WO2016071106A1

WO2016071106A1 - Method for controlling injectors in an internal combustion engine

Info

Publication number: WO2016071106A1
Application number: PCT/EP2015/074306
Authority: WO
Inventors: Fabian FISCHER; Stefan Stein
Original assignee: Robert Bosch Gmbh
Priority date: 2014-11-05
Filing date: 2015-10-21
Publication date: 2016-05-12
Also published as: DE102014222543A1

Abstract

The invention relates to a method for controlling injectors in an internal combustion engine, which allows an adaptation of the control duration AD of the injector by comparing the set starting time of the opening of the nozzle of the injector with a measured time of the opening of the switching valve, the control duration AD of the injector being modified as a function of this comparison.

Description

description

title

Method for controlling injectors in an internal combustion engine Prior art

The invention relates to a method for controlling injectors in an internal combustion engine, in which for the metering of fuel in a

Combustion chamber of the internal combustion engine, the injector is controlled by means of a control signal with a fixed start time and a specified drive time and thus at least one switching valve is opened and closed, via which a control of a nozzle of the injector for metering the fuel.

A large number of modern diesel engines are equipped with so-called common-rail systems, which represent a cost-effective, fuel-efficient and emission-reducing variant of a fuel injection system.

Common rail systems are electronically controllable in their injection quantity and duration independently of the crank angle of an internal combustion engine and also enable pre, main and postinjections of the fuel.

In these systems, for example, known solenoid injectors are used to inject the fuel into the combustion chamber of the internal combustion engine. These injectors have u. a. a switching valve and a nozzle needle on.

To realize an injection of a metered amount of fuel into the combustion chamber, the switching valve (actuator) is supplied with a voltage and / or a current for a defined period of time. The current generates a magnetic field which causes the switching valve to move in a stroke. The pressure relief in the control chamber of the switching valve in combination with the hydraulic design in turn lead to a lifting movement of the nozzle needle. When the switching valve closes, the nozzle needle is offset by the increasing pressure in the control chamber in a closing movement.

To control the solenoid valve injectors, a central control unit is provided, which is also referred to as a motor controller. The

Engine control generates the time-defined control signals for all injectors of all cylinders of an internal combustion engine.

As an alternative to this magnetically operating actuator, it is also possible to use an actuator which operates according to the piezoelectric effect and which sets the switching valve in a stroke movement. Also in this case, the injector is opened and closed by the controlled movement of the nozzle needle.

Usually, the switching valve and the nozzle needle are coupled together by means of a hydraulic system not described here.

Also known are methods for determining correction functions for pressure wave-dependent actuation of solenoid valve injectors, in which needle-closing sensors are used in the discharge nozzle.

Also known are methods for dynamically correcting the actuation duration in the case of injection already in progress or started energization of the actuator of an injector.

Common rail injectors (CRI) with servo principle have a pressure-dependent injection start delay. In the case of multiple injections, the respective preceding injections, which cause pressure waves, influence the pressure for the subsequent injection.

As a result, depending on the distance of the injections, the start of injection takes place too early or too late (so-called quantity wave). The resulting

Quantity error can be corrected with a software (SW) function (QWC: Quantity Wave Correction). This function is measured individually for each injection system, ie for each application, and in the control unit by means of a corresponding record stored. This stored data record is used to correct the quantity error.

In this method, pattern-specific deviations (Ex-Ex scattering) of the injection systems can not be taken into account. Thus, quantity errors caused by pattern-specific deviations can not be completely corrected, which can lead to an increase in the quantity error.

Disclosure of the Invention Advantages of the Invention

The device according to the invention with the features of the independent claim 1 has the advantage that a dynamic adjustment of the drive time AD of an injector due to a check of a timing between an actual time of opening a switching valve and the predetermined by the control signal target time for opening the switching valve ,

For this purpose, for example, by means of a known

Needle closing sensor (NCS) during a current injection event, a time of opening of the switching valve with the name

This measured valve opening time is compared with a specified starting time for the opening of the switching valve, ie a setpoint, with the designation "t_open_MV_soll".

If it is determined in this comparison that both valve opening times coincide, the control duration AD of the injector is not changed. In this case, quantity errors in the injection are measured by those measured for the respective injection system and stored in the engine control

Correction data optimally minimized.

However, it is found in this comparison that the measured

Valve opening timing deviates from the setpoint, a correction of Actuator AD and / or the start of the drive of the injector, for example, made for the subsequent injection process to reduce the quantity error occurring in this case. Alternatively, an adaptation of the control period AD can already be carried out in the current injection process.

A correction of the start of control represents a shift of the starting edge of the control signal driving the injector, for example, with respect to the specified starting time.

This correction is based on the knowledge that the beginning of the injection, i. H. Opening the nozzle, with short spray intervals between each

Injections (hydraulic distance between 50 and 300 is) very well correlated with the opening of the switching valve and so can be concluded from the timing of the switching valve to the injector nozzle / needle.

It is particularly advantageous to calculate a difference between the values of the measured

To form timing of the opening of the switching valve and the set start timing for the opening of the switching valve and to make the correction of the driving time AD and / or the start of the drive in dependence on the difference.

For this purpose, the times are each in one to the other

Processing appropriate value, such as a digital value transferred. From these values a difference can then be generated by means of an arithmetic logic unit.

It is also advantageous, with a difference greater than zero, to increase the activation duration AD or, in the case of a difference smaller than zero, to reduce the activation duration AD.

In the event that the value of the measured valve opening time is greater than the value of the predetermined valve opening time, the result is a difference which is greater than zero. In this case, the driving time AD of the subsequent injection is increased. For the opposite case, that the value of the predetermined valve opening time is greater, this results in a Difference which is less than zero. For this case, the drive duration AD of the subsequent injection is reduced.

According to an advantageous embodiment of the method is provided to weight the difference formed with factors.

For example, a drive duration AD_soll_neu after the

education provision

AD_soll_neu = AD_soll + factorl * (t_open_MV_measured - t_open_MV_soll) ^A factor2 are formed.

With the added factors 1 and 2, an improved adaptation of the method can be achieved.

In this way, the predetermined setpoint for the Bestromungsende of the injector is dynamically adjusted during operation of the internal combustion engine.

Conveniently, by means of a specially designed for this purpose

Computer program containing a program code executable on a data processing device, the steps of the method for

Control of injectors are performed in an internal combustion engine.

It is also advantageous to store the computer program on a machine-readable storage medium.

The method for controlling injectors in an internal combustion engine may include, for example as a data processing device, a processor for processing the program code. To save the

Program codes, the device is equipped with a non-volatile storage means, such as a ROM (Read Only Memory), EPROM (Electrically Programmable Read Only Memory), EEPROM (Electrically Erasable PROMs) or flash EEPROM. This storage means is for transmitting data, such as a program code, connected to the processor and arranged for example in a motor control.

Advantageously, an electronic control unit, for example a

Engine control provided, which can implement the steps of the process.

Brief description of the drawings

An embodiment of the invention is illustrated in the drawing and explained in more detail in the following description.

The figure shows a representation of injection start shifts

different times.

Embodiments of the invention

With the aid of a sensor (NCS) for diesel injectors, the switching of the actuator (MV) itself can also be monitored, since the valve chamber pressure varies depending on the state of the switching valve, which can be open or closed.

At very short intervals between the injections (tdiff), for example less than about 300 is, electrically and hydraulically, the start of injection is also heavily dependent on the timing of the switching of the solenoid valve. Open that

Solenoid valve earlier, also opens the nozzle needle earlier and vice versa.

The time of the injection start, ie the opening of the nozzle, can not be measured directly. Since the timing of the valve opening, so switching of the solenoid valve, correlates well with the opening of the nozzle needle at short injection intervals, as shown schematically in the figure, using the timing of the valve opening, the control period AD of the current and / or the subsequent injection in Corrected a precontrol so that not too much or too little amount of fuel is injected.

In the figure, the injection start shift is in a diagram for

different times tdiff shown. In the vertical trisection of the diagram, the drive current of the injector is shown in amps at different drive times in the upper illustration. The middle diagram shows the injection rate in the unit millivolts, while in the lower illustration, the signal of an arranged in the solenoid valve injector associated needle closing sensor, which monitors the valve opening of the solenoid valve is shown in volts. All three representations run over a common time axis, which is labeled with the unit milliseconds. The signal shown in the diagram in the lower diagram of the needle closing sensor (NCS signal) is for the inventive

Process used.

The drive duration AD of the injector is predetermined by means of a switching signal generated by a motor control. In a deviation of the predetermined valve opening time from the actually realized time of opening the nozzle of the injector, there is no longer the predetermined

Driving time AD responsive time of injection of fuel into the combustion chamber of the internal combustion engine.

This deviation unintentionally alters the amount of metered

Fuel. By means of a dynamic adaptation of the injection duration already for the subsequent injection, the method according to the invention enables a timely correction of occurring deviations from the desired specification.

For adapting the activation period AD, for example, the following education regulation can be used:

AD_soll_neu = AD_soll + (t_open_MV_ measured - t_open_MV_soll)

According to this provision, the drive time AD remains in the case of

Coincidence of the times "t_Open_MV_Measured" and

"T open MV should" unchanged. In a delayed or premature opening of the solenoid valve of the injector, the driving time AD for the injection is adjusted immediately by the driving time AD is increased or decreased.

Such an adaptation of the activation duration AD can be carried out both for the current injection and for the subsequent injection.

In an alternative training regulation factors are added to the weighting, as usually the activation time does not correspond 1: 1 to the injection duration of the injector. Such an extended education requirement reads

for example:

AD_soll_neu = AD_soll + factorl * (t_open_MV_ measured - t_open_MV_soll) ^A factor2

Another application of the method is the correction of different valve opening times, for example as a result of

Return Backpressure Fluctuations, to Reduce Hub-Hub Scattering.

The Ansteuerdauer an injection is based on the operating variables of the injection system, for. B. rail pressure, and calculates the amount of fuel to be injected. Usually, the drive time is before the beginning of the

Injection firmly and can not be changed. In future injection systems, the length of the control period of the already started injection can be adapted.

If it comes to stochastic fluctuations in the valve opening, the z. B. may be due to hydraulic effects

(Return backpressure fluctuations), the injection start of the injector will be subject to these stochastic fluctuations (shot-shot

Volume scattering). If it is detected during the current injection that the switching valve opens earlier / later than specified by the setpoint, these deviations can still be corrected in the current injection. Thus, shot-weft scattering of the injection quantity can be reduced, provided that they are caused by fluctuations in the opening of the valve.

Claims

claims

1. A method for controlling injectors in an internal combustion engine, wherein for the metering of fuel in a combustion chamber of the internal combustion engine, the injector is controlled by means of a control signal with a fixed start time and a fixed drive time (AD), wherein at least one switching valve is opened and closed, via which a control of a nozzle of the injector for metering of the fuel takes place, characterized in that a time of opening of the switching valve of the injector is measured and compared with a fixed starting time and that in a deviation of the two times from each other, the driving time (AD) of the injector is changed.

2. The method according to claim 1, characterized in that the change of the driving time (AD) is carried out during a current metering of fuel.

A method according to claim 1 or 2, characterized in that a difference is formed from values representing the two times, the value representing the fixed starting time being subtracted from the value for the measured time of opening.

4. The method according to claim 3, characterized in that in the event that the difference is less than zero, the driving time (AD) is reduced and that in the event that the difference is greater than zero, the

Activation time (AD) is increased.

5. Computer program which is set up every step of the

Method according to one of claims 1 to 4 perform.

6. Machine-readable storage medium on which a

Computer program according to claim 5 is stored.

7. Electronic control device which is arranged to perform each step of the method according to one of claims 1 to 4.