Title of Invention

A METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE

Abstract

A process is proposed with which to operate an internal combustion engine (1) with a fuel-operated internal combustion motor (5) that enables differentiating between errors in the case of fuel feed. Thereby, fuel is fed under pressure to an internal combustion motor (5) through a fuel feed (10). Decompression speed is determined in the fuel feed (10) and an error IS inferred, subject to a comparison of the decompression speed with a pre-determined threshold value.

Full Text

Prqcess for Operating an Internal Combustion Engine Prior Art The invention emanates from a process with which to operate an internal combustion engine in accordance with the genre of the main claim. Processes for operating an internal combustion engine with a fuel-driven internal combustion motor are already established. In these cases, fuel is fed under pressure to the internal combustion motor via a fuel feed. The pressure in the fuel feed is, thereby, regulated to a specified value. Advantages of the Invention The advantage, on the other hand, with regard to the process in accordance with the invention with characteristics of the main claim is that a decompression speed is determined in the fuel feed and that an error is inferred, subject to a comparison of the decompression speed with a pre-determined threshold value. All leakages in a high-pressure circuit of the fuel feed can thus be detected in this manner and can be differentiated from other errors that may occur in engine fuel supply. Advantageous designs and improvements of the process specified in the main claim are possible through measures presented in the sub claims. It is particularly advantageous that in a situation where the actual value of the pressure does not reach the specified value during a pre-determined period, an error is detected and the decompression speed is determined in the fuel feed and That the type of error is determined, subject to a comparison of the decompression speed with the pre-determined threshold value. Various causes of errors for the offset between the actual value for the pressure and the specified value can be differentiated in this manner. This differentiation is, moreover, possible during operation of the internal combustion engine. Differentiation of the causes of errors allows, for example, for a simplified diagnosis in the workshop. It is particularly beneficial that dry-running operation measures are initiated subject to the type of error. Increased availability of the internal combustion engine can be achieved in this manner since the internal combustion engine can continue to be operated, depending upon the type of error. Another advantage results when a leak is recognised in the fuel feed in a case where the pre-determined threshold value is exceeded by the decompression speed. A leak in the fuel feed can thus be identified in an especially simple and safe manner. A further advantage results when, in the case of a leak identified in fuel supply, the internal combustion engine is switched off which ensures safe operation of the internal combustion engine. This is of significance particularly when the internal combustion engine is powering a motor vehicle. Driving safety is enhanced in this case. Another advantage emanates when in the case of a leak identified in fuel feed, a renewed start of the internal combustion engine is blocked. This prevents the internal combustion engine from being operated again before the error has been rectified. This also guarantees security during operation of the internal combustion engine. It is, furthermore, of advantage if an error is identified in the fuel supply in the case where the decompression speed falls short of the pre-determined threshold value. An error is detected in this manner that does not require the internal combustion engine to be switched off but instead enables continued operation which in turn increases availability of the internal combustion engine. Another advantage results when restriction of fuel quantities fed gets activated when an error is identified in the fuel supply which enables dry-running operation of the internal combustion engine with reduced engine output. Of further advantage is when in the event of an error that is identified irrespective of the type of error, the internal combustion engine is switched off even when the internal combustion engine is operated in no-load operation or under a small load that lies below the pre-determined load threshold. In this case one has to allow for the fact that in the case of no-load operation or a small load, further operation of the internal combustion engine is no longer practically possible when the actual value for the pressure in the fuel feed no longer matches up to the specified value. Another advantage emerges when a high-pressure circuit is separated from a low-pressure circuit of the fuel feed for determination of decompression speed and the decompression speed is determined in the high-pressure circuit. Decompression speed can be very simply determined in this manner. A further advantage is that a warning is signalled when an error is identified. The operator of the internal combustion engine, which in the case of a motor vehicle would be the driver, would thus be informed of the presence of an error in this manner. Drawing An exemplary embodiment of the invention is illustrated in the drawing and described in greater detail in the following description. Figure 1 illustrates a block diagram of an internal combustion engine with fuel feed to an internal combustion motor and Figure 2 is a flow chart for an exemplary execution of the process in accordance with the invention. Description of the Exemplary Embodiment In Figure 1, 1 designates an internal combustion engine that, for example, drives a motor vehicle. The internal combustion engine 1 comprises of a fuel-driven internal combustion motor 5 that could, for example, be designed as a spark-ignition motor or a diesel motor. The internal combustion engine 1 furthermore comprises of fuel supply 15 that provides fuel to the internal combustion motor 5 through a fuel feed 10. Fuel supply 15 comprises of a mechanically or electrically driven feed pump 30 that pumps fuel from a fuel tank 40 into the fuel feed 10 in the direction of the internal combustion motor 5. The feed pump 30 can, for example, be a mechanical pressure regulator that has a parallel connection with a pressure valve. A fuel filter can, moreover, be located at the fuel tank 40 outlet, which is not illustrated in Figure 1 for reasons of clarity. Fuel is first pumped from the fuel tank 40 into a low-pressure pipe 65. The feed pump 30 thereby creates, for example, a primary pressure of approximately 3.5 bar. Pressure that is to be set in the low-pressure pipe 65 can be implemented by using a pressure regulator, for example, that has a parallel connection with a pressure valve. The high-pressure pump 35 that is driven by the internal combustion motor 5 is thus energised in this manner. The function of the high-pressure pump 35 is to increase fuel pressure from the primary pressure of, for example, approximately 3.5 bar up to, for example, approximately 120 bar. The high-pressure pump 35 feeds fuel to the high-pressure pipe 70 in the direction of The internal combustion motor 5. A pressure control valve 45, which is actuated by an engine management system 80, is located in the high-pressure pipe 70 and is set according to the value specified for pressure in the high-pressure pipe 70. Unwanted excess pressure is relieved through a feedback path 85 in that the corresponding excess fuel is re-directed to the fuel tank 40 via the feedback path 85. Furthermore, a measuring device or any other device for setting the feed quantities and which can also take over pressure regulation can be integrated in to the high-pressure pump 35. In this case, the pressure control valve will be controlled or, if necessary, regulated in addition. A variant that does not have a pressure control valve can also be employed. In this example however, it is assumed that a pressure control valve 45 is used. A pressure sensor 50 is located in the high-pressure pipe 70 after the pressure control valve 45 in the direction of fuel flow. This pressure sensor 50 detects fuel pressure in the high-pressure pipe 70 and transmits same to the engine management system 80. The direction of fuel flow in Figure 1 is indicated by arrows in the individual pipes 65, 70, 85. A measuring device 55 is located after the pressure sensor 50 in the direction of fuel flow that, for example, comprises of one or several injection valves with which fuel quantities that are to be injected into a combustion chamber of an internal combustion motor 5 can be set in the manner known to experts. For this purpose, the measuring device 55 is likewise driven by the engine management system 80 in order to attain a pre-determined fuel quantity to be injected. Fuel injection can thereby take place directly into one or several cylinders of the internal combustion motor 5 or into an inlet manifold through which fuel together with air can be fed to the internal combustion motor 5. An injection pipe 75 is symbolically illustrated in Figure 1 through which fuel is fed from the measuring device 55 to the internal combustion motor 5. Furthermore, the diagram illustrates a signalling device 60 with a pilot lamp 90 that is controlled by the engine management system 80. As described, fuel supply 15 comprises of the feed pump 30, the fuel tank 40, the low-pressure pipe 65 and the high-pressure pump 35. A low-pressure circuit 25 comprises of the fuel tank 40, the feed pump 30 and the low-pressure pipe 65 as well as the pressure regulator that has a parallel connection and that is not illustrated. Unwanted excess pressure in the low-pressure pipe 65 can also be released, for example, through the feedback path 85, which is not illustrated in Figure 1 on grounds of clarity. Consequently fuel pressure in the low-pressure pipe 65 of the low-pressure circuit 25 is thus regulated by means of the pressure valve that is not illustrated here. A high-pressure circuit 20 comprises of the high-pressure pump 35, the high-pressure pipe 70, the pressure control valve 45, the pressure sensor 50 and the measuring device 55. In the high-pressure circuit 20, fuel pressure in the high-pressure pipe 70 is regulated using the pressure control valve 45 or the measuring device built into the high-pressure pump 35. Fuel feed 10 comprises of the low-pressure pipe 65, the high-pressure pump 35, the high-pressure pipe 70, the pressure control valve 45 and the pressure sensor 50. The invention now provides that the engine management system 80 determines the actual value of the fuel pressure in the high-pressure pipe 70 by means of the pressure sensor 50 and compares same with a pre-determined specified value of, for example, 120 bar. The engine management system 80 ascertains an error in the case of a positive offset being determined by the engine management system 80 in which the specified value is greater than the actual value and which, during a pre-determined period, will not be achieved by the actual value through corresponding control by the pressure control valve 45. The predetermined period is, thereby, for example, appropriately selected in such a manner that it can tolerate a temporary variation in the actual value on the one hand and on the other, detect the error early. An appropriate value for the predetermined time can, for example, be one second. The engine management system 80 can, thereby, indicate the error by activating the signalling device 60, in this example, by activating the pilot lamp 90. The signalling device 60 can, in addition or alternatively, also comprise of an acoustic warning device that gets activated when an error has been detected by the engine management system 80. Immediately after error detection or after a short time lag of, for example, a second, the engine management system 80 causes deactivation of injection through corresponding control of the measuring device 55 and/or of the injection valve(s). The injection valve(s) are locked for this purpose and the engine management system 80 subsequently attempts to adjust a maximum possible specified value for the fuel pressure through corresponding control of the pressure control valve 45 or of the measuring device in the high-pressure pump 35. This specified value can, for example, be 120 bar. In case the maximum possible specified value can not be adjusted, for example, within the predetermined period of, for example, one second, the engine management system 80 actuates fuel pressure adjustment in the high-pressure pipe 70 to the highest specified value achievable of below 120 bar in this example, through corresponding control of the control pressure valve 45. If this specified value is achieved by the actual value then the high-pressure circuit 20 is subsequently separated from the low-pressure circuit 25 in that the pressure control valve 45 and the measuring unit in the high-pressure pump 35 are closed by the engine management system 80 and the measuring device 55 and therewith the fuel injection are completely locked, whereby the measuring device 55 has already been locked beforehand. Decompression speed is subsequently determined by means of the pressure sensor's 50 signal. For this purpose, the engine management system 80 calculates the pressure modification per period from the pressure sensor's 50 signal. When pressure modification per period is negative, the same is the decompression speed i.e., when the pressure modification is negative. The decompression speed determined is compared by the engine management system 80 with a pre-determined threshold value. If the decompression speed lies above the pre-determined threshold value, then a leak in the high-pressure circuit 20, particularly in the high-pressure pipe 70, is to be assumed. The pre-determined threshold value can thereby be selected in such a manner that a natural pressure loss on grounds of tolerable leakages such as those that result, for example due to the material of the hiah-oressure pipe 70 and the assembly of the pressure control valve 45 as well as of the pressure sensor 50 and due to the integration of the high-pressure pump 35 and of the measuring device 55 (e.g., valve with constant leak in the reflux), result in a decompression speed that lies below the pre-determined threshold value and that, only in the case of a real leak in the high-pressure pipe 70, does the decompression speed exceed the pre-determined threshold value. The predetermined threshold value can thereby be correspondingly determined by test runs on an engine test stand. If an error in the high-pressure circuit 20 is thus detected as a type of error, particularly on grounds of a leak in the high-pressure pipe 70, then the engine management system 80 can deactivate the internal combustion engine 1 as a measure towards error management, for example, by locking the air supply and/or the ignition - the latter in the case of a spark ignition engine. In addition, the engine management system 80 can block a renewed start of the internal combustion engine 1 and also, in fact, for example, by likewise locking the air supply and/or ignition. If the decompression speed lies below the pre-determined threshold value, then a problem in fuel supply 15 is identified as a type of error, whereby the high-pressure circuit 20 is leak-proof and no danger is expected as a result of emerging fuel. The reason for the error in this case, for example, lies therein that the feed pump 30 or the high-pressure pump 35 can not be operated at full engine output. The internal combustion engine 1 can then at the least continue to be operated with reduced engine output. The determination of type of error described can take place within a short period, for example, within a few seconds, so that the internal combustion engine 1 and/or a motor vehicle, for example, driven by it, does not become substantially slower during this determination. Application of the process in accordance with the invention is, above all, expedient when the internal combustion engine 1 is in an operating range with medium or high load. If the positive offset described occurs for at least the pre-determined period when in small load or no-load operation then further operation of the internal combustion engine 1 is usually no longer possible and is therefore, independent of the type of error, terminated by the engine management system 80 in the, for example, manner described. The load can thereby be determined by the engine management system 80 in the manner known to experts and not illustrated in Figure 1, subject to an air-mass flow fed to the internal combustion motor 5, subject to an accelerator pedal position in the case of a motor vehicle, subject to a position of a correcting element, a butterfly valve, for example, with which to influence air supply, subject to the fuel injection quantity or suchlike. A corresponding load signal is then compared with a pre-determined load threshold value in order to differentiate a small load or a no-load operation from a medium or higher load. The predetermined load threshold can, thereby, be appropriately selected in such a manner at an engine test stand that load values below the pre-determined load threshold value in the case of a positive offset for at least the pre-determined period no longer result in an expedient operation of the internal combustion engine 1 and the internal combustion engine 1 can, however, be smoothly operated with load values above the pre-determined load threshold values even in a case of positive offset for at least the pre-determined period. The process in accordance with the invention is explained in greater detail by means of a flow chart in Figure 2. After starting the program, the engine management system 80 determines the offset between the specified value and the actual value of fuel pressure in the high-pressure pipe 70 in program point 100. Furthermore, a time variable is set at zero. The next point moved to is program point 105. At program point 105, the engine management system 80 verifies whether a positive offset is present i.e. whether the specified value is greater than the actual value. If this is the case, the next step is program point 110, if not, then program point 100 is returned to. The time variable in the engine management system 80 is increased by a predetermined incremental value, for example, by 10 ms in program point 110. The next point moved to is program point 115. In program point 115, the engine management system 80 verifies whether the time variable has achieved the pre-determined period or has exceeded the same. If this is the case then the next step is program point 150, if not then program point 105 is returned to. At program point 150, the engine management system 80 checks whether the load determined lies below the pre-determined load threshold value. If this is the case, then the next step is program point 140, if not, then program point 120 is moved to. At program point 120, the engine management system 80 activates the pilot lamp 90 of the signalling device 60 and therewith indicates that an error has been detected. Furthermore, the engine management system 80 activates locking of the measuring device 55 and therewith fuel injection. Program point 125 is the next point moved to. At program point 125, the engine management system 80 triggers adjustment of the actual value of fuel pressure in the high-pressure pipe 70 to the maximum possible and/or the highest achievable specified value by evaluating the signal supplied by the pressure sensor 50 and activating the pressure control valve 45. The next point moved to is program point 130. At program point 130, the engine management system 80 triggers locking of the pressure control valve 45 and therewith separation of the high-pressure circuit 20 from the low-pressure circuit 25. Subsequently the engine management system 80 determines the decompression speed i.e. the fuel's pressure loss per period In the high-pressure pipe 70 by means of the pressure sensor's 50 signal, Program point 135 is the subsequent step. At program point 135 the engine management system 80 checks whether decompression speed lies above the pre-determined threshold value. If this is the case, then the next step is program point 140, if not then program point 145 is moved to. At program point 140, the engine management system 80 has detected a leak in the fuel feed 10 as a type of error and triggers a reaction to this type of error which is deactivation of the internal combustion engine 1 and/or interruption of air supply and/or ignition. At program point 140, the engine management system 80, in addition to or alternatively, also blocks a renewed start of the internal combustion engine 1. The program is subsequently exited from. At program point 145, the engine management system 80 detects an error in fuel supply 15 as a type of error and triggers a reaction to this type of error which is re-opening the measuring device 55 and the pressure control valve 45 and therewith enables further operation of the internal combustion engine 1 with at least reduced engine output since the original specified value to be set is not achieved by the actual value of fuel pressure in the high-pressure pipe 70 due to persistent positive offset. The engine management system 80 can thereby activate the measuring device 55 in such a manner that fuel injection is slowly increased in line with converting the driver's requirement, which corresponds to activating the accelerator pedal of the motor vehicle. In addition to this, a limit on the quantity of fuel injected is activated by the engine management system 80 in order to prevent unnecessary fuel consumption and therewith also prevent unnecessary deterioration of the exhaust gas and to implement dry-running operations. The program is subsequently exited from. Particularly in the case of systems with injectors that do not leak e.g., piezo injectors in diesel or fuel direct injection valves in the measuring device 55, decompression in the high-pressure pipe 70 in the case of a separated high-pressure circuit 20 and low-pressure circuit 25 is comparably slow since there is no leak in the measuring device 55. Additional leakage in the high-pressure pipe 70 then results in significantly faster decompression and can thus be easily identified with the help of an appropriately established, pre-determined threshold value for the decompression speed. In systems with other measuring device 55 (e.g., magnet valve injectors in the case of diesel) due to the leakage present in the injectors there, decompression in the high-pressure pipe 70 in the case of a separated high-pressure circuit 20 and low-pressure circuit 25 is less slow when compared with decompression in the case of additional leakage in the high-pressure pipe 70. Therefore, in systems that have magnet valve injectors, the additional leakage in the high-pressure pipe 70 is less easy to differentiate from the already present injector leakage i.e. the pre-determined threshold value for the decompression speed must be determined with more care in this case. Apart from this, when selecting this threshold value, it should be taken into consideration that leakage of the magnet valve injectors will increase during the service life of the magnet valve injectors and, moreover, distribution of leakage of the various magnet valve injectors occurs. The tolerance range for the selection of the pre-determined threshold value for the decompression speed consequently turns out to be less than when piezo injectors are used. Leakages in the high-pressure circuit 20 can be differentiated from other errors by using the process in accordance with the invention. These leakages can, for example, be caused by a leak in the high-pressure pipe 70 or a leak in one or several injection valves of the measuring device 55. Leakages due to a defective injection valve emerge, for example, when the injection valve can no longer be closed due to a deposit of dirt particles. Particularly after switching off the internal combustion engine 1, the pressure in the fuel feed 10 is reduced even by Minimal leakage in the high-pressure circuit 20, particularly in one or several corresponding dirty injection valves. When an injection valve can thus no longer be closed, for example, due to dirt particles, then fuel will stream into the corresponding cylinder of the internal combustion engine 1 due to continuous pressure in the fuel feed 10 and/or due to gravitation. This can result in damage to the internal combustion motor 5 when next starting up the internal combustion engine 1. This can be prevented, as already described, by blocking a renewed start of the internal combustion engine 1. The process in accordance with the invention can be executed with closed injection valves to determine the decompression speed in fuel feed 10 in accordance with the exemplary embodiments described above even after switching off the internal combustion engine 1. Fuel fed to the internal combustion motor 5 is thus blocked as long as the injection valves are completely leak-proof. In this case, fuel fed to the internal combustion motor 5 does not reach the combustion chamber. The process in accordance with the invention can also be used in the framework of a so-called shed test in the manner described. Emissions of fuel vapours through the fuel tank 40 and its components are measured with the help of such shed tests. Hot fuelling equipment thereby enables testing of fuel feed 10 during fuelling of various fuel types and under various simulated conditions. Using the process in accordance with the invention, during the shed test in the described manner, conclusions can be drawn with regard to leakages in the high-pressure circuit 20 and/or in the fuel feed 10 and with regard to errors in fuel supply 15. Claims 1. Process with which to operate an internal combustion engine (1) with a fuel-operated internal combustion motor (5), in which fuel is fed under pressure to the internal combustion motor (5) through a fuel feed (10), characterised in that a decompression speed is determined in the fuel feed (10) and that, subject to a comparison of the decompression speed with the pre-determined threshold value, a conclusion is made with regard to an error. 2. Process according to Claim 1, characterised in that the fuel pressure is regulated to a specified value so that in the event that the actual value for the pressure does not reach the specified value during a pre determined period, an error is detected and the decompression speed in the fuel feed (10) is determined and that the type of error is determined, subject to a comparison of the decompression speed with the pre-determined threshold value. 3. Process according to Claim 2, characterised in that a dry-running operation measure is initiated subject to the type of error. 4. Process according to one of the previous Claims, characterised in that a leak is identified in the fuel feed (10) in the case where the pre determined threshold value is exceeded by the decompression speed. 5. Process according to Claim 4, characterised in that the internal combustion engine (1) is switched off if a leak is identified in the fuel feed (10). 6. Process according to Claim 4 or 5, characterised in that renewed start of the internal combustion engine (1) is blocked if a leak is identified in the fuel feed (10). 7. Process according to one of the previous claims, characterised in that an error is identified in the fuel supply (15) in the case where the decompression speed falls short of the pre-determined threshold value. 8. Process according to Claim 7, characterised in that restriction of fuel quantities supplied is activated when an error is identified in the fuel supply (15). 9. Process according to one of the preceding claims, characterised in that the internal combustion engine (1) can even be switched off in the case of an identified error independent of the type of error if the internal combustion engine (1) is operated in no-load operation or with a small load below a pre-determined load threshold value. 10. Process according to one of the previous claims, characterised in that, in order to determine decompression speed, a high-pressure circuit (20) is separated from a low-pressure circuit (25) of the fuel feed (10) and the decompression speed in the high-pressure circuit (20) is determined. 11. Process according to one of the previous claims, characterised in that a warning is signalled when an error is detected.

Documents:

1550-chenp-2006 complete specification as granted.pdf

1550-CHENP-2006 ABSTRACT.pdf

1550-CHENP-2006 CLAIMS.pdf

1550-CHENP-2006 CORRESPONDENCE OTHERS.pdf

1550-CHENP-2006 CORRESPONDENCE PO.pdf

1550-CHENP-2006 FORM-18.pdf

1550-CHENP-2006 FORM-2.pdf

1550-chenp-2006 correspondence others-13-07-2009.pdf

1550-chenp-2006 form-26-13-07-2009.pdf

1550-chenp-2006 form3-13-07-2009.pdf

1550-chenp-2006-abstract.pdf

1550-chenp-2006-claims.pdf

1550-chenp-2006-correspondnece-others.pdf

1550-chenp-2006-description(complete).pdf

1550-chenp-2006-drawings.pdf

1550-chenp-2006-form 1.pdf

1550-chenp-2006-form 26.pdf

1550-chenp-2006-form 3.pdf

1550-chenp-2006-form 5.pdf

1550-chenp-2006-pct.pdf

EXAMINATION REPORT REPLY.PDF