EP1784567A1

EP1784567A1 - Method for operating an internal combustion engine, taking into consideration the individual properties of the injection devices

Info

Publication number: EP1784567A1
Application number: EP05758493A
Authority: EP
Inventors: Marco Gangi; Gerit Von Schwertfuehrer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-08-24
Filing date: 2005-06-23
Publication date: 2007-05-16
Also published as: DE102004040926A1; US7600504B2; JP2008510921A; DE102004040926B4; WO2006021469A1; US20080262697A1

Abstract

The invention relates to a method for operating an internal combustion engine (1), whereby the fuel is injected into the combustion chamber (4) of a cylinder (3) of the internal combustion engine (1) using an injection device (9). The inventive method is characterized in that a fuel amount to be injected is determined depending on the individual properties of the injection device (9) and the system functions are monitored. An actual torque (M) is detected on the basis of the parameters of the internal combustion engine (1) and is monitored for a deviation from an admissible torque (M_z). The individual properties of the injection device (9) are taken into consideration when determining the actual torque (M), thereby improving supervision of the system functions.

Description

METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE IN WHICH D-W'S INDIVIDUAL CHARACTERISTICS OF THE INJECTION DEVICES ARE TAKEN INTO ACCOUNT

10

The present invention relates to a method for operating an internal combustion engine, wherein the fuel by means of an injection device in a combustion chamber of a

15 cylinder of the internal combustion engine is injected, wherein an amount of fuel to be injected is determined depending on individual characteristics of the injection device, and in which a function monitoring is performed, in which based on operating variables of the

20 internal combustion engine, an actual torque is determined and monitored for a deviation from an allowable torque.

Furthermore, the present invention relates to a control device for an internal combustion engine and a computer program for such a control device.

25 State of the art

In the context of conventional operating methods, the actual torque output by the internal combustion engine is determined from various operating variables of the internal combustion engine, such as an injection duration and an injection pressure with which the fuel is injected into the combustion chamber. With the aid of this actual torque, safe operation of the internal combustion engine is monitored. If that is in actual torque determined above, for example, exceeds a predefinable threshold value, an error can be registered in a control unit controlling the internal combustion engine or even the injection device can be deactivated via a shutdown path provided for this purpose. As a threshold or comparison value for monitoring the actual torque, for example, a permissible torque is used, which is derived for example from a serving to control the engine target torque.

A comparable calculation of the actual torque is known, for example, from DE 103 00 194 A1, which is hereby made part of the disclosure of the present description.

However, the conventional operating methods are sometimes very inaccurate in terms of determining the actual torque, which u.a. is due to a large variance of the individual characteristics of the injectors. Among individual properties of the injector in this context, e.g. a diameter of a nozzle opening and other characteristic physical quantities which are capable of influencing the function of the injector, and e.g. an aging behavior and the like.

This scattering is mostly due to production and influences in the present case, inter alia, the relationship between the injection duration, the injection pressure and an actually injected into the combustion chamber fuel quantity, on which in turn depends on the actual torque. Accordingly, it is an object of the present invention to develop a generic operating method and a control unit and a computer program for a control unit to the effect that a more reliable determination of the actual torque and thus improved monitoring of the internal combustion engine is possible.

This object is achieved in an operating method of the type mentioned in the present invention that the individual properties of the injector are taken into account in the determination of the actual torque.

Advantages of the invention

As a result, a more accurate determination of the actual torque is possible, and for monitoring the internal combustion engine by means of the actual torque, e.g. in the context of a comparison of the actual torque with one of the for controlling the

Internal combustion engine provided target torque derived allowable torque, lower tolerance thresholds can be set, whereby the monitoring is also improved because errors can be detected faster.

According to a very advantageous embodiment of the present invention, corresponding adjustment values are used in the determination of the actual torque for the individual properties of the injection device. Such adjustment values indicate, for example, a deviation of a diameter of a nozzle opening from a value averaged over several injectors for the diameter of the nozzle opening for a particular injector, and thus allow, with simultaneous knowledge of the statistical averaged value and the adjustment value to determine the nozzle diameter of the considered injection device and thus at least partially compensate for their mostly production-related tolerances.

Of course, the adjustment values may be e.g. Depending on the type of injector, other physical quantities such as e.g. temperature dependence, etc., which vary from device to device, e.g. due to production-related tolerances or the like.

For example, the trim values can be used directly in manufacturing, e.g. in the context of a quality control, determined and assigned to the respective devices or be subsequently determined.

According to a further variant of the present invention, it is particularly advantageous to store the adjustment values in a preferably non-volatile memory of a control unit of the internal combustion engine. In this way, the trim values can be written once into the memory and read out of the engine as needed over the entire operating life of the engine, or in the meantime as e.g. during maintenance, to be modified.

Another very advantageous embodiment of the invention provides that the same adjustment values are used in determining the actual torque, as in the determination of the fuel quantity to be injected, which is performed, for example, in the context of a control of the internal combustion engine. Another advantageous embodiment of the operating method according to the invention is characterized in that the adjustment values of functions preferably realized outside the function monitoring, in particular from a control of the internal combustion engine, are adopted. In this way, the adjustment values do not have to be read from the EEPROM in function monitoring or otherwise determined, but can be copied directly from corresponding quantities of, for example, the engine control functions, thereby saving resources of the controller such as RAM, ROM and running time can.

A further development of the method according to the invention is characterized in that the adopted calibration values are plausibility-checked, preferably using theoretical maximum values and / or an injection pressure and / or an injected fuel volume. As a result, an increased security in the determination of the actual torque is given, which allows an even more reliable function monitoring of the internal combustion engine.

A further solution of the object of the present invention is given by a control device for an internal combustion engine according to claim 7 and a computer program for the control device according to claim 9.

Of particular importance here is the realization of the method according to the invention in the form of the computer program which has program code which is suitable for carrying out the method according to the invention when it is executed on a computer. Furthermore, the program code can be stored on a computer-readable data carrier, for example on a so-called flash memory. In these Cases, the invention is thus realized by the computer program, so that this computer program in the same way represents the invention, as the method to whose execution the computer program is suitable.

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing.

drawings

Figure 1 shows a schematic block diagram of an embodiment of an internal combustion engine according to the invention, and

FIG. 2 shows schematically a time profile of the actual torque of the internal combustion engine,

Figure 3 shows the torque curve of Figure 2 with a threshold a, and

FIG. 4 shows the torque curve from FIG. 2 assuming an error.

Description of the embodiments

In the figure 1 is an internal combustion engine 1 of a

Motor vehicle shown in which a piston 2 in a cylinder 3 back and forth. The cylinder 3 is provided with a combustion chamber 4 which is delimited inter alia by the piston 2, an inlet valve 5 and an outlet valve 6. With the intake valve 5, an intake pipe 7 and with the exhaust valve 6, an exhaust pipe 8 is coupled. In the region of the inlet valve 5 and the outlet valve 6, an injection valve 9 protrudes into the combustion chamber 4, via which fuel can be injected into the combustion chamber 4. In the exhaust pipe 8, a catalyst 12 is housed, which serves to purify the exhaust gases resulting from the combustion of the fuel.

The injection valve 9 is connected via a pressure line with a fuel storage 13. In a corresponding manner, the injection valves of the other cylinders of the internal combustion engine 1 are connected to the fuel storage 13. The fuel storage 13 is supplied via a supply line with fuel. For this purpose, a preferably mechanical fuel pump is provided which is adapted to build up the desired pressure in the fuel accumulator 13.

Furthermore, a pressure sensor 14 is arranged on the fuel storage 13, with which the pressure in the fuel storage 13 is measurable. This pressure is that pressure which is exerted on the fuel and with which therefore the fuel is injected via the injection valve 9 into the combustion chamber 3 of the internal combustion engine 1.

During operation of the internal combustion engine 1, fuel is conveyed into the fuel reservoir 13. This fuel is injected via the injection valves 9 of the individual cylinders 3 into the associated combustion chambers 4. By combustion of the prevailing in the combustion chambers 3 air / fuel mixture, the piston 2 will be placed in a reciprocating motion. These movements are transmitted to a non-illustrated crankshaft and exert on this torque. A control unit 15 is acted upon by input signals 16, which represent measured operating variables of the internal combustion engine 1 by means of sensors. For example, the controller 15 is connected to the pressure sensor 14, an air mass sensor, a speed sensor, and the like. Furthermore, the control unit 15 is connected to an accelerator pedal sensor which generates a signal indicative of the position of a driver-actuated accelerator pedal and thus the requested torque. The control unit 15 generates output signals 17 with which the behavior of the internal combustion engine 1 can be influenced via actuators or actuators. For example, the control unit 15 is connected to the injection valve 9 and the like and generates the signals required for their control.

Among other things, the controller 15 is provided to the

Operating variables of the internal combustion engine 1 to control and / or to regulate. For example, the fuel mass injected by the injection valve 9 into the combustion chamber 4 is emitted by the control unit 15, in particular with regard to low fuel consumption and / or low fuel consumption

Controlled pollutant development and / or regulated. For this purpose, the control unit 15 is provided with a microprocessor which has stored in a storage medium, in particular in a flash memory, a computer program which is adapted to perform said control and / or regulation.

Also implemented in the control unit 15 is a function monitoring of the internal combustion engine 1, which is based on a determination of the output from the internal combustion engine 1 torque, which is hereinafter referred to as actual torque. The actual torque is determined by calculation from the control unit 15 operating variables of the internal combustion engine 1 in the control unit 15. Such operating variables are, for example, an injection duration, ie the length of a time interval over which fuel is injected into the combustion chamber 4 and an injection pressure, ie the pressure in the fuel reservoir 13 determined with the aid of the pressure sensor 14, with which the fuel is injected into the combustion chamber 4.

By way of example, the time profile of the actual torque M is shown in FIG.

For monitoring the internal combustion engine, the actual torque M is preferably periodically compared with an allowable torque M_z, which is formed in the control unit 15 based on a desired torque, which in turn represents an output value for the control of the internal combustion engine 1. Depending on this target torque, for example, the injection pressure and Einspitzdauer be controlled.

The setpoint torque in turn depends on various sizes, i.a. also from a torque request of a driver who signals the torque requested by him, for example by means of the aforementioned accelerator pedal sensor to the control unit 15.

The permissible torque results, for example, from the setpoint torque and a threshold value added to the setpoint torque.

The function monitoring of the internal combustion engine 1 by means of the actual torque M is carried out in particular to to prevent an unauthorized increase in the actual torque M, as it can occur in the event of a fault. If a deviation is detected in the above-mentioned comparison between the permissible torque and the actual torque M, the internal combustion engine 1 can accordingly be deactivated for safety reasons, for example, or at least one fault entry in an error memory of the control device 15 is made.

Due to the production-related tolerances in the injection valve 9, it can in conventional

Operation process occur that even without malfunction in the control of the internal combustion engine 1, a significant deviation between the target torque and the actual torque M occurs. This deviation stems from the fact that calibration values are used in the context of a function also referred to as injector quantity adjustment in the conventional methods for triggering the injection valve 9, which compensate, for example, fluctuating individual properties of the injection valve 9, but not for a determination of the actual torque.

This situation is explained below with reference to FIG. 2, FIG. 3, whereby it is always assumed that there is no error case. Depending on the strength of the injection quantity compensation, the determined actual torque may lie between a lower torque M_u and an upper torque M_o, which define a d + b (FIG. 2) wide torque band around the actual torque M, which is ideally identical to the setpoint torque.

To be at e.g. through the o.g. Tolerances did not already cause deviations from this ideal one

To trigger an error reaction, the permissible torque must be so be chosen that an actual torque within the interval b + d does not yet lead to an error entry. This means that the threshold value for fault detection between the setpoint torque and the permissible torque must be at least b - in the direction of increasing torques. For safety reasons, primarily a deviation of the actual torque in the direction of larger torques is to be monitored.

Components of the function monitoring, which do not affect the injector balance, provide in turn

Inaccuracies in the Istdrehmomentberechnung which is taken into account by the applicable threshold a, so that torque values within the interval a are still considered to be allowed. This is shown in simplified form in FIG. 3. In the diagram of FIG. 3, no injector balance takes place, but it is in the monitoring of the actual torque M only the threshold a for the consideration of other inaccuracies on the actual torque M open. Only when the determined actual torque M exceeds this threshold a and the permissible torque defined thereby, an error is detected.

For simultaneous consideration of the

Injector quantity compensation and the further inaccuracies (FIG. 3) thus result in FIG. 2 a threshold c = a + b, starting from an actual torque M matching the target torque ideally. Only if the actual torque determined is this threshold c and thus the permissible torque M_z is exceeded, an error is detected.

In an unfavorable scenario according to FIG. 4, the determined actual torque M is in the conventional one Operating method, for example in the range of the smallest allowable torque M_u. This may be the case due to the disregard of the injector balance in the determination of the actual torque M, although the actual output of the internal combustion engine torque 1 is for example in the range of torque M_o.

In order to be able to recognize this effectively when an error occurs, the determined actual torque M in this case would first have to exceed the permissible torque M_z, i. only when the actual torque due to an error by an amount of about a + b + d would be greater than the smallest allowable torque M_u an error would be detected, although the actual output from the internal combustion engine 1 torque is already significantly greater than M_z due to the error.

The operating method according to the invention provides for the consideration of adjustment values analogous to the injection quantity compensation also for the determination of the actual torque M. This means that also in the determination of the actual torque in the context of

Function monitoring of the internal combustion engine 1, the individual properties of the injection valve 9 are taken into account and the actual torque value can be calculated by it more accurately. As a result, the thresholds b, d (FIG. 2) can be avoided or significantly reduced because the fuzziness described above no longer occurs in the determination of the actual torque M, which has led to the torque band b + d in conventional methods. This means that only the threshold a of FIG. 3, for example, must be provided as the only threshold for error detection. The permissible torque M_z differs in the method according to the invention therefore only to the threshold a of the target torque.

In an advantageous embodiment of the invention, the adjustment values for the injector quantity adjustment for each injection valve 9 of the internal combustion engine 1 are stored in an EEPROM memory of the control unit 15. From there they can e.g. be read when starting the engine and used for the subsequent determination of the actual torque.

For the determination of the actual torque, the same adjustment values are particularly advantageously used as for the injector quantity adjustment in the case of activation of the injection valves 9, in which an amount of fuel to be injected is calculated as a function of the adjustment values.

In a further variant of the invention has a

Processing of the adjustment values stored in the EEPROM for their consideration in the context of the function monitoring, i. in the determination of the actual torque, not necessarily be carried out, since such treatment, e.g. already required for the control of the internal combustion engine and can be taken over from there.

It is also possible, instead of all adjustment values, to use only some adjustment values or simplified adjustment values derived therefrom for determining the actual torque. For example, in the case of adjustment values stored individually for each cylinder, it may be sufficient to evaluate those adjustment values which correspond to the injection valves with the maximum deviations of their individual properties in the case of the considered internal combustion engine. That is, for example, only the adjustment value of the maximum deviating from the statistical average injection valve is considered and also used for the other injectors to determine the actual torque. This is a safe estimate of the

Actual torque is possible, e.g. a still lower threshold b (Fig. 2) is allowed, measured on a theoretical maximum deviation of the injection valve, as used in conventional methods.

An averaging over the adjustment values of the individual injectors is also conceivable.

In another embodiment in which it is not possible to fall back on the adjustment values stored in the EEPROM within the scope of the function monitoring to determine the actual torque, the adjustment values or values derived therefrom can be taken from the control of the internal combustion engine, which is also implemented in the control unit 15 ,

In this case, a plausibility of the inherited values is particularly advantageous, for example, under

Use of the theoretically maximum possible adjustment values can be performed.

The plausibility check can also be made dependent on the injection pressure and / or the volume of the injected fuel.

The application of the method according to the invention is also possible in operating modes in which the injection quantity is not injected at once but distributed over a plurality of partial injections into the combustion chamber. In principle this is Method according to the invention can be used wherever a function monitoring of the internal combustion engine is carried out and quantities are to be monitored, in whose determination or calculation adjustment values are used.

Claims

claims

1. A method for operating an internal combustion engine (1), wherein the fuel is injected by means of an injection device (9) in a combustion chamber (4) of a cylinder (3) of the internal combustion engine (1), wherein an amount of fuel to be injected in dependence on individual characteristics of the injection device (9) is determined, and in which a function monitoring is performed in which based on operating variables of the internal combustion engine (1) an actual torque (M) is determined and monitored for a deviation from an allowable torque, characterized in that the individual properties of Injection device (9) in the determination of the actual torque (M) are taken into account.

2. The method according to claim 1, characterized in that the individual properties of

Injection device (9) corresponding adjustment values in the determination of the actual torque (M) can be used.

3. The method according to claim 2, characterized in that the adjustment values are stored in a preferably nicht¬ volatile memory of a control device (15) of the internal combustion engine (1).

4. The method according to any one of claims 2 or 3, characterized in that in the determination of the actual torque (M) the same adjustment values are used as in the determination of the amount of fuel to be injected.

5. The method according to any one of claims 2 to 4, characterized in that the adjustment values of preferably outside the function monitoring realized functions, in particular from a control of the internal combustion engine (1), are accepted.

6. The method according to claim 5, characterized in that the adopted adjustment values are plausibilized, preferably using theoretical maximum values and / or an injection pressure and / or an injected fuel volume.

7. Control unit (15) for an internal combustion engine (1), wherein the fuel by means of an injection device (9) in a combustion chamber (4) of a cylinder (3) of

Internal combustion engine (1) can be injected, wherein an amount of fuel to be injected depending on individual characteristics of the injection device (9) can be determined, and wherein a function monitoring is feasible, in which based on operating variables of the internal combustion engine (1) an actual torque (M) can be determined and can be monitored to a deviation from an allowable torque, characterized in that the individual properties of the injection device (9) in the determination of the actual torque (M) are taken into account.

8. Control device (15) according to claim 7, characterized in that the control device (15) for carrying out the method according to one of claims 2 to 6 is suitable.

9. Computer program for a control unit (15) of an internal combustion engine (1) with pregraphic code, which is adapted to carry out the method according to one of claims 1 to 6, when it is executed on a computer.

10. Computer program according to claim 9, wherein the program code is stored on a computer-readable medium.