JP4779738B2 - Control device and control method for internal combustion engine provided with turbocharger - Google Patents

Description

  The present invention relates to control of an internal combustion engine provided with a turbocharger.

Patent Document 1 discloses an internal combustion engine having a plurality of superchargers, which detects an actual suction negative pressure downstream of the throttle and uses the actual suction negative pressure as a single parameter to target a pressure upstream of the throttle, that is, a boost pressure. A technique is described in which the operations of a plurality of superchargers are feedback controlled so as to maintain the values close to each other.
JP-A-1-267318

  In an internal combustion engine equipped with a turbocharger, the pressure downstream of the throttle differs depending on the turbocharger operating (supercharging) state, that is, the pressure upstream of the throttle due to supercharging, even at the same throttle opening. Therefore, the intake air amount, that is, the engine output torque varies. For this reason, for example, the amount of intake air temporarily increases due to the start of supercharging during slow acceleration, and the torque increases carelessly, compared to a naturally aspirated internal combustion engine without a turbocharger, There was a problem that drivability decreased.

  Further, as in Patent Document 1, in the configuration in which the feedback control is performed based on the actual intake negative pressure downstream of the throttle so that a predetermined supercharging pressure is obtained, the response delay of the feedback control and the convergence of the control are reduced. Concerned.

The present invention has been made in view of such problems, and relates to control of an internal combustion engine having a turbocharger that supercharges intake air using exhaust and a throttle that is provided in an intake passage. Throttle upstream pressure detection means for detecting the throttle upstream pressure, which is the pressure in the intake passage downstream of the turbocharger compressor and upstream of the throttle, the accelerator opening detection means for detecting the accelerator opening, and the throttle for driving and controlling the throttle And a throttle control unit that calculates a target throttle opening based on the accelerator opening, and that the throttle upstream pressure is set at a midpoint between the maximum boost pressure and the atmospheric pressure. The target throttle opening is corrected to the close side as the value increases with respect to the target, and the target throttle opening as the throttle upstream pressure becomes lower than the reference pressure. It is characterized in that the correction to the open side.

  According to the present invention, the intake of the turbocharging caused by the supercharging state is detected by detecting the throttle upstream pressure that fluctuates according to the supercharging state by the turbocharger and correcting the target throttle opening based on the throttle upstream pressure. It is possible to absorb and reduce variations and fluctuations in air volume at a high level. In addition, since the target throttle opening located immediately downstream is corrected according to the throttle upstream pressure, the calculation / control processing is simpler than the feedback control as in the conventional example, and the responsiveness is also improved. And it does not cause a decrease in convergence.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a system configuration of an internal combustion engine including a turbocharger according to an embodiment of the present invention. The internal combustion engine 10 includes an intake valve 12 that opens and closes an intake passage 11, an exhaust valve 14 that opens and closes an exhaust passage 13, a spark plug 15 that sparks and ignites an air-fuel mixture in a combustion chamber 15, and a combustion chamber 15 (or intake air). And a fuel injection valve 16 for injecting fuel into the passage 11). A throttle 17 is interposed in the intake passage 11. The throttle 17 is of an electronic control type that incorporates a motor and a position sensor that can adjust the opening TVO of the throttle 17 independently of the operation of an accelerator pedal (not shown) by the driver. As is well known, the turbocharger 20 is configured such that a turbine 21 interposed in the exhaust passage 13 and a compressor 22 interposed in the intake passage 11 upstream of the throttle 17 are coaxially connected to each other. The compressor 22 is rotationally driven by a turbine 21 driven by energy to supercharge intake air.

  As is well known, the engine control unit 25 is a digital computer that stores and executes various control processes, and outputs control signals to the spark plug 18, the fuel injection valve 16, the throttle 17, and the like based on the engine operating state. The ignition timing, fuel injection amount, fuel injection timing, throttle opening, and the like are controlled. As various sensors for detecting the engine operating state, an accelerator opening sensor 26 for detecting an operation amount of an accelerator pedal (not shown) depressed by a driver, that is, an accelerator opening APO, and an engine speed Ne are detected. A crank angle sensor 27, an air flow meter 28 for detecting the intake air amount, a water temperature sensor 29 for detecting the cooling water temperature, and the like are provided. Further, in the intake passage 11, a throttle upstream pressure detection sensor 31 that detects an intake pressure upstream of the throttle 17, that is, a throttle upstream pressure (supercharging pressure), at a position downstream of the turbine 22 and upstream of the throttle 17. Is provided.

  FIG. 2 is a flowchart schematically showing the control contents of the setting process of the target throttle opening tTVO of the throttle 17 according to the present embodiment. This routine is repeatedly executed by the engine control unit 25, for example, every predetermined period (for example, every 10 ms or every predetermined crank angle). The throttle 17 is driven and controlled toward the target throttle opening tTVO set here.

  In step S1, the accelerator opening APO, the engine speed Ne, the throttle upstream pressure Pc, and the like detected by the various sensors described above are read. In step S2, based on the accelerator opening APO, it is determined whether or not it is an operating region in which correction processing based on a throttle upstream pressure Pc and an engine speed Ne to be described later is to be performed. In this embodiment, it is determined whether the accelerator opening APO is less than a predetermined determination value α near the throttle fully open. In the region near the full opening where the accelerator opening APO is greater than or equal to the determination value α, the process proceeds to step S6, and the target throttle opening tTVO (fully opened or near full opening) is set mainly according to the accelerator opening APO.

  In a region where the accelerator opening APO is less than the determination value α, that is, in an operation region excluding the region near the full opening, the target throttle opening tTVO is set through steps S3 to S5. First, in step S3, a basic target throttle opening tTVO is calculated based on the accelerator opening APO. Specifically, the target throttle downstream pressure (collector boost pressure) corresponding to the intake air amount is calculated according to the accelerator opening APO, and the target throttle opening tTVO is set so as to obtain this target throttle downstream pressure.

  In the subsequent step S4, the target throttle opening tTVO is corrected based on the throttle upstream pressure Pc. Specifically, a first correction coefficient β (Pc) corresponding to the throttle upstream pressure Pc is obtained using a preset map, and tTVO is updated by multiplying tTVO by this correction coefficient β (Pc). . FIG. 3 is a characteristic diagram showing the relationship among the throttle opening TVO, the engine torque (load), and the throttle upstream pressure Pc. The amount of intake air supplied to the intake collector on the downstream side of the throttle 17 corresponding to the engine torque varies according to the pressure difference before and after the throttle 17. In the case of an internal combustion engine provided with the turbocharger 20, the throttle upstream pressure Pc varies depending on the operating state of the turbocharger 20, that is, the supercharged state. Therefore, as shown by the arrow Y1 in FIG. 3, even when the throttle opening degree TVO is the same, the engine torque changes due to the throttle upstream pressure Pc. For example, when the throttle upstream pressure Pc is high, the intake air amount increases compared to when it is low. As a result, the engine torque increases. Therefore, in the present embodiment, as indicated by the arrow Y2 in FIG. 3, the target throttle opening tTVO is corrected to the close side as the throttle upstream pressure Pc increases. Therefore, for example, even when the throttle upstream pressure Pc is high, an appropriate torque corresponding to the accelerator opening APO can be obtained without inadvertently increasing torque.

  Referring to FIG. 2 again, in the subsequent step S5, the target throttle opening tTVO is further corrected in accordance with the engine speed Ne. Specifically, a second correction coefficient γ (Ne) corresponding to the engine speed Ne is obtained using a preset map, and tTVO is updated by multiplying tTVO by this correction coefficient γ (Ne). .

  FIG. 4 shows the relationship between the throttle downstream pressure (collector boost pressure), the exhaust pressure, and the engine speed Ne. FIG. 5 shows the throttle opening TVO and the pressure ratio before and after the throttle (throttle downstream pressure / throttle upstream pressure). And the engine speed Ne. As shown in FIG. 4, even at the same throttle downstream pressure, the exhaust pressure differs depending on the engine speed, and the exhaust pressure increases as the engine speed increases (see arrow Y3). For this reason, as shown in FIG. 5, even when the throttle opening degree TVO is equivalent, the higher the engine speed Ne, the lower the pressure ratio before and after the throttle (see arrow Y4), that is, the ratio that is throttled by the throttle 17. Becomes larger. Therefore, in this embodiment, the target throttle opening degree tTVO is corrected to the close side as the engine speed Ne decreases, that is, the target throttle opening degree tTVO is corrected to the opening side as the engine speed Ne increases. As a result, the target throttle opening tTVO can be appropriately set according to the engine speed, and for example, a torque drop on the high rotation side can be reduced or eliminated.

  FIG. 6 shows a time chart at the time of start acceleration to an intermediate opening such as a 1/4 opening. In the figure, the characteristic when the control of the present embodiment is applied is indicated by a solid line, and the characteristic of a comparative example in which the correction processing shown in steps S4 and S5 of FIG. 2 is not performed is indicated by a broken line. As shown in the figure, according to the present embodiment, the torque change is smoother than that of the comparative example, and abrupt torque fluctuation accompanying the rise of supercharging is prevented, thereby improving drivability. be able to.

In the setting of the target throttle opening tTVO at step S3 of FIG. 2, tTVO is set with reference to when the throttle on the fluid pressure Pc is an intermediate reference pressure sPc the maximum boost pressure and atmospheric pressure. That is, when the throttle on the fluid pressure Pc is the reference value SPC, the correction coefficient of the steps S4 and S5 β (Pc), γ ( Ne) becomes 1, is set so as not to be substantially correct Yes. As a result, the correction range is reduced, the calculation is simplified, and torque fluctuations can be effectively absorbed and canceled with high responsiveness.

  FIG. 7 shows a time chart during the preceding vehicle following traveling. In the figure, the characteristic when the control of the present embodiment is applied is indicated by a solid line, and the characteristic of a comparative example in which the correction processing shown in steps S4 and S5 of FIG. 2 is not performed is indicated by a broken line. As shown in the figure, in the comparative example, because the engine torque fluctuates with respect to the accelerator opening APO, the accelerator pedal is frequently operated by the driver so that the desired engine torque is obtained, and the accelerator is opened. The APO is frequently changed. On the other hand, in this embodiment, since the target throttle opening tTVO is corrected according to the supercharging state, the throttle having excellent responsiveness so as to obtain an appropriate engine torque according to the accelerator opening APO. Since the opening degree is driven and controlled, the amount of accelerator operation during follow-up traveling can be significantly reduced as compared with the comparative example.

  As described above, according to the present embodiment, by correcting the target throttle opening tTVO according to the throttle upstream pressure Pc immediately upstream of the throttle 17 that varies according to the supercharging state by the turbocharger 20, An appropriate intake air amount corresponding to the accelerator opening APO can be obtained, and variations and fluctuations in engine torque due to the operating state / supercharging state of the turbocharger 20 can be effectively absorbed and reduced. . In addition, since the opening degree of the throttle 17 located immediately downstream is adjusted according to the throttle upstream pressure Pc, the calculation / control process is simpler than the feedback control as in the conventional example. However, the responsiveness is remarkably improved and the convergence is not lowered.

1 is a system configuration diagram of an internal combustion engine including a turbocharger according to an embodiment of the present invention. The flowchart which shows the flow of the setting control of the target throttle opening of a present Example. The characteristic view which shows the relationship between throttle opening, engine torque, and throttle upstream pressure. The characteristic view which shows the relationship between throttle downstream pressure, exhaust pressure, and engine speed. The characteristic view which shows the relationship between a throttle opening, the pressure ratio before and behind a throttle, and an engine speed. Time chart when starting acceleration to intermediate accelerator opening. Time chart when following the preceding vehicle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 11 ... Intake passage 17 ... Throttle 20 ... Turbocharger 22 ... Compressor 25 ... Engine control part (throttle control part)
26 ... accelerator opening sensor (accelerator opening detecting means)
31. Throttle upstream pressure detection sensor (throttle upstream pressure detection means)

Claims (4)

A control device for an internal combustion engine including a turbocharger having a turbocharger that supercharges intake air using exhaust and a throttle provided in an intake passage,
A throttle upstream pressure detecting means for detecting a throttle upstream pressure which is a pressure of an intake passage downstream of the compressor and upstream of the throttle of the turbocharger;
An accelerator opening detecting means for detecting the accelerator opening;
A throttle control unit for driving and controlling the throttle,
The throttle control unit calculates the target throttle opening based on the accelerator opening, and the target throttle opening increases as the throttle upstream pressure becomes higher than the reference pressure set between the maximum supercharging pressure and the atmospheric pressure. A control device for an internal combustion engine having a turbocharger, wherein the degree of throttle is corrected to the close side, and the target throttle opening is corrected to the open side as the throttle upstream pressure becomes lower than the reference pressure . Having engine speed detecting means for detecting engine speed;
2. The control device for an internal combustion engine having a turbocharger according to claim 1 , wherein the throttle control unit corrects the target throttle opening based on the engine speed. The control apparatus for an internal combustion engine with a turbocharger according to claim 2 , wherein the throttle control unit corrects the target throttle opening to the open side as the engine speed increases. A turbocharger that supercharges intake air using exhaust,
A throttle provided in the intake passage;
A throttle upstream pressure detecting means for detecting a throttle upstream pressure which is a pressure of an intake passage downstream of the compressor and upstream of the throttle of the turbocharger;
An accelerator opening detecting means for detecting the accelerator opening;
An internal combustion engine having a throttle control unit for driving and controlling the throttle,
The throttle control unit calculates the target throttle opening based on the accelerator opening, and the target throttle opening increases as the throttle upstream pressure becomes higher than the reference pressure set between the maximum supercharging pressure and the atmospheric pressure. A control method for an internal combustion engine provided with a turbocharger, wherein the degree of throttle is corrected to the close side, and the target throttle opening is corrected to the open side as the throttle upstream pressure becomes lower than the reference pressure .

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