.

In Step S16 checks whether theoretically an engine start could occur by checking whether during the current start of the engine enough start cycles ZYK performed were. A start cycle ZYK preferably comprises a 180 ° rotation the crankshaft, due to a drive of the starter of the internal combustion engine he follows. Preferably, at each start of the internal combustion engine several start cycles ZYK performed. For example, at startup, eight cycles of ZYK are performed. is satisfies the condition of step S16, the processing in a step S17 continues. Is the condition of step S16 not fulfilled, so processing is continued in step S20.

In In step S17, a false start bit ERR_BIT is preferably set. The miss start bit ERR_BIT is representative of that the current start of the engine is a false start.

In In step S18, it is checked whether the false start counter ERR_CTR greater than is a predetermined false start threshold ERR_THD. Is the condition of step S18, so the processing is continued in a step S19. Is the Condition of step S18 is not satisfied, so the processing continued in step S20.

In Step S19 sets the uncertainty value VAR_BIT.

In Step S20 may be the second program for operating the internal combustion engine to be ended. Preferably, the second program is to operate the internal combustion engine again at the start of the engine processed.

On the storage medium of the control device 25 Preferably, a third program for operating the internal combustion engine is stored ( 4 ). The third program for operating the internal combustion engine serves to vary the proportion value of the alternative fuel until the internal combustion engine starts, if the proportion value of the alternative fuel is not known with certainty.

The third program for operating the internal combustion engine is preferably started during the start of the internal combustion engine in a step S21, in which optionally variables are initialized become.

In A step S22 checks whether the uncertainty value VAR_BIT is set. If the condition of step S22 is not fulfilled, then the processing is continued in a step S27. Is the condition of step S22, thus, the processing may be continued in a step S23.

In the step S23 one or more extreme values of the share value of the alternative fuel be determined. For example, a minimum value of ETH_MIN of Proportion value of the alternative fuel and / or a maximum value ETH_MAX of the share value of the alternative fuel. For example, the extreme values are dependent on the operating variables a maximum possible Deviation from the adapted share value of the alternative fuel determined. Alternatively, you can the extreme values are determined for example on an engine test bench and then be stored permanently on the storage medium. For example can the extreme values are set to be just based on them still operating the internal combustion engine is possible.

In In step S24, it is checked whether a start-up cycle counter ZYK_CTR is less than a predetermined start cycle threshold ZYK_THD. If the condition of step S24 is satisfied, then the processing continued in a step S25. Is the condition of the step S24 not fulfilled, so the processing is continued in a step S28.

In Step S25 checks whether the rotational speed N greater than a starter speed is N_STR. The starter speed N_STR is the Speed of the starter and can, for example, between 250 and 400 Revolutions are.

is satisfies the condition of step S25, the processing becomes continued in a step S26. Is the condition of the step S25 not met, so the processing is continued in a step S29.

In Step S26 checks whether the rotational speed N greater than the start-end speed N_FIN is. Is the condition of the step S26 fulfilled, so the processing is continued in a step S27. Is the condition of step S16 not satisfied, so will be editing in the next Start cycle ZYK continued in step S24.

In a step S28, the start-up cycle counter ZYK_CTR is set equal to zero. Further, in step S28, by means of a variation instruction VAR, the proportion value of an ethanol content ETH_PREC of the fuel 52 varied. Preferably, for the first variation of the ethanol content ETH_PERC, the internal combustion engine is operated based on the current share value of the alternative fuel. During the second processing of the variation instruction VAR, the internal combustion engine is then operated, for example, based on the minimum value ETH_MIN of the ethanol component. Furthermore, in the third execution of the variation instruction VAR, the internal combustion engine can be operated based on the maximum value ETH_MAX of the ethanol component.

In the step S29 becomes the cycle counter ZYK_CTR increased by one unit.

In Step S27 may be the third program for operating the internal combustion engine to be ended. Preferably, the third program is to operate the internal combustion engine always processed at the start of the engine.

Claims (9)

Method for operating an internal combustion engine that is fueled ( 52 ), which comprises gasoline and an alternative fuel in which a share value of the alternative fuel in the fuel ( 52 ) is determined and in which, correlated to determining the proportion value of the alternative fuel - a temperature value (TOIL) of an engine oil, which is located in a crankcase of the internal combustion engine, - a share value (FUEL_PERC) of the fuel is determined in the engine oil, and - a current load of the internal combustion engine is determined, and in which an uncertainty value (VAR_BIT) is given, which is representative that the determined share value of the alternative fuel is uncertain, if the determined temperature value (TOIL) of the engine oil is within a predetermined temperature range, if the determined share value (FUEL_PERC) of the fuel in the engine oil is greater than a predetermined threshold value and - if the determined load of the internal combustion engine is in a lower load range of the internal combustion engine. Method for operating an internal combustion engine that is fueled ( 52 ), which includes gasoline and an alternative fuel in which it is checked at the start of the internal combustion engine, whether a current share value of the alternative fuel in the fuel is known and in which, if the current share value of the alternative fuel is not known, at start the internal combustion engine, the proportion value of the alternative fuel is automatically varied until the internal combustion engine operates automatically. The method of claim 2, wherein it is checked according to the method of claim 1, whether the current share value of the alternative fuel in the fuel ( 52 ) is known for sure. The method of claim 2, wherein the current share value of the alternative fuel is classified as not safe, if a number of false starts just before the start of the engine greater than is a predetermined threshold. Method according to one of claims 2 to 4, wherein, if the current share value of the alternative fuel is uncertain is known at the start of the internal combustion engine - in one first predetermined starting cycle range based on the internal combustion engine operated on the uncertain share value determined for the alternative fuel becomes, - in a second predetermined starting cycle range, the internal combustion engine based on a predetermined first extreme value of the unit value the alternative fuel is operated, if the internal combustion engine while of the first start cycle does not work automatically. The method of claim 5, wherein in a third Starting cycle range, the internal combustion engine based on a predetermined operated at the second extreme value of the value of the alternative fuel is, if the internal combustion engine during the second start cycle range not automatically is working. Method according to one of claims 5 or 6, wherein the first and / or second extreme value of the share value of the alternative fuel a maximum value (ETH_MAX) and / or a minimum value (ETH_MIN) value of the alternative fuel. Device for operating an internal combustion engine that is equipped with a fuel ( 52 ), which comprises gasoline and an alternative fuel, wherein the device is adapted to a share value of the alternative fuel in the fuel ( 52 ) and correlatively for determining the fractional value of the alternative fuel - to determine a temperature value (TOIL) of an engine oil located in a crankcase of the internal combustion engine, - to determine a share value (FUEL_PERC) of the fuel in the engine oil, and - a current one To determine the load of the internal combustion engine and to specify an uncertainty value (VAR_BIT) which is representative of the fact that the determined proportion of the alternative fuel is uncertain, if the determined temperature value (TOIL) of the engine oil is within a predetermined temperature range, if the determined Proportion value (FUEL_PERC) of the fuel in the engine oil is greater than a predetermined threshold and - if the determined load of the internal combustion engine is in a lower load range of the internal combustion engine. Device for operating an internal combustion engine that is equipped with a fuel ( 52 ) which comprises gasoline and an alternative fuel, wherein the device is adapted to check at the start of the internal combustion engine whether a current share value of the alternative fuel in the fuel is certainly known and, if the current share value of the alternative fuel is not known with certainty is to automatically vary the share value of the alternative fuel at the start of the internal combustion engine until the internal combustion engine operates automatically.