EP1313936B1 - Method and device for controlling an internal combustion engine - Google Patents

Description

State of the art

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

To control a central control unit and a peripheral control unit is provided. The central control unit transmits request signals to the peripheral control unit. The peripheral controller acts on the basis of these request signals consumers with control signals. The consumers are, in particular, injectors which control the metering of fuel into the internal combustion engine.

It is particularly advantageous here that the peripheral control unit checks the request signals and / or further signals for plausibility, such as, for example DE-A-196 22 399 known. As a result, the security of the control can be significantly increased. Furthermore, it is advantageous that the central control unit only provides simply configured request signals which define only the beginning and the end of the injection. The peripheral controller then converts these into certain current and voltage profiles required to drive the injectors are. Furthermore, the peripheral controller can perform monitoring of the injectors and the power amplifiers. Furthermore, by using a peripheral control unit, individual adaptation to the injectors is possible. On the other hand, however, the central control unit can be used globally for various injectors. This results in a significant cost savings, since the central control unit can be manufactured in large quantities, since the adaptation to the different injectors in the peripheral control unit takes place.

From the DE 198 21 561 a method of a device for monitoring electromagnetic consumer is known. There, the voltage and / or the current flowing through a booster capacitor or applied to the booster capacitor is monitored for plausibility.

Furthermore, a method and a device for controlling at least one consumption of the DE 195 39 071 known. There consumers are divided into at least two groups. Where the costly and expensive components are each provided only for a group.

drawing

The invention will be explained below with reference to a drawing illustrated embodiments.

Show it FIG. 1 in block diagram of the device according to the invention, FIG. 2 a block diagram of the peripheral controller, FIG. 3 different block time applied signals and FIG. 4 a flowchart illustrating the procedure of the invention.

Description of the embodiments

The invention is preferably used in internal combustion engine, especially in auto-ignited internal combustion engines. There, the fuel metering is controlled by means of injectors, which are actuated by means of electromagnetic valves or by means of piezo actuators. These injectors, or these valves or actuators are referred to below as consumers.

In FIG. 1 are the most essential elements of the device according to the invention shown. A central control unit is designated by 100. These are fed signals from various sensors. This is, on the one hand, a first sensor 110, which provides a signal FP with regard to the driver's request, a second sensor 120, which supplies signal NW with respect to the camshaft revolution, and a third sensor 130, which supplies a signal KW with respect to the crankshaft position. As sensors 120 and / or 130 sensors in particular the increment or segment gears are used. These sensors provide pulses at a fixed angular distance.

The central control unit supplies a peripheral control unit 150 with various request signals A1 to A8. The number of request signals preferably corresponds to the number of consumers to be controlled. Furthermore, the central control unit 100 forwards the signal KW with respect to the crankshaft position to the peripheral control unit 150. Preferably, the request signals A1 to A8 are each transmitted via a line. Further, the central control unit 100, the peripheral control unit 150 and other units, not shown, via a communication system, which is in particular designed as a CAN bus connected.

The peripheral control unit 150 is in turn connected by lines to the consumers 161 to 168. These are each supplied with the control signals S1 to S8. In the illustrated embodiment is an internal combustion engine with eight cylinders. However, the procedure according to the invention can also be used with internal combustion engines with different numbers of cylinders.

The peripheral control unit 150 is connected via a switching means 170 which can be controlled by the central control unit 100 to a supply voltage Ubat.

Based on various variables that characterize the operating state, the environmental conditions and / or the driver's request, the central control unit 100 determines request signals A1 to A8. These request signals determine the beginning, the end and thus the duration of the fuel metering. In accordance with trained consumers, this signal can be used directly to control a switching means for energizing a consumer, in particular a solenoid valve. The problem now is when consumers are used, which require the exact control of a particular current waveform and / or a specific voltage waveform.

Frequently, fast-switching solenoid valves are used, which are initially charged with an increased voltage, which is also referred to as booster voltage. In the further course of the current is regulated to a holding current. This current profile is preferably realized by means of special output stage components or output stage circuits. If these final stage components are integrated in the central control unit, then a different central control unit must be manufactured for each injector type. If, in contrast, the final stage is arranged structurally separate from the injectors, then can occur during data transmission between the central control unit and the power amplifier errors.

According to the invention, therefore, a peripheral control unit 150 is provided, which converts the general request signals into special control signals and at the same time carries out a diagnosis, in particular of the request signals. The diagnostic result is preferably reported back to the central control unit 100 via the CAN bus. It is particularly advantageous that with a correspondingly recognized error, the central control unit by pressing the switching means 170, the peripheral control unit and thus the consumer can put out of service.

In addition to the monitoring of the request signals A1 to A8, a diagnosis of the injectors and / or the corresponding circuits of the output stage modules is also possible.

It is particularly advantageous that the peripheral control unit effects a phase shift of 90 °. This means that the control signals for a particular cylinder are only triggered when the plausibility check is completed, that is, the request signal is complete. This makes it possible to prevent the control of the corresponding consumer and / or all consumers in case of failure.

A detailed illustration of the peripheral controller is shown in FIG FIG. 2 shown. Already in FIG. 1 described element are in FIG. 2 denoted by corresponding reference numerals. The peripheral control unit 150 essentially comprises a first monitor 210, which is supplied with the signal KW, a second monitor 220, to which the request signals A1 to A8 are fed, a drive calculation 230 and an output stage 240, which supply the control signals S1 to S8 provides. In one embodiment, it can also be provided that the output stage is arranged structurally separate from the peripheral control unit 150.

The drive calculation 230 is acted upon by the first monitoring and the second monitoring with signals and provides a signal to the power amplifier 240. The power amplifier 240 reports a signal to the second monitor 220. Furthermore, the first and the second monitor exchange signals. The second monitor 220 applies a signal to the CAN bus.

In FIG. 3 Different signals are plotted over time. In subfigure 3a, different angular ranges of the crankshaft and in FIG. 3b exemplarily permissible request signals are marked for a first group of consumers. In subfigure 3c are for a second group of consumers different angular ranges of the crankshaft and in 3d figure example permissible request signals marked. In FIG. 3e is a subsection of the FIG. 3a and in 3d figure a section of the FIG. 3b shown enlarged.

In FIG. 3a For a first group of consumers angle ranges are marked with vertical lines. The ensprechenden request signals are shown in part 3B. The angular range between the point t1 and the point t3 denotes the angle range in which a request signal A1 is permitted for a first consumer. The angular range between the point t3 and the point t5 denotes the angular range in which a request signal A3 for a second consumer is allowed. The angular range between the point t5 and the point t7 denotes the angular range in which a request signal A5 for a third consumer is allowed. The angle range between the point t7 and the point t1 indicates the angular range in which a request signal A7 is allowed for a fourth consumer. The distance between each two points defines in the illustrated example an angular range of 180 ° crankshaft angle. The conditions are shown in an internal combustion engine with 8 cylinders. In an internal combustion engine with a smaller Zlinderzahl the angular ranges can be selected to be correspondingly larger.

Accordingly, in Figure 3c and 3d the angle ranges and the request signals of a second group of consumers represented. Successive consumers each in the firing order are assigned to different groups of consumers.

In the FIG. 3 a special embodiment for an internal combustion engine with 8 cylinders is shown. The consumers are divided into two groups, with the angular ranges of two cylinders of the same group immediately adjoin one another. Angular ranges of two cylinders of different groups may overlap. The angle ranges can also be selected so that a gap remains between the angular ranges of two cylinders of the same group. This means that there is an angular range in which request signals are inadmissible. The angle ranges can be arbitrary depending on the requirement.

It is essential that an angle range is specified for each request signal. If the request signal occurs in this angular range, it is recognized as plausible. The angular ranges of the individual request signals may overlap, have a spacing and touch each other.

In the FIGS. 3a to 3d the conditions are shown in an internal combustion engine with 8 cylinders. In an internal combustion engine with a smaller number of cylinders, the angular ranges are correspondingly smaller.

It is shown in the subfigures 3a to 3d, only a simple embodiment with only a partial injection. In further embodiments, in particular in internal combustion engines which are equipped with an exhaust gas aftertreatment system, further partial injections may be provided. This is illustrated in subfigures 3e and 3f, which show an enlarged view of the angular range between t1 and t3 and the corresponding request signals. In this case, the injection is divided into a pilot injection between the points t11 and t12 and a main injection between the points t13 and t14.

The first monitoring 210 performs a plausibility check of the request signals A1 to A8 with the crankshaft signal KW. In this case, errors are detected if the request signal is outside the specific angular ranges of the crankshaft. It will, as in FIG. 3 For example, the allowable angular range for the first request signal is defined by times t1 and t3. According to the invention, it is checked whether the request signal starts and / or ends in a corresponding angular range.

In an alternative embodiment, instead of the crankshaft signal and a camshaft signal can be processed.

If the corresponding request signal lies within this angular range, then the request signal is recognized as plausible. If the number of cylinders is equal, these angular ranges may overlap. This is for example at a Internal combustion engine with 8 cylinders, as it is in FIG. 3 is shown, the case.

Furthermore, a proper request signal is only recognized if the duration of the fuel injection has a certain length, i. H. Distance between the times t13 and t14 is greater than a first threshold or it is less than a second threshold. If the signal is shorter than the threshold value, the request signal is too short or it can be assumed that a glitch occurs. If the request signal is too long, it is assumed that a permanent injection. Corresponding errors are detected by the second monitor 220.

If the first or the second monitoring detects a corresponding error, this is transmitted via CAN bus to the central control unit. This then takes appropriate action in particular an emergency operation is initiated or turned off the peripheral control unit, thus deactivating the power amplifiers.

Outgoing of the request signals A1 and A8 and the crankshaft signal KW, the drive calculation 230 calculates the required current profile and / or voltage profile to suitably drive the loads. This signal passes power amplifier 240. As the final stage, for example, a device as known from the prior art can be used. Preferably, an output stage with at least one high-side switch and at least one low-side switch is used. Preferably, a common high-side switch is used for all consumers or a group of consumers. By appropriate control of the high and the low-side switch then a corresponding current / voltage profile is achieved at the consumer.

One working cycle, ie one engine revolution, consists of two crankshaft revolutions. This means that the peripheral control unit can not immediately recognize in which of the two crankshaft revolutions it is located. This means, for example, that the peripheral control unit does not clearly recognize whether the angular range between t1 and t3 or the angular range between t5 and t7 is present. This requires synchronization.

For synchronization, the procedure is as follows. In a first step, it is checked whether a permissible request signal is present. In this case, preferably all checks are performed. If it is detected that the request signal lies within the permissible angular range, the synchronization has taken place. If it is detected that the request signal is not within the permissible angular range, it is checked that the request signal is plausible in the angular range which is phase-shifted by 360 °. If this is the case, a resynchronization takes place. If the request signal is also inadmissible in this angular range, then an error is detected.

Usually, it is provided that the output stage also performs a fault monitoring. It can thus be provided that the currents flowing through the consumer and / or the voltage values dropping at the load or at components of the output stage are monitored. In particular, it is known from the prior art to monitor the voltage across a so-called booster capacitor. This booster capacitor provides the increased voltage required at power up, which is typically greater than the supply voltage. If the output stage detects a corresponding error, then this is also reported to the second monitoring and passed on from there via the CAN bus to the central control unit.

The procedure for monitoring and plausibility of the signals is described in FIG. 4 illustrated by a flow chart. A first query 400 checks whether two request signals A1 to A8 occur simultaneously. In particular, it is checked whether the beginning and / or the end of two request signals occur simultaneously or almost simultaneously.

If this is the case, which means that two request signals are present at the same time, a query 410 checks whether a special operating state exists. In this special operating conditions, the case may occur that is metered into two cylinders at the same time. This is the case, for example, in internal combustion engine with 8 cylinders, if a Nacheinsprtizung done for exhaust aftertreatment. In such a special operating state, there is no error in the case of two request signals occurring at the same time if the two request signals each occur within their permissible angular range or permissible period of time.

If such a special operating state does not exist, the program ends in step 420. In step 420, errors are detected and a corresponding signal is output via the CAN bus. If two request signals A1 to A8 occur simultaneously, then a short circuit between two lines between the central control unit and the peripheral control unit is assumed.

For internal combustion engines in which such simultaneous injection can not occur, step 410 may be omitted. In this case, if the query 400 detects simultaneous injections, it immediately proceeds to step 420 and detects errors.

If the query 400 detects that none of the signals A1 to A8 occur simultaneously, a query 430 checks whether the request signals occur within a permitted angular range. This means that it is checked whether the request signals of a particular cylinder in the corresponding angular range exists. For example, the request signal for the first cylinder must occur between point t1 and t3, for example.

If one of the conditions is not met, that is, the request signal occurs outside of a certain angular range of the crankshaft or the camshaft and / or outside of a certain period of time, the program ends in step 420. If all conditions are satisfied, the query 440 follows.

Query 440 checks if the duration of the request signal is too long or too short. If this is the case, d. H. the request signal is too long or too short, the program ends with step 420. If the duration of the request signal meets the required condition, step 450 follows. This query checks whether the duration of the injection is plausible. Usually, the request signal is significantly shorter than a segment.

In query 450 it is checked whether the distance between two request signals satisfies certain criteria. In particular, the distance between two request signals must be greater than a threshold value, this is not the case, so the program also ends with step 420. If this is the case, that is, the distances between the request signals are plausible, then step 460 follows the distance between two partial injection checked for plausibility. This means it will check if the distance between the points t12 and t13 assumes a permissible value.

It is particularly advantageous if the number of partial injections is counted. For monitoring purposes, this determined number of partial injections is compared with the number of partial injections transmitted by the central control unit. For this it is necessary that the central control unit or the peripheral control unit transmits the corresponding number via the CAN bus.

In step 460, it is checked whether the current and / or voltage values measured and / or detected by the final stage assume plausible values. If this is not the case, then the program also ends with step 420. If this is the case, then in step 470 a fault-free operation is recognized. Alternatively, it can also be provided that the output stage 240 carries out a fault monitoring and transmits a signal to the monitoring if a corresponding fault exists. In this embodiment, the query 460 merely checks whether a corresponding error signal from the output stage 240 is present.

In FIG. 4 the various checks are carried out in chronological order of time. The order of the checks can also be chosen differently. It is particularly advantageous if the queries are processed in parallel.

Particularly advantageous is an embodiment in which the check on the permissible angular range, that is, the query 430 takes place as the last query. If the query 430 detects that the request signal is not within the permissible angular range, then it is checked that the request signal is plausible in the angular range which is phase-shifted by 360 °. If this is the case, a resynchronization takes place. is the request signal in this angular range also inadmissible, it is detected on error.

Claims (8)

1. Method for controlling an internal combustion engine having a central control unit and a peripheral control unit, wherein the central control unit transmits request signals, which determine the start and the end of the metering of fuel, to the peripheral control unit, and the peripheral control unit applies control signals to at least two loads, wherein the peripheral control unit checks the request signals and/or further signals for plausibility, characterized in that a fault is detected if a start and/or an end of two request signals occur simultaneously or virtually simultaneously.
2. Method according to Claim 1, characterized in that faults are not detected if a special operating state is present.
3. Method according to Claim 1 or 2, characterized in that a fault is detected if one of the request signals occurs outside a specific angular range of the crank shaft or cam shaft and/or outside a specific time period.
4. Method according to one of the preceding claims, characterized in that no fault is detected if a special operating state is present and the first and second request signals occur within a permissible angular range or a permissible time period.
5. Method according to one of the preceding claims, characterized in that a fault is detected if one of the request signals is shorter than a first threshold value and/or longer than a second threshold value.
6. Method according to one of the preceding claims, characterized in that a fault is detected if the interval between a first request signal and a second request signal is less than a threshold value.
7. Method according to one of the preceding claims, characterized in that a fault is detected if current values and voltage values in the region of an output stage assume implausible values.
8. Device for controlling an internal combustion engine having a central control unit and a peripheral control unit, wherein the central control unit transmits request signals, which determine the start and the end of the metering of fuel, to the peripheral control unit, and the peripheral control unit applies control signals to at least two loads, wherein the peripheral control unit checks the request signals and/or further signals for plausibility, characterized in that means are provided which detect a fault if a start and/or an end of two request signals occur simultaneously or virtually simultaneously.

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