Method for operating a drive unit for a motor vehicle, corresponding drive unit for a motor vehicle and computer program product

Abstract

The invention relates to a method for operating a drive unit (1) for a motor vehicle, which has an exhaust-generating drive unit, an exhaust system (2) that discharges the exhaust gas towards the outside environment of the motor vehicle, and an iris diaphragm (3) arranged for adjusting the flow cross-section for the exhaust gas in the exhaust system (2). The iris diaphragm (3) is arranged in an end pipe (6) of the exhaust system (2), through which the exhaust system (2) discharges into the outside environment, and is controlled to adjust the flow cross-section to a preset value determined as a function of an operating parameter of the drive unit (1). The invention further relates to a drive unit (1) for a motor vehicle and a computer program.

Description

[0001] The invention relates to a method for operating a drive unit for a motor vehicle, which comprises an exhaust-generating drive unit, an exhaust system that discharges the exhaust gas towards the outside environment of the motor vehicle, and an iris diaphragm arranged in the exhaust system for adjusting the flow cross-section for the exhaust gas. The invention further relates to a drive unit for a motor vehicle and a computer program product.

[0002] For example, German patent application DE 10 2018 120 195 A1 is known from the prior art. This describes an exhaust aftertreatment system for an internal combustion engine, comprising an exhaust system with an exhaust duct in which at least one exhaust aftertreatment component is arranged. It is provided that a device for temporarily changing the flow cross-section of the exhaust duct is arranged downstream of an exhaust manifold of the internal combustion engine and upstream of the first exhaust aftertreatment component in the direction of exhaust gas flow through the exhaust duct, or downstream of the first exhaust aftertreatment component.

[0003] Furthermore, German patent application DE 10 2016 011 149 A1 discloses an exhaust system for an internal combustion engine, comprising an exhaust aftertreatment device through which exhaust gas from the internal combustion engine flows, and which has at least one catalytically active aftertreatment element through which exhaust gas flows to effect and / or support at least one chemical reaction. At least one actuating device is provided by means of which at least one flow cross-section arranged upstream of the aftertreatment element and through which exhaust gas flows, and through which the exhaust gas can be supplied to the aftertreatment element, can be adjusted depending on the temperature and / or the mass flow rate of the exhaust gas.

[0004] Furthermore, German patent application DE 10 2013 204 401 A1 discloses an exhaust aftertreatment system for an internal combustion engine, comprising an exhaust stream in which an oxidation catalyst is arranged. This catalyst includes a coated carrier body with an upstream end face and an downstream end face. The oxidation catalyst has an adjustment device for influencing the velocity of the exhaust gas flowing through the carrier body. Additionally, a control device is provided that is operatively connected to the adjustment device for influencing the velocity within the carrier body. The adjustment device is provided to include at least one cover with which at least one end face of the carrier body can be variably covered to change the cross-sectional area of ​​the passage, and the control device is designed to control and / or regulate the velocity.

[0005] The object of the invention is to propose a method for operating a drive unit for a motor vehicle which has advantages over known methods, in particular ensuring an excellent visual appearance of the motor vehicle and / or enabling effective adjustment of the operating noise of the drive unit.

[0006] According to the invention, this is achieved by a method for operating a drive unit for a motor vehicle with the features of claim 1. It is provided that the iris diaphragm is arranged in an exhaust pipe through which the exhaust system opens into the outside environment, and is controlled to adjust the flow cross-section to a preset value determined as a function of an operating parameter of the drive unit.

[0007] Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments described in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are possible.

[0008] The method is designed for operating the drive system. It is preferably implemented by means of a control unit for the drive system. The drive system or its control unit is preferably an integral part of the motor vehicle, but can of course also be separate from it, particularly until the drive system or the control unit is mounted on or in the motor vehicle. The drive system serves to propel the motor vehicle, i.e., to provide a drive torque directed towards propelling the motor vehicle. The drive unit comprises the drive system to provide the drive torque. The drive unit is preferably an internal combustion engine, in particular a gasoline engine or a diesel engine.

[0009] During operation, the drive unit is supplied with fuel and fresh gas at least intermittently, with the fresh gas containing fresh air at least intermittently. Additionally, the fresh gas may contain exhaust gas if exhaust gas recirculation is implemented, in which the exhaust gas generated by the drive unit is at least partially returned to the drive unit as a component of the fresh gas. The fuel and fresh gas supplied to the drive unit form a fuel-fresh gas mixture with a specific composition, which is then reacted within the drive unit.

[0010] During operation of the engine, exhaust gas is produced due to the chemical reaction of fuel and fresh air. This exhaust gas is discharged towards the outside environment of the engine or vehicle. This discharge is accomplished via the exhaust system. The exhaust system is connected to the engine via a flow path, ensuring that the exhaust gas generated by the engine is fed into it, and in particular, that it is completely discharged. It also discharges into the outside environment via the tailpipe. Thus, the exhaust gas generated by the engine flows out into the outside environment through the tailpipe.

[0011] From a fluid dynamics perspective, an exhaust pipe is preferably present between the engine and the tailpipe. This pipe is, for example, fluidically connected on one side to the engine, specifically to an exhaust manifold and / or a downpipe of the engine, and on the other side to the tailpipe. Preferably, the exhaust pipe extends from the engine, in particular from the exhaust manifold and / or the downpipe, to the tailpipe.

[0012] Since the exhaust gas produced by the engine contains pollutants, it is preferably first routed to an exhaust aftertreatment system before being released into the environment. In this system, the pollutants are at least partially converted into less harmful products. Only after passing through the exhaust aftertreatment system is the exhaust gas released into the environment, namely through the exhaust pipe of the engine.

[0013] The exhaust aftertreatment system is preferably designed as a vehicle catalyst, in particular as a three-way catalyst, oxidation catalyst, NO x -storage catalyst or SCR catalyst, or at least has one. It may be designed so that the vehicle catalyst is integrated into a particulate filter, in particular a gasoline particulate filter or a diesel particulate filter. For this purpose, the particulate filter is, for example, provided with a catalytic coating.

[0014] Preferably, the exhaust aftertreatment system comprises several components, for example, at least one catalytic converter and at least one particulate filter. However, it is also possible for the exhaust aftertreatment system to have multiple catalytic converters and / or multiple particulate filters. In any case, the exhaust aftertreatment system is arranged fluid-wise between the engine and the tailpipe, so that the exhaust gas treated by the exhaust aftertreatment system flows out into the outside environment through the tailpipe.

[0015] For example, it is planned to arrange an iris diaphragm between the drive unit and the tailpipe, and in particular between the drive unit and the exhaust aftertreatment system, to adjust the cross-sectional area available for the exhaust gas flow. By adjusting the cross-sectional area, the exhaust gas flow rate through the aftertreatment system and / or an exhaust gas turbocharger can be set or influenced. This can be achieved by maintaining a specific velocity within the aftertreatment system, thereby enabling a desired conversion rate for a component contained in the exhaust gas.

[0016] However, the applicant has determined that the iris diaphragm can also be used advantageously at another point in the exhaust system. According to the invention, the iris diaphragm is arranged in the exhaust system's tailpipe, through which the exhaust system flows into the outside environment. This means that, from a fluid dynamics perspective, the iris diaphragm has a comparatively small distance to the outside environment, so that the exhaust gas flows directly, or at least almost directly, out of the tailpipe after passing through the iris diaphragm and enters the outside environment.

[0017] For example, the distance of the iris diaphragm from the outlet opening through which the tailpipe enters the external environment is greater than the inner diameter of the tailpipe away from the iris diaphragm by a factor of at most six, at most four, or at most two. Preferably, the distance of the iris diaphragm from the outlet opening is at most equal to, or even smaller than, the inner diameter of the tailpipe away from the iris diaphragm.

[0018] With such an arrangement of the iris diaphragm, the exhaust jet flowing into the outside environment can be directly adjusted using the iris diaphragm. This adjustment is achieved, for example, by reducing the chimney effect in the area of ​​a vehicle's bumper, so that the exhaust gas exiting the tailpipe flows continuously away from the vehicle and is not deflected towards the vehicle, and in particular, does not flow towards the vehicle's bumper.

[0019] Such an airflow can lead to thermally induced damage and / or deformation of the bumper, especially if it is made of plastic. The iris diaphragm ensures and, above all, maintains the vehicle's excellent visual condition by reducing the impact of exhaust gases on the bumper. Additionally or alternatively, the iris diaphragm can be used to adjust the exhaust gas flow and thus the operating noise of the drive system. Specifically, the iris diaphragm is controlled to adjust the back pressure for the tailpipe, resulting in the desired operating noise.

[0020] In any case, the iris diaphragm described here is located downstream of the exhaust aftertreatment system, so that it is exclusively permeated by exhaust gas that has previously passed through the exhaust aftertreatment system. No further exhaust aftertreatment system is arranged downstream of the iris diaphragm in the direction of exhaust gas flow; in particular, the cross-sectional area available for the exhaust gas flow from the iris diaphragm to the tailpipe outlet is preferably constant throughout.

[0021] This means that the exhaust jet exiting the tailpipe opening is directly influenced by the iris diaphragm, particularly with regard to its shape, direction, and / or exhaust flow rate. Exhaust flow rate, in this context, refers to the quantity of exhaust gas per unit of time, for example, exhaust mass per unit of time (i.e., exhaust mass flow rate) or exhaust volume per unit of time (i.e., exhaust volume flow rate).

[0022] In addition to the iris diaphragm described here, another cross-sectional adjustment device can, of course, be present in the exhaust system, namely upstream of the iris diaphragm. This cross-sectional adjustment device can also be designed as an iris diaphragm. For example, the cross-sectional adjustment device is located upstream of the exhaust aftertreatment system and / or the exhaust gas turbocharger in the exhaust pipe. Analogous to the iris diaphragm, the cross-sectional adjustment device serves to set a flow cross-section for the exhaust gas. In particular, it is intended that the flow cross-sections set using the cross-sectional adjustment device and the iris diaphragm can be selected independently of each other. This allows for particularly precise control of the exhaust gas flow.

[0023] A further development of the invention provides that the flow cross-section is adjusted by means of an electrical and / or pneumatic actuator connected to the iris diaphragm. The actuator is connected to the iris diaphragm; for example, it is a rotary actuator, thus causing a rotary movement of an actuating element of the iris diaphragm. The actuating element is preferably connected to lamellae of the iris diaphragm, the rotational angles of which depend on the position of the actuating element. By operating the actuator, the flow cross-section of the iris diaphragm can be adjusted. The flow cross-section refers in particular to the cross-sectional area and / or shape of the flow cross-section. The advantages already mentioned are achieved with the described procedure.

[0024] A further development of the invention provides that at least one of the following parameters is used as an operating parameter: rotational speed of the drive unit, drive torque of the drive unit, exhaust gas flow rate, exhaust gas temperature, and exhaust gas composition. It is possible to use only one of the aforementioned parameters as an operating parameter. However, it is preferred that several or even all of the aforementioned parameters are used to determine the setpoint value. The term "rotational speed" refers to the instantaneous rotational speed of the drive unit, and the term "drive torque" refers to the torque currently provided by the drive unit.

[0025] The exhaust gas flow rate describes the amount of exhaust gas passing through the exhaust system or the iris diaphragm per unit of time and is expressed, for example, as a mass flow rate or a volume flow rate. The exhaust gas temperature is the instantaneous temperature of the exhaust gas, which is measured, for example, using a temperature sensor. The exhaust gas temperature can be measured at any point in the exhaust system; for example, it is determined upstream of the iris diaphragm, preferably downstream of the exhaust aftertreatment system and / or the exhaust gas turbocharger.

[0026] The exhaust gas composition can be used as a further parameter. This describes the proportion of at least one exhaust gas component in the exhaust gas produced by the engine. For example, the exhaust gas composition corresponds to the composition of the exhaust gas produced by the engine. The components of the exhaust gas produced by the engine are also referred to as raw emissions. Raw emissions describe the composition of the exhaust gas upstream of the exhaust aftertreatment system, or, in terms of flow dynamics, between the engine and the exhaust aftertreatment system. By using the aforementioned parameters to determine the target value to which the flow cross-section is adjusted by appropriately setting the iris diaphragm, the advantages already mentioned are achieved.

[0027] A further development of the invention provides that the flow cross-section is adjusted such that identical exhaust gas flow velocities are present in the iris diaphragm at different exhaust gas flow rates, in particular at least two different exhaust gas flow rates. With this approach, the iris diaphragm ensures that, despite different exhaust gas flow rates, the exhaust gas exits the tailpipe into the outside environment at the same or at least similar flow velocities.

[0028] For example, the flow cross-section is chosen to be smaller for a lower exhaust gas flow rate than for a higher exhaust gas flow rate. In particular, it is intended to apply the described procedure for at least two different exhaust gas flow rates; however, it is especially preferred to use it for all exhaust gas flow rates occurring during normal operation of the drive unit, so that the flow velocity of the exhaust gas is kept constant or at least substantially constant with the aid of the iris diaphragm. The advantages explained above are also achieved with this procedure.

[0029] A further development of the invention provides that the actuating speed used to adjust the flow cross-section is limited to a maximum actuating speed that is lower than a nominal actuating speed achievable with the actuator. The actuating speed is understood to be the speed at which the flow cross-section is adjusted. For example, the actuating speed is specified as an area per unit of time, i.e., for example, in mm². 2 / s. The actuator enables the iris diaphragm to be adjusted at the nominal adjustment speed, which corresponds to the highest possible adjustment speed of the iris diaphragm using the actuator.

[0030] The flow cross-section is to be adjusted at a speed lower than the nominal speed. For this purpose, a maximum speed is determined that is lower than the nominal speed. For example, the maximum speed is at most 75%, 50%, or 25% of the nominal speed. The speed used to adjust the flow cross-section is limited to this maximum speed when approaching higher speeds, meaning that the adjustment speed is at most equal to or less than the maximum speed. This approach prevents abrupt changes in the flow cross-section and the resulting disruptive effects, such as undesirable changes in the operating noise of the drive unit.

[0031] A further development of the invention provides that an operating mode of the drive device can be set by a user of the motor vehicle, wherein the default value is determined when setting a first operating mode based on a first implementation rule and / or from a first of the parameters, and when setting a second operating mode different from the first operating mode based on a second implementation rule different from the first implementation rule and / or from a second of the parameters different from the first parameter.

[0032] The operating mode is set, for example, using a control element located in the vehicle's interior or at least accessible from within it. This control element might be a button, a switch, a touchscreen, or something similar. For instance, the control element allows the setting of at least the first and second operating modes.

[0033] If the first operating mode is selected using the control element, the first implementation rule and / or the first parameter are used to determine the default value. If, however, the second operating mode is selected, the default value is determined based on the second implementation rule and / or the second parameter. This procedure allows the user to influence the operation of the iris diaphragm.

[0034] For example, the implementation specifications and / or parameters differ in such a way that different operating noises of the drive unit are achieved in the different operating modes at the same operating point. The operating point is characterized in particular by the rotational speed and / or the drive torque. In any case, the user is given extensive influence over the operation of the drive unit.

[0035] For example, different values ​​are obtained for at least one parameter in the different operating modes, even at the same operating point. This at least one parameter could be, for example, one of the following: exhaust back pressure, flow velocity, or resonance. Exhaust back pressure is the pressure of the exhaust gas upstream of the iris diaphragm, specifically the static pressure. Flow velocity is the speed at which the exhaust gas flows through the iris diaphragm. Resonance describes the resonant behavior of the exhaust system.

[0036] For example, it can be provided that in a first operating mode, a first value of the parameter is available, and in a second operating mode, a second value of the parameter, different from the first, is available at the same operating point. The values ​​of the operating modes can be parameterized, in particular by the user of the vehicle. For this purpose, a control element is preferably provided by means of which the user can influence the values.

[0037] In particular, the first operating mode has a lower exhaust back pressure than the second. Therefore, the first operating mode produces a more dynamic, powerful sound, while the second operating mode produces a quieter, more subdued sound. Additionally or alternatively, in the first operating mode, the first value of the flow velocity is selected to achieve the more dynamic, powerful sound; in the second operating mode, the second value is selected to achieve the quieter, more subdued sound. Optionally, the same procedure is applied to the first and second values ​​of the resonance.

[0038] A further development of the invention provides that an iris diaphragm is used which has adjustable blades made of titanium and / or ceramic for setting the flow cross-section. The blades serve to adjust the flow cross-section and are mounted for this purpose in a movable manner. They are each connected to the actuator via a drive mechanism. To ensure high temperature resistance of the blades and thus reliable function of the iris diaphragm, the blades are made of titanium and / or ceramic or consist of one of these materials. It is therefore possible for the blades to be solid and made entirely of one of the aforementioned materials. However, it is also possible for each blade to have a coating of one of the aforementioned materials to ensure its temperature resistance. The use of these materials enables a long service life for the iris diaphragm.

[0039] A further development of the invention provides for the use of an iris diaphragm whose longitudinal center axis is angled relative to a longitudinal center axis of the tailpipe. This means that the longitudinal center axis of the iris diaphragm and the longitudinal center axis of the tailpipe form an angle with each other which is greater than 0° and less than 180°. Preferably, the angle is at least 5° and at most 30°, at least 7.5° and at most 20°, or at least 10° and at most 15°.

[0040] Angled relative to the longitudinal axis of the tailpipe, and thus also relative to the main exhaust flow direction, the iris diaphragm deflects the exhaust gas depending on the set flow cross-section, thereby directing the exhaust jet. Specifically, the iris diaphragm is angled such that the exhaust jet is deflected away from the vehicle's bumper. This effectively prevents adverse effects of the exhaust gas on the vehicle, particularly on its body and bumper.

[0041] The invention further relates to a drive unit for a motor vehicle, in particular for carrying out the method as explained in this description, wherein the drive unit comprises an exhaust gas-generating drive unit, an exhaust system that discharges the exhaust gas towards the outside environment of the motor vehicle, and an iris diaphragm arranged in the exhaust system for adjusting the flow cross-section for the exhaust gas. It is provided that the iris diaphragm is arranged in an end pipe of the exhaust system through which the exhaust system discharges into the outside environment, and that the drive unit is designed and configured to control the iris diaphragm to adjust the flow cross-section to a preset value determined as a function of an operating parameter of the drive unit.

[0042] The advantages of such a drive system design and such a procedure have already been mentioned. Both the drive system and the method for operating it may be further developed as explained in this description, and reference is made to those explanations.

[0043] Furthermore, the invention relates to a computer program product comprising commands that cause the drive device to execute the described method as described herein. For the advantages and possible advantageous embodiments, reference is made to the description in its entirety.

[0044] The features and combinations of features described in the description, in particular those described in the following figure description and / or shown in the figures, are not only usable in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention, in particular the scope of the claims. Thus, embodiments that are not explicitly shown or explained in the description and / or the figures, but which emerge from or can be derived from the explained embodiments, particularly within the scope of the claims, are also to be considered as encompassed by the invention.

[0045] The invention is explained in more detail below with reference to the exemplary embodiments shown in the description, without limiting the invention. The only embodiment shown is... Fig. 1 A schematic representation of a section of a drive unit for a motor vehicle, namely an iris diaphragm arranged in an exhaust system of the drive unit, which is adjustable by means of an actuator.

[0046] The Fig. Figure 1 shows a schematic representation of a section of a drive unit 1 for a motor vehicle. More precisely, it shows a section of an exhaust system 2, through which exhaust gas from a drive unit is discharged towards the outside environment. The exhaust system 2 includes a cross-sectional adjustment device, designed as an iris diaphragm 3. The iris diaphragm 3 is characterized by several lamellae 4, of which only a few are shown here as examples. The lamellae 4 are adjustable by means of an actuating element 5.

[0047] The iris diaphragm 3 is arranged in an end tube 6, which is only indicated here. The actuating element 5 can be controlled using an actuator 7, which is only shown here as an example, namely to set or adjust the flow cross-section of the iris diaphragm 3. The actuator 7 is electrically connected to a control unit 8, which determines a setpoint value for the flow cross-section depending on an operating parameter of the drive unit and controls the actuator 7 to adjust the iris diaphragm 3 to the setpoint value.

[0048] The described drive unit 1 has the advantage that the flow cross-section can be adjusted with fine precision. Preferably, the adjustment speed of the iris diaphragm 3 is limited, so that it is adjusted more slowly than would actually be possible using the actuator 7. This prevents any undesirable influence on the operation of the drive unit 1 caused by changes in the flow cross-section. REFERENCE MARK LIST: 1 Drive unit 2 Exhaust system 3 Iris diaphragm 4 slats 5 Actuator 6 tailpipe 7 Actuator 8 Control unit QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2018 120 195 A1

[0002] DE 10 2016 011 149 A1

[0003] DE 10 2013 204 401 A1

[0004]

Claims

[1] Method for operating a drive unit (1) for a motor vehicle, which has an exhaust gas generating drive unit, an exhaust system (2) which discharges the exhaust gas towards an outside environment of the motor vehicle and an iris diaphragm (3) arranged for adjusting a flow cross-section for the exhaust gas in the exhaust system (2), characterized by , that the iris diaphragm (3) is arranged in an end pipe (6) of the exhaust system (2), through which the exhaust system (2) flows into the outside environment, and is controlled to adjust the flow cross-section to a preset value determined as a function of an operating parameter of the drive unit (1). [2] Method according to claim 1, characterized by , that the flow cross-section is adjusted by means of an electrical and / or pneumatic actuator (7) connected to the iris diaphragm (3) for drive purposes. [3] Method according to any one of the preceding claims, characterized by , that at least one of the following parameters is changed as an operating parameter: speed of the drive unit, drive torque of the drive unit, exhaust gas flow rate, exhaust gas temperature and exhaust gas composition. [4] Method according to any one of the preceding claims, characterized by , that the flow cross-section is adjusted such that identical flow velocities of the exhaust gas are present in the iris diaphragm (3) for different exhaust gas flow rates. [5] Method according to any one of the preceding claims, characterized by , that a control speed used in adjusting the flow cross-section is limited to a maximum control speed which is less than a nominal control speed achievable using the actuator (7). [6] Method according to any one of the preceding claims, characterized by, that an operating mode of the drive device (1) is adjustable by a user of the motor vehicle, wherein the default value is determined when setting a first operating mode on the basis of a first implementation rule and / or from a first of the parameters and when setting a second operating mode different from the first operating mode on the basis of a second implementation rule different from the first implementation rule and / or from a second of the parameters different from the first parameter. [7] Method according to any one of the preceding claims, characterized by , that an iris diaphragm (3) is used which has adjustable blades (4) made of titanium and / or ceramic for adjusting the flow cross-section. [8] Method according to any one of the preceding claims, characterized by , that an iris diaphragm (3) is used, the longitudinal central axis of which is angled relative to a longitudinal central axis of the end tube (6). [9] Drive unit (1) for a motor vehicle, in particular for carrying out the method according to one or more of the preceding claims, wherein the drive unit (1) has an exhaust gas generating drive unit, an exhaust system (2) which discharges the exhaust gas towards an outside environment of the motor vehicle and an iris diaphragm (3) arranged for adjusting a flow cross-section for the exhaust gas in the exhaust system (2), characterized by , that the iris diaphragm (3) is arranged in an end pipe (6) of the exhaust system (2) through which the exhaust system (2) flows into the outside environment, and that the drive device (1) is provided and designed to control the iris diaphragm (3) to adjust the flow cross-section to a preset value determined as a function of an operating parameter of the drive device (1). [10] Computer program product comprising instructions that cause the drive device (1) according to claim 9 to execute the method according to one or more of claims 1 to 8.

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