EP0923665B1 - Method for operating an internal combustion engine, in particular for a motor vehicle - Google Patents

Description

The invention relates to a method for operating a Internal combustion engine, in particular of a motor vehicle, at the fuel either in a first mode of operation a compression phase or in a second operating mode directly into a combustion chamber during an intake phase is injected, and in which the in the combustion chamber injected fuel mass in the two operating modes inter alia depending on a calculated, of controlled the target engine to be delivered torque and / or is regulated. The invention further relates to a control device for an internal combustion engine or a Internal combustion engine, in particular for a motor vehicle, with an injector, with fuel in either one first operating mode during a compression phase or in a second operating mode directly during an intake phase is injectable into a combustion chamber, and with a Control device for controlling and / or regulating the in the Fuel chamber injected fuel mass in the two Operating modes depending on one calculated, to be delivered by the internal combustion engine Target torque.

Such systems for the direct injection of fuel in the combustion chamber of an internal combustion engine are from the EP 538 890 A2 known.

Further state of the art can be found in FR-2739331 A1 out.

It is the so-called first operating mode Shift operation and a so-called second operating mode Differentiated homogeneous operation. The shift operation is used especially for smaller loads during the Homogeneous operation with larger ones on the internal combustion engine applied loads is used. In shifts the fuel is used during the compression phase Internal combustion engine in the combustion chamber, namely there in the injected in the immediate vicinity of a spark plug. This has the consequence that no even distribution of the Fuel can take place in the combustion chamber more. The The advantage of shift operation is that with a very low fuel mass the adjacent smaller loads executed by the internal combustion engine can be. However, larger loads cannot pass through the shift operation can be fulfilled. Im for such bigger ones The fuel is provided for homogeneous operation during the intake phase of the internal combustion engine injected so that a swirl and thus a Distribution of the fuel in the combustion chamber still without further can be done. To that extent corresponds to Homogeneous operation such as the operation of Internal combustion engines in the conventional way Fuel is injected into the intake pipe.

In both operating modes, i.e. in shift operation and in Homogeneous operation, the fuel mass to be injected from a control device as a function of a plurality from input variables to one with regard to Saving fuel, reducing emissions and the like optimal value controlled and / or regulated. This control and / or regulation depends among other things on a target torque that is calculated by the control unit. The target torque is that of the internal combustion engine total moment to be delivered, i.e. the moment that the internal combustion engine should generate. This target torque consists among other things of what the driver desires Moment and possibly other Torque requirements for example of an air conditioning system or the like together. The moment requested by the driver is determined from the position of the driver Accelerator pedal derived.

It is now possible that when calculating the target torque from the input variables mentioned by the control unit Error occurs. This can be a mistake Sensor and / or the control unit and / or the like act. In particular, it can be a software error act on the control unit due to the rare Occurrence of the error has not yet been recognized is.

The object of the invention is to provide a method with which an error in the calculation of the target torque can be recognized.

This task is carried out in a process or in a Control unit or the internal combustion engine at the beginning mentioned type according to the invention by claims 1 or 9 or 10 solved.

There is therefore a comparison of the determined output Actual torque with a determined permissible moment carried out. The actual torque and also the permissible torque are possibly faulty regardless of that calculated target torque. For this reason, one can Error of the target torque is not based on the comparison mentioned impact. Depending on the comparison then decided whether the target torque is faulty or Not.

The method according to the invention thus enables the to check or to calculate the target torque calculated by the control unit monitor. It can be determined from the comparison whether the target torque is correct or incorrect from that Control unit has been calculated. Through this review and the detection of an error in the Calculation of the target torque can result from this faulty fuel injection into the combustion chambers the internal combustion engine can be prevented. This carries directly for fuel saving and exhaust gas reduction as well as for an overall better operation of the Internal combustion engine at.

According to the invention, a special function is started when the actual torque is greater than the permissible torque. The permissible torque therefore represents a maximum value that from the actual moment per se must not be exceeded. However, the actual torque is greater than the one mentioned Maximum value, for example, with the special function started an error routine or the like with which either the control unit tries to get the error through appropriate corrections, for example from Fix parameters or the like, or by the Driver or a mechanic alerted to the fault is made.

According to the invention, the actual torque is used up Oxygen mass determined. In this way it is possible to calculate the actual torque very precisely. From the then to Available oxygen mass can be used then the burned fuel mass and again the actual moment can be concluded.

In an advantageous development of the invention the mass of oxygen consumed from the supplied Fresh air and the oxygen remaining in the exhaust gas determined. In particular, the difference is formed from the oxygen content of the fresh air supplied and the remaining oxygen mass in the exhaust gas. This represents one simple, yet very accurate and effective way represents the burned oxygen mass and thus ultimately that Actual torque of the internal combustion engine to be calculated.

It is particularly useful if the fresh air from one Air mass sensor and the oxygen remaining in the exhaust gas is measured by a lambda sensor. The air mass sensor and the lambda sensor are usually for other purposes already provided in the internal combustion engine, so that insofar as no additional components for the checking or monitoring of the invention Target torque are required.

In an advantageous embodiment of the invention a recirculation of exhaust gas when determining the burned oxygen mass considered. So it will takes into account that this about the repatriation Exhaust gas fed to combustion chambers has a low Has a direct oxygen content than that of the combustion chambers fresh air supplied, and that due to the recirculated Exhaust gas, the proportion of fresh air supplied is lower. This in turn has the advantage that the tolerance of the Fresh air measuring air mass sensor also supplied plays a minor role.

In an advantageous embodiment of the invention the actual torque from the burned fuel mass determined. This will make a very accurate calculation of the actual torque. The burned can Fuel mass, for example, from the injectors driving signals derived or by other Operating parameters of the internal combustion engine are determined.

In advantageous developments of the invention permissible moment from a driver in particular requested torque and / or from a speed of the Internal combustion engine determined. This represents a simple, but still represent the permissible in an accurate and effective manner Moment to calculate. In particular, one can in this way Maximum value as a function of that from the driver desired moment that are exceeded this maximum value by that of the internal combustion engine output actual value on an error of the control unit calculated target value.

It is particularly useful if the requested moment from an accelerator pedal sensor and the speed from one Speed sensor is measured. The accelerator pedal sensor and the Speed sensors are usually already used for other purposes provided in the internal combustion engine, so that in this respect no additional components for the invention Check or monitoring of the target torque required are.

Figur 1

zeigt ein schematisches Blockschaltbild eines Ausführungsbeispiels einer erfindungsgemäßen Brennkraftmaschine eines Kraftfahrzeugs, und

Figur 2

zeigt ein schematisches Blockschaltbild eines Ausführungsbeispiels eines erfindungsgemäßen Verfahrens zum Betreiben der Brennkraftmaschine nach der Figur 1.

Further features, possible applications and advantages of the invention result from the following description of exemplary embodiments of the invention, which are shown in the figures of the drawing. All of the features described or illustrated, individually or in any combination, form the subject matter of the invention, regardless of their summary in the patent claims or their dependency, and regardless of their formulation or representation in the description or in the drawing.

Figure 1

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

Figure 2

shows a schematic block diagram of an embodiment of a method according to the invention for operating the internal combustion engine according to FIG. 1.

1 shows an internal combustion engine 1, in which a piston 2 in a cylinder 3 back and forth is movable. The cylinder 3 has a combustion chamber 4 provided, on the valves 5, an intake pipe 6 and Exhaust pipe 7 are connected. Furthermore are the Combustion chamber 4 can be controlled with a signal TI Injector 8 and a spark plug 9 assigned. The Exhaust pipe 7 is via an exhaust gas recirculation line 10 and with a signal EGR controllable exhaust gas recirculation valve 11 with connected to the intake pipe 6.

The intake pipe 6 is with an air mass sensor 12 and that Exhaust pipe 7 is provided with a lambda sensor 13. The Air mass sensor measures the air mass flow of the Intake pipe 6 supplied fresh air and generated in Depending on this, a signal LM. The lambda sensor 13 measures the oxygen content of the exhaust gas in the exhaust pipe 7 and generates a signal λ depending on this.

In a first operating mode, the shift operation of the Internal combustion engine 1, the fuel from the Injector 8 during a piston 2 compression phase in the combustion chamber 4 injected, locally in the immediate vicinity the spark plug 9 as well as immediately before the upper one Dead center of the piston 2. Then, using the spark plug 9 the fuel ignites so that the piston 2 in the now following work phase by the expansion of the ignited fuel is driven.

In a second operating mode, the homogeneous operation of the Internal combustion engine 1, the fuel from the Injector 8 during a piston 2 induced suction phase in the combustion chamber 4 injected. Through the air sucked in at the same time the injected fuel swirls and thus in the Combustion chamber 4 is distributed substantially uniformly. After that the fuel-air mixture during the Compression phase compressed to then from the spark plug 9 to be ignited. By the expansion of the inflamed The piston 2 is driven by fuel.

In shift operation, as in homogeneous operation, is by the driven piston a crankshaft 14 in one Offset over which ultimately the wheels of the Motor vehicle is driven. The crankshaft 14 is a Speed sensor 15 assigned, which depending on the Rotation of the crankshaft 14 generates a signal N.

The in the shift operation and in the homogeneous operation of the Injection valve 8 injected into the combustion chamber 4 Fuel mass is in particular from a control unit 16 in terms of low fuel consumption and / or controlled and / or regulated low emissions. For this purpose, the control unit 16 is equipped with a Microprocessor provided in a storage medium, a program especially in a read-only memory has saved, which is suitable for the named Control and / or regulation to perform.

The control unit 16 is acted upon by input signals, the operating variables measured by sensors Represent internal combustion engine. For example, that is Control unit 16 with the air mass sensor 12, the Lambda sensor 13 and the speed sensor 15 connected. Of the control unit 16 is also provided with an accelerator pedal sensor 17 connected, which generates a signal FP, the position indicates an accelerator pedal which can be actuated by a driver. The Control unit 16 generates output signals with which over Actuators the behavior of the internal combustion engine accordingly the desired control and / or regulation influenced can be. For example, the control unit 16 with the Injector 8, the spark plug 9 and the Exhaust gas recirculation valve 11 connected and generates the Control necessary signals.

The control and / or regulation, for example, the injected into the combustion chamber 4 fuel mass is performed by the control unit 16 _{is to} in the two operating modes, inter alia, a function of a setpoint torque M. This setpoint torque represents the torque that the internal combustion engine 1 is to deliver or generate. The setpoint torque to be output is calculated by the control unit 16 as a function of the torque requested by the driver and of further torque requests from the internal combustion engine 1. The torque requested by the driver results from the position of the accelerator pedal sensor 17 and other torque requirements, for example from an air conditioning system, can be derived from corresponding changes in the speed N of the internal combustion engine 1.

The control performed by the controller 16 and / or regulation now causes an actually emitted actual torque M _is substantially the calculated torque M _{is to} be dispensed target is tracked. In essence, therefore, corresponds to the actual torque M _is the setpoint torque M _soll.

It is now possible that with the calculation described of the target torque to be output by the control unit 16 Error occurs. A method is shown in FIG with which such an error can be detected can. The method is controlled by the control unit 16 carried out. It is possible that the procedure especially regularly at certain intervals and or. each time the internal combustion engine is started 1 and / or other special events during the Operation of the internal combustion engine 1 is started.

In a block 18, the control unit 16 converts the Signal FP for the position of the accelerator pedal and from the Speed N of internal combustion engine 1 is a permissible torque zM determined. This permissible moment zM is from the Control unit 16 calculated such that the Torque request from the driver and all other Torque requirements of the internal combustion engine 1 are taken into account. Furthermore, the calculation of the permissible moment a delta value is permitted be added to the total torque requirements and with the possible tolerances of sensors and the like are taken into account.

In a block 19, the control unit 16 calculates a combusted fuel mass vK from the signal LM of the air mass sensor 12 and the signal λ of the lambda sensor 13, from which the actual torque M _{ist is} then calculated by the control unit 16 in a block 20.

The burned fuel mass vK is from the control unit 16 ultimately calculated from the burned oxygen mass. This burned oxygen mass is in turn from the Control unit 16 in block 19 from intake manifold 6 fresh air supplied and that remaining in the exhaust gas and thus calculates unburned oxygen. The Oxygen content of the intake pipe 6 supplied Fresh air is measured by the air mass sensor 12 and can thus from the control unit 16 via the signal LM be taken into account. The oxygen content of the in the exhaust gas remaining oxygen is from the lambda sensor 13 measured and can therefore by the control unit 16 via the Signal λ are taken into account.

vK = verbrannte Kraftstoffmasse

mL = Luftmasse aus Signal LM

mAGR = rückgeführte Abgasmasse

k = 14,8 bei Luft-Kraftstoff-Verhältnis λ=1.

In block 19, the control unit 16 calculates the burned fuel mass vK from the signal LM and the signal λ according to the following equation: vK = mL k · λ + mAGR ( 1 λ - 1 λ ' ) With:

vK = mass of fuel burned

mL = air mass from signal LM

mAGR = recirculated exhaust gas mass

k = 14.8 with air-fuel ratio λ = 1.

With the first summand of the equation, the burned Fuel mass vK from that measured via the signal LM Air mass mL and calculated from the signal λ, the one The function of the oxygen concentration of the exhaust gas is. This Calculation refers to the stationary operation of the Internal combustion engine 1.

The second summand is representative of the Storage capacity of oxygen in the recycled Exhaust. Here λ 'is the air-fuel ratio previous combustion. Furthermore, it is with mAGR by a setpoint. If this is not set then there is an error and an error occurs associated error response. It is also possible to use mAGR derived from measurements, for example from the pressure in the Intake pipe 6 and the local air mass flow or from the Opening ratio of the throttle valve and the Exhaust gas recirculation valve 11. The second summand relates on the transient operation of the internal combustion engine 1.

The control unit 16 then derives the delivered actual torque M _{ist from} the internal combustion engine 1 in block 20 from the burned fuel mass vK calculated in this way. This actual torque M _ist is essentially proportional to the burned fuel mass vK. _Is at the actual torque M If it is actually generated by the internal combustion engine 1 including the moment of friction losses. The actual torque M _is the control device can be used 16 also for other calculations.

In a block 21, the control unit 16 compares the allowable moment zM with the actually discharged from the internal combustion engine 1, the actual torque M _is generated in response to this comparison, a signal F. If the actual torque M _is less than the permissible torque zM, so is the signal F, for example, "0", while in the opposite case, ie if the actual torque M _is greater than the permissible torque zM, the signal F is "1".

Is the actual torque M _is, this means that the product calculated by the controller 16 to be dispensed setpoint torque M _soll of which ultimately _is actually delivered actual torque M depends smaller than the permissible torque zM about the processing performed by the control apparatus 16 control or regulation, is at least in a plausible range of values. The control unit 16 can conclude that the calculation of the target torque is at least not fundamentally wrong. In this case, no further measures are taken by control unit 16.

However, if the actual torque M _is greater than the permissible torque zM, this means that the setpoint torque to be output initially calculated by the control unit 16 is too large and therefore has an error. This error then has the consequence that the control or. Regulation also the actual torque M _is actually too great and therefore exceeds the permissible torque zM. This error is recognized by the control unit 16 by the signal F = 1.

The control unit 16 then starts a special function, for example an error routine. This error routine, for example, parameters of the internal combustion engine 1, the actually delivered actual torque M _is influence by the controller 16 in the sense of a reduction of the actual torque M _is to be changed. It is also possible that the error routine informs the driver of the motor vehicle of the error by means of a corresponding display. It is also possible for the error routine to make a corresponding entry in a memory, which is then read out by the workshop staff when the motor vehicle is being repaired or serviced, in order to bring the error to the attention in this way.

Furthermore, a minimum permissible torque can be determined depending on the position of the accelerator pedal. If the actual torque M _is less than this minimum torque and the target torque M target _is greater than the minimum torque, an error can also be inferred from this and appropriate measures can be initiated.

Claims (12)

1. Method for operating an internal-combustion engine (1), in particular of a motor vehicle, in which fuel is injected directly into a combustion chamber (4) either in a first operating mode during a compression phase or in a second operating mode during an induction phase, and in which the mass of fuel which is injected into the combustion chamber (4) in the two operating modes is controlled, inter alia, as a function of a calculated desired moment which is to be delivered by the internal-combustion engine (1), characterized in that an actual moment (M_actual) which is delivered by the internal-combustion engine (1) and a permissible moment (zM) are determined (18 and 19, 20, respectively), in that the actual moment (M_actual) is compared (21) with the permissible moment (zM), in that a special function is initiated if the actual moment, (M_actual) is higher than the permissible moment (zM), and in that the actual moment (M_actual) is determined from the mass of oxygen consumed.
2. Method according to Claim 1, characterized in that the mass of oxygen consumed is determined from the fresh air supplied and the oxygen which remains in the exhaust gas.
3. Method according to Claim 2, characterized in that the fresh air is measured by an air mass sensor (12), and the oxygen which remains in the exhaust gas is measured by a lambda sensor (13).
4. Method according to one of the preceding claims, characterized in that a recirculation of exhaust gas is taken into account when determining the mass of oxygen consumed.
5. Method according to one of the preceding claims, characterized in that the actual moment (M_actual) is determined from the mass of fuel consumed (vK).
6. Method according to one of the preceding claims, characterized in that the permissible moment (zM) is determined from a moment which is requested in particular by a driver.
7. Method according to one of the preceding claims, characterized in that the permissible moment (zM) is determined from a rotational speed (N) of the internal-combustion engine (1).
8. Method according to Claim 6 and Claim 7, characterized in that the requested moment is measured by an accelerator-pedal sensor (17), and the rotational speed is measured by a rotational-speed sensor (15).
9. Control unit (16) for an internal-combustion engine (1), in particular for a motor vehicle, the internal-combustion engine (1) being provided with an injection valve (8), by means of which fuel can be injected directly into a combustion chamber (4) of the internal-combustion engine (1) either in a first operating mode during a compression phase or in a second operating mode during an induction phase, and the control unit (16) being provided for controlling the mass of fuel injected into the combustion chamber (4) in the two operating modes, inter alia, as a function of a calculated desired moment which is to be delivered by the internal-combustion engine, characterized in that the control unit (16) determines an actual moment (M_actual) which is delivered by the internal-combustion engine (1) and a permissible moment (zM), in that the actual moment (M_actual) is compared with the permissible moment (zM), in that a special function is initiated if the actual moment (M_actual) is greater than the permissible moment (zM), and in that the actual moment (M_actual) is determined from the mass of oxygen consumed.
10. Internal-combustion engine (1), in particular for a motor vehicle, having an injection valve (8), by means of which fuel can be injected directly into a combustion chamber (4) either in a first operating mode during a compression phase or in a second operating mode during an induction phase, and having a control unit (16) for controlling the mass of fuel injected into the combustion chamber (4) in the two operating modes, inter alia, as a function of a calculated desired moment which is to be delivered by the internal-combustion engine, characterized in that the control unit (16) determines an actual moment (M_actual) delivered by the internal-combustion engine (1) and a permissible moment (zM), in that the actual moment (M_actual) is compared with the permissible moment (zM), in that a special function is initiated if the actual moment (M_actual) is greater than the permissible moment (zM), and in that the actual moment (M_actual) is determined from the mass of oxygen consumed.
11. Internal-combustion engine (1) according to Claim 10, characterized in that an air mass sensor (12) and lambda sensor (13) are provided.
12. Internal-combustion engine (1) according to one of Claims 10 or 11, characterized in that an accelerator-pedal sensor (17) and a rotational-speed sensor (15) are provided.

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