JP2010151087A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly suppress a torque level difference by carrying out post-injection at changing from a single turbo mode to a twin turbo mode. <P>SOLUTION: A controller for an internal combustion engine is suitably applied to a system equipped with a first supercharger and a second supercharger. A post-injection control means carries out post-injection in response to control for carrying out changing in changing from a mode of operating the first supercharger to a mode of operating the first supercharger and the second supercharger. By this, exhaust temperature is raised (that is to say, exhaust energy is increased) by the post-injection, and a coefficient of expansion can be improved. Therefore, dropping of the number of revolutions of a turbine of the first supercharger at changing can be recovered, and dropping of a boost pressure can be suppressed. Consequently, the torque level difference at changing can be properly suppressed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine including a plurality of superchargers.

  Conventionally, a technology has been proposed in which two turbochargers (primary turbocharger and secondary turbocharger) are arranged in parallel in the intake system and the exhaust system, and the number of operating these turbochargers is appropriately switched. . Specifically, a control is proposed that is performed when switching between a mode in which only the primary turbocharger is operated and a mode in which both the primary turbocharger and the secondary turbocharger are operated. ing. In the following, the mode for operating only the primary turbocharger is referred to as “single turbo mode”, and the mode for operating both the primary turbocharger and the secondary turbocharger is referred to as “twin turbo mode”. .

  For example, Patent Document 1 discloses a technique for suppressing a torque step at the time of switching by correcting the throttle opening and keeping the amount of change in the intake air constant when switching from the single turbo mode to the twin turbo mode. Proposed. Patent Document 2 proposes a technique for suppressing the torque step at the time of switching by controlling the variable valve timing mechanism when switching from the single turbo mode to the twin turbo mode to increase the engine output. .

Japanese Patent Laid-Open No. 11-50867 Japanese Patent Laid-Open No. 5-288089

  However, since the technique described in Patent Document 1 described above only corrects the throttle opening, there is a case where the decrease in the supercharging pressure cannot be compensated for at the time of switching. In addition, this technology has been difficult to apply to diesel engines. On the other hand, the technique described in Patent Document 2 is difficult to apply to a system that does not include a variable valve timing mechanism.

  The present invention has been made to solve the above-described problems, and an internal combustion engine capable of appropriately suppressing a torque step by performing post-injection when switching from a single turbo mode to a twin turbo mode. An object of the present invention is to provide an engine control device.

  In one aspect of the present invention, a control device for an internal combustion engine including a first supercharger and a second supercharger is configured to perform the first supercharger from a mode in which the first supercharger is operated. At the time of switching to a mode in which the charger and the second supercharger are operated, post injection control means for performing post injection according to control for performing the switching is provided.

  The above control device for an internal combustion engine is suitably applied to a system including a first supercharger and a second supercharger. Specifically, the post injection control means performs the switching at the time of switching from the mode for operating the first supercharger to the mode for operating the first supercharger and the second supercharger. Post injection is performed according to the control. By doing so, the exhaust temperature rises (that is, the exhaust energy increases) by post injection, and the expansion rate can be improved. Therefore, it is possible to recover the decrease in the rotational speed of the turbine of the first supercharger at the time of switching, and it is possible to suppress the decrease in the supercharging pressure. Therefore, it is possible to appropriately suppress the torque step at the time of switching.

  In one aspect of the control device for an internal combustion engine, the control device includes an exhaust gas switching valve control unit that performs control for slightly opening the exhaust gas switching valve to perform preliminary rotation of the second supercharger at the time of the switching, The post-injection control means performs the post-injection according to the opening of the exhaust gas switching valve during execution of the control for slightly opening the exhaust gas switching valve by the exhaust gas switching valve control means.

  According to this aspect, it is possible to appropriately suppress a decrease in the supercharging pressure during the control for pre-rotating the second supercharger (that is, during the running period).

  In another aspect of the control apparatus for an internal combustion engine, the post-injection control unit is configured to gradually open the intake switching valve after the exhaust switching valve control unit performs a slight opening of the exhaust switching valve. During the execution of the above, the fuel injection amount for performing the post injection is increased.

  According to this aspect, it is possible to smoothly shift from the mode for operating the first supercharger to the mode for operating the first supercharger and the second supercharger.

  In another aspect of the control apparatus for an internal combustion engine, the post-injection control means continues the post-injection until the supercharging pressure reaches a target supercharging pressure after the exhaust gas switching valve is fully opened. To do.

  According to this aspect, it is possible to suppress a rapid decrease in the supercharging pressure after the transition to the mode for operating the first supercharger and the second supercharger is completed.

  In a preferred embodiment, the first supercharger and the second supercharger are arranged in parallel to the intake passage and the exhaust passage. In other words, the control device for the internal combustion engine can be applied to a parallel twin turbo system (parallel sequential turbo system).

  Preferred embodiments of the present invention will be described below with reference to the drawings.

[Device 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. In addition, in FIG. 1, the gas flow at the time of setting to single turbo mode is shown.

  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 engine (internal combustion engine) 8, an exhaust passage 10, an intercooler. 12, a surge tank 13, an exhaust gas switching valve 15, an exhaust bypass passage 16, an exhaust bypass valve 17, a boost pressure sensor 21, an intake bypass passage 31, an intake bypass valve 32, 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 disposed in the intake passage 3b. The compressors 4a and 5a compress the intake air that passes through the intake passages 3a and 3b, respectively.

  An intake switching valve 6 is provided in the intake passage 3b. The intake switching valve 6 is controlled in opening degree by a control signal S6 supplied from the ECU 50 via an actuator (not shown) to adjust the flow rate of the intake air passing through the intake passage 3b. 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. Furthermore, in the intake passage 3 on the downstream side of the compressors 4a and 5a, in order from the upstream side, an intercooler 12 for cooling the intake air, a surge tank 13 for storing the intake air, and the pressure of the supercharged intake air (supercharging pressure). A supercharging pressure sensor 21 for detecting is provided. The supercharging pressure sensor 21 supplies a detection signal S21 corresponding to the detected supercharging pressure to the ECU 50.

  One end of the intake bypass passage 31 is connected to the intake passage 3 between the air cleaner 2 and the compressor 4a, and the other end is connected to the intake passage 3b between the compressor 5a and the intake air switching valve 6. The intake bypass passage 31 guides intake air introduced from the air cleaner 2 side to the downstream side of the compressors 4a and 5a, bypassing the compressors 4a and 5a. An intake bypass valve 32 is provided in the intake bypass passage 31. The intake bypass valve 32 is opened when the pressure in the passage exceeds a predetermined level.

  The 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 engine 8 is constituted by, for example, a diesel engine. Exhaust gas generated by combustion in the engine 8 is discharged to the exhaust passage 10. The engine 8 is controlled in various ways by control signals supplied from the ECU 50. For example, control related to fuel injection is performed.

  Here, a specific configuration of the engine 8 will be described with reference to FIG. FIG. 2 is a schematic configuration diagram of the engine 8 in FIG. A solid line arrow in the figure shows an example of a gas flow.

  The engine 8 mainly includes a fuel injection valve (injector) 8b, a cylinder 8c, a piston 8d, a connecting rod 8e, an intake valve 8g, and an exhaust valve 8h. In FIG. 2, only one cylinder 8c is shown for convenience of explanation, but the engine 8 actually has a plurality of cylinders. The engine 1 is configured as a diesel engine.

  Intake air (air) introduced from the outside passes through the intake passage 3, and the flow rate of the intake air passing through the intake passage 3 is adjusted by a throttle valve (not shown). The intake air that has passed through the intake passage 3 is supplied to the combustion chamber 8ca formed by the cylinder 8c. The fuel injected by the fuel injection valve 8b is supplied to the combustion chamber 8ca. In the fuel injection valve 8b, the fuel injection timing, the fuel injection amount, and the like are controlled by a control signal S8 supplied from the ECU 50.

  The combustion chamber 8ca is provided with an intake valve 8g and an exhaust valve 8h. The intake valve 8g opens / closes to control conduction / interruption between the intake passage 3 and the combustion chamber 8ca. The intake valve 8g may be configured such that the valve timing (valve opening timing or valve closing timing) can be controlled by a variable valve timing mechanism. On the other hand, the exhaust valve 8h controls opening / closing of the exhaust passage 10 and the combustion chamber 8ca by opening and closing.

  In the combustion chamber 8ca, the mixture of the intake air and fuel supplied as described above is compressed and burned by self-ignition. In this case, the piston 8d reciprocates due to combustion, the reciprocating motion is transmitted to the crankshaft (not shown) via the connecting rod 8e, and the crankshaft rotates. Exhaust gas generated by combustion in the combustion chamber 8ca is exhausted from the exhaust passage 10.

  Returning to FIG. 1, the description will be resumed. The exhaust passage 10 is branched into exhaust passages 10a and 10b, and the turbine 4b of the turbocharger 4 is disposed in the exhaust passage 10a. The turbine 5b of the turbocharger 5 is disposed in the exhaust passage 10b. Is arranged. 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 Rukoto.

  The turbocharger 4 is configured as a low-capacity low-speed supercharger with a large supercharging capacity in the low and medium speed range, and the turbocharger 5 is a large-capacity high speed with a large supercharging capacity in the medium and high speed range It is configured as a type supercharger. That is, the turbocharger 4 corresponds to a so-called primary turbocharger, and the turbocharger 5 corresponds to a so-called secondary turbocharger. The turbocharger 4 corresponds to the first supercharger in the present invention, and the turbocharger 5 corresponds to the second supercharger in the present invention. As described above, FIG. 1 shows an example in which a control device for an internal combustion engine is applied to a parallel twin turbo system (parallel sequential turbo system).

  Further, an exhaust switching valve 15 is provided in the exhaust passage 10b. The exhaust switching valve 15 is controlled in opening degree by a control signal S15 supplied from the ECU 50 via an actuator (not shown), and adjusts the flow rate of the exhaust gas passing through the exhaust passage 10b. For example, by opening and closing the exhaust gas switching valve 15, it is possible to switch the flow / blocking of the exhaust gas in the exhaust passage 10b.

  One end of the exhaust bypass passage 16 is connected to the exhaust passage 10b between the upstream of the inlet of the turbine 5b and the exhaust switching valve 15, and the other end is connected to the exhaust passage 10 downstream of the turbines 4b and 5b. . The exhaust bypass passage 16 bypasses the turbines 4b and 5b and guides the exhaust gas passing through the exhaust passage 10 to the downstream side of the turbines 4b and 5b. An exhaust bypass valve 17 is provided in the exhaust bypass passage 16. The exhaust bypass valve 17 is opened when the pressure in the passage exceeds a predetermined value.

  The ECU 50 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). ECU50 acquires the output of the various sensors provided in the vehicle, and controls each component of the vehicle based on this. In the present embodiment, the ECU 50 mainly controls the fuel injection valve 8b in the engine 8 based on the detection signal S21 supplied from the supercharging pressure sensor 21 when switching from the single turbo mode to the twin turbo mode. Then, the control signal S8 is supplied to control the fuel injection. Specifically, the ECU 50 performs control for performing the switching, and performs post-injection in accordance with this control. Therefore, the ECU 50 functions as a post injection control unit and an exhaust gas switching valve control unit in the present invention. The ECU 50 also controls other components in the vehicle, but a description of portions that are not particularly related to the present embodiment is omitted.

  Here, a method of switching the mode (single turbo mode / twin turbo mode) for operating the turbochargers 4 and 5 will be briefly described. The ECU 50 performs control to switch between a single turbo mode (without running), a single turbo mode (with running), and a twin turbo mode. Specifically, the ECU 50 performs opening / closing control on the intake switching valve 6, the intake bypass valve 32, the exhaust switching valve 15, and the exhaust bypass valve 17 based on the engine speed, the engine torque, and the like. Switch to one of three modes.

  The “single turbo mode (without running)” is a mode that is performed in the low and medium speed ranges. In this mode, the ECU 50 performs control such that all of the intake switching valve 6, the exhaust switching valve 15, and the exhaust bypass valve 17 are closed. As a result, the intake and exhaust gases are supplied only to the turbocharger 4 out of the turbochargers 4 and 5, and only the turbocharger 4 operates.

  The “single turbo mode (with running)” is a mode that is performed in the middle speed range. Here, the running is equivalent to an operating state in which the turbocharger 5 is rotated in advance in order to suppress a step difference in the supercharging pressure that occurs when switching from the single turbo mode to the twin turbo mode. In this mode, the ECU 50 performs control to slightly open the exhaust switching valve 15 when switching from the single turbo mode to the twin turbo mode, that is, control to slightly open. As a result, a relatively small flow rate of exhaust gas is supplied to the turbocharger 5, and the turbocharger 5 can be gradually operated (ie, run up). In the present specification, the single turbo mode (without running) and the single turbo mode (with running) are basically described as “single turbo mode”.

  The “twin turbo mode” is a mode performed in a medium to high speed range. In this mode, the ECU 50 performs control to open the intake switching valve 6 and the exhaust switching valve 15. Thereby, intake and exhaust gas are supplied to both turbochargers 4 and 5, and both turbochargers 4 and 5 operate.

[Control method in this embodiment]
Next, the control method performed by the ECU 50 in the present embodiment will be specifically described.

  At the time of switching from the single turbo mode to the twin turbo mode as described above, the flow rate is also distributed to the turbocharger 5, and accordingly, the exhaust flow rate to the turbine 4b of the turbocharger 4 (in other words, the exhaust pressure) ) Decreases, the rotational speed of the turbocharger 4 tends to decrease. Therefore, at the time of the switching, the supercharging pressure is reduced, and a torque step (torque shock) may occur.

  Therefore, in the present embodiment, control is performed to appropriately suppress a torque step that may occur when switching from the single turbo mode to the twin turbo mode. Specifically, the ECU 50 performs post injection according to the control for performing the switching. By doing so, the exhaust temperature rises (that is, the exhaust energy increases) by post injection, and the expansion rate can be improved. Therefore, it is possible to recover the decrease in the rotational speed of the turbine 4b of the turbocharger 4 at the time of switching, and it is possible to suppress the decrease in the supercharging pressure. Therefore, it is possible to appropriately suppress the torque step.

  More specifically, in the present embodiment, as described above, in the period in which the control for slightly opening the exhaust gas switching valve 15 is performed in order to pre-rotate (running up) the turbocharger 5 (hereinafter, this period is referred to as the period). The ECU 50 performs post-injection as the exhaust gas switching valve 15 is opened. By doing so, it is possible to appropriately suppress a decrease in supercharging pressure during the run-up period.

  Further, the ECU 50 performs fuel injection when performing post-injection during a period in which the intake switching valve 6 is controlled to be gradually opened after the end of the above-described running period (hereinafter, this period is referred to as a “transition period”). The amount (hereinafter referred to as “post injection amount”) is also gradually increased. By doing so, it is possible to smoothly transition from the single turbo mode to the twin turbo mode.

  Further, the ECU 50 continues such post-injection until the supercharging pressure reaches the target supercharging pressure after the exhaust switching valve 15 is fully opened after the above-described transition period ends. By doing so, it is possible to suppress a rapid decrease in the supercharging pressure after the end of the transition period. The target supercharging pressure is obtained from an arithmetic expression or a map defined based on the driving state of the vehicle (engine speed, fuel injection amount, etc.).

  The post injection described above corresponds to fuel injection performed after main combustion (after main injection). Basically, the post-injection is not a fuel injection performed for the purpose of burning the fuel in the cylinder 8c, but corresponds to a fuel injection performed to send fuel to the exhaust passage 10, for example. The post injection amount used at the time of switching as described above is, for example, the number of revolutions of the turbochargers 4 and 5, the exhaust pressure, the opening of the exhaust switching valve 15, the air amount, and the fuel injection amount (at the time of main injection) It is obtained from a predetermined arithmetic expression or map based on the injection amount).

  Next, with reference to FIG. 3, the control method in this embodiment is demonstrated concretely. FIG. 3 is a diagram illustrating an example of a state at the time of switching from the single turbo mode to the twin turbo mode. Specifically, in order from the top, the post injection amount, the supercharging pressure, the rotational speed of the turbocharger 4, the rotational speed of the turbocharger 5, the opening degree of the exhaust gas switching valve 15, and the opening degree of the intake air switching valve 6 , Shows the change over time. In addition, in the supercharging pressure, the number of revolutions of the turbocharger 4 and the number of revolutions of the turbocharger 5, the graphs 71, 72, and 73 shown by broken lines indicate the cases where post injection is performed, Graphs 81, 82, and 83 indicated by solid lines indicate the cases where post injection is not performed. The period T1 corresponds to the period set in the single turbo mode, the period T2 corresponds to the run-up period, the period T3 corresponds to the transition period, and the period T4 corresponds to the period set in the twin turbo mode. To do.

  Before time t11, the single turbo mode is set, and control for switching from the single turbo mode to the twin turbo mode is started from time t11. Specifically, in the period from time t11 to time t12 (advancing period T2), as indicated by an arrow A1, the exhaust gas switching valve 15 is slightly opened in order to perform preliminary rotation (advancing) of the turbocharger 5. Control is performed. In this run-up period T2, the ECU 50 performs post injection as the exhaust gas switching valve 15 is opened, as indicated by an arrow A2. Thereby, it turns out that the fall of the rotation speed of the turbocharger 4 is suppressed compared with the case where post injection is not performed. Therefore, as shown by the arrow A3, it can be seen that the decrease in the supercharging pressure during the run-up period is suppressed as compared with the case where the post injection is not performed.

  Next, after time t12 (that is, after the end of the run-up period T2), as shown by the arrow B1, the intake switching valve 6 is controlled to be gradually opened. In the period from time t12 to time t13 (transition period T3), specifically, in the period until the exhaust switching valve 15 and the like are fully opened, the ECU 50 gradually increases the post injection amount as indicated by the arrow B2. increase. As a result, the transition from the single turbo mode to the twin turbo mode is smoothly performed. Specifically, it can be seen that the rotational speed of the turbocharger 5 is rapidly increased as compared with the case where post injection is not performed.

  Next, at time t13 (that is, after the end of the transition period T3), as shown by the arrow C1, the exhaust gas switching valve 15 is fully opened. After this time t13, the ECU 50 continues the post-injection until the supercharging pressure reaches the target supercharging pressure as indicated by an arrow C2. Thereby, as shown by arrow C3, it turns out that the rapid fall of a supercharging pressure is suppressed after completion | finish of a transition period. Thereafter, at time t14 when the supercharging pressure reaches the target supercharging pressure, the ECU 50 ends the post injection.

[Modification]
The present invention is not limited to application to a system in which two turbochargers 4 and 5 are arranged in parallel in the intake passage 3 and the exhaust passage 10. The present invention can be similarly applied to a system (series 2 turbo system) in which two turbochargers (a high-pressure turbocharger and a low-pressure turbocharger) are arranged in series in an intake passage and an exhaust passage. it can. That is, even in a system in which two turbochargers are arranged in series, post-injection can be performed in accordance with the control for performing the switching when switching the mode in which the turbocharger is operated. This also makes it possible to appropriately suppress a torque step that can occur at the time of switching.

  Further, in the above, an example in which post injection is performed in order to suppress a torque step that may occur at the time of switching from the single turbo mode to the twin turbo mode is shown, but in place of or in addition to post injection, At the time of switching, at least one of after injection and timing retard may be executed according to the switching. Thereby, the fall of the supercharging pressure at the time of the said switching can be suppressed effectively, and it becomes possible to suppress a torque level | step difference effectively. Note that after-injection basically corresponds to fuel injection that is performed in order to burn unburned fuel by injecting minute fuel after main injection. Further, the timing retard corresponds to control for delaying the fuel injection timing until just before the top dead center.

1 is a schematic configuration diagram of a vehicle to which an internal combustion engine control device according to an embodiment is applied. The schematic block diagram of an engine is shown. The figure for demonstrating the control method in this embodiment concretely is shown.

Explanation of symbols

3 Intake passage 4, 5 Turbocharger 4a, 5a Compressor 4b, 5b Turbine 6 Intake switching valve 8 Engine (internal combustion engine)
8b Fuel injection valve 8c Cylinder 10, 10a, 10b Exhaust passage 15 Exhaust switching valve 16 Exhaust bypass passage 17 Exhaust bypass valve 21 Boost pressure sensor 31 Intake bypass passage 32 Intake bypass valve 50 ECU

Claims (5)

A control device for an internal combustion engine comprising a first supercharger and a second supercharger,
When switching from the mode for operating the first supercharger to the mode for operating the first supercharger and the second supercharger, post-injection according to the control for performing the switching A control device for an internal combustion engine, comprising post-injection control means for performing An exhaust gas switching valve control means for performing control for slightly opening the exhaust gas switching valve in order to perform preliminary rotation of the second supercharger at the time of the switching;
2. The internal combustion engine according to claim 1, wherein the post-injection control unit performs the post-injection according to an opening degree of the exhaust gas switching valve during execution of control for slightly opening the exhaust gas switching valve by the exhaust gas switching valve control unit. Engine control device.   The post-injection control unit is configured to perform fuel injection at the time of performing the post-injection during the execution of the control for gradually opening the intake switching valve after the exhaust switching valve control unit slightly opens the exhaust switching valve. The control device for an internal combustion engine according to claim 2, wherein the amount is increased.   The control apparatus for an internal combustion engine according to claim 2 or 3, wherein the post-injection control means continues the post-injection until the supercharging pressure reaches a target supercharging pressure after the exhaust gas switching valve is fully opened. .   The control device for an internal combustion engine according to any one of claims 1 to 4, wherein the first supercharger and the second supercharger are arranged in parallel to an intake passage and an exhaust passage.

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