JP2008008235A - Internal combustion engine stop / start control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stop/start control device of an internal combustion engine capable of avoiding self-ignition at a start time, while suppressing an influence exerted on setting of a start control condition of the internal combustion engine. <P>SOLUTION: In this stop/start control device of the internal combustion engine for stopping the internal combustion engine when a prescribed stop condition is fulfilled, and starting the internal combustion engine when a prescribed restart condition is fulfilled, it is determined whether self-ignition is generated at the start time of the internal combustion engine or not (step S1), and when determined that the self-ignition is generated, the start control condition of the internal combustion engine is corrected so that the self-ignition is avoided at the start time in the next time or thereafter of the internal combustion engine (step S3). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a stop / start control device having a function of avoiding self-ignition during startup of an internal combustion engine.

An internal combustion engine is stopped when a predetermined stop condition is satisfied, and when the predetermined restart condition is satisfied, the predetermined stop condition is a stop / start control device that causes the internal combustion engine to burn and start the internal combustion engine. If it is established, the fuel injection timing of the internal combustion engine is retarded, the ignition timing is retarded, the external electric load is cut, etc., to reduce the engine speed, and when the engine speed falls to a predetermined range, the fuel injection is performed. And a control device that stops the piston of one of the cylinders within a predetermined range during the expansion stroke suitable for the next start by temporarily stopping the throttle valve opening and increasing the throttle valve opening (for example, Patent Documents). 1).
JP 2004-293444 A

  In order to start the internal combustion engine satisfactorily, control conditions (hereinafter referred to as start control conditions) that affect combustion at start-up, such as fuel injection timing, ignition timing, and throttle valve opening, are determined according to engine conditions such as water temperature. The above-described piston stop position control is also performed as one of the conditions for adjusting the start control condition. However, the start control condition for obtaining good startability is close to a region where self-ignition occurs in the internal combustion engine (hereinafter referred to as a self-ignition region). For this reason, the possibility of self-ignition increases if the start control conditions vary due to a shift in the stop position of the piston or the like. When self-ignition occurs, unfavorable phenomena such as a rapid increase in engine speed, an increase in vibration, and the generation of self-ignition noise occur, and good start cannot be realized. On the other hand, if the start control condition is moved away from the self-ignition region more than necessary, the setting of the start control condition is restricted, and the startability is deteriorated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a stop / start control device for an internal combustion engine capable of avoiding self-ignition during start-up while suppressing the influence on the setting of the start control condition of the internal combustion engine.

  The present invention provides an internal combustion engine stop / start control apparatus that stops an internal combustion engine when a predetermined stop condition is satisfied and starts the internal combustion engine when a predetermined restart condition is satisfied. Self-ignition determination means for determining whether self-ignition has occurred, and when it is determined that self-ignition has occurred, start of the internal combustion engine in a direction to avoid self-ignition at the next start of the internal combustion engine The above-described problem is solved by providing a control condition correction unit that corrects the control condition.

  According to the stop / start control device of the present invention, it is determined whether or not self-ignition has occurred when the internal combustion engine is started in accordance with specific start control conditions, and when it is determined that self-ignition has occurred, The starting control condition at that time is corrected in a direction to avoid self-ignition. As a result, the internal combustion engine is started under the corrected start control condition at the next and subsequent start, and the possibility of self-ignition is reduced. In response to the occurrence of self-ignition, the start control condition is corrected for the next and subsequent start, so it is not necessary to set the start control condition strictly more than necessary in advance for fear of self-ignition. Therefore, initially, the start control conditions are set so that a good startability of the internal combustion engine can be obtained, and when the self-ignition occurs under the start control conditions, the start control conditions should be corrected to the extent necessary to avoid self-ignition. That's fine. For this reason, it is not necessary to tighten or limit the start control condition more than necessary. As a result, it is possible to avoid self-ignition at the start while suppressing the influence on the setting of the start control condition.

  In one embodiment of the stop / start control apparatus of the present invention, the self-ignition determining means determines whether or not a characteristic at the time of self-ignition appears in a physical quantity that changes reflecting the combustion state in the internal combustion engine. It may be determined whether ignition has occurred (Claim 2). The self-ignition determination means compares the detected value of the physical quantity that reflects the combustion state in the internal combustion engine with a reference value that should be detected during ignition combustion with respect to the physical quantity, thereby comparing the self-ignition level. It may be determined whether or not has occurred (claim 3). Further, the self-ignition determination means uses, as a reference time, a timing at which a change corresponding to the start of ignition combustion should appear in the detected value of the physical quantity that reflects the ignition timing of the internal combustion engine or the combustion state in the internal combustion engine. It may be determined whether or not the self-ignition has occurred by comparing the reference time and the time when the change corresponding to the actual start of combustion appears in the detected value of the physical quantity. Item 4). The physical quantity may be at least one of engine speed, angular acceleration of the crankshaft, in-cylinder pressure, vibration acceleration of the internal combustion engine, and self-ignition sound.

  The operating state of the internal combustion engine can be specified by detecting various physical quantities, but physical quantities such as the engine speed, crankshaft angular acceleration, in-cylinder pressure, and acceleration of vibration generated in the internal combustion engine reflect the combustion state of the internal combustion engine. Therefore, the combustion state such as the combustion speed and the combustion start time can be estimated from the detected value. When self-ignition occurs, combustion progresses explosively near the compression end, so the engine speed or in-cylinder pressure rises rapidly, vibrations increase, and self-ignition noise is generated. Behavior or phenomenon occurs. Therefore, if a physical quantity that changes reflecting the combustion state is detected and it is determined whether or not a change indicating the characteristics of self-ignition appears in the detected value, it is determined appropriately whether or not self-ignition has occurred. can do. In particular, when self-ignition occurs, since the combustion speed is high, the maximum values of the engine speed, the in-cylinder pressure, etc. are larger than those during ignition combustion. Therefore, it is possible to accurately determine whether or not self-ignition has occurred by comparing the detected value of the physical quantity reflecting the combustion state with the reference value to be detected during ignition combustion with respect to the physical quantity. In addition, when self-ignition occurs, combustion is usually started at a timing different from the ignition timing or the combustion start timing at the time of ignition combustion, typically earlier than these timings. Therefore, if the ignition timing or the combustion start timing in the case of ignition combustion is examined in advance and set as the reference time, and the reference time is compared with the timing at which a change corresponding to the start of combustion appears with respect to the detected value of the physical quantity, self-ignition It is possible to more appropriately determine whether or not the occurrence has occurred.

  In one form of the stop / start control device of the present invention, the control condition correction means includes, as the start control condition, a target stop position related to a crankshaft or a piston of an internal combustion engine, a condition for prohibiting fuel injection at start, You may correct | amend at least any one of a fuel injection amount and the intake charge efficiency at the time of a start in the direction in which the said self-ignition is avoided (Claim 6).

  For example, if the target stop position is set to avoid the area where self-ignition occurs but the self-ignition occurs, the area where self-ignition occurs is expanded to narrow the target stop position setting range. In addition, it is possible to avoid the occurrence of self-ignition at the time of starting after the next time. If self-ignition occurs even if the conditions for prohibiting fuel injection are set in advance to avoid the occurrence of self-ignition, the conditions for prohibiting fuel injection will be expanded to Occurrence of self-ignition at start-up can be avoided. The conditions for prohibiting fuel injection can be set in association with, for example, the position of the crankshaft or piston at the start, the coolant temperature at the start, or the like. With respect to the fuel injection amount at the time of starting, by increasing or decreasing the fuel injection amount suitable for the starting, it is possible to obtain an effect of making the combustion progress slowly and avoiding self-ignition. Further, with regard to the intake charging efficiency at the time of start-up, it is possible to reduce the compression end pressure by reducing this, thereby suppressing the temperature rise due to the compression of the air-fuel mixture, and obtaining the effect of avoiding self-ignition. The intake charging efficiency can be reduced by, for example, delaying the closing timing of the intake valve.

  As described above, according to the stop / start control device of the present invention, the start control condition is corrected in consideration of the self-ignition because the start control condition is corrected for the next and subsequent start in response to the occurrence of self-ignition. It is not necessary to set more strictly than necessary. Therefore, initially, the start control condition is set so that a good startability of the internal combustion engine can be obtained, and when the self-ignition occurs under the start control condition, the start control condition is corrected to the extent necessary to avoid self-ignition. And start control conditions need not be tightened or limited more than necessary. As a result, it is possible to avoid self-ignition at the start while suppressing the influence on the setting of the start control condition.

  FIG. 1 shows an example of an internal combustion engine as a vehicle driving power source to which a stop / start control apparatus according to an embodiment of the present invention is applied. In FIG. 1, an internal combustion engine (hereinafter referred to as an engine) 1 is configured as a four-cycle engine, for example, and includes a plurality of cylinders 2. Although only a single cylinder 2 is shown in FIG. 1, the configuration of the other cylinders 2 is the same.

  The phases of the pistons 3 in each cylinder 2 are shifted from each other according to the number and layout of the cylinders 2. For example, in the case of an in-line four-cylinder engine in which four cylinders 2 are arranged in one direction, the phase of the piston 3 is shifted by 180 ° as a crank angle. Accordingly, the piston 3 of any one of the four cylinders 2 is always in the intake stroke, and the piston 3 of any one of the other cylinders 2 is always in the expansion stroke. The engine 1 is configured as a port injection engine that injects fuel from a fuel injection valve 4 into an intake port, introduces an air-fuel mixture into the cylinder 2, and ignites the air-fuel mixture from a spark plug 6. The fuel injected from the fuel injection valve 4 is gasoline as an example. Further, the engine 1 includes an intake valve 9 and an exhaust valve 10 that open and close between the combustion chamber 5 and the intake passage 7 and the exhaust passage 8, a throttle valve 13 that adjusts an intake air amount from the intake passage 7, and a piston 3. A connecting rod 15 and a crank arm 16 that transmit the reciprocating motion to the crankshaft 14 as a rotational motion are provided. These configurations may be the same as those of a known engine.

  The engine 1 is provided with a starter motor 17 for starting it. The starter motor 17 is a known electric motor that rotates the crankshaft 14 via the reduction gear mechanism 18. The reduction gear mechanism 18 incorporates a one-way clutch that allows rotation transmission from the starter motor 17 to the crankshaft 14 and prevents rotation transmission from the crankshaft 14 to the starter motor 17 in the middle of the rotation transmission path. Accordingly, some of the gears of the reduction gear mechanism 18 always mesh with the crankshaft 14. Thereby, the starter of the engine 1 is configured as a so-called always-mesh starter.

  The operating state of the engine 1 is controlled by an engine control unit (hereinafter referred to as ECU) 20. The ECU 20 is configured as a computer including a microprocessor and peripheral devices such as RAM and ROM necessary for its operation, and executes various processes necessary for controlling the operating state of the engine 1 according to a program recorded in the ROM. To do. As an example, the ECU 20 detects the pressure of the intake passage 7 and the air-fuel ratio of the exhaust passage 8 from an output signal of a predetermined sensor, and controls the fuel injection amount of the fuel injection valve 4 so that the predetermined air-fuel ratio is obtained. . The sensors referred to by the ECU 20 include a crank angle sensor 21 that outputs a signal corresponding to the phase (crank angle) of the crankshaft 14, a water temperature sensor 22 that outputs a signal corresponding to the cooling water temperature of the engine 1, and the pressure in the cylinder 2. An in-cylinder pressure sensor 23 that outputs a signal corresponding to (in-cylinder pressure) and a vibration sensor 24 that detects vibration acceleration of the engine 1 are provided. The vibration sensor 24 functions as a so-called knock sensor that detects the acceleration of vibration generated due to knocking of the engine 1 and can also detect the acceleration of vibration generated due to self-ignition of the engine 1. In addition, a sensor for detecting the opening degree of the accelerator pedal, a sensor for detecting the operation of the brake pedal, and the like are provided, but these are not shown. Further, the ECU 20 can control the opening degree by operating the throttle valve 13.

  The ECU 20 performs so-called idle stop control in which when the predetermined stop condition is satisfied, the fuel injection to the engine 1 is stopped and its operation is stopped, and when the predetermined restart condition is satisfied, the engine 1 is restarted. Run against. The stop condition and the restart condition may be set in the same manner as a known technique related to idle stop control. When the stop condition is satisfied, the ECU 20 controls the stop operation of the engine 1 so that the piston 3 or the crankshaft 14 stops at a target stop position suitable for the next start. As an example, the ECU 20 uses a correlation existing between the engine speed per unit time (engine speed) and the stop position of the piston 3 to make a target stop when any piston 3 is in the expansion stroke. Stop control is performed such that the fuel injection is stopped when the engine speed decreases to the region where the engine stops at the position. Such stop control is already known, and in this embodiment, the same stop control as those known examples is executed by the ECU 20. Further, the restart procedure is controlled in the same manner as in the known example.

  Further, the ECU 20 executes a self-ignition avoidance control routine shown in FIG. 2 when the engine 1 is started in order to suppress the occurrence of self-ignition when the engine 1 is started. The self-ignition avoidance control routine is repeatedly executed at a predetermined period after the restart condition of the engine 1 is satisfied and until the engine speed is stabilized in a predetermined speed range after the engine 1 is started.

  In the self-ignition avoidance control routine of FIG. 2, the ECU 20 first executes a subroutine process for determining whether or not self-ignition has occurred in the first step S1. In subsequent step S2, the ECU 20 determines whether or not the self-ignition determination flag for determining whether or not self-ignition has occurred is on, that is, whether or not the self-ignition has occurred. When the self-ignition determination flag is on, the ECU 20 proceeds to step S3, and executes a subroutine process for correcting the start control condition of the engine 1 in a direction to avoid self-ignition at the next and subsequent start. When the subroutine processing in step S3 is completed, the ECU 20 ends the current self-ignition avoidance control routine. If it is determined in step S2 that the self-ignition determination flag is off, the ECU 20 skips step S3 and ends the current routine.

  Next, the self-ignition determination method in step S1 of FIG. 2 described above will be described. If self-ignition occurs when the engine 1 is started, it is difficult to control the torque of the engine 1 properly, and it is difficult to control the torque of the engine 1 at the time of ignition combustion, such as rapid increase in engine speed, increase in engine vibration, and generation of self-ignition sound A characteristic behavior different from the behavior occurs. In the present embodiment, a physical quantity that changes reflecting the combustion state of the engine 1 is detected, and whether or not self-ignition has occurred is determined by determining whether or not the above-described characteristics at the time of self-ignition appear in the detected value. Determine. Hereinafter, some examples for determining self-ignition will be described.

  FIG. 3 shows the relationship between the crank angle CA and the engine speed NE when the engine 1 is started. The IG on the horizontal axis is the ignition timing controlled by the ECU 20. Furthermore, the solid line IF in the figure shows the change in the engine speed NE when ignition combustion is normally performed, the imaginary line MF shows the change in the engine speed NE when misfire occurs, and the broken line SI shows that self-ignition occurred. The change in the engine speed NE in each case is shown.

  As is apparent from FIG. 3, at the time of ignition combustion, after the ignition timing IG has passed, the engine speed NE starts to rise as compared with that at the time of misfire. On the other hand, when self-ignition occurs, it ignites near the compression top dead center and explosive combustion occurs, so the engine speed NE rises early and a single combustion period, for example, compression The maximum value of the engine speed between the dead center and the expansion bottom dead center becomes higher than the maximum value of the engine speed during ignition combustion, and a clear difference ΔNE occurs between the two. Therefore, the maximum value of the engine speed in one combustion period is detected, and if the detected value is higher than the maximum value (reference value) of the engine speed that should be detected during ignition combustion, self-ignition has occurred. Can be determined.

  FIG. 4 shows the relationship between the crank angle CA and the angular acceleration α of the crankshaft 14 when the engine 1 is started. The IG on the horizontal axis is the ignition timing controlled by the ECU 20, the solid line IF in the figure shows the change in the angular acceleration α when ignition combustion is normally performed, and the imaginary line MF is the angular acceleration α in the case of misfire. The broken line SI shows the change of the angular acceleration α when self-ignition occurs.

  As is apparent from FIG. 4, the angular acceleration α during ignition combustion rises higher than that during misfire after the ignition timing IG. On the other hand, at the time of self-ignition, since combustion is started earlier than the ignition timing IG, the angular acceleration α rises earlier than that at the time of misfiring at a timing earlier than the ignition timing IG. Therefore, the timing when the angular acceleration α rises higher than that at the time of misfire and the ignition timing IG as the reference time are compared, and it is determined that self-ignition has occurred when the rising timing is earlier than the ignition timing IG. Can do. The timing at which the angular acceleration α rises from that at the time of misfiring during ignition combustion is a crank angle CAx that is later than the ignition timing IG. Therefore, instead of the ignition timing IG, the crank angle CAx as a reference time and the actual It may be determined that self-ignition has occurred when the angular acceleration α rises at a time earlier than the crank angle CAx by comparing with the rising time of the angular acceleration α.

  FIG. 5 shows the relationship between the crank angle CA and the internal pressure (in-cylinder pressure) P of the cylinder 2 when the engine 1 is started. The IG on the horizontal axis is the ignition timing controlled by the ECU 20, the solid line IF in the figure shows the change in the in-cylinder pressure P when ignition combustion is normally performed, and the imaginary line MF is the in-cylinder pressure P in the case of misfire. The broken line SI indicates the change, and the change in the in-cylinder pressure P when self-ignition occurs.

  As is apparent from FIG. 5, the in-cylinder pressure P at the time of ignition combustion rises higher than that at the time of misfire after the ignition timing IG has passed. On the other hand, during self-ignition, explosive combustion starts earlier than the ignition timing IG, so that the in-cylinder pressure P rises earlier than that at the time of misfire, and the maximum value is also ignition combustion. Significantly greater than that of time. Accordingly, when the in-cylinder pressure P rises earlier than that at the time of misfiring in one combustion period and the rise timing of the in-cylinder pressure P is earlier than the ignition timing IG compared to the ignition timing as the reference time, self-ignition Can be determined to have occurred. The maximum value of in-cylinder pressure P in one combustion period is detected, and it is determined that self-ignition has occurred when the detected value is larger than the maximum value (reference value) of in-cylinder pressure P to be detected during ignition combustion. May be.

  In addition to the above, it is possible to determine whether or not self-ignition has occurred, for example, by vibration of the engine 1. For example, when self-ignition occurs, the rising timing of the vibration acceleration generated in the engine 1 is earlier than the rising timing (reference time) that should be detected during ignition combustion, or the vibration during one combustion period The maximum value of acceleration becomes larger than the maximum value (reference value) of vibration acceleration that should be detected during ignition combustion. Therefore, the timing at which the vibration acceleration rises more than that at the time of misfire in one combustion period is compared with the rise timing of the vibration acceleration at the time of ignition combustion, and the rise timing is the rise of the vibration acceleration that should be detected at the time of ignition combustion. If it is earlier than the time, it can be determined that self-ignition has occurred. Alternatively, the maximum value of vibration acceleration in one combustion period may be detected, and it may be determined that self-ignition has occurred when the detected value is larger than the maximum value of vibration acceleration to be detected during ignition combustion.

  Next, a self-ignition determination routine executed by the ECU 20 as a subroutine process of step S1 of FIG. 2 will be described with reference to FIGS. FIG. 6 is an example of a subroutine process for realizing the determination method shown in FIG. 3, that is, the method for determining self-ignition based on the engine speed. In the self-ignition determination routine of FIG. 6, the ECU 20 acquires the engine speed based on the output signal of the crank angle sensor 21 in step S101, and stores the maximum value of the engine speed in one combustion period as a storage medium such as a RAM. Hold on. In subsequent step S102, the ECU 20 determines whether or not one combustion period has ended, based on the output of the crank angle sensor 21, and ends the current routine if it has not ended.

  When one combustion period has ended in step S102, the ECU 20 proceeds to step S103, and whether or not the maximum value of the engine speed held in step S101 is larger than the maximum value of the engine speed during ignition combustion. Judge. The maximum value of the engine speed at the time of ignition combustion is obtained in advance by a conformance test or computer simulation or the like and stored in the ROM or the like of the ECU 20. If the condition of step S103 is satisfied, the ECU 20 determines that self-ignition has occurred, proceeds to step S104, and sets the self-ignition determination flag to ON. On the other hand, when the condition of step S103 is not satisfied, the ECU 20 determines that self-ignition has not occurred, proceeds to step S105, and sets the self-ignition determination flag to OFF. After setting the self-ignition determination flag in step S104 or S105, the ECU 20 ends the current routine.

  FIG. 7 is an example of a subroutine process for realizing the determination method shown in FIG. 4, that is, the method for determining self-ignition based on the angular acceleration of the crankshaft 14. In the self-ignition determination routine of FIG. 7, the ECU 20 calculates the angular acceleration of the crankshaft 14 based on the output signal of the crank angle sensor 21 in step S111. For example, the angular acceleration is calculated by differentiating the rotational speed of the crankshaft 14 detected by the crank angle sensor 21 once with time. In subsequent step S112, ECU 20 determines whether or not the calculated value of angular acceleration is larger than the angular acceleration (setting value) at the time of misfire in order to determine the rising timing of angular acceleration. The angular acceleration at the time of misfire is obtained in advance by a conformance test or computer simulation or the like, and is stored as a set value in the ROM or the like of the ECU 20.

  If the condition of step S112 is not satisfied, the ECU 20 ends the current routine. On the other hand, if the condition of step S112 is satisfied, the ECU 20 determines that the angular acceleration has risen from that at the time of misfire due to combustion, and stores the crank angle at that time in the RAM in step S113. In subsequent step S114, the ECU 20 determines whether or not the stored crank angle, that is, the crank angle when the angular acceleration rises is earlier than the ignition timing. If the crank angle is earlier than the ignition timing, the ECU 20 determines that self-ignition has occurred, proceeds to step S114, and sets the self-ignition determination flag to ON. On the other hand, if the condition of step S114 is not satisfied, the ECU 20 determines that self-ignition has not occurred, proceeds to step S116, and sets the self-ignition determination flag to OFF. After setting the self-ignition determination flag in step S115 or S116, the ECU 20 ends the current routine.

  FIG. 8 is another example of subroutine processing for determining self-ignition based on the angular acceleration of the crankshaft 14. Of the processes executed in the self-ignition determination routine of FIG. 8, steps S121 to S123 are the same as steps S111 to S113 of FIG. 7, and a description thereof is omitted. In the self-ignition determination routine of FIG. 8, the processing after the crank angle corresponding to the rising timing of the angular acceleration is stored in step S123 is different from the routine of FIG. That is, after the crank angle is stored in step S123, the ECU 20 determines in step S124 whether the crank angle is faster than the crank angle when the angular acceleration rises during ignition combustion. The rising timing of the angular acceleration at the time of ignition combustion is obtained in advance by a conformance test or computer simulation or the like and stored in the ROM or the like of the ECU 20. If the crank angle is earlier than that at the time of ignition combustion, the ECU 20 determines that self-ignition has occurred, proceeds to step S124, and sets the self-ignition determination flag to ON. On the other hand, if the condition of step S124 is not satisfied, the ECU 20 determines that self-ignition has not occurred, proceeds to step S126, and sets the self-ignition determination flag to OFF. After setting the self-ignition determination flag in step S125 or S126, the ECU 20 ends the current routine.

  FIG. 9 is an example of a subroutine process for determining self-ignition based on the determination method shown in FIG. 5, that is, the in-cylinder pressure. In the self-ignition determination routine of FIG. 9, the ECU 20 captures the output signal of the in-cylinder pressure sensor 23 in step S131, and in the subsequent step S132, the in-cylinder pressure specified from the output of the in-cylinder pressure sensor is determined in order to determine the combustion start timing. It is judged whether or not it is larger than the value at the time of misfire (setting value). The in-cylinder pressure at the time of misfire is obtained in advance by a conformance test or computer simulation or the like, and is stored as a set value in the ROM or the like of the ECU 20.

  If the condition of step S132 is not satisfied, the ECU 20 ends the current routine. On the other hand, if the condition in step S132 is satisfied, the ECU 20 determines that combustion has started, and stores the crank angle at that time in the RAM in step S133. In the subsequent step S134, the ECU 20 determines whether or not the stored crank angle, that is, the crank angle when combustion is started is earlier than the crank angle when combustion is started during ignition combustion. The crank angle at the time of ignition combustion is also obtained in advance by a conformance test or computer simulation or the like and stored in the ROM of the ECU 20 or the like. If the crank angle is earlier than that at the time of ignition combustion, the ECU 20 determines that self-ignition has occurred, proceeds to step S135, and sets the self-ignition determination flag to ON. On the other hand, if the condition of step S134 is not satisfied, the ECU 20 determines that self-ignition has not occurred, proceeds to step S136, and sets the self-ignition determination flag to OFF. After setting the self-ignition determination flag in step S135 or S136, the ECU 20 ends the current routine.

  FIG. 10 is another example of a subroutine process for determining self-ignition based on the in-cylinder pressure. In the self-ignition determination routine of FIG. 10, the ECU 20 captures the output signal of the in-cylinder pressure sensor 23 in step S141, and in the subsequent step S142, stores the maximum value of the in-cylinder pressure (maximum in-cylinder pressure) in one combustion period in the RAM or the like. Hold on the medium. In subsequent step S143, the ECU 20 determines whether or not one combustion period has ended, based on the output of the crank angle sensor 21, and ends the current routine if it has not ended.

  When one combustion period has ended in step S143, the ECU 20 proceeds to step S144, and determines whether or not the maximum in-cylinder pressure held in step S142 is greater than the maximum in-cylinder pressure (set value) during ignition combustion. To do. The maximum in-cylinder pressure at the time of ignition combustion is obtained in advance by a conformance test or computer simulation or the like, and is stored as a set value in the ROM or the like of the ECU 20. If the condition of step S144 is satisfied, the ECU 20 determines that self-ignition has occurred, proceeds to step S145, and sets the self-ignition determination flag to ON. On the other hand, if the condition of step S144 is not satisfied, the ECU 20 determines that self-ignition has not occurred, proceeds to step S146, and sets the self-ignition determination flag to OFF. After setting the self-ignition determination flag in step S145 or S146, the ECU 20 ends the current routine.

  FIG. 11 is an example of a subroutine process for determining self-ignition based on the vibration of the engine 1. In the self-ignition determination routine of FIG. 11, the ECU 20 captures the output signal of the vibration sensor 24 in step S151, and in the subsequent step S152, the vibration acceleration output from the vibration sensor 24 is used to determine the combustion start timing. It is determined whether or not it is larger than the vibration acceleration value (set value). The vibration acceleration at the time of misfire is obtained in advance by a conformance test or computer simulation or the like and stored as a set value in the ROM of the ECU 20 or the like.

  If the condition of step S152 is not satisfied, the ECU 20 ends the current routine. On the other hand, when the condition of step S152 is satisfied, the ECU 20 determines that combustion has started, and stores the crank angle at that time in the RAM in step S153. In the subsequent step S154, the ECU 20 determines whether or not the stored crank angle, that is, the crank angle when the combustion is started is earlier than the crank angle when the combustion is started during the ignition combustion. The crank angle at the time of ignition combustion is also obtained in advance by a conformance test or computer simulation or the like and stored in the ROM of the ECU 20 or the like. If the crank angle is earlier than that at the time of ignition combustion, the ECU 20 determines that self-ignition has occurred, proceeds to step S155, and sets the self-ignition determination flag to ON. On the other hand, if the condition of step S154 is not satisfied, the ECU 20 determines that self-ignition has not occurred, proceeds to step S156, and sets the self-ignition determination flag to OFF. After setting the self-ignition determination flag in step S155 or S156, the ECU 20 ends the current routine.

  FIG. 12 is another example of subroutine processing for determining self-ignition based on the vibration of the engine 1. In the self-ignition determination routine of FIG. 12, the ECU 20 captures the output signal of the vibration sensor 24 in step S161, and holds the maximum value of vibration acceleration in one combustion period in a storage medium such as a RAM in subsequent step S162. In subsequent step S163, the ECU 20 determines whether or not one combustion period has ended, based on the output of the crank angle sensor 21, and ends the current routine if it has not ended.

  When one combustion period is completed in step S163, the ECU 20 proceeds to step S164, and the maximum value of vibration acceleration held in step S162 is the maximum value (set value) of vibration acceleration generated in the engine 1 during ignition combustion. It is judged whether it is larger than. The maximum value of vibration acceleration at the time of ignition combustion is obtained in advance by a conformance test or computer simulation or the like, and is stored as a set value in the ROM or the like of the ECU 20. If the condition of step S164 is satisfied, the ECU 20 determines that self-ignition has occurred, proceeds to step S165, and sets the self-ignition determination flag to ON. On the other hand, when the condition of step S164 is not satisfied, the ECU 20 determines that self-ignition has not occurred, proceeds to step S166, and sets the self-ignition determination flag to OFF. After setting the self-ignition determination flag in step S165 or S166, the ECU 20 ends the current routine.

  Next, the correction of the start control condition executed in step S3 of FIG. 2 described above will be described. The correction of the start control condition is realized by correcting the control condition that affects the combustion at the start of the engine 1 and that can be changed by the ECU 20 in a direction in which self-ignition is avoided. The correction target includes a target stop position of the piston 3, conditions for prohibiting fuel injection at the start, fuel injection amount, intake valve closing timing, and the like.

  FIG. 13 shows an example of correcting the target stop position of the piston 3. The left half of FIG. 13 shows the target stop position of the piston 3 that reaches the first (first) compression top dead center (TDC) when the engine 1 starts, and the right half reaches the compression TDC second after the engine 1 starts. Each target stop position of the piston 3 is shown. The hatched region in the figure is a self-ignited region where it is determined that there is a high possibility that self-ignition will occur when fuel is injected from the state where the piston 3 is stopped to start the region. The self-ignition region covers a predetermined range before and after the compression bottom dead center (BDC). In the stop control of the engine 1 by the ECU 20, the target stop position of the piston 3 is set avoiding the self-ignition region. If the self-ignition area is set wider than necessary, the range of the target stop position of the piston 3 is narrowed, the stop position of the piston 3 needs to be controlled with higher accuracy, and the control difficulty increases. It takes longer time to stop. Therefore, the self-ignition region shown in FIG. 13 is preferably set to the minimum necessary range.

  However, if the self-ignition region is set to be narrow, the piston 3 stops in the self-ignition region due to mechanical errors, control errors, etc. of the engine 1, and as a result, there is a high possibility that self-ignition will occur at the start. Therefore, when self-ignition occurs, correction is made so that the target stop position is narrowed by expanding the self-ignition region to the compression TDC side as indicated by an arrow A in FIG. The possibility of starting starting from the ignition region is reduced, and the occurrence of self-ignition is avoided. Further, if the self-ignition region is initially set narrow, the range of the target stop position of the piston 3 can be narrowed to the limit necessary for avoiding self-ignition. Thereby, it becomes possible to avoid the occurrence of self-ignition while suppressing the influence on the stop position control of the piston 3.

  FIG. 13 also shows an example in which the condition for prohibiting fuel injection at the start is corrected. The ECU 20 avoids self-ignition by prohibiting fuel injection when the starting state of the engine 1 satisfies a predetermined condition. For example, when the position of the piston 3 at the time of starting is in the self-ignition region (injection prohibited region) shown in FIG. 13, the ECU 20 inhibits self-ignition by prohibiting fuel injection into the cylinder 2 in which the piston 3 is inserted. Avoid occurrence. However, even if such control is executed, self-ignition may occur due to a mechanical error of the engine 1 or the like. Therefore, when self-ignition occurs, the occurrence of self-ignition can be avoided at the next and subsequent startups by expanding the injection prohibited area in the same manner as the expansion of the self-ignition area described above.

  FIG. 14 shows another example of correcting the condition for prohibiting fuel injection. The ECU 20 prohibits fuel injection by determining that there is a high possibility that self-ignition will occur when the water temperature at the start of the engine 1 is in an injection prohibition region higher than a predetermined threshold value Twth. In this case, when self-ignition occurs even when the water temperature is in the injection permission region, the threshold value Twth is corrected to a lower temperature value Twth ′ as shown by an arrow A in the figure to expand the injection prohibition region. By doing so, it is possible to avoid the occurrence of self-ignition at the next and subsequent startups.

  Even when correcting the conditions for prohibiting fuel injection as described above, if the injection prohibited area is initially set to be narrow, the injection prohibited area can be expanded to an appropriate range according to the frequency of occurrence of self-ignition. it can. Accordingly, it is possible to avoid the occurrence of self-ignition without setting the fuel injection prohibition condition more strictly than necessary.

  FIG. 15 shows an example of correcting the fuel injection amount as the start control condition. When the engine 1 is started, the ECU 20 sets a target value for the fuel injection amount so that an air-fuel ratio suitable for starting the engine 1 is obtained, and controls the operation of the fuel injection valve 4 according to the target value. Between the fuel injection amount and the possibility of self-ignition, the possibility of self-ignition shows a peak when the fuel injection amount is controlled near the optimum value as shown in FIG. As a boundary, the possibility of self-ignition decreases if the fuel injection amount changes either on the increase side (arrow AR direction) or on the decrease side (arrow AL direction). Therefore, when self-ignition occurs, the occurrence of self-ignition can be avoided by correcting the fuel injection amount at the next or subsequent start to either the increase side or the decrease side. Even in this case, if self-ignition does not occur, the fuel injection amount is controlled to an optimum value, and inconveniences such as insufficient torque at start-up or misfire are avoided, and the fuel injection amount is reduced only when self-ignition occurs. By correcting, it is possible to avoid the occurrence of self-ignition at the next and subsequent startups. Thereby, it is possible to avoid the occurrence of self-ignition while suppressing the deterioration of the startability of the engine 1 due to the increase or decrease of the fuel injection amount.

  FIG. 16 shows an example of correcting the closing timing of the intake valve 9 as the start control condition. The closing timing of the intake valve 9 correlates with the intake charging efficiency or the in-cylinder pressure (compression end pressure) at the compression TDC. Generally, the closing timing of the intake valve 9 is set in the vicinity of the compression BDC, more specifically, the timing when the piston 3 passes the compression BDC and enters the compression stroke. When the closing timing is further retarded to the compression TDC side, a part of the intake air is pushed back to the intake passage 7 by the piston 3 in the compression stroke, and the intake charging efficiency is lowered, and the compression end pressure is also lowered accordingly. If the compression end pressure decreases, the temperature rise of the air-fuel mixture accompanying compression decreases, and the possibility of self-ignition decreases. Thus, when self-ignition occurs, self-ignition can be avoided by retarding the closing timing of the intake valve 9 at the next and subsequent startups as shown by arrow A in FIG. In this case, initially, the closing timing of the intake valve 9 is set to a timing at which an optimal compression end pressure is obtained for starting, and the closing timing of the intake valve 9 is gradually avoided according to the frequency of occurrence of self-ignition. Can be retarded as much as necessary. As a result, it is possible to avoid the occurrence of self-ignition while suppressing the deterioration of the startability of the engine 1 due to the delay of the closing timing of the intake valve 9.

  Next, a start control condition correction routine executed by the ECU 20 as a subroutine process in step S3 of FIG. 2 will be described with reference to FIGS. FIG. 17 is an example of a subroutine process for correcting the target stop position of the piston 3 to avoid self-ignition. In the start control condition correction routine of FIG. 17, the ECU 20 determines in step S301 whether the target stop position correction completion flag is on, and if it is on, ends the current routine. On the other hand, when the target stop position correction completion flag is not on, the ECU 20 proceeds to step S302 and determines whether or not the self-ignition determination flag is on. When the self-ignition determination flag is off, that is, when it is determined by the self-ignition determination routine illustrated in FIGS. 6 to 12 that self-ignition has not occurred, the ECU 20 ends the current routine. On the other hand, when the self-ignition determination flag is on, that is, when it is determined that self-ignition has occurred, the ECU 20 proceeds to step S303 and executes correction regarding the target stop position of the piston 3. This correction is executed so as to expand the crank angle range set as the self-ignition region as indicated by an arrow A in FIG. The correction amount may be a predetermined amount. In subsequent step S304, the ECU 20 sets the target stop position correction completion flag to ON, and thereafter ends the current routine.

  The target stop position corrected by the above processing is referred to at the next stop control by the ECU 20, and the stop operation of the engine 1 is controlled so that the piston 3 stops at the corrected target stop position. As a result, the piston position as one of the start control conditions is corrected in a direction to avoid self-ignition at the start after the next time.

  FIG. 18 is an example of a subroutine process for correcting self-ignition by correcting a fuel injection prohibited region (hereinafter referred to as “injection prohibited crank angle”) related to the crank angle. In the start control condition correction routine of FIG. 18, the ECU 20 acquires the crank angle at the start based on the output signal of the crank angle sensor 21 in step S311. If the crank angle at the time of start has already been acquired, that value is retained. In the next step S312, the ECU 20 determines whether or not the injection prohibition crank angle correction completion flag is set to ON. If the flag is on, the ECU 20 ends the current routine. On the other hand, if the flag is not on in step S312, the ECU 20 proceeds to step S313 and determines whether or not the self-ignition determination flag is set to on. In this case, it may be determined whether or not the self-ignition determination flag has been turned on in the past at the same starting crank angle as the starting crank angle acquired in step S311. If the self-ignition determination flag is not on, the ECU 20 ends the current routine. On the other hand, if the self-ignition determination flag is on, the ECU 20 proceeds to step S314 and executes correction of the injection prohibited crank angle. This correction is executed so as to expand the injection prohibited area related to the crank angle as indicated by an arrow A in FIG. The correction amount may be a predetermined amount. In subsequent step S315, the ECU 20 sets the injection prohibition crank angle correction completion flag to ON, and thereafter ends the current routine.

  The injection prohibited crank angle corrected by the above processing is referred to when the ECU 20 starts the engine 1 after the next time. When the piston 3 is at the injection prohibited crank angle, the cylinder 2 in which the piston 3 is located is referred to. The fuel injection from the fuel injection valve 4 is prohibited. Thereby, the injection prohibition region (injection prohibition crank angle) as one of the start control conditions is corrected in a direction to avoid self-ignition at the start after the next time.

  FIG. 19 is an example of a subroutine process for correcting self-ignition by correcting a fuel injection prohibition condition (hereinafter referred to as an injection water temperature prohibition condition) set in relation to the water temperature. In the start control condition correction routine of FIG. 19, the ECU 20 acquires the start-time water temperature detected by the water temperature sensor 22 in step S321. If the starting water temperature has already been acquired, the water temperature is maintained. In the next step S322, the ECU 20 determines whether or not the injection water temperature prohibition condition correction completion flag is set to ON. If the flag is on, the ECU 20 ends the current routine. On the other hand, if the flag is not on in step S322, the ECU 20 proceeds to step S323 and determines whether or not the self-ignition determination flag is set to on. In this case, it may be determined whether or not the self-ignition determination flag has been turned on in the past at the same starting water temperature as that acquired in step S321. If the self-ignition determination flag is not on, the ECU 20 ends the current routine. On the other hand, when the self-ignition determination flag is on, the ECU 20 proceeds to step S324, and corrects the injection water temperature prohibition condition. This correction is executed so as to expand the injection prohibited region to the low temperature side as indicated by an arrow A in FIG. The correction amount may be a predetermined amount. In subsequent step S325, the ECU 20 sets the injection water temperature prohibition condition correction completion flag to ON, and thereafter ends the current routine.

  The injection water temperature prohibition condition corrected by the above process is referred to when the ECU 20 starts the engine 1 from the next time onward, and when the starting water temperature is in the corrected injection prohibited region, at least the fuel injection timing is first set. The fuel injection from the fuel injection valve 4 to the cylinder 2 that reaches is prohibited. Thereby, the injection water temperature prohibition condition as one of the start control conditions is corrected in a direction to avoid self-ignition at the start after the next time.

  FIG. 20 is an example of a subroutine process for correcting the fuel injection amount at the start to avoid self-ignition. In the start control condition correction routine of FIG. 20, the ECU 20 acquires the crank angle at the start based on the output signal of the crank angle sensor 21 in step S331. If the crank angle at the time of start has already been acquired, that value is retained. In the next step S332, the ECU 20 determines whether or not the injection correction completion flag is set to ON. If the flag is on, the ECU 20 ends the current routine. On the other hand, if the flag is not on in step S332, the ECU 20 proceeds to step S333 and determines whether or not the self-ignition determination flag is set to on. In this case, it may be determined whether or not the self-ignition determination flag has been turned on in the past at the same starting crank angle as the starting crank angle acquired in step S331. If the self-ignition determination flag is not on, the ECU 20 ends the current routine. On the other hand, when the self-ignition determination flag is on, the ECU 20 proceeds to step S334, and corrects the fuel injection amount at the time of start. In this case, the fuel injection amount may be corrected to the decreasing side as shown by the arrow AL in FIG. 15, that is, the side where the air-fuel ratio becomes lean, or the fuel injection amount is increased to the increasing side as shown by the arrow AR, That is, the air / fuel ratio may be corrected to the rich side. The correction amount may be a predetermined amount. In subsequent step S335, the ECU 20 sets the injection correction completion flag to ON, and thereafter ends the current routine.

  The fuel injection amount corrected by the above processing is referred to when the ECU 20 starts the engine 1 from the next time onward, and at least the fuel injection amount from the fuel injection valve 4 for the cylinder 2 that reaches the fuel injection timing first is corrected. The operation of the fuel injection 4 is controlled so that the fuel injection amount becomes the same. As a result, the injection injection amount as one of the start control conditions is corrected in a direction to avoid self-ignition at the start after the next time.

  FIG. 21 shows an example of a subroutine process for correcting the closing timing of the intake valve 9 at the start to avoid self-ignition. In the start control condition correction routine of FIG. 21, the ECU 20 determines in step S331 whether or not the intake valve closing timing correction completion flag is set to ON. If the flag is on, the ECU 20 ends the current routine. On the other hand, if the flag is not on in step S341, the ECU 20 proceeds to step S342 and determines whether or not the self-ignition determination flag is set to on. In this case, it may be determined whether or not the self-ignition determination flag has been turned on in the past while the same closing timing as the intake valve closing timing set at the present time is set. If the self-ignition determination flag is not on, the ECU 20 ends the current routine. On the other hand, when the self-ignition determination flag is on, the ECU 20 proceeds to step S343, and performs the closing timing correction of the intake valve 9 at the time of start. This correction is realized by retarding the intake valve closing timing to the compression TDC side as indicated by an arrow A in FIG. The correction amount may be a predetermined amount. In subsequent step S344, the ECU 20 sets the intake valve closing timing correction completion flag to ON, and thereafter ends the current routine.

  The intake valve closing timing corrected by the above processing is referred to when the ECU 20 starts the engine 1 after the next time, and at least the closing timing of the intake valve 9 opened at the time of starting is controlled to the corrected timing. . As a result, the intake valve closing timing as one of the start control conditions is corrected in a direction to avoid self-ignition at the start after the next time.

  In the above embodiment, the ECU 20 functions as a self-ignition determination unit by executing any one of the processes in FIGS. 6 to 12, and the control condition correcting unit by executing any one of the processes in FIGS. 17 to 21. Function as. Note that the ECU 20 may execute any one of the self-ignition determination routines shown in FIGS. 6 to 12 as a subroutine process in step S1 of FIG. 2, or two or more self-ignition determination routines in parallel. May be executed. Further, the ECU 20 may execute any one of the start control condition correction routines shown in FIGS. 17 to 21 as a subroutine process of step S3 in FIG. 2, or may execute two or more start control condition correction routines. It may be executed in parallel.

  The present invention is not limited to the form described above, and may be implemented in an appropriate form. For example, whether or not self-ignition has occurred is not limited to the above-described example of determination based on physical quantities such as engine speed, angular acceleration, in-cylinder pressure, or vibration acceleration. You may determine from a physical quantity. Whether or not self-ignition has occurred may be determined based on whether or not the detected value of the combustion sound of the internal combustion engine includes self-ignition sound. The correction of the start control condition for avoiding the self-ignition is not limited to the target stop value, the injection prohibition region or the injection prohibition condition, the fuel injection amount, and the intake valve closing timing described above. Any start control condition that can cause an action may be appropriately corrected. For example, the correction for reducing the intake charging efficiency is not limited to the correction for retarding the intake valve closing timing, and appropriate corrections such as correction for reducing the opening of the throttle valve and correction for reducing the supercharging effect of intake air are possible. is there.

1 is a diagram showing an outline of an internal combustion engine to which a stop / start control apparatus according to an embodiment of the present invention is applied. The flowchart which shows the self-ignition avoidance control routine which ECU of FIG. 1 performs. The figure which shows an example of the relationship between the crank angle at the time of start-up of an internal combustion engine, and an engine speed. The figure which shows an example of the relationship between the crank angle at the time of start-up of an internal combustion engine, and the angular acceleration of a crankshaft. The figure which shows an example of the relationship between the crank angle at the time of start-up of an internal combustion engine, and a cylinder internal pressure. The flowchart which shows the self-ignition determination routine which ECU performs in order to determine self-ignition based on an engine speed. The flowchart which shows the self-ignition determination routine which ECU performs in order to determine self-ignition based on the angular acceleration of a crankshaft. The flowchart which shows the other example of the self-ignition determination routine which ECU performs in order to determine self-ignition based on the angular acceleration of a crankshaft. The flowchart which shows the self-ignition determination routine which ECU performs in order to determine self-ignition based on a cylinder pressure. The flowchart which shows the other example of the self-ignition determination routine which ECU performs in order to determine self-ignition based on a cylinder pressure. The flowchart which shows the self-ignition determination routine which ECU performs in order to determine self-ignition based on a vibration acceleration. The flowchart which shows the other example of the self-ignition determination routine which ECU performs in order to determine self-ignition based on a vibration acceleration. The figure which shows the example which correct | amends a target stop position or a fuel-injection prohibition area | region in order to avoid self-ignition. The figure which shows the example which correct | amends a fuel-injection prohibition area | region in relation to the water temperature at the time of starting in order to avoid self-ignition. The figure which shows the example which correct | amends the fuel injection quantity at the time of a start in order to avoid self-ignition. The figure which shows the example which correct | amends the intake valve closing timing at the time of starting in order to avoid self-ignition. The flowchart which shows the starting control condition correction | amendment routine which ECU performs in order to correct | amend a target stop position and to avoid self-ignition. The flowchart which shows the starting control condition correction | amendment routine which ECU performs in order to correct | amend the fuel injection prohibition area | region in relation to a crank angle, and to avoid self-ignition. The flowchart which shows the starting control condition correction | amendment routine which ECU performs in order to correct | amend the fuel injection prohibition area | region in relation to the water temperature at the time of starting, and to avoid self-ignition. The flowchart which shows the starting control condition correction | amendment routine which ECU performs in order to correct | amend the fuel injection quantity at the time of starting, and to avoid self-ignition. The flowchart which shows the starting control condition correction | amendment routine which ECU performs in order to correct | amend the intake valve closing timing at the time of starting, and to avoid self-ignition.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Piston 4 Fuel injection valve 9 Intake valve 13 Throttle valve 14 Crankshaft 20 Engine control unit (self-ignition judgment means, control condition correction means)
21 Crank angle sensor 22 Water temperature sensor 23 In-cylinder pressure sensor 24 Vibration sensor

Claims (6)

In an internal combustion engine stop / start control device that stops an internal combustion engine when a predetermined stop condition is satisfied, and starts the internal combustion engine when a predetermined restart condition is satisfied,
Self-ignition determination means for determining whether or not self-ignition has occurred when starting the internal combustion engine;
When it is determined that self-ignition has occurred, control condition correction means for correcting the start-up control condition of the internal combustion engine in a direction to avoid self-ignition at the next start of the internal combustion engine;
A stop / start control apparatus for an internal combustion engine.   The self-ignition determination means determines whether or not self-ignition has occurred by determining whether or not a characteristic at the time of self-ignition appears in a physical quantity that changes reflecting the combustion state in the internal combustion engine. The stop / start control apparatus according to claim 1.   The self-ignition determination means generates the self-ignition by comparing the detected value of the physical quantity that reflects the combustion state in the internal combustion engine with a reference value that should be detected during ignition combustion with respect to the physical quantity. The stop / start control apparatus according to claim 1, wherein it is determined whether or not it has been performed.   The self-ignition determination means sets, as a reference time, a timing at which a change corresponding to the start of ignition combustion should appear in a detected value of a physical quantity that reflects the ignition timing of the internal combustion engine or a combustion state in the internal combustion engine. The determination of whether or not the self-ignition has occurred is made by comparing the reference time with a time when a change corresponding to the actual start of combustion appears in the detected value of the physical quantity. The stop / start control device according to 1.   The physical quantity is at least one of engine speed, crankshaft angular acceleration, in-cylinder pressure, vibration acceleration of the internal combustion engine, and self-igniting sound. The stop / start control device according to item.   The control condition correction means includes at least a target stop position related to a crankshaft or a piston of an internal combustion engine, a condition for prohibiting fuel injection at start, a fuel injection amount at start, and an intake charging efficiency at start as the start control condition. The stop / start control apparatus according to claim 1, wherein any one of the corrections is corrected in a direction in which the self-ignition is avoided.

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