DE102010027986A1 - Fuel injection system i.e. common rail storage injection system, operating method for injecting fuel e.g. diesel, into combustion engine for vehicle, involves disabling support function of nozzles if nozzles of injection system leak - Google Patents

Abstract

The method involves holding pressure by carrying-out pressure support function on a pressure holding threshold value. A checking is done to check whether injector nozzles (12, 14) of a fuel injection system (6) leak. The pressure support function of the injector nozzles is disabled if the injector nozzles leak. Valves (38, 42, 44) are closed for a time interval if the pressure support function is disabled. An actual value of the pressure is monitored. The pressure is decreased over fuel return lines (40, 46, 48) if the pressure support function is disabled. An independent claim is also included for an arrangement for operating a fuel injection system to inject fuel into a combustion engine.

Description

The invention relates to a method for operating an injection system and an arrangement for operating an injection system.

State of the art

In injection systems injectors are provided with which the combustion chamber of an internal combustion engine fuel is supplied. The amount of fuel to be supplied may u. a. be controlled by a pressure of the fuel as a possible operating parameter.

For a vehicle with a start-stop function, all valves are closed during the stop phase for an injection system with dense injectors for quick re-start or restart, so that the pressure in a rail or an injection reservoir does not drop or only slowly decreases. If this measure provided for a start-stop operation is not carried out, the pressure during start-stop operation in the injection system can first be compressed by a pump, for example designed as a high-pressure pump, before injections can take place. Thus, the pressure can be maintained even with a leaking valve. However, if a nozzle of the injection system is leaking, a significant amount of fuel enters the cylinder and is ejected into the exhaust line at startup.

In the publication DE 195 13 158 A1 A device for detecting a leak in a fuel supply system in an internal combustion engine will be described. In this case, the fuel is conveyed by a fuel pump under pressure from the fuel tank, so that it passes via corresponding lines to the injection valves. In addition, a pressure sensor is provided which continuously measures the fuel pressure. With a computing device, control variables are formed starting from measured variables. The computing device determines the course of the fuel pressure after switching off the fuel pump and compares the course with a predeterminable course. If a deviation is detected, an error message is triggered.

The publication DE 10 2004 040 708 A1 describes a method for starting an internal combustion engine. In the context of this method, provision is made inter alia to determine a proportion of gaseous fuel in an intake system from a plurality of individual factors and furthermore to derive an adaptation factor, which describes possible changes in the leakage of the injectors during the service life of the internal combustion engine, from a current adaptation factor. Furthermore, the individual factors mentioned are taken from maps, these maps include various parameters, such as, for example, the fuel pressure of the internal combustion engine.

A method for checking and measuring the leakage of valves is in the document DE 198 09 926 C2 described. Among other things, fuel injection valves for internal combustion engines can be checked with this method. In this case, a valve to be tested is arranged in a measuring device and connected with its valve inlet to a high-pressure region and with its valve outlet to a low-pressure region of a test circuit of the measuring device. The test is subdivided into two test sections, wherein in a first test section a test takes place in the low-pressure region of the test circuit and in a second test section in a high-pressure region of the test circuit. In addition, a measurement signal of a determined pressure value in the low-pressure region of the test circuit is used as the control signal for the actuating device.

A method for testing a high-pressure fuel system is from the document DE 103 03 443 B3 known. The intended for an internal combustion engine high-pressure fuel system includes, inter alia, a plurality of injectors. As part of the method, the speed of the internal combustion engine is reduced to zero during an initialization phase and opened a pressure control valve for a predetermined time. In a first interval, the injection valves and pressure control valves are closed and the high-pressure pump is started. In addition, a pressure occurring in the central pressure accumulator pressure is measured by a pressure sensor. In a second interval, the high pressure pump is switched off with closed injection valves and closed pressure control valve. During fault diagnosis, the measured values or curves of the pressure are compared with setpoints.

Disclosure of the invention

Against this background, a method and an injection system with the features of the independent claims are presented. Further embodiments of the invention will become apparent from the dependent claims and the description.

In the context of the invention, inter alia, a diagnosis of a pressure-holding function that maintains a pressure of an injection system of an internal combustion engine at a suitable level for operation and thus pressure-holding threshold. In addition, measures can be taken to control the pressure via the pressure-holding function. With the pressure-holding function can be a sensory detected actual value of the pressure of the fuel, via an injection nozzle in a Cylinder of the internal combustion engine is injected, to be regulated to the pressure-holding threshold.

In this case, as a rule, the detection of a leaktightness or leakage of an injection nozzle takes place by evaluating a pressure signal provided by sensors and switching off the pressure-maintaining function in order to avoid consequential errors. Whether an injection nozzle is now leaking or leaking can be determined by comparing an in-service recorded actual value of the pressure with a sealing threshold value of the pressure of the fuel in the injection nozzle. An injector is usually leaky when the actual value of the pressure is significantly lower than the pressure hold threshold. Accordingly, the seal threshold is usually smaller than the pressure hold threshold.

With the invention, it is thus possible to provide a diagnostic method to detect the leakage of the injectors. Upon detection of the leak, measures are then taken to turn off the pressure holding function.

This prevents, for example, that during a shutdown phase of the internal combustion engine, as a rule, too much fuel can pass from an injection nozzle into the cylinder.

Furthermore, increased emissions and damage to a catalyst can be avoided by exothermic reactions or hotspots and thus overheated spots. A possibly resulting oil dilution by a fuel entry is thereby avoided.

If an injector is typically leaking through an incorrectly seated nozzle needle, it results in more fuel entering the cylinder than is normally provided. By reducing the pressure of the fuel, which takes place in the embodiment of the invention by switching off or deactivating the pressure-holding function, it can be avoided that too much fuel enters a combustion chamber or a cylinder of the internal combustion engine.

In start-stop operation of the internal combustion engine while implementing the pressure-holding function, all normally designed as switching valves valves, eg. The pressure control valve (DRV) or control valves of injectors or injectors, closed at the time of engine shutdown, thus the pressure of the fuel in a generally designed as a memory injection system (common rail) injection system remains constant or degrades only slowly. In one of the injector associated direct switch, the nozzle needle of the injector is driven by a designated drive so that the nozzle needle pressed directly against the nozzle seat and the injector or the injector is then hydraulically sealed.

In an embodiment of the method, the pressure in an injection reservoir or rail, in which the fuel, for example. Diesel, is stored under high pressure is monitored time-dependent during the Abstellphase. If the pressure falls within a defined time interval despite a closed valve by a value which is greater than a sealing pressure interval, and / or if the pressure has fallen below the sealing threshold value after a certain time interval, the pressure holding function is recognized as defective. In this case, an error bit can be set in a control unit for controlling the injection system.

Once the error, usually the leaking injector is detected or from the next stop of the internal combustion engine, the rail pressure and thus the pressure in the injection system via the pressure control valve (DRV) or via the control valve of the injector via a fuel return line targeted quickly degraded to prevent fuel from entering the cylinder through the injector.

In addition, the speed gradient at the cylinder, at the injection path of which a leak occurs, can be monitored at restart. If the speed gradient of the internal combustion engine at this cylinder falls below the sealing threshold value, this means that the leak is present at the injection nozzle. Thus, during the next stop of the internal combustion engine, the rail pressure can be reduced rapidly in a targeted manner via the pressure regulating valve of the injection accumulator or the switching valve of an injection nozzle via a fuel return line.

Otherwise, the pressure hold function may still remain active when the injector is sealed. That an injector is leaking during operation, may occur in an injection to be made. However, this must not be a permanent but merely sporadic state. For example, an injection nozzle may be leaky if a nozzle needle of the injection nozzle is not correctly positioned.

Usually, for a vehicle having a start-stop function in the event injectors or injectors of the injection system are sealed, for fast re-start all valves during a stop phase of the vehicle, in which a shutdown of the engine takes place closed. Thus, it follows that the pressure of the fuel in the example. As a common rail system formed injection system is not or only slowly decreases. Thus, the injections can start immediately upon restart be released to allow an even faster start.

If any component of the injection system, such as a valve, leaks, a predetermined pressure of the fuel can not be maintained. In the case of a leaking injection nozzle, there is additionally the risk that a considerable amount of fuel can still enter the exhaust line in the cylinder and at the start. With the design of the invention provided in the control of the pressure, it is possible to prevent such a pushing out of fuel in the cylinder and the exhaust system.

One application is in start-stop (ISS) injection-type injection systems, typically injectors without permanent leakage, which have a direct switch for actuating and thus controlling the movement of a nozzle needle injector nozzle and one use Pressure holding function with closed valves is possible.

The arrangement according to the invention is designed to carry out all the steps of the presented method. In this case, individual steps of this method can also be carried out by individual components of the arrangement. Furthermore, functions of the arrangement or functions of individual components of the arrangement can be implemented as steps of the method. In addition, it is possible for steps of the method to be realized as functions of at least one component of the arrangement or of the entire arrangement.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

Brief description of the drawings

1 shows a schematic representation of an embodiment of an arrangement according to the invention.

Embodiment of the invention

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described below in detail with reference to the drawings.

1 shows a schematic representation of an embodiment of an arrangement according to the invention 2 in the present embodiment, at least one control device 4 , which is adapted to an embodiment of a method according to the invention for operating an exemplary embodiment of an injection system shown here 6 for an internal combustion engine 8th , which is usually intended for a vehicle to perform.

The present injection system described 6 is designed as a so-called. Common rail or storage injection system. The injection system 6 includes an injection memory 10 and a number of injectors 12 . 14 , A first fuel supply line 16 the injection system 6 is to promote fuel 18 from a fuel reservoir 20 with the injection memory 10 connected. Along the first fuel supply line 16 is a pump designed as a high-pressure pump in the present embodiment 22 arranged to promote the fuel. With the pump 22 becomes the fuel 18 to the injection memory 10 transported and further pressurized, with a value of this pressure within the injection memory 10 corresponds to a pressure hold threshold value of a pressure provided for a memory injection.

The injection memory 10 is over several second fuel supply lines 24 . 26 with the injectors 12 . 14 connected. The injectors 12 . 14 the injection system 6 are combustion chambers 28 . 30 , which are designed here as a cylinder, the internal combustion engine 8th assigned. To operate the internal combustion engine 8th is provided that fuel 18 For example, diesel or gasoline in the injection tank 10 collected and pressurized via the injectors 12 . 14 in the combustion chambers 28 . 30 of the internal combustion engine 8th is promoted and burned.

As further components, the injection system 6 a first formed as a pressure sensor sensor 32 which is adapted to a value of the pressure of the fuel 18 within the injection memory 10 to investigate. Furthermore, the injection system 6 second sensors designed as pressure sensors 34 . 36 on, with each of these sensors 34 . 36 an injection nozzle 12 . 14 assigned and for determining a pressure of the fuel 18 inside the injectors 12 . 14 is trained.

In addition, the injection system points 6 a first valve 38 on, which here designed as a pressure control valve and the injection reservoir 10 assigned. If a value of within the injection memory 10 collected fuel 18 should be too high, it is provided that the first valve 38 opened and thus excess fuel 18 from the Injection storage 10 via a first fuel return line 40 in the fuel reservoir 20 is transported back.

As further components of the injection system 6 are second valves 42 . 44 provided, in each case one of these two second valves 42 . 44 designed as a switching valve and in each case an injection nozzle 12 . 14 assigned. If during operation of an injector 12 . 14 the fuel contained therein 18 should reach a high pressure, is a respective second valve 42 . 44 opened and fuel 18 via a respective second fuel return line 46 . 48 drained.

In the 1 schematically indicated second fuel return lines 46 . 48 open into the first fuel return line 40 , Thus, it is also possible to fuel 18 from the injectors 12 . 14 back to the fuel reservoir 20 to promote. Usually, the valves 38 . 42 . 44 along the fuel return lines 40 . 46 . 48 at appropriate positions, here at the beginning arranged.

This in 1 shown control unit 4 as at least one component of the arrangement according to the invention 2 depending on the definition also as a component of the injection system 6 be educated. However, it is alternatively or additionally possible that some components of the injection system 6 , for example, the sensors 32 . 34 . 36 , as components of the embodiment of the inventive arrangement shown here 2 are formed.

The control unit 4 includes an interface 50 over which the control unit 4 with at least one line 52 connected is. From this line 52 is in 1 only a short section is shown. However, it is envisaged that the lines 52 branched and with components of the injection system 6 connected is. This usually affects the sensors 32 . 34 . 36 , which are generally used to determine any operating parameters of individual components of the injection system 6 in the presently described embodiment for determining the pressure of the fuel 18 as operating parameters are formed.

The values determined for the operating parameters are provided by the sensors 32 . 34 . 36 as signals, for example. Pressure signals, to the controller 4 transmitted. About the usually arbitrarily branched line 52 is the control unit 4 also with the valves 38 . 42 . 44 the injection system 6 Depending on the design, if necessary, continue with the injection reservoir 10 , the injectors 12 . 14 as well as with the pump 22 connected. Thus, starting from the control unit 4 as signals commands for control and thus for the control and / or regulation of components of the injection system 6 be transmitted to these components.

The control unit 4 is thus suitable for functions of components of the injection system 6 in different, arbitrary operating situations to control and thus to control and / or to regulate. Thus, with the controller 4 for the injection system 6 inter alia, a so-called. Pressure hold function are executed. When performing this pressure holding function is provided that a pressure of the fuel 18 within the injection system 6 optionally, depending on the component, has a first pressure-holding threshold value. This pressure-holding threshold value may, in the context of an embodiment of the pressure-holding function, be provided by the control unit by providing corresponding control commands 4 for the components of the injection system 6 be suitably adjusted and thus maintained.

The pressure holding function is usually at a start-stop operation of the internal combustion engine 8th and thus for the realization of a start-stop function of the injection system 6 executed. When implementing the start-stop operation of the internal combustion engine 8th becomes the internal combustion engine 8th usually temporarily shut down at short notice. To help ensure that the pressure within the injection system 6 corresponds to the pressure-holding threshold, at least one valve controlled by the pressure-holding function 38 . 42 . 44 the injection system 6 closed as soon as the internal combustion engine 8th is turned off. By this measure is usually achieved that the pressure of the fuel 18 at a restart of the internal combustion engine to be carried out at short notice 8th can be restarted immediately during start-stop operation, as by maintaining the pressure at a level of the pressure hold threshold of the fuel 18 this over the injectors 12 . 14 at a restart of the internal combustion engine 8th immediately in the combustion chambers 28 . 30 can be injected.

The pressure hold function can be performed as a partial function of the start-stop function. Accordingly, switching off or deactivating the pressure-holding function usually means that the pressure of the fuel 18 in the injection system 6 , typically the pressure of the at least one injector 12 . 14 located fuel 18 , is sufficiently reduced, which by at least briefly opening at least one of the valves 38 . 42 . 44 can be done. A time interval during which at least one valve 38 . 42 . 44 can be set, taking into account an existing characteristic curve, so that the pressure targeted to one for the further operation of the injection system 6 and / or the internal combustion engine 8th appropriate level is regulated.

However, it is possible that in a running ordinary operation of the internal combustion engine 8th , but also in the start-stop operation of internal combustion engine 8th individual injectors 12 . 14 at least after single injections, but not necessarily permanently after several consecutive injections, can not be properly closed. This may, for example, be due to the fact that a nozzle needle of an injection nozzle 12 . 14 whose operation by the control unit 4 can be controlled, not properly moved back to a closed position after a successful injection.

This may result in that fuel 18 , albeit in small quantities, in a combustion chamber 28 . 30 seeps when an associated injector 12 . 14 is leaking and thus leaking. If so, for at least one injector 12 . 14 Usually in the execution of the pressure-holding function is the case, the pressure-holding function for the at least one injector 12 . 14 , usually for one of the at least one injection nozzle 12 . 14 associated second valve 42 . 44 , switched off or deactivated and thereby the associated second valve 42 . 44 open, leaving fuel 18 via a fuel return line 46 . 48 is to be dropped.

If several injectors 12 . 14 are leaking after an injection process, as an alternative or supplementary measure to be performed in the context of an embodiment of the invention for the first designed as a pressure control valve valve 38 that the injection memory 10 is assigned, the pressure-holding function starting from the control unit 4 shut down so that it is possible to simultaneously for all injectors 12 . 14 Fuel after opening the valve 38 over the first fuel return line 40 drain.

Evidence that at least one injector 12 . 14 is leaking, can be done by the pressure of the fuel in the at least one injector 12 . 14 and / or injection injection 10 measured and thereby determined actual value of the pressure can be compared with a sealing threshold. If the sealing threshold value, which is generally smaller than the already described pressure hold threshold value, for example, after a time interval to be defined, for at least its injection valve 12 . 14 is undershot, it is proved that the at least one injection valve 12 . 14 is leaking. As an alternative or supplementary measure to detect a possibly present leakage of an injection nozzle 12 . 14 can be provided that a time course of at least one actual value of the pressure is determined and monitored. If the actual value of the pressure within a time interval to be defined should fall by an alternative or additional further sealing threshold for a sealing-pressure difference, this may also be a possible indication of a leaking injection nozzle 12 . 14 evaluated and at least one of the thus identified as leaking injector 12 . 14 associated valve 28 . 30 be opened.

Regardless of whether at least an absolute actual value of the pressure or a change, typically a drop in the actual value of the pressure, is detected by a sealing threshold value of the sealing pressure difference, the pressure can be determined via a second sensor 34 . 36 in an injection nozzle 12 . 14 Measured actual value of pressure with one above the first sensor 32 in the injection memory 10 measured actual pressure of the fuel 18 be compared and a leakage of an injection nozzle 12 . 14 be proved if the difference in the different components of the injection system 6 simultaneously measured pressures exceeds a defined in this regard further sealing threshold.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19513158 A1 [0004]
• DE 102004040708 A1 [0005]
• DE 19809926 C2 [0006]
• DE 10303443 B3 [0007]

Claims (10)

Method for operating an injection system ( 6 ) for injecting fuel ( 18 ) in an internal combustion engine ( 8th ), wherein it is provided that a pressure of the fuel is maintained at a pressure-holding threshold value by carrying out a pressure-holding function, it being checked when carrying out the method whether at least one injection nozzle ( 12 . 14 ) of the injection system ( 6 ) is leaking, and wherein for the at least one injection nozzle ( 12 . 14 ) is switched off, if the injection nozzle ( 12 . 14 ) is leaking. Method according to Claim 1, which is used during a start-stop operation of the internal combustion engine ( 8th ), which provides that at a time when the internal combustion engine ( 8th ), at least one valve closed by the pressure maintenance function ( 38 . 42 . 44 ) of the injection system ( 6 ) is opened. Method according to Claim 2, in which the at least one valve ( 38 . 42 . 44 ) is opened for a time interval when the pressure hold function is turned off. Method according to one of the preceding claims, in which at least one actual value of the pressure is determined and compared with a sealing threshold, which is defined for the pressure, wherein the pressure holding function is switched off, if the at least one actual value of the seal Threshold deviates. The method of claim 4, wherein a time course of the at least one actual value of the pressure is monitored. Method according to one of the preceding claims, wherein the pressure via at least one fuel return line ( 40 . 46 . 48 ) is canceled when the pressure-holding function is turned off. Arrangement for operating an injection system ( 6 ) for injecting fuel ( 18 ) in an internal combustion engine ( 8th ), the injection system ( 6 ) at least one injection nozzle ( 12 . 14 ) and the arrangement ( 2 ) at least one control device ( 4 ), wherein the at least one control unit ( 4 ) is adapted to a pressure of the fuel ( 18 ) by maintaining a pressure-holding function at a pressure-holding threshold and checking whether the at least one injection nozzle ( 12 . 14 ) is leaking, and wherein the at least one control unit ( 4 ) is adapted to that for the at least one injection nozzle ( 12 . 14 ) to shut off provided pressure holding function, if the injector ( 12 . 14 ) is leaking. Arrangement according to claim 7, which has an injection memory ( 10 ) and a injection memory ( 10 ) associated with the pressure-holding function, wherein the pressure regulating valve is open when the pressure-holding function is to be switched off. Arrangement according to claim 7 or 8, which is one of the at least one injection nozzle ( 12 . 14 ) associated with the pressure-holding function is to be controlled, wherein the switching valve is open when the pressure-maintaining function is to be switched off. Arrangement according to one of claims 7 to 9, the at least one sensor ( 32 . 34 . 36 ) adapted to detect an actual value of the pressure.

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