JP2008095529A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress considerable deterioration of a combustion state caused by execution of a deposit burnoff treatment. <P>SOLUTION: A control device 40 for an internal combustion engine 10 executes a deposit burnoff treatment for burning off the accumulated deposit by switching an engine combustion state to a combustion state in which exhaust temperature becomes high when deposit of prescribed quantity or more is determined to be accumulated in an exhaust valve 25 of the internal combustion engine 10. When an engine operating region is divided into a plurality of regions on the basis of engine load and engine rotation speed, the control device 40 of the internal combustion engine 10 performs a deposit burnoff treatment on the condition that an engine operating state is in a second region adjacent to a first region where exhaust temperature becomes the temperature making a deposit burnt off, wherein in a second region, engine load and engine rotation speed are set to be lower than those of the first region by predetermined values, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control apparatus for an internal combustion engine that executes a deposit burnout process when it is determined that deposits have accumulated.

  In the internal combustion engine, the air-fuel mixture introduced into the combustion chamber is combusted in the combustion chamber, and the exhaust gas after combustion is discharged to the exhaust passage through the exhaust valve, so that the deposit contained in the exhaust adheres to the exhaust valve. Sometimes. On the other hand, such a deposit is burned down by high-temperature exhaust when an engine operation state with a high exhaust temperature, for example, a high-load operation state continues. However, when an engine operating state with a low exhaust temperature, for example, a low-load operating state continues, deposits accumulate on the exhaust valve. In this case, there is a risk of hindering the opening or closing operation of the exhaust valve.

Therefore, conventionally, in the control apparatus for an internal combustion engine described in Patent Document 1, for example, when it is determined that a predetermined amount or more of deposit has been accumulated in the exhaust system of the internal combustion engine, the exhaust temperature of the engine becomes a high temperature. Switch to the combustion state. In such a control device, when an operation state with a low exhaust temperature such that deposits accumulate on the exhaust valve is continued, the engine combustion state is switched to a combustion state in which the exhaust temperature becomes high, whereby the exhaust valve Deposits deposited on the surface will be burned away by high-temperature exhaust. For this reason, the accumulation of deposits in the exhaust valve is suppressed, and the valve opening failure or valve closing failure of the exhaust valve is suppressed.
JP 2006-112342 A

  By the way, in the control apparatus for an internal combustion engine as described above, deposit accumulation on the exhaust valve can surely be suppressed. However, for example, when the engine operating state is in a state where both the engine load and the engine speed are low, if the engine combustion state is changed to a combustion state where the exhaust temperature becomes a temperature at which the deposit burns out, the change amount Must be large. For this reason, there exists a possibility of causing the deterioration of the combustion state resulting from performing a deposit burning process.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a control device for an internal combustion engine that can suppress a significant deterioration in a combustion state caused by executing a deposit burnout process. is there.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
According to the first aspect of the present invention, when it is determined that a predetermined amount or more of deposit has accumulated in the exhaust system of the internal combustion engine, the engine combustion state is switched to a combustion state in which the exhaust temperature becomes high, and the deposited deposit is burned down. In a control apparatus for an internal combustion engine that executes deposit burnout processing, when the engine operation region is divided into a plurality of regions based on the engine load and the engine speed, the exhaust temperature is adjacent to the first region where the deposit is burnt out. The gist is that the deposit burnout process is executed on the condition that the engine operating state is in the second region where the engine load and the engine speed are set lower than the first region by a predetermined value. Yes.

  According to this configuration, even when it is determined that a predetermined amount or more of deposit has accumulated in the exhaust system of the internal combustion engine, the engine operating state is the first temperature at which the exhaust temperature becomes the temperature at which the deposit burns down. When the engine load and the engine speed are not in the second region adjacent to the region and lower than the first region by a predetermined value, execution of the deposit burnout process is suspended. For this reason, even when the engine operating state is in the low load and low speed range, the amount of change in the engine combustion state when executing the deposit burnout process is small compared to the configuration in which the deposit burnout process is executed. Thus, it is possible to suppress the significant deterioration of the combustion state caused by executing the deposit burnout process.

  According to a second aspect of the present invention, in the control device for an internal combustion engine according to the first aspect, the internal combustion engine is mounted as a drive source of a vehicle, and the deposit burn-out process has an engine operating state in the second region. And the gist is that it is executed on condition that the speed of the vehicle is equal to or higher than a predetermined speed.

  When the above-described deposit burnout process is executed, the engine combustion state is switched, so the engine output may be temporarily reduced due to misfire or the like. In this regard, according to the above configuration, the deposit burnout process is executed when the vehicle speed is equal to or higher than the predetermined speed. Therefore, even if the engine output temporarily decreases, the internal combustion engine can be By transmitting the driving force to the output shaft, it is possible to suppress the internal combustion engine from stalling.

  As a specific mode for switching the engine combustion state so that the exhaust temperature becomes high when the deposit burnout process is executed, the deposit burnout process is performed, for example, according to the invention according to claim 3. Can be adopted such that the combustion state is switched to a combustion state in which the exhaust gas temperature becomes high by retarding the ignition timing immediately before the deposit incineration process is executed.

  According to a fourth aspect of the present invention, in the control device for an internal combustion engine according to the third aspect, the deposit burnout process executes a process for retarding the ignition timing, and sets the opening of the throttle valve of the internal combustion engine. The gist is to switch the combustion state to a combustion state in which the exhaust gas temperature becomes high by changing the opening of the throttle valve just before the deposit burnout processing to the open side.

  According to this configuration, the output of the internal combustion engine accompanying the execution of the ignition timing retarding process by changing the opening of the throttle valve of the internal combustion engine to the open side of the opening in the low exhaust temperature operation state. It will be possible to make up for the decline.

Hereinafter, an embodiment of a control device for an internal combustion engine according to the present invention will be described with reference to FIG.
As shown in FIG. 1, a cylinder 12 (only one cylinder is shown in the figure) is formed in a cylinder block 11 of the internal combustion engine 10, and a piston 13 can reciprocate in each cylinder 12. Contained. The piston 13 is connected to the output shaft 15 via the connecting rod 14, and the output shaft 15 rotates as the piston 13 reciprocates. A combustion chamber 16 is formed above the piston 13 in the cylinder 12. An intake passage 17 and an exhaust passage 18 are connected to the combustion chamber 16. A throttle valve 20 that is driven to open and close by a motor 21 is provided in the intake passage 17, and the intake air amount is adjusted by the throttle valve 20. The intake air is introduced into the combustion chamber 16 as the intake valve 22 is opened. The fuel directly injected into the combustion chamber 16 from the fuel injection valve 23 is mixed with the intake air to become an air-fuel mixture, and the air-fuel mixture is combusted by ignition by the spark plug 24. Exhaust gas generated after the air-fuel mixture burns is discharged to the exhaust passage 18 as the exhaust valve 25 is opened.

  By the way, the internal combustion engine 10 is provided with various sensors for detecting the operating state of the internal combustion engine 10 and the like. For example, a rotation speed sensor 30 for detecting the rotation speed of the output shaft 15, that is, the engine rotation speed NE, is provided in the vicinity of the output shaft 15. Further, in the vicinity of the accelerator pedal 19, there is provided an accelerator opening sensor 31 for detecting the depression amount of the pedal 19, that is, the accelerator opening ACCP. Further, in the vicinity of the throttle valve 20, a throttle opening sensor 32 for detecting the opening of the valve 20, that is, the throttle opening TA is provided. Furthermore, a vehicle speed sensor 33 for detecting a vehicle speed SPD is provided in the vicinity of a wheel (not shown) of the vehicle on which the internal combustion engine 10 is mounted.

  Then, an output signal from the rotation speed sensor 30 or the like is input to the electronic control device 40. The electronic control unit 40 is a part that includes an arithmetic processing unit (CPU), a memory, and the like and performs overall control of the system of the internal combustion engine 10. That is, the electronic control unit 40 obtains various state quantities related to the operation of the internal combustion engine 10 based on the output signal from the rotational speed sensor 30 and the like, and drives the throttle valve 20 and the spark plug 24 to thereby open the throttle valve. Various engine controls such as degree control and ignition timing control are executed. Further, the electronic control unit 40 executes a deposit burnout process for burning out and removing deposits deposited on the exhaust system, particularly the exhaust valve 25.

  Next, with reference to FIG. 2 to FIG. 5, a processing procedure for executing this deposit burnout processing will be described. The series of processes shown in the flowcharts of FIGS. 2 and 3 are repeatedly executed by the electronic control unit 40 at a predetermined cycle. FIG. 5 is a timing chart showing the execution timing and the like of the deposit burnout process when each process shown in FIGS. 2 and 3 is executed.

  As shown in FIG. 2, in this deposit burnout process, first, the engine load KL, the engine speed NE, and the vehicle speed SPD are read (step S100). The engine load KL is calculated based on the accelerator opening ACCP.

  Then, following the process of step S100, it is determined whether or not the engine operating state is in the second region (step S101). Here, the determination process in step S101 will be specifically described with reference to FIG. In FIG. 4, when the engine operation region is divided into a plurality of regions based on the engine load and the engine speed, the first region where the exhaust temperature becomes the temperature at which the deposit burns out is adjacent to the first region. A second region in which the engine load and the engine speed are set lower than the first region by a predetermined value is shown. Further, in FIG. 4, the engine load and the engine speed limit are indicated by broken lines. In the engine operation region shown in FIG. 4, the region surrounded by the alternate long and short dash line among the regions adjacent to the first region, that is, the region S where the engine load is equal to or greater than the predetermined value is excluded from the second region. It has been. Therefore, in this region S, the deposit burn-out process is not executed even though the exhaust temperature is relatively high. This is because, in such a high-load operation region, priority is given to securing engine output rather than deposit removal. In the determination process of step S101 shown in FIG. 2, it is determined whether or not the engine operating state is in the second region shown in FIG. 4 based on the engine load KL and the engine speed NE. Incidentally, the relationship between the engine speed and the engine load shown in FIG. 4 is obtained in advance by experiments or the like and stored in the memory of the electronic control unit 40.

  If it is determined through the determination process in step S101 that the engine operating state is in the second region (step S101: YES, timing t0 in FIG. 5), whether or not the vehicle speed SPD is equal to or higher than the predetermined speed SPDK. Is determined (step S102). Here, the predetermined speed SPDK is such that the output shaft 15 of the internal combustion engine 10 is driven by the vehicle drive system even when the output of the internal combustion engine 10 is temporarily reduced by executing the deposit burning process. Thus, the internal combustion engine 10 is set to a value equal to or higher than the speed at which the internal combustion engine 10 does not stall. Incidentally, the predetermined speed SPDK is obtained in advance by experiments or the like and is stored in the memory of the electronic control unit 40.

  If it is determined through the determination processing in step S102 that the vehicle speed SPD is equal to or higher than the predetermined speed SPDK (step S102: YES), whether or not the low exhaust temperature timer value LC has reached the first predetermined time LCK. (Step S103, timings t0 to t1 in FIG. 5). Here, the low exhaust temperature timer value LC is counted up when the engine operating state is in a region other than the first region shown in FIG. 4, that is, in a region where deposits are accumulated on the exhaust valve 25. In addition, the first predetermined time LCK is an amount in which the amount of deposit accumulated on the exhaust valve 25 may cause a malfunction in the valve 25 after the engine operating state enters a region where such deposit accumulates. It is set to a time shorter than the time required to become. Thus, in the determination process of step S103, it is determined whether or not a predetermined amount or more of deposit has accumulated on the exhaust valve 25.

  If it is determined through the determination process in step S103 that the low exhaust temperature timer value LC has reached the first predetermined time LCK (step S103: YES, timing t1 in FIG. 5), the deposit burnout process is started. After that, it is determined whether or not the second predetermined time DMT has elapsed (step S104). The second predetermined time DMT is set to a time required from when the deposit incineration process is started until the deposit accumulated on the exhaust valve 25 is sufficiently burned out.

  If it is determined that the second predetermined time DMT has not elapsed after the deposit burnout process is started through the determination process in step S103 (step S104: NO), the deposit burnout process is executed (step S104: NO). Step S106: Timing t1 to t2 in FIG. In this deposit burnout process, the ignition timing of the spark plug 24 is retarded from the ignition timing immediately before the deposit burnout process is executed, and the opening of the throttle valve 20 is the opening just before the deposit burnout process is executed. Than the open side.

  By the way, when the ignition timing retarding process is executed in this way, the combustion state of the internal combustion engine 10 is a combustion state in which the air-fuel mixture is combusted even when the exhaust valve 25 is opened, that is, The combustion state is such that the air-fuel mixture is burned after. For this reason, when the retarding process of the ignition timing is executed, the exhaust temperature when the exhaust valve 25 is opened rises higher than the exhaust temperature before the ignition timing is retarded. Deposits deposited on the surface will be burned out. On the other hand, when such ignition timing retardation processing is executed, the engine output may decrease. In this regard, in the deposit burnout process, the ignition timing retard process is executed and the opening of the throttle valve 20 is changed to the open side, so that the intake air amount increases and the engine output increases. For this reason, a decrease in engine output accompanying the execution of the ignition timing retardation process is compensated.

  The deposit burnout process is executed when it is determined that the vehicle speed SPD is equal to or higher than the predetermined speed SPDK (step S102: YES). Therefore, even if the engine output temporarily decreases due to misfire or the like due to the execution of the ignition timing retarding process, the driving force is transmitted to the output shaft 15 of the internal combustion engine through the vehicle drive system. Therefore, it is possible to suppress the internal combustion engine from stalling.

After executing the processing of step S106, the electronic control unit 40 once ends this routine.
On the other hand, if it is determined that the second predetermined time DMT has elapsed after the deposit burnout process is started (step S104: YES, timing t2 in FIG. 5), the low exhaust temperature timer value LC is reset ( Step S105). Then, after executing the processing in step S105, the electronic control unit 40 once ends this routine.

  On the other hand, when it is determined that the engine operating state is not in the second region (step S101: NO), the electronic control unit 40 once ends this routine. Therefore, in this case, even if it is determined that the low exhaust temperature timer value LC has reached the first predetermined time LCK (step S103: YES), the execution of the deposit burnout process is suspended. (Timing t3 to t4 in FIG. 5). In other words, even when deposits of a predetermined amount or more are accumulated on the exhaust valve 25, the ignition timing and the opening of the throttle valve 20 must be greatly changed when the deposit burnout process is executed. For example, if the exhaust temperature does not rise to a temperature at which the deposit can be burned out, execution of the deposit burning process is suspended. For this reason, the amount of change in the engine combustion state when the deposit burnout process is executed is limited.

  When it is determined that the vehicle speed SPD is not equal to or higher than the predetermined speed SPDK (step S102: NO), and when it is determined that the low exhaust temperature timer value LC has not reached the first predetermined time LCK (step S103: NO) ), The electronic control unit 40 once ends this routine.

Next, a processing procedure for resetting the low exhaust temperature timer value LC will be described.
As shown in FIG. 3, in the low exhaust temperature timer reset process, first, the engine load KL and the engine speed NE are read (step S200). The engine load KL is calculated based on the accelerator opening ACCP.

  Then, following the process of step S200, it is determined whether or not the engine operating state is in the first region (step S201). Specifically, it is determined whether or not the engine operating state is in the first region shown in FIG. 4 based on the engine load KL and the engine speed NE.

  If it is determined through the determination process in step S201 that the engine operating state is in the first region (step S201: YES, timing t4 in FIG. 5), the engine operating state is shifted to the first region. Whether or not the third predetermined time HCK has elapsed is determined (step S202). The third predetermined time HCK is set to a time required until the deposit accumulated on the exhaust valve 25 is sufficiently burned after the engine operating state enters the first region.

  When it is determined through the determination process in step S202 that the third predetermined time HCK has elapsed since the engine operating state entered the first region (step S202: YES), the low exhaust temperature is set. The timer value LC is reset (step S203, timing t5 in FIG. 5). Even when the deposit burnout process is not executed, if the engine is operating in the first region where the deposit can be burnt down, the deposit deposited on the exhaust valve 25 is burned out. Therefore, in such a case, the execution of the deposit burnout process is suspended. Then, after executing the processing of step S203, the electronic control unit 40 once ends this routine.

  On the other hand, when it is determined that the engine operating state has not shifted to the first region (step S201: NO), and the third predetermined time HCK has elapsed since the engine operating state entered the first region. If it is determined that it is not (step S202: NO), the electronic control unit 40 once ends this routine.

As described above, according to the embodiment described above, the following effects can be obtained.
(1) According to the same configuration, even when it is determined that a deposit of a predetermined amount or more is accumulated on the exhaust valve 25 of the internal combustion engine 10, the engine operating state is the temperature at which the exhaust temperature is burned out of the deposit. When the engine load and the engine speed are not in the second area adjacent to the first area and lower than the first area by a predetermined value, execution of the deposit burnout process is suspended. For this reason, even when the engine operating state is in the low load and low speed range, the amount of change in the engine combustion state when executing the deposit burnout process is small compared to the configuration in which the deposit burnout process is executed. Thus, it is possible to suppress the significant deterioration of the combustion state caused by executing the deposit burnout process. Further, even when the engine operating state is the first region, that is, when the exhaust temperature is high and the deposit is burnt down even if the combustion state is not changed, the deposit burnout process is naturally not performed. It is possible to suitably suppress the change of the combustion state.

  (2) When the deposit burnout process as described above is executed, the engine combustion state is switched by retarding the ignition timing of the spark plug 24, so the engine output may be temporarily reduced due to misfire or the like. . In this regard, in the control device for the internal combustion engine 10, the deposit burnout process is executed when the vehicle speed is equal to or higher than the predetermined speed SPDK. Therefore, even if the engine output temporarily decreases, the internal combustion engine 10 By transmitting the driving force to the output shaft 15 of the engine 10, the internal combustion engine 10 is prevented from stalling.

  (3) In the control apparatus for the internal combustion engine 10, the ignition timing retarding process is executed during the deposit burnout process, and the opening of the throttle valve 20 is larger than the opening just before the deposit burnout process is executed. Changed to open side. For this reason, it becomes possible to compensate for the decrease in the output of the internal combustion engine 10 due to the execution of the ignition timing retarding process.

In addition, the said embodiment can be implemented with the following forms which changed this suitably.
The low exhaust temperature operation timer value LC described above has a correlation with the amount of deposit accumulated on the exhaust valve 25. For this reason, the execution time of the deposit burnout process, that is, the second predetermined time DMT is set so that the second predetermined time DMT becomes longer as the timer value LC is larger based on the low exhaust temperature operation timer value LC. May be variably set. According to such a configuration, it is possible to set the execution time of the deposit burnout process in a manner commensurate with the deposit accumulation amount of the exhaust valve 25.

  In the above-described embodiment, in the deposit burnout process, the ignition timing retarding process of the spark plug 24 and the opening degree changing process of the throttle valve 20 are executed together, but only the ignition timing retarding process is executed. You may make it do.

  In the above-described embodiment, the ignition timing of the spark plug 24 is retarded during the deposit burnout process. In addition to this, for example, by changing the air-fuel ratio to lean, and changing the fuel injection amount, etc. The exhaust temperature can also be raised.

In the deposit burnout processing routine, the determination as to whether or not the vehicle speed on which the internal combustion engine 10 is mounted is equal to or higher than a predetermined speed SPDK can be omitted.
In the execution of the deposit burnout process, only the deposit burnout process shown in FIG. 2 may be executed without executing the low exhaust temperature timer reset process shown in FIG. That is, deposit accumulation can be more reliably suppressed by resetting the low exhaust temperature timer value LC only when the deposit burn-out process is performed.

  Although the exhaust valve 25 is illustrated as an exhaust system in which deposits are accumulated, for example, the amount of deposits accumulated in the nozzle holes of the fuel injection valve 23 may be estimated, and the deposit burnout process may be executed based on the estimation result. Good.

The schematic diagram which shows the schematic structure about the control apparatus of the internal combustion engine concerning this invention. The flowchart which shows the process sequence about a deposit incineration process. The flowchart which shows the process sequence about the low exhaust temperature operation timer reset process. A map for judging the engine operating state based on the engine load and the engine speed. The timing chart which shows an example of a deposit burning process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Cylinder block, 12 ... Cylinder, 13 ... Piston, 14 ... Connecting rod, 15 ... Output shaft, 16 ... Combustion chamber, 17 ... Intake passage, 18 ... Exhaust passage, 19 ... Accelerator pedal, 20 ... Throttle valve, 21 ... motor, 22 ... intake valve, 23 ... fuel injection valve, 24 ... ignition plug, 25 ... exhaust valve, 30 ... rotational speed sensor, 31 ... accelerator opening sensor, 32 ... throttle opening sensor, 33 ... Vehicle speed sensor 34 ... Electronic control device.

Claims (4)

An internal combustion engine that performs a deposit burnout process that switches the engine combustion state to a combustion state in which the exhaust temperature becomes high when it is determined that a predetermined amount or more of deposit has accumulated in the exhaust system of the internal combustion engine and burns up the deposited deposit. In the control device,
When the engine operating region is divided into a plurality of regions based on the engine load and the engine rotational speed, the engine load and the engine rotational speed are adjacent to the first region where the exhaust temperature becomes a temperature at which the deposit burns out. The control apparatus for an internal combustion engine, wherein the deposit burnout process is executed on condition that the engine operating state is in a second region that is set lower by a predetermined value than each other. The control apparatus for an internal combustion engine according to claim 1,
The internal combustion engine is mounted as a vehicle drive source,
The control apparatus for an internal combustion engine, wherein the deposit burnout process is executed on condition that the engine operating state is in the second region and the vehicle speed is equal to or higher than a predetermined speed. The control device for an internal combustion engine according to claim 1 or 2,
The deposit burnout process is characterized in that the engine combustion state is switched to a combustion state in which the exhaust temperature becomes high by retarding the ignition timing of the internal combustion engine from the ignition timing immediately before the deposit burnout process is executed. A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 3,
In the deposit burnout process, the ignition timing retarding process is executed, and the opening degree of the throttle valve of the internal combustion engine is changed to the open side with respect to the opening degree of the throttle valve immediately before the deposit burnout process is executed. The control device for an internal combustion engine, wherein the combustion state is switched to a combustion state in which the exhaust temperature becomes high.

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