JP2010229928A - Ignition timing control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control the ignition timing of an internal combustion engine in consideration of a correlation between the ignition timing and a timing when a predetermined combustion ratio is reached. <P>SOLUTION: An ignition timing control device 1 of the internal combustion engine 10 includes: a calculation means calculating a value representing a relation between the timing when the predetermined combustion ratio is reached in a combustion chamber 14 and the ignition timing; and an ignition timing correction means correcting the ignition timing so that the value calculated by the calculation means does not deviate from a predetermined relation area. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

Pay attention to the combustion ratio, which is the ratio of the heat generation amount until a predetermined timing between the two points (heat generation amount ratio) with respect to the total heat generation amount (total heat generation amount) between two points in a combustion chamber. Thus, it has been proposed to control the internal combustion engine. For example, Patent Document 1 discloses that a combustion ratio at a specific timing in a certain combustion chamber is calculated, and the ignition timing of the internal combustion engine is set based on the combustion ratio. This combustion ratio is calculated by calculating the in-cylinder pressure P (θ) detected using the in-cylinder pressure sensor when the crank angle is θ and the in-cylinder volume V (θ) when the crank angle is the same θ. This is performed by paying attention to a product value P (θ) · V ^κ (θ) with a value V ^κ (θ) raised to a specific heat ratio (predetermined index) κ. In this calculation, the in-cylinder pressure P (θ1) at the first timing (timing when the crank angle becomes θ1) after the intake valve is closed and before ignition, and the second timing (crank) after ignition and before the exhaust valve is opened. In-cylinder pressure P (θ2) at an angle θ2) and in-cylinder pressure at a specific timing at which the crank angle between the first timing and the second timing is θ0 (where θ1 <θ0 <θ2) P (θ0) is used. Based on the in-cylinder pressure at these three points, the combustion ratio at the specific timing is obtained, and the ignition timing is set based on the combustion ratio.

JP 2006-144642 A

  As a result of the inventor's earnest research, when the ignition timing is moved to the advance side, the timing at which the predetermined combustion ratio is moved to the advance side, and conversely, the case where the timing is moved to the retard side It was found that there is. By focusing on this point and performing ignition timing control, it is expected that the air-fuel mixture is burned more appropriately.

  Accordingly, the present invention has been made in view of such a point, and an object thereof is to control the ignition timing of the internal combustion engine in consideration of the correlation between the ignition timing and the timing at which the predetermined combustion ratio is obtained. .

An ignition timing control apparatus for an internal combustion engine according to the present invention includes a calculation unit that calculates a value representing a relationship between a timing at which a predetermined combustion ratio is obtained in a combustion chamber and an ignition timing, and the value calculated by the calculation unit has a predetermined relationship. Ignition timing correction means for correcting the ignition timing so as not to deviate from the region is provided.

It is a graph which shows the example of a correlation with product value PV ( ^kappa) and the amount of heat generation in a combustion chamber. It is a graph which shows the correlation example of the combustion rate calculated | required based on product value PV ( ^kappa) , and the combustion rate calculated ^| required based on a heat release rate. It is a graph showing the relationship between 50% combustion timing and ignition timing. It is a graph which shows the correlation with the ignition timing and torque of an internal combustion engine when charging efficiency and engine speed are constant. 1 is a schematic configuration diagram showing an internal combustion engine to which an embodiment of the present invention is applied. It is a flowchart for demonstrating the routine for ignition timing basic control performed in embodiment. It is a flowchart for demonstrating the routine for ignition timing correction | amendment control performed in embodiment. It is a graph showing the relationship between an ignition timing and an evaluation value.

  First, the calculation of the combustion ratio in the combustion chamber based on the in-cylinder pressure will be exemplarily described based on FIGS.

In the same manner as described with respect to Patent Document 1, here, the cylinder pressure detected or estimated by the cylinder pressure detection means at the timing when the crank angle is θ is P (θ), and the crank angle is θ. The in-cylinder volume (when detecting or estimating the in-cylinder pressure P (θ)) is V (θ), and the specific heat ratio is κ. A product value P (θ) · V ^κ (θ) (hereinafter referred to as a value V (θ) obtained by raising the in-cylinder pressure P (θ) and the in-cylinder volume V (θ) by a specific heat ratio (predetermined index) κ. The combustion ratio is calculated by paying attention to “PV ^κ ” as appropriate.

It is known that the change pattern of the heat generation amount Q in the combustion chamber of the internal combustion engine with respect to the crank angle and the change pattern of the product value PV ^κ with respect to the crank angle have a correlation as shown in FIG. Reference 1). In FIG. 1, the solid line shows the in-cylinder pressure detected at a predetermined minute crank angle in a predetermined model cylinder and the value obtained by raising the in-cylinder volume at the time of detection of the in-cylinder pressure by a predetermined specific heat ratio κ. The product value PV ^κ is plotted. Further, in FIG. 1, the broken line indicates the heat generation amount Q in the model cylinder based on the following equation (1):

As calculated and plotted. In either case, for simplicity, κ = 1.32. In FIG. 1, −360 °, 0 ° and 360 ° are top dead centers (when the piston is located at the top dead center), and −180 ° and 180 ° are bottom dead centers (the piston is located at the bottom dead center). Corresponding to).

As can be seen from the results shown in FIG. 1, the change pattern of the heat generation amount Q with respect to the crank angle and the change pattern of the product value PV ^κ with respect to the crank angle are approximately the same (similar). In particular, before and after the start of combustion of the air-fuel mixture in the cylinder (for spark ignition in a gasoline engine) (for example, a range from about -180 ° to about 135 ° in FIG. 1), both patterns in FIG. To be understood.

Using the correlation between the heat generation amount Q and product value PV ^kappa in the combustion chamber, the cylinder pressure detected or estimated by the in-cylinder pressure detection means, and cylinder volume at the time when detecting or estimating of the cylinder pressure Combustion that is a ratio of a heat generation amount between two points to a predetermined timing (a heat generation amount ratio) with respect to a total heat generation amount (total heat generation amount) between two points based on the product value PV ^κ of The ratio MFB is determined (measured). Here, if the combustion ratio in the combustion chamber is calculated based on the product value PV ^κ , the combustion ratio in the combustion chamber can be obtained with high accuracy without requiring high-load calculation processing. That is, as shown in FIG. 2, the combustion rate obtained based on the product value PV ^κ (see the solid line in the figure) is substantially the same as the combustion rate obtained based on the heat generation rate (see the broken line in the figure). To do.

  In FIG. 2, the solid line represents the combustion ratio at the timing when the crank angle = θ in the model cylinder described above, according to the following equation (2) and based on the detected in-cylinder pressure P (θ), It is a plot. However, for simplicity, κ = 1.32. In FIG. 2, the broken line indicates the combustion ratio at the timing when the crank angle = θ in the above model cylinder, according to the above equation (1) and the following equation (3), and the detected in-cylinder pressure P (θ). Calculated based on the above and plotted. Also in this case, for simplicity, κ = 1.32.

Here, an example in which two timings of 120 ° before compression top dead center (simply −120 ° in equation (2)) and 120 ° after compression top dead center (simply 120 ° in equation (2)) are adopted. The calculation of the combustion ratio focused on PV ^κ was explained. However, they may be at other timings, such as 60 ° before compression top dead center to eliminate the effects of ignition noise, and 60 ° after compression top dead center to cover all combustion modes. Can be °.

  Here, in a combustion cycle in a certain combustion chamber, the timing at which the combustion ratio becomes a predetermined amount (timing at which the predetermined combustion ratio becomes), here, the timing at which the predetermined combustion ratio becomes 50% (50% combustion timing) CA50, and the ignition timing Since the relationship with SA was examined, the relationship is shown in FIG. In this experiment, the engine speed NE and the intake charging efficiency KL were fixed, and the change in the 50% combustion ratio CA50 with respect to the change in the ignition timing was examined. The experiment was performed for a plurality of combinations of the engine speed NE and the intake charging efficiency KL. In FIG. 3, the horizontal axis represents the 50% combustion timing CA50, and the vertical axis represents the ignition timing SA in the combustion cycle in which the 50% combustion timing CA50 is calculated. However, on the horizontal axis, “0 °” corresponds to the piston positioned at the compression top dead center, and “20 °” corresponds to a crank angle of 20 ° (ATDC 20 °) after the compression top dead center. In the vertical axis of FIG. 3, the ignition timing SA is taken with MBT as a reference (corresponding to 0 ° on the vertical axis in FIG. 3). MBT is obtained from each experimental data, and the experimental results are shown in FIG. 3 based on the MBT. In the vertical axis of FIG. 3, “0 °” is the ignition timing that is MBT, and “20 °” on the vertical axis is the ignition timing that is advanced by 20 ° from the MBT by the crank angle, and is “−20 °”. Is the ignition timing retarded by 20 ° in crank angle from MBT.

  Here, “MBT” will be described with reference to FIG. The indicated torque of the internal combustion engine (the total torque that is the net torque output from the engine output shaft plus the internal friction loss) changes according to the ignition timing, and the ignition timing is moved from the retard limit value to the advance side. As a result, the indicated torque increases and then decreases. The vicinity of the apex of this torque characteristic curve (the intake charge efficiency KL and the engine speed NE are constant) is relatively flat, and the ignition timing immediately before reaching the flat portion when the ignition timing is moved to the advance side. Is called MBT (Minimum advance for Best Torque). MBT is a timing at which a large torque is obtained and knocking does not occur.

  Returning to FIG. 3, the description will be continued. As can be seen from the results of FIG. 3, when the ignition timing SA is moved to the advance side, the 50% combustion timing CA50 also moves to the advance side in the lower region in FIG. 3 (see auxiliary line A1). On the other hand, when the ignition timing SA is moved to the advance side, the 50% combustion timing tends to move to the retard side in the upper region in FIG. 3 (see auxiliary line A2). Thus, in the critical region (for example, region A3 in FIG. 3) including the boundary between the lines A1 and A2, the relationship between the ignition timing SA and the 50% combustion timing CA50 is reversed. That is, the ignition timing SA and the 50% combustion timing CA50 have a relationship that changes so as to take an extreme value on the way. Therefore, focusing on such characteristics, the ignition timing is controlled here. In FIG. 3, when the ignition timing SA is moved to the advance side, the region where the relationship in which the 50% combustion timing CA50 moves approximately proportionally to the advance side is established, and the relationship is not substantially established. A line B is drawn so as to divide the region.

  Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.

  FIG. 5 is a schematic configuration diagram showing an internal combustion engine 10 to which the ignition timing control device 1 for an internal combustion engine according to an embodiment of the present invention is applied. The internal combustion engine 10 shown in FIG. 1 generates power by burning a mixture of fuel and air in a combustion chamber 14 of a cylinder 13 formed in a cylinder block 12 and reciprocating a piston 16 in the cylinder 13. It is. The internal combustion engine 10 is preferably configured as a multi-cylinder engine, and the internal combustion engine 10 of the present embodiment is configured as a four-cylinder engine, for example. Here, the internal combustion engine 10 is mounted on a vehicle here.

  An intake port formed in the cylinder head of the internal combustion engine 10 and facing each combustion chamber 14 is connected to an intake pipe (including an intake manifold) 18. Further, the exhaust ports formed in the cylinder head and facing each combustion chamber 14 are connected to an exhaust pipe (including an exhaust manifold) 20 respectively. The cylinder head is provided with an intake valve Vi and an exhaust valve Ve for each combustion chamber 14. Each intake valve Vi opens and closes a corresponding intake port, and each exhaust valve Ve opens and closes a corresponding exhaust port. Each intake valve Vi and each exhaust valve Ve are operated by a variable valve mechanism, for example, a valve mechanism (not shown) having a variable valve timing function that makes the valve timing and phase angle variable. Furthermore, the internal combustion engine 10 has a number of spark plugs 22 corresponding to the number of cylinders, and the spark plugs 22 are disposed in the cylinder heads so as to face the corresponding combustion chambers 14.

  The intake pipe 18 is connected to the surge tank 24 as shown in FIG. An air supply line (intake pipe) is connected to the surge tank 24, and the air supply line is connected to an air intake port (not shown) via an air cleaner 26. A throttle valve (in this embodiment, an electronically controlled throttle valve) 28 and an air flow meter 30 are incorporated in the air supply line (between the surge tank 24 and the air cleaner 26). On the other hand, the exhaust pipe 20 is provided with a catalyst device. Here, as shown in FIG. 5, a front-stage catalyst device 32 including a three-way catalyst and a rear-stage catalyst device 34 including a NOx storage reduction catalyst are provided.

  Furthermore, the internal combustion engine 10 has a plurality of injectors 36, and each injector 36 is disposed so as to face a corresponding intake port, as shown in FIG. Each injector 36 injects fuel such as gasoline into each intake passage. In addition, although the internal combustion engine 10 of this embodiment is demonstrated as what is called a port injection type gasoline engine, this invention can be applied also to an internal combustion engine provided with another structure. For example, the present invention can be applied to a so-called direct injection internal combustion engine.

Each of the spark plugs 22, the throttle valve 28, the injectors 36, the valve operating mechanism and the like described above are electrically connected to an ECU 38 that substantially functions as control means for the internal combustion engine 10. The ECU 38 includes a CPU, a ROM, a RAM, an input / output port, an A / D and D / A converter, and a storage device, all not shown. As shown in FIG. 5, various sensors such as a crank angle sensor 40, an air flow meter 30, and an air-fuel ratio sensor (O ₂ sensor) 42 provided in the exhaust pipe 20 are electrically connected to the ECU 38. The ECU 38 uses each of the spark plugs 22, the throttle valve 28, and each of the throttle valves 28 so that a desired output can be obtained based on detection values obtained using various sensors and the like stored in the storage device. The injector 36, the valve mechanism and the like are controlled. Note that the calculation means and the ignition timing correction means each include a part of the ECU 38.

  Further, the internal combustion engine 10 has a number of in-cylinder pressure sensors 50 including semiconductor elements, piezoelectric elements, optical fiber detection elements, and the like corresponding to the number of cylinders. Each in-cylinder pressure sensor 50 is disposed on the cylinder head so that the pressure receiving surface faces the corresponding combustion chamber 14, and is electrically connected to the ECU 38. Each in-cylinder pressure sensor 50 gives a sensor output signal corresponding to the detected value to the ECU 38 so as to detect the in-cylinder pressure (for example, relative pressure) in the corresponding combustion chamber 14. Sensor output signals from the in-cylinder pressure sensors 50 are sequentially given to the ECU 38 at predetermined time intervals (predetermined crank angles) and converted into detection values that are absolute pressure values, for example, and then a predetermined storage area (buffer) of the ECU 38. Is stored and held by a predetermined amount. The in-cylinder pressure detection means includes an in-cylinder pressure sensor 50 as a detection unit and a part of the ECU 38 as a calculation unit.

  In the internal combustion engine 10 configured in this way, basically, the air-fuel ratio of air and fuel in each operating combustion chamber 14 is set to the theoretical air-fuel ratio (about 14.7). That is, the air-fuel ratio sensor 42 outputs a voltage corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust pipe 20 as a sensor output signal, and the ECU 38 takes into account the response delay of the air-fuel ratio sensor 42 and the like. Thus, the rich / lean determination of the air-fuel ratio in each combustion chamber 14 is performed based on the detection value of the air-fuel ratio sensor 42. When the ECU 38 determines that the air-fuel ratio in the combustion chamber 14 is larger (lean) than the stoichiometric air-fuel ratio based on the detection value obtained using the air-fuel ratio sensor 42, the ECU 38 follows a predetermined procedure. The fuel injection amount τ from the injector 36 is corrected to be increased. When the ECU 38 determines that the air-fuel ratio in the combustion chamber 14 is smaller (richer) than the stoichiometric air-fuel ratio based on the detection value obtained using the air-fuel ratio sensor 42, the ECU 38 follows a predetermined procedure. The fuel injection amount τ from the injector 36 is corrected to decrease.

  Further, such an internal combustion engine includes the valve operating mechanism for controlling the intake and exhaust valves Vi and Ve. Therefore, for example, when the engine is started or when the load is high, the valve overlap is eliminated. On the other hand, the valve overlap is increased when the engine operating state is in a steady state.

  Next, the ignition timing control procedure in the internal combustion engine 10 will be described with reference to FIG.

  In the internal combustion engine 10, the air-fuel ratio feedback control as described above is executed, and the ignition timing control routine of FIG. 6 is repeatedly executed for each combustion chamber 14. In FIG. 6, first, when the previously set ignition timing arrives, the ECU 38 outputs an ignition instruction to the ignition plug 22 in the target combustion chamber 14, thereby executing ignition (step S601).

  Next, the ECU 38 obtains the in-cylinder pressure value from the sensor output signal from the in-cylinder pressure sensor 50, and calculates the combustion ratio at a predetermined timing based on this (S603). The calculation of the combustion ratio is performed according to the following procedure. First, the ECU 38 reads the in-cylinder pressure from the predetermined storage area of the target combustion chamber 14 at the first timing (timing at which the crank angle becomes θ1) after the intake valve Vi is opened and before the combustion is started. P (θ1), in-cylinder pressure P (θ2) at the second timing (timing at which the crank angle becomes θ2) after ignition corresponding to the start of combustion and before the opening of the exhaust valve Ve, the first timing and the second The in-cylinder pressure P (θ0) at a predetermined timing at which the crank angle = θ0 (where θ1 <θ0 <θ2) is read out.

  The crank angle θ1 is preferably set to a timing sufficiently before the time point at which combustion starts in the combustion chamber 14 (at the time of ignition), for example, 60 ° (−60 °) before top dead center. The crank angle θ2 is preferably set to a timing at which the combustion of the air-fuel mixture in the combustion chamber 14 is substantially completed, and is set to 60 ° (60 °) after top dead center, for example. Further, the reference crank angle θ0 is set to 8 ° (8 °) after top dead center, which is experimentally and empirically known to have a combustion ratio MFB of 50%. Note that the timing at which the combustion ratio MFB becomes 50% is referred to as 50% combustion timing CA50 in the present specification as described above.

When the ECU 38 reads the in-cylinder pressure P (θ1), the in-cylinder pressure P (θ0), and the in-cylinder pressure P (θ2), the product value P (θ1) · V when the crank angles are θ1, θ0, and θ2. ^κ (θ1), P (θ0) · V ^κ (θ0) and P (θ2) · V ^κ (θ2) are calculated. That is, the ECU 38 determines the in-cylinder pressure P (θ1) and the in-cylinder pressure P (θ1), that is, the in-cylinder volume V (θ1) when the crank angle is θ1, the specific heat ratio κ (this embodiment). Then, the product value P (θ1) · V ^κ (θ1), which is the product of the value raised to the power of κ = 1.32), is calculated. Similarly, the ECU 38 calculates a product value P (θ0) · that is the product of the in-cylinder pressure P (θ0) and the value obtained by raising the in-cylinder volume V (θ0) when the crank angle becomes θ0 by the specific heat ratio κ. The product value P (θ2), which is the product of V ^κ (θ0), the in-cylinder pressure P (θ2), and the value obtained by raising the in-cylinder volume V (θ2) when the crank angle becomes θ2 by the specific heat ratio κ. ) · V ^κ (θ2) is calculated. The values of V ^κ (θ1), V ^κ (θ0), and V ^κ (θ2) are calculated in advance and stored in the storage device.

Then, the ECU 38 determines the product values P (θ1) · V ^κ (θ1), P (θ0) · V ^κ (θ0) and P (θ2) · V ^κ (θ2) when the crank angles are θ1, θ0, and θ2. ), The combustion ratio MFB at the timing when the crank angle becomes θ0 is calculated from the following equation (4). As a result, the combustion ratio MFB up to the reference crank angle θ0 can be accurately obtained based on the in-cylinder pressures P (θ1), P (θ0), and P (θ2) detected at the three points.

  Thus, when the combustion rate MFB is calculated in step S603, the ECU 38 determines whether the calculated combustion rate MFB is below a predetermined reference combustion rate (step S605). This reference combustion ratio is a combustion ratio corresponding to the reference crank angle θ0, and is 50% here.

  If the result of the determination in step S605 is affirmative, the ECU 38 sets the advance amount of the ignition timing according to a predetermined advance amount table or function (step S607), and the ignition timing according to the set advance amount. Is advanced (step S609). If the result of the determination in step S605 is negative, the ECU 38 sets the ignition timing retard amount in accordance with a predetermined retard amount table or function (step S611), and the ignition timing in accordance with the set retard amount. Is retarded (step S613). Through the above processing, the ignition timing is controlled so that the combustion ratio MFB matches the reference combustion ratio. In this ignition timing control, for example, a predetermined dead zone may be provided in the determination in step S605 in order to prevent control hunting.

  Note that such advance or retard of the ignition timing is performed by a reference step width per combustion cycle. Then, with the set advance amount or retard amount as a target, the ignition timing is shifted (corrected) by one step width per combustion cycle so as to approach the target.

  By the way, in such ignition timing control (ignition timing basic control), when the ignition timing is moved to the advance side, the 50% combustion timing CA50 is also moved to the advance side, whereas the ignition timing is retarded. This control is based on the premise that the relationship that the 50% combustion timing CA50 also moves to the retarded angle side is established. However, as described above with reference to FIG. 3, when the ignition timing SA is moved to the advance side, the 50% combustion timing CA50 is retarded from the case where the 50% combustion timing CA50 is also moved to the advance side. May move to the corner. In short, when the ignition timing SA is moved to the advance side, the ignition timing control fails in a region where the relationship in which the 50% combustion timing CA50 moves to the retard side is established. Therefore, here, in order to prevent this failure, paying attention to such characteristics, further correction is performed for the ignition timing control. This correction will be described based on the flowchart of FIG. However, the flowchart of FIG. 7 may be incorporated into the flowchart of FIG. 6 described above.

  The ECU 38 first reads the engine speed NE and the charging efficiency KL in step S701. Here, the phase angle IN of the intake valve Vi and the phase angle EX of the exhaust valve Ve may be further read.

  In step S703, it is determined whether or not the engine operating state is a predetermined operating state, here a steady state. However, the predetermined operation state is not limited to the steady state, and may be another state. For example, it may be determined whether or not the valve overlap amount is a predetermined amount or more, that is, whether or not the engine operation state is an operation state in which the valve overlap amount is a predetermined amount or more.

  If an affirmative determination is made in step S703, an evaluation value γ as a value representing the relationship between the ignition timing SA and the 50% combustion timing CA50 is calculated in the next step S705. The evaluation value γ is calculated based on the ignition timing SA and the 50% combustion timing CA50 in two combustion cycles, preferably two consecutive combustion cycles.

Here, first, the ignition timing SA ₀ in the most recent combustion cycle, preferably the current combustion cycle, is read, and 50% calculated based on data obtained as a result of ignition at this ignition timing SA _0. combustion timing CA50 ₀ is read. Then, the ignition timing SA ₁ for the obtained next combustion cycle the ignition timing SA ₀ by causing a predetermined angle delSA partial advance, thus obtained result of the ignition with the ignition timing SA ₁ obtained was 50% combustion timing CA50 ₁ which is calculated based on the data is read. Note that the 50% combustion timings CA50 ₀ and CA50 ₁ are calculated based on the detected in-cylinder pressure by, for example, calculating a graph as shown in FIG.

Then, by substituting these ignition timings SA ₀ , SA ₁ , 50% combustion timing CA50 ₀ , CA50 ₁ into the following equation (5), the relationship between the ignition timing SA and the 50% combustion timing CA50 is evaluated. An evaluation value γ is calculated. Incidentally, the evaluation value γ corresponds to the slope of a graph showing the relationship between the such ignition timing SA and 50% combustion timing CA50 shown in FIG.

  The evaluation value γ calculated in this way is stored in a predetermined storage area so as to learn and update mapped data (not shown). This data is a collection of evaluation values γ for the engine speed NE and the charging efficiency KL, and is configured as a collection of data for various conditions. In the initial stage, this data is constructed based on experiments and the like, and is updated with the subsequent operation (operation) of the internal combustion engine 10. Note that the phase angle IN of the intake valve Vi and the phase angle EX of the exhaust valve Ve may be associated with the data.

  The evaluation value γ calculated in step S705 is compared with the first threshold value α in step S707. Specifically, it is determined whether or not the evaluation value γ is greater than the first threshold value α and less than zero. If the determination is affirmative, the routine ends. On the other hand, if a negative determination is made in step S707, the evaluation value γ is compared with the second threshold value β in step S709. Specifically, it is determined whether or not the evaluation value γ is less than the second threshold value β or greater than or equal to zero. If an affirmative determination is made in step S709, a predetermined forced retard amount is set as an ignition timing correction amount in step S711, ignition timing correction is performed using the predetermined forced retard amount, and ignition is performed. On the other hand, if a negative determination is made in step S709, the width of the reference step is reduced (narrowed) in step S713.

  Here, further description will be made based on FIG. FIG. 8 is a graph showing an example of a relationship between the ignition timing SA on the horizontal axis and the evaluation value γ on the vertical axis. However, the vertical axis is positive on the upper side in the figure, and the horizontal axis is the angle before top dead center on the right side in the figure. In FIG. 8, the relationship corresponding to the relationship in which the 50% combustion timing CA50 moves to the advance side as the ignition timing SA moves to the advance side is represented by a line C1, and the ignition timing SA moves to the advance side. Accordingly, the relationship corresponding to the relationship in which the 50% combustion timing CA50 moves to the retarded angle side is represented by a line C2. In order to prevent the ignition timing control as described above from failing, it is desirable to maintain the relationship between the ignition timing SA and the evaluation value γ as indicated by the line C1. Therefore, here, when the evaluation value γ is greater than the first threshold value α and less than zero, that is, when an affirmative determination is made in step S707, the ignition timing control is continued as it is. The first threshold value α may be associated with the line B in FIG.

  On the other hand, when the evaluation value γ is less than the second threshold value β or greater than or equal to zero, that is, when an affirmative determination is made in step S709, the ignition timing cannot be continued as it is. The angle is delayed by the amount of forced retardation, and the evaluation value γ is forced to be a value that is less than zero and exceeds the first threshold value α (so as not to depart from a predetermined relational area). When the evaluation value γ is equal to or less than the first threshold value α and equal to or greater than the second threshold value β, that is, when a negative determination is made in step S709, the basic step width for ignition timing control is shortened. As a result, the evaluation value γ is suppressed so as not to be less than the second threshold value β or not to be greater than zero.

  If a negative determination is made in step S703 that the engine operating state is not a steady state, in step S715, based on the engine operating state, here, the engine rotational speed NE and the charging efficiency KL, from the data related to the evaluation value γ. The evaluation value γ is extracted (read). Then, step S707 and subsequent steps are performed using the extracted evaluation value γ.

  As described above, the relationship between the ignition timing SA and the 50% combustion timing CA50 is maintained such that the 50% combustion timing CA50 moves to the advance side as the ignition timing SA moves to the advance side (in this case) By performing the ignition timing control (without departing from the relationship), the combustion of the air-fuel mixture in the cylinder can be appropriately controlled.

  In the above embodiment, the ignition timing is controlled based on the combustion ratio MFB. However, the ignition timing is normally advanced so as not to cause knocking or the like, and is retarded when knocking or the like occurs. It may be controlled by doing so. With respect to such basic control of the ignition timing, the ignition timing SA and the 50% combustion timing that the 50% combustion timing CA50 moves to the advance side as the ignition timing SA moves to the advance side as described above. Correction control for maintaining the relationship with the CA50 can be adapted.

  In the above-described embodiment, the 50% combustion timing CA50 is used as the timing at which the combustion ratio becomes a predetermined amount in the combustion cycle, but 40% combustion timing, 60% combustion timing, or the like may be used as such timing. That is, the predetermined amount is not limited to 50% and can be set to various amounts.

  In addition, although the present invention has been described with a certain degree of specificity in the above-described embodiments and modifications thereof, the present invention is not limited to these, and the spirit and scope of the invention described in the scope of the claims. It should be understood that various modifications and changes can be made without leaving. That is, the present invention includes modifications and changes that fall within the scope and spirit of the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 Control apparatus 10 of internal combustion engine Internal combustion engine 14 Combustion chamber 22 Spark plug 36 Injector 38 ECU
40 Crank angle sensor 50 Cylinder pressure sensor Ve Exhaust valve Vi Intake valve

Claims (1)

A calculating means for calculating a value representing a relationship between a timing at which a predetermined combustion ratio in the combustion chamber is reached and an ignition timing;
An ignition timing control device for an internal combustion engine, comprising: an ignition timing correction unit that corrects the ignition timing so that the value calculated by the calculation unit does not deviate from a predetermined relational region.

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