JP4911135B2 - Self-ignition combustion detector - Google Patents

Description

  The present invention relates to a self-ignition combustion detection device for a spark ignition internal combustion engine that is ignited by sparks of a spark plug.

In a spark-ignition internal combustion engine that is ignited by sparks of a spark plug, in a recent internal combustion engine designed to have a high compression ratio, self-ignition that burns by compression self-ignition at a timing earlier than when spark sparks by a spark plug. There is concern about the occurrence of combustion. In response to this concern, in Patent Document 1, it is determined that self-ignition combustion has occurred when the peak value of the in-cylinder pressure exceeds the reference value, and when the occurrence of self-ignition combustion is detected in this way, Suppression of self-ignition combustion is aimed at by control, such as prohibiting injection.
JP 2008-8235 A

  Here, as a result of various tests by the present inventors, once self-ignition combustion occurs, self-ignition combustion with large combustion energy occurs in the next combustion, and self-ignition combustion with larger combustion energy occurs in the next combustion. It was revealed that auto-ignition combustion gradually increased. The in-cylinder pressure detection value of FIG. 2 represents this increased growth phenomenon. The in-cylinder pressure waveform shown by the solid line L1 is due to spark ignition, and the waveform shown by the solid line L2 in the first self-ignition combustion. It was found that the solid lines L3, L4, L5, L6, L7 and the in-cylinder pressure gradually change as the number of turns increases.

  However, in the auto-ignition combustion at the later stage of the increasing phenomenon shown by the solid line L7, the maximum value of the in-cylinder pressure is much larger than the maximum value P1 at the time of normal combustion, but the initial value shown by the solid lines L4 and L5. In the self-ignition combustion at the stage, the maximum value of the in-cylinder pressure is almost the same as the maximum value P1 during normal combustion. Therefore, the conventional method for detecting the occurrence of self-ignition combustion based on whether or not the maximum value of the in-cylinder pressure exceeds the reference value as described in Patent Document 1 cannot detect self-ignition combustion at the initial stage.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a new self-ignition combustion detection device that can detect the occurrence of self-ignition combustion at an initial stage.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

The invention according to claim 1 is applied to a spark ignition internal combustion engine that is designed to have a high compression ratio and is ignited by a spark of a spark plug, and the cylinder pressure of the internal combustion engine or a physical quantity correlated with the cylinder pressure is determined as the cylinder pressure. Based on the value in a predetermined first period set after the piston top dead center of the combustion stroke among the in-cylinder pressure acquisition means acquired as a detection value and the in-cylinder pressure detection value acquired by the in-cylinder pressure acquisition means, Initial self-ignition combustion for determining whether or not initial stage self-ignition combustion is occurring, wherein the maximum value of the in-cylinder pressure detection value during self-ignition combustion is less than or equal to the maximum value of the in-cylinder pressure detection value during normal combustion An ignition determination means , wherein the initial auto-ignition determination means detects the in-cylinder pressure in the first period when the maximum value in the first period among the in-cylinder pressure detection values is during combustion without self-ignition. Than the maximum value It is determined that the self-ignition combustion in the initial stage has occurred when it is larger than a first threshold value set lower than the in-cylinder pressure detection value at the piston top dead center when combustion is not set and combustion has not occurred. characterized in that it.

  Among the in-cylinder pressure waveforms shown in FIG. 2 described above, when comparing the waveforms L4 and L5 at the time of self-ignition combustion at the initial stage with the waveform L1 at the time of normal combustion, a predetermined value after the piston top dead center TDC in the combustion stroke. The inventors have clarified that the difference can be recognized by comparing the waveforms in the first period G1. Accordingly, in the invention according to claim 1, wherein the presence or absence of self-ignition combustion at the initial stage is determined based on a value in the first period set after the piston top dead center of the combustion stroke among the in-cylinder pressure detection values. According to this, it is possible to easily detect the occurrence of self-ignition combustion in the initial stage.

Further , the initial self-ignition determination means is an initial stage when the maximum value in the first period among the in-cylinder pressure detection values is larger than a predetermined first threshold value (for example, a value indicated by symbol TH1 in FIG. 2). It is determined that self-ignition combustion is occurring. According to this, for example, by using a peak hold circuit or the like, it is possible to easily determine whether or not the initial stage ignition combustion has occurred. That is, in the example of FIG. 2, the auto-ignition combustion at the initial stage shown by the waveform L4 can be easily detected.

According to a second aspect of the present invention, the first threshold value is variably set according to an operating state of the internal combustion engine. For example, when the rotation speed of the crankshaft (hereinafter referred to as engine rotation speed) is high or the load of the internal combustion engine (hereinafter referred to as engine load) is high, the in-cylinder pressure due to normal combustion is reduced. Since the waveform also increases as a whole, in such a case, it is desirable to variably set the first threshold value used for the self-ignition initial determination to be increased. According to this, the determination accuracy of the self-ignition initial determination can be improved.

The invention according to claim 3 is characterized in that the first period is variably set according to an operating state of the internal combustion engine.

Among the in-cylinder pressure waveforms, the first period in which the difference between the waveforms L4 and L5 at the time of self-ignition combustion in the initial stage and the waveform L1 at the time of normal combustion appears significantly is the operating state of the internal combustion engine (for example, engine rotation) According to the invention of claim 3 in which the first period is variably set according to the operating state, the accuracy of determination by the initial self-ignition determination means can be improved.

According to a fourth aspect of the present invention, when the initial self-ignition determining means determines that the initial stage of self-ignition combustion has occurred, the initial content of changing the control content of the internal combustion engine so as to suppress the self-ignition combustion. Self-ignition suppression means is provided.

  According to this, since auto-ignition combustion is detected in the initial stage and the auto-ignition combustion is suppressed, it is possible to prevent the auto-ignition combustion with a large combustion energy from occurring due to the increased growth phenomenon.

As a specific example of the initial self-ignition suppression means, when the initial self-ignition determination means determines that the initial stage of self-ignition combustion has occurred, the control content of the fuel injection valve is increased so as to increase the fuel injection amount. include changing (see claim 5), and the closing timing of the intake valve changes the control content of the slower as the valve timing control apparatus to the piston bottom dead center of the intake stroke (see claim 6) It is done.

If the fuel injection amount is increased as in the fifth aspect of the invention , the injected liquid fuel is vaporized, so that the in-cylinder temperature can be cooled by the amount of heat of vaporization, so that self-ignition can be easily suppressed. Further, if the closing timing of the intake valve is made later than the piston bottom dead center of the intake stroke as described in claim 6 , the substantial compression period is shortened when the piston rises from the bottom dead center and compresses. Self-ignition can be easily suppressed.

In the invention of claim 7,8, wherein, among the cylinder pressure sensing value obtained by the cylinder pressure obtaining means, the maximum value at a predetermined second period including at least the piston top dead center of the combustion stroke, caused combustion The in-cylinder pressure at the time of self-ignition combustion is greater than a second threshold value set higher than the in-cylinder pressure detection value at the piston top dead center when not (for example, a value indicated by reference sign TH2 in FIG. 2). It is provided with late self-ignition determination means for determining that the maximum value of the detected value is a later stage of self-ignition combustion that is larger than the maximum value of the in-cylinder pressure detected value during normal combustion .

  As described above, when the waveforms L4 and L5 at the time of self-ignition combustion in the initial stage are compared with the waveform L1 at the time of normal combustion, the waveform is noticeable in the first period G1 after the piston top dead center TDC in the combustion stroke. Differences appear. On the other hand, when the waveform L7 at the time of self-ignition combustion in the later stage is compared with the waveform L1 at the time of normal combustion, a difference in the waveform appears significantly in a predetermined second period G2 including the piston top dead center of the combustion stroke. .

According to the invention described in claim 7, 8, wherein in view of this point, the initial stage of the self-ignition combustion, the occurrence or non-occurrence based on the cylinder pressure sensing value in the first period set after the piston top dead center The second stage of the self-ignition combustion is determined based on the in-cylinder pressure detection value in the second period including the piston top dead center, so that the second stage of the self-ignition combustion can be accurately detected and the initial stage It is possible to accurately detect whether a stage or a late stage has occurred.

  The second threshold value used in the determination by the late self-ignition determination means is desirably set to a value larger than the first threshold value used in the determination by the initial self-ignition determination means.

Further, in the invention according to claim 8 , when the late-stage self-ignition determining means determines that the late-stage auto-ignition combustion is occurring, the control content of the internal combustion engine is changed so as to suppress the self-ignition combustion. A late-stage self-ignition suppression means is provided, wherein the late-stage self-ignition suppression means performs the change so as to be largely suppressed as compared with the initial self-ignition suppression means or to stop the operation of the internal combustion engine.

As described above, since the combustion energy at the time of the late self-ignition is extremely large as compared with the time of the initial self-ignition, the parts of the internal combustion engine are further concerned when the late self-ignition occurs. Therefore, in the invention described in claim 8 , since the late self-ignition suppression means largely suppresses or stops the engine operation as compared with the initial self-ignition suppression means, the above-mentioned concerns can be solved preferably.

As specific examples of the late-stage self-ignition suppression means, as described in claim 9 , the intake air amount is limited, the engine rotational speed and the load are limited, the fuel injection is prohibited, and the internal combustion engine is stopped. Is mentioned. According to this, since late self-ignition can be avoided quickly, the above-mentioned concern about damage to each part of the internal combustion engine can be preferably eliminated.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.

  In this embodiment, a spark ignition type multi-cylinder four-cycle gasoline engine mounted on a vehicle is to be controlled, and electronic control of various actuators in the engine is performed. First, the overall schematic configuration of the engine control system will be described with reference to FIG.

  In the spark ignition engine (hereinafter referred to as the engine 10) shown in FIG. 1, an air flow meter 12 for detecting the intake air amount is provided upstream of the intake pipe 11. A throttle valve 14 whose opening degree is adjusted by a throttle actuator 13 such as a DC motor is provided on the downstream side of the air flow meter 12. The opening degree (throttle opening degree) of the throttle valve 14 is built in the throttle actuator 13. It is detected by the throttle opening sensor.

  An electromagnetically driven injector 16 (fuel injection valve) is provided on the downstream side of the surge tank portion 15 in the intake pipe 11, and is injected into the intake pipe 11 by the injector 16. That is, the engine 10 is a port injection type. High pressure fuel is supplied to the injector 16 through a high pressure pump (not shown) and a fuel pipe (delivery pipe).

  Further, an intake valve 17 and an exhaust valve 18 are respectively provided at the intake port and the exhaust port of the engine 10, and intake air is introduced into the combustion chamber 24 by the opening operation of the intake valve 17, and the opening operation of the exhaust valve 18 is performed. Thus, the exhaust gas after combustion is discharged to the exhaust pipe. The opening / closing timing (valve timing) of the intake valve 17 can be adjusted by a variable valve device 19 (valve timing adjusting device). Specifically, the variable valve device 19 is disposed in a power transmission path from the crankshaft 20 to the camshaft 21, and the relative position (phase) of the rotation angle of the camshaft 21 with respect to the rotation angle of the crankshaft 20 can be varied. It is a structure to do.

  A spark plug 22 is attached to each cylinder in the cylinder head of the engine 10, and a high voltage is applied to the spark plug 22 through an ignition coil 23 and the like at a desired ignition timing. By applying this high voltage, a spark discharge is generated between the opposing electrodes of each spark plug 22, and the fuel is ignited in the combustion chamber 24 and used for combustion.

  The cylinder block of the engine 10 includes an in-cylinder pressure sensor 25 that detects the pressure in the combustion chamber 24, a cooling water temperature sensor 26 that detects the temperature of engine cooling water, and a predetermined crank angle of the engine (for example, at a cycle of 30 ° CA). A crank angle sensor 27 and the like for outputting a rectangular crank angle signal are attached. Then, detection signals from these sensors 25, 26, 27 and the above-described air flow meter 12 are input to an electronic control unit (hereinafter referred to as ECU 40) that controls the engine. Further, the operation state of the engine 10 and various information on the vehicle, such as an accelerator sensor for detecting the accelerator operation amount by the vehicle driver, is input to the ECU 40 as indicated by reference numeral 28.

  The ECU 40 is composed mainly of a microcomputer comprising a CPU 42 (see FIG. 6), ROM, RAM, etc., and detects various sensors 12, 25-28, etc. by executing various control programs stored in the ROM. In accordance with the signal, the fuel injection amount and fuel injection timing of the injector 16, the ignition timing of the spark plug 22, the opening degree of the throttle valve 14, and the like are controlled, and the operation of the hydraulic actuator 29 of the variable valve device 19 is controlled. The opening / closing timing of the valve 17 is appropriately controlled.

  By the way, when the engine 10 is designed to have a high compression ratio, when the temperature of the combustion chamber 24 becomes high, compression ignition is performed at an earlier timing than when spark ignition is performed by the spark plug 22. There is concern about the occurrence of self-ignition combustion. As described above with reference to FIG. 2, the in-cylinder pressure waveform detected by the in-cylinder pressure sensor 25 gradually changes to L2, L3, L4, L5, L6, and L7 once self-ignition combustion occurs. Thus, the self-ignition combustion mode grows and grows so that the combustion energy gradually increases.

  The ECU 40 detects whether or not the self-ignition combustion L4 and L5 is generated in the initial stage and whether or not the self-ignition combustion L7 is generated in the late stage. Hereinafter, a procedure for determining whether self-ignition combustion has occurred will be described. FIG. 3 shows a procedure of base routine processing by the microcomputer of the ECU 40 that executes this determination. After starting with the ignition switch being turned on as a trigger, each predetermined cycle (for example, a calculation cycle performed by the CPU 42) or It is repeatedly executed at every predetermined crank angle. In addition, ECU40 when performing the process of FIG. 3 is corresponded to a self-ignition combustion detection apparatus.

  First, the program is initialized in step S1 of FIG. 3 as the base routine process, and the subsequent step S2 is a self-ignition detection gate (hereinafter referred to as a CI gate) for detecting self-ignition in the initial stage. This is a self-ignition detection gate routine to be set. The CI gate is a gate for extracting only a value detected in a predetermined first period G1, which will be described below, from a detection value (in-cylinder pressure detection value CP) of the in-cylinder pressure sensor 25.

  Here, in comparing the waveforms L4 and L5 at the time of self-ignition combustion in the initial stage and the waveform L1 at the time of normal combustion, the first of the crank angles after the top dead center TDC of the piston 30 in the combustion stroke is compared. As described above, the difference can be recognized by comparing the waveforms in the period G1. The first period G1 in which the difference is noticeable in the comparison between the waveforms L4 and L5 at the time of self-ignition combustion at the initial stage and the waveform L1 at the time of normal combustion is the operating state of the engine 10 (for example, the engine speed Ne or It varies according to the intake air amount Ga). Therefore, in step S2, the CI gate is set so that the predetermined period G1 is variably set according to the operation state.

  The subsequent step S3 (initial self-ignition determination means) is for determining whether or not self-ignition has occurred in the initial stage based on the in-cylinder pressure detection value CP extracted by the CI gate set in step S2. This is a self-ignition initial stage determination routine. In the subsequent step S4 (late self-ignition determination means), self-ignition in the later stage is performed based on the in-cylinder pressure detection value CP detected in the predetermined second period G2 including at least the top dead center of the piston 30 in the combustion stroke. It is a self-ignition late stage determination routine for determining whether or not it has occurred.

  Subsequent step S5 (initial self-ignition suppression means, late self-ignition suppression means) is a self-ignition for changing the control content of the engine so as to suppress the self-ignition combustion when it is determined in step S3 that self-ignition has occurred. This is an ignition suppression routine. After the routine processing in step S5 is completed, the initialization processing in step S1 is avoided, and the processing after step S2 is repeatedly executed.

  Next, details of the self-ignition detection gate routine in step S2 will be described with reference to FIG. The self-ignition detection gate routine S2 is a routine executed every TDC (every crank angle corresponding to the piston top dead center position).

  First, in step S201, the engine speed Ne calculated based on the detection signal output from the crank angle sensor 27 is read. Next, in step S202, the mass flow rate (intake air amount Ga) of the intake air calculated based on the detection signal output from the air flow meter 12 is read. Next, in step S203, the engine coolant temperature THw calculated based on the detection signal output from the coolant temperature sensor 26 is read.

  In subsequent step S204, it is determined whether or not the engine coolant temperature THw read in step S203 is higher than a predetermined water temperature α. Here, in the case of THw ≦ α, the warm-up state of the engine 10 is insufficient, so that the combustion is slow and the possibility of occurrence of self-ignition is extremely low. Therefore, when it is determined that THw ≦ α (S204: NO), in the subsequent step S205, the ON / OFF timing set for the self-ignition detection gate (CI gate) is initially set. Therefore, the presence / absence determination of the self-ignition combustion in step S3 is not substantially executed.

  On the other hand, when THw> α, there is a high possibility that self-ignition will occur. In subsequent steps S206 and S207, whether or not self-ignition combustion occurs in step S3 by setting the ON / OFF timing of the CI gate Make a decision. The ON / OFF timing is set based on the engine operating state (here, the engine rotation speed Ne and the intake air amount Ga).

  A map M1 in FIG. 4 is a map in which the optimal ON timing of the CI gate for Ne and Ga is stored, and a map M2 is a map in which the optimal OFF timing of the CI gate for Ne and Ga is stored. That is, the first period G1 in which the difference is noticeable in the comparison between the waveforms L4 and L5 at the time of self-ignition combustion in the initial stage and the waveform L1 at the time of normal combustion changes according to Ne and Ga. The optimal first period G1 in which the difference is noticeable according to Ga is acquired in advance by a test or the like, and the acquired optimal values are stored in the maps M1 and M2.

  In steps S206 and S207, the optimum ON timing (A) and the optimum OFF timing (B) are calculated with reference to the maps M1 and M2 based on Ne and Ga read in steps S201 and S202. When these calculations are made, this routine shown in FIG. 4 is terminated.

  Next, a CI gate generation process for designating a detection range (first period G1) for detecting self-ignition will be described with reference to a time chart shown in FIG.

  First, at the TDC timing t1, the time until the ON timing (A) calculated in step S206 is set in the timer A which is the time measuring means, and the time measurement by the timer A is started. Thereafter, when the timing count by the timer A reaches the ON timing (A), the CI gate is turned ON, and the time until the OFF timing (B) calculated in step S207 is set in the timer B which is the timing means. Then, the timer B starts timing. Thereafter, when the time count by the timer B reaches the OFF timing (B), the CI gate is turned OFF to generate the CI gate.

  Next, a hardware configuration for detecting the in-cylinder pressure CP and detecting self-ignition combustion in the initial stage will be described with reference to the block diagram of FIG.

  In the ECU 40, an A / D converter 41, a CPU 42, a gate circuit 43, a peak hold circuit 44, and the like shown in FIG. 6 are provided. The operation information (detection signal) of the engine 10 such as the engine rotation speed Ne, the intake air amount Ga, the cooling water temperature THw, etc. is sent from the various sensors 27, 12, 26 to the CPU 42 via the A / D converter 41 or directly. Entered. The in-cylinder pressure signal CP output from the in-cylinder pressure sensor 25 is taken into the peak hold circuit 44 via the gate circuit 43, and the peak hold signal CPPKH is input to the CPU.

  The gate circuit 43 functions to input the in-cylinder pressure signal CP to the peak hold circuit only when the gate is instructed by the CPU 42. The peak hold circuit 44 extracts the maximum value of the in-cylinder pressure signal CP input during the gate opening period (that is, the first period G1), and outputs it to the CPU 42.

  The state of the peak hold value CPPKH in this gate open section will be described using the time chart of FIG. The gate circuit 43 sets the section where the CI gate is ON as the gate opening section (first period G1), and the peak hold circuit 44 holds the peak pressure from the in-cylinder pressure CP of the gate opening section, and the hold value Is output to the CPU 42 as the peak hold value CPPKH. When the input peak hold value CPPKH is greater than the predetermined first threshold value TH1, the CPU 42 determines that the initial stage of self-ignition has occurred.

  The one-dot chain line in FIG. 7 shows changes in the in-cylinder pressure CP and the peak hold value CPPKH when there is no self-ignition, and the solid line in FIG. 7 shows changes in both values CP and CPPKH when there is self-ignition in the initial stage. Show. When it is determined that CPPKH> TH1 and the initial stage of self-ignition has occurred, the initial self-ignition generation flag XCI is set to 1.

  Of the waveform of the in-cylinder pressure CP shown in the uppermost stage of FIG. 7, a period in which a difference is noticeable in comparison between the waveform shown by the solid line during the auto-ignition combustion in the initial stage and the waveform during normal combustion shown by the one-dot chain line Changes according to the operating state of the engine 10 (for example, the engine rotational speed Ne and the intake air amount Ga), so that the gate opening section (first period G1) is variably set according to the operating state.

  In addition, when self-ignition combustion occurs in the initial stage, the in-cylinder pressure CP in the first period G1 increases as a whole, but the peak hold value CPPKH is equal to that at the time of TDC due to the compression of the piston 30. It may be lower than the in-cylinder pressure CP. For this reason, the first threshold value TH1 is set to a value lower than the in-cylinder pressure CP at the time of TDC when combustion does not occur.

  FIG. 8 is a flowchart showing the process of step S3 in the base routine of FIG. 3 for determining whether or not self-ignition has occurred in the above-described initial stage. This routine is executed every time the CI gate is turned OFF. It is.

  First, in step S301 (in-cylinder pressure acquisition means), the peak hold value CPPKH in the CI gate open section (first period G1) is read. The first period G1 in this embodiment is set to, for example, ATDC 30 ° C. A to 90 ° C. A.

  In subsequent step S302 (initial self-ignition determination means), it is determined whether or not CPPKH> TH1. If CPPKH ≦ TH1, it is determined that the initial stage self-ignition has not occurred, and the initial self-ignition occurrence flag XCI is set to zero in step S303. On the other hand, if CPPKH> TH1, it is determined that the initial stage of self-ignition has occurred, and the initial self-ignition occurrence flag XCI is set to 1 in step S304. After the processing of steps S303 and S304, this routine is terminated.

  As described above with reference to FIG. 2, once the self-ignition combustion occurs, the self-ignition combustion gradually increases and grows unless the control content of the engine 10 is changed so as to suppress the self-ignition combustion. FIG. 9 is a flowchart showing the process of step S4 in the base routine of FIG. 3 for determining whether or not self-ignition has occurred in the late stage of the increased growth as described above. This routine is executed for each combustion cycle. Routine.

  First, in step S401, the peak hold value CPPKHa of the in-cylinder pressure CP in a predetermined second period G2 (see FIG. 2) including the piston top dead center TDC in the combustion stroke is read. The second period G2 in the present embodiment is set to, for example, BTDC 30 ° C. A to ATDC 90 ° C. A.

  In subsequent step S402 (late self-ignition determination means), it is determined whether or not the peak hold value CPPKHa is larger than a predetermined second threshold value TH2. The second threshold TH2 is set to a value higher than the first threshold TH1. Further, the second threshold value TH2 is set to a value higher than the in-cylinder pressure CP at the time of TDC when combustion does not occur.

  If CPPKHa ≦ TH2, it is determined that late-stage self-ignition has not occurred, and the later-stage self-ignition occurrence flag XCIa is set to zero in step S403. On the other hand, if CPPKHa> TH2, it is determined that late-stage self-ignition has occurred, and the later-stage self-ignition occurrence flag XCIa is set to 1 in step S404. After the processing of steps S403 and S404, this routine is terminated.

  Next, details of the self-ignition suppression routine of step S5 in the base routine shown in FIG. 3 will be described.

  In the self-ignition suppression routine S5, when changing the engine control content so as to suppress self-ignition, when initial self-ignition is detected (XCI = 1) and when late self-ignition is detected (XCIa = 1). We try to suppress self-ignition by different methods. That is, when late self-ignition occurs, it is required to suppress self-ignition more immediately than when initial self-ignition occurs. Therefore, in the self-ignition suppression at the time of the late self-ignition, the engine 10 is limp home operation (degeneration operation) or the drive of the engine 10 is stopped in order to avoid damage to the crankshaft 20 or the like. As a specific example of the limp home operation, the opening of the throttle valve 14 is limited to a predetermined opening or less (for example, the opening during idle operation), or the engine rotational speed Ne or the intake air amount Ga is set to a predetermined value or less. Limiting can be mentioned. Further, as a specific example of engine drive stop, stopping fuel injection can be mentioned.

  On the other hand, a method of suppressing self-ignition when initial self-ignition occurs will be described below using the flowchart of FIG. Note that this routine shown in FIG. 10 is a routine executed for each TDC. First, in step S501, the engine speed Ne is read, and in the subsequent step S502, the intake air amount Ga is read. Next, when controlling the valve opening period of the intake valve 17 by the variable valve device 19, the target value (final VVT advance value TVVT) of the opening / closing period is calculated by the following steps S503 to S510.

  First, in step S503, the valve opening base advance value TVVTB by the variable valve device 19 is calculated based on the rotational speed Ne and the intake air amount Ga read in steps S501 and S502. Specifically, the optimal valve opening timing preset for each operation region determined by Ne and Ga is stored in the map M3 (see FIG. 10), and the value (C) read from the map M3 is stored in the valve opening base. Set as advance value TVVTB.

  Since the engine 10 according to the present embodiment is set to a high compression ratio, the optimum valve opening timing stored in the map M3 is set in consideration of the charging efficiency of intake air and the avoidance of the occurrence of self-ignition. . That is, the intake charge efficiency increases as the VVT advance value TVVT is advanced, but self-ignition tends to occur as a contradiction. Therefore, the above-described optimum valve opening timing is set so that the VVT advance value TVVT is advanced to a limit that does not cause self-ignition.

  Next, in step S504, based on the initial self-ignition generation flag XCI, it is determined whether or not initial stage self-ignition has occurred. If XCI = 1 and it is determined that initial self-ignition has occurred, the VVT retarded dither amount DCRVTA is calculated in the following step S505. The DCRVTA is a map M4 (see FIG. 10) showing an optimum dither amount set in advance for each operation region determined by Ne and Ga so that the VVT retardation speed can be changed according to the operation state of the engine 10 (Ne and Ga in this case). ) And the value (D) read from the map M4 is set as the VVT retarded dither amount DCRVTA.

  In the subsequent step S506, the VVT correction amount TDCRVVT is calculated. Specifically, as shown in Equation 1 below, the current TDCRVVT is calculated by adding the self-ignition correction DCRVTA to the previously calculated TDCRVVT. As a result, the VVT advance value TVVT is changed to the retard-side safety side, and self-ignition is suppressed.

TDCRVVT = TDCRVVT (i−1) + DCRVTA (Formula 1)
Next, in step S507, an upper limit value GDCRVTMAX of the VVT correction amount guard is obtained. Specifically, the optimum upper limit value set in advance for each operation region determined by Ne and Ga is stored in the map M5 (see FIG. 10), and the value (E) read from the map M5 is used as the upper limit value GDCRVTMAX. Set. In subsequent step S508, the lower limit value GDCRVTMIN of the VVT correction amount guard is obtained. Here, GDCRVTMIN is set to zero regardless of the engine operating region.

  In subsequent step S509, the VVT correction amount TDCRVVT calculated in step S506 is guarded with the upper limit value GDCRVTMAX and the lower limit value GDCRVTMIN set in steps S507 and S508. That is, when TDCRVVT calculated in step S506 is larger than GDCRVTMAX, the value of TDCRVVT is set to GDCRVTMAX, and when TDCRVVT calculated in step S506 is smaller than GDCRVTMIN, the value of TDCRVVT is set to GDCRVTMIN.

  Next, in step S510, a final VVT advance value TVVT is calculated. Specifically, as shown in Expression 2 below, the final VVT advance value TVVT is calculated by subtracting the TDCRVVT set in step S509 from the base advance value TVVTB calculated in step S503. That is, the base advance value TVVTB is corrected to the retard side by TDCRVVT.

TVVT = TVVTB−TDCRVVT (Formula 2)
If it is determined in step S504 that no self-ignition has occurred (XCI = 0), the VVT advance dither amount DCRVTS is calculated in step S511. Similar to the method calculated in step S505, the map is calculated for each driving region. In subsequent step S512, the VVT correction amount TDCRVVT is calculated in the same manner as in step S506. Specifically, as shown in Equation 3 below, the current TDCRVVT is calculated by subtracting the advance angle correction DCRVTS from the previously calculated TDCRVVT. As a result, the VVT advance value TVVT is changed to the advance side, and the improvement in the charging efficiency of the intake air is promoted.

TDCRVVT = TDCRVVT (i−1) + DCRVTS (Formula 3)
Next, how the TVVT that is the final VVT advance value changes by the process of FIG. 10 will be described with reference to the time chart of FIG.

  The uppermost stage in FIG. 11 represents the appearance timings t1 to t8 of the piston top dead center TDC in the combustion stroke, and the waveform of the in-cylinder pressure CP obtained for each combustion stroke is shown in the lowermost stage in FIG. Reference numerals (1) to (8) in the drawing represent timings at which the presence / absence of the initial self-ignition is determined based on the first threshold value TH1, and this determination is performed for each TDC.

  In the example of FIG. 11, it is determined in the determinations (1) to (4) that self-ignition combustion at the initial stage has occurred, and therefore the period from t1 to t4 is the initial self-ignition occurrence detection period. Continue to set the ignition occurrence flag XCI (XCI = 1). From the time when XCI = 1 is set, the VVT advance value TVVT continues to be retarded from the base value TVVTB by the retarded dither amount (DCRVTA) for each TDC. Therefore, in the case where the closing timing of the intake valve 17 is set later than the bottom dead center of the piston in the intake stroke, the piston rises from the bottom dead center and compresses as the closing timing is delayed. Since the compression period becomes shorter, the in-cylinder pressure CP decreases and self-ignition combustion is suppressed.

  Thereafter, the initial self-ignition generation flag XCI is set to zero from the time point when it is determined that the occurrence of self-ignition combustion has ceased (the time point determined by determination (5)), and the VVT advance value TVVT is set to advance dither for each TDC. Continue to advance from the base value TVVTB by an amount (DCRVTS). As described above, the feedback control is performed so as to repeat the VVT advance / retard according to whether or not the autoignition combustion in the initial stage is generated. Therefore, the VVT advance value TVVT is advanced to the limit of the autoignition occurrence, and the internal combustion is performed. The actual compression of the engine 10 can be increased, and the engine 10 is burned with high efficiency up to the limit where self-ignition does not occur.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) In comparing the in-cylinder pressure waveforms L4 and L5 at the time of self-ignition combustion in the initial stage and the waveform L1 at the time of normal combustion, the waveform in the first period G1 after the piston top dead center TDC in the combustion stroke is shown. Based on the knowledge that the difference can be recognized by comparison, the peak hold value CPPKH of the in-cylinder pressure CP in the first period G1 is detected, and when CPPKH> TH1, self-ignition combustion occurs in the initial stage. Is determined. Therefore, it is possible to easily detect the occurrence of self-ignition combustion in the initial stage.

  (2) Since the setting of the first threshold value TH1 and the first period G1 used to determine whether or not initial self-ignition has occurred is varied according to the operating state of the engine 10 (for example, the engine speed Ne, the intake air amount Ga, etc.) The determination accuracy of the self-ignition initial determination can be improved.

  (3) Here, when comparing the in-cylinder pressure waveform L7 at the time of self-ignition in the latter stage and the in-cylinder pressure waveform L1 at the time of normal combustion, if only the first period G1 is compared, there is a difference between the two waveforms L7 and L1. It hardly appears. Therefore, although the initial self-ignition can be detected according to the peak hold value CPPKH in the first period G1, it is difficult to detect the late self-ignition. Therefore, in this embodiment, apart from the determination of whether or not initial self-ignition has occurred in step S3, whether or not self-ignition has occurred in the later stage in step S4 is determined. Then, based on the knowledge that the difference between the two waveforms L7 and L1 can be recognized by comparing the waveforms in the second period G2 including the piston top dead center TDC of the combustion stroke, the peak of the in-cylinder pressure CP in the second period G2 A hold value CPPKHa is detected, and when CPPKHa> TH2, it is determined that self-ignition combustion is occurring in the later stage. Therefore, it is possible to easily detect not only the initial self-ignition combustion but also the late self-ignition combustion.

  (4) When initial self-ignition combustion is detected, by delaying the valve opening period of the intake valve 17 by the variable valve device 19, the substantial compression period in the compression stroke is shortened to reduce the in-cylinder pressure CP. . Therefore, self-ignition combustion can be easily suppressed.

(Other embodiments)
The present invention is not limited to the description of the above-described embodiments, and the characteristic configurations of the respective embodiments may be arbitrarily combined. In addition, each of the above embodiments may be modified as follows.

  Here, in the in-cylinder pressure waveforms L3, L4, and L5 at the time of self-ignition combustion in the initial stage, after the peak P1 appears at TDC, the peaks PE3, PE4, and PE5 appear again (see FIG. 2). Then, the appearance time of the peaks PE3, PE4, and PE5 again becomes earlier as the auto-ignition combustion increases and grows, and in the latter stage, the peak PE7 is again advanced to the vicinity of the TDC, and the peak P1 is superimposed again by the peak PE7. The knowledge that it does not appear was obtained.

  Therefore, in the embodiment shown in FIG. 8, whether or not initial self-ignition has occurred is determined based on the peak hold value CPPKH of the in-cylinder pressure CP in the first period G1, but in view of the above knowledge, the first period G1 It is also possible to detect the peak appearance time of the in-cylinder pressure CP, that is, the appearance time of the peaks PE3, PE4, and PE5 again, and determine that the initial self-ignition has occurred when the peak appearance time is earlier than the predetermined time.

  In addition, instead of determining whether or not initial self-ignition has occurred based on the peak hold value CPPKH (maximum value) of the in-cylinder pressure CP in the first period G1, the integrated value (area) of the in-cylinder pressure waveform in the first period G1, that is, The occurrence of initial self-ignition may be determined based on the value obtained by integrating the in-cylinder pressure CP in the first period G1.

  Here, an ion current flows through both electrodes of the spark plug 22 as combustion occurs in the combustion chamber 24. Since this ion current flows more as the flame caused by combustion increases, it can be said that the ion current has a correlation with the in-cylinder pressure. Therefore, in the embodiment shown in FIG. 1, the presence or absence of the initial self-ignition is determined based on the in-cylinder pressure CP detected by the in-cylinder pressure sensor 25. However, the ion current detection circuit 45 (see FIG. 1) that detects the ionic current described above. ) To determine whether or not initial self-ignition is based on the detected ion current. The waveform of the detected ion current value is the same as the waveform of the in-cylinder pressure CP exemplified in FIGS. Therefore, the presence / absence of initial self-ignition can be determined based on the ion current waveform by a method similar to the method for determining the presence / absence of initial self-ignition based on the in-cylinder pressure waveform in the first period G1.

  In the above-described embodiment shown in FIG. 1, self-ignition combustion is suppressed by retarding the valve opening period of the intake valve 17 by the variable valve device 19, but the present invention is such initial self-ignition suppression means. For example, by increasing the amount of fuel injected from the injector 16, the in-cylinder temperature is lowered due to vaporization of the injected liquid fuel, and self-ignition combustion is suppressed. It may be. Alternatively, in an engine equipped with an EGR system that circulates a part of the exhaust gas into the intake air, the combustion temperature may be lowered by increasing the EGR amount to suppress self-ignition combustion. Alternatively, in the case of a direct injection engine that directly injects fuel into the combustion chamber 24, the combustion temperature may be lowered by retarding the fuel injection timing during the compression stroke so as to suppress self-ignition combustion. .

The figure which shows the whole schematic structure of the engine control system concerning one Embodiment of this invention. It is a figure which shows an in-cylinder pressure change, and is a figure explaining a mode that self-ignition combustion increases and grows gradually. The flowchart which shows the procedure of the base routine process which determines the presence or absence of generation | occurrence | production of initial stage self-ignition combustion. The flowchart which shows the detail of the self-ignition detection gate routine in step S2 of FIG. The time chart explaining the production | generation process of CI gate which designates the detection range (1st period G1) for detecting self-ignition. FIG. 3 is a block diagram showing a hardware configuration for detecting in-cylinder pressure CP and detecting self-ignition combustion at an initial stage. The time chart which shows the state change of the peak hold value CPPKH in a gate open area (1st period G1). FIG. 4 is a flowchart showing details of an initial self-ignition determination routine in step S <b> 3 of FIG. 3. FIG. 4 is a flowchart showing details of a late self-ignition determination routine in step S4 of FIG. 3. The flowchart which shows the detail of the self-ignition suppression routine in step S5 of FIG. The time chart which shows the state of the change by correction | amendment of the advance value TVVT of the intake valve opening period by a variable valve apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 19 ... Variable valve apparatus (valve timing adjustment apparatus), 40 ... ECU (self-ignition combustion detection apparatus), G1 ... 1st period, G2 ... 2nd period, S3, S302 ... Initial self-ignition judgment means, S301 ... In-cylinder pressure acquisition Means, S4, S402 ... Late autoignition determination means, S5 ... Initial autoignition suppression means, Late autoignition suppression means, TH1 ... First threshold, TH2 ... Second threshold.

Claims (9)

Designed to have a high compression ratio and applied to spark ignition internal combustion engines that are ignited by sparks from spark plugs,
In-cylinder pressure acquisition means for acquiring a cylinder internal pressure of the internal combustion engine or a physical quantity correlated with the cylinder internal pressure as a cylinder internal pressure detection value;
Of the in-cylinder pressure detection values acquired by the in-cylinder pressure acquisition means, the in-cylinder pressure detection value at the time of self-ignition combustion is based on a value in a predetermined first period set after the piston top dead center of the combustion stroke . Initial self-ignition determination means for determining whether or not initial-stage self-ignition combustion in which the maximum value is equal to or less than the maximum value of the in-cylinder pressure detection value during normal combustion ;
Equipped with a,
The initial self-ignition determination means sets the maximum value in the first period among the in-cylinder pressure detection values higher than the maximum value of the in-cylinder pressure detection value in the first period during combustion without self-ignition. And when it is larger than the first threshold value set lower than the detected cylinder pressure at the piston top dead center when combustion is not occurring, it is determined that the auto-ignition combustion in the initial stage has occurred. A self-ignition combustion detector characterized by the above. The self-ignition combustion detection apparatus according to claim 1 , wherein the first threshold value is variably set according to an operating state of the internal combustion engine. 3. The self-ignition combustion detection apparatus according to claim 1, wherein the first period is variably set according to an operating state of the internal combustion engine. Comprising initial self-ignition suppression means for changing the control content of the internal combustion engine to suppress self-ignition combustion when the initial self-ignition determination means determines that initial stage self-ignition combustion has occurred. The self-ignition combustion detection device according to any one of claims 1 to 3 . The initial self-ignition suppression means changes the control content of the fuel injection valve so as to increase the fuel injection amount when it is determined by the initial self-ignition determination means that the initial stage self-ignition combustion has occurred. The self-ignition combustion detection apparatus according to claim 4 . The internal combustion engine is equipped with a valve timing adjusting device capable of changing the closing timing of the intake valve,
The initial self-ignition suppression means, when the initial self-ignition determination means determines that the initial stage self-ignition combustion has occurred, the closing timing of the intake valve is higher than the piston bottom dead center of the intake stroke. 6. The self-ignition combustion detection device according to claim 4 or 5 , wherein the control content of the valve timing adjustment device is changed so as to be delayed. Among the in-cylinder pressure detection values acquired by the in-cylinder pressure acquisition means, the maximum value in a predetermined second period including at least the piston top dead center of the combustion stroke is the piston top dead center when combustion has not occurred. The maximum value of the in-cylinder pressure detection value at the time of self-ignition combustion is approximately the same as the maximum value of the in-cylinder pressure detection value at the time of normal combustion when greater than a second threshold value set higher than the in-cylinder pressure detection value. self-ignition combustion detection apparatus according to any one of claims 1-3, characterized in that also comprises a late self-ignition determination means determines that the later stages of high self-ignition combustion. Among the in-cylinder pressure detection values acquired by the in-cylinder pressure acquisition means, the maximum value in a predetermined second period including at least the piston top dead center of the combustion stroke is the piston top dead center when combustion has not occurred. The maximum value of the in-cylinder pressure detection value at the time of self-ignition combustion is approximately the same as the maximum value of the in-cylinder pressure detection value at the time of normal combustion when greater than a second threshold value set higher than the in-cylinder pressure detection value. A later- stage self-ignition determination means for determining that it is a later stage of the larger self-ignition combustion,
Late auto-ignition suppression means for changing the control content of the internal combustion engine to suppress self-ignition combustion when it is determined by the late auto-ignition determination means that late-stage auto-ignition combustion has occurred,
With
In the late ignition suppression means, greatly inhibited in comparison with the initial self-ignition suppression means, or any one of claims 4-6, wherein: performing the change so as to stop the operation of the internal combustion engine The self-ignition combustion detector described in 1. The late self-ignition suppression means changes the control content to limit the intake air amount into the combustion chamber of the internal combustion engine, or changes the control content to limit the engine rotation speed and load of the internal combustion engine, or 9. The self-ignition combustion detection apparatus according to claim 8 , wherein the control content is changed so that fuel injection is prohibited and the operation of the internal combustion engine is stopped.

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