JP2008223527A - Turbo supercharger control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the rotational speed of a turbo supercharger at high accuracy without performing calculation of actual turbine power. <P>SOLUTION: A target excess pressure is determined based on accelerator opening, and a compressor pressure ratio PR is determined from the target excess pressure. When the rotational speed Nt of an internal combustion engine is lower than the predetermined rotational speed Ntp, since an equivalent line of the target rotational speed N<SB>t-trg</SB>of the supercharger is approximately constant relative to the compressor pressure ratio PR regardless of a value of a correction compressor passing air flow rate G<SB>a-mod</SB>, the target rotational speed N<SB>t-trg</SB>of the supercharger is only determined from the compressor pressure ratio PR. When the rotational speed Nt of the internal combustion engine is higher than the predetermined rotational speed Ntp, the target rotational speed N<SB>t-trg</SB>of the supercharger is determined from any two values of the compressor pressure ratio PR, the correction compressor passing air flow rate G<SB>a-mod</SB>and the rotational speed Nt of the internal combustion engine. Driving of an electric motor provided on the turbo supercharger is controlled based on the determined target revolution number N<SB>t-trg</SB>of the supercharger. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a turbocharger control system that controls the rotational speed of a turbocharger.

For example, a turbocharger with an electric motor is known that controls the rotational speed of the supercharger by controlling the drive of the electric motor (see Patent Document 1). In the turbocharger control mechanism described in Patent Document 1, the target turbine power is calculated based on the target supercharging pressure and the target air amount, and the actual turbine power is calculated based on the exhaust information. Based on the difference between the actual turbine power and the actual turbine power, the assist power of the electric motor is calculated.
JP 2006-242064 A

  The actual turbine power is calculated using measured values of the exhaust flow rate and the exhaust gas temperature, but it is difficult to obtain a measured value with sufficient accuracy for these. In particular, since it is difficult to obtain highly accurate measurement values in real time, it is difficult to calculate actual turbine power in a transient state. Further, when a variable nozzle or a waste gate is used, it is more difficult to reflect these effects.

  An object of the present invention is to control the rotational speed of a turbocharger with high accuracy without calculating actual turbine power.

  A turbocharger control system according to the present invention is a turbocharger control system used for supercharging an internal combustion engine, and calculates a target supercharging pressure of a supercharger based on an accelerator opening. Pressure calculating means, target turbocharger speed calculating means for calculating the target speed of the turbocharger based on the target boost pressure, and supercharger speed detecting means for detecting the actual speed of the turbocharger; And a supercharger rotation speed control means for controlling the rotation speed of the supercharger based on the target rotation speed and the actual rotation speed.

  The supercharger preferably includes an electric motor that assists the turbine power, and the supercharger rotation speed control means controls the rotation speed of the supercharger by controlling the drive of the electric motor. The target supercharger rotational speed calculation means calculates the target rotational speed based only on the target supercharging pressure when the internal combustion engine rotational speed is relatively low, and the internal combustion engine rotational speed when the internal combustion engine rotational speed is relatively high. The target rotational speed is calculated based on any two values of the target supercharging pressure and the air flow rate flowing into the compressor.

  The turbocharger control system further includes exhaust gas control means for controlling the exhaust system from the internal combustion engine based on the target supercharging pressure. The exhaust gas control means includes, for example, at least one of a turbine flow rate control means for controlling the turbine flow rate or an exhaust gas circulation amount control means for controlling the circulation amount of the exhaust gas to the intake system.

  As described above, according to the present invention, the rotational speed of the turbocharger can be controlled with high accuracy without calculating the actual turbine power.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a turbocharger control system according to the first embodiment of the present invention.

  The internal combustion engine 10 includes an intake manifold 10A and an exhaust manifold 10B. Air that has been pressurized by the compressor 11 </ b> A of the turbocharger 11 is supercharged to the intake manifold 10 </ b> A via the intercooler 12 and the throttle 13.

  The compressor 11A uses a turbine 11B that is rotationally driven by exhaust gas from the exhaust manifold 10B as a power source. In the turbocharger 11 of the present embodiment, an electric motor 11C for assisting the power of the turbine 11B is provided. Electric power is supplied to the electric motor 11C from a control system 14 including an electronic control unit, an inverter / controller, and the like, and its drive is controlled. Further, a sensor 15 for detecting the turbocharger rotational speed is provided on the rotating shaft of the turbocharger 11, and a pressure sensor 16 for measuring the supercharging pressure is provided on the intake manifold 10A. Furthermore, a flow rate sensor 17 and a temperature sensor 18 are provided in the vicinity of the inlet of the compressor 11A, and a sensor 19 for detecting the rotational speed of the internal combustion engine is provided on the crankshaft of the internal combustion engine 10. Signals detected by the sensors 15 to 19 are respectively input to the control system 14.

  A control process of the turbocharger 11 in the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart of the control process of the turbocharger 11 (particularly, the drive control process of the electric motor 11C) in the present embodiment.

  In step S101, a target boost pressure P_trg by the compressor 11A is calculated. The target supercharging pressure P_trg is obtained from the internal combustion engine speed Ne and the accelerator opening Af using, for example, the map of FIG. 3 to first determine the fuel injection amount Q, and further to the internal combustion engine speed Ne and the determined fuel injection amount Q. Based on the map shown in FIG. 4, for example.

  In FIG. 3, the horizontal axis corresponds to the internal combustion engine speed Ne, the vertical axis corresponds to the accelerator opening Af, and the plurality of straight lines drawn in the graph correspond to the isolines of the fuel injection amount Q, respectively. Note that the value of each isoline in FIG. 3 increases as the distance from the graph origin increases. In FIG. 4, the horizontal axis corresponds to the internal combustion engine speed Ne, the vertical axis corresponds to the fuel injection amount Q, and the curves drawn in the graph correspond to the isolines of the target boost pressure P_trg. Note that the values of the isolines in FIG. 4 increase as the fuel injection amount increases.

  Next, in step S102, the atmospheric pressure P0 is measured. In step S103, the current air flow rate Ga flowing into the compressor 11A detected by the flow rate sensor 17 and the temperature sensor 18 and the intake air temperature T1 are measured. 14 is input. In step S104, the inlet pressure P1 of the compressor 11A is obtained as P1 = (atmospheric pressure P0) − (pressure loss F (Ga)) from the pressure loss F (Ga) given as a function of the atmospheric pressure P0 and the air flow rate Ga. It is done.

  In step S105, the compressor outlet pressure P2 is calculated as P2 = (target supercharging pressure (P_trg) + (pressure) from the target supercharging pressure P_trg obtained in step S101 and the pressure loss f (Ga) given in advance as a function of the air flow rate Ga. Loss f (Ga)) Further, in step S106, the compressor pressure ratio PR = P2 / P1 is obtained.

  In step S107, it is determined whether or not the internal combustion engine speed Ne is equal to or less than a predetermined value. FIG. 5 shows an isoline of the internal combustion engine speed Nt and the target turbocharger speed when the corrected compressor passing air flow rate Ga_mod obtained by correcting the compressor passing air amount Ga is set on the horizontal axis and the compressor pressure ratio PR is set on the vertical axis. An isoline of Nt_trg is schematically shown. As shown in FIG. 5, each value of the isoline of the internal combustion engine speed Nt increases as the corrected compressor passage air flow rate Ga_mod increases, and each value of the isoline of the target turbocharger speed Nt_trg Increases as you move away from the graph origin. The corrected compressor passage air flow rate Ga_mod is a value obtained by correcting the compressor passage air amount Ga by the intake air temperature T1 and the compressor inlet pressure P1, θ = intake air temperature T1 / reference temperature (for example, 293.15K), δ = compressor inlet. When the pressure is P1 / reference pressure (eg, 101.325 kPa), Ga_mod = air flow rate Ga × √ (θ / δ).

  As shown in FIG. 5 (Map 1), the compressor pressure ratio is increased even when the corrected compressor passage air flow rate Ga_mod increases in the region below the predetermined internal combustion engine speed Ntp on the isoline of the target turbocharger speed Nt_trg. PR is substantially constant. On the other hand, in the region exceeding the predetermined internal combustion engine speed Ntp, the compressor pressure ratio PR rapidly decreases as the corrected compressor passage air flow rate Ga_mod increases on the isoline of the target turbocharger speed Nt_trg. That is, the target turbocharger speed Nt_trg has a one-to-one relationship with the compressor pressure ratio PR in the region below the predetermined internal combustion engine speed Ntp, and is determined only by the compressor pressure ratio PR. On the other hand, in a region where the internal combustion engine speed Nt is larger than the predetermined internal combustion engine speed Ntp, the target supercharger speed Nt_trg is within the corrected compressor passage air flow rate Ga_mod, the compressor pressure ratio PR, and the internal combustion engine speed Nt. It is determined by any two values.

  Therefore, in the present embodiment, when the internal combustion engine speed Nt is equal to or lower than the predetermined internal combustion engine speed Ntp, the target turbocharger speed Nt_trg is referred to Map2 shown in FIG. When it is determined only by PR and the internal combustion engine speed Nt is larger than the predetermined internal combustion engine speed Ntp, in step S109, the target turbocharger speed Nt_trg is referred to Map1 shown in FIG. It is determined based on any two values of the air flow rate Ga_mod, the compressor pressure ratio PR, and the internal combustion engine speed Nt. The predetermined internal combustion engine speed Ntp is, for example, 3000 rpm. In FIG. 5, a curve S is a surge line.

  In step S110, the target turbocharger speed Nt_trg0 corrected by the intake air temperature T1 based on the target turbocharger speed Nt_trg obtained in step S108 or step S109 is calculated as Nt_trg0 = Nt_trg / √θ. In step S111, the actual turbocharger speed Nt, which is the actual turbocharger speed, is detected by the sensor 15 and input to the control system 14.

  In step S112, it is determined whether or not the actual turbocharger rotation speed Nt is smaller than the corrected target turbocharger rotation speed Nt_trg0. If it is determined in step S112 that the actual turbocharger rotational speed Nt is smaller than the corrected target turbocharger rotational speed Nt_trg0, the rotational speed Nt of the supercharger 11 has not reached the target value. In step S113, the motor 11C is operated with reference to Map3 shown in FIG.

  In FIG. 7, the horizontal axis corresponds to the difference between the corrected target turbocharger speed Nt_trg0 and the actual supercharger speed Nt (Nt_trg0−Nt), and the vertical axis corresponds to the output of the electric motor 11C. That is, when the difference (Nt_trg0−Nt) between the target turbocharger rotational speed Nt_trg0 and the actual supercharger rotational speed Nt exceeds a certain value, the motor output increases monotonously, When the difference (Nt_trg0−Nt) in the rotational speed Nt becomes equal to or greater than a predetermined value, the output of the electric motor 11C becomes 100%.

  On the other hand, if it is determined in step S112 that the value of the target turbocharger rotation speed Nt_trg0 is equal to or greater than the actual turbocharger rotation speed Nt, the control system 14 stops (or stopped) the operation of the electric motor 11C in step S114. To maintain the state).

  When one of the processes in steps S113 and S114 is executed, the control process for the turbocharger 11 is finished, and the same process is repeated thereafter at a predetermined time interval.

  As described above, according to the first embodiment, the target turbocharger rotational speed is obtained from the target supercharging pressure or the like without calculating the actual turbine power, and the supercharger rotational speed is monitored based on the target turbocharger rotational speed. Thus, the rotational speed of the supercharger can be controlled. In particular, in the present embodiment, the turbocharger is driven and controlled more flexibly at a rotational speed corresponding to the accelerator opening even in a transient state such as when the accelerator is depressed by driving an electric motor as assist power. Can do.

  In the present embodiment, in the turbocharger that performs electric assist, the rotational speed of the supercharger is controlled by performing drive control of the electric motor, but the turbocharger control system of the present embodiment is, for example, The present invention is also applicable to a case where the rotational speed is controlled only by control of a variable nozzle (VN) mechanism or a waste gate (WG) mechanism without having an electric assist function.

  Next, a second embodiment of the present invention will be described with reference to FIG. In the turbocharger control system of the second embodiment, the electric motor 11C provided in the turbocharger 11 is controlled based on the calculated target supercharging pressure P_trg, and a predetermined exhaust system process is performed. Done. The exhaust system processing using the target boost pressure P_trg includes, for example, turbine flow rate control using a variable nozzle (VN) mechanism or a waste gate (WG) mechanism.

  In the second embodiment, for example, a variable nozzle (not shown) is provided on the upstream side of the turbine 11B of the turbine supercharger 11 of FIG. That is, by adjusting the opening of the nozzle, the flow rate of the exhaust gas supplied to the turbine 11B is controlled, and the turbine power is adjusted. In addition, since the structure of another turbocharger control system is the same as that of 1st Embodiment, the description is abbreviate | omitted using the same referential mark about the same structure.

  FIG. 8 is a flowchart of the turbocharger control process of the second embodiment including the control of the variable nozzle (VN) mechanism. Hereinafter, the turbocharger control process of the second embodiment will be described with reference to FIG. .

  In step S201, the target boost pressure P_trg is calculated from the internal combustion engine speed Ne and the accelerator opening Af in the control system 14 in the same manner as in step S101 of FIG. In step S202, the current supercharging pressure P3 in the intake manifold 10A is measured by the pressure sensor 16 provided in the intake manifold 10A and input to the control system 14.

  In step S203, it is determined whether or not to perform transient control of the variable nozzle. That is, the value of (target supercharging pressure P_trg) − (supercharging pressure P3) is not less than a predetermined threshold value α1 (α1> 0) (corresponding to sudden acceleration) or not more than a predetermined threshold value β1 (β1 <0). It is determined whether or not (corresponding to sudden deceleration). When it is determined that the value of (target supercharging pressure P_trg) − (supercharging pressure P3) is not equal to or greater than a predetermined threshold value α1 or not equal to or less than the threshold value β1, that is, the target supercharging pressure P_trg and the current supercharging pressure P3 If the variable nozzle (VN) only needs to be maintained at a normal opening, and the variable nozzle (VN) is maintained at a normal opening in step S208, the turbocharger of the second embodiment The control process ends. Here, the normal opening of the variable nozzle (VN) is an opening obtained by adding the basic drive amount of the variable nozzle (VN) based on the target boost pressure and the correction amount by feedback, and the basic drive amount. As for, the base opening degree corresponding to the exhaust passage area assumed to be necessary for setting the actual boost pressure P3 to the target boost pressure P_trg is used. That is, the base opening is determined based on the internal combustion engine speed Ne and the engine load, and the feedback amount is determined based on the value of (target boost pressure P_trg) − (supercharge pressure P3).

  On the other hand, when it is determined in step S203 that the value of (target supercharging pressure P_trg) − (supercharging pressure P3) is not less than a predetermined threshold value α1 or not more than the threshold value β1, that is, the target supercharging pressure P_trg and the current value. When the difference from the supercharging pressure P3 is large, the opening degree of the variable nozzle (VN) needs to be controlled transiently different from the normal opening degree. (VN) is controlled by the control system 14.

  That is, when it is determined in step S203 that the value of (target boost pressure P_trg) − (supercharge pressure P3) is equal to or greater than the predetermined threshold value α1, the opening of the variable nozzle (VN) is set to the normal opening degree in step S204. Increase the boost pressure more quickly by setting it narrower. On the other hand, when it is determined in step S203 that the value of (target supercharging pressure P_trg) − (supercharging pressure P3) is equal to or less than the predetermined threshold value β1, the opening of the variable nozzle (VN) is made to be larger than the normal opening. Widely set (for example, fully open) to reduce the supercharging pressure more quickly.

  In step S203, by setting a plurality of threshold values, the value of (target supercharging pressure P_trg) − (supercharging pressure P3) is divided in stages, and (target supercharging pressure P_trg) − (superimposed pressure). Depending on which section the value of the supply pressure P3) belongs to, the opening of the variable nozzle (VN) in step S204 may be set to a different value.

  Next, in step S205, for example, the value of (target supercharging pressure P_trg) − (supercharging pressure P3) is not less than a predetermined threshold value α2 (corresponding to sudden acceleration) or not more than a predetermined threshold value β2 (corresponding to sudden deceleration). Whether or not the electric motor 11C provided in the turbocharger 11 is to be operated is determined. The predetermined threshold values α2 and β2 may be the same as or different from the threshold values α1 and β1 in step S203.

  If the value of (target supercharging pressure P_trg) − (supercharging pressure P3) is smaller than the predetermined threshold α2 and larger than the predetermined threshold β2 in step S205, the turbocharger 11 is determined in step S207. The operation of the electric motor 11C is stopped (or maintained in the stopped state), and the turbocharger control process of the second embodiment ends.

  On the other hand, if it is determined in step S205 that the value of (target boost pressure P_trg) − (supercharge pressure P3) is equal to or greater than a predetermined threshold value α2 or less than or equal to the threshold value β2, the motor 11C is controlled in step S206. The process for starting is started. That is, when it is determined in step S205 that the value of (target boost pressure P_trg) − (supercharge pressure P3) is equal to or greater than the predetermined threshold value α2, the process from step S102 to step S114 in FIG. 2 is performed in step S206. As in the first embodiment, the target turbocharger rotational speed N_trg0 is calculated from the target supercharging pressure P_trg, and the drive of the electric motor 11C is controlled based on the measured actual supercharger rotational speed Nt. Is done. If it is determined in step S205 that the value of (target supercharging pressure P_trg) − (supercharging pressure P3) is equal to or smaller than the predetermined threshold value β2, the actual supercharger rotation speed Nt is set to the target supercharging in step S206. The electric motor 11C is controlled so as to suppress the turbine rotational speed so as to be the feeder rotational speed N_trg0. The rotation suppression control includes a case where regeneration is performed by the electric motor 11.

  Thus, the turbocharger control process of the second embodiment is completed. In addition, when the turbocharger control process of the second embodiment is completed by completing any of the processes of step S206, step S207, and step S208, the processes after step S201 are repeatedly executed at predetermined time intervals. The

  As described above, also in the second embodiment, the same effect as in the first embodiment can be obtained. Further, as shown in the second embodiment, the target supercharging pressure is often used for controlling a mechanism provided in an exhaust system such as a variable valve. Therefore, supercharger rotation speed control using the target supercharging pressure is performed. Is highly consistent with the control of other mechanisms.

  In the second embodiment, the turbine flow rate control using the variable nozzle (VN) mechanism has been described as an example. However, even when the turbine flow rate control is performed using the waste gate (WG) mechanism, (P_trg−P3) The same control can be performed based on the comparison between the value and the threshold value. In this case, the opening / closing operation of the variable nozzle in steps S203, S204, and S208 in FIG. 8 is replaced with the opening / closing operation of the waste gate valve.

  In the present embodiment, the target turbocharger rotation speed is obtained from the map (Map1, Map2) using the compressor pressure ratio, but when the compressor inlet pressure is considered to correspond to a substantially constant atmospheric pressure. The target turbocharger speed can also be obtained using the compressor outlet pressure instead of the compressor pressure ratio. In this case, the vertical axis of Map1 and the horizontal axis of Map2 correspond to the compressor outlet pressure.

It is a block diagram which shows the structure of the turbocharger control system in 1st Embodiment of this invention. It is a flowchart of the control processing in the turbocharger control system of 1st Embodiment. 3 is a map for obtaining a fuel injection amount from an internal combustion engine speed and an accelerator opening. 3 is a map for obtaining a target supercharging pressure from an internal combustion engine speed and a fuel injection amount. FIG. 6 is a map for obtaining a target supercharger speed using two values of a corrected compressor passage air flow rate, a compressor pressure ratio, and an internal combustion engine speed when the engine speed is relatively high. It is a map for calculating | requiring a target supercharger rotation speed using a compressor pressure ratio when an internal combustion engine rotation speed is relatively low. It is a map for calculating | requiring the output of an electric motor from correction | amendment compressor passage air flow rate. It is a flowchart of the control processing in the turbocharger control system of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 10A Intake manifold 10B Exhaust manifold 11 Turbocharger 11A Compressor 11B Turbine 11C Electric motor 14 Control system 15 Supercharger rotation speed sensor 16 Pressure sensor 17 Flow rate sensor 18 Temperature sensor 19 Internal combustion engine rotation speed sensor

Claims (5)

A turbocharger control system used for supercharging an internal combustion engine,
A target boost pressure calculating means for calculating a target boost pressure of the turbocharger based on the accelerator opening;
Target turbocharger speed calculating means for calculating a target speed of the supercharger based on the target boost pressure;
Supercharger rotation speed detection means for detecting the actual rotation speed of the supercharger;
A turbocharger control system comprising: a supercharger rotation speed control unit that controls the rotation speed of the supercharger based on the target rotation speed and the actual rotation speed.   The supercharger includes an electric motor for assisting turbine power, and the supercharger rotation speed control means controls the rotation speed of the supercharger by controlling driving of the electric motor. The turbocharger control system according to 1.   The target supercharger rotational speed calculation means calculates the target rotational speed based only on the target supercharging pressure when the internal combustion engine rotational speed is relatively low, and when the internal combustion engine rotational speed is relatively high, 2. The turbocharger according to claim 1, wherein the target rotational speed is calculated based on any two values of the internal combustion engine rotational speed, the target supercharging pressure, and an air flow rate flowing into the compressor. Machine control system.   The turbocharger control system according to any one of claims 1 to 3, further comprising exhaust gas control means for controlling an exhaust system from the internal combustion engine based on the target supercharging pressure.   The exhaust gas control means includes at least one of a turbine flow rate control means for controlling the turbine flow rate or an exhaust gas circulation amount control means for controlling the circulation amount of the exhaust gas to the intake system. The turbocharger control system according to claim 4.

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