DE102015212154A1 - Method and device for operating a common rail fuel injection device, in particular of a motor vehicle - Google Patents

Abstract

The present invention relates to a method and a device for operating a fuel injection device, in particular of a motor vehicle, in which fuel is conveyed under high pressure into a high-pressure accumulator (1) whose pressure is controlled by means of a pressure control and from the fuel for injection via at least one fuel injection valve (14 ) is controlled by a control device (7), and in the means for detecting a mass balance violation of the high-pressure accumulator (1) supplied and from the high-pressure accumulator (1) discharged fuel amount are provided, wherein the fuel pressure in the high-pressure accumulator (1) by a predetermined Value (200) and wherein based on a detected mass balance violation (215), a dynamic decrease or limitation of the increased fuel pressure and / or the reduction of the torque of the internal combustion engine is performed (230).

Description

The invention relates to a method and a device for operating a common rail fuel injection device of an internal combustion engine, in particular of a motor vehicle according to the preambles of the respective independent claims. Furthermore, the present invention relates to a computer program, a machine-readable data carrier for storing the computer program and an electronic control unit, by means of which the method according to the invention can be carried out.

State of the art

An affected fuel injector goes out of the DE 196 25 487 A1 out. In this device, fuel under high pressure in a high-pressure accumulator, a so-called "Common Rail" (CR), promoted, the pressure of which is controlled by a control device arranged in a pressure regulator or a corresponding pressure control valve and from the fuel for injection via electrically controlled injectors ( "Injectors") is removed.

During operation of such an injection device, it may happen that the fuel quantity or fuel mass actually supplied to the high-pressure accumulator is, for example, not equal to the quantity which is provided for the fuel injection and is required for pressure regulation, for example due to aging effects of said injection valves. It is therefore out of the DE 10 2013 201 997 A1 known to perform at least temporarily a check of the fuel quantity balance in the high-pressure accumulator to determine if necessary corresponding mass balance violations, with a control pressure deviation of the pressure in the high-pressure accumulator is detected.

Such a recognized mass balance violation is known to be remedied by means of a Quantity Balance Adjustment (QBA). Such a QBA function includes a corresponding logic circuit, by means of which a torque controller is activated, which calculates a respective new permissible torque for the operation of the internal combustion engine.

The QBA functionality is suitable only for the presence of a particular standard fuel with a low-viscosity grade of fuel to effectively eliminate said mass balance violation, as the fuel injection and fuel combustion at this grade of fuel is little affected by a corresponding intervention. Now, however, the viscosity of the fuel is subject to considerable fluctuations in various markets or regions.

A named injection valve usually comprises a nozzle needle, which is operated by means of a nozzle closing control (NCC = Needle Closing Control) and thereby enables appropriate NCC interventions in order to counteract an approximately recognized quantity balance violation,

Disclosure of the invention

The invention is based initially on the idea that the above-mentioned aging behavior or effects affected injectors ("injectors") can be counteracted that in a CR fuel injection system of an internal combustion engine, or in a high-pressure fuel storage arranged there, the Fuel pressure or rail pressure is continuously raised over the life of the injector,

Such an increase in pressure can be carried out vehicle-specific, which can be achieved that over the life of the internal combustion engine or the injector naturally occurring coking particular called injectors and the associated extension of injection durations can be counteracted for a given injection quantity. Correspondingly necessary corrective interventions on the injector behavior are carried out on the basis of an intervention or closure control mentioned above of a nozzle needle of the respective injection valve on the basis of a named NCC control.

However, a named increase in the rail pressure is not taken into account or even counteracts this in the case of an initially mentioned quantity compensation control, which is said to compensate for the aging effects, in particular of the injection valves, and therefore leads to said mass balance violations.

One way to prevent such injection quantity violations despite the raised rail pressure would be a limitation of the maximum possible rail pressure for all types of vehicles. As a result, however, the effectiveness of increasing the rail pressure would be considerably reduced, since the weakest injection system with injection components which are the least dimensioned for the increased rail pressure, in particular injection valves, would decisively determine the height of the limited value of the rail pressure. In addition, the number of vehicles with such poorly designed injection systems is statistically significantly less than the number of vehicles equipped with higher quality injection components or systems.

Another way of preventing such injection quantity violations would be to reduce the maximum possible torque calculated by an initially mentioned torque controller with increased rail pressure. However, such torque reduction is associated with adverse effects on the driver or the ride comfort of the motor vehicle.

The method according to the invention proposes, in the case of a fuel injection device affected here, in which the rail pressure is raised as described, to carry out a preferably controlled, dynamic reduction or limitation of the raised rail pressure on the basis of a detected mass balance violation. Alternatively or additionally, a reduction of the torque (or torque) of the internal combustion engine can take place on the basis of a recognized mass balance violation. As a result, the rail pressure can be maintained at a maximum possible pressure level for the respective operating state of the internal combustion engine, without causing a mass balance violation.

The dynamic reduction of the rail pressure can take place with respect to the fuel injection device or of the motor vehicle, for example, specifically and / or as a function of a current operating point of the internal combustion engine. The said operating point is e.g. at a critical balance point operating point. This ensures that the lowering of the rail pressure only takes place up to a pressure level suitable for the respective injection system or motor vehicle or a present operating state of the internal combustion engine and thus a maximum possible pressure level is maintained.

The lowering of the rail pressure can be controlled or regulated, and based on the detection path of a QBA function mentioned above (QBA = Quantity Balance Adjustment), as it also uses a said torque controller. As a result, it can be ensured that the raised rail pressure is reduced only to the extent necessary for preventing a mass balance violation, with it being possible to reduce or even avoid a corresponding tolerance reserve.

It can also be provided that a prioritization of the rail pressure reduction or limitation takes place up to a predefinable NCC intervention limit (NCC = Needle Closing Control), wherein a possible mass balance violation is effectively prevented by cascaded reduction of the maximum retrievable at the internal combustion engine torque. As a result, it can be achieved that a named NCC intervention is not moment-effective and therefore does not imply a loss of comfort for the vehicle driver and, moreover, only low-viscosity fuels require a stated torque reduction.

It can further be provided that the dynamic reduction or limitation of the rail pressure takes place on the basis of a full load characteristic curve of the internal combustion engine. This ensures that a rail pressure reduction is always designed for full engine load of the internal combustion engine and is carried out with sufficient height accordingly. Because in full load operation of the internal combustion engine, the rail pressure drops known to be relatively strong.

The dynamic reduction or limitation of the rail pressure can also be done by Raildruckabsenkung using an integrally operating I-controller. This ensures that the rail pressure reduction causes only substantially smoothed rail pressure profiles and effectively avoids short-term rail pressure peaks or sinks, which would lead to a troubled operation of the internal combustion engine. With the method according to the invention, an initialization of the I-controller by an unnecessary dead travel and an overcorrection can be avoided.

Finally, permanent limitation of rail pressure caused by one-off effects in only one drive cycle can be prevented by debounce logic, which preferably minimizes the impact of such one-off effects when the engine is not in a potentially margin-critical operating range.

The device likewise proposed according to the invention comprises computing means for carrying out the described method and can therefore be implemented with relatively little implementation effort.

With the method and the device according to the invention can be ensured at the same time that the interventions in the setpoint correction also meet the strict requirements of the so-called "EGAS working group". These specifications relate to an already standardized safety concept for engine controls of gasoline and diesel engines, which in particular also the very strict safety requirements of the ASIL classification (ASIL = Automotive Safety Integrity Level, a in the ISO 26262 standard specified safety requirement level for safety-relevant systems in motor vehicles).

The method and the device proposed according to the invention also make it possible to cure a motor vehicle having a vehicle affected here during driving operation by raising the rail pressure Mass balance violation and thus the continued operation of the internal combustion engine or a motor vehicle having the internal combustion engine.

The invention can be used both in internal combustion engines of motor vehicles with a fuel injection device concerned here and in corresponding internal combustion engines of e.g. Industrial plants, for example, used in industrial process engineering internal combustion engines, with the advantages described herein are used.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

1 shows a fuel injection device according to the prior art.

2 shows a preferred embodiment of the method and the device according to the invention with reference to a combined block / flow diagram.

Description of exemplary embodiments

In the 1 is a high-pressure fuel storage 1 shown by a pipeline 2 from a fuel pump 3 coming from a fuel tank 4 Fuel sucks, is supplied with fuel, which is brought to high injection pressure. There are pressures that are substantially above 1000 bar. The pressure in the high-pressure fuel storage 1 is by a pressure transducer 6 detects its signal a control device 7 is supplied, by the above a fixed or a desired pressure, which may be dependent on a respective operating state of the associated internal combustion engine, by a corresponding signal, a pressure control valve 9 is controlled. This is located in a fuel return line 10 from the high-pressure fuel storage 1 to the fuel tank 4 ,

From high-pressure fuel storage 1 also carry pressure lines 11 off, each with a fuel injector 14 are connected, via which at the appropriate time in each case a desired amount of fuel can be injected to the internal combustion engine. The control of the amount of fuel injection by time and quantity also takes place via the control device 7 , which receives control signals for this control according to the speed and the load under which the associated internal combustion engine is to be operated. The control of this amount of fuel injection takes place, for example in a known manner by solenoid valves that control the connection between the high-pressure accumulator and the fuel injection valve. Possible occurring fuel control quantities, which flow back into the tank, can also via the return line 10 be returned to the tank.

The fuel pump 3 In this case, for example, it is driven synchronously with the internal combustion engine operated by the fuel injection device, that is to say with a rotational speed which is already detected for controlling the injection. The fuel pump 3 but can also be operated separately by a special drive, and thereby the relevant drive speed of the fuel pump 3 are also recorded, for. B. by a speed sensor 15 , With the help of this drive speed and the fact that the fuel pump 3 per revolution promotes a constant flow rate, the amount of fuel supplied in the high-pressure fuel accumulator can indirectly detect, so that can be dispensed with a flow meter for direct measurement of the amount of fuel delivered.

At the beginning of in 2 1, the fuel pressure (absolute rail pressure) in a prescribed high-pressure fuel accumulator is initially raised by an NCC (Nile Needle Closing Control) by an empirically predetermined value, as per Block 200 , In a subsequent first test step 205 It is checked whether the internal combustion engine is operated at the present time due to the Raildruckanhebung with respect to the currently metered amount of fuel and the current rail pressure (possibly as a function of engine speed) in a potentially margin critical operating range. The required operating (punkt-) data of the internal combustion engine are based on a block 210 provided.

One in the first test step 205 The test criterion to be used is, for example, the fuel quantity or fuel mass currently supplied to the high-pressure accumulator, which, as mentioned at the beginning, due to aging effects of a described injection valve 14 may deviate from the amount of fuel which is provided for the respective fuel injection and at a pressure control mentioned or pressure control 6 . 7 . 9 is taken as a basis. Because only from a certain size of the high pressure accumulator supplied amount of fuel, the operation of quantity balance is critical. In one In terms of volume balance-critical operating range, a rail pressure reduction described below is therefore not carried out.

Returns the first test step 205 in that the internal combustion engine is in a range-critical operating range, again before step 205 jumping back to the routine. However, if this condition is not met, in a subsequent second test step 215 Checked for an actual mass balance violation. The data to be used as a basis are provided by a recognition path, known per se, of a QBA function (QBA = Quantity Balance Adjustment) known per se. If this condition 215 is not met, it will be again before step 205 jumps back. Otherwise, in the subsequent step 220 an integral controller ("I-controller") is activated, by means of which a subsequently carried out dynamic or regulated rail pressure reduction or torque reduction takes place 230 ,

A named QBA function for detecting a mass balance violation is in the aforementioned DE 10 2013 201 997 A1 in the local 2 and the corresponding part of the description. The detection is based on a rail pressure control of one in the present 1 shown fuel high pressure accumulator 1 an internal combustion engine. In this case, rail pressure values supplied by a pressure sensor are recorded in, for example, regular intervals of, for example, 1/10 s intervals, and the control deviation in each case from a predetermined desired value is determined by means of the rail pressure regulator. The values of the system deviation recorded in this way can also be debounced in order to prevent, for example, transient processes in the high-pressure fuel storage 1 caused short-term pressure fluctuations are erroneously recognized as a mass balance violation and only recorded with a permanence events are taken into account.

In the method described there, values of the control pressure deviation detected and debounced in an empirically determined time window Δt _E are compared with a predetermined threshold value Δp _thres . Based on the time window .DELTA.t _E , the said permanence of the detected events is taken into account. If said threshold Δp _{thres is} not exceeded, it is further checked whether the time window Δt _E has not yet been exceeded. If this condition is met, another value of the control deviation is detected and evaluated as described above. However, if the time window has already been exceeded, the procedure is carried out again from the beginning. If the threshold Δp _thres is now _exceeded within the time window Δt _E , the presence of an actual _{mass balance violation} is assumed and, as described, in the second test step 215 based on.

By means of said dynamic or regulated rail pressure reduction by means of an I-regulator, it is ensured that, in particular, short-term rail pressure peaks or sinks are avoided by the rail pressure reduction, which would lead to uneven operation of the internal combustion engine. The initialization of the I-controller takes place in the present embodiment, both at a torque controller and at a pressure regulator, via a difference of each currently calculated desired value and each currently re-measured actual value at the time of activation of the two controllers. For the pressure regulator, this is the difference between a desired rail pressure and a currently measured rail pressure. For the torque controller, a current desired torque and a currently actually possible moment are evaluated. This difference, multiplied by an applicable percentage value between 0-100%, is used as the respective start value for the two controllers. If the two controllers have already been active in a previous drive cycle and the controller values that are already current are more negative than a specified initialization value, the existing value will continue to be accepted.

In connection with the described method for dynamic rail pressure reduction, an unnecessary dead travel and an overcorrection can be avoided during the initialization of the I controller.

The two regulators mentioned, i. the pressure regulator and the torque controller can be prioritized depending on a currently detected rail pressure with regard to their activation. Is e.g. the instantaneous rail pressure is higher than e.g. From an applicable characteristic curve "rail pressure over engine speed" predetermined threshold, the pressure regulator is first active. Only when the nominal value of the rail pressure falls below the specified threshold value and the mass balance violation still exists, the torque controller is activated and the pressure regulator is stopped.

The dynamic rail pressure reduction 230 also takes place on the basis of already mentioned operating point data 210 the internal combustion engine and required characteristics of the internal combustion engine 235 , It can also be provided that Raildruckabsenkung 230 so to speak by way of prioritization up to a predefinable, initially mentioned NCC intervention limit takes place, whereby a possible mass balance violation is effectively prevented by cascaded reduction of the maximum torque which can be called up by the internal combustion engine.

In addition, in order to prevent permanent limitation of the rail pressure caused by one-off effects occurring only in one drive cycle, a debounce logic may be provided, which preferably minimizes the influence of such unique effects when the internal combustion engine is not in a potentially margin critical operating range. This debounce logic compares a current actual value of the torque with a current torque limit. If the current actual value is lower than the torque limitation by an applicable offset, the controller input is switched to a negative deviation, which then causes the controller to run back, until the condition is met. The same applies to the pressure regulator. However, the pressure regulator compares whether the current rail pressure setpoint is lower by an offset than a corresponding pressure limitation.

The method described can be implemented in the form of a control program for an electronic control unit for controlling an internal combustion engine or a fuel injection system affected here or in the form of one or more corresponding electronic control units (ECUs).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19625487 A1 [0002]
• DE 102013201997 A1 [0003, 0033]

Cited non-patent literature

• ISO 26262 standard [0020]

Claims (14)

Method for operating a fuel injection device of an internal combustion engine, in particular of a motor vehicle, in which fuel is injected under high pressure into a high-pressure accumulator ( 1 ) is controlled, the pressure of which is controlled by means of a pressure control and from the fuel for injection via at least one fuel injection valve ( 14 ) controlled by a control device ( 7 ) and in the means for detecting a mass balance violation of the high-pressure accumulator ( 1 ) supplied and from the high-pressure accumulator ( 1 ) are provided, the fuel pressure in the high-pressure accumulator ( 1 ) is raised by a predefinable value ( 200 ) and based on a recognized mass balance violation ( 215 ) a dynamic reduction or limitation of the raised fuel pressure and / or a reduction of the torque of the internal combustion engine is performed ( 230 ). A method according to claim 1, characterized in that a mass balance violation based on control pressure deviation of the fuel pressure in the high-pressure accumulator ( 1 ) is recognized. A method according to claim 1 or 2, characterized in that the dynamic reduction or limitation of the raised fuel pressure and / or the reduction of the torque of the internal combustion engine takes place specifically for each individual ( 235 ). Method according to one of the preceding claims, characterized in that the dynamic reduction or limitation of the raised fuel pressure and / or the reduction of the torque of the internal combustion engine in dependence on a current operating point of the internal combustion engine takes place ( 210 ). Method according to claim 4, characterized in that at the current operating point ( 210 ) is a critical balance point operating point. Method according to one of the preceding claims, characterized in that the dynamic reduction or limitation of the raised fuel pressure and / or the reduction of the torque of the internal combustion engine, on the basis of a recognition path of an existing Quantity Balance Adjustment function, is controlled or regulated. Method according to one of the preceding claims, characterized in that a prioritization of the dynamic reduction or limitation of the raised fuel pressure and / or the reduction of the torque of the internal combustion engine takes place up to a predefinable Needle Closing Control intervention limit, wherein a possible mass balance violation by cascaded reduction of an the engine maximum retrievable torque is prevented. Method according to one of the preceding claims, characterized in that the dynamic reduction or limitation of the raised fuel pressure and / or the reduction of the torque of the internal combustion engine based on a full load characteristic ( 225 ) of the internal combustion engine takes place. Method according to one of the preceding claims, characterized in that the dynamic reduction or limitation of the raised fuel pressure and / or the reduction of the torque of the internal combustion engine by means of an integrally operating regulator ( 220 ) he follows. Method according to one of the preceding claims, characterized in that the dynamic reduction or limitation of the raised fuel pressure and / or the reduction of the torque of the internal combustion engine takes place by means of a debounce logic. A computer program that performs all the steps of a method according to any one of claims 1 to 10 when running on a computing device or controller. A machine-readable storage medium on which a computer program according to claim 11 is stored. Electronic control device, which is set up to a fuel injection device, in particular of a motor vehicle, in the fuel under high pressure in a high-pressure accumulator ( 1 ) is controlled, the pressure of which is controlled by means of a pressure control and from the fuel for injection via at least one fuel injection valve ( 14 ) controlled by a control device ( 7 ) is controlled by means of a method according to one of claims 1 to 10. Fuel injection device, characterized by computing means for carrying out the method according to one of claims 1 to 10.

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