DE102013220605B3 - Method and device for operating an internal combustion engine working with alcohol and alcohol mixed fuels - Google Patents

Abstract

A method and a device for operating a spark ignition internal combustion engine working with alcohol and alcohol mixed fuels with at least one heating device for heating the fuel and a heating control device for controlling and / or regulating the heating power of the heating device are described. If a criterion that is indicative of an impending start of the internal combustion engine is met and if a criterion that indicates a cold start of the internal combustion engine is met, the heating control device is activated. Depending on the actuation or non-actuation of an ignition and starting device for the internal combustion engine, different temperature setpoints (T_SP_LOW, T_SP_HIGH, T_SP_ST) are set for the fuel by means of the heating control device. The temperature setpoint (T_SP_HIGH) when the ignition is switched on and the starter device of the internal combustion engine is not actuated is higher than the temperature value (T_SP_LOW) when the ignition is switched off. The temperature setpoint (T_SP_ST) when the ignition is switched on and the starter device is activated is higher in relation to the temperature setpoint (T_SP_HIGH) when the ignition is switched on and the starter device is not actuated.

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 heating device for heating the fuel and a heating control device for controlling and / or regulating the heating power of the heating device.

Vehicles are known which can be used with either alcohol or mixed alcohol fuels, d. H. can be operated with fuels with variable alcohol contents, as well as with petrol fuel (gasoline). 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). Common alcohol mixtures are for example M85, d. H. 85% methanol in the fuel and E85, d. H. 85% ethanol in the fuel, in which the gasoline content is therefore 15% each. In particular, in the Brazilian market motor vehicles are operated, in which pure ethanol (E100) is used as fuel.

The use of such mixed fuels with high alcohol contents has the disadvantage that the vehicle is difficult to start at low temperatures, since alcohol evaporates very poorly at low temperatures. For vehicles fueled with 100% ethanol, for example, starting below + 12 ° C (flashpoint ethanol) is almost impossible. Thus, since cold start problems occur without special precautions, vehicles that allow operation with very high alcohol concentrations in the fuel, small, built-in fuel additive container carried a small amount of starting fuel, eg. B. Brazilian gasoline ("Gasohol", E20 fuel) include. To start the vehicle below certain outside temperatures, gasoline is then used as starting fuel or injected in addition to the alcohol to form a combustible mixture. The problem here, however, is that in a cold start always very small amounts of fuel are taken from the additional container containing the starting fuel and in the course of time this starting fuel is getting worse. By "worse" is meant in this context that the volatile hydrocarbon fractions such as propane and butane, by 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 when no starting fuel is needed , evaporate slightly and escape from the additional tank. The necessary components for a cold start are then lost or at least considerably reduced. Under certain circumstances, no cold start can be performed.

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. Also, the driver must track the fuel level in both tanks in order to refill them in time. Furthermore, it must distinguish between two separate filler neck, which can lead to incorrect filling of the two tanks if ignored.

From the DE 25 36 432 A1 an internal combustion engine is known, which is operable with alcohol and alcohol-mixed fuels and in which in a main mixing means bypassing Nebenansaugkanal a cold start device is provided with an electrically operated heater. The necessary air for the cold start mixture is diverted from the main air intake duct, wherein the flow connection can be interrupted by a shut-off device. Warming up the fuel-air mixture improves the start-up capability of the internal combustion engine at low ambient temperatures.

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 is described 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 heater for heating the alcohol or alcohol / gasoline mixed fuel and are in communication with the injection rail, so that the injectors with the stored alcohol or alcohol / gasoline mixed fuel can be supplied. 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 engine. Furthermore, 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 impending 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 assumed imminent 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 DE 39 03 234 A1 is a device for controlling the Ansauggemischtemperatur an internal combustion engine, especially in motor vehicles known. The device has at least one Ansauggemischtemperaturfühler, a controller that receives the sensor output signal and controls depending on the sensor output signal and a target temperature of the Ansauggemisches an adjusting device for influencing Ansauggemischtemperatur on. For a simple and cost-effective adaptation of the intake mixture temperature to operating conditions of the internal combustion engine, at least one further sensor for measuring at least one operating variable of the internal combustion engine is provided, which influences the setpoint temperature depending on the measured operating variables.

The AT 411 484 B shows a cold start device operated with alcohol or alcohol blending fuels internal combustion engine with external mixture formation and spark ignition, which has an electric heating element, which is acted upon via a cold start valve with fuel. To minimize the heating power of the heating element is provided that at least one Verdaßfungskammer is provided, in which the cold start valve opens and in which the electric heating element is arranged, that each evaporation chamber to at least one inlet channel of the internal combustion engine has a flow connection, and that the evaporation chamber has a channel for has the air supply.

From the JP S57-52665A 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.

All these electric heating systems have the disadvantage that they require a certain heating time, which depends in particular on the coolant temperature of the motor vehicle before the starting process of the internal combustion engine and not an arbitrary amount of power for the heating systems can be removed from the electrical system.

This preheating or heating of the electric heating systems represents a not negligible loss of comfort compared to the cold start systems with an additional tank for a starting fuel.

The object of the invention is to provide a method and a device for operating a working with alcohol or alcohol-mixed fuels internal combustion engine, which ensures even at low temperatures and very high alcohol levels in the fuel quick start of the internal combustion engine and not the vehicle electrical system is excessively burdened.

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

The invention is characterized by a method and a corresponding device for operating a spark-ignited internal combustion engine operating with alcohol or alcohol mixed fuels with at least one heating device for heating the fuel and a heating control device for controlling and / or regulating the heating power of the at least one heating device. 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 heater control device is activated. Depending on the operation or non-operation of an ignition device for the internal combustion engine, different temperature target values for the fuel are set by the heater controller. The temperature setpoint when the ignition is switched on and the starting device of the internal combustion engine is not actuated is higher in relation to the temperature setpoint when the ignition is switched off. The temperature setpoint when the ignition is switched on and actuated Starting device is selected higher in relation to the temperature setpoint with the ignition switched on and the starting device not actuated.

With the method according to the invention, it is possible, on the one hand, to significantly reduce the time for heating the fuel and thus the waiting time for the driver of the motor vehicle until he can safely start the internal combustion engine, which increases the comfort over known heating systems with constant heating power.

Upon occurrence of certain events indicative of an imminent cold start of the internal combustion engine, the fuel is heated to a first, relatively low temperature setpoint. This first temperature setpoint is chosen so that no vapor bubble formation occurs in the fuel. A typical value is 60 ° C. If then after no start of the internal combustion engine within a first, predetermined period of time, because z. For example, if the driver has opened the car door but has not turned on the ignition, the heater will be deactivated again, d. H. switched off.

By choosing a low, first temperature target value at a time at which a start of the internal combustion engine is likely, but ultimately not sure that it is also carried out, an excessive load on the vehicle electrical system can be avoided.

If the ignition is switched on after such a preheating to the first, low temperature setpoint within the first time period, this is a stronger indication that a start of the internal combustion engine could be imminent. Therefore, the fuel is heated to a second, compared to the first temperature setpoint higher temperature setpoint, for example, to a value of 100 ° C.

If no start of the internal combustion engine, so the starting device is not activated within a second predetermined time since ignition "ON" because z. B. the driver has only turned on the ignition to listen to music by means of the car radio, it is controlled to the first, lower temperature setpoint and deactivated after the first period, the heater, d. H. switched off. This also helps to reduce the load on the vehicle electrical system.

Since in this case only the first temperature setpoint has to be heated to the second temperature setpoint after the ignition has been switched on, both a lower heating output and a shortened heating time compared with heating proceed from a low starting temperature up to the second temperature setpoint.

If the starter is also actuated within the first period of time, the fuel is heated to a third temperature set point, which is higher than the second set temperature value, for example to 120 ° C., whereby a safe and rapid start of the internal combustion engine is ensured even at low ambient temperatures. In this case, it is only necessary to heat from the second temperature setpoint to the third setpoint temperature, so that only a small amount of heating energy has to be supplied. This results in a shortened heating time compared to a heating starting from a low starting temperature up to the third temperature setpoint.

According to an advantageous embodiment, when the internal combustion engine is stopped, the ignition switched on and the starting device is not actuated, it is checked how often the ignition has been switched on without the starting device being actuated in between. When a predetermined threshold value for this number is exceeded, a temperature setpoint is selected which corresponds to the temperature setpoint when the ignition is switched off, since in this case it is not clear whether the driver intends to start the internal combustion engine at all. Such a procedure also contributes to the reduction of heating power and thus to a lower load on the vehicle siding.

According to a further advantageous embodiment, in a post-start phase after a successful start of the internal combustion engine, the temperature setpoint is reduced starting from the temperature setpoint when the ignition is switched on and the starting device is actuated with increasing time. This lowering of the temperature setpoint correlates with the increasing combustion chamber temperature and helps to relieve the vehicle electrical system.

A further relief of the vehicle electrical system results when after a period of time after a successful start of the internal combustion engine, the heating control device is completely deactivated. This period of time is advantageously determined depending on the temperature of the coolant at the start of the internal combustion engine, the alcohol content of the fuel and the air / fuel ratio. This ensures on the one hand that the internal combustion engine does not die off again after the start, but on the other hand is only heated as long as absolutely necessary.

According to a further advantageous embodiment, the temperature setpoint values for the fuel are determined as a function of the temperature of the coolant at the start of the internal combustion engine and the air / fuel ratio, resulting in a heat output optimally adapted to these boundary conditions.

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

According to further advantageous embodiments, the touch or actuation of the door handle of the motor vehicle driven by the internal combustion engine, the signal of a switch arranged on a door lock of the driver's door or a door-opening contact is used as a criterion for a possibly imminent start of the internal combustion engine. Since other functions, such as switching on the interior lighting are triggered in modern motor vehicles with the touch or actuation of the door handle or by opening the driver's door, resulting in a simple and cost-effective option for premature activation of the heater.

According to a further advantageous embodiment, the signal of a sensor device for detecting the seat occupancy of the driver's seat of the motor vehicle driven by the internal combustion engine is used as a criterion for a possibly upcoming start of the internal combustion engine. Since this signal is present in modern motor vehicles anyway, there is a cost-effective solution for premature activation of the heater.

If the motor vehicle is secured against unauthorized access with an active or passive access system, then the signal of a so-called mobile identification transmitter, in the simplest case the transmitter of a radio remote control for central locking, can be evaluated. Again, no additional components are needed.

An embodiment of the invention is explained in more detail below with reference to drawings. Show it:

1 in the form of a block diagram of an operable with gasoline, alcohol or any mixing ratios of these fuels internal combustion engine with associated control device,

2 a flowchart of a program for controlling the fuel system for 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 ignition device necessary for the ignition of the fuel / air mixture 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 a different number of cylinders and regardless of the nature of the engine concept, z. B. four-stroke gasoline engine, two-stroke engine or rotary engine.

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 purified in an exhaust aftertreatment device, not shown, and enter via a, also not shown muffler into the environment.

To start the internal combustion engine 10 a starting device is provided which, for example, an electric starter 46 , 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 connected. Each cylinder Z1 to Z4 of the internal combustion engine 10 is a separate fuel injector 19 assigned, with the aid of which fuel can be injected directly into the combustion chambers of the cylinders Z1 to Z4 and the this via 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 is in the fuel supply system, an alcohol concentration sensor 26 provided, which detects the proportion of alcohol in the fuel. 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 high-alcohol fuel, even at low temperatures, an electric fuel heating system is provided, as described in more detail below.

Each of the individual fuel injectors 19 is with an electric heater 20 and a temperature of the fuel in the respective fuel injector 19 detecting temperature sensor 21 Mistake. It is also possible to use only a single temperature sensor 21 at one of the fuel injectors 19 whose measured value is representative of the temperature of the fuel in all fuel injectors 19 is. Alternatively, the temperature may be determined via a change in the material properties of the fuel injectors. Alternatively or in addition to the heating of the fuel injectors 19 is an electric heater 22 in or on the fuel rail 18 arranged. If the heating system consists exclusively of the heater 22 at the fuel rail 18 , so is at her serving for detecting the fuel temperature temperature sensor 23 intended.

For controlling and / or regulating the described heating system is a heating control device 30 provided by means of which the heating powers for the heaters 20 . 22 can be varied so that set different fuel temperature setpoints. For this purpose, the heating control device 30 including the signals of the temperature sensors 21 . 23 for the fuel, the signal of a coolant temperature sensor 25 and the signal of the alcohol concentration sensor 26 evaluated, as it is based on the 2 will be explained in more detail.

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 are stored, which are for the operation of the internal combustion engine 10 are necessary. In particular, a method for heating the fuel is implemented before and during operation of the internal combustion engine 10 from the arithmetic unit 36 is processed, as it is based on the 2 will be explained in more detail. In the value memory 37 Amongst others, there are different setpoint values T_SP_LOW, T_SP_HIGH, T_SP_ST for the fuel temperature in the fuel injectors 19 or in the fuel rail 18 and stores a plurality of threshold values t_TEMP_SP_LOW, t_SP_LOW_SW, t_SP_HIGH_SW for durations. In the heating control device 30 are still two time counters 39A . 39B whose function is also based on the description of the procedure according to the 2 be explained in more detail.

The heating control device 30 is with the ignition switch 31 connected, the ignition of the internal combustion engine at position I. 10 releases and at position II a starting device 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 is 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 . 34 allow the heaters 20 . 22 already activate before the driver of the motor vehicle, the ignition-start switch 31 or a start / stop button is pressed.

Furthermore, the heater control device 30 with a voltage source 35 connected, preferably with the vehicle battery of the electrical system. It supplies, inter alia, via power output stages, not shown, the electrical energy for the heaters 20 . 22 ,

For controlling and regulating the internal combustion engine 10 is an engine control unit (ECU) 24 which is electrically connected to the heating control device 30 preferably by means of a CAN bus 40 connected is. This allows input signals from sensors directly 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, a crankshaft angle sensor 27 which detects a crankshaft angle to which a rotational speed N is then assigned, the alcohol concentration sensor 26 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.

Among other things, the engine control unit determines 24 in response to a load signal and the rotational speed N under evaluation of the signal of the alcohol concentration sensor 26 for the composition of 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 Among other things, 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.

The 2 shows in the form of a flow chart a method for controlling a cold start system within a fuel supply system of an internal combustion engine.

The method begins when at least one criterion is met, that for an imminent start of the internal combustion engine 10 is indicative (step S1). 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 as an indication of a possibly imminent starting operation of the internal combustion engine 10 be used. Also the signal A radio remote control for opening a garage door in which the vehicle is parked or parked in front of it may be indicative of an imminent start of the internal combustion engine 10 be interpreted.

If none of these mentioned criteria or indications is fulfilled, then the processing will be repeated, possibly after expiration of a predetermined waiting time t_WAIT in the step 51 continued.

Is in the step 51 an indication that is due to an imminent launch of the internal combustion engine 10 the engine control unit (ECU) 24 is activated and it is queried whether the use of a cold start system for heating the fuel is necessary (step S2). Such a cold start system is particularly necessary if the fuel has a high alcohol content, since alcohol evaporates very poorly at low temperatures and thus a cold start of the internal combustion engine 10 difficult or even impossible.

In detail, in step S2 for deciding whether the cold start system is needed, the temperature of the coolant TKW, the alcohol content ALC_AN in the fuel and a time interval t_ST after starting the internal combustion engine 10 used.

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 value TKW_SW, the cold start system must 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_AN in the fuel, this threshold TKW_SW is dependent on the alcohol content AL_CAN in a map KF1 within the value memory 43 the engine control device 24 stored. The higher the alcohol content ALC_AN in the fuel, the more the threshold value TKW_SW, from which the cold start system must be activated, shifts to higher temperature values.

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_AN is taken from the signal of the alcohol concentration sensor 26 receive. From these two values, the threshold values TKW_SW are empirically determined and stored in the map KF1.

Furthermore, it is checked in step S2, whether a predetermined time t_ST since the start of the internal combustion engine 10 has expired. For this purpose, a count of a anyway in the engine control device 24 existing and also for other tax and / or regulatory purposes serving time to start counter 44 queried. If this time interval t_ST determined in this way is greater than a predefined threshold value t_ST_SW, then it is assumed that the starting process of the internal combustion engine 10 successfully completed and stable. The cold start system is not or no longer needed and can thus be deactivated (step S3) and the process is over (step S20).

The threshold value t_ST_SW is determined empirically as a function of the temperature of the coolant TKW and of the alcohol portion ALC_AN and stored in a characteristic field KF2 within the value memory 43 the engine control device 24 stored. This means that for a certain coolant temperature TKW and a certain amount of alcohol ALC_AN in the fuel, one needs a corresponding period of time within which the cold-starting device must be activated.

If the query in step S2, that for a proper start of the internal combustion engine 10 Heating of the fuel is necessary, in a step S4, the heater control device 30 activated. This is preferably done via the CAN bus 40 ,

In a subsequent step S5, it is checked whether the internal combustion engine 10 is running, ie whether its speed is above a specified value (logical variable LV_ERU = 1). This is not the case during the first pass of the method and the method is continued in a step S6.

In step S6 it is queried whether the ignition of the internal combustion engine 10 is turned on. In a conventional, key-operated ignition starter switch 31 For this purpose, the position of the ignition key (position I, 1 ) (logical variable LV_IGK = 1).

If the ignition is not switched on (position 0, 1 ), the process proceeds to step S7. It is queried whether a given, by the time counter 39A determined time span t_SP_LOW has expired, that is greater than a predetermined threshold t_SP_LOW_SW. At the first pass of the procedure is the count of the counter 39A is still zero, ie it has not yet started and the method is continued with a step S8.

In step S8, a first desired value T_SP_LOW for the temperature to which the fuel is to be heated is specified. This setpoint T_SP_LOW depends on the temperature of the Coolant TKW at the start of the internal combustion engine 10 and the air-fuel ratio AFR in a map of the value memory 38 the heating control device 30 stored. By means of signals of the heating control device 30 become the heaters 20 the fuel injectors 19 and / or the heater 22 the fuel rail 18 activated, so that the predetermined, first temperature setpoint T_SP_LOW, for example 60 ° C is reached.

Compliance with the setpoint temperature is achieved with the help of temperature sensors 21 at the fuel injectors 19 or the temperature sensor 23 at the fuel rail 18 monitors and thereby regulating the heating power for the heaters 20 . 22 allows.

In a subsequent step S9, the count of the time counter 39A increases and the process continues with step S2. If the cold start system is still necessary, the engine is still not running and the ignition is still off, the steps S2, S4 to S9 are run through until it is first established in step S7 that the predetermined period t_SP_LOW, for example 30 seconds, has elapsed is. In this case, a branch is made to step S10, in which the power supplies of the heaters 20 respectively. 22 be switched off.

The above-described run of the method reflects the case again that although an indication of a possible start of the internal combustion engine 10 but within the given period of time t_SP_LOW then no attempt to start was made. This may occur, for example, when a person has opened the door of the vehicle but has not operated the ignition key because they only wanted to get something out of the vehicle or put it down there. In this case, no longer needs to be heated.

If, however, during the described run, the ignition is switched on in step S6 (position I of the ignition start switch) 31 . 1 ), ie the logical variable LV_IGK = 1, this is another, compared to the criteria in step 51 stronger indication that a possible start of the internal combustion engine 10 imminent. In a subsequent step S11, it is queried whether the ignition key has previously been brought into position I (logical variable LV_IGK _n-1 = 1). If this is the case (yes), it is queried in a subsequent step S13 whether the number of ignition key actuations (position 0 to position I) has exceeded a predetermined threshold value CTR_IGK_ON_SW. If the result of the query is positive, the method is continued in step S7. The threshold value CTR_IGK_ON_SW may be, for example, between 3 and 5 and is in the value memory 43 the engine control device 24 stored.

If the query results in a negative result (no) in step S11, then in a step S12 the count CTR_IGK_ON of the counter is obtained 45 increases and the process is also continued in step S13.

The queries in steps S11 and S13 are based on the idea that repeated actuation of the ignition key in position I and subsequent failure to actuate into position II, there is no serious intention to start the internal combustion engine. For example, the purpose of the ignition key was to turn on the radio or something similar. In this case, then the activation of the heaters 20 . 22 with a heating power that has a relatively low temperature, for example, the specified 60 ° C result or when exceeding the predetermined period of time, the complete deactivation of the heaters.

If, however, it was detected in step S13 that the ignition key was actuated either for the first time or repeatedly, but this number has not yet reached the threshold value CTR_IGK_ON_SW, a query is made in the following step S14 as to whether a predetermined one of the time counter 39B determined time period t_SP_HIGH has expired, that is greater than a predetermined threshold t_SP_HIGH_SW. The time counter 39B begins to start if it is determined in step S6 that the ignition is turned on. If the threshold value t_SP_HIGH_SW has not yet been reached, then a second desired value T_SP_HIGH, which is higher than the first desired value T_SP_LOW, is specified for the temperature to which the fuel is to be heated (step S15). This setpoint T_SP_HIGH is also dependent on the temperature of the coolant TKW when starting the internal combustion engine 10 and the air-fuel ratio AFR in a map of the value memory 38 the heating control device 30 stored. By means of signals of the heating control device 30 become the heaters 20 the fuel injectors 19 and / or the heater 22 the fuel rail 18 is activated, so that the predetermined, second temperature setpoint T_SP_HIGH, for example 100 ° C is reached.

Also, compliance with this increased setpoint temperature is using the temperature sensors 21 at the fuel injectors 19 or the temperature sensor 23 at the fuel rail 18 monitors and thereby allows control of the heating power.

In a subsequent step S16, the count of the time counter 39B increases and the process continues with step S2.

The specification of a, compared to the first setpoint T_SP_LOW increased setpoint T_SP_HIGH for the temperature is based on the fact that when the ignition is switched on (logical variable LV_IGK = 1) soon a starting operation of the internal combustion engine 10 is more likely than with the ignition off. If it really starts the internal combustion engine 10 comes, then the fuel is optimally heated and the starting process of the internal combustion engine 10 is successful even at low temperatures.

But even if the ignition is switched on and switched on only once, it may happen that the ignition starter switch 31 within the predetermined time t_SP_HIGH (query in step S14) is not moved to position II, so no start of the internal combustion engine 10 is initiated. After unsuccessful expiry of the time span t_SP_HIGH, for example 20 seconds, the method continues with step S7, which has already been explained.

This results in a lowering of the higher temperature setpoint T_SP_HIGH to the lower temperature setpoint T_SP_LOW, which is equivalent to a reduction in the heating power.

If it is determined in a renewed passage in step S5 that the internal combustion engine 10 is running (LV_ERU = 1), it is queried in a step S17 whether the internal combustion engine 10 still in the starting phase or in the post-start phase. The internal combustion engine 10 is in the post-start phase when the speed has exceeded a predetermined threshold, for example 1000 min ^-1 (logical variable LV_ST_END = 1), otherwise in the starting phase.

Is the internal combustion engine 10 still in the starting phase, when the starting device 46 is still activated, for example, an electric starter with the flywheel of the internal combustion engine 10 is still engaged, the method is continued with a step S18. In step S18, a third, compared to the first setpoint T_SP_LOW and second setpoint T_SP_HIGH again increased setpoint T_SP_ST for the temperature is set to which the fuel is to be heated.

This setpoint T_SP_ST is also dependent on the temperature of the coolant TKW at the start of the internal combustion engine 10 and the air-fuel ratio AFR in a map of the value memory 38 the heating control device 30 stored. By means of signals of the heating control device 30 become the heaters 20 the fuel injectors 19 and / or the heater 22 the fuel rail 18 is activated, so that the predetermined, third temperature setpoint T_SP_ST, for example 120 ° C is reached.

If the query in step S17 shows that the internal combustion engine 10 is located in the Nachstartphase, so due to the heating of the fuel, a successful start of the internal combustion engine 10 is completed, so are not directly the heaters 20 . 22 deactivated, but during the Nachstartphase the internal combustion engine 10 relevant setpoint value T_SP_AST is determined from the characteristic map for the setpoint value T_SP_ST by weighting this characteristic diagram as a function of the time span after start t_ST (step S19). With increasing time, the heating power and thus the temperature of the fuel is reduced. The longer the internal combustion engine 10 running, the less the fuel must be heated to ensure proper operation of the internal combustion engine 10 to ensure.

If it is subsequently determined in step S2 that the time duration t_ST has elapsed, for example 60 seconds have elapsed, heating of the fuel is no longer necessary, the heating devices 20 . 22 in step S3, the heating device is deactivated and the process is ended with step S20.

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 heating devices 20 . 22 completely in the engine control device 24 to integrate or integrate only the control electronics and the power amplifiers for the heaters 20 . 22 to arrange externally.

In the described embodiment, the motor vehicle on a conventional ignition starter switch with 3 positions (0-I-II) and for controlling the heating power, these switching positions are queried. However, the invention is also applicable to modern motor vehicles, where no key in the true sense must be plugged into a lock to activate the ignition and start the engine. In such, z. B. keyless-start or keyless-go systems, the presence of the "electronic key", also often referred to as a mobile identification transmitter, in the interior, the startup process is then sufficient by pressing a start-stop button. In this case, the signals of this Components evaluated to activate the heaters early.

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

Heater injectors

21

Temperature sensor injector

22

Heater fuel rail

23

Temperature sensor fuel rail

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

39A

Time counter for heating up when ignition off

39B

Time counter for heating on ignition

40

CAN bus

41

Arithmetic unit ECU

42

Program memory ECU

43

Value memory, data memory ECU

44

Time counter for time after start

45

Counter for actuation ignition

46

Starting device of the internal combustion engine

t

rotation speed

TKW

Coolant temperature

TKW_SW

Threshold coolant temperature

T_KST

Temperature of the fuel

T_SP_LOW

first setpoint for KST temperature

T_SF_HIGH

second setpoint for KST temperature

T_SP_ST

third setpoint for KST temperature

T_SP_AST

Setpoint for fuel temperature in post-start phase

IT

input signals

AS

Output signals, control signals

Z1-Z4

Cylinder of the internal combustion engine

AFR

Air-fuel ratio

KF1

map

KF2

map

T_WAIT

Waiting period

t_St

Time span after start of the internal combustion engine

t_ST_SW

Threshold for time after start of the internal combustion engine

t_SP_LOW

Time for heating up when ignition off

t_SP LOW_SW

Threshold for time limit for ignition during ignition off

t_SP_HIGH_SW

Threshold for time limit for ignition on ignition

ALC_AN

Alcohol content in the fuel

LV_ERU

Logical variable engine is running

LV_IGK

Logical variable ignition

LV_ST_END

Logical variable motor operation outside start

Claims (13)

Method for operating a spark-ignited internal combustion engine working with alcohol and alcohol mixed fuels ( 10 ), with at least one heating device ( 20 . 22 ) for heating the fuel and a heating control device ( 30 ) for controlling and / or regulating the heating power of the at least one heating device ( 20 . 22 ), wherein, when a criterion is met, which is responsible for an imminent start of the internal combustion engine ( 10 ) is indicative and when a criterion is met which is based on a cold start of the internal combustion engine ( 10 ), the heating control device ( 30 ) is activated, characterized in that - depending on the operation or non-actuation of an ignition and tempering device ( 31 . 46 ) for the internal combustion engine ( 10 ) different temperature setpoints (T_SP_LOW, T_SP_HIGH, T_SP_ST) for the fuel by means of the heating control device ( 30 ), wherein - the temperature setpoint (T_SP_HIGH) with the ignition switched on and a non-actuated starting device ( 31 . 46 ) of the internal combustion engine ( 10 ) is higher with respect to the temperature value (T_SP_LOW) when the ignition is switched off, - the temperature setpoint (T_SP_ST) with the ignition switched on and the starting device actuated ( 31 . 46 ) with reference to the temperature setpoint (T_SP_HIGH) with the ignition switched on and non-actuated starting device ( 31 . 46 ) is higher. Method according to Claim 1, characterized in that when the internal combustion engine is at a standstill ( 10 ), with the ignition switched on and the starter 31 . 46 ) is checked how often the ignition has been switched on without the starting device ( 31 . 46 ) has been actuated and, when a predetermined threshold value (CTR_IGK_ON_SW) is exceeded, a temperature setpoint is selected for this number which corresponds to the temperature setpoint (T_SP_LOW) when the ignition is switched off. Method according to Claim 1 or 2, characterized in that when the internal combustion engine is at a standstill ( 10 ), with the ignition switched on and the starter 31 . 46 ) is checked whether a predetermined period of time (t_SP_HIGH) has expired since the ignition was first turned on and in the positive case, a temperature setpoint is selected, which corresponds to the temperature setpoint (T_SP_LOW) with the ignition off. Method according to one of claims 1 to 3, characterized in that when the ignition is switched off after a predetermined period of time (t_SP_LOW), the heating control device ( 30 ) is deactivated. A method according to claim 1, characterized in that in a Nachstartphase after a successful start of the internal combustion engine ( 10 ) the temperature setpoint starting from the temperature setpoint (T_SP_ST) with the ignition switched on and the starting device actuated ( 31 . 46 ) is reduced with increasing time. Method according to one of the preceding claims, characterized in that after a period of time (t_ST) has elapsed after a successful start of the internal combustion engine ( 10 ) the heating control device ( 30 ) is deactivated. A method according to claim 6, characterized in that the time period (t_ST) depending on the temperature (TKW) of a coolant at the start of the internal combustion engine ( 10 ), an alcohol content (ALC_AN) of the fuel and an air-fuel ratio (AFR). Method according to one of the preceding claims, characterized in that the temperature setpoint values (T_SP_LOW, T_SP_HIGH, T_SP_ST) for the fuel depend on the temperature (TKW) of a coolant at the start of the internal combustion engine ( 10 ) and an air-fuel ratio (AFR). 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 1-8, 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 1-8, characterized in that the 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 1-8, 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. Device for operating a fuel system of a spark-ignited internal combustion engine operable with alcohol or alcohol mixtures as fuel ( 10 ), with at least one heating device ( 20 . 22 ) for heating the fuel and a heating control device ( 30 ) for controlling and / or regulating the heating power of the at least one heating device ( 20 . 22 ), wherein the device is designed to carry out a method according to one of claims 1 to 12.

Images