CN114439634A

CN114439634A - Method for identifying a drifting injector in a fuel injection system

Info

Publication number: CN114439634A
Application number: CN202111271357.XA
Authority: CN
Inventors: B·J·阿提塔; G·P·安东尼; K·甘迪班
Original assignee: Robert Bosch GmbH; Bosch Ltd
Current assignee: Robert Bosch GmbH; Bosch Ltd
Priority date: 2020-10-31
Filing date: 2021-10-29
Publication date: 2022-05-06
Also published as: DE102021211924A1

Abstract

The invention relates to a method for identifying a drifting injector in a fuel injection system. An electronic control unit (10) in a fuel injection system (12), the fuel injection system (12) comprising at least a common rail (14) and a fuel injector (16), the electronic control unit (10) being configured to: receiving a rail pressure signal from a pressure sensor in the common rail from the common rail (14); controlling the injection timing of the fuel injector (16) by controlling the actuation of the injector. The electronic control unit can use the engine speed variation and injection quantity deviation to identify a particular drifting injector in a set of injectors in the fuel injection system 12.

Description

Method for identifying a drifting injector in a fuel injection system

Technical Field

The invention relates to a method for identifying a drifting injector in a fuel injection system.

Background

In common rail systems, the fuel injection system includes components such as a fuel tank, a fuel feed pump/pre-feed pump, a fuel filter, a high pressure pump, a common rail, and injectors. These components are connected by high-pressure and low-pressure circuits of the fuel injection system. The fuel injection system components may be mounted on the engine head based on space availability. Fuel from the fuel tank is pumped by the pre-supply pump via a filter to the high-pressure pump. The high-pressure pump pressurizes fuel, and supplies it to the common rail and the injectors through a high-pressure pipe.

With this particular disclosure, we wish to focus on fuel injection systems in which there is no pressure control valve or pressure relief valve downstream of the common rail. Thus, the injector return flow or return path of the injector is the only path that additional fuel will flow back to the fuel tank. The basic function of the injector return flow is to support fuel injection, since the injector needle will not lift if there is no return flow.

During operation of the fuel injection system, a series of injectors are operated in a particular sequence to ensure that the injectors inject fuel in different combustion chambers. The injection timing and the injection quantity are controlled by an electronic control unit in the fuel injection system. These two parameters are calculated separately for each of a plurality of injectors. It is expected that the injector will continue to inject a certain amount of fuel and for a certain period of time. However, over time, different components of the fuel injector may wear. Due to wear of the injector, if there is no signal, the injector may continue to inject at night, which is considered an injector failure, and in this case there is no other option than replacing the injector. Due to wear, it is also possible that the fuel injector injects a higher than expected amount of fuel even if the energization time is set to a level at which the injector is expected to inject the predefined amount. Due to wear, it is also possible that the injector injects fuel in an amount lower than the expected amount even if the energization time of the injector is set to a level at which the injector is expected to inject the predefined amount. In both cases, the injector is a drift injector in the event that the fuel injector injects less than a predefined amount or the fuel injector injects less than a predefined amount. The drift phenomenon affects individual injectors and becomes more pronounced over time.

IN201841007156 discloses a diagnostic tester and method to identify drift IN an injector fitted IN an internal combustion engine. The method comprises the following steps: reading a compensation value of the injector for the fuel quantity; triggering a Morse test to collect friction data for the engine; declaring the injector to have a drift if the compensation value of the injector does not correspond to the friction data.

DE 10232356 a1 discloses a process as follows: the start of injection and the end of injection of the injector are compared with the stored values of these variables and the value of the start of injection is compared and/or the injection duration is changed such that the deviation resulting from the comparison is minimized. However, such drift correction has the following disadvantages: it is not possible to accurately detect the start and end of injection at all engine load points.

DE102007060768 discloses a method for drift detection and drift compensation of an injector for injecting fuel into a combustion chamber of an internal combustion engine by the following steps: sampling a signal indicative of rail pressure; converting the time discrete signal into a frequency space; performing feature extraction from the spectrum and establishing at least one feature vector; comparing the at least one feature vector with at least one corresponding feature vector previously determined and characterizing a normally operating injector and stored in memory; if a deviation of the at least one characteristic vector from the stored characteristic vectors is determined by a predetermined amount, a deviation of the injection quantity due to drift is inferred.

Some of the challenges of the above techniques known in the prior art are that it is very difficult to diagnose which particular injector in the set of injectors is actually drifting. Since the above method does not allow pointing towards a drift injector, the compensation will in principle be applied to the whole group of injectors. Thus, in certain situations, there may be overcompensation for drift.

It is an object of the concepts of the present disclosure to provide a method by which we can specifically identify one or more injectors from the entire set of injectors in a fuel injection system.

Drawings

The different modes of the present disclosure are disclosed in detail in the specification and illustrated in the accompanying drawings, wherein:

FIG. 1 illustrates a representative fuel injection system for purposes of the present disclosure;

FIG. 2 illustrates a block diagram representing a method to identify a drifting injector in a fuel injection system according to the present disclosure.

Detailed Description

FIG. 1 illustrates a representative fuel injection system for purposes of the present disclosure. An electronic control unit 10 in a fuel injection system 12 is disclosed. The electronic control unit 10 is configured to: receiving an engine speed value from an engine speed sensor; a fuel balance control correction is applied based on the received engine speed value from the engine speed sensor and the known fuel injector firing pattern. The electronic control unit 10 is characterized in that it is configured such that: monitoring 102 a rail pressure gradient over a distance traveled by a vehicle in which the fuel injection system is operating; comparing 104 the monitored rail pressure gradient to a threshold rail pressure gradient value; learning 106 an engine speed variation from an engine speed sensor and correlating the engine speed variation to a particular engine cylinder by a known fuel injector firing pattern; applying 108 a fuel balance control correction to correct engine speed variations and to correct engine speed to a threshold engine speed value by changing a power-on time of a fuel injector fired as part of a known firing pattern; mapping 110 a fuel injection quantity deviation for each of the fuel injectors while applying the fuel balance control correction; measuring 112 engine speed variation and measuring fuel injection quantity deviation in real time using an engine speed sensor while applying fuel balance control correction for each of the fuel injectors; identifying 114 a drifting injector by comparing the measured value of fuel injection quantity deviation with the mapped value of fuel injection quantity deviation; identifying 116 the identified drift injector as a drift injector if the injection quantity deviation count is greater than the threshold injection quantity deviation count; and alerting (118) the user based on the confirmation.

During operation of the engine and the fuel injection system, fuel from the fuel tank is pumped by the feed to the filter. The filter removes water content and particulate matter from the fuel and delivers the fuel to the high pressure pump. The high-pressure pump pressurizes fuel and sends the fuel to the common rail. The common rail (also referred to as an accumulator) is the component where the fuel is accumulated and maintained at the desired pressure required for combustion. An engine speed sensor is also provided in the engine. The engine speed sensor provides information about the speed of the engine. Each engine also has a known fuel injector firing pattern. There will be an expected engine speed change when a particular injector in the firing pattern is fired. When the injector is not aged, or when injector wear is low, the engine speed measured by the engine speed sensor will not exceed the threshold engine speed value during the ignition mode of the injector. However, this changes as the injector ages and wears. The electronic control unit 10 already has information about the ignition mode of the fuel injectors and it also receives signals from an engine speed sensor. Thus, the electronic control unit is in position to identify the particular injector that is drifting based on engine speed. This is the basic principle of operation of the electronic control unit 10 according to the present disclosure and is also important for understanding the operation of the method 100 according to the present disclosure.

FIG. 2 illustrates a block diagram representing a method to identify a drifting injector in a fuel injection system according to the present disclosure. The fuel injection system 12 includes a plurality of fuel injectors, one for each of a plurality of engine cylinders in the engine. The fuel injection system is operating in a vehicle. The method comprises the following steps: monitoring 102 a rail pressure gradient over a distance traveled by a vehicle in which the fuel injection system is operating; comparing 104 the monitored rail pressure gradient to a threshold rail pressure gradient value; learning 106 an engine speed variation from an engine speed sensor and correlating the engine speed variation to a particular engine cylinder by a known fuel injector firing pattern; applying 108 a fuel balance control correction to correct engine speed variations and to correct engine speed to a threshold engine speed value by changing an energization time of an ignited fuel injector; mapping 110 a fuel injection quantity deviation for each of the fuel injectors while applying the fuel balance control correction; measuring 112 engine speed variation and measuring fuel injection quantity deviation in real time using an engine speed sensor while applying fuel balance control correction for each of the fuel injectors; identifying 114 a drifting injector by comparing the measured value of fuel injection quantity deviation with the mapped value of fuel injection quantity deviation; identifying 116 the identified drift injector as a drift injector if the injection quantity deviation count is greater than the threshold injection quantity deviation count; the user is alerted 118 based on the confirmation.

The method 100 may be explained in further detail in the following manner. Monitoring 102 of the rail pressure gradient may be explained as follows. During the ignition state of the engine (also referred to as the T15 state), rail pressure and total kilometers traveled by the vehicle are monitored. As previously mentioned in the background of the invention, the performance of an injector degrades over the life of the injector, for which reason monitoring of rail pressure gradients is performed over the kilometer of travel by the vehicle. Thus, during the steps associated with monitoring 102, rail pressure is continuously monitored over the life of the vehicle, and the rail changes (also referred to as rail pressure gradients) over the time period are recorded. Thus, a rail pressure gradient map may be obtained. Further, during implementation of the method 100 according to the present disclosure, a threshold value of the rail pressure gradient will be defined based on the distance traveled by the vehicle and the recorded values or dust particle ingress. This threshold value already takes into account the real-time values of the rail pressure and the rail pressure gradient. The threshold value for the rail pressure gradient is a fixed value for a particular fuel injection system.

During operation of the engine, real-time rail pressure values are measured, and the monitored rail pressure gradient is compared to a defined threshold value in a comparison step 104 of the method 100. If the monitored rail pressure gradient exceeds a defined threshold for the rail pressure gradient, this is indicative of the fact that there may be some deviation due to drifting the injector. The defined threshold is typically set to a value that will cause changes in the rail pressure gradient to occur due to drifting the injector and not due to any other factors. However, if the injector drift is within limits, this will mean that there is a leak in the high pressure system, and this can be communicated to the user.

During operation of the engine, there is also a learning operation 106 that is performed as part of the method 100. During a learning operation 106, engine speed variations are identified from signals received by the engine speed sensor, and further, the electronic control unit 10 has already had information about the ignition pattern of the fuel injectors. Thus, a correlation may be established between engine speed changes and the particular injector fired. Using this correlation, a clear link can be established, i.e. the ignition of a particular injector will result in an increase in engine speed. During operation of the engine, it may be observed that during ignition of a particular injector, the engine speed increases beyond an engine speed threshold. Similarly, it may be observed that during ignition of a particular injector, the engine speed decreases beyond an engine speed threshold. It is normally expected that there will be no drift from the injector, and the engine speed will not be above or below the engine speed threshold.

Further, as part of method 100, since the engine speed threshold is not maintained, a correction must be applied to maintain the engine speed threshold, referred to as a fuel balance control correction. The fuel balance control correction is applied 108 by changing the energization time of the particular fuel injector that is fired. In the next step, a map 110 of fuel injection quantity deviations is mapped for each of the ignited fuel injectors. The map provides, in principle, an indication of the value of the deviation of the injector in terms of the fuel injection quantity. The map can provide an indication of positive drift injectors and negative drift injectors. The learning operation 106 and the mapping operation 110 are executed in the ecu 10 of the fuel injection system 12. However, it must be understood that learning 106 and mapping 110 may or may not be process steps that may be performed continuously. Learning 106 and mapping 110 may be performed at certain predefined intervals or under certain engine or vehicle operating conditions.

Although the learning operation 106 and mapping operation 110 are used, the method has identified which injector may be drifting, but it is equally important that the methodology be robust and not provide an indication based on only one reading or one measurement. As previously mentioned in the practical implementation of the method, the learning 106 and mapping 118 processes will not be performed continuously, and these processes may be performed under certain engine or vehicle operating conditions. To ensure that the method 100 is robust, it is also necessary to know the real-time value of the engine speed change and the change in the fuel injection amount. To this end, in the measuring operation 112, a real-time engine speed value is determined by an engine speed sensor, and a change in the fuel injection quantity is calculated by the ecu 10 while mapping the fuel injection quantity deviation while applying the fuel balance control correction. Based on the measured values of the real-time changes in fuel injection quantity values, a particular drifting injector is identified in an identifying operation 114.

In a further step of making the method 100 even more robust, in a confirmation operation 116, a drifting injector is identified as a drifting injector if the injection quantity deviation count is greater than the threshold injection quantity deviation count. This is to ensure that a single instance of deviation in injection quantity will not be eligible for determining a drift injector. Based on a confirmation operation 116 that the identified injector is actually drifting, an alert 118 is provided. The alert 118 may be a visual alert, an audio alert, an audiovisual alert, and the like.

An advantage of the method for identifying drifting injectors according to the present disclosure is that with this method we can specify which particular injector is drifting and thus compensation can be applied only to that injector, not to the entire group of injectors. Further, this also reduces overcompensation that may be applied to some injectors that may not have any drift. This method provides a method to identify a drifting injector using engine speed variations, so no additional hardware would be required to identify the drifting injector.

It must be understood that the fuel injection system shown in the figures is illustrative only and does not limit the scope of the present disclosure to the fuel injection system represented therein. The scope is limited only by the scope of the claims.

Claims

1. A method (100) for identifying drifting injectors in a fuel injection system (12), the fuel injection system (12) including a plurality of fuel injectors (16), each fuel injector (16) for a plurality of engine cylinders in an engine, the method comprising the steps of:

-monitoring (102) a rail pressure gradient over a distance travelled by the vehicle in which the fuel injection system is operating;

-comparing (104) the monitored rail pressure gradient with a threshold rail pressure gradient value;

-learning (106) an engine speed variation from an engine speed sensor and correlating the engine speed variation with a specific engine cylinder by a known fuel injector firing pattern;

-applying (108) a fuel balance control correction to correct the engine speed variation and to correct engine speed to a threshold engine speed value by changing the energisation time of the fired fuel injector;

-mapping (110) a fuel injection quantity deviation for each of the fuel injectors while applying the fuel balance control correction;

-measuring (112) engine speed variations and measuring fuel injection quantity deviations in real time using an engine speed sensor while applying the fuel balance control correction for each of the fuel injectors;

-identifying (114) a drifting injector by comparing the measured value of fuel injection quantity deviation with the mapped value of fuel injection quantity deviation;

-identifying (116) the identified drift injector as a drift injector if the injection quantity deviation count is greater than a threshold injection quantity deviation count;

-alerting (118) the user based on the confirmation.

2. An electronic control unit (10) in a fuel injection system (12), the electronic control unit (10) being configured to:

-receiving an engine speed value from the engine speed sensor;

-applying a fuel balance control correction based on the received engine speed value from the engine speed sensor and a known fuel injector firing pattern;

characterized in that said electronic control unit (10) is configured to:

-monitoring (102) a rail pressure gradient over a distance travelled by the vehicle;

-comparing (104) the monitored rail pressure gradient to a threshold rail pressure gradient value;

-applying (108) a fuel balance control correction to correct the engine speed variation and to correct engine speed to a threshold engine speed value by changing the energisation time of the ignited fuel injector as part of a known ignition pattern;

-alerting (118) the user based on the confirmation.