WO2016156007A1

WO2016156007A1 - Method and device for controlling the temperature of an injection valve

Info

Publication number: WO2016156007A1
Application number: PCT/EP2016/055204
Authority: WO
Inventors: Tany GARGISO; Robert Hoffmann; Anselm Schwarte
Original assignee: Continental Automotive Gmbh
Priority date: 2015-04-01
Filing date: 2016-03-10
Publication date: 2016-10-06
Also published as: DE102015205942A1; CN107429622B; KR101972688B1; CN107429622A; DE102015205942B4; KR20170122239A

Abstract

The invention relates to a method for monitoring the operation of the fuel injection system of an internal combustion engine, comprising the following steps: determining a criticality index for the thermal load of an injector of the fuel injection system; checking whether the determined criticality index is greater than a threshold value; checking whether the determined criticality index is greater than the threshold value for a specified duration if the determined criticality index is greater than the threshold value; and introducing a measure for reducing the thermal load of the injector if the determined criticality index is greater than the threshold value for the specified duration.

Description

description

METHOD AND DEVICE FOR CONTROLLING THE TEMPERATURE OF AN INJECTION VALVE

The invention relates to a method and a device for monitoring the operation of the fuel injection system of an internal combustion engine. Internal combustion engines having a fuel injection system have been known for a long time. Such an internal combustion engine is described for example in DE 10 2013 206 600 AI. There, an injection system and a control method for an injection system with at least one injection valve for injecting fuel into an internal combustion ^¬ engine described, wherein in recurrent injection cycles, a closure element of the injection valve is moved so that it is in an actual opening time OPP2 on an upper Stop hits and / or in one

Actual closing time OPP4 impinges in a closed position and thereby triggers a characteristic signal of a sensor element of the injection valve, wherein a temporal signal waveform of the sensor element is detected and in a temporal

If the characteristic signal is not detected in said portion of the temporal waveform, a search process is performed in subsequent injection cycles. By this procedure, the measurement of the opening and closing times of the injectors and thus the reliability and the robustness of the control method of the injection system is improved.

With regard to the control of the operation of such internal combustion engines, in particular the fuel quantity control using piezoelectrically driven Inj ectors, there are ambiguous symptoms, which may need to be responded to situa ^¬ tion dependent. The control unit of these internal combustion engines übli ^¬ cherweise contains a plurality of control mechanisms and control loops that can increase or decrease the metered amount of fuel as needed. A single high manipulated variable is usually uncritical, especially at low dynamic motor operation.

However, should the manipulated variables a plurality of parameters to be high and at the same time present a highly dynamic operation of the internal combustion ^¬ machine, for example, a sharp acceleration, then care must be taken that the injectors of the fuel injection of the internal combustion engine can be maintained in a stable operating range, to avoid that a possibly critical driving situation arises.

The object of the invention is to provide a method and an apparatus for monitoring the operation of the fuel injection system of an internal combustion engine, wherein the application of the injectors of the fuel injection can be maintained in a stable operating range mög ^¬ lichst long.

This object is achieved by a method having the features specified in claim 1 or by a device having the features specified in claim 13. Advantageous embodiments and further developments of the invention are specified in the dependent claims.

The advantages of the invention are, in particular, that by means of the claimed method a safety function can be implemented by which it is ensured that the injectors of the fuel injection system are kept in a stable operating range as long as possible. This reduces the likelihood of kri ^¬-Nazi driving situations as they may arise during overtaking ^¬ processes, for example, is reduced. This is achieved essentially by the fact that in the presence of increased values in parameters which are important for the operation of the fuel injection system, before initiating suitable countermeasures, first by calculating a critical value. From this parameter and its evaluation, it is possible to check within which reaction time and with what strength countermeasures have to be initiated. This procedure corresponds to a variable in terms of the step size and the maximum debouncing of a fault, depending on the current system state, which by the force ^¬ injection system influencing parameters will be described.

Further advantageous features of the invention will become apparent from the following exemplary explanation with reference to FIGS. It shows

Figure 1 is a block diagram for explaining the structure of a

Fuel injection system of an internal combustion engine,

FIG. 2 is a flowchart for explaining an exemplary embodiment of a method according to the invention and FIG

Figure 3 is a block diagram for explaining a control unit of the fuel injection system of the internal combustion ^¬ engine.

1 shows a block diagram for explaining the structure of the fuel injection system 100 of an internal combustion ^¬ machine. This fuel injection system 100 has a fuel tank 200, from which fuel is taken from a fuel pump 300 via a fuel line 210. In the fuel line 210, a dashed line drawn fuel filter 220 may be arranged. The fuel extracted from the fuel tank 200 by the fuel pump 300 is supplied to an intake valve 400 via a fuel line 310. This intake valve 400 regulates the flow of fuel through a fuel line 410 to a high pressure pump 500. The intake valve 400 may be an integral part of the high pressure pump 500. The compressed in the high ^¬ pressure pump 500 to a high pressure fuel is via a high-pressure fuel line 510 to a rail 600th passed. From there it passes via high-pressure lines 610 to injectors 700, via which the compressed to a high pressure fuel is injected into the combustion chambers of a combustion engine 800 ^¬ . The rail 600 is connected to a digital pressure reduction valve 630, which may be also be an integral part of the Be ^¬ stand rails. The digital pressure reduction valve 630 is connected via a fuel return line 620 to the motor ^¬ fuel tank 200 to return 600 from the rail excess fuel through the pressure reduction valve 630 in the fuel tank 200th Alternatively, the over the

Returned fuel 620 also be returned to the fuel filter 220, as indicated in the figure 1 by the dashed lines. For detecting the fuel pressure present in the rail 600, a pressure sensor 640 is provided.

Furthermore, the injection system 100 to fuel ^¬ a control unit 900 shown in FIG 1, which is designed for controlling the injection processes. The control unit 900 is connected via control lines 910 to the inlet valve 400, which

High-pressure pump 500, the injectors 700 and the pressure reduction valve 630 connected. The control unit 900 controls the injection ^{¬ processes} in dependence on the current operating state of the internal combustion engine, which it determines using sensor signals, stored tables and a stored work program. The sensor signals include, inter alia, a sensor signal s1 output by the pressure sensor 640, a sensor signal s2 output by a speed sensor 810, and a sensor signal s3 output by a temperature sensor 820.

The control unit 900 determines, using the at ^¬ her out sensor signals to the stored tables and the stored work program, inter alia the currently induced power of the internal combustion engine, the instantaneous fuel temperature, the current energy requirement of the

Internal combustion engine and the instantaneous injection duration of In ^¬ jektoren. In doing so, it determines the instantaneous energy requirement by evaluating the time OPP2, which is the Opening time of the injection valve is, which is described by the current manipulated variable of the OPP2 controller. If this time occurs comparatively early within an injection ^cycle , then there is currently a comparatively low energy requirement. However, if this time occurs relatively late within an injection cycle, then there is currently a comparatively high energy requirement. Furthermore, it determines the instantaneous injection duration using a stored injection duration map and an evaluation of the times OPP2 and OPP4, where OPP4 is the closing time of the injection valve, which is described by the manipulated variable of the OPP4 controller.

FIG. 2 shows a flow chart for explaining an exemplary embodiment of a method according to the invention.

In this method, in a step S1, a determination of a criticality index I for the thermal load of an injector of the fuel injection system takes place. This thermal load of the injector is, for example high, when a large temperature gradient jektors is present between the head point and the base of the housing of the In ^¬. There is a need to monitor the thermal load of the injector and to check whether the injector can be kept in a stable operating range under the current thermal load, or whether measures to reduce the thermal load on the injector must be initiated.

For this purpose, in the embodiment shown in FIG. 2, after step S1, in a step S2, a query is made as to whether the criticality index I determined in step S1 is greater than a predefined first threshold value SW1.

If this check reveals that the determined criticality index I is greater than the predetermined first threshold value SW1, then a query is made in a step S3 as to whether the determined criticality index I already exists for a predetermined first one Time tl is greater than the predetermined first threshold SWl.

If this query yields the fact that the determined criticality index I is already greater than the predefined first threshold value SW1 for the predefined first time duration t1, then a measure for reducing the thermal load of the injector is initiated in a step S4. This measure belongs to a first reaction level RE1. The measures of the first reaction level RE1 preferably include a reduction in the number of active injections within one injection cycle. By reducing the number of active injections within an injection cycle of the injector, it is advantageously achieved that the reduction of the thermal load of the injector is imperceptible or inconspicuous for the user.

If an internal combustion engine with an automatic transmission is present, then in step S4, instead of or in addition to a reduction in the number of active injections, an automatic changeover to a higher gear can be undertaken. Also, such automatic switching to a higher gear is one of the measures of the first reaction level, does not limit the usability of the internal combustion engine and leads to a reduction of the thermal load of the injector.

If the query in step S2 is that determined in step Sl criticality index I is less than the prior ^¬ given first threshold SWl, then in a step S5, an inquiry is made as to whether the determined criticality index I is greater than a predetermined second threshold value SW2 , which is smaller than the predetermined first threshold value SWl.

If this query yields that the determined criticality index I is greater than the predetermined second threshold value SW2, then a query is made in a step S6 as to whether the determined criticality index I already exists for a predetermined second one Time t2 is greater than the predetermined second threshold SW2.

If this query yields the fact that the determined criticality index I is already greater than the predefined second threshold value SW2 for the predefined second time period t2, then a measure for reducing the thermal load of the injector is initiated in a step S7. This measure belongs to a second reaction level RE2. The measures of the second reaction level RE2 include, for example, a limitation of the rotational speed and / or the torque of the internal combustion engine. Also by such a restriction of the speed and / or the torque of the internal combustion engine is achieved in an advantageous manner that the thermal load of the injector is reduced.

The measures of the first reaction level RE1 differ from the measures of the second reaction level RE2, in particular in that the measures of the first reaction level RE1 do not restrict the current performance of the internal combustion engine or at most slightly and are as inconspicuous as possible for the user, while the measures of the second reaction level RE2 the instantaneous performance of the

Can noticeably limit internal combustion engine and also be noticeable to the user.

Preferably, the predetermined first time t 1 is smaller than the predetermined second time t 2. Therefore, the measures of the first reaction level RE1, which are initiated when the determined criticality index I is greater than the first threshold SW1 greater than the predetermined second threshold SW2, are initiated relatively quickly, whereas the measures of the second reaction level RE2, which are initiated when the determined criticality index I is greater than the second threshold value SW2 but smaller than the first threshold value SW1, can not be initiated until a comparatively longer period of time has elapsed. The said threshold values SW1 and SW2 and the stated time periods t1 and t2 were empirically determined in advance by the vehicle manufacturer and stored in a memory of the control unit of the internal combustion engine.

The above-described measures for reducing the thermal load of the injector have already been assigned in advance to the two reaction levels by the vehicle manufacturer, wherein this assignment is also stored in a memory of the control unit of the internal combustion engine and can be retrieved from the control unit from there, if necessary.

If the query in step S5 shows that the determined criticality index I is smaller than the predetermined second one

Threshold SW2, then proceed to step S8.

In this step S8, a query as to whether the determined criticality index I is already smaller than the predefined threshold value SW2 for a predetermined third time duration t3, which is preferably greater than the first time duration and also greater than the second time duration, is then detected. that the determined criticality index I lies in its normal range. In this case, it goes to a step S9. In this step S9, the measures introduced in step S4 or S5 for reducing the thermal load on the injector are canceled again (STOP). On the other hand, if the query in step S8 indicates that the determined criticality index is not yet smaller than the predetermined threshold value SW2 for the predetermined third time duration t3, then the measures for reducing the thermal load of the injector initiated in step S4 or S5 are maintained (CONTINUE ).

3 shows a block diagram for explaining a control unit S of the fuel injection system of the internal combustion engine, which is designed to determine the criticality index I and to determine activation signals stl and st2 for initiating measures for reducing the thermal load of an injector. In this control unit S it is preferably at the position shown in the Figure 1 control unit 900 which is provided to control the entire power ^¬ fuel injection system. The control unit S, a plurality of sensor signals sl ... sn supplied, which are provided by respective sensors of the internal combustion engine. The control unit S evaluates sensor signals using a stored in a memory SP working program and by using further in the memory SP stored data and determines the currently induced power P of the internal combustion ^¬ machine, the instantaneous fuel temperature T, the instantaneous energy demand E of Internal combustion engine and the instantaneous injection duration T of the respective injector.

These parameters P, T, E and T are variables which influence the temperature gradient prevailing on the housing of the injectors. For example, the momentarily induced power P of the internal combustion engine serves as a measure of the combustion chamber temperature, the nozzle heating and the nozzle elongation. The instantaneous fuel temperature T serves, for example, as a measure of the needle cooling and the needle shortening. A high temperature gradient along the injector body and also between the nozzle body and the nozzle needle is in particular a presently high induced power of Brennkraftma ^¬ machine. This corresponds to a high energy input from the combustion chamber into the nozzle, resulting in a high nozzle temperature. Furthermore, large injection quantities at low fuel pressure lead to near-to-nozzle combustion. In the case of a low fuel temperature is a good

Cooling of the nozzle needle before. This is especially true in the presence of a long injection duration, as it is necessary for high induced power of the engine or low fuel pressure.

Furthermore, the control unit S also evaluates the opening ^{behavior of} the injector. A low energy requirement indicates easy opening. A low OPP2 time indicates a fast opening. A high OPP4 time indicates a slow closing.

For the aforementioned parameters P, T, E and T, a weighting factor determined in advance and stored in the memory SP is multiplied. Thus, the instantaneously induced power P is multiplied by a weighting factor kl, the instantaneous fuel temperature T by a weighting factor k2, the instantaneous energy requirement E by a weighting factor k3, and the instantaneous injection duration T by a weighting factor k4. These too

Weighting factors were determined empirically in advance and stored in memory SP.

From these parameters, each multiplied by a weighting factor, the criticality index I is determined in an adder A by means of an addition process:

I = kl * P + k2 * T + k3 * E + k4 * T. This determined criticality index I is fed to a computing unit R of the control unit S which determines control signals stl and / or st2 using the determined criticality index I, which is used to initiate Measures to reduce the thermal load of the injector can be used. One or more measures of the first reaction level RE 1 and by means of the control signals st2 one or more measures of the second reaction level RE2 are initiated by the control signals stl when the control unit S in the context of their control of the method described above with reference to FIG 2 the need for initiation of the above measures.

The invention described above is based on the fact that the behavior of a piezoelectrically operated injector is highly temperature-dependent. In particular, very high temperatures of the injector body and high temperature gradients along the

Injector bodies pose a challenge for injector operation or injector control. Special attention must also be placed on the intake of an injector, since in newly manufactured injectors during the first hours of operation an accelerated behavior change may occur in the form of an opening tension drift.

Typically, an injector in reference is adjusted to the materials from which it is made so that to today largely offset in the on ^¬ settled state thermal expansions of the individual Injektorbestandteile, so that the behavior of the injector ^¬ turbereich stable over a wide temperature. However, if under certain engine operating conditions, an end portion of the injector, such as the nozzle tip, heats up very rapidly, then the behavior of the injector can reach the limits of its stable working range.

A certain control intervention, which has no undesirable effects during normal operation when the injector has been reheated, can possibly lead to problems in a highly transient operation.

In order to avoid this and to be able to better estimate the possible effects of a current operating state, a kind of effect chain analysis is carried out in the invention described above in which the influencing variables relevant for the thermal load of the injector are weighted and from this a criticality index is determined.

A high weighting factor means a high influence of the respective parameter on the criticality index and vice versa.

The higher the criticality index is, the faster it must be for certain error signs resp. Symptoms that occur in the injection system are responding. A single high criticality index does not yet require that measures be taken to reduce the thermal load on the injector. Only when the high criticality index is present for a given period of time is it initiated Measures to reduce the thermal load on the injector. This approach increases the safety of error detection and ^¬ means that appropriate corrective action is initiated only when this is necessary.

In particular, the envisaged for monitoring the operation of the motor ^¬ fuel injection system control unit S is configured such that it specifies the length of time for which the criticality index must exceed the respective threshold in dependence on the level of criticality index calculated and the measure (s) purports to reduce the thermal load of the injector as a function of the height of he ^¬ mediated criticality, so that always one can be routed to ^¬ measured response to the respectively determined criticality in the paths.

Another advantage of the invention is that in addition to the occurring in highly transient operation or operation of the border area in ^¬ jektors temperature gradient along the injectors torkörpers a significantly above a predetermined operating temperature limit injector can be detected. Such high injector temperatures can be set, for example, in the event of a defect in the combustion chamber seal.

An advantageous development of the invention consists in not only taking into account the instantaneous values of the above-mentioned parameters when determining the criticality index, but also their gradients.

Claims

claims

A method of monitoring the operation of the internal combustion engine fuel injection system, comprising the steps of: determining a thermal load criticality index (I) of an injector of the fuel injection system, checking whether the determined criticality index is greater than a threshold (SW1),

if the criticality index determined is greater than the threshold, then checking whether the determined Kriti ^¬ kalitätsindex for a predetermined time period (tl) is greater than the threshold value, and

Initiation of a measure (RE1) for reducing the thermal load of the injector if the determined criticality index (I) for the predetermined time duration (t1) is greater than the threshold value (SW1).

2. The method according to claim 1, characterized in that the time duration is predetermined as a function of the height of the criticality index.

3. The method according to claim 1 or 2, characterized in that the measure for reducing the thermal load of the injector in dependence on the height of the determined criticality index is specified.

4. The method according to any one of the preceding claims, characterized in that the criticality index is determined by a evaluation ^¬ evaluation of several parameters to which the currently induced power (P) of the internal combustion engine, the current fuel temperature (T), the instantaneous energy demand (E ) and the current injection duration (T).

5. The method according to claim 4, characterized in that the instantaneous energy requirement (E) by an evaluation of the time

OPP2 of the injector is determined.

6. The method according to claim 4 or 5, characterized in that the instantaneous injection duration (T) is determined by an evaluation of the times OPP2 and OPP4 of the injector.

7. The method according to any one of claims 4 to 6, characterized in that for each of the parameters (Ρ, Τ, Ε, Τ) a weighting factor (kl, k2, k3, k4) is multiplied.

8. The method according to claim 7, characterized in that the criticality index is calculated by a combination of the respective multiplied by a weighting factor parameters.

9. The method according to any one of the preceding claims, characterized in that it comprises the following steps:

Checking whether the determined criticality index (I) is greater than a first threshold value (SW1),

if the check result is positive, checking whether the determined criticality index (I) has already been greater than the first threshold value for more than a first time duration (t1) and activating a measure of a first reaction level (RE1), if this is the case,

in the case of a negative check result, checking whether the determined criticality index (I) is greater than a second threshold value (SW2) which is smaller than the first threshold value,

if the check result is positive, checking whether the determined criticality index (I) has been greater than the second threshold value (SW2) for more than a second time duration (t2) which is greater than the first time duration (t1) and activating a measure of the second reaction level (RE2) if this is the case.

10. The method according to claim 9, characterized in that the measures of the first reaction level includes a reduction in the number of active injections.

11. The method according to claim 9 or 10, characterized in that in the presence of an automatic transmission to the measures of the first reaction level belongs to an automatic transition to a higher gear.

12. The method according to any one of claims 9 to 11, character- ized in that the measures of the second reaction level include a restriction of the speed and / or the torque of the internal combustion engine.

13. A device for monitoring the operation of the fuel injection system of an internal combustion engine, characterized marked ^¬ characterized in that it comprises a control unit (S), which is designed to control a method having the features specified in one of the preceding claims.