METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE

Description

[0001] The invention relates to a method for operating an internal combustion engine with an exhaust line that conducts exhaust gas from the internal combustion engine via an exhaust gas turbocharger to the environment. In particular, the method can be used in motor vehicles to control the operation of the internal combustion engine. Furthermore, the method can determine an exhaust backpressure in the exhaust line and, based on the change in the exhaust backpressure, determine the soot loading of an exhaust gas treatment component (e.g., a particulate filter).

[0002] In internal combustion engines with exhaust turbochargers, a first section of the exhaust line is located downstream of the internal combustion engine and upstream of the exhaust turbocharger, and a second section of the exhaust line is located downstream of the exhaust turbocharger. In internal combustion engines, a pressure sensor can be arranged in the first section, e.g., in an exhaust manifold of the internal combustion engine.

[0003] Furthermore, the internal combustion engine is controlled during operation. In particular, the following controls are implemented: Control of the boost pressure for the internal combustion engine; Control of a gas exchange model (i.e., the supply of fresh air, exhaust gas, and fuel for combustion in the combustion chambers of the internal combustion engine, as well as the removal of exhaust gas from the combustion chambers; furthermore, the ignition timing, the valve opening timing, etc.) of the internal combustion engine; Diagnosis of exhaust gas turbocharger overspeed; Control of the regeneration of an exhaust gas treatment component arranged in the second section. These controls are particularly dependent on an exhaust backpressure present in the second section of the exhaust line downstream of the exhaust gas turbocharger.

[0004] However, installing a pressure sensor in this difficult-to-access section of the exhaust line is complex and expensive. Therefore, prior art approaches exist to estimate the exhaust backpressure in the second section.

[0005] EP 1 491 747 A2 discloses a method by which exhaust gas back pressure can be calculated.

[0006] It is known from FR 2 899 278 A1 and DE 10 2004 040 924 A1 that a pressure downstream of a turbocharger can be determined from the measured values of a sensor arranged between the internal combustion engine and the turbocharger. It is also known that the pressure values at these two locations can be very similar at certain operating points of the internal combustion engine, where only a very slight expansion of the exhaust gas via the turbocharger occurs.

[0007] From FR 2 923 537 A1 a method is known by which the pressure downstream of a turbocharger can be determined.

[0008] These estimation or calculation methods are too imprecise for controlling the internal combustion engine, at least in some operating situations.

[0009] The object of the present invention is to at least partially solve the problems cited with reference to the prior art. In particular, a method is to be provided that enables the most accurate determination possible of the exhaust backpressure present in a second section, i.e., downstream of an exhaust gas turbocharger. The exhaust backpressure thus determined can be used for the various control systems of the internal combustion engine, thus enabling effective operation of the internal combustion engine.

[0010] A method having the features according to claim 1 contributes to achieving these objectives. Advantageous further developments are the subject of the dependent claims. The features listed individually in the claims can be combined with one another in a technologically expedient manner and can be supplemented by explanatory facts from the description and / or details from the figures, whereby further embodiments of the invention are shown. The scope of protection is defined by the appended claims.

[0011] A method for operating an internal combustion engine having an exhaust line is proposed. The exhaust line conducts exhaust gas from the internal combustion engine via an exhaust gas turbocharger (e.g., to an environment, optionally at least partially back to the internal combustion engine via an exhaust gas recirculation line). By measuring a first pressure in a first section of the exhaust line downstream of the internal combustion engine and upstream of the exhaust gas turbocharger (e.g., by a pressure sensor, i.e., by a first sensor), a second pressure is determined in a second section of the exhaust line downstream of the exhaust gas turbocharger. The determination of the second pressure is derived from the condition or relationship according to which the first pressure (substantially) corresponds to the second pressure at predetermined operating points of the internal combustion engine and predetermined crankshaft angular positions.

[0012] In other words, the procedure could be formulated (alternatively or in addition) as follows: 1. Measuring at least the first pressure and the second pressure during several operating points of the internal combustion engine and several crankshaft angle positions of the internal combustion engine. 2. Identifying at least one operating point and one crankshaft angle position of the internal combustion engine at which the first pressure and the second pressure substantially coincide, and establishing this crankshaft angle position or this operating point as the control base. 3. Controlling the operation of the internal combustion engine based on measured first pressures and depending on second pressures specified by the control base.

[0013] Steps 1 and 2 are carried out (once) in an initiation process (e.g. on a test bench), while step 3 is carried out during (driving) operation of the internal combustion engine in the motor vehicle.

[0014] The identification of "matching" pressures can be achieved by ensuring that a specified maximum deviation, which results from a comparison of the first pressure and the second pressure, is not exceeded. The specified maximum deviation can be, for example, 2%, 1%, or even 0.5%.

[0015] The control basis is defined in the form of a characteristic curve, whereby the identified crankshaft angle positions and operating points are at least one support or reference value.

[0016] Before step 3, any (pressure) sensor in the second section is removed. It is possible that a sensor for measuring the first pressure is only provided and installed in the first section.

[0017] The second section extends from the exhaust turbocharger further downstream, in particular along the main exhaust system to the surrounding area. In particular, at least one exhaust gas treatment component (particulate filter, catalyst, flow control, injection device, heating device, etc.) is arranged in the second section.

[0018] The second pressure is to be determined between the exhaust gas turbocharger and an exhaust gas treatment component located closest downstream of the exhaust gas turbocharger.

[0019] The first pressure in the first section changes depending on the respective operating point and the crankshaft angle position (at the respective operating point). Depending on the crankshaft angle position, the exhaust valves of the combustion chambers are actuated, allowing exhaust gas from the combustion chambers to enter the first section. It has now been determined that at specific operating points to be determined and for specific crankshaft angle positions that then exist, the first pressure upstream of the exhaust gas turbocharger is equal to the second pressure downstream of the exhaust gas turbocharger.

[0020] It has also been established that this point in time can be determined very precisely in the first course of the first pressure, so that the second pressure can be derived with high accuracy from the first course of the first pressure.

[0021] It is also known that the second pressure has a certain second curve depending on the curve of the measured first pressure.

[0022] From these conditions, it was deduced that the second profile of the second pressure can be determined as a function of the first profile of the measured first pressure. Furthermore, based on a change in the measured first pressure at the specific operating points and at the specific crankshaft angle positions, a change in the second pressure and thus a currently existing exhaust backpressure in the second section of the exhaust line can be determined.

[0023] The exhaust back pressure determined (precisely) in this way can be used to control, for example, the internal combustion engine. Furthermore, a change in the exhaust back pressure can be determined via the change in the measured first pressure and thus the determined second pressure. The change in the exhaust back pressure is caused in particular by an increasing loading of, for example, an exhaust treatment component arranged in the second section with soot. The state of the exhaust treatment component (i.e., for example, a pressure loss across the exhaust treatment component) can be determined via the determined change in the exhaust back pressure. Preferably, a time for regeneration of the exhaust treatment component can be determined. Furthermore, the effectiveness of the regeneration can also be checked via the currently existing exhaust back pressure.

[0024] In particular, it is proposed that the internal combustion engine be operated on a test bench in a test bench procedure to determine the operating points and the crankshaft angle positions.

[0025] In a test bench procedure, a second (pressure) sensor can be arranged in the second section and thus the second pressure and the second curve in the second

[0026] Section can be measured. In the test bench procedure, the operating points and crank angle positions at which the magnitudes of the first pressure and the second pressure are equal can be determined for each configuration of the internal combustion engine, exhaust line, exhaust treatment components, and drive train (e.g., transmission, additional drive units, etc.).

[0027] The operating points and crank angle positions thus determined in the test bench procedure can then be used in the procedure already described, so that the internal combustion engine of the same type (as the configuration used in the test bench procedure) produced in large quantities can be used without a second sensor.

[0028] The operating point of the internal combustion engine depends in particular on the currently available operating parameters of the internal combustion engine (ignition timing, injection quantity, compression ratio, etc.), an exhaust gas mass flow, a position of an actuator of the turbocharger and a position of a camshaft.

[0029] In particular, for the test bench procedure, a condition of the exhaust line downstream of the exhaust turbocharger with regard to flow resistance and the resulting current exhaust backpressure in the second section is known (or is determined as part of the test bench procedure). The test bench procedure comprises at least the following steps: a) Measuring a profile of the first pressure during operation of the internal combustion engine with a first sensor; b) Measuring a profile of the second pressure during operation of the internal combustion engine with a second sensor; c) Determining the operating points and the crankshaft angle positions at which the first pressure (substantially) corresponds to the second pressure.

[0030] The condition of the exhaust line includes, for example, the loading of the at least one exhaust treatment component in the second section. This condition particularly includes knowledge of all factors that influence the exhaust backpressure in the second section. In particular, these are (exclusively) factors that do not change, for example, when a gas is passed through (without soot and reaction in one of the exhaust treatment components or interaction with the second section of the exhaust line).

[0031] In particular, knowing that the first pressure or the first profile changes based on this known state can be used to infer one or more causes for the resulting change in the second pressure or the second profile. In particular, this can be used to determine the loading state of an exhaust gas treatment component (e.g., a particulate filter).

[0032] Preferably, starting from step c), a characteristic curve for an adaptation value can be determined, by which a second pressure is determined for other operating points of the internal combustion engine from the measurement of the first pressure. This characteristic curve includes, in particular, the operating points and crankshaft angle positions determined in step c) as reference points and is generated therefrom for other operating points. Using the adaptation value, it is particularly possible to also determine the second pressure at these other operating points based on the measured first pressure.

[0033] In particular, during operation of the internal combustion engine, the second pressure and thus a current exhaust back pressure in the second section is determined based on a change in the first pressure.

[0034] The current exhaust back pressure can be used for at least the following control processes: (1) Control of a boost pressure for the internal combustion engine (in particular the pressure provided on the fresh air side of the internal combustion engine); (2) Control of a gas exchange model of the internal combustion engine (in particular the supply of fresh air, exhaust gas, fuel for combustion in the combustion chambers of the internal combustion engine as well as the removal of the exhaust gas from the combustion chambers are controlled by this; furthermore the ignition timing, the valve opening timing, etc.); (3) Correction of the gas exchange model based on the current exhaust gas back pressure; (4) Diagnosis of an exhaust gas turbocharger component (e.g. analysis of the exhaust gas turbocharger speed to avoid exceeding predetermined limit speeds; to protect the exhaust gas turbocharger from mechanical and / or thermal damage); (5) Control of a regeneration of an exhaust gas treatment component arranged in the second section (e.g. a particulate filter in which, for example,the temperature of the exhaust gas is at least temporarily increased or additional oxygen and / or fuel is provided).

[0035] These controls depend in particular on an exhaust back pressure that exists in the second section of the exhaust line downstream of the exhaust turbocharger.

[0036] In particular, at least one exhaust gas treatment component (e.g., a particulate filter) is arranged in the second section, which influences the current exhaust gas backpressure in the second section upstream of the exhaust gas treatment component as a function of at least a soot load on the exhaust gas treatment component. In particular, the load can be determined by determining the current exhaust gas backpressure (or the second pressure). In particular, this also allows the effectiveness of a performed regeneration of the particulate filter to be checked.

[0037] The load of a particulate filter, for example, refers in particular to the quantity or mass of solids (such as soot particles) currently stored in the particulate filter. A particulate filter in the present sense refers in particular to a so-called wall-flow filter, i.e., a component with a plurality of channels (e.g., in the manner of a honeycomb structure) that are particularly closed at opposite ends and thus require the exhaust gas containing the solids to pass through a gas-permeable or porous wall. In this process, the solids are deposited and / or retained on or in the walls. As the load increases, the walls or channels become clogged.

[0038] Furthermore, a computer program is proposed that is configured to execute the method already described. In particular, an engine control system is proposed that at least partially executes the method proposed here.

[0039] Furthermore, a machine-readable storage medium (e.g. in a control unit assigned to the internal combustion engine) is proposed on which the computer program already described is stored.

[0040] Furthermore, an internal combustion engine with an exhaust line is proposed, through which an exhaust gas originating from the internal combustion engine can be conducted via an exhaust gas turbocharger. The internal combustion engine is particularly intended for installation in a motor vehicle or is arranged in a motor vehicle.

[0041] The exhaust line has a first section downstream of the internal combustion engine and upstream of the exhaust gas turbocharger, and a second section downstream of the exhaust gas turbocharger. A first sensor for measuring a first pressure is arranged in the first section. The internal combustion engine further comprises a control unit that is suitable for carrying out the method described above, or is suitably designed and configured, or carries out or can carry out the method.

[0042] The process can be used in particular for all types of internal combustion engines (gasoline engines, diesel engines, etc.) and especially in combination with other drive units (electric drives).

[0043] The statements on the proposed method are transferable to the proposed internal combustion engine, the computer program and the storage medium and vice versa.

[0044] As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and therefore do not necessarily specify any interdependence and / or sequence of these objects, quantities, or processes. Should a dependence and / or sequence be required, this is explicitly stated here or will be obvious to the person skilled in the art upon studying the specifically described embodiment.

[0045] The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other components and findings from the present description and / or figures. In particular, it should be noted that the figures and in particular the illustrated proportions are only schematic. The same reference numerals denote the same objects, so that explanations from other figures can be used as a supplement if necessary. They show: Fig. 1: an internal combustion engine with an exhaust pipe; and Fig. 2: a pressure-time diagram.

[0046] The Figure 1shows an internal combustion engine 1 with an exhaust line 2. An exhaust gas 3 originating from the internal combustion engine 1 is conducted through the exhaust line 2 via an exhaust gas turbocharger 4. The exhaust line 2 has a first section 6 downstream of the internal combustion engine 1 and upstream of the exhaust gas turbocharger 4, and a second section 8 downstream of the exhaust gas turbocharger 4. A first sensor 13 for measuring a first pressure 5 is arranged in the first section 6. The internal combustion engine 1 further comprises a control unit 21 suitable for carrying out the described method.

[0047] By measuring a first pressure 5 in a first section 6 of the exhaust line 2, a second pressure 7 is determined in a second section 8 of the exhaust line 2 downstream of the exhaust gas turbocharger 4. This determination of the second pressure 7 is derived from the condition that at certain operating points 9 of the internal combustion engine 1 at certain crankshaft angle positions 10, the first pressure 5 corresponds to the second pressure 7.

[0048] In the second section 8, an exhaust gas treatment component 17 (particle filter, catalyst, flow influencer, injection device, heating device, etc.) is arranged.

[0049] In a test bench procedure, a second (pressure) sensor 15 (indicated here by dashed lines) can be arranged in the second section 8, thus measuring the second pressure 7 and the second curve 14 in the second section 8. In the test bench procedure, the operating points 9 and crank angle positions 10 at which the magnitudes of the first pressure 5 and the second pressure 7 are equal can be determined for each configuration of internal combustion engine 1, exhaust line 2, exhaust treatment components 17, drive train (e.g., transmission, additional drive units, etc.).

[0050] The operating points 9 and crank angle positions 10 thus determined in the test bench procedure can then be used in the procedure already described, so that the internal combustion engine 1 of the same type (as the configuration used in the test bench procedure) produced in large quantities can be used without a second sensor 15.

[0051] An exhaust gas treatment component 4 (e.g., a particulate filter) is arranged in the second section 8, by which the current exhaust gas backpressure 11 is influenced in the second section 8 upstream of the exhaust gas treatment component 4 as a function of at least a soot loading 18 of the exhaust gas treatment component 17. The loading 18 can be determined by determining the current exhaust gas backpressure 11 (or the second pressure 7).

[0052] The control unit 21 can detect the pressures 5 and 7. The computer program 19, which is stored on a machine-readable storage medium 20, is stored in the control unit 21. Furthermore, the characteristic curve 16 is stored in the control unit 21.

[0053] Fig. 2 shows a pressure-time diagram. Pressure 5, 7 is plotted on the vertical axis. Time 22, or the recurring crankshaft angle position 10, is plotted on the horizontal axis.

[0054] The first pressure 5 in the first section 6 changes depending on the respective operating point 9 and the crankshaft angular position 10 (at the respective operating point 9). Depending on the crankshaft angular position 10, the exhaust valves of the combustion chambers are actuated so that exhaust gas 3 from the combustion chambers can enter the first section 6. It has now been determined that at certain operating points 9 and for certain crankshaft angular positions 10 then present, the first pressure 5 upstream of the exhaust gas turbocharger 4 has the same magnitude as the second pressure 7 downstream of the exhaust gas turbocharger 4 (see intersection points of the first curve 12 of the first pressure 5 and the second curve 14 of the second pressure 7).It has further been determined that this point in time in the first curve 12 of the first pressure 5 can be determined very precisely, so that the second pressure 7 can be derived with high accuracy from the first curve 12 of the first pressure 5.

[0055] It is further known that the second pressure 7 has a specific second curve 14 depending on the first curve 12 of the first pressure 5.

[0056] From these conditions, it was derived that the second curve 14 of the second pressure 7 can be determined as a function of the first curve 12 of the first pressure 5. Furthermore, based on a change in the first pressure 5, in particular at the specific operating points 9 and at the specific crankshaft angle positions 10, a change in the second pressure 7 and thus a currently existing exhaust backpressure 11 in the second section 8 of the exhaust line 2 can be determined. LIST OF REFERENCE SYMBOLS

[0057] 1 Internal combustion engine 2 Exhaust pipe 3 Exhaust gas 4 Exhaust turbocharger 5 First pressure 6 First section 7 Second pressure 8 Second section 9 Operating point 10 Crankshaft angle position 11 Exhaust back pressure 12 First curve 13 First sensor 14 Second curve 15 Second sensor 16 Characteristic curve 17 Exhaust treatment component 18 Loading 19 Computer program 20 Machine-readable storage medium 21 Control unit 22 Time

Claims

1. Method for operating an internal combustion engine (1) having an exhaust line (2) which conducts an exhaust gas (3) from the internal combustion engine (1) via an exhaust gas turbocharger (4), a second pressure (7) in a second portion (8) of the exhaust line (2) downstream of the exhaust gas turbocharger (4) being determined by measuring a first pressure (5) in a first portion (6) of the exhaust line (2) downstream of the internal combustion engine (1) and upstream of the exhaust gas turbocharger (4); characterized in that this determination of the second pressure (7) is derived from a relationship according to which the first pressure (5) in predetermined operating points (9) of the internal combustion engine (1) corresponds to the second pressure (7) at predetermined crankshaft angle positions (10); the first pressure (5) in the first portion (6) changing depending on each existing operating point (9) and on the crankshaft angle position (10) in the relevant operating point (9); the exhaust valves of the combustion chambers being actuated depending on the crankshaft angle position (10), so that the exhaust gas (3) from the combustion chambers can enter the first portion (6); in operating points (9) to be specifically determined and for determined crankshaft angle positions (10) which are then definitely present, the first pressure (5) upstream of the exhaust gas turbocharger (4) having the same magnitude as the second pressure (7) downstream of the exhaust gas turbocharger (4); this point in time in the first curve (12) of the first pressure (5) being determined very precisely as part of a test bench method on the basis of intersection points of the first curve (12) of the first pressure (5) and the second curve (14), which is different therefrom, of the second pressure (7), so that the second pressure (7) can be derived with a high level of accuracy from the first curve (12) of the first pressure (5).

2. Method according to claim 1, wherein the internal combustion engine (1) is operated on a test bench in a test bench method in order to ascertain the operating points (9) and the crankshaft angle positions (10).

3. Method according to claim 2, wherein, for the test bench method, a state of the exhaust line (2) downstream of the exhaust gas turbocharger (4) with regard to a through-flow resistance and a resulting current exhaust gas back-pressure (11) in the second portion (8) is known; wherein the test bench method comprises at least the following steps: a) measuring, using a first sensor (13), a first curve (12) of the first pressure (5) during operation of the internal combustion engine (1); b) measuring, using a second sensor (15), a second curve (14) of the second pressure (7) during operation of the internal combustion engine (1); c) ascertaining the operating points (9) and the crankshaft angle positions (10) at which the first pressure (5) corresponds to the second pressure (7).

4. Method according to claim 3, wherein, starting from step c), a characteristic curve (16) for an adaptation value is ascertained, by means of which a second pressure (7) is determined from the measurement of the first pressure (5) for other operating points (9) of the internal combustion engine (1).

5. Method according to any of the preceding claims, wherein, during operation of the internal combustion engine (1), the second pressure (7) and thus a current exhaust gas back-pressure (11) in the second portion (8) is determined on the basis of a change in the first pressure (5).

6. Method according to claim 5, wherein the current exhaust back-pressure (11) is used at least for the following control processes: (1) controlling a boost pressure for the internal combustion engine (1); (2) controlling a charge exchange model of the internal combustion engine (1); (3) diagnosing exhaust gas turbocharger overspeed; (4) controlling regeneration of an exhaust gas treatment component (17) arranged in the second portion (8).

7. Method according to one of the preceding claims 5 and 6, wherein at least one exhaust gas treatment component (17) is arranged in the second portion (8), by means of which the current exhaust gas back-pressure (11) is influenced in the second portion (8) upstream of the exhaust gas treatment component (17) depending on at least a loading (18) of the exhaust gas treatment component (17) with soot; wherein the loading (18) can be determined by determining the current exhaust gas back-pressure (11).

8. Internal combustion engine (1) comprising an exhaust line (2) through which an exhaust gas (3) can be conducted from the internal combustion engine (1) via an exhaust gas turbocharger (4), wherein the exhaust line (2) has a first portion (6) downstream of the internal combustion engine (1) and upstream of the exhaust gas turbocharger (4) and a second portion (8) downstream of the exhaust gas turbocharger (4); wherein a first sensor (13) for measuring a first pressure (5) is arranged in the first portion (6); wherein the internal combustion engine (1) further comprises a control unit (21) which is suitable for carrying out the method according to any of the preceding claims 1 to 7.

9. Computer program (19) comprising program code that executes the method according to any of claims 1 to 7 when it runs on the control unit (21) of the internal combustion engine according to claim 8.

10. Machine-readable storage medium (20) on which the computer program (19) according to claim 9 is stored.