JP2009030537A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of appropriately shifting from a single turbo mode to a twin turbo mode. <P>SOLUTION: The control device (50) of the internal combustion engine is disposed in an intake system and an exhaust system of the internal combustion engine, and equipped with a first supercharger (4) for performing supercharge, a second supercharger (5) disposed parallel to the first supercharger, an injection means (30R or the like) for performing a main injection and sub injection, and a control means (50) which controls the injection means to change an injection amount and an injection timing of the main injection in addition to or instead of changing the injection amount and the injection timing of the sub injection when changing over from the single turbo mode as an operating state in which the first supercharger is in operation to the twin turbo mode as an operating state in which both the first supercharger and the second supercharger are in operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that controls an internal combustion engine in which a plurality of superchargers are arranged in an intake passage and an exhaust passage.

  Conventionally, a technique has been proposed in which two superchargers are arranged in parallel in an intake system and an exhaust system, and the number of operating these superchargers is appropriately switched. Specifically, in an internal combustion engine in which a primary turbocharger and a secondary turbocharger are arranged in parallel, the secondary turbocharger is configured to have a larger capacity than the primary turbocharger. When the engine operating region is in the low speed region, only the primary turbocharger with a small capacity is operated (single turbo mode), and when the engine operating region is in the high speed region, the two superchargers are operated simultaneously (twin turbo mode). As a result, the output performance is improved from the low speed range to the high speed range. Such a supercharging system has been proposed.

  Specifically, when shifting from the single turbo mode to the twin turbo mode, the opening degree control is performed so that an exhaust flow rate change valve in the secondary turbocharger, a so-called exhaust switching valve, is opened. At this time, the pressure of the exhaust system caused by the change in the exhaust flow rate, that is, the so-called exhaust pressure, is reduced, so that the rotation of the turbine of the secondary turbocharger is affected to the rotation of the compressor, and consequently the secondary turbocharger. There is a possibility that the supercharging pressure when the primary turbocharger supercharges the internal combustion engine in addition to the supercharger will decrease. For this reason, the amount of intake air sucked into the internal combustion engine is reduced, and combustion is performed under an unexpected combustion state, so that the maximum pressure generated in the cylinder drops rapidly, and consequently the internal combustion engine. There is a possibility that a so-called torque step occurs.

  Therefore, in general, when shifting from the single turbo mode to the twin turbo mode, first, in the secondary turbocharger, a running operation for driving the internal combustion engine with the exhaust flow rate change valve closed is performed. ing.

  Further, in Patent Documents 1 and 2, etc., as a measure for preventing torque shock, a method of switching after adjusting the pressure by control of a variable mechanism for turbo capacity, or a fuel injection amount in the rich direction (Q increase) is taken. Techniques related to the technique are disclosed.

JP-A-5-296053 JP 10-274070 A

  However, in the supercharging system that performs the approach running as described above, when switching from the single turbo mode to the twin turbo mode, if the mode is suddenly changed, the change in the driving state of the internal combustion engine can be quickly handled. In other words, the supercharging pressure of the secondary turbocharger does not increase immediately, and a phenomenon occurs in which the torque temporarily drops. For this reason, a torque step occurs, and the driver may feel uncomfortable. Further, at this time, due to the change in the combustion state, the exhaust emission is deteriorated, or the degree of noise and vibration (so-called Noise Vibration) is increased.

  Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a control device for an internal combustion engine capable of appropriately shifting from a single turbo mode to a twin turbo mode.

In order to solve the above-described problems, an internal combustion engine control apparatus according to the present invention is arranged in an intake system and an exhaust system of an internal combustion engine, and in a first supercharger that performs supercharging, and in the intake system and the exhaust system A second supercharger disposed in parallel with the first supercharger and capable of supercharging together with the first supercharger; a main injection that is a primary fuel injection in the internal combustion engine; and The first supercharger and the second supercharger from the injection unit that performs the sub-injection that is the secondary injection and the single turbo mode that is the operation state in which the first supercharger is operating. When switching to the two-turbo mode, which is an operating state in which both are operating, in addition to or instead of changing at least one of the injection amount and injection timing of the sub-injection, the injection amount and injection of the main injection Said to change at least one of the times And control means for controlling the elevation means.

  According to the control device for an internal combustion engine according to the present invention, when switching from the single turbo mode to the dual turbo mode is performed suddenly, the injection unit is controlled under the control of the control unit. At least one of the injection amount and the injection timing of the sub injection is changed. In addition to or instead of this, at least one of the injection amount and the injection timing of the main injection is changed. Here, the injection timing according to the present invention means all temporal parameters and variables that can change the amount of fuel injected into the cylinder. The injection timing according to the present invention may directly or indirectly change the amount of fuel injected into the cylinder, for example, it may mean the timing of fuel injection, or it means the duration of continuing fuel injection. May be. Alternatively, it may mean the frequency of fuel injection, the number of times per unit time, or the time interval from one injection to the next injection, the so-called interval. In particular, with respect to the sub-injection, instead of stopping the sub-injection, the sub-injection is performed instead of stopping the sub-injection in a traveling region where noise and vibration are more effectively suppressed and in a traveling region where heat generated in the cylinder is reduced. The amount is preferably reduced. Therefore, it is possible to appropriately control the heat generation rate and the maximum pressure in the cylinder by the injection control in the sub-injection and the main injection, thereby reducing the degree of occurrence of the torque step. As a result, it is possible to effectively suppress a decrease in supercharging pressure when the first supercharger supercharges the internal combustion engine in addition to the second supercharger.

  As a result, it is possible to reduce the degree of occurrence of a torque step when switching from the single turbo mode to the dual turbo mode. Furthermore, it is possible to effectively suppress the deterioration of exhaust emission and the generation of noise and vibration when shifting from the single turbo mode to the dual turbo mode. Furthermore, when switching from the single turbo mode to the dual turbo mode, the rotational operation of the first and second superchargers is stabilized in response to the reduction in the generation of torque steps, resulting in repeated rotational operations. It is possible to reduce the stress and improve the durability of the internal combustion engine.

  In one aspect of the control apparatus for an internal combustion engine according to the present invention, the control means controls the injection means to stop the sub-injection when changing to the two-turbo mode.

  According to this aspect, the combustion and explosion of the main injection are not affected by the sub-injection. Therefore, by controlling the combustion state of the main injection, it is possible to appropriately and simply control the heat generation rate and the maximum pressure in the cylinder, and thereby suppress the degree of occurrence of a torque step. Specifically, for example, stopping the sub-injection peculiar to an internal combustion engine such as a diesel engine, so-called pilot injection, controls the combustion state of the main injection, so-called main injection, in the cylinder with high accuracy in advance. Is preferable.

  In another aspect of the control device for an internal combustion engine according to the present invention, an intake flow rate change valve disposed in the intake system and changing a flow rate of intake air flowing through the second supercharger, and provided in the exhaust system, An exhaust flow rate change valve that changes the flow rate of the exhaust gas flowing through the second supercharger, and the control means is configured to change the intake flow rate change valve and the exhaust flow rate change valve when changing to the two turbo mode. Of these, at least after the exhaust flow rate change valve is opened, the injection means is controlled.

  According to this aspect, after the exhaust flow rate change valve of the second supercharger that starts the supercharging operation is opened under the control of the control means, the injection amount in each of the sub-injection and the main injection by the injection means and The injection timing is changed. Therefore, since the number of revolutions of the second supercharger is sufficiently increased and the amount of exhaust gas is sufficiently increased, switching to the two-turbo mode is performed, so that the degree of occurrence of the torque step is effectively suppressed. It is possible.

  In particular, when switching from the single turbo mode to the dual turbo mode, the start of an appropriate supercharging operation of the second supercharger more effectively suppresses the deterioration of exhaust emissions and the generation of noise and vibration. It is possible.

  In another aspect of the control apparatus for an internal combustion engine according to the present invention, the control means is based on a first map in which the injection amount and the injection timing of the sub-injection are input information about the load or the rotational speed of the internal combustion engine. In addition to or instead of changing, the injection means is controlled while changing the injection amount and the injection timing of the main injection based on the second map having the load or the rotation speed of the internal combustion engine as input information. .

  According to this aspect, in addition to or instead of the injection control based on the first map in the sub-injection, the heat generation rate and the maximum pressure in the cylinder are appropriately and appropriately increased by the injection control based on the second map in the main injection. It is possible to control the accuracy and to quantitatively reduce the degree of occurrence of the torque step. These first and second maps can be defined so as to obtain a desired injection amount and injection timing based on theoretical, experimental, empirical, simulation and the like.

  In the aspect according to the above-mentioned control means, the control means further includes pressure measurement means for measuring the pressure in one or a plurality of cylinders of the internal combustion engine, and the control means corrects the first map based on the measured pressure. In addition to or instead, the injection unit may be controlled while correcting the second map based on the measured pressure.

  According to this configuration, in addition to or instead of the injection control based on the first map corrected based on the measured pressure in the secondary injection, the correction was performed based on the measured pressure in the main injection. With the injection control based on the second map, it is possible to control the heat generation rate and the maximum pressure in the cylinder more appropriately and with higher accuracy, and to further reduce the degree of occurrence of the torque step more quantitatively. .

  Furthermore, in the aspect according to the above-described control means, the control means, when the measured pressure is larger than a predetermined threshold, the first offset value defined based on a difference between the measured pressure and the predetermined threshold In addition to or in place of correcting the first map by adding to the first map, a second offset value defined based on the difference is added to the second map to add the second map to the first map. You may make it control the said injection | pouring means, correct | amending.

  If comprised in this way, addition of the 1st offset value in the 1st map and addition of the 2nd offset value in the 2nd map, for example, the variation of the quantity of the fuel adhering to the injector etc. It is possible to further reduce the degree of influence due to variations as internal factors, or variations as external factors of the internal combustion engine, such as the external temperature of the internal combustion engine.

  In the aspect according to the above-described control means, the control means is configured to perform the sub-change when the sub-change amount that is the change amount of the sub-injection and the injection timing defined by the first map is greater than a first predetermined value. In addition to or instead of setting the time interval required for changing by the change amount to be longer than the first reference value, the main injection amount and the change amount of the injection timing defined by the second map When the change amount is larger than the second predetermined value, the time interval required to change the main change amount may be set longer than the second reference value.

  With this configuration, the time interval required for changing the sub-change amount is adjusted. The time interval required to change the main change amount is adjusted. As a result, even when the load and the rotational speed of the internal combustion engine change suddenly during the run-up operation, changes in the rotational speed and rotational force of the turbine of the second supercharger are reduced and the rotation is stabilized. It is possible to wait for the traveling state to be completely switched to the two-turbo mode.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(1) Basic configuration
First, the overall configuration of a system to which the control device for an internal combustion engine according to the present embodiment is applied will be described. FIG. 1 is a schematic diagram illustrating a configuration of a vehicle to which a control device for an internal combustion engine according to the present embodiment is applied. In FIG. 1, solid arrows indicate gas flow, and broken arrows indicate signal input / output. FIG. 1 shows the gas flow when the single turbo mode is set.

  The vehicle mainly includes an air cleaner 2, an intake passage 3, turbochargers 4 and 5, an intake switching valve 6, a reed valve 7, an internal combustion engine 8, a supercharging pressure sensor 9, and an exhaust passage 10. And an EGR passage 11, an EGR valve 14, an exhaust gas switching valve 15, an exhaust gas bypass valve 16, injectors 30 </ b> R and 30 </ b> L, pressure sensors 40 </ b> R and 40 </ b> L, and an ECU (Engine Control Unit) 50.

  The air cleaner 2 purifies air (intake air) acquired from the outside and supplies it to the intake passage 3. The intake passage 3 is branched into intake passages 3a and 3b on the way. A compressor 4a of the turbocharger 4 is disposed in the intake passage 3a, and a compressor 5a of the turbocharger 5 is provided in the intake passage 3b. Is arranged. The compressors 4a and 5a compress the intake air that passes through the intake passages 3a and 3b, respectively.

  An intake switching valve 6 and a reed valve 7 are provided in the intake passage 3b. The intake switching valve 6 is configured to be opened and closed by a control signal S6 supplied from the ECU 50 so that the flow rate of intake air passing through the intake passage 3b can be adjusted. For example, by opening and closing the intake air switching valve 6, it is possible to switch the intake air flow / blockage in the intake passage 3b. The reed valve 7 is configured to open when the pressure in the passage exceeds a predetermined value. Further, a supercharging pressure sensor 9 is provided in the intake passage 3 on the downstream side of the compressors 4a and 4b. The supercharging pressure sensor 9 detects the pressure of supercharged intake air (hereinafter also referred to as “actual supercharging pressure”) and supplies a detection signal S9 corresponding to the actual supercharging pressure to the ECU 50. The intake switching valve 6 constitutes a specific example of the intake flow rate change valve according to the present invention.

  The internal combustion engine 8 is configured as a V-type 8-cylinder engine in which four cylinders (cylinders) 8La and 8Ra are provided in each of the left and right banks (cylinder groups) 8L and 8R. The internal combustion engine 8 is a device that generates power by burning an air-fuel mixture of intake air and fuel supplied from the intake passage 3. The internal combustion engine 8 is constituted by, for example, a gasoline engine or a diesel engine. The exhaust gas generated by the combustion in the internal combustion engine 8 is discharged to the exhaust passage 10.

  The operating state of the internal combustion engine 8 is under the control of the ECU 50 described later, injectors 30R and 30L for injecting fuel into the eight cylinders described above, and the fuel pressure supplied from the fuel pump (not shown) to the injectors 30R and 30L. Various devices such as a common rail pressure regulating valve for storing the power are operated and controlled. Specifically, under the control of the ECU 50 described later, the injectors 30R and 30L have a stoichiometric air-fuel ratio that is given as a mass ratio between the air sucked into the internal combustion engine 8 and the fuel added from the injectors 30R and 30L. The fuel is injected so that it is on the lean side.

  The state of the pressure inside the cylinder provided in the internal combustion engine 8 is measured by pressure sensors 40R and 40L. A signal S40 indicating the value of the measured pressure is supplied to the ECU 50. The injectors 30R and 30L constitute a specific example of the injection unit according to the present invention. Further, the pressure sensors 40R and 40L constitute a specific example of the pressure measuring means according to the present invention.

  An EGR passage 11 is connected in the exhaust passage 10. The EGR passage 11 has one end connected to the exhaust passage 10 and the other end connected to the intake passage 3. The EGR passage 11 is a passage for returning exhaust gas (EGR gas) to the intake system. Specifically, the EGR passage 11 is provided with an EGR cooler 12, an EGR valve 14, a bypass passage 11a, and a bypass valve 13. The EGR cooler 12 is a device that cools the EGR gas, and the EGR valve 14 is a valve that adjusts the flow rate of the EGR gas that passes through the EGR passage 11, in other words, a valve that adjusts the amount of EGR gas recirculated to the intake system. The opening degree of the EGR valve 14 is controlled by a control signal S14 supplied from the ECU 50. The bypass passage 11a is a passage that bypasses the EGR cooler 12, and a bypass valve 13 is provided on the passage. The bypass valve 13 adjusts the flow rate of EGR gas passing through the bypass passage 11a.

  The exhaust passage 10 is branched into exhaust passages 10a and 10b on the way. A turbine 4b of the turbocharger 4 is disposed in the exhaust passage 10a, and a turbine 5b of the turbocharger 5 is disposed in the exhaust passage 10b. The turbines 4b and 5b are rotated by exhaust gas passing through the exhaust passages 10a and 10b, respectively. The rotational torque of the turbines 4b and 5b is transmitted to the compressor 4a in the turbocharger 4 and the compressor 5a in the turbocharger 5 to rotate, whereby the intake air is compressed (that is, supercharged). ) The turbocharger 4 is configured as a low-capacity low-speed supercharger having a large supercharging capability in the low / medium speed range, and the turbocharger 5 is a large capacity having a large supercharging capability in the medium / high speed range. It is configured as a high-speed supercharger. An exhaust purification unit (not shown) including a DPNR catalyst (not shown) as an example of an NOx storage reduction catalyst as exhaust purification means is provided downstream of the turbines 4b and 5b, and a reducing agent is provided upstream of the DPNR catalyst. A fuel addition valve (not shown) as a fuel addition means for adding fuel may be provided.

  The turbocharger 4 includes a variable nozzle (VN) mechanism. The variable nozzle function is a mechanism for adjusting the supercharging amount by controlling the flow rate of the exhaust gas by controlling the opening degree of the nozzle vane provided on the upstream side of the turbine. The opening degree of the nozzle vane is controlled by a signal S19 supplied from the ECU 50.

  The turbocharger 4 is provided with a rotation speed sensor 4c that detects the turbo rotation speed, that is, the rotation speed of the turbine 4b. The rotation speed detection signal S18 output from the rotation speed sensor 4c is supplied to the ECU 50.

  An exhaust switching valve 15 is provided in the exhaust passage 10b, and an exhaust bypass passage 10ba is connected to the exhaust passage 10b. The exhaust gas switching valve 15 is controlled to be opened and closed by a control signal S15 supplied from the ECU 50, and is configured to be able to adjust the flow rate of the exhaust gas passing through the exhaust passage 10b. By opening and closing the exhaust gas switching valve 15, it is possible to switch the exhaust gas flow / blocking in the exhaust passage 10b. The exhaust bypass passage 10ba is configured as a passage that bypasses the exhaust passage 10b in which the exhaust switching valve 15 is provided. Specifically, the exhaust bypass passage 10ba has a smaller passage diameter than the exhaust passage 10b provided with the exhaust switching valve 15. An exhaust bypass valve 16 is provided in the exhaust bypass passage 10ba. The exhaust bypass valve 16 adjusts the flow rate of the exhaust gas passing through the exhaust bypass passage 10ba. The exhaust gas switching valve 15 constitutes a specific example of the exhaust flow rate changing valve according to the present invention.

  When the intake switching valve 6, the exhaust switching valve 15, and the exhaust bypass valve 16 are all closed, intake and exhaust gas are supplied only to the turbocharger 4, and intake and exhaust gas are supplied to the turbocharger 5. Is not supplied. Therefore, only the turbocharger 4 operates, and the turbocharger 5 does not operate. On the other hand, when the intake switching valve 6 is open and either the exhaust switching valve 15 or the exhaust bypass valve 16 is open, intake and exhaust gas are supplied to both the turbochargers 4 and 5. Therefore, both turbochargers 4 and 5 operate.

  The ECU 50 includes a CPU, a ROM, a RAM, an A / D converter, and the like (not shown). The ECU 50 performs in-vehicle control based on outputs supplied from various sensors in the vehicle. Specifically, the ECU 50 acquires the actual boost pressure from the boost pressure sensor 9, and based on the actual boost pressure and the like, the intake air switching valve 6, the EGR valve 14, the exhaust gas switching valve 15, and the exhaust gas bypass. Control the valve 16 and the like.

  In the above configuration, the turbocharger 4 is a specific example of the first supercharger according to the present invention, and the turbocharger 5 is a specific example of the second supercharger according to the present invention. . The ECU 50 is a specific example of the control means according to the present invention.

  In the present embodiment, the ECU 50 mainly controls the intake air switching valve 6, the exhaust gas switching valve 15, and the exhaust gas bypass valve 16 to operate only the turbocharger 4 (“one turbo mode”). And a mode for operating both turbochargers 4 and 5 (referred to as “two turbo mode”). Specifically, the ECU 50 executes switching from the single turbo mode to the double turbo mode and switching from the double turbo mode to the single turbo mode based on, for example, the engine speed and the required torque. .

  Here, basic control executed when switching between the single turbo mode and the dual turbo mode will be briefly described. As described above, the mode is switched by the ECU 50 controlling the intake switching valve 6, the exhaust switching valve 15, and the exhaust bypass valve 16 based on the engine speed and the required torque. Specifically, when switching from the single turbo mode to the dual turbo mode, the ECU 50 controls the intake switching valve 6, the exhaust switching valve 15, and the exhaust bypass valve 16 from closed to open. In this case, the ECU 50 basically performs switching by opening the exhaust bypass valve 16, the exhaust switching valve 15, and the intake switching valve 6 in this order. More specifically, the exhaust bypass valve 16 is first opened little by little, the exhaust switching valve 15 is opened when a predetermined condition is satisfied in this state, and then the intake switching valve 6 is opened. In this case, the exhaust bypass valve 16 is first opened a little by supplying the turbocharger 5 with a relatively small flow rate of exhaust gas (because the diameter of the exhaust bypass passage 10ba is small). Is to gradually operate (ie, run up). In other words, by opening the exhaust gas switching valve 15 first, it is possible to prevent a relatively large flow rate of exhaust gas from flowing into the turbocharger 5 at a stretch and causing a torque shock or the like. On the other hand, when switching from the two turbo mode to the single turbo mode, the ECU 50 controls the intake switching valve 6, the exhaust switching valve 15, and the exhaust bypass valve 16 from opening to closing in the same manner as described above.

  FIG. 2 schematically shows an operation region map of the single turbo mode and the double turbo mode. In the graph of FIG. 2, the horizontal axis indicates the engine speed, the left vertical axis indicates the required torque (fuel injection amount), and the right vertical axis indicates the turbo speed. In FIG. 2, the solid line 71 indicates the operating characteristics of the single turbo mode, and the broken line 72 indicates the operating characteristics of the double turbo mode. When the operating point determined by the engine speed and the required torque (fuel injection amount) is below the solid line 71, the internal combustion engine operates in the single turbo mode. When the engine speed and torque increase and the operating point enters a region above the solid line 71, the internal combustion engine operates in the two-turbo mode. That is, when the operating point is below the switching line surrounded by the broken line 74, the single turbo mode is selected, and when the operating point is above the double line 74, the two turbo mode is selected.

  A solid line 73 indicates the relationship between the engine speed and the turbo speed of the turbocharger 4. Basically, the turbo speed increases as the engine speed increases. The turbo rotation speed is detected by the rotation speed sensor 4c described above.

  Regarding basic control executed when switching between the single turbo mode and the dual turbo mode, more specifically, as described above, turbocharging is performed when switching from the single turbo mode to the dual turbo mode. Although the machine 5 is running up, the rotation of the turbocharger 5 does not increase immediately, so the torque temporarily decreases, and a so-called torque step may occur. As described above, the torque step is caused by the time required for the rotation of the turbocharger 5 to increase. However, when the switching from the single turbo mode to the double turbo mode is performed relatively slowly, Hardly occurs or even if it occurs, the level difference is small. On the other hand, when the switching from the single turbo mode to the double turbo mode is suddenly performed, such as during sudden acceleration, the torque step becomes large, which is generally a problem. When switching from the single turbo mode to the dual turbo mode is performed in the low speed (low torque) region, the torque step becomes large, and when switched in the high torque (high intake air amount) region, the torque step becomes small. . Therefore, when switching from the single turbo mode to the dual turbo mode, it is preferable to switch to the dual turbo mode after sufficiently increasing the torque by the turbocharger 4.

(2) Method of controlling fuel injection when switching from single turbo mode to dual turbo mode Next, with reference to FIGS. 3 to 6, the control method for an internal combustion engine according to the present embodiment is applied. A fuel injection control method when switching from the single turbo mode to the dual turbo mode will be described.

(2-1) Operating principle (Overall processing)
First, with reference to FIG. 3 and FIG. 4, the overall process in the operation principle of fuel injection when switching from the single turbo mode to the dual turbo mode according to the present embodiment will be described. FIG. 3 is a flowchart showing the flow of the entire fuel injection control process when switching from the single turbo mode to the dual turbo mode according to this embodiment. The fuel injection control process at the time of mode switching is repeatedly executed by the ECU at a predetermined cycle such as several tens of microseconds or several microseconds. FIG. 4 is a schematic diagram illustrating a predetermined map in which the operation amount of the injection system according to the present embodiment is defined by using the load of the internal combustion engine or the rotational speed of the internal combustion engine as input information.

  As shown in FIG. 3, under the control of the ECU 50, the opening state of the exhaust gas switching valve 15 is detected (step S101).

  Next, under the control of the ECU 50, it is determined whether or not the detected opening state of the exhaust gas switching valve 15 is a valve opening state (step S102). If the result of this determination is that the opening degree of the exhaust gas switching valve 15 is open (step S102: Yes), the opening degree state of the intake air switching valve 6 is detected under the control of the ECU 50 (step S103). ).

  Next, under the control of the ECU 50, it is determined whether or not the detected opening degree of the intake air switching valve 6 is a valve closing state (step S104). As a result of this determination, if the opening degree of the intake air switching valve 6 is in the closed state (step S104: Yes), the injection system is determined under the control of the ECU 50, for example, based on the travel region of the internal combustion engine. It is determined whether or not the operation amount is greater than a certain value (step S105). In particular, the traveling state in which the exhaust gas switching valve 15 is in the open state and the intake air switching valve 6 is in the closed state as described above may mean the above-described running operation.

  Here, the operation amount of the injection system according to the present embodiment includes the injection amount of the secondary injection (so-called pilot injection), the injection timing of the secondary injection, the injection amount of the main injection (so-called main injection), and the main injection. It may mean a physical quantity indicating at least one of the injection timings. In this pilot injection, a kind of fire type is generated in the cylinder in advance, and the pressure change can be moderated for combustion and explosion by the main injection. Specifically, as an example of the operation amount of the injection system, the injection amount of pilot injection, the time interval for performing pilot injection, the injection amount of main injection, and the amount of change that changes the injection timing of main injection to the advance side And so on. More specifically, as shown in FIG. 4, the operation amounts of these injection systems are uniquely defined based on a predetermined map using the load of the internal combustion engine or the rotation speed of the internal combustion engine as input information. Good. More specifically, in the predetermined map, for example, the injection amount of the main injection is defined so as to increase as the load on the internal combustion engine increases and the rotation speed of the internal combustion engine increases. The predetermined map described above can be defined so as to obtain a desired operation amount of the injection system based on theoretical, experimental, empirical, simulation, or the like. In addition, the specific map constitutes a specific example of the first map or the second map according to the present invention. Further, a specific example of the injection amount and the injection timing according to the present invention is configured by the operation amount of the injection system described above.

  As a result of the determination in step S105 described above, for example, when it is determined that the operation amount of the injection system, which is determined based on the travel region of the internal combustion engine, is greater than a certain value (step S105: Yes), under the control of the ECU 50, The time interval until the operation amount in the sub-injection or main injection reaches a predetermined value, in other words, the time interval required for the operation is, for example, relatively long based on the difference between the operation amount of the injection system and a constant value. (Step S106). On the other hand, as a result of the determination in step S105 described above, for example, when it is not determined that the operation amount of the injection system, which is determined based on the travel region of the internal combustion engine, is greater than a certain value (step S105: No), The operation amount is set to be zero (step S107).

  On the other hand, as a result of the determination in step S104 described above, when the opening degree of the intake air switching valve 6 is not the valve closing state but the valve opening state (step S104: No), the operation of the injection system is controlled under the control of the ECU 50. It is determined whether or not it is the first time to operate the target, in other words, whether or not it is the second time to operate the operation target of the injection system (step S108). In particular, the traveling state in which the exhaust gas switching valve 15 is in the open state and the intake air switching valve 6 is in the open state in this way is the traveling state during the switching from the single turbo mode to the dual turbo mode. It may mean a state.

  As a result of the determination in step S108 described above, if it is not the first time to operate the operation target of the injection system, in other words, the second time to operate the operation target of the injection system (step S108: Yes), the cylinder is controlled under the control of the ECU 50. The maximum value of the pressure in the cylinder is measured by a pressure sensor that measures the pressure in the cylinder (step S109).

  Next, when switching from the single turbo mode to the dual turbo mode under the control of the ECU 50, a value indicating the pressure in a general cylinder is acquired (step S110). Specifically, the value indicating the maximum value of the pressure in a general cylinder at the time of this mode switching is based on, for example, a map or function that defines the load of the internal combustion engine or the rotation speed of the internal combustion engine as input information, It may be acquired uniquely.

  Next, under the control of the ECU 50, it is determined whether or not the measured maximum value of pressure in the cylinder is smaller than a value indicating the maximum value of pressure in a general cylinder (step S111). Here, when it is determined that the measured maximum value of the pressure in the cylinder is smaller than a value indicating the maximum value of the pressure in the general cylinder (step S111: Yes), the above-described control is performed under the control of the ECU 50. An offset amount for adding or subtracting a predetermined map that can define the operation amount of the injection system is calculated (step S112). Specifically, under the control of the ECU 50, the injection amount of the pilot injection is reduced based on the difference between the measured maximum value of the cylinder pressure and the value indicating the maximum value of the general cylinder pressure. An offset amount that changes in the direction to be generated may be calculated. While the fuel whose injection amount is set in consideration of the calculated offset amount is injected into an injection means such as an injector, the generation of noise and vibration in the cylinder is more effectively suppressed, It is possible to control the heat generation rate and the maximum pressure in the cylinder so as to increase appropriately, thereby reducing the degree of occurrence of the torque step. In detail, in the fuel injection by the injection means, the offset amount is considered to be a variation as an internal factor of the internal combustion engine, such as a variation in the amount of fuel adhering to the injector or the like, or, for example, an external environment of the internal combustion engine. This is very preferable from the viewpoint of reducing the degree of the influence of variations such as temperature as external factors of the internal combustion engine.

  On the other hand, as a result of the determination in step S111, when it is not determined that the measured maximum value of the pressure in the cylinder is smaller than the value indicating the maximum value of the pressure in the general cylinder (step S111: No), the ECU 50 is further determined. Under the control, it is determined whether or not the measured maximum value of the pressure in the cylinder is larger than the upper limit value of the allowable range determined from the viewpoint of durability or mechanism of the internal combustion engine (step S113). Here, when it is determined that the measured maximum value of the pressure in the cylinder is larger than the upper limit value of the allowable range determined from the viewpoint of durability or mechanism of the internal combustion engine (step S113: Yes), the above-described case is made. The operation amount of the injection system is set to be zero (step S114). On the other hand, as a result of the determination in step S113 described above, when it is not determined that the maximum value of the measured pressure in the cylinder is larger than the upper limit value of the allowable range determined from the viewpoint of durability or mechanism of the internal combustion engine (step S113: No), step S114 is omitted. As a result, the ECU 50 can acquire the operation amount of the injection system using the above-described predetermined map as it is.

  Next, a process for actually operating the operation amount of the injection system is performed under the control of the ECU 50 (step S115).

(2-2) Operating principle (Injection system operation processing)
Next, referring to FIG. 6 in addition to FIG. 5, an operation process of the injection system in the operation principle of the fuel injection when switching from the single turbo mode to the dual turbo mode according to the present embodiment will be described. FIG. 5 is a flowchart showing a part of the fuel injection control process when switching from the single turbo mode to the dual turbo mode according to the present embodiment. FIG. 6 is a timing chart schematically showing the operation timing of fuel injection when switching from the single turbo mode to the dual turbo mode according to the present embodiment.

  As shown in FIG. 5, first, under the control of the ECU 50, it is determined whether or not the operation amount of the injection system is set to be zero in the above-described step S107 or S114 (step S201). If the operation amount of the injection system is set to be zero (step S201: Yes), the operation amount is actually set to zero (step S202). On the other hand, if the result of determination in step S201 is that the operation amount of the injection system is not set to be zero (step S201: No), the load on the internal combustion engine shown in FIG. Alternatively, the operation amount of the injection system is determined based on a predetermined map using the rotation speed of the internal combustion engine as input information (step S203).

  Next, under the control of the ECU 50, for example, the determined operation amount of the injection system is added or subtracted by the offset amount calculated in step S112 described above (step S204).

  Next, under the control of the ECU 50, for example, various parameters and variables such as the time interval required for the operation calculated in step S106 described above are actually set (step S205).

  Next, under the control of the ECU 50, the injection means such as an injector is driven based on various operation amounts of the injection system actually set as described above (step S206).

  As described above, (i) the traveling state in which the exhaust gas switching valve 15 is in the open state and the intake air switching valve 6 is in the open state is being switched from the single turbo mode to the dual turbo mode. (Ii) The fuel injection control process is different in the running operation in which the exhaust gas switching valve 15 is in the open state and the intake air switching valve 6 is in the closed state. Therefore, it is possible to appropriately control the heat generation rate and the maximum pressure in the cylinder by the injection control in the pilot injection and the main injection, thereby reducing the degree of occurrence of the torque step. As a result, it is possible to effectively suppress a decrease in supercharging pressure when the first supercharger supercharges the internal combustion engine in addition to the second supercharger.

  Specifically, as shown in FIG. 6, (i) the exhaust switching valve 15 is in the open state and the intake switching valve 6 is switched from the single turbo mode to the dual turbo mode. In the running state in the middle, the first time counted by the operation counter of the injection system is based on a predetermined map shown in FIG. 4 described above with the load of the internal combustion engine or the rotational speed of the internal combustion engine as input information. An injection means such as an injector is driven based on the determined operation amount of the injection system. Subsequently, in the second and subsequent times, an injection unit such as an injector is driven while an offset amount is added to or subtracted from an operation amount of the injection system determined based on a predetermined map.

  On the other hand, as shown in FIG. 6, in the run-up operation in which (ii) the exhaust gas switching valve 15 is in the open state and the intake air switching valve 6 is in the closed state, sub-injection or main fuel is controlled under the control of the ECU 50. The time interval until the operation amount in injection (that is, one specific example of the sub-change amount or the main change amount according to the present invention) reaches a predetermined value is adjusted. As a result, even when the load and the rotational speed of the internal combustion engine change suddenly during the run-up operation, changes in the rotational speed and rotational force of the turbine of the second supercharger are reduced and the rotation is stabilized. It is possible to wait for the traveling state to be completely switched to the two-turbo mode.

(3) Examination of action and effect of this embodiment
Next, with reference to FIG.7 and FIG.8, the effect | action and effect which concern on this embodiment are examined. Here, FIG. 7 shows the injection amount and the injection timing corresponding to the pilot injection and the main injection, respectively, in the cylinder when switching from the single turbo mode to the dual turbo mode according to the comparative example and the present embodiment. It is the schematic diagram (FIG. 7 (a) and FIG.7 (b)) which showed the relationship with the change of a pressure. 7 (a) and 7 (b), the dotted line indicates the change in the pressure in the cylinder after switching from the single turbo mode to the dual turbo mode, and the solid line indicates from the single turbo mode. The change in the pressure in the cylinder after switching to the two-turbo mode is shown. FIG. 8 shows the timing when the exhaust gas switching valve or the intake air switching valve is opened, the change in the torque generated in the internal combustion engine, when the switching from the single turbo mode to the dual turbo mode is performed, It is the graph which showed the change of the opening degree of the variable nozzle in a supercharger and a 2nd supercharger, the lift amount of an EGR valve, the change of the generation amount of Nox, and the change of the generation amount of Smoke in time series.

  As shown by the dotted line in FIG. 7A, according to the study by the inventors of the present application, in the fuel injection control according to the comparative example, after switching from the single turbo mode to the dual turbo mode, It has been found that the pressure in the cylinder changes to the decreasing side. Specifically, when shifting from the single turbo mode to the dual turbo mode, the opening degree control is performed so as to open the exhaust flow rate change valve, so-called exhaust switching valve, in the second supercharger. . At this time, the pressure of the exhaust system due to the change in the exhaust flow rate, that is, the so-called exhaust pressure, decreases, so that the rotation of the turbine of the second supercharger is affected to the rotation of the compressor, and consequently the second excess There is a possibility that the supercharging pressure when the first supercharger supercharges the internal combustion engine in addition to the supercharger will decrease. For this reason, the amount of intake air sucked into the internal combustion engine is reduced, and combustion is performed under an unexpected combustion state, so that the maximum pressure generated in the cylinder drops rapidly, and consequently the internal combustion engine. There is a possibility that a so-called torque step occurs.

  On the other hand, according to the present embodiment, as shown in FIG. 7B, the pilot injection is stopped or the injection amount of the pilot injection is changed to the decreasing side. In addition to or instead of this, the injection amount of the main injection is changed to the increasing side by changing the injection timing of the main injection or changing the injection time of the main injection. Therefore, it is possible to appropriately control the heat generation rate and the maximum pressure in the cylinder by the injection control in the pilot injection and the main injection, thereby reducing the degree of occurrence of the torque step. As a result, it is possible to effectively suppress a decrease in supercharging pressure when the first supercharger supercharges the internal combustion engine in addition to the second supercharger.

  As a result, according to the present embodiment, it is possible to reduce the degree of occurrence of a torque step when switching from the single turbo mode to the dual turbo mode. Furthermore, it is possible to effectively suppress the deterioration of exhaust emission and the generation of noise and vibration when shifting from the single turbo mode to the dual turbo mode. Furthermore, when switching from the single turbo mode to the dual turbo mode, the rotational operation of the first and second superchargers is stabilized in response to the reduction in the generation of torque steps, resulting in repeated rotational operations. It is possible to reduce the stress and improve the durability of the internal combustion engine.

  Specifically, as shown by the dotted-line ellipse in FIG. 8 (a), after the opening degree of the exhaust gas switching valve according to the present embodiment is fully opened, the intake air switching valve is connected together with the exhaust gas switching valve. A large change in the torque generated in the internal combustion engine by appropriately controlling the heat generation rate and the maximum pressure in the cylinder of the internal combustion engine during the travel period in which the single turbo mode is switched to the double turbo mode including the period in which the engine is fully open Can be suppressed, and as a result, the degree of occurrence of a torque step can be reduced. In addition, the dotted line in the ellipse of the dotted line of Fig.8 (a) shows the change of the torque which concerns on the comparative example mentioned above. Further, in FIG. 8 (b), the change in the opening degree of the variable nozzle of the first supercharger, the change in the opening degree of the variable nozzle of the second supercharger corresponding to FIG. 8 (a), and The change of the opening degree of an EGR valve is shown. FIG. 8C shows the change in the amount of NOx generated and the change in the amount of smoke (so-called soot) corresponding to FIG. 8A described above. The amount of NOx generated and the amount of smoke generated can be reduced as the degree of occurrence of a torque step when switching from the single turbo mode to the double turbo mode is reduced.

  As another embodiment of the above-described embodiment, (i) the exhaust switching valve 15 is in the open state and the intake switching valve 6 is switched from the single turbo mode to the dual turbo mode. The fuel injection control process does not differ between the running state during the running and the run-up operation in which (ii) the exhaust gas switching valve 15 is in the open state and the intake air switching valve 6 is in the closed state. Good. For example, when the exhaust gas switching valve 15 is in the open state, the processing after step S108 described above, that is, the measurement is always performed regardless of whether the intake air switching valve 6 is in the closed state or the open state. A fuel injection control process may be performed based on whether or not the maximum pressure value is smaller than a general value indicating the maximum pressure in the cylinder. As a result, the fuel injection control process can be made simple and quick, and the memory capacity stored in the ECU 50 or the like can be saved.

  The present invention is not limited to the above-described embodiments, and may be implemented in various forms. For example, the present invention is not limited to a diesel engine, and may be applied to various internal combustion engines that use gasoline or other fuels.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and the control of the internal combustion engine accompanying such a change. The apparatus is also included in the technical scope of the present invention.

1 is a schematic diagram showing a configuration of a vehicle to which a control device for an internal combustion engine according to an embodiment is applied. The operation area | region map of 1 turbo mode and 2 turbo mode is shown roughly. It is the flowchart which showed the flow of the whole process of the control process of the fuel injection at the time of switching from 1 turbo mode to 2 turbo mode based on this embodiment. It is the schematic diagram which showed the predetermined map which prescribed | regulated the operation amount of the injection system which concerns on this embodiment as the input information on the load of the internal combustion engine, or the rotation speed of the internal combustion engine. It is the flowchart which showed the flow of a part of control process of the fuel injection at the time of switching from 1 turbo mode to 2 turbo mode based on this embodiment. 6 is a timing chart schematically showing the operation timing of fuel injection when switching from the single turbo mode to the dual turbo mode according to the present embodiment. The relationship between the injection amount and the injection timing corresponding to the pilot injection and the main injection, and the change in the pressure in the cylinder when switching from the single turbo mode to the dual turbo mode according to the comparative example and the present embodiment. It is the schematic diagram shown (Fig.7 (a) and FIG.7 (b)). According to the present embodiment, when switching from the single turbo mode to the dual turbo mode, the timing when the exhaust gas switching valve or the intake gas switching valve is opened, the change in torque generated in the internal combustion engine, the first supercharger, It is the graph which showed the change of the opening degree of the variable nozzle in a 2nd supercharger, the lift amount of an EGR valve, the change of the generation amount of Nox, and the change of the generation amount of Smoke in time series.

Explanation of symbols

2 Air cleaner 3 Intake passage 4, 5 Turbocharger 4a, 5a Compressor 4b, 5b Turbine 6 Intake switching valve 8 Internal combustion engine 8a Cylinder 9 Supercharging pressure sensor 10 Exhaust passage 15 Exhaust switching valve 16 Exhaust bypass valve 30R, 30L Injector 40R 40L Pressure sensor 50 ECU

Claims (7)

A first supercharger that is arranged in an intake system and an exhaust system of an internal combustion engine and performs supercharging;
A second supercharger that is arranged in parallel with the first supercharger in the intake system and the exhaust system, and is superchargeable together with the first supercharger;
In the internal combustion engine, injection means for performing main injection that is primary injection of fuel and sub-injection that is secondary injection of the fuel;
Switching from the single turbo mode in which the first supercharger is operating to the dual turbo mode in which the first supercharger and the second supercharger are operating together In this case, in addition to or instead of changing at least one of the injection amount and the injection timing of the sub-injection, the injection means is configured to change at least one of the injection amount and the injection timing of the main injection. And a control means for controlling the internal combustion engine.   2. The control device for an internal combustion engine according to claim 1, wherein the control unit controls the injection unit to stop the sub-injection when the two-turbo mode is changed. 3. An intake flow rate change valve that is arranged in the intake system and changes a flow rate of intake air flowing through the second supercharger;
An exhaust flow rate change valve provided in the exhaust system and configured to change a flow rate of exhaust gas flowing through the second supercharger;
The control means controls the injection means after opening at least the exhaust flow rate change valve among the intake flow rate change valve and the exhaust flow rate change valve when changing to the two turbo mode. The control apparatus for an internal combustion engine according to claim 1 or 2.   In addition to or instead of changing the injection amount and the injection timing of the sub-injection based on the first map using the load or the rotation speed of the internal combustion engine as input information, the control means performs the injection of the main injection. 4. The injection means is controlled while changing the amount and the injection timing based on a second map having the load or rotation speed of the internal combustion engine as input information. 5. The control apparatus for an internal combustion engine according to the item. Pressure measuring means for measuring pressure in one or more cylinders of the internal combustion engine,
The control means controls the injection means while correcting the second map based on the measured pressure in addition to or instead of correcting the first map based on the measured pressure. The control apparatus for an internal combustion engine according to claim 4, wherein   When the measured pressure is greater than a predetermined threshold, the control means adds a first offset value defined based on a difference between the measured pressure and the predetermined threshold to the first map. In addition to or instead of correcting one map, the second offset value defined based on the difference is added to the second map to control the injection means while correcting the second map. The control device for an internal combustion engine according to claim 5.   When the sub-change amount, which is a change amount of the sub-injection and injection timing defined by the first map, is greater than a first predetermined value, the control means takes a time required to change the sub-change amount. In addition to or instead of setting the interval to be longer than the first reference value, the main change amount, which is the change amount of the main injection and the injection timing defined by the second map, is greater than a second predetermined value. The internal combustion engine control apparatus according to any one of claims 4 to 6, wherein a time interval required for changing the main change amount is set to be longer than a second reference value.

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