Operating method of a fresh air supply device, use of such a fresh air supply device in an internal combustion engine and internal combustion engine with such a fresh air supply device

Abstract

Operating method of a fresh air supply device (1) of an internal combustion engine, wherein the fresh air supply device (1), which is configured to supply fresh air from an environment surrounding the internal combustion engine into at least one combustion chamber of the internal combustion engine, has a controllable throttle valve (6) which is configured to change a flowable area of ​​the fresh air supply device (1) and to at least partially shut off the fresh air supply device (1) and wherein the fresh air supply device (1) has a compressor device (3) which is arranged in a planned flow direction (10) from the environment into the combustion chamber, upstream to the throttle valve (6) and is designed to deliver an air mass flow in the planned flow direction (10) in the fresh air supply device (1) and wherein a pre-compressor section (2) of the fresh air supply device (1) is arranged upstream of the compressor device (3), an intermediate section (4) is arranged downstream of the compressor device (3) and upstream of the throttle valve (6), and a post-throttle section (7) is arranged downstream of the throttle valve (6), wherein a first air pressure sensor (8) is arranged in the pre-compressor section (2) and wherein a second air pressure sensor (9) is arranged in the post-throttle section (7), characterized by the fact that in a first operating state of the fresh air supply device, a first air pressure is measured with the first air pressure sensor (8), and in a second step in this first operating state, a second air pressure is measured with the second air pressure sensor (9) and that, on the basis of this second air pressure, a theoretical air pressure for the intermediate section (4) is determined as a function of a theoretically flowable area set with the throttle valve (6), that the theoretical air pressure is compared with the first air pressure or a reference value for the first air pressure and that if the theoretical air pressure deviates from the first air pressure or the reference value beyond an error threshold, a correction value for determining the theoretical air pressure is determined and that the correction value determined from this comparison for the calculation of the theoretical air pressure refers to the effective area of ​​the throttle valve, since the effective area of ​​the throttle valve, i.e. the flowable area in the region of the throttle valve, which depends on the degree of opening of the throttle valve, is adjusted in the calculation.

Description

[0001] The invention relates to an intake air guide for an internal combustion engine, wherein in this intake air guide a sensorless intake air pressure determination takes place in at least one sub-area and with a method for determining the intake air pressure.

[0002] DE 10 2016 117 139 A1 deals with a method and system for pump control, which also deals with pressure in the intake manifold of an internal combustion engine.

[0003] DE 10 2007 000 300 A1 deals with the control system for a turbocharged internal combustion engine.

[0004] From EP 2 447 516 A1, a method for determining the pressure at the outlet of an exhaust system of an internal combustion engine system of a vehicle is known. In this method, a mass flow rate through the internal combustion engine system and an ambient pressure at a fresh air supply of the internal combustion engine system are measured.

[0005] From DE 10 2015 224 828 A1, a control system for an internal combustion engine is known, wherein this internal combustion engine comprises a so-called turbocharger, which has a turbine provided in an exhaust gas path and a compressor provided on the upstream side of a throttle valve in an inlet path and integrally connected to the turbine and rotating with it. Furthermore, the turbocharger has a wastegate valve provided in a turbine bypass path of the exhaust gas path, which bypasses the turbine.

[0006] The invention is described below in connection with a specific internal combustion engine; this is not to be understood as limiting the invention to this application. An internal combustion engine that runs on diesel fuel, a so-called diesel engine, typically has a throttle valve in the fresh air intake. The fresh air intake is understood to be a line that supplies fresh air from the environment surrounding the internal combustion engine to at least one combustion chamber of this engine. Downstream of the throttle valve, i.e., a device arranged in the fresh air intake that is configured to preferably completely or partially close off the fresh air intake, a pressure sensor is arranged in the intended flow direction through this fresh air intake (from the environment into the combustion chamber). This pressure sensor measures the air pressure in this section of the fresh air intake.The air pressure in the fresh air intake before the throttle valve is also important for controlling the internal combustion engine. To save costs, this pressure is not measured with a sensor, but can be determined based on the throttle valve's position and the measured air pressure downstream of the throttle valve. The following parameters can be considered for this determination: air pressure downstream of the throttle valve (measured), temperature upstream of the throttle valve (measured), the mass airflow (measured), and the effective area (the area through which air flows in the throttle valve, which depends on the throttle valve's opening degree). If one or all of these parameters are known, the determination can be made with sufficient accuracy.

[0007] Investigations show that this determination can be faulty in certain situations, which can lead to efficiency losses in the control of the internal combustion engine. In particular, deposits can adhere to the throttle valve during operation of the internal combustion engine, so that the actual flow area at the throttle valve deviates from the previously mentioned effective area, or the area assumed solely based on the throttle valve opening degree. This leads to an incorrect determination of the air pressure upstream of the throttle valve. Furthermore, the throttle valve and the fresh air intake are subject to manufacturing tolerances, which can also affect the actual flow area at the throttle valve and likewise lead to an incorrect determination of the air pressure upstream of the throttle valve.

[0008] It is an object of the invention to provide a method for determining the air pressure upstream of the throttle valve and a fresh air supply controlled by this method. This object is achieved by a method according to the first claim and by a device controlled by this method according to claim 3. Preferred embodiments of the invention are the subject of the dependent claims.

[0009] An operating method for a fresh air supply device is proposed. For the purposes of the invention, a fresh air supply device is understood to be a device for supplying fresh air from the environment surrounding the internal combustion engine into at least one combustion chamber or combustion chamber of the internal combustion engine. The fresh air supply device is thus understood to be a device for guiding a mass flow of air to at least one combustion chamber, wherein this mass flow from the environment into the combustion chamber passes through the fresh air supply device in a planned flow direction. Such a fresh air supply device therefore comprises pipes and other devices for guiding the fresh air.

[0010] One such additional device in the fresh air supply system is a controllable throttle valve. For the purposes of the invention, such a throttle valve is understood to be a device for controlling, or at least influencing, the air mass flow in the fresh air supply system. Preferably, the throttle valve allows for the variation of the area through which this air mass flow passes in the fresh air supply system. The size of this area is determined, in particular, indirectly or derived from the degree of opening of the throttle valve. Especially if the throttle valve has a throttle flap, the degree of opening of the throttle valve can be described by means of an opening angle of the throttle flap, and furthermore, a specific flow area can be assigned to each opening angle. In this context, the indirectly determined area at the throttle valve is referred to as the effective area.In colloquial terms, this effective area can also be understood as the presumed area, since, as explained, it is only determined indirectly.

[0011] Another component in the fresh air supply system is a compressor unit. Preferably, such a compressor unit is a pump unit. The compressor unit is preferably designed as a compressor of a so-called supercharger and more preferably as a compressor of an exhaust gas turbocharger. The compressor unit is therefore configured, at least temporarily, to supply fresh air from the environment surrounding the internal combustion engine into the at least one combustion chamber, and more preferably, the compressor unit is configured to generate the air mass flow. With respect to the intended flow direction, this compressor unit is arranged upstream of this throttle valve.In particular, the throttle valve and the compressor unit, both of which are located in the fresh air supply unit, result in a division of this unit into a pre-compressor section upstream of the compressor unit, an intermediate section downstream of the compressor unit and upstream of the throttle valve, and a post-throttling section downstream of the throttle valve.

[0012] The pressure conditions in the fresh air supply are crucial for controlling the fresh air intake and thus for the operation of an internal combustion engine. Due to the compressor action at the compressor unit and the throttling effect at the throttle valve, different pressures can occur in the three aforementioned sections of the fresh air supply system at certain operating points.

[0013] The operating procedure proposes a variant for determining the air pressures in all three sections of the fresh air supply system using only two air pressure measuring points. A first air pressure sensor is arranged in the pre-compressor section, which is configured to determine and preferably measure the air pressure in the air mass flow in this section; this is referred to as the first air pressure sensor. A second air pressure sensor is arranged in the post-throttling section, which is also configured to determine and preferably measure the air pressure in the air mass flow in this section. Preferably, the intermediate section is designed without air pressure sensors; in this section of the fresh air supply system, an air pressure sensor is arranged, or the proposed method is applied in the event of a failure or if an air pressure sensor located there is not operating.

[0014] The proposed operating procedure comprises the following steps, which can also be carried out in a different order than specified. In a first operating state of the fresh air supply device, a first air pressure is measured with the first air pressure sensor. Preferably, this first air pressure can be converted into a reference value. Such a conversion is particularly possible if it is known that the air pressure at the intermediate distance in this first operating state differs from this first measured air pressure, wherein the first operating state is selected such that the relationship between the first air pressure and the air pressure at the intermediate distance is known in this operating mode.Preferably, in this first operating state, the internal combustion engine, which is supplied with fresh air via the fresh air supply device, is in an idling state, or more preferably, this first operating state is a state in which the air pressure in the pre-compressor section is known to correspond to the air pressure in the intermediate section.

[0015] In particular, such a state can be determined by means of experiments or calculations, or can be predicted based on experience.

[0016] In a further step, a second air pressure is measured with the second air pressure sensor in the same operating state as the first one mentioned above. Preferably, the two air pressures can be measured at the same time, or preferably in the same operating state but at different times.

[0017] In a further step, a theoretical air pressure for the intermediate section is determined based on this measured second air pressure. This theoretical air pressure for the intermediate section is calculated as a function of the flow area, the so-called effective area, set by the throttle valve. Preferably, further parameters are incorporated into this calculation of the air pressure for the intermediate section, the air pressure calculation itself being possible using known relationships from the prior art.

[0018] This theoretical air pressure, i.e., the air pressure determined by the measurement with the second air pressure sensor and as a function of the effective area, is compared with the first air pressure, i.e., the air pressure measured in the pre-compressor section for the same operating condition. Particularly under ideal conditions, i.e., when the effective area exactly corresponds to the actual flow area, then the first air pressure and the theoretical air pressure either coincide, or the theoretical air pressure deviates from this first air pressure by a predetermined threshold value. Preferably, the predetermined threshold value takes into account an air pressure difference that is expected to occur between the pre-compressor section and the intermediate section under the first operating condition.

[0019] If this comparison of the theoretical air pressure with the first air pressure reveals an unplanned deviation, particularly if the deviation lies outside a predefined air pressure tolerance range, a correction value for determining the theoretical air pressure is calculated from the comparison. Specifically, the effective area of ​​the throttle valve is adjusted in the calculation. This procedure thus calibrates the determination of the air pressure for the intermediate section, since the first operating condition is chosen such that the air pressure in the intermediate section can be reliably inferred from the first air pressure, or rather, because the first operating condition is chosen such that the first air pressure corresponds to the air pressure in the intermediate section. In this context, air pressure refers to the air pressure in the air mass flow and not to static conditions.In operating conditions that deviate from the first operating condition, the air pressure in the air mass flow in the intermediate range can then be accurately determined based on the calibrated calculation.

[0020] In a preferred embodiment, the fresh air supply device has at least one second operating state, which differs from the first operating state. In this second operating state, an internal combustion engine can be operated in partial-load or full-load mode using the fresh air supply device. Preferably, in this second operating state of the fresh air supply device, a corrected air pressure for the intermediate range is determined. This corrected air pressure is preferably based on the correction value determined in the first operating state, derived from a second air pressure measured in this second operating state (measurement with the second air pressure sensor). Preferably, to determine the corrected air pressure, the air pressure in this post-throttling section is measured in the second operating state using the second air pressure sensor.Furthermore, the correction value determined in the first operating state is used to calculate the corrected air pressure. Specifically, the effective area is corrected, and the air pressure in the intermediate section is determined in the second operating state using this corrected effective area. This method allows for a more precise determination of the air pressure in the intermediate section in the second operating state, where the air pressure in the pre-compressor section does not correspond to the air pressure in the intermediate section. This is based on the air pressure determined in the post-throttling section, thus enabling improved control of the fresh air supply system.

[0021] Furthermore, the use of a fresh air supply device in an internal combustion engine is proposed. The fresh air supply device is designed to supply fresh air from the environment surrounding the internal combustion engine into at least one combustion chamber of the engine and is configured as previously described. Accordingly, the fresh air supply device includes a controllable throttle valve, which is designed to change the cross-sectional area through which the air flows. The fresh air supply device also includes a compressor unit, which is arranged upstream of the throttle valve in the intended flow direction, i.e., from the environment into the combustion chamber. As explained, this fresh air supply device is divided into three sections by means of the compressor unit and the throttle valve.In the fresh air supply device, the pre-compressor section is arranged upstream of the compressor device, the intermediate section is arranged downstream of the compressor device and upstream of the throttle valve, and the post-throttle section is arranged downstream of the throttle valve.

[0022] Furthermore, a first air pressure sensor is arranged in the pre-compressor section, and a second air pressure sensor is arranged in the post-throttling section. Preferably, no air pressure sensor is arranged in the intermediate section, and thus, more preferably, the intermediate section is designed without an air pressure sensor. Furthermore, the fresh air supply device is controlled, at least intermittently, according to a method based on one of the previously described embodiments. In particular, a fresh air supply device of the aforementioned design, operated with the proposed methods, makes it possible to determine the pressure in three different areas of the fresh air supply, whereby the pressure is only measurable in two of these three areas and is determined in the third area from one of the other two air pressures. This also results in the advantage of precise air pressure determination with minimal hardware requirements.

[0023] Furthermore, an internal combustion engine is proposed with one or more combustion chambers, wherein at least one combustion chamber can be supplied with fresh air from the environment surrounding the internal combustion engine via a fresh air supply of the aforementioned design, and wherein the operating procedure described above can be carried out using the fresh air supply. Furthermore, this operating procedure for operating the fresh air supply is stored in the form of computer-executable instructions on an electronic engine control unit, and preferably, the fresh air supply, and thus also the internal combustion engine, is controlled, at least temporarily, by this procedure.

[0024] The following section explains individual features and embodiments of the invention in more detail with reference to the figure, whereby other combinations of the features of the invention than those shown are also possible, as shown: Fig. 1: a part of a schematic fresh air supply system, Fig. 2: a schematic flowchart for the operating procedure.

[0025] The fresh air supply unit 1 is divided into three sections by the compressor unit 3 and the throttle valve 6 with the throttle flap 5. The pre-compressor section 2 is located upstream of the compressor unit 3, which in this case is designed as the high-pressure stage of an exhaust gas turbocharger, with respect to the planned flow direction 10 through the fresh air supply unit 1, i.e., with respect to an air mass flow from the environment into at least one combustion chamber of an internal combustion engine. The intermediate section 4 is further arranged downstream of the compressor unit 3 and upstream of the throttle valve 6 with respect to this planned flow direction 10. The post-throttle section 7 is further arranged downstream of the throttle valve 6.

[0026] In the pre-compressor section 2, a first air pressure sensor 8 is arranged with which the air pressure in the air mass flow in this section can be measured. Furthermore, in the post-throttling section 7, a second air pressure sensor 9 is arranged with which the air pressure in the air mass flow in this section can be measured. The intermediate section 4 is designed without air pressure sensors; therefore, measuring the air pressure in this area is not possible with the proposed fresh air supply system. However, knowing the air pressure during operation of the internal combustion engine improves the control accuracy of the fresh air supply system.

[0027] To determine the air pressure during the operation of the internal combustion engine, i.e., when the air mass flow passes through the fresh air supply device, the pressure drop during the passage of the air mass flow 11 through the throttle valve 6 can be determined by measuring the air pressure with the second air pressure sensor 9, using known physical relationships. However, such a calculation of the air pressure in the intermediate zone 4 requires at least an assumption of the size of the area through which the air mass flow 11 passes, the so-called effective area. The effective area depends in particular on the degree of opening of the throttle valve. If this assumed effective area does not correspond to the actual area through which the air mass flow 11 passes, then the calculated air pressure in the intermediate zone 11 will also deviate from the actual prevailing air pressure.Deviations in the surface area can occur due to unavoidable manufacturing tolerances. The actual surface area can also change during the service life, particularly due to deposits. Therefore, a calculation calibrated when new may deviate from reality after a considerable operating period. To avoid the need for an additional air pressure sensor in the intermediate section, the invention proposes a repeatable calibration of the air pressure determination in the intermediate section 4. In a first operating state, the air pressure in the air mass flow is measured using the first and second air pressure sensors 8, 9. This first operating state is selected such that the air pressure in the air mass flow in the pre-compressor section 2 and in the intermediate section 4 is at least approximately the same or differs by a known pressure difference.Next, the calculation of the air pressure for the intermediate range 4, which as explained is based on the air pressure measured with the second air pressure sensor 9, is carried out and the air pressure thus determined is compared with the air pressure determined with the first air pressure sensor 8.

[0028] If there is a discrepancy in this comparison, the calculation, based on the air pressure measured by the second air pressure sensor 9, is adjusted so that the calculation is "correct," in particular, the airflow in the throttle valve is modified. In other words, the calculation of the air pressure for the intermediate section 4 is calibrated in this process.

[0029] If the internal combustion engine is operated in a different operating mode than in the first operating mode, i.e. in a partial load or full load operating mode, the calibrated calculation method for determining the air pressure in the intermediate range 4 is applied on the basis of the air pressure measured with the second air pressure sensor 9, and thus the air pressure for the intermediate range in this second operating mode can be determined more accurately than without calibration.

[0030] In Fig.Figure 2 shows a flowchart for the proposed operating procedure. In step 101, the air pressure in the first operating state in the pre-compressor section is measured using the first air pressure sensor 8. In step 102, the air pressure in the first operating state in the post-throttling section is measured using the second air pressure sensor 9. In step 103, the air pressure measured in step 102 is converted into the pressure in the intermediate section 4 using a throttling equation, taking into account the assumptions made, in particular the effective area. The air pressure thus determined for the intermediate section is then compared in step 104 with the air pressure measured in step 101.If this comparison shows that the two air pressures differ from each other by a specified tolerance, the calculation methodology for the air pressure measured on the basis of the measurement with the second air pressure sensor 9 is adjusted, in particular the size of the effective area is adjusted, in particular the area through which the air can flow is determined.

[0031] With the adapted calculation methodology, in particular with the calibrated calculation based on the measured value from the second air pressure sensor 9, the air pressure is calculated in step 105 in an operating state that differs from the first operating state.

[0032] In other words, the invention is applied to a reciprocating internal combustion engine, in which a throttle valve is installed in the fresh air supply system. An air pressure sensor is located downstream of the throttle valve. However, the air pressure in the air mass flow upstream of the throttle valve during engine operation is also relevant for controlling the internal combustion engine and the fresh air supply system. To save costs, this air pressure is not measured with an air pressure sensor, but calculated using a well-known throttle equation. The following parameters, in particular, are included in this equation: - Air pressure downstream of the throttle valve, - Air temperature upstream of the throttle valve, - Air mass flow and - the effective area in the throttle valve through which this mass airflow can flow, this is particularly dependent on the throttle valve position.

[0033] The effective area is therefore only indirectly known, since it is unknown, in particular, whether the throttle valve becomes clogged with contaminants over time; only the set opening degree or opening angle is known. If the aforementioned parameters are known, it is possible to calculate the air pressure in the intermediate range. However, due to fouling / contamination, especially on the throttle valve, particularly through soot deposits, and due to component variations resulting from manufacturing tolerances, deviations can occur between the air pressure determined using the proposed calculation method and the actual air pressure prevailing in the intermediate range.

[0034] The invention utilizes the principle in an internal combustion engine with an exhaust gas turbocharger that the air pressure in the intermediate section 4 can be deduced from the air pressure measured in the pre-compressor section 2. In the first operating mode, particularly in the idle mode of the internal combustion engine, the air pressure is known with sufficient accuracy because the compressor unit 3 of the exhaust gas turbocharger, or rather the high-pressure stage of the exhaust gas turbocharger, generates very little boost pressure. An air pressure sensor is located upstream of this high-pressure stage. Using a simple calculation model, the pressure before the throttle valve can be estimated at idle. At other operating points of the internal combustion engine, this is not possible with the required accuracy. With the help of the calculation methodology calibrated at idle, the air pressure in the intermediate section 4 can be determined more accurately than without the calibration.

[0035] Conversely, calibration minimizes area errors (the presumed or effective area in the throttle valve compared to the actual flow area). The flow area determined in the first operating mode can be stored in a control unit as a basis for calculations and used to determine air pressure in all other operating ranges. This method, in particular, allows for the consideration of the influence of component tolerances and unknown sooting / contamination in the fresh air supply system. An air pressure sensor upstream of the throttle valve is not necessary, although precise air pressure measurement is possible.

Claims

[1] Operating method of a fresh air supply device (1) of an internal combustion engine, wherein the fresh air supply device (1), which is configured to supply fresh air from an environment surrounding the internal combustion engine into at least one combustion chamber of the internal combustion engine, has a controllable throttle valve (6) which is configured to change a flowable area of ​​the fresh air supply device (1) and to at least partially shut off the fresh air supply device (1) and wherein the fresh air supply device (1) has a compressor device (3) which is arranged in a planned flow direction (10) from the environment into the combustion chamber, upstream to the throttle valve (6) and is designed to deliver an air mass flow in the planned flow direction (10) in the fresh air supply device (1) and wherein a pre-compressor section (2) of the fresh air supply device (1) is arranged upstream of the compressor device (3), an intermediate section (4) is arranged downstream of the compressor device (3) and upstream of the throttle valve (6), and a post-throttle section (7) is arranged downstream of the throttle valve (6), wherein a first air pressure sensor (8) is arranged in the pre-compressor section (2) and wherein a second air pressure sensor (9) is arranged in the post-throttle section (7), characterized by , that in a first operating state of the fresh air supply device, in a first step a first air pressure is measured with the first air pressure sensor (8), that in a second step in this first operating state a second air pressure is measured with the second air pressure sensor (9) and that, on the basis of this second air pressure, a theoretical air pressure for the intermediate section (4) is determined as a function of a theoretically flowable area set with the throttle valve (6), that the theoretical air pressure is compared with the first air pressure or a reference value for the first air pressure and that if the theoretical air pressure deviates from the first air pressure or the reference value beyond an error threshold, a correction value for determining the theoretical air pressure is determined and that the correction value determined from this comparison for the calculation of the theoretical air pressure refers to the effective area of ​​the throttle valve, since the effective area of ​​the throttle valve, i.e. the flowable area in the region of the throttle valve, which depends on the degree of opening of the throttle valve, is adjusted in the calculation. [2] Operating method according to claim 1, characterized by , that in a second operating state of the fresh air supply device (1) a corrected air pressure for the intermediate range (4) is determined and that to determine the corrected air pressure, the air pressure in this post-throttle section (7) is measured with the second air pressure sensor (9) and that this correction value is used to determine the corrected air pressure. [3] Use of a fresh air supply device (1) in an internal combustion engine, wherein the fresh air supply device is configured to supply fresh air from an environment surrounding the internal combustion engine into at least one combustion chamber of the internal combustion engine, and furthermore the fresh air supply device (1) has a controllable throttle valve (6) for changing a flow area of ​​the fresh air supply device (1), which is configured to at least partially shut off the fresh air supply device (1), and furthermore the fresh air supply device (1) has a compressor device (3) which is arranged in a planned flow direction (10) from the environment into the combustion chamber, upstream of the throttle valve (6), and upstream of the compressor device (3) a pre-compressor section (2) of the fresh air supply device (1) is arranged,Downstream of the compressor unit (3) and upstream of the throttle valve (6) an intermediate section (4) is arranged and downstream of the throttle valve (6) a post-throttle section (7) is arranged, and furthermore a first air pressure sensor (8) is arranged in the pre-compressor section (2) and a second air pressure sensor (9) is arranged in the post-throttle section (7), . characterized by that the fresh air supply device (1) is controlled at least temporarily according to a method according to one of the preceding claims. [4] Internal combustion engine with a fresh air supply device (1) according to claim 3, characterized by , that the method for controlling the fresh air supply device (1) according to one of claims 1 or 2 is stored on an engine control unit in the form of computer-executable instructions.

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