CN107816393B

CN107816393B - Method for controlling multipoint injection in an injection system

Info

Publication number: CN107816393B
Application number: CN201710811359.0A
Authority: CN
Inventors: E.托纳; E.沙伊德; T.延森
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-09-12
Filing date: 2017-09-11
Publication date: 2022-03-01
Anticipated expiration: 2037-09-11
Also published as: DE102016217306A1; CN107816393A

Abstract

The invention relates to a method for controlling a multi-point injection in an injection system, wherein at least two successive partial injections are injected by means of at least one injector having a nozzle needle, wherein a signal is detected which characterizes the closing time of the nozzle needle, and wherein a continuous delivery of fuel between the two partial injections is detected if no closing time is detected within a predefined time window.

Description

Method for controlling multipoint injection in an injection system

Technical Field

The invention relates to a method for controlling a multipoint injection of an injection system.

Background

In so-called common rail injection systems for injecting fuel into an internal combustion engine, it is known to vary the time intervals between the individual partial injections or the duration of the individual partial injections in order to influence the combustion process taking place in the combustion chamber of the internal combustion engine. The injection is carried out by an injector operated by means of a nozzle needle.

If the time interval between the individual partial injections becomes too short, a so-called coherent delivery of fuel may occur. This means that at least two individual partial injections merge into one another and that these partial injections act as a single longer partial injection. This results in a significant increase in the injection quantity and a deterioration of the combustion process.

Disclosure of Invention

In contrast, the method according to the invention has the following advantages: a coherent delivery of fuel between two partial injections can already be identified. This can reliably prevent the increase in the fuel amount due to the continuous delivery.

This is achieved according to the invention in the following way: in a method for controlling a multipoint injection, in which at least two successive partial injections are carried out by means of at least one injector having a nozzle needle, the coherent feed (Durchf sparing) is identified if no closing time is identified within a predefined time window.

In this way, a consistent transport can be reliably detected and appropriate countermeasures can be introduced. For example, the interval of the partial injection can be increased at the next injection.

It is particularly advantageous if a signal which characterizes the closing time of the nozzle needle is detected and a coherent delivery of fuel between two partial injections is detected starting from the time derivative of the signal which characterizes the closing time of the nozzle needle.

It is also advantageous if the closing time of the nozzle needle is detected from a local maximum of the derivative of the signal which characterizes the closing time.

In a particularly advantageous embodiment, it is provided that the time window corresponds to a time range within which the closing time is expected.

In a further aspect, the invention relates to a novel program code for producing a computer program that can be run on a controller, in particular a source code with compilation instructions and/or linking instructions, together with processing instructions, wherein the program code generates a computer program for carrying out all the steps of one of the described methods if the program code is converted, i.e. in particular compiled, and/or linked into a computer program that can be run in accordance with the processing instructions. Such a program code can be generated, inter alia, by source code, which can be downloaded, for example, from a server in the internet.

Drawings

Embodiments of the invention are illustrated in the drawings and are explained in detail in the following description. In the drawings:

FIG. 1 shows a block diagram of the major elements of a control mechanism for fuel injection;

FIG. 2 shows different signals plotted with respect to time; and is

Fig. 3 shows a flow chart of the process according to the invention.

Detailed Description

The different elements of the injection system are shown in fig. 1. The injector is denoted by 100. This injector comprises on the one hand an actuator 105 and on the other hand a sensor 108. The actuator 105 is actuated by an actuating mechanism 110. This actuating mechanism 110 comprises, in particular, a regulator 115. The sensor evaluation unit 120 evaluates the signals of the sensor 108. The sensor evaluation device 120 transmits the evaluated signal to the controller 115 and on the other hand to the coherent feed detection device 130. The consecutive feed detection means 130 in turn apply a signal to the injection control means 140 indicating the consecutive feed performed. The injection control device 140 in turn loads the actuation device 110.

The injection control unit 140 presets the start of injection and the injection duration depending on various operating parameters, such as rotational speed, load and, if necessary, further parameters. The control unit 140 converts these predefined specifications for the start of injection and the injection duration into a control signal for the actuator 105 of the injector 100. The metering of fuel into the combustion chamber by the injector 100 is started and ended at a predefined point in time or at a predefined angular position of the crankshaft.

In order to improve the accuracy of such control mechanisms, systems equipped with sensors 108 are known. This sensor 108 provides a sensor signal which characterizes the closing time of the nozzle needle of the injector. Such sensors are commonly referred to as NCC sensors. In one embodiment of such a sensor 108, it is provided that the sensor is designed as a pressure sensor which is arranged in the injector and detects the pressure in the injector. Starting from the pressure curve, the sensor evaluation unit 120 then determines the closing time of the injector or other characteristic variables of the injector from the sensor signal. These signals are then transmitted to the controller 115 about characteristic features of the injector, for example the closing times, which accordingly corrects the actuation of the actuator 105 as a function of the desired closing time and the actually measured closing time.

With modern fuel metering systems, increasingly shorter intervals are required between the partial injections. Because of the very significant deviations of the individual systems, the following may occur: for small intervals of the partial injection, this results in a continuous feed in the individual injection systems and not in the other systems. The task of identifying a coherent feed between two partial injections is therefore addressed. This is carried out according to the invention in the following way: the output signal of the sensor evaluation device 120 corresponding to the processed sensor signal of the sensor 108 is transmitted to the continuous conveyance detection device 130. This consecutive delivery detection means 130 accordingly processes the signal of the sensor 108 and supplies a signal to the injection control means 140 which indicates the consecutive delivery performed. The injection control device then changes the first partial injection or the second partial injection in such a way that the distance is increased and the coherent feed is thereby prevented. For example, it can be provided that the desired actuation of the second partial injection is started to be pushed backward and/or the actuation of the first partial injection is started to be pushed forward.

In fig. 2a, a control signal in the form of a rectangular signal for the actuator 108 of the injector and the corresponding lift of the nozzle needle are plotted over time. In fig. 2b, the associated signal S of the sensor 108 is plotted. The differential signal AS of the sensor 108 is depicted in fig. 2 c. Fig. 2a to 2c show ratios for which the distance between the two partial injections E1 and E2 is selected to be so large that a coherent feed is reliably prevented. As the needle lift begins, the signal S of the sensor 108 falls and reaches its minimum value approximately in the middle of the injection. As closure begins, the signal S again rises and reaches its maximum slope as the valve needle closes. After the signal has been left at the higher level for a certain time, it drops back to its original value. At the time the needle is closed, i.e. at the end of the injection, the derivative AS of the signal of the sensor 108 has a local maximum. The profile of the signal is then repeated during a second partial injection E2. The signal profiles for the two partial injections are clearly separated. Wherein the maximum value of needle closure showing the second partial jet is less strongly shown.

The signals are shown only roughly schematically and greatly simplified and idealized.

In sub-diagram 2d, the separation between the partial injections E1 and E2 is significantly reduced. This leads to the following results: the signal of the sensor 108 no longer reaches its high level. The signal of the sensor 108 no longer rises due to the disappearance of the needle closure. This causes the local maximum of the first derivative AS of the output signal of the sensor 108 to disappear. Only the maximum value of needle closure showing the second partial jet can be seen.

According to the invention, it is provided that the consecutive feed is detected if a needle closure is not detected. Needle closure is detected if a local maximum of the display of the derivative AS of the signal of the sensor 108 occurs within a specific time window. If this is not the case, the consecutive conveyance is decided. This may for example occur if the value of the maximum is smaller than a threshold value. The time window corresponds here to a time range within which the closing time is expected. The time window preferably begins at a specific time duration after the end of the maneuver E1 for the first partial injection. Alternatively, the time window can also be started at a specific time duration after the start of the actuation E1 for the first partial injection. Ending the time window after expiration of a specified duration after the time window begins or after the maneuver E1 for the first partial injection begins or ends.

Alternatively, it can also be provided that the disappearance of the needle closure is detected by another method. For example, it can be provided that the disappearance of the needle closure is detected by a model search (Mustersuche) or by the use of a neural network to detect the disappearance of the needle closure and thus to detect a continuous delivery.

A corresponding embodiment for detecting a continuous feed is illustrated in fig. 3 by means of a flow chart. In a first step 300, a sensor signal S of the sensor 108 is evaluated and the signal S is differentiated and a derivative AS of the signal S is calculated therefrom. The timer T is set to zero in step 310. This is done at the beginning of the time window. Subsequently, in step 320, the timer T is increased by a certain value DT. In step 330, the maximum MAX reached by the derivative AS of the signal S in the time window is saved. The following query 340 checks whether the timer T is still less than the end TE of the time window. If this is the case, step 320 is repeated. If this is not the case, i.e. the end of the time window is reached, the query 350 checks whether the maximum MAX exceeds a threshold. If this is the case, it is identified in step 360 that no coherent transport is performed. If the query 350 identifies that the maximum value MAX is less than the threshold value, then a determination is made in step 370 for a coherent delivery.

Claims

1. Method for controlling a multipoint injection in an injection system, wherein at least two successive partial injections are carried out by means of at least one injector having a nozzle needle, characterized in that, if no closing time is detected within a predefined time window, a consecutive delivery is detected, a signal which characterizes the closing time of the nozzle needle is detected, the consecutive delivery of fuel between the two partial injections is detected starting from a time derivative of the signal which characterizes the closing time of the nozzle needle, and the closing time is detected on the basis of a local maximum of the derivative of the signal which characterizes the closing time of the nozzle needle.

2. The method of claim 1, wherein if the local maximum exceeds a threshold, no consecutive delivery occurs.

3. The method of claim 1, wherein the continuous transport is performed if the local maximum is less than a threshold.

4. The method according to claim 1, characterized in that the time window corresponds to a time range within which the closing time is expected.

5. The method according to any one of claims 1 to 4, characterized in that the spacing between the two partial jets is enlarged when a coherent feed is detected.

6. A machine-readable storage medium having stored thereon a computer program configured to: all the steps of one of the methods according to any one of claims 1 to 5 are performed.

7. A controller configured to: all the steps of one of the methods according to any one of claims 1 to 5 are performed.