JP2018053841A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of exhaust by suppressing generation of soot by reducing fuel injection from a stage number near an ignition timing among the divided fuel injections, in reducing a fuel injection amount from a fuel injection device in accordance with a canister purge.SOLUTION: In an engine control device for controlling an engine provided with a fuel injection device, a fuel injection amount is reduced from injection near at least an ignition timing in accordance with a request reduction amount, when the reduction of the fuel injection amount injected from the fuel injection device, is requested in executing multi-stage injection.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a control device for an internal combustion engine.

  Some engines perform multi-stage injection to suppress harmful substances contained in exhaust gas by using a fuel injection device for in-cylinder injection. In addition, there is an engine equipped with a canister purge system that processes fuel evaporated from a fuel tank by introducing it into a combustion chamber through an intake pipe and burning it. When the canister purge is performed, it is necessary to reduce the fuel injected from the fuel injection device so that the fuel in the combustion chamber does not become excessive. As a method for making both the multistage injection and the canister purge compatible, Patent Document 1 discloses an engine control method for reducing the fuel injection amount of at least the first stage of the multistage injection in accordance with the amount of fuel sucked by the purge.

WO2015 / 162797

  By the way, in the engine which performs multistage injection, the timing which finishes fuel injection will be late | slow compared with the engine which does not perform multistage injection, and will cause a generation of soot. It is not possible to cope with this problem only by reducing the fuel injection amount of at least the first stage injection.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for an internal combustion engine that reduces soot while satisfying both the multistage injection and the demand for reducing the fuel injection amount.

  In order to solve the above-described problems, in the present invention, in an engine control device including a fuel injection device that injects fuel into a combustion chamber of an engine, fuel is injected from the fuel injection device when performing multistage injection in which fuel is divided and injected. When the fuel injection amount reduction request is generated, the fuel injection amount is preferentially reduced from the injection close to the ignition timing in accordance with the reduction amount request.

  According to the present invention, when the fuel injection amount from the fuel injection device is decreased in accordance with the canister purge, the generation of soot is suppressed by reducing the fuel injection from the number of stages close to the ignition timing among the divided fuel injections. And exhaust deterioration can be prevented. Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.

1 is a system configuration diagram of an automobile engine system according to a first embodiment of the present invention. The system block diagram which shows the structure of ECU1 by 1st Example of this invention. The flowchart which shows the fuel loss correction | amendment at the time of the multistage injection by 1st Example of this invention. The flowchart which shows the method of reducing the injection of the most retarded angle in the fuel loss correction | amendment at the time of the multistage injection by 1st Example of this invention. The schematic diagram which shows the change of the pulse shape in the case of reducing the injection of the most retarded angle in the fuel reduction correction at the time of multistage injection by 1st Example of this invention. 10 is a flowchart showing another method of changing the divided pulse width by reducing the most retarded injection in the fuel reduction correction at the time of multi-stage injection according to the second embodiment of the present invention. The schematic diagram which shows the change of the pulse shape at the time of reducing the injection of the most retarded angle in the fuel reduction correction | amendment at the time of the multistage injection by 2nd Example of this invention, and changing another division | segmentation pulse width. The flowchart which shows the fuel loss correction method at the time of weak stratified lean combustion and multistage injection by 3rd Example of this invention. The schematic diagram which shows the change of the pulse shape in the case of performing fuel reduction correction at the time of weak stratified lean combustion and multistage injection by the 3rd example of the present invention. The flowchart which shows the transfer method at the time of weak stratified lean combustion at the time of fuel reduction correction | amendment execution at the time of the multistage injection by 4th Example of this invention. The schematic diagram which shows the change of the pulse shape at the time of shifting to the time of weak stratified lean combustion at the time of fuel reduction correction | amendment at the time of the multistage injection by 4th Example of this invention.

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

FIG. 1 is a system configuration diagram of an engine in the present embodiment.
The engine 100 is a spark ignition internal combustion engine. A mass flow meter 3 for measuring the intake air amount of the engine, an intake pipe pressure sensor 4 for measuring the intake pipe pressure, and an intake pipe temperature sensor 5 for measuring the temperature of the intake air as one aspect of the intake air temperature detector. And a throttle 6 for adjusting the intake pipe pressure are appropriately provided at each position of the intake pipe 7. Further, the engine 100 is provided with a fuel injection device 8 for injecting fuel into the combustion chamber 13 and a spark plug 9 for supplying ignition energy at appropriate positions of the engine 100. Further, a three-way catalyst 16 for purifying the exhaust and an air-fuel ratio sensor 15 that is an aspect of the air-fuel ratio detector and detects the air-fuel ratio of the exhaust on the upstream side of the three-way catalyst 16 are appropriately disposed in each of the exhaust pipes 14. Provided in position. The air-fuel ratio sensor 15 may be an oxygen concentration sensor.

  The crankshaft 11 is provided with a crank angle sensor 12 for detecting the angle and rotational speed of the crankshaft 11 and the moving speed of the piston 10. There is also a fuel tank 19 for supplying fuel to the fuel injection device 8. A pipe is connected from the fuel tank 19 to a charcoal canister 18 for adsorbing fuel vapor in the fuel tank 19. Further, a canister purge valve 17 is connected between a pipe for introducing fuel vapor from the charcoal canister 18 to the intake pipe 7 and the intake pipe 7.

  Detection signal Ss15 obtained from air-fuel ratio sensor 15, detection signal Ss12 obtained from crank angle sensor 12, detection signal Ss3 obtained from mass flow meter 3, detection signal Ss4 obtained from intake pipe temperature sensor 4, and intake pipe pressure sensor 3 The detection signal Ss3 obtained from is sent to the engine control unit (hereinafter referred to as ECU) 1. A signal Ss2 obtained from the accelerator opening sensor 2 that detects the amount of depression of the accelerator pedal, that is, the accelerator opening, is sent to the ECU 1.

  The ECU 1 calculates the required torque based on the output signal Ss2 of the accelerator opening sensor 2 and various sensor signals. That is, the accelerator opening sensor 2 is used as a required torque detection sensor that detects a required torque for the engine 100. The ECU 1 calculates the angle and rotational speed of the crankshaft 11 and the moving speed of the piston 10 based on the output signal Ss12 of the crank angle sensor 12. The ECU 1 optimizes the main operating amount of the engine 100 such as the opening degree of the throttle 6, the injection pulse period of the fuel injection device 8, and the ignition timing of the spark plug 9 based on the operating state of the engine 100 obtained from the outputs of the various sensors. Calculate to

  The fuel injection pulse period calculated by the ECU 1 is converted into a fuel injector valve opening pulse signal Ds8 and sent to the fuel injector 8. A spark plug drive signal Ds9 is sent to the spark plug 9 so as to be ignited at the ignition timing calculated by the ECU 1. The throttle opening calculated by the ECU 1 is sent to the throttle 5 as a throttle drive signal Ds6.

  Fuel is injected from the fuel injection device 8 through a fuel pump (not shown) from the fuel tank 19 to the air flowing into the combustion chamber 13 from the intake pipe 7 through the intake valve, thereby forming an air-fuel mixture. The air-fuel mixture is burned by a spark generated from the spark plug 9 at a predetermined ignition timing, and the piston 10 is pushed down by the combustion pressure to become a driving force of the engine 100. The exhaust gas after combustion is sent to the three-way catalyst 16 through the exhaust valve and the exhaust pipe 14, and after the NOx, CO, and HC components are purified in the three-way catalyst 16, it is discharged.

  When the pressure in the charcoal canister 18 for storing the evaporated fuel in the fuel tank 19 increases, the ECU 1 transmits an opening command to the canister purge valve 17, and the evaporated fuel flows into the intake pipe 7 by opening the canister purge valve 17. And then sent to the combustion chamber 13.

  FIG. 2 is a system block diagram showing the configuration of the ECU 1 according to this embodiment. The output signals of the accelerator opening sensor 2, the mass flow meter 3, the intake pipe pressure sensor 4, the intake pipe temperature sensor 5, the crank angle sensor 12, and the air-fuel ratio sensor 15 are input to the input circuit 30a of the ECU 1. However, the input signal is not limited to these. The input signal from each input sensor is sent to the input port in the input / output port 30b. The value of the input signal sent to the input / output port 30b is stored in the random access memory RAM 30c and is processed by the CPU 30e. At this time, a signal composed of an analog signal among input signals sent to the input circuit 30a is converted into a digital signal by an A / D converter provided in the input circuit 30a.

  A control program describing the contents of the arithmetic processing is written in advance in the read-only memory ROM 30d. A value indicating the operation amount of each actuator calculated according to the control program is stored in the RAM 30c, then sent to the output port of the input / output port 30b, and sent to each actuator via each drive circuit. In this embodiment, there are a throttle drive circuit 30f, a fuel injection device drive circuit 30g, an ignition output circuit 30h, a variable valve mechanism drive circuit 30i, and a canister purge valve drive circuit 30j as drive circuits.

  Each drive circuit controls the throttle 6, the fuel injection device 8, the spark plug 9, and the canister purge valve 17. Although the ECU 1 of this embodiment includes the drive circuit in the ECU 1, the present invention is not limited to this, and any or all of the drive circuits may be provided outside the ECU 1.

  FIG. 3 is a flowchart showing the operation of the control device in this embodiment. First, in step S301, a basic fuel injection pulse width TPBASE before a reduction request for injection from the fuel injection device is calculated. Next, in step S302, the basic multi-stage injection number NDIVINJ0 before requesting a reduction is calculated. Next, in step S303, it is determined whether there is a request for reducing the fuel injection amount. If there is a weight reduction request, the process proceeds to step S304. When there is no weight reduction request, the process proceeds to step S306. In step S304, a fuel injection pulse width TPDEC corresponding to the required amount of reduction is calculated. The fuel injection amount is reduced in step S305 based on the basic fuel injection pulse width TPBASE calculated in step S301 and the reduction equivalent pulse width TPDEC calculated in step S304. In step S306, a pulse width is input to the fuel injection device to perform fuel injection.

FIG. 4 is a flowchart for explaining details of the flowchart shown in FIG. Steps S401 to S404 are the same as steps S301 to S304 in FIG. In step S405, the most retarded basic pulse width TPDIVN0 is calculated. The specific calculation of the pulse width may be performed by an appropriate technique in addition to a known technique.
In step S406, the reduction equivalent pulse width TPDEC is compared with the most retarded stage pulse width TPDIVO. If TPDEC is smaller than TPDIVO, the process proceeds to step S407. If TPDEC is greater than TPDIVO, the process proceeds to step S408. In step S407, the most retarded stage pulse width TPDIVN is calculated. The difference obtained by subtracting TPDEC from the basic most retarded stage pulse width TPDIVN0 is defined as TPDIVN. After calculating TPDIVN, the process proceeds to step S409. In step S408, the number of multistage injections NDIVINJF, which is the number of multistage injections, is calculated. The number obtained by subtracting 1 from the basic multi-stage injection number NDIVINJ0 calculated in step S402 is defined as NDIVINJF. Finally, in step S409, fuel injection is executed based on the pulse width calculated in steps S401 to S408.

  FIG. 5 is a schematic diagram showing changes in the number of multistage injections and pulse widths due to the flow operation shown in FIG. As an example, a case where a canister purge is executed and a reduction request depending on the purge flow rate is made is shown. In normal times when there is no request for weight reduction, the number of multistage injections is three times. However, as shown in FIG. Alternatively, the third pulse width is decreased as shown in FIG. Note that FIG. 5 shows three divisions as an example, but the actual number of divisions is not limited to three, and may be determined by a known technique and an appropriate technique.

  As described above, the engine control apparatus (ECU 1) of the present embodiment includes the fuel injection device 8 that injects fuel into the combustion chamber 13 of the engine 100, and the fuel injection device 8 at the time of performing multistage injection that divides and injects the fuel. When a request to reduce the fuel injection amount injected from the engine is generated, the fuel injection device 8 is controlled so that the fuel injection amount is preferentially reduced from the injection close to the ignition timing of the spark plug 9 in accordance with the reduction request amount.

  At this time, as shown in FIG. 5 a), when the engine control unit (ECU 1) generates a fuel injection amount reduction request during the multistage injection execution, the number of divisions of the multistage injection is set to the spark plug 9 in accordance with the reduction amount request amount. It is better to preferentially reduce the injection close to the ignition timing. Alternatively, as shown in FIG. 5 b), when the engine control unit (ECU 1) reduces the fuel injection amount from the injection close to the ignition timing of the spark plug 9, the fuel injection pulse width may be shortened.

  In the present embodiment, it is possible to achieve both the reduction request and the multistage injection while suppressing the generation of soot by reducing the pulse at least from the most retarded angle based on the request for the reduction of the fuel injection amount when executing the multistage injection. It becomes.

  FIG. 6 is a flowchart showing another embodiment of the flow shown in FIG. Steps S601 to S607 are the same as steps S401 to S407 in FIG. The most retarded stage pulse width TPDIVN decreased in step S608 is compared with the pulse width TPMIN corresponding to the fuel injection amount lower limit value that can be controlled by the fuel injection device. If TPDIVN is greater than TPMIN, the process proceeds to step S611. If TPDIVN is smaller than TPMIN, the process proceeds to step S609. Since step S609 is the same as step S408, description thereof is omitted. In step S610, TPDIVN is added to the remaining pulse width. In step S611, fuel injection is executed based on the number of multistage injections and the pulse width calculated in steps S601 to S610.

  FIG. 7 is a schematic diagram showing changes in the number of multistage injections and pulse widths due to the flow operation shown in FIG. If the difference between the pulse width of the most retarded stage and the pulse width corresponding to the reduction amount is smaller than the minimum value TPMMIN, the pulse width of the most retarded stage is reduced and the difference is distributed to other pulse widths.

  As described above, the engine control apparatus (ECU 1) of the present embodiment has a fuel amount obtained by subtracting the reduction amount from the amount of fuel that is reduced when the number of divisions of multistage injection is reduced, as shown in FIG. If it is smaller than the minimum value that can be controlled by the control, control is performed to increase the pulse width of the other divided injections. At this time, the injection pulse of the injection close to the ignition timing of the spark plug 9 is controlled to be short. Further, as shown in FIG. 7, the engine control unit (ECU 1) adds the fuel amount obtained by subtracting the reduction amount from the fuel amount that is reduced when the number of divisions of multi-stage injection is reduced to the other divided pulse widths. .

  In the embodiment of the present invention, the fuel injection amount reduction request amount is determined, for example, based on the purge-derived fuel amount at the time of canister purge execution. Alternatively, it is determined based on the fuel reduction request when the air-fuel ratio feedback control is executed. Alternatively, it is determined based on the fuel cut request amount during deceleration. Alternatively, it is determined based on the purge amount of the crankcase volatile fuel. It is desirable that the fuel injection amount reduction request amount is determined by combining any of the above factors or these factors.

  In this embodiment, the difference between the pulse width of the most retarded stage and the pulse width corresponding to the reduction request is added to the other pulse widths, and at least the injection of the most retarded stage is deleted, so that the fuel injection device can be controlled. By reducing the fuel injection amount and preventing excessive reduction without falling below the lower limit value, it becomes possible to prevent misfire and generation of harmful substances.

  FIG. 8 is a flowchart showing another embodiment of the flow shown in FIGS. Since steps S801 to S804 are the same as steps S601 to S604, the description thereof is omitted. In step S805, it is determined whether the combustion mode is weakly stratified lean combustion. Weakly stratified lean combustion is a stratified lean combustion in which the air-fuel ratio in the combustion chamber 13 is larger than the stoichiometric ratio, that is, a homogeneous lean combustion state is set, and in addition, fuel for ignition is injected just before ignition in the latter half of the compression stroke. It is a combustion mode combining states. If the combustion mode is weakly stratified lean combustion, the process proceeds to step S806. If the combustion mode is not weakly stratified lean combustion, the process proceeds to step S808. In step S806, the basic fuel injection pulse width TPDIVNM10 immediately before the most retarded stage is calculated. In step S807, processing is performed with TPDIVN0 in steps S607 to S610 as TPDIVNM10 and TPDIVN as TPDIVNM1. Since steps S808 to S810 perform the same processing as steps S605 to S611, description thereof is omitted.

  As described above, the engine control apparatus (ECU 1) of the present embodiment, as shown in FIG. 7, is a case where the combustion chamber 13 is burned by weakly stratified lean combustion combining homogeneous lean combustion and stratified lean combustion, and when multistage injection is performed. When a request for reducing the fuel injection amount injected from the fuel injection device 8 is generated, the fuel injection closest to the ignition timing of the spark plug 9 remains, and the fuel injection device 8 is set so as to reduce the fuel amount from the previous injection. Control.

  FIG. 9 is a schematic diagram showing a change in the number of multistage injections by the flow operation shown in FIG. In the case of weak stratified lean combustion, the fuel injection at the most retarded stage is necessary for ignition, so the quantity is reduced from at least the previous stage.

  In this embodiment, when a request for reduction of fuel injection is made during weak stratified lean combustion, the most retarded stage injection is left and the previous injection pulse is reduced, so that the combustion stability of lean combustion is not impaired. In addition, it is possible to prevent misfires and generation of harmful substances by making the multistage injection and the weight reduction request compatible.

  FIG. 10 is a flow chart showing another embodiment of the flow shown in FIGS. In step S1001, it is determined whether fuel reduction correction is being performed. Here, the fuel content reduction correction is performed according to the implementation contents shown in the first to third embodiments. If the weight reduction correction is being performed, the process proceeds to step S1002. If the weight reduction correction has not been executed, the process proceeds to step S1006. In step S1002, it is determined whether there is a request for the combustion mode to shift from stoichiometric ratio to weakly stratified lean combustion. If there is a migration request, the process proceeds to step S1003. If there is no migration request, the process proceeds to step S1006.

  In step S1003, the number of multistage injections NDIVINJL at the time of weak stratification lean combustion is calculated. 1 is added to the number of multistage injections at the stoichiometric ratio, and the process proceeds to step S1004. In step S1004, the fuel injection stage injection timing for the amount added in S1003 is set in the latter half of the compression stroke. In step S1005, the same width as the pulse width increased in S1003 and S1004 is decreased from the other divided pulses. In step S1006, the actual combustion mode is changed from stoichiometric ratio to weakly stratified lean combustion. In step S1007, fuel injection is performed based on the fuel injection pulse width and fuel injection timing calculated in steps S1001 to S1006.

  FIG. 11 is a schematic diagram showing a change in the number of multistage injections by the flow operation shown in FIG. When the stoichiometric ratio combustion state and the reduction correction are performed, the fuel injection pulse at the most retarded stage is cut off. When the combustion mode shifts from this state to weakly stratified lean combustion, it is necessary to inject fuel in the latter half of the compression stroke in order to maintain ignitability. Therefore, the number of multistages is increased. However, if the pulse width is simply increased, the fuel amount becomes excessive, so the same amount of pulse width is reduced from the other pulses.

  As described above, the engine control device (ECU 1) of the present embodiment injects from the fuel injection device 8 when the combustion chamber is burned by the stoichiometric combustion as shown in FIG. The fuel injection device 8 is controlled so as to increase the number of multistage injections when a request to change the combustion mode to a weakly stratified state occurs in a state where the fuel injection amount is reduced in response to a request to reduce the fuel injection amount. . In addition, when increasing the number of multistage injections in this way, it is desirable that the injection timing of the injection to be increased is the latter half of the compression stroke.

In this embodiment, even when a change in combustion mode occurs during the reduction correction, it is possible to realize weak stratified lean combustion while maintaining an appropriate fuel amount, and to prevent deterioration of fuel consumption and exhaust. Become.
In addition, this invention is not limited to each above-mentioned Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.
For example, the fuel injection amount reduction request in each embodiment is caused by a canister purge, an air-fuel ratio feedback by the output of an air-fuel ratio sensor or an oxygen sensor, or a torque reduction request during deceleration, etc. Various selections are possible.

DESCRIPTION OF SYMBOLS 1 ... ECU, 2 ... Accelerator opening sensor, 3 ... Mass flow meter, 4 ... Intake pipe pressure sensor, 5 ... Intake pipe temperature sensor, 6 ... Throttle valve, 7 ... Intake pipe, 8 ... Fuel injection device, 9 ... Ignition Plug 10, piston 10, crankshaft 12, crank angle sensor 13 combustion chamber 14 exhaust pipe 15 air / fuel ratio sensor 16 three-way catalyst 17 canister purge valve 18 charcoal canister 19 ... Fuel tank

Claims (9)

In an engine control device including a fuel injection device that injects fuel into a combustion chamber of an engine,
When a request to reduce the fuel injection amount injected from the fuel injection device is generated during the execution of multistage injection in which fuel is divided and injected, the fuel injection amount is preferentially reduced from the injection close to the ignition timing in accordance with the reduction request amount. An engine control device characterized by that. The engine control device according to claim 1,
An engine control apparatus characterized by shortening a fuel injection pulse width when the fuel injection amount is reduced from injection close to ignition timing. The engine control device according to claim 1,
An engine control device characterized by preferentially reducing the number of divisions of multi-stage injection from injection close to the ignition timing in accordance with the reduction quantity requested when a fuel injection quantity reduction request is generated during execution of multi-stage injection. The engine control apparatus according to claim 3, wherein
When the fuel amount obtained by subtracting the reduction amount from the fuel amount that decreases when the number of divisions for multi-stage injection is smaller than the minimum value that can be controlled by the fuel injection device, it decreases when the number of divisions for multi-stage injection is reduced. An engine control apparatus characterized in that a fuel amount obtained by subtracting a reduction amount from a fuel amount is added to another divided pulse width. The engine control device according to claim 1,
The engine control apparatus characterized in that the increase in the fuel injection amount is set to an injection timing close to the ignition timing from the multistage injection before the increase is executed. 6. The engine control apparatus according to claim 1, wherein the fuel injection amount reduction request amount includes at least a purge-derived fuel amount at the time of canister purge execution, a fuel reduction request at the time of air-fuel ratio feedback control execution, and a fuel cut request at the time of deceleration. The engine control device is determined on the basis of the amount, the purge amount of the crankcase volatile fuel, or a combination thereof. The engine control device according to claim 1,
When the combustion chamber is combusted by weak stratified lean combustion combining homogeneous lean combustion and stratified lean combustion, and when a request to reduce the amount of fuel injected from the fuel injection device occurs during multistage injection, the ignition timing is An engine control device that controls the fuel injection device so as to reduce the amount of fuel from the previous injection, leaving the closest fuel injection. The engine control device according to claim 1,
Combustion mode when the combustion chamber is burned by stoichiometric combustion and when the multistage injection is performed and the fuel injection amount is reduced in response to a request for reduction of the fuel injection amount injected from the fuel injection device. When the request | requirement which changes to a weak stratification state generate | occur | produces, the said fuel-injection apparatus is controlled so that the frequency | count of multistage injection may be increased, The engine control apparatus characterized by the above-mentioned. The engine control apparatus according to claim 8, wherein
An engine control device characterized in that when the number of multistage injections is increased, the injection timing of the injection to be increased is in the latter half of the compression stroke.

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