DE102016224427B3 - Method and device for operating an internal combustion engine working with alcohol and alcohol mixed fuels - Google Patents

Abstract

The internal combustion engine has a plurality of cylinders (Z1-Z4), wherein the cylinders (Z1-Z4) are assigned cylinder-specific, electrical heating devices for heating the fuel. Upon satisfaction of a criterion (SA) which is indicative of an imminent start of the internal combustion engine and upon fulfillment of a criterion (TKW_SW1) indicative of a cold start of the internal combustion engine, the cylinder-specific heating devices are activated. Each of the cylinder-specific heaters is checked for proper function. If a defect of a heating device is detected, the fuel supply to that cylinder (Z1-Z4) to which the defective heating device is assigned is blocked. The internal combustion engine is started with a number of cylinders (Z1-Z4) reduced by the number of defective heaters. During operation of the internal combustion engine, at least one variable (TKW, N) correlated with the temperature of the internal combustion engine is monitored. When a predetermined threshold value (TKW_SW3, N_SW) for the at least one correlating variable (TKW, N) is exceeded, the fuel supply to that cylinder (Z1-Z4) is released to which the defective heating device is assigned and the heating devices are deactivated.

Description

The invention relates to a method and a device for operating a spark-ignited internal combustion engine operating with alcohol and alcohol mixed fuels, with a cylinder-specific heating device for heating the fuel.

Vehicles are known which can be operated both with alcohol or mixed alcohol fuels (fuels with variable alcohol contents), as well as with petrol fuel (gasoline) as the only fuel component. The alcohol, z. As ethanol or methanol in the fuel can be present in different proportions in the range of 0 to 100%. Such fuels are also referred to as "flex fuel" or "flexible fuel" (FF) and the motor vehicles that can be operated as a flexible fuel vehicle (FFV). A common alcohol / gasoline blend in Europe and the USA is E85 for example. H. 85% ethanol in the fuel, in which the gasoline content is therefore 15%. In particular, in the Brazilian market motor vehicles are operated, in which pure ethanol (E100) is used as fuel. In the following, when referring to E100 as the fuel, it is to be considered that usually in such fuel, 5-7% of water may be contained.

Thus, such motor vehicles offer the possibility of refueling both conventional gasoline and these mixed ethanol fuels, since the current gasoline-ethanol concentration in the fuel is detected via an alcohol sensor or a model calculation in the electronic engine control and appropriate parameters for controlling the internal combustion engine are adapted ,

The use of such blended fuels with high ethanol content has the disadvantage that the vehicle is difficult to start at low temperatures, since ethanol has a relatively high boiling point (78 ° C) and low vapor pressure, ie very poorly vaporized at low temperatures. The addition of ethanol reduces the total amount of volatile fuel and impairs cold start capability. The minimum starting temperature without additional cold-start systems is about -20 ° C when using E85 fuel and about + 15 ° C when using E100 fuel (flash point ethanol).

Since cold start problems thus occur without special precautions, motor vehicles which permit operation with fuels having very high alcohol concentrations (up to 100%) carry small, permanently installed fuel tanks carrying a small amount of starter fuel, e.g. As gasoline include. To start the motor vehicle below certain outside temperatures then gasoline is used as starting fuel or injected in addition to the alcohol, so that a combustible mixture is formed. The problem here, however, is that in a cold start only very small amounts of starting fuel are taken from the additional tank and over time, this starting fuel is getting worse. By "worse" is meant in this context that the volatile hydrocarbon fractions such as propane and butane, due to the high temperatures in the engine compartment during operation of the internal combustion engine and thus of the vehicle, and by the high temperatures in the summer months, where no starting fuel needed is, evaporate easily and escape from the auxiliary tank. The necessary components for a cold start are then lost or at least considerably reduced. Under certain circumstances, a cold start can no longer be carried out.

In the pamphlets US 4,911,116 A and US 4,646,691 A U.S. Patent Nos. 3,800,988 and 4,322,014 describe fuel systems for internal combustion engines of a motor vehicle which are operated with alcohol and have separate cold start tanks containing gasoline used for starting the engine. Subsequently, when the engine has been started and starts to warm, instead of the cold start fuel, the main tank is switched on with the fuel contained in the alcohol. The disadvantage here is that both tanks require a separate filling, ie supply lines to the body outside and u. U. separate tank flaps must be provided. The driver also has to monitor the fuel level in both tanks in order to be able to top up in time. Furthermore, it must distinguish between two separate filler neck, which can lead to incorrect filling of the two tanks if ignored.

In addition, cold-start systems for motor vehicles which can be operated with high alcohol content in fuel are already known, which heat the fuel to higher temperatures by means of electrical energy from the vehicle electrical system (battery). The fuel heating in the injector or in the fuel rail can be done by means of a resistive or inductive heating principle.

In the DE 10 2008 056 892 A1 a fuel supply device for assisting a cold start of an internal combustion engine designed for operation with alcohol or alcohol / gasoline mixed fuels, with an injection rail in which pressurized alcohol or alcohol / gasoline mixed fuel for the cold start of the internal combustion engine can be stored and with injectors, each having an electric heating device for heating the alcohol or alcohol / gasoline Have mixed fuel and communicate with the injection rail, so that the injectors can be supplied with the stored alcohol or alcohol / gasoline blended fuel. The injectors are designed as self-opening pressure relief valves that open when reaching a predetermined pressure in the injection rail and measure alcohol or alcohol / gasoline mixed fuel cylinder individually in an intake of the internal combustion engine. Further, in this document a method for controlling a fuel supply system for this internal combustion engine is described, wherein in the presence of a signal, which suggests an imminent start of the internal combustion engine, the main fuel pump is activated and is closed when satisfying at least one cold start condition for the internal combustion engine to a cold start and the heaters are activated. After a predetermined period of time and in the presence of a further signal, which confirms the presumed upcoming start of the internal combustion engine, the fuel pump of the fuel supply device is driven such that the pressure in the injection rail reaches the opening pressure of the injectors.

From the JP 57-052665 For example, a heater for heating an intake pipe is known, wherein the heater is controlled in accordance with the output of an alcohol concentration sensor, and in which the heat generation amount of the heater increases as the alcohol concentration becomes or becomes greater than a reference value.

If the heater for the fuel from individual, the respective cylinders associated electrical heaters, for example in the form of heated injectors, so in the case of a defective heater or in the worst case of multiple defective heater, the fuel for or for the corresponding cylinder is not heated and Formation of an ignitable mixture in or in the cylinders is not possible. The unburned fuel can lead to a break in the lubricating film between the piston and the cylinder wall of the cylinder (s) concerned, and because of the cold fuel there is an increased input of fuel into the lubricating oil of the internal combustion engine.

In the DE 602 03 659 T2 For example, there is described a method of detecting a failure of heaters provided in a fuel supply system of an internal combustion engine for heating an injection fuel. The method comprises the step of detecting the failure based on a change occurring at least in a parameter relating to the operating conditions of the internal combustion engine due to the injected fuel that has not been heated to a predetermined degree of heating.

The invention has for its object to provide a method and apparatus for operating a working with alcohol and alcohol blending fuels internal combustion engine, which ensure a safe and low-emission start of the internal combustion engine even at high alcohol levels in the fuel and low outside temperatures.

This object is achieved according to the features of the independent claims. Advantageous developments and refinements of the invention are specified in the dependent claims.

The invention is characterized by a method and a corresponding apparatus for operating a spark-ignited internal combustion engine having a plurality of cylinders operating with alcohol or alcohol mixed fuels, the cylinders being assigned cylinder-individual, electrical heating devices for heating the fuel. Upon satisfaction of a criterion indicative of an imminent startup of the internal combustion engine and upon satisfaction of a criterion indicative of a cold start of the internal combustion engine, the cylinder-individual heaters are activated. Each of the cylinder-specific heaters is checked for proper function. In case of a detected defect of a heater, the fuel supply to the cylinder is locked to which the defective heater is assigned. The internal combustion engine is started with a reduced by the number of defective heaters number of cylinders. During operation of the internal combustion engine, at least one variable which correlates with the temperature of the internal combustion engine is monitored. If a predetermined threshold value for the at least one correlating variable is exceeded, the fuel supply to the cylinder to which the defective heating device is assigned is released and the heating devices are deactivated.

According to the invention, the activation of the heating device and the diagnosis of the heating devices are coupled to events which, seen in terms of time, are still before the start of the internal combustion engine.

With the method according to the invention, it is firstly possible to significantly reduce the time for heating up the fuel and thus the waiting time for the driver of the motor vehicle until he can safely start the internal combustion engine. On the other hand, a diagnosis of the cylinder-specific electrical heating devices is carried out before the start of the internal combustion engine. Thus, it is possible that in the case of a detected defect in one or more heating devices, measures can be taken to prevent cylinders from being supplied with cold fuel as a result of the absence of a preheated fuel and an ignitable mixture not being present in the combustion chamber. By blocking the fuel supply to those cylinders, which is assigned to a defective heater, no fuel is introduced into the lubricating oil and a demolition of the lubricating film between the piston and the cylinder wall is reliably prevented.

According to an advantageous embodiment, a cold start of the internal combustion engine is concluded when the coolant temperature of the internal combustion engine is below a threshold which is determined as a function of the alcohol concentration in the fuel. The electric heaters are activated only when it is necessary for a safe start of the internal combustion engine. Since the capacity of the electrical system of a motor vehicle is limited, this contributes to a relief of the electrical system.

By taking into account a temperature threshold value dependent on the alcohol concentration in the fuel, a very accurate determination is made as to when a preheating of the fuel must take place. This temperature threshold is stored in a preferred manner in a map of a memory of a control device controlling and / or regulating the internal combustion engine.

The fuel supply to the affected cylinders is released only when a, the temperature of the internal combustion engine representing size exceeds a predetermined threshold, d. H. the affected cylinders do not work until the higher temperature allows efficient combustion.

As a determining factor, when the previously blocked fuel supply to the affected cylinders will be released again, which is due to the fired cylinder adjusting temperature of the internal combustion engine, in particular the coolant temperature of the internal combustion engine used. If, in addition, the speed which is set by the starting process is included as a criterion, then a more precise time for connecting the fuel injection results.

Further embodiments and advantages of the invention will become apparent from the description of an embodiment which is explained in more detail below with reference to the drawing. Show it:

1 in a schematic representation of an operable with gasoline, alcohol or any mixing ratios of these fuels internal combustion engine with associated control device and

2 a flowchart for operating such an internal combustion engine.

The 1 shows a schematic representation of an operable for both gasoline, alcohol and with any mixing ratios of these fuels internal combustion engine 10 a motor vehicle. Such vehicles are referred to as flexible fuel vehicles (FFV) or variable fuel vehicles (VFV).

When the term fuel is used below, it refers to a fuel which consists either of pure gasoline (Otto fuel), of a mixture of any proportions of gasoline and alcohol or of pure alcohol, in particular of pure ethanol (E100).

In the 1 only the necessary components for understanding the invention are shown. In particular, the necessary for the ignition of the fuel / air mixture ignition device (spark plug and corresponding control) is omitted. The invention is based on an internal combustion engine 10 with 4 cylinders Z1-Z4 explained, but it is also applicable to internal combustion engines with other cylinder number ≥ 3.

The internal combustion engine 10 is an intake tract 11 and an exhaust tract 12 assigned, by means not shown inlet valves and exhaust valves with the combustion chambers of the cylinders Z1-Z4 of the internal combustion engine 10 keep in touch. The internal combustion engine 10 gets over the intake tract 11 supplied to the combustion of the fuel / air mixture fresh air needed. The resulting due to the combustion of the fuel / air mixture exhaust gases are in one, in the exhaust tract 12 arranged, not shown exhaust aftertreatment device cleaned and get over a, also not shown muffler into the environment.

To start the internal combustion engine 10 a starting device is provided which, inter alia, an electric starter 46 , one the starter 46 vehicle battery supplying electric power 35 , as well as a starter switch 31 includes.

The internal combustion engine 10 has a fuel supply system, which includes a fuel tank 13 and an electrically driven low pressure fuel pump 14 which has fuel from the fuel reservoir 13 via a low-pressure fuel line 15 to a fuel rail 18 promotes. Each cylinder Z1 to Z4 of the internal combustion engine 10 has its own intake manifold, each with a fuel injector 19 is assigned, with the help of which fuel can be injected into the individual intake manifolds. The individual injectors 19 are on unspecified lines with the fuel rail 18 in fluid communication. As the operating behavior of the internal combustion engine 10 is largely dependent on the type and composition of the fuel used is in the fuel supply system, an alcohol concentration sensor 26 provided, which detects the proportion of alcohol in the fuel ALC_KONZ. In the embodiment according to 1 is this alcohol concentration sensor 26 in the low pressure fuel line 15 arranged. Alternatively, the alcohol concentration in the fuel may also be modeled using operating parameters of the internal combustion engine 10 , So from already existing measures, for example, by using the signal in the exhaust system 12 the internal combustion engine 10 arranged exhaust gas sensor 28 to be determined, as for example in the US 6,257,174 B1 is described.

To start the internal combustion engine 10 When operating with a fuel with a high alcohol content even at low outside temperatures to ensure safe, an electric heating system for the fuel is provided, which is described in more detail below.

Each of the individual fuel injectors 19 is with an electric heater 20 Mistake. The electric heaters 20 can do this at the respective injectors 19 for example, in the form of a heating coil, heating mat, heating coil be mounted or in the injectors 19 be integrated as it is in the DE 10 2006 058 881 A1 is specified. There is a nozzle assembly for an injection valve disclosed with a nozzle body having a extending in the direction of a longitudinal axis nozzle body recess which is hydraulically coupled to a fluid supply, an axially movable in the Düsenkörperausnehmung nozzle needle in a closed position, a fluid flow through at least one injection port prevents and otherwise releases the fluid flow, and an inductively heatable heating element, which is arranged between the nozzle body and the nozzle needle, wherein the heating element is at least partially spaced from the nozzle body and the nozzle needle, and the DUsenkörper a facing side of the heating element and a The nozzle needle facing side of the heating element during the operation of the injection valve can be flowed by the fluid.

Alternatively, the individual electric heaters 20 also in the individual connecting lines between the fuel rail 18 and the individual injectors 19 be arranged.

For the method and the device, it is not important, as the individual electric heaters 20 are configured and according to which principle (resistive or inductive heating principle) they work, it must only be ensured that a cylinder-specific heating of the fuel takes place.

In one embodiment of the invention, each fuel injector 19 with a temperature of the fuel in the respective fuel injector 19 detecting temperature sensor 21 Mistake. Alternatively, these temperatures may be due to a change in the material properties of the fuel injectors 19 be determined.

For controlling and / or regulating the electric heating devices 20 is a heater controller 30 (HCU, Heating Control Unit). The heating control device 30 contains a computing unit 36 that with a program memory 37 and a value memory 38 (Data memory) is coupled. The arithmetic unit 36 , the program memory 37 and the value memory 38 may each comprise one or more microelectronic components. Alternatively, these components may be partially or fully integrated in a single microelectronic device. In the program memory 37 or the value memory 38 programs or values stored for the operation of the heaters 20 are necessary. In particular, a method for adjusting the heating power and for checking the proper operation of the individual heating devices 20 implemented before and / or during operation of the internal combustion engine 10 from the arithmetic unit 36 be worked off, as it is based on the 2 will be explained in more detail.

For this purpose, the heating control device 30 including the signals of the temperature sensors 21 for the fuel, the signal TKW of a coolant temperature sensor 25 the internal combustion engine 10 , the rotational speed N of the internal combustion engine 10 , which from the signal of a crankshaft angle sensor 27 is derived, the ALC_KONZ signal of the alcohol concentration sensor 26 and optionally evaluated further parameters, as determined by the 2 will be explained in more detail.

The heating control device 30 is with the ignition switch 31 connected, which releases the ignition in position I and the position II Starting device 46 for starting the internal combustion engine 10 , for example, an electric starter activated.

With the reference number 32 is an electrical switching element referred to, its activation as an indication of a possibly imminent starting operation of the internal combustion engine 10 can be interpreted. This may be the signal of a switch arranged on the door lock of the driver's door or a door-opening contact which, for example, also activates the interior lighting of the passenger compartment. If the driver's seat is equipped with a sensor device for seat occupancy recognition, then the signal of this sensor can also be used.

If the vehicle has a so-called keyless, active or passive access system, the signal for opening and closing doors of the internal combustion engine can be heard 10 driven motor vehicle serving, mobile identification transmitter are used. In the simplest case, the operation of the transmitter of a radio remote control for central locking of the doors and the trunk as an indication of a possibly imminent starting operation of the internal combustion engine 10 be interpreted. In the 1 is such a transmitter with the reference numeral 33 and the associated vehicle-side receiver with the reference numeral 34 characterized.

The mentioned facilities 32 . 33 . 34 allow the individual heaters 20 the injectors 19 already to activate and a diagnosis of the heaters 20 perform before the driver of the motor vehicle, the ignition-start switch 31 or a start-stop button for starting the internal combustion engine actuated.

Furthermore, the heater control device 30 connected to a voltage source, preferably with the vehicle battery 35 of the electrical system. It supplies, inter alia, via power output stages, not shown, the electrical energy for the starting device 46 and for the heaters 20 ,

For controlling and regulating the internal combustion engine 10 is an engine control unit (ECU) 24 provided, which via an electrical connection with the heating control device 30 , preferably by means of a CAN bus 40 connected is. As a result, signals and data can be exchanged bidirectionally, in particular input signals from sensors that are directly connected to the heating control device 30 are fed, including the engine control device 24 for further processing. Similarly, input signals from sensors directly to the engine control unit 24 are also supplied to the heating control device 30 for further processing. In addition, you can use this CAN bus 40 other operating variables and / or calculated sizes are exchanged.

The engine control device 24 Additional sensors are assigned, which record different measurands and determine the measured value of the measurand. Operating variables include not only the measured quantities but also variables derived therefrom. The engine control device 24 determined depending on at least one of the measured variables and / or the operating variables manipulated variables, which are then converted into one or more actuating signals for controlling actuators by means of corresponding actuators.

The sensors are for example the temperature sensor 25 for the coolant temperature TKW, the crankshaft angle sensor 27 which detects a crankshaft angle to which a rotational speed N is then assigned, the alcohol concentration sensor 26 , an air mass meter serving as a load sensor 23 and the exhaust gas sensor 28 in the exhaust tract 12 and more, for the operation of the internal combustion engine 10 necessary sensors that are not explicitly shown and whose signals are generally indicated by the reference symbol ES.

The actuators are for example a throttle valve 29 in the intake tract 11 , the fuel injectors 19 and the low pressure fuel pump 14 , Other signals for other actuators that operate the internal combustion engine 10 are necessary, but not shown explicitly, are generally designated by the reference symbol AS.

The engine control device 24 contains a computing unit in a known manner 41 that with a program memory 42 and a value memory 43 (Data memory) is coupled. In addition, a non-volatile storage of errors determined by means of various diagnoses, for example the on-board diagnosis, is an error memory 44 provided with an error indicator 45 is coupled.

Among other things, the engine control unit determines 24 as a function of a load signal L and the rotational speed N, taking into account the alcohol content ALC_KONZ in the fuel, the appropriate ignition timing and the injection period.

In the program memory 42 or the value memory 43 Programs or values are stored, which are for the operation of the internal combustion engine 10 are necessary. In the value memory 43 are, among other maps KF1, KF2 and various Threshold values are stored, whose meaning is based on the description of the 2 will be explained in more detail. Further, in the engine control device 24 a time counter (timer) 47 whose function is also based on the description of the 2 will be explained in more detail.

In one embodiment of the invention, the heating control device 30 also in the engine control device 24 be integrated.

The 2 shows in the form of a flowchart a method for operating the internal combustion engine during the starting process.

The method is started in step S0, in which variables are initialized if necessary and counter readings are reset.

In the subsequent step S1, it is checked whether at least one criterion is met, that for an imminent start of the internal combustion engine 10 is indicative (start request signal SA). As a criterion or indication, a start of the internal combustion engine 10 is likely to appear, for example, the touching or pressing the door handle of the driver's door can be used by a person. Also, by evaluating the signal of a switch arranged on the door lock of the driver's door or a door opening contact, which, for example, also activates the interior lighting of the passenger compartment, can be interpreted as an indication of a possibly imminent start of the internal combustion engine.

If the driver's seat is equipped with a sensor device for seat occupancy recognition, a signal generated by this sensor device can also be used as an indication of a possibly imminent start of the internal combustion engine 10 be interpreted.

Does that with the internal combustion engine 10 powered vehicle on a so-called keyless entry system, as the activation of the transmitter of serving for opening and closing the doors of the vehicle radio remote control or remote key as an indication of a possibly imminent starting operation of the internal combustion engine 10 be used. The signal of a radio remote control for opening a garage door, in which the vehicle is parked or parked in front of it, can be used as an indication of an imminent start of the internal combustion engine 10 be interpreted.

If none of these mentioned criteria or indications is fulfilled and thus there is no start request signal SA, the query in step 51 , possibly repeated after a predetermined waiting time t_WAIT, until the query returns a positive result.

However, if there is an indication in step S1 that is due to an imminent start of the internal combustion engine 10 If the engine control unit (ECU) is 24 and the heating control device (HCU) 30 activated, that is put from a sleep mode in the operating mode and it is queried whether a heating of the fuel is necessary (step S2). A heating of the fuel is particularly necessary if the fuel has a high alcohol content and low outside temperatures prevail, since alcohol evaporates very poorly at low temperatures and thus a cold start of the internal combustion engine 10 difficult or even impossible.

In particular, the temperature of the coolant TKW and the alcohol component ALC_KONZ in the fuel are used in the step S2 for deciding whether heating of the fuel is necessary.

If the temperature of the coolant TKW, which in very good approximation, the temperature of the internal combustion engine 10 reflects, below a predetermined threshold TKW_SW1, so must the heating devices 20 to be activated. Because the temperature at which still a safe cold start of the internal combustion engine 10 can be carried out, depends on the alcohol content ALC_KONZ in the fuel, this threshold TKW_SW1 depends on the alcohol content ALC_KONZ in a map KF1 within the value memory 43 the engine control device 24 stored. The higher the alcohol content ALC_KONZ in the fuel, the more the threshold value TKW_SW1 shifts, from which the heating devices start 20 must be activated, to higher temperatures.

The KF1 the map KF1 by means of tests on the test bench by varying the coolant temperature TKW and the alcohol concentration ALC_KONZ in the fuel and then carried out attempts to start the internal combustion engine.

The value for the temperature of the coolant TKW becomes from the signal of the temperature sensor 25 , the value of the alcohol content ALC_KONZ becomes from the signal of the alcohol concentration sensor 26 receive. However, both values can also be determined indirectly from other parameters by means of calculations and / or modeling.

If the coolant temperature TKW is above a second threshold value TKW_SW2, wherein this value is significantly higher than the threshold value TKW_SW1 dependent on the alcohol concentration, it is assumed that heating of the fuel is no longer necessary, regardless of the alcohol content ALC_KONZ. This threshold value TKW SW2 is also determined empirically and is in the value memory 43 stored.

If the query in step S2 shows that no heating of the fuel is necessary, then in a step S3, a "conventional start" of the internal combustion engine 10 initiated. In this context, "conventional starting" is to be understood as meaning that conditions exist that start the internal combustion engine 10 allow additional heating measures for the fuel to be taken. The process is then ended with step S14.

If the query in step S2, that for a proper start of the internal combustion engine 10 a heating of the fuel is necessary, in a step S4 via signals of the heating control device 30 (HCU) the individual, provided according to the number of cylinders Z1-Z4 heaters 20 controlled, ie supplied with electrical energy. Subsequently, it is checked in a step S5 whether all the heaters 20 work properly.

To check the individual electric heaters 20 Any of the well-known from the prior art method can be used. In this case, by detecting and evaluating the to the electric heaters 20 applied electrical voltage, the thereby adjusting electric current, the recorded electrical power, among other things, both an open circuit (open circuit) and a short circuit or insufficient heating power are closed.

If the query in step S5 shows that all cylinder-specific heating devices 20 function properly, it is checked in a subsequent step S6, whether the heating of the fuel can be stopped again, or whether still needs to be heated. As a criterion, either the means of the time counter 47 obtained time span t_AH since activation of the heaters 20 or that of the individual temperature sensors 21 at the injectors 19 delivered temperature signals are evaluated. If the time span t_AH is equal to or longer than a predefined threshold value t_AH_SW, which depends on the coolant temperature TKW and the alcohol concentration ALC_KONZ in the value memory 43 the control device 24 is stored, so a further heating of the fuel is no longer necessary and the power supplies for the heaters 20 are turned off in a step S7. Alternatively, the power supplies for the heaters 20 shut off when the of the temperature sensors 21 supplied signals in the value memory 43 the control device 24 exceeded threshold T_KST_SW.

In a subsequent step S8, the internal combustion engine 10 Even at low coolant temperatures TKW and high alcohol concentrations ALC_KONZ be safely started in the fuel, without causing start-up difficulties.

If the query in step S5 but a negative result, that is, at least one of the total existing, cylinder-specific heating devices 20 is defective, so in a step S9 cylinder-specific fuel allocation for those cylinders prevented that the defective (s) heating device (s) 20 is assigned or are. In addition, the presence of a defective heater 20 indicating the cylinder of this heater 20 is assigned to the fault memory 44 registered and this optionally also the leader of the internal combustion engine 10 powered vehicle acoustically and / optically by means of the fault indicator 45 notified (step S9 ').

For a start of the internal combustion engine to be performed 10 Thus, the one or those injectors is not supplied with fuel and thus no fuel supplied to the corresponding cylinders Z1-Z4 and the internal combustion engine 10 will be in the presence of defective heaters 20 only with one of the number of defective heaters 20 operated smaller number of cylinders (step S10).

It should be noted that only a maximum number of defective heaters 20 may occur to even a safe and stable start of the internal combustion engine 10 to ensure. In an internal combustion engine 10 with 3 cylinders a maximum of one heater is allowed 20 be defective, in a combustion engine with 4 cylinders a maximum of 2 heaters 20 be defect. Generally, the more heaters 20 may fail, the more cylinders the internal combustion engine 10 having.

After the internal combustion engine 10 was started with a reduced number of fired cylinders Z1-Z4, the temperature of the coolant TKW of the internal combustion engine is continuously 10 and the rotational speed N of the internal combustion engine 10 supervised.

In a step S11 it is checked whether the coolant temperature TKW of the internal combustion engine 10 a predetermined threshold TKW_SW3 and the speed N of the internal combustion engine 10 has reached a predetermined threshold N_SW. Only when both threshold values TKW_SW3, N_SW are exceeded are the cylinders deactivated in step S9 by inhibiting fuel supply switched on again in a step S12, that is, the fuel injection by driving the corresponding injectors 19 also released again for these cylinders (step S12). The two threshold values TKW_SW3, N_SW are determined by tests and are in the value memory 43 the engine control device 24 stored.

In a simpler process variant can on the review of the speed curve of the internal combustion engine 10 be dispensed with during the starting with a limited number of cylinders, since the main criterion when the deactivated cylinders can be switched on again, the coolant temperature TKW the internal combustion engine 10 represents. If only the rotational speed N is evaluated, it may happen that the threshold value N_SW is exceeded, but the previously deactivated cylinders are still too cold, so that, despite the speed reached, an increased entry of lubricating oil into the crankcase and / or a breakdown of the lubricating film between piston and cylinder wall can not be excluded.

Since now the starting process of the internal combustion engine 10 is successfully completed, a further heating of the fuel is no longer necessary and in step S13 are the power supplies for the heaters 20 turned off and the process is completed in step S14.

The invention has been explained with an example in which the engine control device 24 and the heater control device 30 are shown as separate components. But it is also possible, the heating control device 30 with the associated output stages for the heaters 20 completely in the engine control device 24 to integrate or integrate only the control electronics and the power amplifiers for the heaters 20 to arrange externally.

LIST OF REFERENCE NUMBERS

10

Internal combustion engine

11

intake system

12

exhaust tract

13

Fuel tank

14

Low-pressure fuel pump

15

Low-pressure fuel line

18

Fuel rail

19

fuel injector

20

electric heater

21

Temperature sensor injector

23

Air mass meter, load sensor

24

Engine control unit (ECU)

25

Temperature sensor coolant

26

Alcohol concentration sensor

27

Crank angle sensor

28

exhaust gas sensor

29

throttle

30

Heating control unit (HCU)

31

Ignition starter switch

32

electrical switching element

33

Transmitter of the radio remote control, mobile identification transmitter

34

Receiver of the radio remote control

35

Voltage source, vehicle battery

36

Computing unit HCU

37

Program memory HCU

38

Value memory, data memory HCU

40

CAN bus

41

Arithmetic unit ECU

42

Program memory ECU

43

Value memory, data memory ECU

44

error memory

45

Error display device

46

Starting device of the internal combustion engine

47

Time counter, timer

ALC_KONZ

Alcohol content in the fuel, alcohol concentration

AS

Output signals, control signals

IT

input signals

KF1, KF2

map

L

load signal

N

rotation speed

N_SW

Threshold for speed

SA

start request

S0..S14

step

T_KST_SW

Threshold fuel temperature

TKW

Coolant temperature

TKW_SWi

Threshold coolant temperature

T_WAIT

Waiting period

t_AH

Time since activating the heaters

t_AH_SW

Threshold for time since activation of the heaters

Z1-Z4

Cylinder of the internal combustion engine

Claims (12)

Method for operating a spark-ignited internal combustion engine working with alcohol and alcohol mixed fuels ( 10 ) with a plurality of cylinders (Z1-Z4), wherein the cylinders (Z1-Z4) are cylinder-specific, electrical heating devices (Z1-Z4) 20 ) are assigned to the heating of the fuel, and upon fulfillment of a criterion (SA), which for an impending start of the internal combustion engine ( 10 ) is indicative and when a criterion (TKW_SW1) is met, which is based on a cold start of the internal combustion engine ( 10 ), the cylinder-specific heating devices ( 20 ) are activated, characterized in that - each of the cylinder-specific heating devices ( 20 ) is checked for proper functioning, - in the event of a defect in a heating device ( 20 ) the fuel supply to the cylinder (Z1-Z4) is blocked, the defective heater ( 20 ), - the internal combustion engine ( 10 ) with a number of defective heaters ( 20 ) reduced cylinder number (Z1-Z4) is started, - during operation of the internal combustion engine ( 19 ) at least one, with the temperature of the internal combustion engine ( 10 ) is monitored at a predetermined threshold value (TKW_SW3, N_SW) for the at least one correlating variable (TKW, N), the fuel supply to those cylinders (Z1-Z4), where the defective heater ( 20 ) and - the heaters ( 20 ) are disabled. A method according to claim 1, characterized in that on a cold start of the internal combustion engine ( 10 ) is closed when the coolant temperature (TKW) of the internal combustion engine ( 10 ) is below a threshold (TKW_SW1), which is determined depending on the alcohol concentration (ALC_KONZ) in the fuel. Method according to one of the preceding claims, characterized in that the correlating variable the coolant temperature (TKW) of the internal combustion engine ( 10 ). A method according to claim 3, characterized in that the correlating quantity in addition the rotational speed (N) of the internal combustion engine ( 10 ). Method according to one of the preceding claims, characterized in that as a criterion for an imminent start of the internal combustion engine ( 10 ) Touching or pressing the door handle of the driver's door of the internal combustion engine ( 10 ) driven motor vehicle is used. Method according to one of claims 1-4, characterized in that as a criterion for an imminent start of the internal combustion engine ( 10 ) the signal on a door lock of the driver's door of the internal combustion engine ( 10 ) driven motor vehicle arranged switch or a door opening contact is used. Method according to one of claims 1-4, characterized in that as a criterion for an imminent start of the internal combustion engine ( 10 ) the signal of a sensor device for detecting the seat occupancy of the driver's seat of the internal combustion engine ( 10 ) driven motor vehicle is used. Method according to one of claims 1-4, characterized in that as a criterion for an imminent start of the internal combustion engine ( 10 ) the signal for opening and closing doors of the internal combustion engine ( 10 ) powered motor vehicle serving mobile identification transmitter ( 33 ) is used. Method according to one of the preceding claims, characterized in that in the case of a detected defect of a heating device ( 20 ), indicating the relevant cylinder (Z1-Z4) a corresponding entry in a fault memory ( 44 ) one of the internal combustion engine ( 10 ) controlling and / or regulating engine control device ( 24 ) he follows. Device for operating a spark-ignited internal combustion engine working with alcohol and alcohol mixed fuels ( 10 ) with a plurality of cylinders (Z1-Z4), wherein the cylinders (Z1-Z4) are cylinder-specific, electrical heating devices (Z1-Z4) 20 ) are assigned to the heating of the fuel, and upon fulfillment of a criterion (SA), which for an impending start of the internal combustion engine ( 10 ) is indicative and when a criterion (TKW_SW1) is met, which is based on a cold start of the internal combustion engine ( 10 ), the cylinder-specific heating devices ( 20 ) are activated, wherein the device is adapted to perform a method according to one of claims 1 to 9. Apparatus according to claim 10, characterized in that the electrical heating devices ( 20 ) on or in the individual injectors (Z1-Z4) associated fuel injectors ( 19 ) are arranged. Apparatus according to claim 10, characterized in that the electrical heating devices ( 20 ) or in which the individual fuel injectors ( 19 ) with a fuel rail ( 18 ) connecting lines are arranged.

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