DE102007062279B4 - Method for operating an internal combustion engine - Google Patents

Abstract

Method for operating an internal combustion engine (10), in particular in motor vehicles, in which fuel reaches at least one combustion chamber (12) of the internal combustion engine (10) by means of at least one fuel injection device (14), in which an injected fuel quantity of one injection duration (180) is dependent on the fuel injection device (14) and in which an opening movement of a valve element (15) of the fuel injection device (14) is not limited by a stop, characterized in that a control start of the fuel injection device (14) is changed so that the difference between an actual injection end (195) and a desired injection end (200) is minimal, wherein the time interval between a drive end (120) and the actual injection end (195) serves as control variable, and in that a control duration ( 130) serves.

Description

State of the art

The invention relates to a method for operating an internal combustion engine according to the preamble of claim 1 and a control and / or regulating device and an internal combustion engine according to the preambles of the independent claims.

A method of the type mentioned is used for example in internal combustion engines with a common rail fuel system. Common rail, or rail for short, is a common high-pressure fuel line for supplying the cylinders with fuel. Fuel injectors, also called injectors, are connected to the rail. Injection time and injection duration of the fuel injectors are controlled per cylinder by a control unit by means of a map depending on a target injection quantity and a current rail pressure. From the control unit control signals for an actuator are generated per fuel injection device, which in turn actuates a valve element for an injection process.

Manufacturing tolerances of the fuel injection devices, wear over the life, pressure wave effects in the high pressure region of the injection system and other variable boundary conditions during operation of the internal combustion engine may cause deviations of an actual injection amount of a target injection quantity. These quantity deviations can be partially compensated by corrections to a drive duration of the fuel injection device. Thus, for example, manufacturing tolerances can be compensated by a so-called injector counterbalancing (IMA), pressure oscillations arising in the high-pressure region can be partially compensated by a pressure wave correction (DWK) or effects due to wear with a zero-quantity calibration (NMK) can be minimized.

From the DE 10 2005 002 242 A1 For example, a method for operating a fuel injection device of an internal combustion engine is known. This is a piezoelectric actuator. The increase in the force acting on the piezoelectric actuator is interpreted as opening of the valve element and the drop in pressure as closing of the valve element. The actual injection start and the actual injection end are regulated to a setpoint.

From the DE 34 26 799 A1 a device for controlling an internal combustion engine is known. This comprises a control device which determines the start of injection and the injection end of the injection. This compensates for the error caused by changes in the waste or operating times.

The DE 10 2005 032 087 A1 also relates to a method and apparatus for controlling injectors. It is determined a Nadelschließzeitdauer and the Ansteuerzeitdauer depending on the needle closing period.

The DE 10 2006 016 145 A1 describes a method for controlling a valve with variable valve lift.

The DE 101 22 441 A1 shows a method and an apparatus for controlling an internal combustion engine. Here, a structure-borne sound sensor is used.

The DE 102 32 356 A1 describes a method for controlling injectors of a fuel metering system. The start of injection and the duration of injection are regulated to a setpoint.

Also the DE 10 2007 045 641 A1 describes a method for operating an internal combustion engine.

Disclosure of the invention

The object of the invention is to develop a method, a control and regulating device and an internal combustion engine of the type mentioned in such a way that they work even more reliably and precisely so that manufacturing tolerances are even better compensated, wear influences are reduced more and lower emissions are achieved at low cost ,

To solve the problem is proposed starting from the method for operating an internal combustion engine of the type mentioned that a drive time of the fuel injection device is changed so that the difference between an actual injection end and a target end of injection is minimal. For this purpose, an activation start is preferably shifted. The controlled variable used is the time interval between a drive end and the actual injection end. Furthermore, a control period is used as a control variable of the control loop.

This can be achieved with little application effort and without any influence on the hardware, for example an output stage. The time interval between the drive end and the actual injection end corresponds at least approximately to a valve element closing duration and can be quickly adjusted in a closed loop by shifting the start of a drive signal to obtain the target injection end time.

Furthermore, it is proposed that the internal combustion engine and a control and / or regulating device have means which ensure a method of the above type with the features of the independent claims. Advantageous developments are specified in subclaims. For the invention important features are also found in the following description and in the drawing, these features may be important both alone and in different combinations for the invention, without being explicitly pointed out.

Many fuel injection devices use so-called "flying" valve elements, whose opening movement is not limited by a stop, but which are held by an actuator associated with the valve element in an open floating state, or their opening movement continues as long as the actuator is driven. If the control is terminated, the valve element is moved in the closing direction by a constantly acting in the closing direction loading device, for example by a hydraulic force until it impinges on the valve seat. In this case, the speed of the valve element during the opening movement as well as the speed during the closing movement are generally known with sufficient accuracy. This is utilized according to the invention in order to influence or correct the end of injection and thus also the injection quantity only by changing the actuation duration in such a way that predetermined setpoint values are maintained. Thus, only a single operating variable-namely, the activation duration-must be adjusted in a control circuit by shifting the start of control in order to set the parameters essential for the operation of the fuel injector, such as start of injection, end of injection, injection duration and injection quantity, to desired values or regulate that ensure a low-consumption and low-emission operation of the internal combustion engine and thus meet the legal requirements for improving exhaust emissions and reducing fuel consumption. The inventive method is thus very effective and inexpensive.

Constant monitoring of the actual injection end ensures that manufacturing tolerances, wear-related changes in the valve elements and the valve seats, pressure wave effects and other variable boundary conditions can be detected and compensated during operation of the internal combustion engine over the life of the fuel injection device, with a variety of previously applied System functions can be omitted. This simplifies the overall system and reduces the application effort. Complex interactions between individual functions are reduced or completely avoided. Furthermore, the method can simplify the final test in the manufacture of the fuel injection device because test data of the final test are no longer required or only to a small extent for a quantity correction during operation of the internal combustion engine. An influence of power, noise or emission by deviation of the actual injection quantity from a desired injection quantity is avoided even with changing boundary conditions during operation of the internal combustion engine. In addition, the information obtained may be provided to the electronic diagnostic devices (eg, onboard diagnostic device) of the motor vehicle to detect faults in the fuel injection device and to cause the driver, for example, via a dashboard indicator light to visit a workshop ,

Furthermore, it is proposed that a pressure profile in the fuel injection device and / or in a fuel distributor and / or in a line between fuel distributor and fuel injection device and / or a signal of a structure-borne sound sensor is evaluated to determine the actual injection end. The pressure profiles mentioned can be determined in a simple manner with sensors which are usually present anyway, so that no additional hardware is required for carrying out the method. The same applies to structure-borne sound sensors, which are already present in many internal combustion engines, for example for the detection of a combustion process. This development is therefore inexpensive.

In addition, it is proposed that, to determine the actual injection end, repercussions of a closing of the valve element on an actuator of at least one fuel injection device are evaluated. Such reactions are transmitted, for example, in the form of corresponding signals via the existing electrical control lines from the actuator to the control and / or regulating device. An additional sensor is not required in this case, which saves costs.

It is also proposed that a desired value for the controlled variable is determined from a characteristic map into which a drive duration and / or an injection quantity and a fuel pressure are fed. The determination of the controlled variable from a map offers the advantageous possibility of adequately taking into account many variables which influence the fuel injection. In addition, such a map saves computational resources.

If the map is determined in an engine test bench, very many parameters be taken into account, and it saves on the series internal combustion engine Rechenresources.

On the other hand, if the characteristic map is individually taught for each fuel injection device during normal operation of the internal combustion engine while maintaining certain boundary conditions (for example, new state of the fuel injection device), particularities of individual fuel injection device types can be taken into account from the outset in the characteristic field.

In addition, it is proposed that an influence of at least one current operating variable, in particular a current temperature, on a movement speed of the valve element by a controlled correction of the control is taken into account. This allows a particularly accurate correction of the injection process and can be achieved, for example, by a superimposed correction of the regulation of the activation duration.

Brief description of the drawings

An embodiment of the invention will be explained in more detail with reference to figures. Show it:

1 a schematic representation of an internal combustion engine;

2 a diagram in which a drive signal and a stroke of a valve element are plotted against time when an injection end is not controlled;

3 a diagram similar to 2 but with control of the end of injection; and

4 a flowchart of a method for operating the internal combustion engine of 1 ,

Embodiments of the invention

An internal combustion engine, in particular for a motor vehicle, which in its entirety 1 with the reference number 10 is provided, includes an engine block 11 with several combustion chambers 12 , The engine block 11 has a temperature sensor 13 on. Fuel gets into the combustion chambers 12 directly each by means of a fuel injection device 14 , also called injector, injected. For this purpose, each of the fuel injectors 14 via a needle-like valve element 15 , which with a housing-side valve seat 16 at an injection nozzle (not shown) of the fuel injection device 14 cooperates. The valve seat 16 represents a stop of the valve element 15 when closing the fuel injection device 14 A stop, the opening movement of the valve element 15 limited, is not present, since this is a so-called. "Ballistic" embodiment of the valve element ("flying" valve element) is.

By an actor 17 , For example, an electromagnetic actuator, the valve element 15 be moved in the longitudinal direction, whereby the fuel injection device 14 opens and closes. The actor 17 is controlled by drive signals from a control and regulating device 18 via a control and / or data line 19 to the fuel injector 14 be sent, pressed. In the control and regulating device 18 a control loop is integrated to control an injection phase that is required for each fuel injector 14 an individual regulation allows.

The fuel injectors 14 are in the present embodiment via lines 24 to a fuel rail 20 connected, which is also referred to as "common rail" or short "rail". The fuel is in the rail 20 stored under high pressure. For this purpose, the fuel via a high-pressure conveyor 21 in the rail 20 promoted. The pressure in the rail 20 is due to a high-resolution pressure sensor 22 supervised. The fuel injector 14 points to the valve seat 16 opposite end of a structure-borne sound sensor 23 on, which detects structure-borne sound vibrations. By evaluating the signal of the structure-borne sound sensor 23 can be the control and regulating device 18 a striking of the valve element 15 at the valve seat 16 when closing the fuel injection device 14 and thus recognize an actual injection end. In other, not shown embodiments of internal combustion engines, other sensor types in conjunction with other methods for determining the stop of the valve element 15 or the actual injection end are used. For example, the pressure sensor can also be used 22 used to talk about the pressure gradient in the rail 20 close to the actual injection end.

2 shows in the upper section a diagram 60 , which shows the course of a drive signal 100 for controlling the actuator 17 to the valve element 15 from the valve seat 16 to lift (opening movement) over which time represents t. The drive signal 100 has a basically vertical Ansteuerflanke to a control start 110 and after expiration of an activation period 130 a basically vertical Ansteuerflanke to a Ansteuerende 120 on. The drive signal 100 is therefore essentially a rectangular pulse.

In the lower section of 2 are in a diagram 70 different Hubverläufe the valve element 15 over time t represented by the drive signal 100 be effected without the actual injection end being set to a desired Einspitzende is adjusted. The beginning of the stroke can be very good approximation of the start of injection 190 be equated. Analogous to this is the actual injection end 195 then reached when there is no more hub, so the valve element 15 in the valve seat 16 has struck. The lifting movement starts from the beginning of the activation (Diagram 60 ) with a delay caused by a certain inertia of the fuel injection device 14 , but also by manufacturing tolerances of the fuel injection device 14 , wear over the life, pressure wave effects in the rail 20 or other variable boundary conditions in the operation of the internal combustion engine 10 is conditional. Therefore, the delay falls with different injectors 14 or at the same injector 14 at different times of life despite the same tax period 130 different sizes. In 2 are through the lines 140 three such cases are represented, which are distinguishable by the indices a (dashed line), b (solid line), and c (dotted line) distinguishable. Executions without naming the index apply to all three cases. One recognizes the different actual injection starts 190a . 190b and 190c and actual injection ends 195a . 195b and 195c , wherein the index b denotes a desired "ideal" situation in which the deviation from a desired end of injection 200 and a target valve element closing duration 210 is minimal.

The stroke course is due to the following facts: In the ballistic embodiment mentioned above, the valve element lifts 15 after the start of taxation 110 , through an in 1 not shown opening mechanism, such as a hydraulic lift control, from the valve seat 16 off (actual injection start 190 ) and continues the opening movement unhindered until the control is terminated (reference numeral 120 in diagram 60 ). With the end of the control in 120 the direction of movement reverses and the valve element reverses 15 returns under the influence of a not shown closing mechanism during a Ventilelementschließdauer 170 back to its original position, so it reaches the valve seat 16 (Actual injection end 195 ). This means in case of too early start of injection 190a in that the valve element 15 is raised comparatively far and accordingly late back in the valve seat 16 returns (late actual injection end 195a ). An injection duration 180a , the valve element closing time 170a and thus also an injection quantity of fuel are thereby compared with the setpoint values (for example, desired valve element closing duration 210 ). At comparatively late start of injection 190c becomes the valve element 15 raised accordingly little and then returns comparatively early back into the valve seat 16 , The injection duration 180c , the valve element closing time 170c and thus also the injection quantity are compared with the desired value (eg., Soll-Ventilelementschließdauer 210 ) decreased.

By evaluation of the signals of the structure-borne sound sensor 23 can the actual injection end detected and from this the deviation of a time interval between Ansteuerende 120 and actual injection end 195 of the valve element 15 (= Valve element closing time 170 ) from the setpoint 210 determined and for the next injection by one in the control and regulating device 18 be corrected integrated circuit. As a result, in the end, a difference between the actual injection end and a desired injection end (corresponding to the ideal stroke progression 140b ) minimized.

This is based on the assumption that two injections following each other take place under approximately the same conditions. The controlled variable of the control loop is preferably the valve element closing duration 170 , In an alternative embodiment, the controlled variable could also be the end of injection 195 be. The manipulated variable of the control loop is preferably the actuation period 130 , It could also be the start of the drive in an alternative embodiment 110 be. The driving time 130 is adjusted by the control loop so that a correction at the start of control 110 is made while the temporal Ansteuerende 120 (Target specification) remains unchanged. The control loop thus corrects the start of injection 190 , Injection end 195 , Injection duration 180 and so does the injection amount of fuel.

3 shows in the upper section in diagram 80 the drive signal 100 in a regulated by the control loop arrangement and in the lower section again the corresponding stroke over the time t, in each case for the three already in 2 described cases, where the same reference numerals and indices are used for equivalent contents as in 2 , The driving time 130a . 130b . 130c is now - depending on the deviation of the actual injection end 195a -C from the target injection end 200 - postponed; the driving end 120 is unchanged. The drive times 130a -C represent those drive durations associated with the respective fuel injector 14 to a minimum difference between actual injection end 195 and target injection end 200 to lead. Too late actual injection end 195a to correct (curve 140a in 2 ), the driving time becomes 130a (Control variable) shortened accordingly by the control loop, until the Ventilelementschließdauer 170 (Controlled variable) the setpoint 210 corresponds (diagram 90 ). Too early actual injection end 195c to correct (curve 140c in 2 ), the driving time becomes 130c (Control variable) extended accordingly until the valve element closing time 170 (Control variable) also the setpoint 210 equivalent.

From diagram 90 it can be seen that now for all three cases shown, the difference between actual injection end and target injection end (see reference numerals 195 ) is minimal, and that now also the start of injection 190 and the duration of injection 180 correspond to the ideal values.

The speed of the valve element 15 and thus the valve element closing time 170 hang next to the drive time 130 in addition to the pressure in the rail 20 from. Therefore, to determine the target valve element closing time 210 (Controlled variable) in the control and regulating device 18 implemented a map and stored, which is the dependence of the target Ventilelementschließdauer 210 from the driving time 130 and the pressure in the rail 20 considered. In an alternative embodiment, the desired injection quantity and the pressure in the rail can also be used to determine the desired valve closing duration. The parameters of the characteristic map are for a fuel injection device 14 an average embodiment in the application phase of the internal combustion engine 10 determined and stored and / or in a new state of the fuel injection device 14 during operation of the internal combustion engine 10 have been individually trained or adapted in compliance with certain boundary conditions.

Should temperature variations or special characteristics of the fuel injection device 14 indicating the speed of the valve element 15 or the valve element closing duration 170 can be taken into account, then the valve element closing time 170 be superimposed by a controlled correction, which influences the deviating speed of the valve element 15 global or individual for each fuel injector 14 compensated. These can z. B. the start of control 110 and / or the driving time 130 to be influenced.

A possible procedure of the control of the fuel injection device 14 is in 4 shown in a flow chart. In step 300 is calculated taking into account relevant parameters, at least the activation period 130 and the pressure in the rail 20 , using the map described above, the target Ventilelementschließdauer 210 and the target injection end 200 determined and saved. It follows step 310 in which by evaluating the signals of the structure-borne sound sensor 23 the actual injection end 195 a current injection is detected. This will be in step 320 in the control and regulating device 18 the actual valve element closing time 170 the fuel injector 14 determined from the determined target Ventilelementschließdauer 210 may differ. In step 330 becomes the target valve element closing time 210 with the actual valve element closing duration 170 compared.

If a difference is detected, the difference value in the loop described above (step 340 ) introduced, the control mechanism but can only engage in the next injection. In the next injection, therefore, by adjusting the activation duration (= manipulated variable; 130a -C in diagram 80 ) the valve element closing time 170 (Controlled variable) to the specified setpoint 210 regulated and thereby the target injection end 200 recorded. This means that the start of tax 110 corresponding to the detected difference of actual valve element closing time 170 and desired valve element closing time 210 is moved. The control can - as already described above - by a controlled correction to take into account the different valve element speed due to temperature fluctuations or special properties of the fuel injection device 14 be superimposed.

Will in step 330 If no difference is detected, the control loop (step 340 ), or must the Ventilelementschließdauer 170 can not be corrected because the same conditions as in the previous injection were found.

In an alternative embodiment, comparison of the desired valve closure duration may be made 210 with the actual valve element closing duration 170 (Step 330 ) are waived. In this simplified method, the control loop is triggered in each case, even if there is no difference between the target valve element closing duration with the actual valve element closing duration and no end of injection has to be compensated.

Claims (9)

Method for operating an internal combustion engine ( 10 ), in particular in motor vehicles, wherein the fuel by means of at least one fuel injection device ( 14 ) in at least one combustion chamber ( 12 ) of the internal combustion engine ( 10 ), in which an injected fuel quantity of an injection duration ( 180 ) of the fuel injection device ( 14 ) and in which an opening movement of a valve element ( 15 ) of the fuel injection device ( 14 ) is not limited by a stop, characterized in that a control start of the fuel injection device ( 14 ) is changed so that the difference between an actual injection end ( 195 ) and a desired injection end ( 200 ) becomes minimal, the controlled variable being the time interval between a drive end ( 120 ) and the actual injection end ( 195 ), and that a control period ( 130 ) serves. A method according to claim 1, characterized in that for determining the actual Injecting ( 195 ) a pressure curve in the fuel injection device ( 14 ) and / or in a fuel distributor ( 20 ) and / or in a line ( 24 ) between fuel distributor ( 20 ) and fuel injection device ( 14 ) and / or a signal from a structure-borne sound sensor ( 23 ) is evaluated. A method according to claim 1, characterized in that for determining the actual injection end ( 195 ) Reactions of a closing of the valve element ( 15 ) on an actuator ( 17 ) at least one fuel injection device ( 14 ) be evaluated. A method according to claim 1, characterized in that a desired value for the controlled variable is determined from a characteristic map, in which a drive time ( 130 ) and / or an injection amount and a fuel pressure is fed. A method according to claim 4, characterized in that the characteristic map is determined in an engine test bench and / or a hydraulic test stand. A method according to claim 4, characterized in that the characteristic map during normal operation of the internal combustion engine ( 10 ) in compliance with certain boundary conditions for each fuel injection device ( 14 ) is learned individually. Method according to one of the 1 to 6, characterized in that an influence of at least one current operating variable, in particular a current temperature, on a movement speed of the valve element ( 15 ) is taken into account by a controlled correction of the control. Control and / or regulating device ( 18 ) for an internal combustion engine ( 10 ), characterized in that it is designed by programming to perform a method according to any one of claims 1 to 7. Internal combustion engine ( 10 ), in particular for a motor vehicle, with a control and / or regulating device ( 18 ), according to claim 8.

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