Engine system of a motor vehicle

Abstract

An engine system of a motor vehicle, comprising an internal combustion engine (20) having a plurality of combustion chambers (201, 202, 203, 204, 205, 206) into which air can be introduced via an air supply system (30), wherein exhaust gases can be discharged from the combustion chambers (201, 202, 203, 204, 205, 206) via an exhaust system (50) which is fluidically connectable to the combustion chambers (201, 202, 203, 204, 205, 206), a turbocharger device (60) comprising a first turbocharger unit (62) and a second turbocharger unit (64), each of which comprises at least one compressor (621, 641) and an electric motor which can be connected to the compressor (621, 641) in a torque-transmitting manner (623, 643), wherein the turbocharger units (62, 64) are fluidically connected on the compressor side to a common air collection chamber (42) of the air supply system (30), a sensor device (44) which has a pressure sensor (46) which is designed to detect the pressure in the air collection chamber (42), a control unit (70),which is designed to control the electric motors (623, 643) of the turbocharger units (62, 64), wherein a modeled speed (nm) of the electric motors determined from the sensor signal of the pressure sensor (46) is compared with an actual speed (nist) of at least one of the electric motors (623, 643) and / or the electrical powers (P1, P2) of the electric motors (623, 643) are compared with one another, wherein if a predefined speed difference threshold is exceeded by the speed difference value and / or if a predefined power difference threshold is exceeded by the power difference value, unstable operation of one of the compressors (621, 641) is concluded.

Description

[0001] The invention relates to an engine system of a motor vehicle.

[0002] Such engine systems are generally known from the prior art. The turbocharger devices can comprise one or more turbocharger units, i.e., multiple compressors, wherein the ambient air flowing into the air supply system is compressed by the turbocharger units before the compressed air is directed into the combustion chambers of the internal combustion engine. With multiple turbocharger units, the compressors of the turbocharger units are fluidly connected at the output side to an air plenum of the air supply system, wherein the compressed air emanating from the individual compressors flows into the air plenum. Thus, both compressors each deliver an air mass flow into the air plenum, wherein the air mass flows are ideally equal.To provide the charged air present in the air plenum for operating the combustion engine, the electric motors, which are connected to the compressor in a torque-transmitting manner, are controlled based on a driver command, in particular based on a boost pressure dependent on the accelerator pedal position required for the corresponding operation of the combustion engine. Based on the driver command, the target air mass flow and the target boost pressure are determined, and the target speed required for the air mass flow and boost pressure is determined. The electric motors are controlled based on the determined target speed.

[0003] Such an engine system is disclosed, for example, in DE 10 2017 200 948 A1. Furthermore, DE 196 15 033 A1 discloses an engine system comprising a plurality of turbocharger units, each assigned to a cylinder bank. A device is provided that determines the difference between the pressures or gas masses prevailing in the two exhaust tracts assigned to the cylinder banks upstream of the turbocharger units and signals a speed deviation if the determined difference exceeds a predeterminable threshold.

[0004] Because the compressors each deliver an air mass flow into the air plenum and no sensors or actuators are arranged in the air flow direction immediately after the individual compressors, the actual air mass flows from the individual compressors to the air plenum are unknown.

[0005] The disadvantage is that there is a risk of unnoticed unstable operation, particularly a stall, of one of the compressors. Such unstable operation can cause hot air to flow upstream of the corresponding compressor, i.e., into the intake area, which could damage components in the intake area.

[0006] The object of the invention is to provide an engine system in which unstable operation of a compressor can be reliably detected and reliably avoided.

[0007] The problem is solved by the features of claim 1.

[0008] The engine system comprises an internal combustion engine having a plurality of combustion chambers into which air can be introduced via an air supply system, wherein exhaust gases can be discharged from the combustion chambers via an exhaust tract that is fluidly connected to the combustion chambers. The internal combustion engine comprises, in particular, a plurality of cylinder banks, wherein a plurality of combustion chambers are each assigned to a cylinder bank. For example, a 6-cylinder engine has two cylinder banks, each of which is assigned three combustion chambers. The engine system further comprises a turbocharger device, a sensor device, and a control unit.The turbocharger device comprises a first turbocharger unit and a second turbocharger unit, each turbocharger unit having at least one compressor and an electric motor that can be connected to the compressor in a torque-transmitting manner. The turbocharger units are fluidly connected on the compressor side to a common air plenum of the air supply system. The sensor device has a pressure sensor designed to detect the pressure in the air plenum. The pressure sensor, or the sensor signals from the pressure sensor, are preferably used for boost pressure control.In this case, the boost pressure is controlled in such a way that a target torque is determined from the driver's request, in particular from an accelerator pedal position, and based on this, the electric motors are controlled by the control unit, which basically serves to control the electric motors, whereby an actual pressure is detected by the pressure sensor, compared with the target pressure and based on this, the control of the electric motors is adjusted.

[0009] According to the invention, the control unit is designed to determine a modeled speed of the electric motors of the turbocharger units based on the sensor signal of the pressure sensor, to compare the modeled speed with an actual speed of the electric motors and to determine a speed difference value, wherein if a predefined speed difference threshold value is exceeded by the speed difference value, an unstable operation of one of the compressors is concluded.

[0010] A comparison of the modeled speed and the actual speed of the electric motors is performed separately for each electric motor. The modeled speed of the electric motors of the turbocharger units is determined based on the sensor signal from the pressure sensor, i.e., the pressure in the air plenum provided by the two compressors, and using a compressor map. A suitable model is used to determine the modeled speed. The actual speed of the compressors can be determined either by a separate, dedicated speed sensor or from the speeds already available from the control of the electric motors.

[0011] During stable operation of both compressors, the pressure in the air plenum corresponds, in particular due to boost pressure control, to the target pressure that should be provided by controlling the electric motors. By comparing the modeled speed, which applies to both compressors, with the actual speeds of the compressors, a speed difference value is determined. If the speed difference values ​​are below a predefined speed difference threshold, stable and non-critical operation of the compressors is present, with the modeled speeds essentially corresponding to the actual speeds of the compressors.

[0012] If the speed difference exceeds the predefined speed difference threshold, unstable and critical operation of one of the compressors occurs. In this case, the compressed air provided by the compressor operating in stable mode flows from the air plenum to the combustion chambers, providing the air mass flow required for the operation of the combustion engine, and through the other compressor operating in unstable mode. Specifically, the compressor operating in unstable mode is experiencing flow stall, meaning that this compressor is not delivering any air mass flow, and no air mass flow is flowing through this compressor into the air plenum.

[0013] When such a condition occurs in the engine system, the pressure in the air plenum, which is detected by the pressure sensor, is initially reduced compared to the target boost pressure. By calculating the modeled speed based on the reduced boost pressure, a reduced, modeled speed is also present. Due to the reduced, modeled speed, this deviates from the actual speed of the compressors. In a subsequent period of time, the actual speeds of the electric motors and thus of the compressors are adjusted or increased due to the boost pressure control in such a way that the target boost pressure is provided again. Here, too, a speed difference value exceeding the speed difference threshold would exist because providing the target boost pressure requires a speed of the electric motors that is higher than the original, predefined speed of the electric motors.

[0014] According to the invention, the control unit is additionally or alternatively designed such that the electrical powers of the electric motors are compared with each other and a power difference value is determined, wherein if a predefined power difference threshold value is exceeded by the power difference value, it is concluded that one of the compressors is operating unstably.

[0015] Here, the electrical power outputs of the electric motors driving the compressors during operation are compared with each other and, based on this, a power difference value is determined. The electrical power outputs are determined from the actual voltages and actual currents available from the control of the electric motors. During stable operation of both compressors, the electrical power outputs of the electric motors are essentially the same. If the electrical power outputs differ, i.e. if the power difference value exceeds the power difference threshold value, one of the compressors is operating unstably. Due to the unstable operation, in particular due to flow separation, the resistance acting on the compressor is reduced, which reduces the torque provided by the electric motor and thus the compressor's delivery rate and electrical power.

[0016] This allows for reliable detection of unstable operation of one of the compressors. Based on this information, appropriate measures can be initiated to correct the unstable operation.

[0017] The problem is also solved by the features of claim 2.

[0018] The engine system of a motor vehicle here also comprises an internal combustion engine having a plurality of combustion chambers into which air can be introduced via an air supply system, wherein exhaust gases can be discharged from the combustion chambers via an exhaust tract that is fluidly connected to the combustion chambers, and a turbocharger device comprising a first turbocharger unit and a second turbocharger unit, each of which has at least one compressor and an electric motor that can be connected to the compressor in a torque-transmitting manner, wherein the turbocharger units are fluidly connected on the compressor side to a common air plenum of the air supply system. Furthermore, the engine system comprises a sensor device and a control unit for controlling the electric motors, wherein the sensor device is designed to determine the air flow properties and / or the operating properties of the turbocharger units.

[0019] According to the invention, the control unit is designed to detect an operation of one of the compressors in an unstable mode from the sensor signals of the sensor device and, based thereon, to adjust the electrical powers of the electric motors to one another.

[0020] The sensor device can, as already explained in the previous approaches, comprise a pressure sensor, whereby the detection of unstable operation of one of the compressors can be carried out according to the explanation in the previous paragraphs using the sensor signals of the pressure sensor or by adjusting the electrical power of the electric motors. Alternatively, the unstable operation of one of the compressors can also be detected in another way.

[0021] According to the invention, the two electric motors' electrical outputs are matched, thereby eliminating any existing pressure differential between the two compressors and thus eliminating the flow stall. This brings the compressor operating in unstable mode back to stable operation.

[0022] In this way, unstable operation of one of the compressors can be reliably avoided.

[0023] The turbocharger device is preferably an exhaust gas turbocharger device, wherein each turbocharger unit has a turbine which is connected to the compressor via a turbocharger shaft in a torque-transmitting manner and which is fluidly connected to an exhaust system, wherein a rotor of the electric motor is connected in a rotationally fixed manner to the turbocharger shaft. As a result, the air mass flows emanating from the individual compressors depend, on the one hand, on the drive power generated by the turbine and, on the other hand, on the drive power generated by the electric motors. The drive power emanating from the turbines depends on the exhaust gas mass flows flowing around and driving the turbine, wherein the target air mass flow required for the operation of the combustion engine can be specifically adjusted by appropriately controlling the electric motors.In this case, the compressor can be accelerated and decelerated by the electric motor in comparison to the turbine, whereby the electric motor is in recuperation mode during deceleration.

[0024] In the event of a stall at one of the compressors, i.e. when the compressor is running in unstable operation, the pressure determined by the pressure sensor drops, and as a reaction to this, the boost pressure control increases the speed controllable by the electric motors. In this case, the compressor running in unstable operation is braked by the electric motor, as the exhaust gases flowing around the turbine would accelerate the compressor to a higher speed, as there is almost no resistance and no flow rate due to the stall. On the other hand, the compressor operating in stable operation is accelerated by the associated electric motor. Due to this mode of operation, both the modeled speed of the compressors deviates from the actual speed of the compressors and the electrical power of the electric motors, with one electric motor driving and the other recuperating, deviates from one another.

[0025] By adjusting the electrical power of the electric motors, in particular the electrical power of the electric motor assigned to the compressor running in unstable operation, the pressure difference between the two compressors is eliminated, whereby the delivery capacities of both compressors are adapted to each other and the stable operation of the compressor previously running in unstable operation is caused.

[0026] Preferably, the air supply system comprises a cooler containing the air plenum. As a result, the two air mass flows emanating from the two compressors converge in the cooler, allowing one air mass flow from the cooler to flow to the combustion chambers of the internal combustion engine. The cooler serves to cool the air heated by the compression process.

[0027] An embodiment of the invention is explained in more detail with reference to the drawings. Fig. 1 shows schematically an engine system of a motor vehicle, and Fig. 2a shows a pressure-time diagram, Fig. 2b shows a speed-time diagram, and Fig. Figure 2c shows a power-time diagram.

[0028] The Fig. 1 shows an engine system 10 of a motor vehicle. The engine system 10 comprises an internal combustion engine 20 with six combustion chambers 201, 202, 203, 204, 205, 206, wherein three cylinders or combustion chambers 201, 202, 203 are assigned to a first cylinder bank 22 and three cylinders or combustion chambers 204, 205, 206 are assigned to a second cylinder bank 24.

[0029] To supply the combustion chambers 201, 202, 203, 204, 205, 206 with air, the engine system 10 has an air supply system 30. The air supply system 30 comprises a first air supply tract 32 and a second air supply tract 34, each of which has an air filter 321, 341 and opens into a common cooler 40. The cooler 40 is fluidly connected to the combustion chambers 201, 202, 203, 204, 205, 206 of the cylinder banks 22, 24 via an air line 36, 38, wherein a throttle valve 361, 381 is provided on each of the two air lines 36, 38.

[0030] To remove the exhaust gases generated during the combustion processes in the combustion chambers 201, 202, 203, 204, 205, 206, the engine system 10 has an exhaust system 50. The exhaust system 50 has two exhaust tracts 52, 54, with a first exhaust tract 52 assigned to the first cylinder bank 22 and a second exhaust tract 54 assigned to the second cylinder bank 24. Thus, the exhaust gases from the combustion chambers 201, 202, 203 are removed via the first exhaust tract 52, and the exhaust gases from the combustion chambers 204, 205, 206 are removed via the second exhaust tract 54. Both exhaust tracts 52, 54 each have a plurality of exhaust aftertreatment components 521, 522, 541, 542, for example an exhaust gas catalyst and a particulate filter, and a silencer 523, 543.

[0031] To increase the engine power of the internal combustion engine 20, the air flowing into the air supply system 30 from the outside environment is compressed. For this purpose, the engine system 10 has a turbocharger device 60, wherein the turbocharger device 60 is designed as an exhaust gas turbocharger device. The turbocharger device 60 has two turbocharger units 62, 64, wherein a first turbocharger unit 62 is assigned to the first air supply tract 32 and the first exhaust tract 52, and a second turbocharger unit 64 is assigned to the second air supply tract 34 and the second exhaust tract 54. Each turbocharger device 62, 64 has a compressor 621, 641, a turbine 622, 642, and an electric motor 623, 643. The turbines 622, 642 are driven by the exhaust gas which flows around the associated combustion chambers 201, 202, 203, 204, 205, 206 of the cylinder banks 22.Compressors 621, 641 are each connected in a rotationally fixed manner to the associated turbine 622, 642 via a turbocharger shaft 624, 644, so that compressors 621, 641 rotate together with turbines 622, 642. The rotation of compressors 621, 641 compresses the air flowing through air supply ducts 321, 341. The compressed air is cooled in cooler 40. Furthermore, the compressed air from air supply ducts 32, 34 mixes in an air plenum 42, which in this case is formed by cooler 40, in which a fluidic coupling of air supply ducts 32, 34 is present. Starting from the cooler 40, the compressed, mixed and cooled air can flow via the air lines 36, 38 to the corresponding cylinder banks 22, 24, wherein the air mass flow to the individual cylinder banks 22, 24 is adjusted by the throttle valves 361, 381.

[0032] The electric motors 623, 643 each have a stator 631, 651 and a rotor 632, 652, wherein the stator 631, 651 is mounted fixedly to the housing and the rotor 632, 652 is rotationally fixedly connected to the turbocharger shaft 624, 644. The electric motors 623, 643 are electrically connected to a control unit 70, so that the electric motors 623, 643 are controlled by the control unit 70.

[0033] During operation of the engine system 10, the air mass flows emanating from the individual compressors 621, 641 depend, on the one hand, on the drive power generated by the turbine 622, 642 and, on the other hand, on the drive power generated by the electric motors 623, 643. The drive power emanating from the turbines 622, 642 depends on the exhaust gas mass flows flowing around and driving the turbine 622, 642. By appropriately controlling the electric motors 623, 643, the target air mass flow required for the operation of the combustion engine 20 can be specifically adjusted. In this case, the compressor 621, 641 can be accelerated or decelerated by the electric motor 623, 643 relative to the turbine 622, 642, whereby the electric motor 623, 643 is in recuperation mode during deceleration.

[0034] Furthermore, the engine system 10 comprises a sensor device 44 with a pressure sensor 46, wherein the pressure sensor 46 detects the pressure in the air collection chamber 42.

[0035] Fig. 2a, Fig. 2b and Fig. 2c show the pressure curves p s , p m , the speeds n s , n lst , n m of the electric motors 623, 623 and the electrical power P1, P2 of the electric motors 623, 643, wherein such curves occur when there is a boost pressure control and a speed control of the electric motors 623, 643.

[0036] In Fig. 2a the solid line shows a target pressure curve p s , which is determined based on the driver's input, for example, the accelerator pedal position. The dashed-dotted line shows a curve of the measured pressure p m in the air collection chamber 42, which results from the sensor signals of the pressure sensor 44.

[0037] Fig. 2b shows a speed-time curve of the electric motors 623, 643 and thus also of the compressors 621, 641. The solid line represents the target speed n S of the rotors 632, 652 of the electric motors 623, 643. The dashed line shows the actual speed n lst of the rotors 632, 652, The dash-dot line shows the pressure p m determined modeled speed n m the rotors 632, 652 of the electric motors 623, 643.

[0038] Fig. Figure 2c shows an electrical power-time curve of the electric motors 623, 643. The solid line represents the curve of the electrical power P1 of the first electric motor 623. The dashed line represents the curve of the electrical power P2 of the second electric motor 643.

[0039] The operation of the engine system 10 is basically pressure-controlled, whereby depending on the driver's request, a pressure required for the operation of the combustion engine 10, Fig. 2a shown target boost pressure p s This boost pressure is provided by controlling the electric motors 623, 643 in such a way that the target boost pressure p s by the rotation of the compressors 621, 641 with a Fig. 2b shown target speed n s is provided, wherein the electric motors 623, 643 are speed-controlled, so that the Fig. 2b shown actual speed n lst to the target speed n s The boost pressure is controlled in such a way that the actual Fig. 2a shown pressure p m , which is determined by the pressure sensor 44, to the target pressure p s is adjusted in such a way that the control and thus the speed n lst to the target speed ns is adjusted.

[0040] The problem is that there is a risk that an unnoticed unstable operation, in particular a flow stall, of one of the compressors 623, 643 may occur. Fig. 2a, Fig. 2b, Fig. 2c, this condition exists at time t1. Here, the pressure in the air collection chamber 42, as determined by the pressure sensor 44, drops, and due to the boost pressure control, the pressure determined by the speed n s the compressors 621, 641 are increased. In this case, the compressor 641, which is operating in unstable mode, is decelerated by the electric motor 643, since the exhaust gases flowing around the turbine 642 would cause the compressor 641 to accelerate to a higher speed, since the flow separation creates virtually no resistance and also a flow rate. On the other hand, the compressor 621, operating in stable mode, is accelerated by the electric motor 623.

[0041] In order to detect the unstable operation of one of the two compressors 621, 641, a modeled speed n is calculated from the sensor signal of the pressure sensor 46 using a model. m the compressor is determined and compared with the actual speeds n lst the compressor is calibrated. As in Fig. 2b, there is a speed difference value Δn between the actual speed n lst and the modeled speed n mof the electric motors 621, 641. As soon as the speed difference value Δn exceeds a speed difference threshold, it is detected that one of the compressors 621, 641, in this case compressor 641, is operating in unstable mode. In parallel, the electrical powers P1, P2 of the electric motors 623, 643 are compared with each other, and a resulting power difference value is determined. In this case, the power difference value exceeds a predefined power difference threshold, which also detects unstable operation of one of the compressors 621, 641. This provides redundant detection of unstable operation of the compressors 621, 641.

[0042] To correct the unstable operation of one of the compressors 621, 641, the electric motors 623, 643 are controlled in such a way that the electrical powers P1, P2 of the electric motors 623, 643 are equalized, thereby returning the electric motor 623, 643 running in unstable operation to stable operation. In particular, the electrical power P1 of the electric motor 623 is reduced to the electrical power P2 of the electric motor 643.

Claims

[1] Engine system of a motor vehicle, with an internal combustion engine (20) having a plurality of combustion chambers (201, 202, 203, 204, 205, 206) into which air can be introduced via an air supply system (30), wherein exhaust gases can be discharged from the combustion chambers (201, 202, 203, 204, 205, 206) via an exhaust system (50) which is fluidically connectable to the combustion chambers (201, 202, 203, 204, 205, 206), a turbocharger device (60) comprising a first turbocharger unit (62) and a second turbocharger unit (64), each of which has at least one compressor (621, 641) and an electric motor (623, 643) which can be connected to the compressor (621, 641) in a torque-transmitting manner wherein the turbocharger units (62, 64) are fluidly connected on the compressor side to a common air collection chamber (42) of the air supply system (30), a sensor device (44) having a pressure sensor (46) designed to detect the pressure in the air collection chamber (42), a control unit (70) designed to control the electric motors (623, 643) of the turbocharger units (62, 64), characterized by , that the control unit (70) is designed to model a speed (n m ) of the electric motors (623, 643) of the turbocharger units (62, 64) based on the sensor signal of the pressure sensor (46), the modeled speed (n m ) each with an actual speed (n ist) to adjust at least one of the electric motors (623, 643) and to determine a speed difference value and / or to adjust the electrical powers (P1, P2) of the electric motors (623, 643) with one another and to determine a power difference value, wherein if a predefined speed difference threshold value is exceeded by the speed difference value and / or if a predefined power difference threshold value is exceeded by the power difference value, it is concluded that one of the compressors (621, 641) is operating unstably. [2] Engine system of a motor vehicle, with an internal combustion engine (20) having a plurality of combustion chambers (201, 202, 203, 204, 205, 206) into which air can be introduced via an air supply system (30), wherein exhaust gases can be discharged from the combustion chambers (201, 202, 203, 204, 205, 206) via an exhaust system (50) which is fluidically connectable to the combustion chambers (201, 202, 203, 204, 205, 206), a turbocharger device (60) comprising a first turbocharger unit (62) and a second turbocharger unit (64), each of which has at least one compressor (621, 641) and an electric motor (623, 643) which can be connected to the compressor (621, 641) in a torque-transmitting manner wherein the turbocharger units (62, 64) are fluidly connected on the compressor side to a common air collection chamber (42) of the air supply system (30), a sensor device (44) designed to determine the air flow characteristics and / or the operating characteristics of the turbocharger units (62, 64), a control unit (70) which is designed to control the electric motors (623, 643) of the turbocharger units (62, 64), characterized by , that the control unit (70) is designed to detect an operation of one of the compressors (621, 641) in an unstable mode from the sensor signals of the sensor device (44) and, based thereon, to adjust the electrical powers (P1, P2) of the electric motors (623, 643) to one another. [3] Engine system according to claim 1 or 2, characterized by in that the turbocharger device (60) is an exhaust gas turbocharger device, wherein each turbocharger unit (62, 64) has a turbine (622, 642) which is connected to the compressor (621, 641) in a torque-transmitting manner via a turbocharger shaft (624, 644) and which is fluidically connected to the exhaust system (50), wherein a rotor (632, 652) of the electric motor (623, 643) is connected in a rotationally fixed manner to the turbocharger shaft (624, 644). [4] Engine system according to one of the preceding claims, characterized by that the control unit (70) is designed such that the electric motors (623, 643) are speed-controlled. [5] Engine system according to one of the preceding claims, characterized by that the control unit (70) is designed such that the turbocharger units (62, 64) are pressure-controlled. [6] Engine system according to one of the preceding claims, characterized by that the air supply system (30) has a cooler (40) which has the air collection chamber (42).

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