WO2012159841A2

WO2012159841A2 - Method for operating an internal combustion engine

Info

Publication number: WO2012159841A2
Application number: PCT/EP2012/057547
Authority: WO
Inventors: David Vitre
Original assignee: Robert Bosch Gmbh
Priority date: 2011-05-23
Filing date: 2012-04-25
Publication date: 2012-11-29
Also published as: DE102011076258A1; CN103562532A; WO2012159841A3; KR101858785B1; KR20140035915A; EP2715095A2; CN103562532B

Abstract

The invention relates to a method and to assembly for operating an internal combustion engine having common rail injection. In the method, fuel is introduced into the rail by means of a high-pressure pump, wherein the high-pressure pump is actuated by a metering unit that receives a control value (58) therefore, the control value (58) being determined on the basis of a pilot control (22, 24) such that a control of the metering unit is carried out.

Description

description

title

Method for operating an internal combustion engine The invention relates to a method for operating an internal combustion engine with

Memory injection and an arrangement for carrying out the method.

BACKGROUND OF THE INVENTION In internal combustion engines, the operation of which utilizes accumulator injection, also referred to as common rail injection, employs single-tip systems in which a high-pressure pump brings the fuel to a high pressure level. The pressurized fuel is in a pressure accumulator, which is permanently under pressure during operation.

In this way, a complete separation of the pressure generation from the injection process is possible, the injection is controlled exclusively by maps, the injection timing and the injection quantity are controlled by an electronic engine control. Fuel in the pressure accumulator or rail is injected into combustion chambers via injection valves. To the

Therefore, to maintain pressure in the rail, fuel is supplied to the rail continuously or at regular intervals via a high pressure pump controlled by a metering unit (MPROP). For this purpose, the metering unit receives a control value which is based on an output value of a regulation of the pressure in the pressure feed, wherein the control in turn receives a signal from a pressure sensor which detects the pressure in the rail.

The pressure in the rail is thus monitored or regulated with the pressure sensor or rail pressure sensor in order to always keep the desired pressure in the rail. In some injection systems, a pressure control valve is additionally provided, which also allows regulation of the pressure in the rail. From the document DE 10 2010 0298 40 A1 a method for operating an internal combustion engine is known, in which unwanted pressure deviations can be avoided. In this case, a change in the driver's request is detected. As a result of the change in the driver's request, a pressure correction value is determined and a control signal, which is fed to a controlled system, is changed as a function of the pressure correction value.

In a common rail system with a regulator in the metering unit (MPROP) for the high pressure pump and with a rail without pressure control valve, the rail pressure can not be set sufficiently accurately with the software currently being used in the event of a defective rail pressure sensor. Such a system is also called a 1-controller system. A 2-controller system has a regulator in the Zumessteil and additionally a pressure control valve. Consequently, the injection quantity, which depends in particular on the rail pressure, no longer corresponds exactly to the driver's intention, since the rail pressure without the rail pressure sensor is not detected.

In case of failure of the rail pressure sensor, it is therefore previously provided in injection systems without pressure control valve to stop the engine. This means that the vehicle can not be operated only due to the failure of the rail pressure sensor. However, this reaction is unacceptable to many vehicle manufacturers. If a parking is omitted, however, a significantly reduced driving behavior must be expected.

Disclosure of the invention

Against this background, a method according to claim 1 and an arrangement with the features of claim 9 are presented. Embodiments result from the dependent claims and the description.

The proposed method makes it possible to operate the internal combustion engine without a rail pressure sensor, since a control of the metering unit and thus a control of the amount of fuel introduced into the rail is carried out based on a control value which is determined on the basis of pilot control. In the presented method for operating an internal combustion engine, at least one emergency driving function can be ensured in an embodiment starting from a regulated operation with a rail pressure sensor in the event of failure of the rail pressure sensor. With a slight adjustment of the software function and with a learned correction function, a significantly improved rail pressure control can be achieved without

Rail pressure sensor and thus improve the driving behavior can be achieved.

In case of failure of the rail pressure sensor is thus switched from a regulated operation to a controlled operation. This means that over the

Metering unit supplied in the rail amount of fuel is no longer regulated based on a signal from the rail pressure sensor, but is controlled. For this purpose, a control value is determined, which is determined on the basis of a feedforward control and possibly taking into account an adaptive metering curve (AMC: Adaptive Metering Curve) as a correction function. At idle, an additional feedforward control can also be taken into account. In this case, an idle controller can deliver a signal that is used to control the metering unit.

The AMC is typically learned in the metering unit during trouble-free operation, and thus typically also continually adapted. The AMC takes into account a volumetric flow difference between the nominal system demand (nominal physical feed forward) and the manipulated variable of the metering unit during control operation. 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 specified, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

FIG. 1 shows the sequence of an embodiment of the described method. FIG. 2 shows an embodiment of the described arrangement.

EMBODIMENTS OF THE INVENTION The invention is schematically illustrated by means of embodiments in the drawings and will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the presented method with reference to a flowchart. The sequence is divided into four parts, namely part A 10, part B 12, part C 14 and part D 16. The illustration shows the determination of a control value for the metering unit (MPROP) in the event that in the case of failure of the rail pressure sensor of a regulated operation in a controlled operation must be switched.

In part A 10, a switch 20 is shown, with which can be switched between a nominal physical feedforward control 22 and a minimum physical feedforward control 24. In Part B 12, a correction is made with the learning value of an adaptive one

Zumesskurve (AMC) 30, if available.

In part C 14, a pump tolerance 40 can be taken into account, in particular depending on whether the AMC 30 could already be learned or not.

In part D 16, a switch 50 is provided, which can switch on an additional pilot 52, when the internal combustion engine is idling 54. This results in an output 56, the manipulated variable 58 for the control of the metering unit.

It has been recognized that it is possible to continue the motor vehicle without a pressure sensor, in this case without a rail pressure sensor, by carrying out a rail pressure control.

However, the following two problems arise: 1 . The driving behavior is highly dependent on the system tolerance, ie the tolerance of the control amount and leakage amount of the injectors, the tolerance of the injection quantity and the tolerance of the pump characteristic and the control units. 2. In particular, it should be noted that the rail pressure control in idle is insufficient because the idle controller engages. In normal operation, the rail pressure finds a stable point, despite an integrative behavior of the control unit of the metering unit (MPROP) for the high-pressure pump, because the injection quantity increases or decreases, as the rail pressure in the pressure accumulator or rail increases or decreases, although the rail pressure, how the control unit conveys, remains the same. At idle, the idle controller reacts against this injection quantity variation.

The first problem is addressed as follows:

1 . The use of a physical feedforward controller 22 or 24 in Part A 10.

2. The determination of a minimum system requirement in order to introduce too little rather than too much into the rail. Just as the physical feedforward control determines a maximum system requirement from a nominal system requirement, a minimum system requirement can be determined. This occurs when a shutdown is desired rather than too much injection quantity. This is done in part A 10.

Under nominal pilot control, the computational determination of the volumetric flow demand, which must deliver the high-pressure pump into the rail, is to be understood. The injection quantity and the speed are known. This can be the

Volume flow can be calculated. From the injection quantity, the control quantity, that is to say the quantities for actuation, namely opening and closing, of the injector can be calculated. The injector leakage is also measurable for a nominal system and is stored in the form of a map in the control unit.

The injection quantities, the control amounts and the injector leakages are known and have a certain tolerance. These tolerances are taken into account in the calculation in order to calculate the volumetric flow requirement of a system with the lowest requirement as the minimum feedforward control. Basically, the pilot control is dependent on the injection quantity, which in turn depends on the engine speed, thus one can estimate how much fuel has to be introduced into the rail. 3. The use of AMC 30 correction to reduce the influence of component tolerance. This requires knowledge of the AMC learning tolerance. This is done in part B 12.

4. The reduction of the pump demand from the known tolerance of the pump characteristic curve or the pump tolerance 40, in turn, to promote rather less than too much in the rail. This is done in part C 14.

With regard to the second problem, an additional feedforward control 52 can be added depending on the injection quantity in idle 54. If the idle controller reduces the injection rate to below the normal idle demand, it means that the rail pressure is higher than expected and that the pump is over-delivering. This additional pilot control must then reduce the pump delivery quantity if the injection quantity increases and vice versa. This is done in Part D 16.

At the output 56 results in a value that is used directly as a control value 58 for the metering unit. The parts A 10 to D 16 can be independently examined, evaluated and used. The first switch 20 and the pump tolerance 40 may be used in consideration of the manufacturer's safety regulations.

In the presented method, a transition from a controlled to a controlled mode takes place in an embodiment when a defect of the

Rail pressure sensor was detected. In the event of a defect, the control value of the metering unit should be from the controller output value to that shown in FIG

Exit 56 jump. In order to avoid a jump in the rail pressure, a ramp start value can be initialized so that the control value of the metering unit does not make a jump. So the starting value of the ramp can be the last one

Controller output value (without P component) minus the value 58 at output 56. The ramp output is added to the output 56 and then gradually lowered to zero. The P component is used for the initialization of the ramp not used because the pressure regulator deviation may be implausible if the rail pressure sensor is detected as defective.

In Figure 2, a pressure accumulator or rail 80 of an internal combustion engine is shown, in which there is pressurized fuel via a first injection valve 82, a second injection valve 84, a third injection valve 86 and a fourth injection valve 88 in combustion chambers, such as. Cylinder of the internal combustion engine, can be injected. To simplify the illustration, only the third injection valve 86 is shown in detail in FIG.

Furthermore, a rail pressure sensor 90 is provided on the rail 80, which detects the pressure in the rail 80 and outputs a signal 92 representing the pressure. This signal 92, in addition to a second signal 94 from an accelerator pedal 96, a third signal 98 from a crankshaft 100, a fourth signal 102 from a camshaft 104 and at least one further signal 106 from further sensors in a control unit 120 a. This control device 120 controls actuators provided via a first output 122, the injection valves 82 to 88 via a second output 124 and a third output 126 via a second output 124

Metering unit 130 of a high-pressure pump 132 which supplies fuel 146 to the rail 80 via a line 134.

Furthermore, the illustration shows a fuel filter 140, a check valve 142 and a tank 144 in which fuel 146 is located. Furthermore, an electric pre-supply pump 150 and a pre-filter 152 are provided in the tank 144.

In fault-free operation, the rail pressure sensor 90 thus supplies the signal 92, which is used to control the metering unit 130 and thus to control the fuel discharged from the high-pressure pump 132 into the rail. If the rail pressure sensor 90 fails, a value is calculated by the control unit 120, as has been explained in connection with FIG. 1, which is used as the control value for the

Control of the metering unit is used.

Claims

claims

1 . Method for operating an internal combustion engine with a memory injection, in which by means of a high-pressure pump (132) fuel is introduced into a rail (80), wherein the high-pressure pump (132) of a

Metering unit (130) is actuated, which receives for this purpose a control value (58) which is determined on the basis of a pilot control (22, 24), so that a control of the metering unit (130) and thus a control of the rail pressure is carried out.

2. The method of claim 1, wherein the control value (58) for the metering unit (130) is first determined based on a control based on a signal of a rail pressure sensor (90), which monitors the pressure in the rail (80), and at a failure of the rail pressure sensor (90) a transition from a regulation of the metering unit (130) to a control of

Metering unit (130) takes place.

3. The method of claim 2, wherein in the transition from a control to a control of the metering unit (130), a ramp start value is initialized so that the control value (58) of the metering unit (130) makes no jump.

4. The method according to any one of claims 1 to 3, wherein an adaptive curve (30) in the determination of the control value (58) is taken into account.

5. The method of claim 2 and 4, wherein the adaptive trace (30) is learned during operation with rail pressure sensor (90).

6. The method according to any one of claims 1 to 5, wherein in idle (54) in the determination of the control value (58) an additional feedforward control (52) is taken into account.

7. The method of claim 6, wherein an idle controller outputs a signal that is taken into account for determining the control value (58).

8. The method according to any one of claims 1 to 7, wherein in the determination of the control value (58) a pump tolerance (40) is taken into account.

9. Arrangement for operating an internal combustion engine with accumulator injection, in which a high-pressure pump (132) for introducing fuel (146) into the rail (80) is provided, wherein a metering unit (130) is provided, which is used to control the high-pressure pump (132). based on a manipulated variable (58), wherein the arrangement is designed such that the manipulated variable (58) can be determined on the basis of a precontrol (22, 24).