WO2010003780A1 - Method and diagnostic device for detecting a malfunction of an injection system - Google Patents

Abstract

In order to prevent in particular the arbitrary and uneconomical replacement of components of an injection system of an internal combustion engine in the event of a failure of the injection system, according to the invention a method for detecting a malfunction of an injection system of an internal combustion engine, particularly of a motor vehicle, is proposed, wherein for the detection of the malfunction in the injection system a regular injection quantity of a fuel is increased at least temporarily using an additional injection quantity of fuel, a measurement value of an exhaust gas temperature and/or a rise in the exhaust gas temperature are determined based on an increase in the injection quantity, and the measurement value determined is compared to an expected value.

Description

description

Method and diagnostic device for detecting a malfunction in an injection system

On the one hand, the invention relates to a method for detecting a malfunction in an injection system of an internal combustion engine, in particular of a motor vehicle. On the other hand, the invention relates to a fault diagnosis device for detecting a malfunction in an injection system of an internal combustion engine, in particular of a motor vehicle, in which the fault diagnosis device can be connected to a data peripheral of the motor vehicle by means of suitable connection means.

In particular, methods for detecting a malfunction in an injection system of an internal combustion engine, in particular a self-igniting internal combustion engine, allow it only in connection with on-board diagnostic systems of a motor vehicle under dynamic operating conditions only to a limited extent, for example with regard to an electrical short circuit Determine the cause of an error in an injection system without negatively influencing the driving behavior, the exhaust emissions and / or the fuel consumption. Moreover, it is not possible with the known methods to determine an exact cause of failure in an injection system. Thus, because of a lack of knowledge about an exact cause of the error, it is often necessary to exchange components or too many components, in particular of an injection system of an internal combustion engine. For example, often all injectors of an injection system are exchanged, although the actual cause of the error can only be found in one of the injectors. Such a differentiated error However, the search is not possible with currently available methods.

Further causes of error, which so far can not be detected sufficiently well by means of a suitable detection method, are, for example, the wear or contamination of injectors, so that by means of the injectors only an injection quantity differing from a regular injection quantity can be provided. Often such errors lead to malfunction of an internal combustion engine of a motor vehicle, such as a non-circular engine run, critical smoke and / or critical power loss, the causes of such errors can be limited so far only speculative or not at all. This is particularly disadvantageous in particular in self-igniting internal combustion engines with particle filters, which can lead to an extreme deterioration of an initiation of a particle filter regeneration. There is also the danger of an overload of the particulate filter, so that it can also lead to an uncontrolled self-generation. As a result, among other components of an exhaust system of an internal combustion engine, for example, by extremely high exhaust gas temperatures, damaged or even destroyed.

It is an object of the present invention to avoid related disadvantages with regard to fault detection on an internal combustion engine, in particular on a self-igniting internal combustion engine, of a motor vehicle.

The object of the invention is achieved by a method for detecting a malfunction in an injection system of an internal combustion engine, in particular of a motor vehicle, in which a regular injection quantity of a fuel by means of a for detecting the malfunction in the injection system additional or reduced injection amount of fuel at least temporarily increases or decreases, a measured value of an exhaust gas temperature and / or an increase / decrease of the exhaust gas temperature due to the injection quantity increase or - determined reduction and the determined measured value is compared with an expected value.

Advantageously, a malfunction in the injection system can be detected when the internal combustion engine an additional or reduced injection amount of fuel is supplied, with an increase in injection quantity within an exhaust system, in particular within an oxidation catalyst, the internal combustion engine causes an exhaust gas temperature rise. If a measured value is determined for this exhaust-gas temperature rise and compared with an expected value which is to be expected with regard to the additional injection quantity of fuel, it is possible to draw conclusions about the actual amount of fuel injected. As a result of this, a cause of the fault which causes the malfunction on the injection system can be detected much more precisely for the first time than was previously possible.

Thus, based on the method according to the invention, an abnormal injection quantity of fuel can be detected particularly advantageously by means of an evaluation of the injection-related increase in a measured exhaust gas temperature, which can be measured behind, in particular, a diesel oxidation catalytic converter of a diesel internal combustion engine, and the relevant expectation value. In this case, it is then possible to further infer a malfunction in the injection system of the internal combustion engine.

An already suitable measured value, which can be used as a sufficiently accurate actual value for comparison with an expected value, can either be a measured value of a single exhaust-gas temperature measurement as a result of an increase in injection quantity be. Cumulatively or alternatively, a difference value with regard to an exhaust-gas temperature rise due to an increase in injection quantity can also be related to a calculated expected value in this regard.

The term "fuel injection system" in the present case describes any components, in particular fuel-carrying components of an internal combustion engine, which are required in order to be able to supply the fuel to individual combustion chambers of the internal combustion engine.

It is advantageous if the expected value is calculated on the basis of an additional injection quantity of fuel supplied to the combustion chambers of the internal combustion engine, in particular with regard to the injection quantity increase.

It is understood that the internal combustion engine, the additional injection amount of fuel can be supplied in different ways, such as all injectors of an injection system at the same time. A particularly advantageous variant of the method provides that the injection quantity of the fuel at each of the injection devices, such as at an injector of the injection system, is incrementally increased or reduced. For example, due to such a stepwise variation of the additional injection quantity at each injector, a multiplicity of different measurements can take place one behind the other, so that faulty components of the injection system can be delimited even more precisely by means of a series of measurements that can be developed from this.

In order to achieve a reliable and particularly defined increase in injection quantity, it is advantageous if an additional injection quantity of the fuel is injected by means of a post-fuel injection. Such post fuel injections are already well known in the art and also well controlled. For example, such a post-injection fuel injection is used to achieve an increase in exhaust gas temperature, for example for regeneration of a catalytic converter. Such a post-fuel injection is also known, for example, from the European patent specification EP 1 252 427 B1, in which an injected fuel mass is regulated by increasing an engine load, without influencing vehicle operation, so that a total exhaust-gas temperature increase that is neutral in terms of the engine can be achieved. However, in this case no malfunction can be detected on a component of an injection system of an internal combustion engine.

The exhaust gas temperature and / or the increase in the exhaust gas temperature can be determined particularly advantageously in terms of design by means of an exothermic reaction with respect to an oxidation catalyst, in particular with respect to a diesel oxidation catalyst.

In particular, the present method can be used particularly advantageously if an abnormal injection quantity of a fuel is to be detected.

The method can advantageously be further developed if a faulty injection quantity, in particular an insufficient injection quantity, is detected. By way of example, an injection quantity that is too low or fuel injection that has not been carried out can be detected at one of the injectors if it is possible to determine an excessively low or no measurable exhaust-gas temperature increase in the exhaust system with regard to a sequential post-injection of fuel. An insufficient injection quantity may result, for example, if an injector is dirty. It is also advantageous if an injection quantity that is too high can be detected. For example, this may be the case at an injector of an injection system when the injector already has critical signs of wear. Such wear can be attributed to excessive exhaust gas temperature rise within the exhaust system due to an abnormally increased injection quantity. In particular, it is advantageous if, in this connection, each individual one of the injection devices or each individual one of the injectors is checked.

If, on the other hand, an exhaust-gas temperature rise is too low for all injectors, it can be concluded that there is a problem of pressure build-up within the injection system. For example, the causes of this can be a leakage in fuel-carrying lines or components and / or a reduced efficiency of a high-pressure pump of the injection system. In particular, if exhaust gas temperature rise is too low for all injectors, it can be assumed that only a single injector is unlikely to operate improperly. Especially in this context, it is advantageous if a faulty pressure build-up within the fuel supply of the injection system is detected.

In addition, a faulty rail pressure within the fuel supply position of the injection liner can also be determined if an exhaust gas temperature rise is too high with respect to all individually tested injectors. It can be assumed that there is an overall high rail pressure. This may indicate a problem with a volume control valve. If necessary, this is too far open, o- if any, a pressure control valve may be too closed. If, in particular, an ignition system of a gasoline-fueled internal combustion engine is operated with targeted spark ignitions, an exhaust gas temperature increase within the exhaust gas system can likewise be achieved cumulatively or alternatively to the fuel post-injection.

In addition, an increase in injection quantity and, as a result, an exhaust-gas temperature increase can also be achieved by means of a higher load requirement on the internal combustion engine. This can be achieved without great effort, for example, by switching in particular electrical consumers, so that the load with regard to the internal combustion engine can be increased in terms of process technology in a particularly simple manner in order to be able to provide sufficiently additional electrical energy for the electrical consumers. Therefore, a further advantageous variant of the method provides that electrical consumers, in particular of a motor vehicle, are connected in order to be able to increase an injection quantity of the internal combustion engine.

It goes without saying that the method on which the invention is based can be carried out on-board a vehicle, in which case appropriate hardware and / or software systems for carrying out the method in the vehicle periphery can be provided and permanently carried. For example, the method according to the invention could be carried out during relatively uniform driving conditions, for example during a sufficiently long idling or coasting phase of an internal combustion engine.

However, if such hardware and / or software systems are not desired on-board a vehicle, for example for cost reasons, the present method can also be carried out only during maintenance or repair work in a workshop with an external fault diagnosis device. In particular in this context, the object of the invention is düng also solved by a fault diagnosis device for detecting a malfunction in an injection system of an internal combustion engine, in particular a motor vehicle, in which the fault diagnosis device can be connected by means of suitable connection means to a data peripheral of the motor vehicle, wherein the fault diagnosis device is characterized in that it means for Activation and / or deactivation of individual or all injection devices of an injection system of an internal combustion engine comprises.

In addition, in order to be able to easily carry out the above-explained method on the fault diagnosis device, it is advantageous if the fault diagnosis device comprises means for comparing a measured value of an exhaust gas temperature increase due to an increase in injection quantity of a fuel with a respective expected value of a predicted exhaust gas temperature rise.

In addition, if the fault diagnosis device comprises means for measuring an exothermic reaction in an oxidation catalytic converter, on the one hand, procedurally and on the other hand structurally accurate measured values with regard to an achieved exhaust gas temperature difference can be determined particularly easily. Thus, the expected exothermic reactions, preferably by means of suitable exhaust gas temperature sensors directly on the oxidation catalyst can be monitored.

In order for measured values determined and / or other calculated measured values or related measured data to be available for evaluation, for subsequent checking and / or further processing, it is advantageous if the fault diagnosis device also has means for evaluating and / or storing of determined measurement data with regard to the method explained here. Thus, targeted repair measures can also be made at a later date or visit to the workshop based on stored measurement data targeted.

In order to be able to obtain reliable evaluation results with regard to the method described above, it is advantageous if at least the initial conditions described below can be fulfilled on an internal combustion engine or on a motor vehicle. On the one hand, an internal combustion engine must still be able to be started and operated, for example during standstill operation of a motor vehicle during a workshop visit. In addition, a sufficient Raildruckaufbau should still be possible on an injection system of the internal combustion engine, in particular should not be present critical leaks in fuel-carrying components of the injection system. In addition, the internal combustion engine would ideally have to be able to be operated at low load or at low torque in a stationary operating state. Furthermore, it is advantageous if a low-consumption operating mode can be selected on the internal combustion engine in which, if possible, only a constant main injection is active. Also, in this context, a low idle speed, such as about 700 U / min, could be set with respect to the engine. Components, in particular of a fuel intake tract and of an exhaust system of the internal combustion engine, should be able to operate well, ie at least not be defective. In addition, in order to obtain sufficiently accurate measurement results, it is expedient if the exhaust gas temperature has already reached or exceeded an activation temperature of an oxidation catalyst and has at least approximately reached a required conversion rate.

Further advantages, objects and features of the present invention will become more apparent from the following description Explanation explains, in which an example of a self-igniting internal combustion engine is shown with an injection system and an exhaust system.

It shows

the single FIGURE schematically shows a view of a self-igniting internal combustion engine with a downstream exhaust system.

With regard to the single figure, an internal combustion engine / exhaust unit 1 is schematically illustrated with an internal combustion engine 2 and with an exhaust system 3 downstream of the internal combustion engine 2. The internal combustion engine 2 is a self-igniting internal combustion engine 4, which is operated by means of diesel fuel.

The self-igniting internal combustion engine 4 includes an injection system 5 for the diesel fuel, which can be injected into the respective combustion chamber 8 of the self-igniting internal combustion engine 4 by means of injection devices 6, which are shown as an example injector 7 in this illustration. The injection system 5 also includes, for example, injection relays 9, by means of which injection of the diesel fuel can be regulated, in particular a regular injection quantity for the proper operation of the self-igniting internal combustion engine 4 and as an additional injection quantity for an injection quantity increase.

The exhaust system 3 comprises an exhaust manifold 10, by means of which the exhaust system 3 is flanged to the self-igniting internal combustion engine 4. Furthermore, the exhaust system 3 according to this illustration comprises an exhaust gas turbine 11, a diesel oxidation catalyst 12, a particulate filter 13 and a muffler 14. In front of the diesel oxidation catalyst 12 is a first exhaust gas temperature sensor 15 and behind the Diesel oxidation catalyst 12 is placed another exhaust temperature sensor 16, by means of which an exhaust gas temperature increase can be measured, which can be caused by exothermic reactions within the diesel oxidation catalyst 12 due to injection quantity increases of the diesel fuel. The particle filter 13 is also equipped with a pressure sensor 17, by means of which a pressure difference between a particle filter inlet 18 and a particle filter outlet 19 can be measured.

In order to be able to recognize a malfunction in the injection system 5 more accurately than heretofore, an additional injection quantity of diesel fuel is injected into the combustion chambers 8 to a regular injection quantity of diesel fuel, resulting in a defined increase in injection quantity. This increase in injection quantity results in an increased exothermic reaction within the diesel oxidation catalytic converter, as a result of which an exhaust gas temperature increase, in particular at the further exhaust gas temperature sensor 16, can be determined. This determined exhaust gas temperature rise is compared with a calculated expected value. From this targeted conclusions can be obtained on the cause of the malfunction of the injection system 5, whereby an exchange of defective components of the injection system 5 can be made more targeted than before. It should also be noted at this point that the other variants of the method explained above can be additionally performed if an improved diagnosis can be achieved as a result.

All disclosed in the application documents features are claimed as essential to the invention, provided they are new individually or in combination over the prior art.

Claims

claims 1. A method for detecting a malfunction in an injection system (5) of an internal combustion engine (2, 4) in particular of a motor vehicle, characterized in that for detecting the malfunction in the injection system (5) a regular injection amount of fuel by means of an additional or Reduced injection amount of fuel at least temporarily increased or decreased, a measured value of an exhaust gas temperature and / or an increase / decrease of the exhaust gas temperature determined as a result of the injection quantity increase or injection quantity reduction and the determined measured value is compared with an expectation value. 2. The method according to claim 1, characterized in that the expected value is calculated on the basis of an additional or reduced injection quantity of fuel. 3. The method according to claim 1 or 2, characterized in that the injection quantity of the fuel at each of the injection devices (6), such as at an injector (7) of the injection system (5), increased seguenzweise or reduced. 4. The method according to any one of claims 1 to 3, characterized in that an additional injection quantity of the fuel is injected by means of a fuel post-injection. 5. The method according to any one of claims 1 to 4, characterized in that the exhaust gas temperature and / or the rise / fall of the exhaust gas temperature are determined by means of an exothermic reaction with respect to an oxidation catalyst, in particular with regard to a diesel oxidation catalyst. 6. The method according to any one of claims 1 to 5, characterized in that an abnormal or defective injection quantity of a fuel is detected. 7. The method according to any one of claims 1 to 6, characterized in that too high or too low injection quantity is detected. 8. The method according to any one of claims 1 to 7, characterized in that a faulty pressure build-up within the fuel supply position of the injection system (5) is detected. 9. The method according to any one of claims 1 to 8, characterized in that a faulty rail pressure within the fuel supply position of the injection system (5) is determined. 10. The method according to any one of claims 1 to 9, characterized in that a delayed ignition timing is set to the internal combustion engine (2). 11. The method according to any one of claims 1 to 10, characterized in that electrical consumers in particular of a motor vehicle are connected in order to increase an injection quantity to the internal combustion engine (2) can. 12. Fault diagnosis device for detecting a malfunction in an injection system (5) of an internal combustion engine (2) in particular of a motor vehicle, in which the fault diagnosis device can be connected by means of suitable connection means to a data peripheral of the motor vehicle, characterized by Means for activating and / or deactivating individual or all injection devices (6) of an injection system (5) of an internal combustion engine (2). 13. Fault diagnostic device according to claim 12, characterized by Means for comparing a measured value of an actual exhaust gas temperature increase or exhaust gas temperature drop due to an injection quantity increase or reduction of a fuel with a respective expected value of a predicted exhaust gas temperature rise. 14. Fault diagnosis apparatus according to claim 12 or 13, characterized by Means for measuring an exothermic reaction in an oxidation catalyst (12). 15. Fault diagnosis device according to one of claims 12 to 4, characterized by means for evaluating and / or for storing determined measured data with regard to the method according to one of claims 1 to 11.