DE10061855A1 - Method, computer program and control and / or regulating device for operating an internal combustion engine, and internal combustion engine - Google Patents

Abstract

In an internal combustion engine (10), in particular a motor vehicle, the fuel is conveyed from a fuel pump (32) into a fuel line (26). In order to be able to reliably detect a fuel leak, the internal combustion engine (10) is in a state in which the fuel is not delivered by the fuel pump (32) and the fuel line (26) is part of a closed fuel system (20-26) (80, 94), the fuel pressure in the closed fuel system (20-26) is recorded (82, 86, 100, 104). If the pressure in the closed fuel system (20-26) drops by an amount that is above a limit value (88, 106), a message is issued (90, 108).

Description

State of the art

The present invention initially relates to a method for operating an internal combustion engine, in particular one Motor vehicle in which the fuel from a Fuel pump is pumped into a fuel line.

Such a process is known from the market. It will z. B. used in internal combustion engines with gasoline Direct injection (BDE) work. At a Internal combustion engine using such a method is operated, the injectors are directly to the Firing chambers arranged. The fuel will be the Injectors through a fuel rail fed, which is also referred to as "Rail". The Fuel in the fuel rail is from a High pressure fuel pump put under very high pressure. The fuel will turn to the high pressure fuel pump fed by a low pressure fuel pump.

The high pressure fuel pump is directly on the Flanged internal combustion engine and is by the Camshaft driven. The seal between the  oil-filled area of the internal combustion engine and the Fuel filled area of the high pressure fuel pump takes place via one or more O-rings. This seal should be as good as possible, as it must be avoided must have fuel in from the high pressure fuel pump reaches the oil-filled area of the internal combustion engine and there the oil is diluted, which will eventually damage it the internal combustion engine can lead. For this reason, in Generally between the fuel-filled area of the High pressure fuel pump and the oil filled area of the Internal combustion engine provided a space from which fuel leaked off and z. B. to Fuel tank is fed back.

However, if B. due to wear or Manufacturing defects to a break of the sealing elements between High pressure fuel pump and internal combustion engine, it can come to a leak, which nevertheless leads to an overflow of Fuel in the oil filled area of the Internal combustion engine leads. Such leakage could e.g. B. can be recognized by sensors, but what from cost and Maintenance is undesirable.

Another method of the type mentioned is also known from the market and is used by Internal combustion engines used with Intake manifold injection work. In this case, a Low pressure fuel pump from the tank directly into one Fuel line on which the injection valves are arranged are. The injectors are in a de-energized state closed. However, one of the injectors may be stuck the one under pressure in the fuel line Fuel with the internal combustion engine turned off from the Drain the injection valve into the intake pipe. This can be the case with Restarting the engine can cause problems.  

The present invention therefore has the task of a To further develop methods of the type mentioned at the beginning that with him reliably and in simple and cost effective way of fuel leakage can be recognized.

This task is initiated in a procedure mentioned type in that in a state of Internal combustion engine in which no fuel delivery done by the fuel pump and the fuel line Is part of a closed fuel system that Fuel pressure in the closed fuel system is detected and then when the pressure in the completed fuel system drops by an amount which is above a limit value, a message is issued.

Advantages of the invention

The method according to the invention assumes that also then when the fuel pump has no fuel in the Fuel line promotes what z. B. is the case if the engine is not operating, the pressure in the fuel line is maintained, that is Is part of a closed system. This Approach is chosen to prevent yourself when the pressure in the fuel line drops Vapor bubbles form when the engine is restarted Internal combustion engine affect the fuel delivery. In such a state, the pressure in this locked fuel system recorded and determined this can result in the pressure falling more than permitted for a leak in this closed fuel system getting closed. The measurement of the pressure in the locked fuel system is without additional Sensor possible because a pressure sensor for regulating the Fuel pressure in the operation of the internal combustion engine anyway  is available.

With the method according to the invention it is therefore possible reliably detect a fuel leak without an additional sensor or expensive leakage Capture techniques are required. The Internal combustion engine can with the inventive method can therefore be operated more reliably without additional There are costs.

Advantageous developments of the invention are in Subclaims specified.

In a first preferred development of the The inventive method is mentioned that the message only occurs when the amount of pressure drop the limit within a certain period of time exceeds. This ensures that a Pressure drop due to e.g. B. a temperature change in Fuel system that is relatively slow from a difference in pressure due to leakage can be. This will increase the reliability of the Leakage detection increased.

It is also proposed that the pressure in the Fuel system for a period after Switching off the internal combustion engine is detected. After this There is no funding for switching off the internal combustion engine of the fuel, so that this condition becomes Leakage detection is particularly suitable.

But it is also possible that during operation of the Internal combustion engine in a suitable fuel pump Operating point switched off briefly and the pressure drop is detected in the closed fuel system. The Leakage testing can thus be performed more often  be what security when operating the Internal combustion engine increased again.

It is particularly preferred if during a Thrust phase of the internal combustion engine the fuel pump turned off and the pressure in the completed Fuel system is detected. During the overrun phase of the Internal combustion engine is used in today's internal combustion engines Generally no fuel in the combustion chambers of the Internal combustion engine injected. A promotion of So there is no fuel during this phase required so that the fuel pump is turned off can be without the operation of the internal combustion engine is affected.

Under the term "notification" introduced above various measures can be understood. So it can Message z. B. setting a certain flag state and / or an entry in a fault memory and / or the Output of a warning and / or alarm message include. Regarding the flag state, it is possible that the flag if leakage is detected; but it is also possible that a flag set in the normal state at a detected leakage is deleted.

The flag state or the entry in the error memory can then z. B. from a diagnostic unit in a workshop be read out so that in the workshop the Leakage condition of the fuel system can be detected. The user is informed by a warning and / or alarm message the internal combustion engine, e.g. B. the driver of one Motor vehicle, pointed out the leakage problem, so that he take appropriate measures on his own, e.g. B. can go to a workshop. In this context noted that, if necessary, several Limit values can be specified with which the  Pressure drop is compared. That way the degree the leakage is determined and dependent on this for example, a warning or an alarm message is issued become.

To prevent the leakage in the event of a detected leak Internal combustion engine is damaged by z. B. Fuel gets into the oil circuit of the internal combustion engine, the oil diluted and thereby the lubricating effect of the oil is impaired in a preferred development of the inventive method proposed that at the start the internal combustion engine the fault memory and / or the flag read out and at an entry in the error memory and / or a safety measure if the flag state is appropriate carried out, preferably another tempering of the Internal combustion engine is prevented.

Internal combustion engines with gasoline direct injection (BDE) typically include a fuel system with a High pressure area and a low pressure area. The pressure in the high pressure range is usually above one Pressure sensor detected. To also the pressure in the To be able to monitor the low pressure area and thereby a to be able to determine appropriate leakage proposed according to the invention that if the Fuel pump does not promote a high pressure area of the Fuel system with a low pressure area of the Fuel system is connected so that in them roughly there is the same pressure and the pressure in the High pressure area is detected.

In a development of this embodiment, it is proposed that that the high pressure area with the low pressure area only is then connected when the temperature in the High pressure area is so low that when lowered the pressure in the high pressure area to the pressure in the  Low pressure area in the fuel no vapor bubbles arise. This training takes into account the fact that those heated during operation of the internal combustion engine Parts of the internal combustion engine to heat the Fuel line and therefore the fuel and therefore too lead to an increase in the vapor pressure of the fuel. Would the pressure of such a heated fuel could be lowered in the corresponding system Vapor bubbles form that are fueling affect. This could be the case with a so-called "Hot start" of the internal combustion engine, if it is in warm condition is started again, to start problems to lead. Such problems are caused by the invention Measure avoided.

The invention also relates to a computer program which is suitable for performing the above method if it is running on a computer. It is special preferred that the computer program on a memory, is stored in particular on a flash memory.

The invention further relates to a control and / or Control device for operating an internal combustion engine, especially a motor vehicle in which the fuel from a fuel pump to a fuel line is promoted. To with such a tax and / or Control unit a leak in the fuel system reliably To be able to recognize, it is proposed according to the invention that it is used to control and / or regulate the above Process is suitable. Again, this is special preferred if the control and / or regulating device with a of the above-mentioned computer programs.

Finally, the invention relates to one Internal combustion engine with a fuel pump, which Feeds fuel into a fuel line, and with one  Pressure sensor, which measures the pressure in the fuel line detected. To ensure that at such a time Internal combustion engine fuel leakage reliable is recognized, it is proposed according to the invention that the Internal combustion engine a control or regulating device of the above mentioned type, which includes the signals of the pressure sensor processed.

drawing

Exemplary embodiments of the invention are described below Reference to the attached drawing in detail explained. The drawing shows:

Fig. 1 is a block diagram of a first embodiment Beipiels an internal combustion engine;

FIG. 2 shows a partially sectioned side view of a high-pressure fuel pump of the internal combustion engine from FIG. 1;

. FIG. 3 is a flow chart of a first method for operating the internal combustion engine of Figure 1;

FIG. 4 shows a flowchart of a second method for operating the internal combustion engine from FIG. 1; FIG. and

FIG. 5 shows a block diagram of a second embodiment of an internal combustion engine.

Description of the execution examples

In Fig. 1, an internal combustion engine is identified overall by reference numeral 10. It comprises a plurality of combustion chambers, of which only the combustion chamber 12 is shown, for reasons of clarity, to which air is supplied via an intake pipe 14 . The exhaust gases are discharged via an exhaust pipe 16 .

Fuel is supplied to the combustion chamber 12 directly through injection valves, of which only one is shown in FIG. 1. This has the reference number 18 . The injection valve 18 is connected to a fuel rail 20 , referred to as a “rail”. The fuel is in turn conveyed into it by a high-pressure fuel pump 22 and pressurized. A high-pressure fuel line 24 is provided between the high-pressure fuel pump 22 and the fuel manifold 20 .

A low-pressure fuel line 26 leads from the high-pressure fuel pump 22 to a tank 28 . A fuel filter 30 and an electric low-pressure fuel pump 32 are arranged in the low-pressure fuel line 26 . A low-pressure regulator 36 is connected to the low-pressure fuel line 26 via a branch line 34 . A leakage line 38 also connects the high-pressure fuel pump 22 to the branch line 34 .

Between the high-pressure fuel pump 22 and the filter 30 , a check valve 40 blocking the tank 28 and a pressure damper 42 are also provided. A return flow line 44 is connected on the one hand between the high pressure fuel pump 22 and the fuel manifold 20 to the high pressure fuel line 24 and on the other hand between the pressure damper 42 and the second check valve 40 with the low pressure fuel line 26 . A quantity control valve 46 is interposed in the return flow line 44 . This is a 2/2-way switching valve which completely blocks the return flow line 44 in one extreme position and completely releases the return flow line 44 in the other extreme position. The quantity control valve 46 is actuated by a magnetic actuator 48 . In the de-energized state, the quantity control valve 46 is pressed into its fully open extreme position by a spring 50 .

The fuel rail 20 is connected to a pressure relief valve 52 , which in turn is fluidly connected to the low pressure fuel line 26 at a location between the pressure damper 42 and the filter 30 . The pressure relief valve 52 is a spring-loaded ball valve.

The pressure in the fuel collecting line 20 is detected by a pressure sensor 54 , which sends corresponding signals to a control and regulating device 56 . On the input side, the control and regulating device 56 is also connected to a position transmitter 58 of an ignition lock (not shown). On the output side, the control and regulating device 56 controls the magnetic actuator 48 of the quantity control valve 46 , the electric fuel pump 32 and the injection valve 18 .

In normal operation, the fuel rail 20 is pressurized by the high pressure fuel pump 22 . The pressure of the fuel in the fuel manifold 20 is regulated by a closed control loop, which includes the pressure sensor 54 and the quantity control valve 46 .

The high-pressure fuel pump 22 is shown in detail in FIG. 2. It is a piston pump with a displacement piston arranged in a star shape (without reference number). It comprises a housing 60 in which a central drive shaft 62 is received. The drive shaft 62 is supported in the housing 60 at the end by bearings 64 and 66 . On the left side in FIG. 2, the housing 60 of the high-pressure fuel pump 22 has an opening 68 which is coaxial with the drive shaft 62 . The end of a camshaft 70 engages in the opening 68 and is connected in a rotationally fixed manner to the drive shaft 62 via a coupling (not described in more detail here). The camshaft 70 is also shown in FIG. 1. The mechanical connection between the drive shaft 62 and the camshaft 70 is indicated in FIG. 1 by a dashed line.

The housing 60 is flanged to the engine block (not shown) of the internal combustion engine 10 . The fuel-filled area lying on the right side of the high-pressure fuel pump 22 in FIG. 2 is sealed off from the oil-filled area of the internal combustion engine 10 on the left-hand side in FIG. 2 via shaft seals 72 and 74 . A space 76 is formed between the two seals 72 and 74 , from which leakage fuel can be conveyed to the tank 28 via the delivery line 38 .

With an oversized leak, e.g. B. at a break of the seal 72 and / or the seal 74 , however, there is a risk that fuel gets into the oil-filled area of the internal combustion engine 10 . This would result in a dilution of the oil and a deterioration in the lubricating properties of the oil, which can lead to damage to the internal combustion engine 10 . In order to be able to recognize such an oversized leakage, a computer program is stored in the control and regulating device 56 , with which the internal combustion engine 10 can be operated in the following way (see FIGS. 3 and 4):
After the start of the computer program (block 78 in FIG. 3), it is checked whether the internal combustion engine 10 is in operation. This is done by querying the position transmitter 58 of the ignition lock. If this is brought from the operating position into the exhibition, this is recorded in block 80 . In this case, the result of the query is "no" and it is assumed that the fuel pump 32 is also not delivering. However, all other types of detection of a standstill of the fuel pump 32 are also possible . The pressure signal from the pressure sensor 54 is then read out in a block 82 and temporarily stored as pressure P1.

Since the magnetic actuator 48 is de-energized when the internal combustion engine 10 is switched off, the 2/2-way quantity control valve 46 is pressed into its fully open position by the spring 50 , so that the high-pressure fuel line 24 is connected to the low-pressure fuel line 26 via the return flow line 44 is. The same pressure prevails in both fuel lines 24 and 26 , which is detected by pressure sensor 54 . In an exemplary embodiment (not shown), the temperature of the internal combustion engine is detected before a connection between the high-pressure area and the low-pressure area, and the connection is only established if there is no fear of temperature-related vapor bubble formation in the high-pressure area when the pressure in the high-pressure area drops.

In an exemplary embodiment, not shown, the quantity control valve 46 is closed in the de-energized state. In this way, an undesirable pressure drop in the high-pressure fuel line 24 is avoided by a connection to the low-pressure fuel line 26 , which could lead to the formation of vapor bubbles in the high-pressure fuel line 24 or the fuel manifold 20 at a relatively high operating temperature of the internal combustion engine 10 . This would in turn be problematic in a subsequent starting process. In the case of the corresponding method, it would therefore first be waited until the temperature has dropped so far that there is no fear of vapor bubbles forming when the pressure in the high-pressure fuel line 24 or the fuel collecting line 20 is reduced. Only then would the quantity control valve 46 be actively controlled and opened by the control and regulating device 56 .

After the pressure P1 has been measured in block 82 , a certain time t is waited for (block 84 ). After this time interval t has elapsed, the pressure P2 detected by the pressure sensor 54 is read out in block 86 . The difference between the pressure P2 and the pressure P1 is then formed in a block 88 . This is the pressure drop that occurred in the closed fuel system, which is formed from the fuel rail 20 , the high-pressure fuel pump 22 , the high-pressure fuel line 24 and the low-pressure fuel line 26 , during the period t. This pressure drop P1-P2 is compared in block 88 with a limit value PG. If the amount of pressure drop is greater than the limit value, the answer to the question in block 88 is "yes", which indicates a leak in the fuel system, a flag F is set in block 90 . The method illustrated in FIG. 3 ends in an end block 92 . An uncritical pressure increase with regard to a leak, which z. B. can be triggered by heating the fuel, can be recognized from the sign of the difference P1-P2.

If it is determined in block 80 that the internal combustion engine 12 is in operation, the answer is "yes", a check is made in a block 94 to determine whether the internal combustion engine 10 is operating in overrun mode. In such overrun mode, fuel is normally not injected into the combustion chamber 12 through the injection valves 18 . Therefore, the low-pressure fuel pump 32 can be switched off in a block 96 . This happens in block 96 . The quantity control valve 46 is then activated in block 98 in such a way that it is completely open, that is to say the high-pressure fuel line 24 is connected to the low-pressure fuel line 26 .

The pressure P1 is then measured in block 100 , as has already been described above. After a time interval t (block 102 ), the pressure P2 is measured in block 104 and the pressure drop between P1 and P2 is compared with a limit value PG in block 106 . If the pressure drop exceeds the limit value, a flag F is set in block 108 . In addition, a warning is generated in block 110 , which is displayed to the user of internal combustion engine 10 , that is to say to the driver in the case of a motor vehicle. In this way, he is informed of the leakage in the fuel system. Here, too, the method ends in end block 92 . With regard to a possible increase in pressure, what has been said above applies. In an exemplary embodiment not shown, in addition to setting the flag F, an entry is made in an error memory which, for. B. can be read by a diagnostic device in a workshop.

FIG. 4 shows a method likewise stored in the control and regulating device 56 as a computer program, with which the flag F is processed. After starting in block 112 , the position transmitter 58 is again queried in block 114 , which indicates the position or the movement of the ignition lock (not shown). If it is determined that the ignition is switched on and a start process is to be initiated (answer to the query in block 114 is "yes"), a query is made in block 116 as to whether the flag F is set. If this is the case, a control signal is emitted by the control and regulating device 56 , as a result of which the low-pressure fuel pump 32 cannot be switched on (block 118 ). This prevents z. B. due to a damaged seal 72 and / or 74 , which could damage the internal combustion engine 10 due to excessive oil dilution, the internal combustion engine 10 can be switched on at all. The method then ends in end block 120 . If the flag F is not set, this is recognized in block 116 and the usual starting sequence of the internal combustion engine 10 is initiated (block 122 ).

In Fig. 5, a second embodiment of an internal combustion engine 10 is shown. This does not work with gasoline direct injection (BDE), but with a manifold injection. Such parts which have functions equivalent to the parts of the first exemplary embodiment have the same reference numerals in FIG. 5 and are not explained again in detail.

The low-pressure fuel pump 32 , which is used in the internal combustion engine shown in FIG. 5, is generally not driven directly by the internal combustion engine 10 , but rather has an electric motor. The problem of leakage between the low-pressure fuel pump 32 and the engine 10 does not exist in this case. However, it is possible that the injection valve 18 is stuck and is not completely closed in the de-energized state, as is necessary per se. This means that when the internal combustion engine 10 is switched off, the fuel which is in the low-pressure fuel line 26 and is under pressure can escape through the injection valve 18 into the intake pipe 14 . When starting the internal combustion engine 10 subsequently, this can lead to problems. In order to also be able to recognize such a leakage due to a defective injection valve 18 , the method shown in FIGS. 3 and 4 is also used by the control and regulating device 56 in the internal combustion engine shown in FIG. 5.

It is understood that a prerequisite for the reliable implementation of the method shown in FIGS. 3 and 4 is the closed nature of the fuel system, ie that a backflow of fuel into the tank 28 must be prevented by suitable measures.

Claims (14)

1. A method for operating an internal combustion engine ( 10 ), in particular a motor vehicle, in which the fuel from a fuel pump ( 32 ) is fed into a fuel line ( 26 ), characterized in that in a state of the internal combustion engine ( 10 ) in which no The fuel is pumped by the fuel pump ( 32 ) and the fuel line ( 26 ) is part of a closed fuel system ( 20 , 22 , 24 , 26 ) ( 80 , 94 ), the fuel pressure in the closed fuel system ( 20 , 22 , 24 , 26 ) is detected ( 82 , 86 , 100 , 104 ) and when the pressure in the closed fuel system ( 20 , 22 , 24 , 26 ) drops by an amount (P1-P2) that is above a limit value (PG) ( 88 , 106 ), a report is made ( 90 , 108 ). 2. The method according to claim 1, characterized in that the message ( 90 , 108 ) only occurs when the amount (P1-P2) of the pressure drop within a certain period ( 84 , 102 ) exceeds the limit value (PG) ( 88 , 106 ). 3. The method according to any one of claims 1 or 2, characterized in that the pressure in the fuel system ( 20 , 22 , 24 , 26 ) during a period after switching off ( 80 ) of the internal combustion engine ( 10 ) is detected ( 82 , 86 , 100 , 104 ). 4. The method according to any one of the preceding claims, characterized in that during operation of the internal combustion engine ( 10 ), the fuel pump ( 32 ) in a suitable operating point ( 94 ) briefly switched off ( 96 ) and the pressure drop (P1-P2) in the closed fuel system ( 20 , 22 , 24 , 26 ) is recorded ( 100 , 104 ). 5. The method according to claim 4, characterized in that during a push phase ( 94 ) of the internal combustion engine ( 10 ) the fuel pump ( 32 ) is switched off ( 96 ) and the pressure in the closed fuel system ( 20-26 ) is detected ( 100 , 104 ) , 6. The method according to any one of the preceding claims, characterized in that the message comprises the setting of a certain flag state ( 90 , 108 ) and / or an entry in an error memory and / or the output of a warning and / or alarm message ( 110 ). 7. The method according to claim 6, characterized in that at the start ( 114 ) of the internal combustion engine ( 10 ) the error memory and / or the flag is read out ( 116 ) and when an entry is made in the error memory and / or in the corresponding flag state, a safety measure is carried out ( 118 ). , preferably a further starting of the internal combustion engine is prevented ( 118 ). 8. The method according to any one of the preceding claims, characterized in that when the fuel pump ( 32 ) does not deliver, a high pressure area ( 20 , 24 ) of the fuel system ( 20-26 ) with a low pressure area ( 26 ) of the fuel system ( 20-26 ) is connected so that the same pressure prevails in them and the pressure in the high pressure area ( 20 , 24 ) is recorded. 9. The method according to claim 8, characterized in that the high pressure region ( 20 , 24 ) is connected to the low pressure region ( 26 ) only when the temperature in the high pressure region ( 20 , 24 ) is so low that when the pressure in the High pressure area ( 20 , 24 ) to the pressure in the low pressure area ( 26 ) in the fuel, no vapor bubbles arise. 10. Computer program, characterized in that it is used for Implementation of the method according to one of claims 1 to 9 is suitable when running on a computer. 11. Computer program according to claim 10, characterized characterized it on a store, in particular on a flash memory. 12. Control and / or regulating device ( 56 ) for operating an internal combustion engine ( 10 ), in particular a motor vehicle, in which the fuel is conveyed by a fuel pump ( 32 ) into a fuel line ( 26 ), characterized in that it is used for controlling and / or or regulation of the method according to one of claims 1 to 9 is suitable. 13. Control and / or regulating device ( 56 ) according to claim 12, characterized in that it is provided with a computer program according to one of claims 8 or 11. 14. Internal combustion engine ( 10 ) with a fuel pump ( 32 ), which delivers fuel into a fuel line ( 26 ), and with a pressure sensor ( 54 ), which detects the pressure (P1, P2) in the fuel line ( 26 ), characterized in that that it comprises a control and / or regulating device ( 56 ) according to one of claims 12 or 13, which processes the signals of the pressure sensor ( 54 ).