EP1309781B1 - Method and device for the control of an internal combustion engine - Google Patents

Abstract

A method and device for the control of an internal combustion engine are disclosed. Starting with a first parameter which characterises the injection amount and a second parameter which characterises the angular position at which the injection amount is determined, a third parameter which characterises the torque produced by the engine is determined. Further, starting with a fourth parameter which characterises the driver's wish, a fifth parameter which characterises the torque desired by the driver is determined. The third and fifth parameters are evaluated for error monitoring.

Description

State of the art

The invention relates to a method and a device for controlling an internal combustion engine.

From DE 40 33 049 a method and an apparatus for checking a sensor for detecting the position of a quantity control unit and the quantity control unit is known. In the method described there is checked when de-energized Mengenstellwerk whether a needle movement sensor or a corresponding sensor provides an output signal.

US-A-5,996,547 describes a control of an internal combustion engine in which, based on the combustion chamber pressure, the torque provided by the internal combustion engine is calculated. Furthermore, based on the driver's request, the desired moment is determined. Based on the comparison between the desired moment and the torque measured from the combustion chamber pressure, errors are detected.

From US-A-5,591,176 a method is known in which the actual torque of a diesel engine is calculated from a control rod position and the injection time. This rack position is usually detected by means of a sensor. In this device, therefore, a sensor is necessary, which detects the rack position this

However, document states and that the rack position is to be understood only in a trivial sense and generally represents a value for fuel flow (Sp. 3, 710 et seq.).

Furthermore, methods are known in which various signals are plausibilized with each other.

Especially with the use of an injection quantity signal, the plausibility check with other signals is problematic, since in today's systems injections frequently occur which do not contribute to the moment of the internal combustion engine. These are, for example, pre-injections which take place before the actual injection and post-injections which are used in particular for the treatment of exhaust gas or for the regeneration of filters and / or catalysts.

Advantages of the invention

According to the invention, starting from a drive duration of a final stage, a solenoid valve or a piezoactuator, which characterizes the injection quantity, and a second variable, which characterizes the angular position at which the injection quantity is measured, a third variable, which characterizes the torque provided by the internal combustion engine , certainly. Starting from a fourth variable, which characterizes the driver's request, a fifth variable, which characterizes the moment desired by the driver, is determined. The third size and the fifth size are evaluated for error monitoring. By this procedure according to the invention a safe and accurate fault detection in the area of the entire control unit is possible. It is particularly advantageous here that the second variable, which characterizes the angular position of the crankshaft or the camshaft during the injection, is taken into account. This makes it possible to take into account the influence of the injected fuel on the moment provided by the internal combustion engine. The second variable used is preferably the desired value or actual value of the start of injection, the start of delivery, the start of activation or another corresponding variable.

It is particularly advantageous if the fourth size corresponds to the position of a control element. As a result, too Error in the processing of the output signals of the control recognizable.

It is advantageous if an error is detected if the third size and the fifth size deviate from one another by more than a threshold value. This procedure makes it possible to detect errors in the entire signal path of the controller. These are in particular errors in the range of the evaluation of the input variables, the calculation and the determination of the output variables.

Due to the fact that the fault monitoring takes place only in certain operating states, on the one hand the effort can be reduced. Furthermore, a more precise error detection is possible, since in states in which no clear results can be obtained, no error detection takes place.

Advantageous and expedient refinements and developments of the invention are characterized in the subclaims.

drawing

The invention will be explained below with reference to the embodiments shown in the drawing. 1 shows a block diagram of the device according to the invention, FIG. 2 shows a detailed representation of the device according to the invention, and FIG. 3 shows a flow diagram for clarifying the method according to the invention.

Description of the embodiments

The procedure according to the invention is described below using the example of the control of a diesel internal combustion engine. The procedure according to the invention is however not limited to use with a diesel engine. It can also be used in other internal combustion engines in which there is a relationship between the injected fuel quantity and torque of the internal combustion engine, or in the systems where there is a defined relationship between the injection quantity and another size to be monitored.

FIG. 1 shows the essential elements of the device for controlling an internal combustion engine. An actuator is designated 100. This actuator 100 determines the amount of fuel to be injected into the internal combustion engine. This is preferably a solenoid valve or a piezoelectric actuator. Depending on the duration of a drive signal, the actuator of the internal combustion engine, not shown, to a certain amount of fuel.

The actuator 100 is acted upon by a designated TPU unit 110 with drive signals. In this case, the TPU provides signals that determine the start of injection, the end of injection. An output stage, not shown, in the actuator converts these into control signals for controlling various switching means.

For this purpose, the TPU 110 is acted upon by a controller 120 with corresponding signals. The controller 120 processes sensor signals from various sensors 130, which provide, for example, signals relating to the driver's request FP, the speed N of the internal combustion engine and other operating parameters or environmental variables.

Furthermore, a monitor 140 is provided to which the output signals of various sensors and the output signals of the TPU are fed. The monitoring 140 acts on the controller 120 and in an advantageous Design a display 150 with corresponding signals. Alternatively, it can also be provided that the display 150 is controlled by the controller 120.

This facility works as follows. Based on various operating parameters, such as in particular the speed of the internal combustion engine and the driver's request, the controller 120 calculates the time at which the injection should take place, and the amount of fuel to be injected. The amount of fuel to be injected is then metered by the actuator 100 of the internal combustion engine and leads to a corresponding moment.

In addition to the amount of fuel that is attributed to the generation of torque, additional fuel quantities are metered at each or at individual Zumeßzyklen. For example, it may be provided that a pre-injection takes place in order to reduce the noise before the actual metering of the fuel. Furthermore, it can be provided that a post-injection takes place after the actual injection. The post-injection serves inter alia for the introduction of hydrocarbons into the exhaust gases, which in turn cause an increase in the temperature of the exhaust gases. Furthermore, these hydrocarbons can cause in a catalytic converter downstream of the engine or particulate filter reactions that are required to keep the catalyst and / or the particulate filter functional.

In particular, the post-injections, which are required for an exhaust aftertreatment system, do not contribute to the output torque of the internal combustion engine. Further partial injections contribute only to a lesser extent to the torque.

The monitor 140 processes the inputs to the controller 120. In particular, the monitor 140 reads the values of the accelerator pedal position sensor. This is in particular the output signal of an AD converter of the accelerator pedal transmitter 130. Furthermore, the monitoring 140 evaluates the last detectable value, for example the actuation duration, and preferably calculates whether these values are plausible, independently of the normal quantity control. If, for example, the accelerator pedal position assumes a large value and the actuation duration signal assumes a large value, this is recognized as a plausible value.

Such a procedure requires adapted to the injection system approach, since the monitoring 140 must take into account whether, for example, a post-injection takes place at the corresponding operating conditions. As a result, the monitoring 140 and there, in particular the plausibility check, must be adapted individually to the injection system.

According to the invention, it is provided that the data of each injection over 720 degrees crankshaft rotation angle are provided independently of the injection system via a defined interface. For this purpose, for each cylinder and for each injection, a quantity is stored, that of the injected quantity and another variable, which is the angular position at which the injection has taken place. With this information, it is possible to determine the moments formed in the cylinder and to make it plausible with other input variables.

By providing a uniform interface, only the determination of the location and the amount of fuel must be adapted specifically to the injection system. Monitoring for plausibility can be the same for all systems respectively. Furthermore, the detected data for the calculation of the current engine power based on the angular position of the crankshaft, the amount of fuel is determined

The monitoring is shown in more detail in FIG. Already described in Figure 1 elements are designated in Figure 2 with corresponding reference numerals. The output signal of the TPU 110 reaches a table 200 and from there to a moment determination 210. The output signal of the torque determination 210 passes via a torque summation 220 to a logic 230, which in turn delivers a corresponding output signal to the display 150 or to the controller 120. The second input of the logic 230 is the output of a torque map 240, the output signals FP and N of the sensors 130 are fed as input.

This device works as follows. The indication of the indicated torque is based on a quantity that characterizes the injection amount that has been metered and a quantity that characterizes the angular position at which the amount of fuel is metered. For this purpose, the injection start and the duration of injection are preferably read from the corresponding registers of the TPU 110. Instead of the injection duration and the corresponding injection angle can be used. The start of injection indicates the time or the angular position of the crankshaft at which the injection takes place. The injection duration defines the duration of the injection or the angle that is swept during the injection.

In this case, the actual injection commencement and injection durations, or the times or the angular positions at which the actuation of the actuator takes place, can be read out of the TPU. Based on the duration of injection, an amount of fuel is determined. In determining the Quantity from the control period is taken into account, for example, that the control of the actuator is longer than the actual injection. The fuel quantity determined for each injection is entered into the table 200 separately for each cylinder together with the drive start angle. This table contains all the injection events of a cylinder over 720 degrees crankshaft. As an identifier, the cylinder number is also stored in the table. To ensure data integrity, a counter is included, which is incremented each time the last event table is written. For each cylinder, a message is created with the table layout managed by the operating system. This prevents access conflicts through concurrent processing. Furthermore, an adjustment of the storage requirements to the required number of cylinders is easily possible. The determination of the injection quantity and the associated start of injection takes place in the table, preferably in angular synchrony.

Table 200 forms the interface between the controller and the monitor. The message is the same as the table layout for all injection systems.

In the moment determination 210, an indexed moment is calculated from this data for each cylinder and forwarded to the momentum summation 220. The momentum summation 220 calculates time-synchronized indexed moments summed over all cylinders.

At the output of torque summation 220, an indexed moment determined over a sampling period is then available.

Parallel to this, based on the accelerator pedal position FP and the rotational speed N by means of a torque map 240, a variable is determined which characterizes the driver's request. These Size and the size that characterizes the indexed moment are checked for plausibility by the logic 230 and, if there is a deviation, detected for errors and preferably a corresponding display 150 is activated.

Instead of the torque map 240, a calculation can also take place by means of a formula. Furthermore, other sizes or other sizes in addition to the accelerator pedal position and the speed can be used.

FIG. 3 shows the procedure on the basis of a flowchart. In a first step 300, the desired torque MS is calculated on the basis of the rotational speed and the accelerator pedal position FP. A subsequent query 310 checks whether there are operating states in which a plausiblization is possible. If this is not the case, step 300 is repeated.

If such an operating state exists, then in step 320 the indicated torque is determined for each individual cylinder. For this purpose, the control period is weighted with the crankshaft angle and thus the indicated torque per injection determined. This determination preferably takes place for each partial injection, that is to say for the pre-injection, for the main injection and also for the post-injection. Fuel amounts that are metered in the post-injection are preferably weighted with the value zero because they do not contribute anything to the moment. Activation time, main injection and the pilot injection are determined according to a predetermined function, the indicated moment of the respective injection.

In the subsequent step 330, the individual indexed moments are integrated over a plurality of partial injections and preferably and / or over a plurality of cylinders, and the actual torque MI is determined therefrom. Subsequently, in step 340, the Amount of the difference between the target torque MS and the actual torque MI calculated. The subsequent query 350 checks whether the amount of moment difference MD is greater than a threshold value SW. If this is not the case, step 300 is repeated.

If the magnitude MD of the torque difference is greater than a threshold, then an error is detected in step 360. The threshold value SW is selected such that possible tolerances in the determination of the torque do not lead to an error triggering.

Claims (6)

1. Method for controlling an internal combustion engine in which, on the basis of an actuation period of an output stage, of a solenoid valve or of a piezoactuator which characterizes the injection quantity, and of a second variable which characterizes the angular position at which the injection quantity is metered, a third variable which characterizes the torque made available by the internal combustion engine is determined, in that, on the basis of a fourth variable which characterizes the driver's request, a fifth variable which characterizes the torque desired by the driver is determined, in that the third variable and the fifth variable are evaluated in order to monitor faults.
2. Method according to Claim 1, characterized in that the second variable corresponds to the angular position of the crankshaft at which the injection takes place.
3. Method according to one of the preceding claims, characterized in that the fourth variable corresponds to the position of an operator controlled element.
4. Method according to one of the preceding claims, characterized in that a fault is detected if the third variable and the fifth variable deviate from one another by more than a threshold value.
5. Method according to one of the preceding claims, characterized in that the monitoring of faults takes place only in specific operating states.
6. Device for controlling an internal combustion engine, having means which, on the basis of an actuation period of an output stage, of a solenoid valve or of a piezoactuator which characterizes the injection quantity, and of a second variable which characterizes the angular position at which the injection quantity is metered, a third variable which characterizes the torque made available by the internal combustion engine is determined, in that, on the basis of a fourth variable which characterizes the driver's request, a fifth variable which characterizes the torque desired by the driver is determined, in that the third variable and the fifth variable are evaluated in order to monitor faults.

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