Method and device for operating turbocharger, in particular rolling-supported turbocharger, for internal combustion engine

Abstract

The invention relates to a method for operating a turbocharger (110), in particular a rolling-supported turbocharger (110), for an internal combustion engine (102). The method comprises a step of setting a target boost pressure (125) of the turbocharger (110) in dependence on a relationship of a compressor speed required for the turbocharger (110) as a function of a target torque (105) of the internal combustion engine (102) with respect to at least one critical resonant speed range. The resonant speed range includes a resonant speed of the turbocharger (110), where vibrational excitation of the turbocharger (110) occurs with its resonant frequency. The resonance rotation speed range is limited by a lower critical threshold rotation speed and an upper critical threshold rotation speed.

Description

Technical Field

[0001] The invention relates to a method for operating a turbocharger, in particular a rolling bearing, for an internal combustion engine and a device for operating a turbocharger, in particular a rolling bearing, for an internal combustion engine according to the independent claims. A computer program is also a subject of the invention. Background Art

[0002] With regard to the operation of turbochargers taking into account their natural frequencies, in particular those of rolling bearings, there are conventional solutions, for example, which are based on design changes or on a shifting of the resonance frequency into a safe range. Summary of the invention

[0003] Against this background, the solution proposed here presents a method for operating a turbocharger, in particular a rolling bearing, for an internal combustion engine, according to the independent claim, furthermore a device for using this method and finally a corresponding computer program. Advantageous developments and improvements of the device described in the independent claim can be achieved by the measures listed in the dependent claims.

[0004] According to the embodiment, in particular, critical resonant speed ranges during the operation of an exhaust gas turbocharger, which is particularly supported by rolling bearings, can be avoided. In particular, the calculation of the rated values ​​for boost pressure regulation can be optimized in order to bypass specific speed ranges of the exhaust gas turbocharger in a targeted manner. In this case, for example, the natural frequency of the exhaust gas turbocharger unit can be taken into account when calculating the rated values. As a result, in particular when using a turbocharger, which is particularly supported by rolling bearings, at low temperatures, critical operating conditions with high amplitudes in the resonant range can be prevented. As a result, safe operation of an exhaust gas turbocharger on an internal combustion engine can be achieved, wherein the turbocharger should be operated above and below its natural frequency speed during design or so-called matching (Matchings), but should not be operated stably within the natural frequency range.

[0005] A method for operating a turbocharger, in particular a rolling bearing turbocharger, for an internal combustion engine is described, the method comprising the following steps:

[0006] The setpoint boost pressure of the turbocharger is set as a function of the compressor speed for the turbocharger required according to the setpoint torque of the internal combustion engine relative to at least one critical resonant speed range, the critical resonant speed range including the resonant speed of the turbocharger, in which the vibration excitation of the turbocharger occurs at its resonant frequency, wherein the resonant speed range is limited by a lower critical threshold speed and an upper critical threshold speed. In other words, the critical resonant speed range includes the resonant speed at which the vibration excitation of the turbocharger occurs at its resonant frequency.

[0007] The turbocharger can also be referred to as an exhaust gas turbocharger. The internal combustion engine can be configured for a motor vehicle. The motor vehicle can be a car, a commercial vehicle, etc. The rated boost pressure can be a rated value of a boost pressure that should be caused by a turbocharger for an internal combustion engine. The relationship can be a mathematical relationship, in particular a magnitude and a numerical value and can be a variation curve of the required compressor speed relative to at least one critical resonant speed range as a supplement or alternative. The resonant frequency can also be referred to as a natural frequency. By executing the setting step, the boost pressure regulation can be implemented as a control loop with at least partial hysteresis characteristics, in particular a closed-loop control loop.

[0008] According to one embodiment, in the setting step, the setpoint charge pressure can be adjusted to a value which, when the required compressor speed rises to a lower critical threshold speed, results in operation of the turbocharger at an upper critical threshold speed. Such an embodiment offers the advantage that, in order to avoid a critical resonant speed range when operating, in particular, a rolling-supported exhaust gas turbocharger, when approaching the lower critical speed threshold, the setpoint charge pressure can be increased in such a way that the critical resonant speed range is quickly passed upward.

[0009] In the setting step, the set charge pressure can also be adjusted to a value that causes the turbocharger to operate with an upper critical threshold speed when the required compressor speed drops to an upper critical threshold speed and until the required compressor speed reaches a lower critical threshold speed; and to a value that causes the turbocharger to operate with a lower critical threshold speed when the required compressor speed drops to a lower critical threshold. That is, in other words, the set charge pressure is always adjusted to a value that causes the turbocharger to operate with an upper critical threshold speed until the required compressor speed drops to a lower critical threshold speed. Such an embodiment provides the advantage that, in order to avoid a critical resonant speed range when operating an exhaust gas turbocharger that is particularly roller-supported when approaching an upper critical threshold speed, the set charge pressure is first kept constant until the critical resonant speed range can be quickly passed downward.

[0010] Furthermore, the method can have a step of reading in a setpoint torque of the internal combustion engine and, as a supplement or alternative, a step of reading in an actual value of at least one controlled variable for the turbocharger, in order to set a setpoint boost pressure of the turbocharger taking into account the read-in actual value of the at least one controlled variable. The at least one read-in controlled variable can be an actual boost pressure, an actual rotational speed or an actual compressor rotational speed and / or similar variables. Such an embodiment offers the advantage that a current data basis for the operation of the turbocharger can be reliably available.

[0011] In addition, the method can have a step for generating a control signal for controlling the compressor of the turbocharger while using the set boost pressure set in the setting step. In other words, a control signal for controlling the compressor of the turbocharger is generated in the generating step while using the set boost pressure set in the setting step. The compressor can be operated at a speed caused by the set boost pressure or compressor speed while using the control signal. Such an embodiment provides the advantage that the turbocharger can be safely and reliably operated by such a control of the compressor while avoiding a critical resonant speed range.

[0012] According to one embodiment, a compressor characteristic curve that establishes a relationship between a set pressure ratio, a set mass flow and a compressor speed of the turbocharger can be used in the setting step to determine the set boost pressure. In this case, the set mass flow and the set pressure ratio are determined based on the set torque of the internal combustion engine, in particular based on the set torque of the internal combustion engine or derived from the set torque of the internal combustion engine. The pressure ratio can include a set pressure on the inlet side or a set pressure at the inlet valve of the internal combustion engine. Such an embodiment offers the advantage that the set boost pressure can be determined in a simple and precise manner so that it is available in the setting step.

[0013] In this case, the compressor characteristic curve can be inverted so that the rated pressure ratio can be described using the compressor speed and the rated mass flow. In this case, the inverted compressor characteristic curve can be addressed using the lower critical threshold speed, the upper critical threshold speed and the rated mass flow in order to determine the rated boost pressure. That is, in other words, the rated boost pressure is determined based on the critical threshold speed, the upper critical threshold speed and the rated mass flow when using the inverted compressor characteristic curve. Such an embodiment provides the advantage that the easily and accurately determined rated boost pressure can be set so that the critical resonant speed range is avoided as much as possible.

[0014] Such a method can be implemented in a control unit or device, for example, in the form of software or hardware or, for example, in a hybrid form consisting of software and hardware.

[0015] In addition, the scheme introduced here provides a device, which is configured to implement, control or realize the steps of a variant of the method introduced here in a corresponding mechanism. Through this embodiment variant of the present invention in the form of a device, the task that is the basis of the present invention can be quickly and effectively solved.

[0016] For this purpose, the device can have at least one computing unit for processing signals or data, at least one storage unit for storing signals or data, at least one interface to a sensor or actuator for reading in sensor signals from a sensor or outputting data or control signals to an actuator and / or at least one communication interface for reading in or outputting data, the communication interface being embedded in the communication protocol. The computing unit can be, for example, a signal processor, a microcontroller, etc., wherein the storage unit can be a flash memory or a magnetic storage unit. The communication interface can be designed for reading in or outputting data wirelessly and / or by wire, wherein a communication interface capable of reading in or outputting wired data can, for example, read these data in electrically or optically from a corresponding data transmission line or output them to a corresponding data transmission line.

[0017] In this case, a "device" can be understood as an electrical device which processes sensor signals and outputs control and / or data signals as a function of this. The device can have an interface which can be designed in hardware and / or software. In the case of a hardware design, the interface can, for example, be part of a so-called system ASIC which contains the various functions of the device. However, it is also possible that the interface is a separate integrated circuit or is at least partially composed of discrete structural elements. In the case of a software design, the interface can be a software module which, for example, is also located on a microcontroller in addition to other software modules.

[0018] Also advantageous is a computer program product or a computer program having a program code, which can be stored on a machine-readable carrier or storage medium, such as a semiconductor memory, a hard disk memory or an optical memory, and is used, in particular, to implement, realize and / or control the steps of the method according to one of the above-described embodiments when the program product or the program is executed on a computer or a device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] An exemplary embodiment of the solution presented here is shown in the drawings and is explained in detail in the following description.

[0020] Figure 1 A schematic diagram of an embodiment of a device for operating a turbocharger, in particular a rolling bearing, for an internal combustion engine of a motor vehicle is shown;

[0021] Figure 2 A flow chart showing an exemplary embodiment of a method for operating a turbocharger, in particular a rolling bearing, for an internal combustion engine;

[0022] Figure 3 A schematic diagram of an inverted compressor characteristic curve for operating a turbocharger, in particular a rolling bearing, for an internal combustion engine is shown; and

[0023] Figure 4 A schematic charge pressure-time diagram is shown for operating a turbocharger, in particular a rolling element-mounted turbocharger, for an internal combustion engine. DETAILED DESCRIPTION

[0024] Before describing the advantageous embodiments of the present invention below, the background and basis of the embodiments will first be briefly discussed.

[0025] The working point of an internal combustion engine or an internal combustion engine is determined by the available density, that is, the pressure and temperature level of the fresh air in the intake space before the inlet valve of the engine. For a turbine engine or an engine with a turbocharger, the increase in the specific engine torque is achieved by the increase in the air density relative to the ambient air. Therefore, in order to adjust the torque output of the internal combustion engine, the boost pressure regulation on the fresh air side is used. The closed-loop control loop is based on the rated boost pressure derived from the rated torque and the measured actual boost pressure before the throttle valve in general. The boost pressure to be adjusted is generated by the working point or rated torque of the internal combustion engine. The rated pressure ratio and the rated mass flow at the compressor stage define the working point or speed of the compressor in the compressor characteristic curve. In the specified area of ​​the compressor, the increase in boost pressure is assumed as the speed increases.

[0026] The natural frequency or resonance frequency of the turbine or compressor unit of the turbocharger depends on the mechanical design. Correspondingly safe operation in a wider speed range can be achieved according to tradition by sufficient damping characteristics in the body group or bearings of the turbocharger. Therefore, in traditional, lubricated support systems, basically every arbitrary speed range is operated permanently. For turbochargers that are particularly rolling-supported, such damping characteristics are sometimes reduced so that a specific speed should not be operated permanently. However, it is possible to pass through the critical speed. The natural frequency speed of a turbocharger or a turbocharger unit is generally known to the manufacturer. The critical range of the natural frequency can be changed by external influences, for example, these natural frequencies can depend on the oil temperature. Depending on the mechanical design, multiple resonance ranges may appear within the prescribed operating range of the exhaust gas turbocharger.

[0027] In the following description of advantageous exemplary embodiments of the invention, identical or similar reference numerals are used for elements which are shown in different figures and act similarly, wherein a repeated description of these elements is omitted.

[0028] Figure 1 The schematic diagram of an exemplary embodiment of a device 120 for operating a turbocharger 110, in particular a rolling bearing, for an internal combustion engine 102 for a vehicle 10 is shown. The vehicle 100 is a motor vehicle, such as a passenger car or the like. The device 120 is designed for operating a turbocharger 110. The device 120 can be designed, for example, as an independent unit or as part of a control device for an internal combustion engine 102 and / or a turbocharger 110 of the vehicle 100.

[0029] The device 120 includes a regulating device 124. The regulating device 124 is designed to set a set boost pressure 125 of the turbocharger 110 as a function of a compressor speed required for the turbocharger 110 according to the set torque 105 of the internal combustion engine 102 relative to at least one critical resonant speed range. The resonant speed range includes a resonant speed of the turbocharger 110, wherein vibration excitation of the turbocharger 110 occurs at its resonant frequency. The resonant speed range is limited by a lower critical threshold speed and an upper critical threshold speed.

[0030] Specifically, the regulating device 124 is configured to regulate the setpoint charge pressure 125 to a value that, when the required compressor speed increases to a lower critical threshold speed, causes the turbocharger 110 to operate at an upper critical threshold speed. In addition, the regulating device 144 is configured to regulate the setpoint charge pressure 125 to a value that, when the required compressor speed decreases to an upper critical threshold speed and until the required compressor speed reaches a lower critical threshold speed, causes the turbocharger 110 to operate at an upper critical threshold speed; and to a value that, when the required compressor speed decreases to a lower critical threshold speed, causes the turbocharger 110 to operate at a lower critical threshold speed.

[0031] According to one exemplary embodiment, the device 120 also includes a read-in device 122. The read-in device 122 is designed to read in a setpoint torque 105 of the internal combustion engine 102 and / or an actual value 115 of at least one manipulated variable for the turbocharger 110. In this case, the read-in device 122 is designed to read in the setpoint torque 105 and / or the actual value 115 from the internal combustion engine 102 and / or the turbocharger 110, more precisely from at least one detection device, control device, etc. assigned to the internal combustion engine 102 and / or the turbine 110, via an input interface 121. The read-in device 122 is also designed to forward the setpoint torque 105 and / or the actual value 115 to a control device 124.

[0032] According to an exemplary embodiment, the device 120 further comprises a generating device 126. The generating device 126 is configured to generate a control signal 127 for actuating a compressor of the turbocharger 110 using a set boost pressure 125 set by means of the regulating device 124. The generating device 126 is configured to receive the set boost pressure 124 from the regulating device 124. In addition, the generating device 126 or the device 120 is configured to output the control signal 127 to the turbocharger 110 via an output interface 129. When using the control signal 127, the turbocharger 110 can be advantageously operated, wherein the critical resonant speed range can be largely avoided.

[0033] Figure 2 A flow chart of an exemplary embodiment of a method 220 for operating a turbocharger, in particular a rolling bearing, for an internal combustion engine is shown. The method 220 for operating can be performed using Figure 1 Here, the method 220 for operating can be performed to operate Figure 1 turbocharger in or similar turbocharger.

[0034] The method 220 for operation comprises a step 224 of setting a rated boost pressure of the turbocharger as a function of a compressor speed for the turbocharger required according to the rated torque of the internal combustion engine relative to at least one critical resonant speed range. The resonant speed range comprises a resonant speed of the turbocharger, wherein vibration excitation of the turbocharger occurs at its resonant frequency. The resonant speed range is limited by a lower critical threshold speed and an upper critical threshold speed.

[0035] According to one embodiment, in the setting step 224, the set boost pressure is adjusted to a value that causes the turbocharger to operate at an upper critical threshold speed when the required compressor speed increases to a lower critical threshold range. In the setting step 224, the set boost pressure is adjusted to a value that causes the turbocharger to operate at an upper critical threshold speed when the required compressor speed decreases to an upper critical threshold and until the required compressor speed reaches a lower critical threshold; and to a value that causes the turbocharger to operate at a lower critical threshold speed when the required compressor speed decreases to a lower critical threshold speed.

[0036] According to one embodiment, a compressor characteristic curve that establishes a correlation between a rated pressure ratio, a rated mass flow and a compressor speed of the turbocharger is used in setting step 224 to determine the rated boost pressure. In this case, the rated mass flow and the rated pressure ratio are determined based on the rated torque of the internal combustion engine or are derived from the rated torque of the internal combustion engine. Optionally, the compressor characteristic curve is additionally inverted here in order to describe the rated pressure ratio with the compressor speed and the rated mass flow. The inverted compressor characteristic curve is addressed with a lower critical threshold speed, an upper critical threshold speed and a rated mass flow in order to determine the rated boost pressure.

[0037] According to one embodiment, the method 220 for operation also includes the step of reading in a setpoint torque of the internal combustion engine and / or an actual value of at least one manipulated variable for the turbocharger. Additionally or alternatively, the method 200 for operation also includes a step 226 of generating a control signal for actuating a compressor of the turbocharger using the setpoint boost pressure set in the setting step 224.

[0038] Figure 3 A schematic diagram of an inverted compressor characteristic curve 300 for operating a turbocharger, in particular a rolling bearing, for an internal combustion engine is shown. The inverted compressor characteristic curve 300 can be obtained by Figure 1 Devices in or similar devices and / or Figure 2 The method in or a similar method for operating such a turbocharger, in particular for setting a setpoint boost pressure, is used. The inverted compressor characteristic curve 300 is shown as a Cartesian coordinate system, wherein the throughput or mass flow 302 is plotted on the abscissa axis and the pressure ratio 304 is plotted on the ordinate axis. A plurality of speed lines for a pump limit 306 and a compressor speed 308 are plotted in the compressor characteristic curve 300. In addition, a resonance range or a critical resonance speed range 310 is plotted in the inverted compressor characteristic curve 300, which is limited by a lower critical threshold speed 312 and an upper critical threshold speed 314.

[0039] In order to set the desired torque of the internal combustion engine or internal combustion motor, the set mass flow and the set pressure at the inlet valve are derived from the set torque. From the compressor characteristic curve, the relationship between the pressure ratio 304 and the mass flow 302 and the compressor speed 308 can be described. By inverting the compressor characteristic curve, that is, in the inverted compressor characteristic curve 300, the pressure ratio 304 can be described with the compressor speed 308 and the mass flow 302. The inverted compressor characteristic curve 300 can be addressed with critical speeds, that is, a lower critical threshold speed 312 and an upper critical threshold speed 314 and the current set mass flow of the internal combustion engine or internal combustion motor.

[0040] Figure 4 A schematic boost pressure-time diagram 400 is shown for operating a turbocharger, in particular a rolling bearing, for an internal combustion engine. The boost pressure-time diagram 400 is similar to Figure 1 Devices in or similar devices and / or Figure 2 , or a similar method for operating such a turbocharger, in particular for setting a desired boost pressure. The boost pressure-time diagram 400 is shown as a Cartesian coordinate system, with the time t being plotted on the abscissa and the boost pressure P being plotted on the ordinate. The boost pressure-time diagram 400 shows a desired boost pressure 125 for an operating point of the internal combustion engine and a critical resonant speed range 310 with a lower critical threshold speed 312 and an upper critical threshold speed 314. In addition, the boost pressure-time diagram 400 shows a method for operating such a turbocharger, in particular for setting a desired boost pressure. Figure 1 The regulating mechanism of the device or similar device in Figure 2 The adjustment range 424 of the set boost pressure 125 is corrected by executing the setting steps within the scope of the method or a similar method.

[0041] Within control range 424, a stepped and / or abrupt control of setpoint charge pressure 125 occurs. This is caused by setting setpoint charge pressure 125 by means of a control device or by the execution of a setting step to a value which, when the required compressor speed increases to lower critical threshold speed 312, results in operation of the turbocharger with upper critical threshold speed 314. Figure 4This is the case in the left adjustment range 424 in FIG. In addition, the set charge pressure 125 is adjusted by means of the adjustment device or by the execution of the setting step to a value that causes the turbocharger to operate with the upper critical threshold speed 314 when the required compressor speed drops to the upper critical threshold speed 314 and until the required compressor speed reaches the lower critical threshold speed 312, and to a value that causes the turbocharger to operate with the lower critical threshold speed 312 when the required compressor speed drops to the lower critical threshold speed 312.

[0042] If the boost pressure to be set by the setpoint torque or setpoint boost pressure 125 reaches a critical range or critical resonant speed range 310 , in other words, the procedure explained below occurs in particular.

[0043] Setpoint boost pressure 125 for the operating point of the internal combustion engine increases and approaches lower critical speed threshold or lower threshold speed 312 from below: When lower critical speed threshold or threshold speed 312 is reached, setpoint boost pressure 125 is increased in such a way that a compressor operating point at critical upper speed threshold or threshold speed 314 is required. Critical speed range or resonance speed range 310 is then passed upward as quickly as possible.

[0044] The set boost pressure 125 for the operating point of the internal combustion engine decreases and approaches the upper critical speed threshold or threshold speed 314 from above: in the case of conversion, the set boost pressure 125 is kept at the upper critical speed threshold or threshold speed 314 until the unrestricted set boost pressure 125 drops below the calculated lower speed threshold 312. The turbocharger thus remains at the upper critical speed or speed threshold 314 until an operating point of the combination of internal combustion engine and turbocharger that falls below the critical speed range or resonance speed range 310 is reached.

[0045] If an exemplary embodiment includes an “and / or” connection between a first feature and a second feature, this may be interpreted as follows: the exemplary embodiment according to one embodiment has both the first feature and the second feature and according to another embodiment has either only the first feature or only the second feature.

Claims

1. A method (220) for operating a turbocharger (110), in particular a rolling bearing, for an internal combustion engine (102), wherein the method (220) comprises the following steps: A rated boost pressure (125) of the turbocharger (110) is set (224) as a function of a compressor speed (308) for the turbocharger (110) required according to a rated torque (105) of the internal combustion engine (102) relative to at least one critical resonant speed range (310), the resonant speed range comprising a resonant speed of the turbocharger (110), wherein vibration excitation of the turbocharger (110) occurs at its resonant frequency, wherein the resonant speed range (310) is limited by a lower critical threshold speed (312) and an upper critical threshold speed (314).

2. The method (220) according to claim 1, wherein in a setting step (224) the set boost pressure (125) is adjusted to a value which causes the turbocharger (110) to operate at an upper critical threshold speed (314) when the required compressor speed (308) rises to a lower critical threshold speed (312).

3. A method (220) according to any one of the preceding claims, wherein in a setting step (224), the rated boost pressure (125) is adjusted to a value that causes the turbocharger (110) to operate with an upper critical threshold speed (314) when the required compressor speed (308) drops to the upper critical threshold speed (314) and until the required compressor speed (308) reaches a lower critical threshold speed (312); and the rated boost pressure (125) is adjusted to a value that causes the turbocharger (110) to operate with a lower critical threshold speed (312) when the required compressor speed (308) drops to the lower critical threshold speed (312).

4. The method (220) according to any one of the preceding claims, comprising: - the rated torque (105) of the internal combustion engine (102) and / or - a step (222) of determining at least one actual value (115) of a controlled variable of the turbocharger (110), in order to also set a setpoint boost pressure (125) of the turbocharger (110) taking into account the read-in actual value (115) of the at least one controlled variable.

5. The method (220) according to any one of the preceding claims comprises a step (226) for generating a control signal (127) for controlling the compressor of the turbocharger (110) using the set boost pressure (125) set in the setting step (224).

6. A method (220) according to any one of the preceding claims, wherein a compressor characteristic curve that establishes a correlation between a rated pressure ratio (304), a rated mass flow (302) and a compressor speed (308) of the turbocharger (110) is used in a setting step (224) in order to determine the rated boost pressure (125), wherein the rated mass flow (302) and the rated pressure ratio (304) are based on a rated torque (105) of the internal combustion engine (102).

7. The method (220) according to claim 6, inverting the compressor characteristic curve so that the rated pressure ratio (304) is described by the compressor speed (308) and the rated mass flow (302), wherein the inverted compressor characteristic curve (300) is addressed by a lower critical threshold speed (312), an upper critical threshold speed (314) and the rated mass flow (302) in order to determine the rated boost pressure (125).

8. A device (120) configured to execute and / or control the steps (222, 224, 226) of the method (220) according to any one of the preceding claims in a corresponding unit (122, 124, 126).

9. A computer program configured to carry out and / or control the steps (222, 224, 226) of the method (220) according to claim 1.

10. A machine-readable storage medium having stored thereon the computer program according to claim 9.

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