EP1045966B1 - Method and device for operating and monitoring an internal combustion engine - Google Patents

Abstract

The invention relates to a method and a device for operating and monitoring an internal combustion engine. In at least one operating state the internal combustion engine is run on a lean air/fuel mixture and at least one quantity representing the degree of accelerator pedal application and one quantity representing engine speed are detected. In at least one operating state the internal combustion engine can be run only with an almost stoecchiometric or rich mixture and/or with a limited air supply. Operation of the internal combustion engine is monitored on the basis of at least one operating quantity of same.

Description

State of the art

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

FR-A 2 722 248 describes a procedure for operation an internal combustion engine known in at least one Operating condition with a lean air / fuel ratio is operated and at least one of the accelerator pedal actuation representative size and a the engine speed representative size is recorded, an optimal one Value for the air / fuel ratio is determined and with the deviation of this optimal value from the measured Air / fuel ratio value a correction the setting of the throttle valve of the internal combustion engine in In terms of regulating the measured value to the optimum Value takes place. Instructions for monitoring the operation not given.

Monitoring is described in DE-A 195 36 038 (US Pat. No. 5,692,472) the control of a conventional internal combustion engine represented on a torque basis. At least there will be a maximum permissible based on the accelerator pedal position Torque or a maximum allowable power determined. Furthermore, the current torque or the current power the internal combustion engine depending on engine speed, Firing angle setting and load (air mass, etc.) are calculated. For monitoring, the maximum permissible value is calculated with the compared current value. Error response measures are initiated when the current value reaches the maximum permissible exceeds. The error response measures exist in a performance limitation, for example in a Switching off the fuel supply to the internal combustion engine until the current value falls below the maximum permissible again.

This surveillance strategy offers a reliable and satisfactory one Monitoring the control of the internal combustion engine in the entire operating area. However, it is based on the measured air mass supplied to the internal combustion engine. In internal combustion engines that are at least in one operating state operated with a lean air / fuel mixture are determined from the measured air mass Torque or the determined power is not the actual one Values, so that the described monitoring only is conditionally operational.

This applies above all to internal combustion engines with direct injection, since the recorded air mass there in shift operation and the set ignition angle to calculate the current one Torque is not sufficient. The immeasurable, injected Fuel mass is lean here as with all operated motors have a strong influence on the torque, by the procedure in the prior art cannot be taken into account. In particular the fuel mass but can be caused by error influences like a too high Rail pressure or an injection valve that closes too slowly be too high so that excessive torque can occur and thus unwanted operating states of the internal combustion engine can arise.

It is an object of the invention to take measures to monitor the Specify control of an internal combustion engine, at least in some operating conditions with a lean air / fuel mixture is operated.

This is due to the characteristics of the independent claims achieved.

A control procedure for a direct injected Gasoline engine is out of the DE-A 196 31 986 known. This internal combustion engine is in essentially in two different operating modes, the Shift operation and homogeneous operation, controlled. In homogeneous operation fuel is injected during the intake phase and throttled the internal combustion engine, in shift operation is injected into the compression phase and the Internal combustion engine operated without throttling.

In homogeneous operation, at least the position of a Accelerator pedal determines a target torque value, the one to be injected Fuel mass is implemented. Also going out a target throttle valve angle from this fuel mass to adjust the air supply to the internal combustion engine determined in the sense of setting a predetermined target value for the exhaust gas composition. The latter does not apply for shift operation in which the internal combustion engine is not throttled, i.e. with the throttle valve open. Homogeneous operation takes place at least in the area of higher loads instead of shift operation in the lower area Loads or in the partial load range. activities for function monitoring of the control system are mentioned in the Publication not described.

Advantages of the invention

The solution according to the invention allows an effective and satisfactory monitoring of the control of an internal combustion engine, the at least in some operating conditions is operated with a lean air / fuel mixture.

There are particular advantages in monitoring the function the control of internal combustion engines with gasoline direct injection.

It is particularly advantageous that when the internal combustion engine is operating with lean mixture depending on the accelerator pedal position a maximum permissible speed is derived above which limits the air supply to the internal combustion engine becomes. This is preferably done by closing the throttle valve.

It is particularly advantageous that only when the button is released Accelerator pedal, i.e. with the pedal in neutral, a maximum speed is specified above which the air supply is limited becomes. This will make at least one particularly critical Operating status through accurate and reliable error detection covered, so that there are none in this operating state unwanted operating situations.

This ensures that when the fuel is turned off e.g. due to a leaky injector an ignitable mixture, the torque or Performance does not become prohibitively high. Advantageously the fresh air supply is adjusted so that when an injection would take place with stoichiometric mixture composition would give a torque which does not lead to an impermissible vehicle reaction.

Supplementary or alternative to is of particular advantage above solution switching to stoichiometric or bold Operation, then based on the prior art known surveillance methods is used. In advantageous Way this is done when the accelerator pedal is released. Again, it is advantageous if the supplied Fresh air volume dependent on control of the throttle valve of driver specification and speed is set so that there is an idling torque. Then exceed that currently calculated moment or the currently calculated power, this is how this error is recognized and countermeasures initiated.

In a particularly advantageous manner, when the pedal is released the maximum speed is used for monitoring and the Fresh air volume limited, either at the same time SC fuel supply is switched off or in special operating conditions, in which e.g. a shutdown above the Speed, for example, due to a hot catalytic converter or for comfort reasons e.g. not take place in first gear can, the stoichiometric operation is initiated. In Both cases are based on the well-known surveillance procedure based on the determined air supply.

drawing

The invention is described below with reference to the drawing illustrated embodiments explained in more detail. It shows FIG. 1 shows a control device for controlling an internal combustion engine, while in Figure 2 an embodiment the solution according to the invention as the flow diagram is preferred Embodiment of an internal combustion engine with gasoline direct injection is outlined. How this solution works is illustrated in Figure 3 using timing diagrams.

Description of exemplary embodiments

In Figure 1, a control unit 10 is shown, which as Elements at least one input circuit 12, at least one Microcomputer 14, an output circuit 16 and this one connecting communication system 18 includes. The input circuit 12 are input lines supplied via the signals supplied by corresponding measuring devices which represent company sizes or from which company sizes are derivable. Regarding the following The inventive solution described are one in FIG Input line 20 shown, which the control unit with a measuring device 22 which connects a the degree of actuation β representing the accelerator pedal size. Further an input line 24 is provided, which is from a Measuring device 26 originates and via which the engine speed NMOT representative size is supplied. Furthermore connects an input line 28 to the control unit 10 Measuring device 30, which is the supplied air mass HFM representing signal. An input line 32 leads from a measuring device 34 a size that the current IGES translation in the drive train corresponds. Further input lines 36 to 40 are provided, the operating variables representative signals from measuring devices Bring 42 to 46. Examples of such company sizes, the use in the control of the internal combustion engine find, are temperature variables, the position of the throttle valve angle, etc. Go to control the internal combustion engine in the embodiment shown in Figure 1 by the Output circuit 16 output lines 48 to 52 for control of the injection valves 54 and an output line 56 to control the throttle valve adjustable by electric motor 58 out. In addition, at least not shown Lines are provided to control the ignition.

On the basis of the degree of operation β of the accelerator pedal, the Fuel and air supply according to a predetermined Air / fuel ratio controlled. The latter can be lean be or during operation depending on the operating situation between a fat, an almost stoichiometric or change a lean attitude.

For the control of engines with gasoline direct injection according to the prior art mentioned at the Based on the degree of actuation β, a torque setpoint is formed, which in a value for the fuel mass to be injected is implemented. The conversion is done, for example taking into account the engine speed and the respective current operating mode. Switching between homogeneous and Shift operation takes place, for example, depending on the load condition the internal combustion engine. So the internal combustion engine e.g. with higher load in homogeneous operation, with low load, also operated at idle and at partial load in shift operation. In homogeneous operation it depends on the calculated Fuel mass taking into account the current operating status the internal combustion engine a target throttle valve angle calculated, depending on the electromotive adjustable throttle valve and thus the air supply is set to the internal combustion engine. In doing so, a predetermined one Setpoints for the air-fuel ratio are taken into account. The internal combustion engine works in shift operation unthrottled, i.e. with lean mixture composition. The throttle valve is not adjusted. Switching strategies between the two operating states are e.g. known from the prior art mentioned at the outset.

The control unit described in Figure 1 is used depending on the embodiment for the control of an intake manifold injection engine, the lean is operated, or to control a Engines with direct petrol injection.

The satisfactory functionality is in lean operation the comparison for monitoring the Function of the control of the internal combustion engine is not guaranteed. In order to make these control concepts satisfactory Provide monitoring of the control function, is provided, at least in a particular Operating state only an operation with stoichiometric or almost stoichiometric or with a rich air / fuel ratio or with limited fresh air supply. This allows the torque and power monitoring mentioned at the beginning satisfactory in this operating state be performed.

The at least one operating state is an operating state, in which the accelerator pedal is almost released, especially his position falls below a predetermined threshold and the engine speed exceeds a limit. Then only at least one of the operating modes shown above authorized. If deviations e.g. by virtue of If the torque monitoring is recognized, error measures are initiated. The speed is below the limit and / or the accelerator pedal position above the threshold operation with a lean air / fuel ratio is permitted. Monitoring by torque comparison takes place not instead.

In certain operating conditions, the engine speed is above a threshold value (e.g. 1500 rev / min), the Fuel supply switched off (overrun cut-off). simultaneously when operating with limited fresh air supply, the Throttle valve and thus the fresh air supply set so that there is an engine torque in the range of the idle torque would, if instead of the fuel cut-off e.g. as a result of a fault condition to the fresh air quantity or mass stoichiometric fuel quantity or mass injected would. For example, the throttle valve position is over a corresponding speed-dependent characteristic curve is set.

This also applies if the internal combustion engine with a stoichiometric or almost stoichiometric or with a rich air / fuel ratio is operated. This is especially the case if the fuel cut-off e.g. is not permitted for exhaust gas reasons, i.e. fuel is injected becomes. The fresh air volume or mass is also shown here and thus limits the amount or mass of fuel that there is a torque value in the range of the idling torque results. If the speed is below the threshold, The idle controller takes over the torque control.

During operation with stoichiometric or almost stoichiometric or with a rich air / fuel ratio or with limited fresh air supply, the known moment or performance comparison based on one from one measured, representing the fresh air quantity or mass Signal calculated comparison value instead. exceeds the comparison value the maximum allowable, the Power supply for the electrically controlled throttle valve switched off and / or the fuel supply is interrupted.

If the internal combustion engine is operated with gasoline direct injection, is used in shift operation for error detection in one first embodiment checks whether the accelerator pedal is in the idle position, i.e. completely released is. In this operating state, a maximum engine speed, For example, 1500 rev / min. exceeds the actual speed this maximum speed becomes the fuel supply switched off to the internal combustion engine until the engine speed drops below the maximum speed again. On increased rail pressure cannot have a negative impact, are undesired operating situations in this operating phase effectively avoided. In a supplementary embodiment a maximum speed is not only in idle mode, i.e. with the accelerator pedal released, specified, but in the entire accelerator pedal position range. There is a characteristic curve filed in which the maximum speed depends on the degree of actuation the accelerator pedal is read out. exceeds the actual speed is the maximum speed depending on the degree of actuation, the fuel supply is switched off as shown above.

Alternatively, in at least one operating state Shift operation, at least when the accelerator pedal is in neutral is switched to stoichiometric operation (λ = 1). In this operating state, the Torque comparison known from the prior art mentioned at the outset carried out. The fuel mass does not have to be taken into account are recognized so that possible error states and unwanted operating situations in this operating state be effectively avoided. Instead of torque monitoring is a corresponding monitoring of the performance of the internal combustion engine carried out.

These two measures can also be combined. there is the maximum speed comparison for shift operation carried out. In operating conditions in which a Fuel cut-off above the specified engine speed is not carried out, for example in operating states, in which the engine speed due to a hot Catalyst must be exceeded or for reasons of comfort, such as in first gear is switched to λ = 1 operation. In this particular one Operating situations is then the above torque or performance comparison used for error monitoring.

The result is a satisfactory monitoring of one Internal combustion engine with gasoline direct injection, wherein in Homogeneous operation the torque known from the prior art or performance monitoring is carried out.

A preferred embodiment for an internal combustion engine with gasoline direct injection is based on the flow chart a computer program is outlined in FIG. A corresponding one Program results from the application of the described Solution for intake manifold injectors.

The program is started at specified time intervals. In the first step 100, the necessary operating parameters such as degree of actuation β, engine speed NMOT, Gear ratio IGES and, if applicable, catalyst temperature TKAT read. In the subsequent step 102, by comparison the degree of actuation checked with a limit value, whether the accelerator pedal is in neutral (LL). If this is not the case, the program is ended and the initiated next time.

If this is the case, then step 104 checks whether a fuel cut-off above that when idling specified maximum speed of the accelerator pedal was not carried out would be. This will e.g. based on the gear ratio and / or the catalyst temperature. is the catalyst temperature is high and / or has the gear ratio when the first gear is engaged, the Shutdown not carried out. In this case, according to Step 106 switched to stoichiometric operation (λ = 1 operation) or the stoichiometric one already initiated Operation continued. Furthermore, at least for engine speed limits the fresh air supply above the idle range, in which the throttle valve is controlled accordingly. This will adjust the throttle and thus the fresh air supply ensures that an idle torque leads. This cannot be done incorrectly or the stoichiometric operation was not or not fully initiated, one is described as below an error detected. Instead of an almost stoichiometric one Adjustment can also be a rich adjustment of the mixture respectively. Thereupon in step 108, as is known based on the degree of operation of the accelerator pedal as well if necessary, other operating variables, the permissible torque MZUL as well as on the basis of air mass and other farm sizes the current actual torque MIST is determined. In the next Step 110 becomes the actual torque with the maximum allowable Moment compared. If the actual torque exceeds the maximum permissible torque, an error reaction becomes step 112 initiated, for example, the fuel supply is switched off and / or the electrically controllable throttle valve is de-energized connected. This is then reset by a device returned to their rest position. Exceeds that If the maximum torque is not the moment, the program will as ended after step 112 and at the next time performed again.

Step 104 has indicated that the fuel cut would be carried out above the limit speed so in step 114 the current engine speed NMOT with compared to the predetermined limit value N0. Exceeds the Engine speed this limit value, according to step 116 Fuel supply switched off. Furthermore, as described above the fresh air supply is limited. Then the program as in the case of a no answer in step 104 or continued with step 110.

In another exemplary embodiment, step 106 not λ = 1 operation, but operation with another predetermined λ value carried out, with the actual torque calculation the deviation of the λ value from 1 is taken into account becomes.

In homogeneous operation, in which the fuel mass during the Intake phase is injected, the mode of operation is like known in the context of torque or performance comparison checked so that the program shown in Figure 2 only when operating in shifts, i.e. when injected into the Compression phase is run through.

The embodiment described in Figure 2 is in Figure 3 using an exemplary operating situation with the help illustrated by time diagrams. Figure 3a shows the Course of the degree of actuation β over time, Figure 3b the the engine speed NMOT or the limit value N0 of the engine speed, Figure 3c the course of the maximum allowable torque MZUL and the actual torque MIST. In Figure 3d the Operating state Switch off the fuel supply using a bivalent signal over time.

First, the accelerator pedal is operated. Until time T0 (see FIG. 3a) the driver releases the pedal, so that from the Time T0 for the remaining time of the operating state shown the accelerator pedal is in neutral. The internal combustion engine is operated in shift operation. FIG. 3b shows how the engine speed changes NMOT (solid line) according to the driver specification (see Figure 3a) changed. At time T0 reached the idle speed. The limit speed N0 (dashed line). Exceeds at time T1 the engine speed is the limit value (see FIG. 3b), at time T2, the limit is again undershot. Therefore, between the times T1 and T2 according to FIG. 3d the fuel supply is switched off. The course is in FIG. 3c the maximum permissible torque (dashed line) and of the current actual torque (solid line). The actual torque and the maximum run before the time T0 permissible torque essentially according to the driver specification β. From time T0 it becomes for the idle state a maximum permissible torque is specified. At the times T1 and T2 becomes the check based on the engine speed curve carried out. After time T2 is on stoichiometric Operation switched. This means that in this Case monitoring based on the moment signals takes place. So exceeds the actual torque at the time T3 is the maximum permissible moment and falls below it Moment at time T4, then between times T3 and T4 the fuel supply is switched off (see FIG. 3d). The engine speed curve and the actual torque curve are for clarification recorded clearly separated from each other. In the second phase of operation, therefore, an overrun leads the limit speed by the engine speed does not become one Fuel cut-off, just exceeding it the maximum permissible torque by the actual torque at the time T3.

Claims (8)

1. Method of operating and monitoring an internal combustion engine, which is operated with a lean air/fuel ratio in at least one operating range, at least one variable representing the degree of actuation of the accelerator pedal and one variable representing the engine speed being detected, characterized in that, in at least one operating state in the operating range in which the internal combustion engine is operated with a lean air/fuel ratio, operation of the internal combustion engine is only permissible with an approximately stoichiometric or rich air/fuel ratio and/or with a limited air supply and monitoring of the operation of the internal combustion engine is carried out on the basis of at least one operating variable of the internal combustion engine if such operation of the internal combustion engine takes place.
2. Method according to Claim 1, characterized in that the air supply is adjusted in such a way during operation with an approximately stoichiometric or rich air/fuel ratio that a torque or power in the region of the idling value is obtained.
3. Method according to Claim 1, characterized in that, during operation with a limited air supply and the fuel supply cut off, the air supply is adjusted in such a way that an engine torque or engine power in the region of the idling value would be obtained if a fuel quantity that was approximately stoichiometric in relation to the air supply were injected.
4. Method according to one of the preceding claims, characterized in that the at least one operating state is determined as a function of the degree of actuation of the accelerator pedal and the engine speed, and is present, in particular, when an engine speed above a specified threshold value is present at a degree of actuation of the accelerator pedal below a specified threshold value, preferably close to the idling position.
5. Method according to one of the preceding claims, characterized in that a maximum permissible torque or a maximum permissible power is calculated in the at least one operating state, this value is compared with a comparison value and a fault is · detected if the comparison value exceeds the permissible value.
6. Method according to Claim 5, characterized in that the comparison value is calculated from at least one signal representing the current air supply.
7. Method according to Claim 5, characterized in that, when a fault is detected, the power supply to an electrically actuated throttle valve is interrupted and/or the fuel supply is interrupted.
8. Apparatus for operating and monitoring an internal combustion engine, which is operated with a lean air/fuel ratio in at least one operating range, with a control unit which detects at least one variable representing the degree of actuation of the accelerator pedal and one variable representing the engine speed, characterized in that, in at least one operating state in the operating range in which the internal combustion engine is operated with a lean air/fuel ratio, operation of the internal combustion engine is only permissible with an approximately stoichiometric or rich air/fuel ratio and/or with a limited air supply and the control unit has means for monitoring the operation of the internal combustion engine on the basis of at least one operating variable of the internal combustion engine, which carry out monitoring if such operation of the internal combustion engine takes place.

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