WO2016087034A1

WO2016087034A1 - Method for open-loop and/or closed-loop control of a fuel injector and device

Info

Publication number: WO2016087034A1
Application number: PCT/EP2015/002395
Authority: WO
Inventors: Patrick Deubler; Bernd Eder
Original assignee: Daimler Ag
Priority date: 2014-12-04
Filing date: 2015-11-27
Publication date: 2016-06-09
Also published as: DE102014017987A1

Abstract

The invention relates to a method for open-loop and/or closed-loop control of an injection of fuel by means of at least one fuel injector of an internal combustion engine, wherein an electrical charge (Q) applied to the fuel injector configured as a piezo injector (1) is continuously recorded for the purposes of open-loop and/or closed-loop control, wherein an injected amount of fuel (K) is determined from the recorded electrical charge (Q), and an error is detected in the event of a predefined deviation of the determined fuel amount (K) from a target value. The invention also relates to a device for carrying out the method.

Description

Method for controlling and / or regulating a fuel injector and device

The invention relates to a method for controlling and / or regulating an injection of fuel by means of at least one fuel injector

Internal combustion engine. Furthermore, the invention relates to a device for carrying out the method.

From DE 10 2008 040 629 A1 a method for driving a

Fuel injector in case of overpressure or failure and an associated injection system for internal combustion engines known. The fuel injector has a controllable piezoelectric actuator for switching a high-pressure injection

Fuel controlling switching valve of the fuel injector. In the event of a fault or overpressure detected in the injection system, the piezoactuator is activated for a partial or full lift of the switching valve.

In addition, from DE 31 38 647 A1 a control device for solenoid valves is known. The control device is provided for pressure valves of hydraulic vehicle brake systems, which are actuated with power pulses of controllable pulse width and constant frequency and continuously adjustable. The pulse frequency is higher than the limit frequency of the solenoid valves, which results from their mass and rear part spring constant.

The invention has for its object to provide a comparison with the prior art improved method for controlling and / or regulating an injection of fuel by means of at least one fuel injector of an internal combustion engine and an improved apparatus for performing the method.

The object is achieved with respect to the method by the in claim 1 and in terms of the device by the features specified in claim 8.

CONFIRMATION COPY Advantageous embodiments of the invention are the subject of the dependent claims.

A method for controlling and / or regulating an injection of fuel by means of at least one fuel injector of an internal combustion engine sees

According to the invention, that for the control and / or regulation on the as

Piezo injector trained fuel injector applied quantity of electric charge is detected continuously, wherein from the detected electric charge an injected fuel quantity is determined and at a predetermined deviation of the determined fuel quantity from a target value, an error is detected.

By means of the method it is possible to make a mistake of the fuel injector

Determine internal combustion engine as part of a vehicle and output this error as this error message in the vehicle.

The method provides a comparatively simple, reliable and stable basis for a vehicle diagnostic system, with continuity of detection

relatively few error detections occur or False MIL is avoided.

By carrying out the continuous diagnosis, it is not necessary to fulfill a specification of an in-use monitoring performance ratio, since by means of the

Method is not a basic vehicle diagnostic function of a fuel system is shown, but a monitoring of a secondary sensor. This type of monitoring can be legally assigned to a comprehensive component allocation, which is subject to relatively less complex legal requirements.

In addition, the continuous detection of the electric charge in a

Cold start phase can be used for a multiple injection of the internal combustion engine, wherein it is also possible the method for several cylinders of

Apply internal combustion engine. This makes it possible for each individual cylinder to be monitored, so that cylinder-precise fault diagnosis can be carried out.

In a development of the method, a sum of injector strokes over a predetermined period of time is determined for the diagnosis of a multiple injection. In this case, partial injections, ie partial strokes, of the fuel injector as well as full injections, ie full strokes, are detected. In a resulting development, a total stroke of the fuel injector is determined on the basis of the sum of the injector strokes of a stroke. In this case, the total stroke represents a reference variable for determining an injection quantity of the fuel, wherein the total stroke can also be referred to as the total opening duration of the fuel injector. This total opening duration is a holding time of the electric charge applied to the fuel injector.

To determine an error in an embodiment of the method the

Total charge and the total opening duration compared with a respective predetermined setpoint. Exceeds or falls below the total charge and the

Total opening duration the specified setpoint, there is an error case.

In particular, the error of the control and / or regulation of the fuel injector is determined as a function of a deviation of the total charge and the total opening duration determined from the comparison from the respective desired value.

A further embodiment of the method provides that the error is stored in a control unit of the internal combustion engine, in particular an engine control unit. This makes it possible to have the error, for example, read by a workshop personnel, so that an injection quantity can be adjusted.

In one possible development, at least one of the fuel injector effluent electrical charge by means of a voltage drop by means of a

Measuring resistance determined by an end of the voltage drop, an end of the holding time and thus a total charging time can be determined.

Moreover, the invention relates to a device for carrying out the method described above, wherein it is possible by means of the device, an applied on the fuel injector designed as a piezoelectric injector electric charge

continuously detect.

In this case, the device comprises at least one fuel injector, a control unit for controlling the fuel injector and a measuring resistor.

Embodiments of the invention are explained in more detail below with reference to drawings. Showing:

Fig. 1 shows schematically a circuit diagram for driving a piezo injector a

Internal combustion engine,

2 schematically shows a first diagram with a charge curve,

Fig. 3 shows schematically a second diagram for determining a relative

Fuel quantity for a respective partial injection and

Fig. 4 shows schematically a third diagram for determining a fault of a

Control and / or control of the piezo injector.

Corresponding parts are provided in all figures with the same reference numerals.

FIG. 1 shows a circuit diagram for controlling a fuel injector, designed as a piezoinjector 1, of an internal combustion engine, not shown in more detail, of a vehicle.

The piezoelectric injector 1 is coupled to a so-called driver electronics 2, a microcontroller 3 and a measuring resistor 4, wherein the driver electronics 2 and the

Measuring resistor 4 are components of an application-specific integrated circuit S arranged in a motor control unit 5.

A current I flows through the piezo injector 1, the piezo injector 1 comprising multilayer piezoelectric elements as a piezo stack 1.1. By applying an electrical voltage to the piezoelectric elements, a mechanical movement is performed.

Stack arrangements of multi-layered piezoelectric elements are used as a piezoelectric actuator, wherein an advantage of such a piezoelectric actuator over a magnetic actuator is that a piezoelectric stack 1.1 inevitably always changes in proportion to the electrical charge absorbed in its length. The cause is the piezoelectric effect. By this piezoelectric effect are the deflection of the piezo injector and this

Physically coupled to each other, so there is a direct correlation between the two parameters. If one of the piezoelectric elements of the piezo stack 1.1 is defective, it absorbs none, too little or too much electrical charge Q. The inclusion of none, too little or too much electrical charge Q can lead to an incorrect supply of fuel, in particular into a cylinder of the internal combustion engine.

The current I, which flows through the piezoinjector 1, also flows through the

Measuring resistor 4. Since the electrical voltage of the product of electrical

Resistor and the current I corresponds, the measured electric voltage corresponds to the current I flowing through the piezoelectric injector 1. This electrical voltage is integrated in the application-specific integrated circuit S over a time to be measured t.

Based on the voltage curve of the piezoinjector 1 during an injection of fuel, the electrical charge Q and discharge is determined, so that it can be deduced whether the electrical charge Q is applied in the correct time to the piezoelectric injector 1 and is discharged in the correct time.

FIG. 2 shows a first diagram D1 of a profile of an electrical charge Q of the piezoinjector 1 during an injection process for combustion in a cylinder of the internal combustion engine. In particular, the course of the electrical charge Q is shown when driving the piezoelectric injector 1.

For this purpose, the time t is plotted on the ordinate of the current I and on the abscissa of the first diagram D1 as the driving time of the piezo injector 1.

Figure 3 shows a second diagram D2, wherein on the ordinate a relative

Fuel quantity K and on the abscissa the time t is removed.

It is in the second diagram D2 in a cylinder of the

Internal combustion engine for combustion injected fuel quantity K at a partial stroke Qi to Q ₃ and a full stroke Q _{4 of} the piezo injector 1 shown.

The injection of fuel can take place over several partial strokes up to Q ₃ and / or a full stroke Q ₄ .

In the case of a partial stroke Qi to Q ₃ , the piezoinjector 1 is activated in such a way that an injector needle is not fully opened. In a full stroke Q ₄ , the electrical Control, however, so that the Injektornadel is completely open for a predetermined time t for injection.

In this case, a relative amount of fuel K is determined based on the electrical charge Q of the piezo injector 1 at the partial strokes to Q ₃ and based on the electric charge Q of the piezo injector 1 at the full stroke Q ₄ and the corresponding hold time over which the electric charge Q is maintained ,

An electrical charge Q, a discharge current, flowing from the piezoinjector 1 is determined on the basis of a voltage drop across a resistor determined by means of the measuring resistor 4.

By means of the electric charge Q and the holding time is an injected

Fuel quantity K largely determined exactly, so that a target-actual comparison is possible.

From the partial strokes to Q ₃ and the full stroke Q _{4 of} a stroke of the cylinder, as shown in a third diagram D3 in Figure 4 is shown in more detail, a total stroke Q _{ges determined} with a corresponding amount of fuel K.

The relative fuel quantity K is determined from a total electric charge Q _ges and a total opening duration t _{ges of} the injector needle. The relative fuel quantity K is thus determined from the sum of the individual determined relative fuel quantities K.

In order to determine whether there is an error with regard to operation of the piezoinjector 1, the determined total electric charge Q _ges and the total opening duration t _{ges of} the injector needle are compared with a respective desired value.

Is determined based on the comparison performed that the electrical

Total charge Q _ges and / or the total opening duration t _ges deviate from their respective setpoint value by more than a predetermined tolerance range T shown by the dashed lines, a vehicle diagnosis error is determined and stored. This error is preferably displayed in a display area of an instrument panel of the vehicle and can be read by a workshop staff for troubleshooting. By means of the method, an applied quantity of electrical charge Q is determined, wherein the determination takes place both in the cold start and in the warm homogeneous operation and in the stratified operation of the internal combustion engine.

Since the determination of the total stroke Q _{ges is} also possible for injections with more than one partial stroke up to Q ₃ , the monitoring of the electrical charge Q can also be carried out in the cold start region, wherein in the cold start region usually

Multiple injections are provided to heat a coupled to the internal combustion engine catalyst to an operating temperature.

LIST OF REFERENCE NUMBERS

1 piezo injector

1.1 Piezo stack

2 driver electronics

3 microcontroller

4 measuring resistor

5 engine control unit

D1 first diagram

D2 second diagram

D3 third diagram

I electricity

K fuel quantity

Q electric charge

Qi to Q ₃ partial lift

Q ₄ full stroke

Qge _S total charge

S circuit

T tolerance range t time

t tot _total opening duration

Claims

claims

1. A method for controlling and / or regulating an injection of fuel

by means of at least one fuel injector of an internal combustion engine, characterized in that

for controlling and / or regulating, an electrical charge (Q) applied to the fuel injector formed as a piezo injector (1) is detected continuously, an injected one of the detected electrical charge (Q)

Fuel quantity (K) is determined and at a predetermined deviation of the determined fuel quantity (K) from a target value, an error is detected.

2. The method according to claim 1,

characterized in that

for the diagnosis of a multiple injection a sum of

Injector strokes (Q ^ to Q ₄ ) is determined over a predetermined period.

3. The method according to claim 1 or 2,

characterized in that

Based on the sum of injector strokes (Qi to Q ₄ ) of a stroke, a total stroke (Q _ges ) of the fuel injector is determined.

4. The method according to any one of the preceding claims,

characterized in that

a total charge and a total opening duration of the fuel injector is compared with a respective predetermined target value.

5. The method according to claim 4,

characterized in that

as a function of a deviation of the total charge determined from the comparison and the total opening duration (t _ges ) from the respective desired value, the error of the control and / or regulation of the fuel injector is determined.

6. The method according to claim 1,

characterized in that

the fault is stored in a control unit of the internal combustion engine, in particular an engine control unit (5).

7. The method according to any one of the preceding claims,

characterized in that

at least one of the fuel injector effluent electrical charge (Q) is determined based on a voltage drop by means of a measuring resistor (4).

8. Device, designed to carry out a method according to one of

previous claims.

9. Apparatus according to claim 8,

characterized by at least one fuel injector, a control unit for controlling the fuel injector and a measuring resistor (4).