JP4419975B2 - Control device for internal combustion engine - Google Patents

Description

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

  Conventionally, for example, JP-A-8-232752 discloses a method for determining the fluctuation limit of the indicated mean effective pressure using a value obtained by dividing the standard deviation of the indicated mean effective pressure by the average value of the indicated mean effective pressure. Has been.

JP-A-8-232752 Japanese Patent Laid-Open No. 11-107822 Japanese Patent Laid-Open No. 9-189281

  However, since the technique described in Japanese Patent Laid-Open No. 8-232752 discriminates the variation limit using the determination index calculated from the actual measurement value, the average shown in the figure until the determination index reaches the variation limit. There is a problem that it cannot be determined whether or not the effective pressure has reached a limit value. For this reason, in the determination, the indicated mean effective pressure actually reaches the fluctuation limit value, resulting in a problem that the drivability deteriorates.

  In addition, since the method described in Japanese Patent Laid-Open No. 8-232752 uses the indicated mean effective pressure as a determination index, it is determined whether or not the shaft torque actually output from the internal combustion engine has reached the fluctuation limit. There is a problem that can not be.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain the most retarded ignition timing within an allowable range of torque fluctuation without deteriorating drivability.

In order to achieve the above object, the first invention provides a cylinder pressure acquisition means for acquiring a cylinder pressure, a combustion ratio calculation means for calculating a combustion ratio based on the cylinder pressure, and a cylinder pressure based on the cylinder pressure. Illustrated torque calculating means for calculating the indicated torque, crank angle position calculating means for calculating the crank angle position at which the combustion ratio becomes a predetermined value, and combustion ratio crank angle position distribution calculation for calculating the distribution of the crank angle position in a plurality of cycles Means, calculated torque distribution calculating means for calculating the distribution of the indicated torque in the plurality of cycles, combustion rate crank angle position distribution estimating means for estimating the distribution of the crank angle position when the ignition timing is retarded, The indicated torque for estimating the indicated torque distribution when the ignition timing is retarded based on the indicated torque distribution and the estimated distribution of the crank angle position. Cloth estimation means, based on the distribution of the indicated torque, an ignition timing calculation means torque fluctuation of the internal combustion engine obtains the ignition timing is retarded under conditions of a predetermined range, which is calculated by said ignition timing calculation means And ignition timing retard control execution means for executing ignition timing retard control based on the ignition timing .
In a second aspect based on the first aspect, the ignition timing calculation means calculates the ignition timing that is most retarded under the condition that the torque fluctuation of the internal combustion engine falls within the predetermined range based on the distribution of the indicated torque. It is characterized by seeking.

According to a third invention, in the first or second invention, the combustion ratio crank angle position distribution estimating unit divides a standard deviation representing the distribution of the crank angle position by a value including an average value of the crank angle position. The distribution of the crank angle position when the ignition timing is retarded is estimated based on the fact that the value becomes a substantially constant value regardless of the ignition timing.

In a fourth aspect based on any one of the first to third aspects , the indicated torque distribution estimating means is a value obtained by dividing a standard deviation representing the distribution of the crank angle position by a standard deviation representing the distribution of the indicated torque. The distribution of the indicated torque when the ignition timing is retarded is estimated using a mathematical formula or a map that defines the relationship between the ignition timing and the ignition timing.

In a fifth aspect based on the fourth aspect , the mathematical expression or the map represents a relationship between an ignition timing and a value obtained by dividing a standard deviation representing the distribution of the crank angle position by a standard deviation representing the distribution of the indicated torque. It is defined by a linear function.

A sixth invention is characterized in that, in the fourth or fifth invention, a correction means for correcting the mathematical expression or the map in accordance with an aging change or a machine difference of the internal combustion engine is further provided.

According to a seventh invention, in any one of the first to sixth inventions, there is further provided a shaft torque distribution calculating means for calculating a shaft torque distribution of the crankshaft of the internal combustion engine based on the estimated distribution of the indicated torque. The ignition timing calculation means obtains an ignition timing retarded under the condition that the torque fluctuation of the internal combustion engine falls within a predetermined range based on the distribution of the shaft torque calculated from the distribution of the indicated torque. And

According to an eighth invention, in any one of the first to seventh inventions, the combustion rate crank angle position distribution estimating means is configured such that the smaller the distribution of the indicated torque calculated by the indicated torque distribution calculating means, The retard amount of the ignition timing when estimating the distribution of the crank angle position is increased.

According to the first invention, since the distribution of the indicated torque when the ignition timing is retarded can be estimated, the ignition timing that can be retarded within a range in which the torque fluctuation becomes an allowable level is obtained by model calculation. Can be sought. Therefore, it is possible to retard the ignition timing while maintaining good drivability, and it is possible to warm up the catalyst at the time of startup in a short time.
According to the second invention, since the distribution of the indicated torque when the ignition timing is retarded can be estimated, the ignition timing that can be most retarded within a range where the torque fluctuation is within the allowable level is calculated by model calculation. It can ask for. Accordingly, the ignition timing can be most retarded while maintaining good drivability, and the catalyst can be warmed up in a short time.

According to the third invention, the value obtained by dividing the standard deviation representing the distribution of the crank angle position at which the combustion ratio becomes a predetermined value by the value including the average value of the crank angle position is a substantially constant value regardless of the ignition timing. Therefore, it is possible to estimate the crank angle position distribution when the ignition timing is retarded.

According to the fourth aspect of the present invention, a mathematical formula or a map that prescribes the relationship between the value obtained by dividing the standard deviation representing the distribution of the crank angle position by the standard deviation representing the distribution of the indicated torque and the ignition timing is constructed in advance. Thus, it is possible to estimate the distribution of the indicated torque when the ignition timing is retarded.

According to the fifth invention, since the relationship between the standard deviation representing the distribution of the crank angle position divided by the standard deviation representing the distribution of the indicated torque and the ignition timing is defined by the linear function, the mathematical formula or the map is simplified. Can be built.

According to the sixth invention, since the mathematical formula or the map is corrected according to the secular change or machine difference of the internal combustion engine, the distribution of the indicated torque when the ignition timing is retarded can be estimated with high accuracy. Become.

According to the seventh aspect of the invention, since the ignition timing is obtained based on the distribution of the shaft torque of the crankshaft of the internal combustion engine, it is possible to perform ignition timing retardation control with higher accuracy in consideration of drivability. It becomes.

According to the eighth aspect of the invention, as the indicated torque distribution is smaller, the amount of processing until the ignition timing is set to the target value in order to increase the retard amount of the ignition timing when estimating the crank angle position distribution. Can be reduced.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram for explaining a control device for an internal combustion engine according to a first embodiment of the present invention and a structure around the control device. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. The intake passage 12 includes an air filter 16 at an upstream end. The air filter 16 is assembled with an intake air temperature sensor 18 for detecting the intake air temperature THA (ie, the outside air temperature). An exhaust purification catalyst 31 is provided in the exhaust passage 14.

  An air flow meter 20 is disposed downstream of the air filter 16. The air flow meter 20 is a sensor that detects an intake air amount Ga flowing through the intake passage 12. A throttle valve 22 is provided downstream of the air flow meter 20. A throttle sensor 24 that detects the throttle opening degree TA and an idle switch 26 that is turned on when the throttle valve 22 is fully closed are disposed in the vicinity of the throttle valve 22.

  A surge tank 28 is provided downstream of the throttle valve 22. Further, a fuel injection valve 30 for injecting fuel into the intake port of the internal combustion engine 10 is disposed further downstream of the surge tank 28.

  Each cylinder of the internal combustion engine 10 includes a cylinder 32, a piston 34, and a spark plug 35. A crankshaft 36 that is rotationally driven by the reciprocating motion is connected to the piston 34. The vehicle drive system and accessories (air conditioner compressor, alternator, torque converter, power steering pump, etc.) are driven by the rotational torque of the crankshaft 36. A crank angle sensor 38 for detecting the rotation angle (engine speed) of the crankshaft 36 is attached in the vicinity of the crankshaft 36. The internal combustion engine 10 is provided with an in-cylinder pressure sensor 44 for detecting the in-cylinder pressure (in-cylinder pressure).

  Members constituting the internal combustion engine 10 such as the cylinder 32 and the piston 34 are cooled by cooling water flowing around. A water temperature sensor 42 for detecting the cooling water temperature THW is attached to the cylinder block of the internal combustion engine 10.

  As shown in FIG. 1, the fuel control apparatus of the present embodiment includes an ECU (Electronic Control Unit) 40. In addition to the various sensors described above, the ECU 40 includes an atmospheric pressure sensor that detects atmospheric pressure, a KCS sensor that detects the occurrence of knocking, and various sensors that detect vehicle speed, exhaust temperature, lubricating oil temperature, catalyst bed temperature, and the like. (Not shown) is connected. The ECU 40 is connected to each actuator such as the fuel injection valve 30 and the spark plug 35 described above.

  In the system of the present embodiment configured as described above, the catalyst is warmed up by retarding the ignition timing under conditions where the temperature of the exhaust purification catalyst 31 does not reach the activation temperature, such as during cold start. According to the control for retarding the ignition timing, the gas sent to the cylinder 32 can be combusted on the catalyst side, so that the exhaust purification catalyst 31 can be warmed up early. Therefore, it is possible to improve the emission of exhaust gas when starting the engine.

  On the other hand, if the ignition timing is retarded excessively, the variation in torque fluctuation of the crankshaft 36 increases, and drivability may deteriorate. For this reason, in this embodiment, control is performed so that the ignition timing is most retarded in a state where torque fluctuation is suppressed. As a result, it is possible to maintain good drivability and warm up the exhaust purification catalyst 31 at an early stage.

  At this time, in the present embodiment, an optimal ignition timing that does not deteriorate drivability is calculated by model calculation, and based on this, control is performed to retard the actual ignition timing. According to such a method, since it is not necessary to observe the torque fluctuation after actually changing the ignition timing, it can be avoided that the actual ignition timing is set to a state exceeding the allowable range of the torque fluctuation, Deterioration of drivability can be reliably suppressed. Accordingly, it is possible to set the ignition timing at which the catalyst warm-up effect can be quickly enhanced while ensuring the stability of torque variation.

  Hereinafter, processing in the system of the present embodiment will be described based on the flowchart of FIG. The process in FIG. 2 is repeatedly executed at predetermined time intervals. First, in step S1, the state of a flag indicating the operation mode is read. If flag = 1, the process proceeds to step S2. On the other hand, if flag = 0, the process proceeds to step S3.

  Here, flag represents the current operation mode, and flag = 1 is set when operation is performed in the ignition timing retardation correction mode according to the method of the present embodiment. On the other hand, flag = 0 is set when ignition timing retardation correction is not performed, such as during normal travel.

  In step S3, the cycle count number cyc in the ignition timing retard correction mode is set to 0 (cyc = 0). After step S3, the process proceeds to step S2.

  In step S2, operating conditions such as the current engine speed Ne, load KL, and intake air amount Ga of the internal combustion engine 10 are measured and stored. In the next step S4, it is determined whether or not the current operating state is a steady state by comparing the operating state of the current cycle and the previous cycle based on the operating state measured in step S2.

  If it is determined in step S4 that the current operating state is a steady state, the process proceeds to step S5. In step S5, a flag flag indicating the operation mode is set to 1 (flag = 1). On the other hand, if it is determined in step S4 that the current operation state is not a steady state, that is, if the current operation state is determined to be a transient operation state, the ignition timing retardation correction is not performed, and thus the process proceeds to step S17. Go ahead and set flag = 0. Then, after step S17, the process ends (RETURN).

  After step S5, the process proceeds to step S6. In step S6, a process of adding 1 to the current cycle count cyc is performed (cyc = cyc + 1). In the next step S7, in-cylinder pressure is measured by the in-cylinder pressure sensor 44 in the current cycle (cyc + 1). At this time, when the internal combustion engine 10 is a four-cylinder engine, the in-cylinder pressure is measured in a section where the crank angle of the compression stroke and the expansion stroke is 360 °.

  In the next step S8, the 50% combustion point (BP) [CA] and the indicated torque ITQ in the current cycle are calculated based on the in-cylinder pressure measured in step S7. FIG. 3 is a schematic diagram showing the 50% combustion point [CA], and the horizontal axis shows the crank angle. The vertical axis represents the ratio of the amount of heat generated up to an arbitrary crank angle (combustion ratio) with respect to the total amount of heat generated in the current cycle.

As shown in FIG. 3, when ignition is performed at the crank angle θ ₀ , the combustion rate increases as the crank angle advances. The 50% combustion point [CA] represents the crank angle at which the combustion ratio becomes 50%. The 50% combustion point [CA] can be calculated from the following equations (1) and (2).

Equation (1) is an energy conservation law that is established between the in-cylinder pressure P, the in-cylinder volume V, and the heat generation amount (cumulative heating rate) Q. In the formula (1), κ is a specific heat ratio. Further, the in-cylinder volume V and the rate of change dV / dθ are values determined geometrically according to the crank angle θ. Θ ₀ is the crank angle at which ignition was performed, and P is the in-cylinder pressure detected by the in-cylinder pressure sensor 44. Therefore, the calorific value Q generated from the crank angle θ ₀ to an arbitrary crank angle EVO can be calculated by calculating the integral value according to the equation (1).

  According to the equation (1), the maximum value Qmax of the heat generation amount Q can be obtained by sequentially calculating the heat generation amount Q at an arbitrary crank angle EVO. The crank angle EVO at which the heat quantity Q that is 50% of Qmax is generated becomes the 50% combustion point [CA]. The calorific value Q of 50% of Qmax is calculated by setting the combustion ratio xb = 50 [%] in the equation (2).

  The indicated torque ITQ in the current cycle can be calculated from the following formulas (3) and (4). The expression (3) is an expression for calculating the work amount W in the section of the crank angle 360 ° in the compression stroke and the expansion stroke based on the in-cylinder pressure P. Further, the expression (4) is an expression for calculating the indicated torque ITQ based on the work amount W. In the equation (4), Nc represents the number of cylinders.

  The values of the 50% combustion point [CA] and the indicated torque ITQ obtained in this way are stored in a memory in the ECU 40, for example.

  In the next step S9, it is determined whether or not the cycle count number cyc of the current cycle is 100 or more. That is, it is determined here whether cyc ≧ 100. In the case of cyc ≧ 100, acquisition of data for 100 cycles of the 50% combustion point [CA] and the indicated torque ITQ is completed, and the process proceeds to step S10. Here, the determination value 100 of the cycle count number cyc is a cycle number for calculating the 50% combustion point [CA] and the standard deviations σ50 and σITQ of the indicated torque ITQ, but the determination value of the cycle count number is other than 100. You may set to the value of. On the other hand, if cyc <100 in step S9, data for 100 cycles of the 50% combustion point [CA] and the indicated torque ITQ has not been acquired, and the processing of the current routine is terminated (RETURN). In this case, in step S6 of the next routine, 1 is added to the cycle count number cyc, and the calculation of the 50% combustion point [CA] and the indicated torque ITQ in the next cycle is continued.

  When the process proceeds to step S10, the average value μ50 and standard deviation σ50 of the 50% combustion point [CA] and the indicated torque ITQ based on the data for 100 cycles of the 50% combustion point [CA] and the indicated torque ITQ. The standard deviation σITQ is calculated. Here, the standard deviations σ50 and σITQ can be calculated from the following equation (5).

  In equation (5), the standard deviation σ50 is obtained by substituting the data for 100 cycles of the 50% combustion point [CA] into the value of x. Also, the standard deviation σITQ is obtained by substituting the data for 100 cycles of the indicated torque ITQ into the value of x. In the equation (5), cyc = 100.

  In the next step S11, the ignition timing SAr is set to the current ignition timing. That is, here, the ignition timing when the data for 100 cycles of the 50% combustion point [CA] and the indicated torque ITQ is acquired in the routine of steps S5 to S9 is set to SAr.

  In the next step S12, a process for retarding the ignition timing SAr by 2 ° is performed. That is, here, a process of adding 2 ° to the current ignition timing SAr set in step S11 is performed (SAr = SAr + 2).

  In the next step S13, the standard deviation σ50r of the 50% combustion point [CA] is calculated at the ignition timing SAr set in step S12. Here, a method for calculating the standard deviation σ50r will be described in detail with reference to FIGS. 4, 5, and 6. FIG.

  FIG. 4 is a characteristic diagram showing the relationship between the ignition timing and the indicated torque. In FIG. 4, the horizontal axis indicates the ignition timing [ATDC] with the compression top dead center as a reference. That is, as the ignition timing value on the horizontal axis increases, the ignition timing is retarded. As shown in the characteristics of FIG. 4, the value of the indicated torque decreases as the ignition timing is retarded.

  The ignition timing θ1 shown in FIG. 4 indicates the ignition timing SAr set in step S11. In the routine of steps S5 to S9, 50% combustion point [CA] and data for 100 cycles of the indicated torque ITQ are obtained. The ignition timing SAr at the time of acquisition is shown. Further, the ignition timing θ2 shown in FIG. 4 indicates the ignition timing SAr set in step S12, and is a value obtained by retarding the ignition timing SAr set in step S11 by 2 °.

  A distribution A2 of small coordinates A1 shown in FIG. 4 represents the distribution of data for 100 cycles of the 50% combustion point [CA] acquired in the routine of steps S5 to S9 and the indicated torque ITQ. Thus, the 100 data of the 50% combustion point [CA] acquired in the routine of steps S5 to S9 is distributed with the standard deviation σ50 around the average value μ50. In addition, 100 pieces of data of the indicated torque ITQ acquired in the routine of steps S5 to S9 are distributed with the standard deviation σITQ. The 50% combustion point [CA] represented by the distribution A2 of the small coordinates A1 and the distribution of the indicated torque ITQ are values already calculated in step S10.

  On the other hand, the distribution B2 of the small coordinate B1 shown in FIG. 4 shows the distribution of the data of the 50% combustion point [CA] at the ignition timing SAr set in step S12 and retarded by 2 °, and the indicated torque ITQ. Yes. Here, the standard deviation σ50r is the standard deviation of the 50% combustion point [CA] in the distribution B2 of the small coordinate B1, and the average value μ50r is the average value of the 50% combustion point [CA] in the distribution B2 of the small coordinate B1. . The standard deviation σITQr is a standard deviation of the indicated torque ITQr in the distribution B2 of the small coordinates B1.

  In step S13, the standard deviation σ50r of the 50% combustion point [CA] in the distribution B2 of small coordinates B1 obtained by retarding the ignition timing by 2 ° based on the standard deviation σ50 and standard deviation σITQ in the distribution A2 of small coordinates A1. The process which estimates is performed. Hereinafter, a method for estimating the standard deviation σ50r of the 50% combustion point [CA] after retarding the ignition timing by 2 ° will be described in detail.

  FIG. 5 is a characteristic diagram showing the relationship between the standard deviation σ50 of the 50% combustion point [CA] and the ignition timing. As described above, the 50% combustion point [CA] is a crank angle at which the combustion ratio is 50%. As shown in FIG. 5, the value of the standard deviation σ50 of the 50% combustion point [CA] changes according to the ignition timing, and the value of the standard deviation σ50 increases as the ignition timing is retarded. That is, as the ignition timing is retarded, the variation in the value of the 50% combustion point [CA] increases.

  On the other hand, FIG. 6 is a characteristic diagram showing the relationship between the ignition timing and the value obtained by dividing the standard deviation σ50 of the 50% combustion point [CA] by the average value μ50 + C. Thus, in the relationship between the standard deviation σ50 / (average value μ50 + C) and the ignition timing, the value of the standard deviation σ / (average value μ50 + C) is kept constant even when the ignition timing changes. It is. That is, in the relationship between σ50 / (μ50 + C) and the ignition timing, a characteristic that the sensitivity of the ignition timing is lost is obtained. Therefore, according to the characteristics of FIG. 6, the standard deviation σ50 / (average value μ50 + C) in the distribution A2 of the small coordinate A1 is equal to the standard deviation σ50r / (average value μ50r + C) in the distribution B2 of the small coordinate B1. Become. The constant C is a value identified for each internal combustion engine 10. Accordingly, the relationship of the following expression (6) is established.

  Further, the value of the average value μ50 of the 50% combustion point [CA] changes by the retard amount when the ignition timing is retarded. That is, the difference between the average value μ50 of the 50% combustion point [CA] in the distribution A2 of the small coordinate A1 and the average value μ50r of the 50% combustion point [CA] in the distribution B2 of the small coordinate B1 is retarded by 2 °. It corresponds to. Accordingly, the relationship of the following expression (7) is established.

  When the equations (6) and (7) are solved for σ50r, the following equation (8) is obtained. In the equation (8), each term on the right side is a known value. Accordingly, in step S13, the standard deviation σ50r of the 50% combustion point [CA] at the ignition timing SAr retarded by 2 ° set in step S12 can be calculated based on the equation (8).

  After step S13, the process proceeds to step S14. In step S14, the standard deviation σITQr of the indicated torque ITQr in the distribution B2 of the small coordinates B1 is calculated based on the standard deviation σ50r calculated in step S13. Hereinafter, a method for calculating the standard deviation σITQr based on the standard deviation σ50r will be described in detail.

  The standard deviation σITQr is a distribution of the indicated torque ITQr in the distribution B2 of the small coordinates B2 in FIG. Here, the inventors obtained a value (= σITQ / σ50) obtained by dividing the standard deviation σITQ of the indicated torque by the standard deviation σ50 of the 50% combustion point [CA] at an arbitrary ignition timing of the characteristic curve of FIG. It was found that the slope of the characteristic curve of FIG. That is, in the distribution B2 of the small coordinate B1 in FIG. 4, the value of σITQr / σ50r matches the slope of the characteristic curve at the ignition timing SAr (= θ2) (Δindicated torque / Δignition timing).

  Further, the characteristic curve of FIG. 4 can be approximated by a quadratic function. Therefore, as shown in FIG. 7, the relationship between σITQ / σ50 and the ignition timing can be expressed by a linear function, and can be expressed by the following equation (9). Further, when the formula (9) is modified, the following formula (10) is obtained.

  In the equations (9) and (10), the values of the coefficients a and b are values determined according to the engine speed Ne and the load KL, and are values acquired in advance.

  Accordingly, in step S14, the standard deviation σITQr of the indicated torque ITQr can be calculated from the standard deviation σ50r of the 50% combustion point [CA] calculated in step S13 based on the characteristic of FIG. 7 (equation (10)). It becomes possible.

  After step S14, the process proceeds to step S15. In step S15, the value of the standard deviation σITQr calculated in step S14 is compared with a predetermined threshold value thr to determine whether or not σITQr> thr.

  If σITQr> thr in step S15, the process proceeds to step S16. In this case, since the standard deviation σITQr of the indicated torque ITQr at the ignition timing SAr set in step S12 exceeds the predetermined threshold value thr, it is assumed that the fluctuation of the indicated torque ITQr is large and the drivability is deteriorated. it can. Accordingly, in step S16, a process of subtracting 2 ° from the currently set ignition timing SAr is performed (SAr = SAr-2).

  After step S16, the process proceeds to step S17. In step S17, a flag indicating the operation mode is set to 0 (flag = 0). After step S17, the process ends (RETURN).

  On the other hand, if σITQr ≦ thr in step S15, the process returns to step S12. In this case, since the standard deviation σITQr of the indicated torque ITQr has not reached the predetermined threshold value thr, the ignition timing can be further retarded to the fluctuation limit of the indicated torque. Accordingly, a process for further retarding the ignition timing is performed by the processes after step S12.

  According to the process of FIG. 2, the ignition timing SAr can be retarded most within a range in which the standard deviation σITQr of the indicated torque does not reach the predetermined fluctuation limit (threshold value thr). Therefore, it is not necessary to actually change the ignition timing and observe the torque fluctuation of the internal combustion engine 10, and while delaying the ignition timing, the catalyst warm-up effect can be increased quickly while ensuring the stability of the torque variation. It becomes possible. As a result, the ignition timing can be most retarded to the torque fluctuation limit point with good drivability, and the catalyst can be warmed up in a short time.

  As described above, according to the first embodiment, the ignition timing at which the indicated torque value becomes the fluctuation limit point of torque fluctuation can be calculated by model calculation. Therefore, when the catalyst is warmed up, the ignition timing can be most retarded while maintaining good drivability. This makes it possible to warm up the catalyst early without deteriorating drivability.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. In the first embodiment, the ignition timing is retarded so that the standard deviation σITQr of the indicated torque is less than the predetermined threshold value thr. However, drivability directly affects the influence of the shaft torque generated by the crankshaft 46. Therefore, it is more preferable to determine the ignition timing based on the shaft torque of the crankshaft 46.

  Therefore, in the second embodiment, the standard deviation σBTQr of the shaft torque BTQr generated by the crankshaft 46 is calculated based on the standard deviation σITQr of the indicated torque σITQr calculated in the first embodiment, and based on this, the ignition timing is calculated. The amount of retardation is determined.

  FIG. 8 is a characteristic diagram showing the relationship between the standard deviation σITQr of the indicated torque and the standard deviation σBTQr of the shaft torque. As shown in FIG. 8, the standard deviation σBTQr of the shaft torque increases as the standard deviation σITQr of the indicated torque increases.

  Further, as shown in FIG. 8, the relationship between the standard deviation σITQr of the indicated torque and the standard deviation σBTQr of the shaft torque changes according to the engine speed Ne, and the value of the standard deviation σITQr of the indicated torque is the same. However, the value of the standard deviation σBTQr of the shaft torque decreases as the engine speed increases. This is because as the engine speed Ne increases, the value of the standard deviation σBTQr decreases with respect to the standard deviation σITQr due to the influence of rotational inertia.

  In the second embodiment, the standard deviation σITQr of the indicated torque is calculated by the method of the first embodiment, and the standard deviation σBTQr of the shaft torque is calculated based on the characteristics of FIG. Then, control is performed to retard the ignition timing so that the standard deviation σBTQr of the shaft torque is less than a predetermined threshold value.

  As a result, the ignition timing can be retarded based on the standard deviation σBTQr of the shaft torque that directly affects vehicle vibration, and the ignition timing can be more accurately retarded to the limit point of torque fluctuation. .

  As described above, according to the second embodiment, the standard deviation σBTQr of the shaft torque is calculated from the standard deviation σITQr of the indicated torque, and the ignition timing is retarded based on the standard deviation σBTQr of the shaft torque. It becomes possible to perform the ignition timing retardation control with higher accuracy in consideration of drivability.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described. In the third embodiment, the map of FIG. 7 described in the first embodiment is updated as needed at a predetermined timing.

  As described in the first embodiment, in the equations (9) and (10) of the linear functions representing the map of FIG. 7, the values of the coefficients a and b are set according to the engine speed NE and the load KL. . Here, the values of the coefficients a and b fluctuate due to aging of the internal combustion engine 10, machine difference variation, and the like.

  Therefore, in the third embodiment, the values of the coefficients a and b are updated at a predetermined timing, and the process of updating the map in FIG. 7 to the latest map according to the state of the internal combustion engine 10 is performed. Specifically, based on the measurement result of the in-cylinder pressure, the data of σ50 and σITQ are acquired by changing the ignition timing SAr, the engine speed NE, and the load KL, and based on these data, the map (coefficient of FIG. A process of updating the values of a and b) is performed. The map update timing is performed, for example, every time the vehicle travel distance reaches a predetermined distance.

  As a result, the standard deviation σITQr of the indicated torque can be calculated using the latest map in consideration of aging, machine difference variation, and the like. Therefore, it is possible to control the ignition timing according to the standard deviation σITQr with high accuracy.

  As described above, according to the third embodiment, the map for calculating the standard deviation σITQr, which serves as an index of the torque fluctuation limit, is updated in accordance with the secular change of the internal combustion engine 10 and the machine difference variation. It is possible to perform ignition angle retardation control based on σITQr with high accuracy.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, when the ignition timing is retarded by the method of the first embodiment, if the currently set ignition timing is far from the ignition timing at the torque fluctuation limit, the ignition timing manipulated variable is increased. To do.

  As described with reference to FIG. 2 of the first embodiment, the ignition timing retardation is determined by setting the ignition timing manipulated variable (ΔSAr) to 2 under the condition that the standard deviation σITQr of the indicated torque is less than the predetermined threshold value thr. (Step S12 in FIG. 2) is performed by retarding the crank angle. In this case, the ignition timing at which data for 100 cycles of the 50% combustion point [CA] and the indicated torque ITQ is acquired in the routine of steps S5 to S9 in FIG. 2 is, for example, in the vicinity of the MBT ignition timing in FIG. In some cases, it is necessary to perform retardation control every 2 ° several times until the ignition timing of the torque fluctuation limit is calculated, and it is assumed that the amount of calculation processing increases.

  For this reason, in the fourth embodiment, control for varying the ignition timing manipulated variable ΔSAr is performed based on the standard deviation σITQr of the indicated torque. FIG. 9 is a map showing the relationship between the standard deviation σITQr of the indicated torque and the manipulated variable ΔSAr of the ignition timing. As shown in FIG. 9, the control is performed so that the ignition timing manipulated variable ΔSAr increases as the indicated torque standard deviation σITQr decreases.

  When the standard deviation σITQr of the indicated torque is small, it is considered that the deviation of the torque fluctuation limit from the ignition timing is large, so that the operation amount ΔSAr of the ignition timing can be increased. Therefore, when the standard deviation σITQr of the indicated torque is small and the retard amount until the ignition timing of the torque fluctuation limit is large, the ignition timing is set to a large value until the ignition timing reaches the torque fluctuation limit. It is possible to reduce the amount of processing. Therefore, the ignition timing retarding control to the torque fluctuation limit can be performed in a short time.

  As described above, according to the fourth embodiment, since the manipulated variable ΔSAr of the ignition timing is made variable according to the value of the standard deviation σITQr of the indicated torque, the amount of processing until the ignition timing is set to the target value is reduced. It becomes possible to reduce.

It is a figure for demonstrating the structure of the control apparatus of the internal combustion engine concerning Embodiment 1 of this invention, and its periphery. 3 is a flowchart illustrating a processing procedure in the system according to the first embodiment. It is a schematic diagram showing 50% combustion point [CA]. FIG. 6 is a characteristic diagram showing the relationship between ignition timing and indicated torque. It is a characteristic figure showing the relation between standard deviation σ50 of 50% combustion point [CA] and ignition timing. It is a characteristic figure showing the relation between the value which divided standard deviation σ50 of 50% combustion point [CA] by μ50 + C, and ignition timing. It is a schematic diagram which shows the map showing the relationship between (sigma) ITQ / (sigma) 50 and ignition timing. FIG. 6 is a characteristic diagram showing a relationship between a standard deviation σITQr of indicated torque and a standard deviation σBTQr of shaft torque. FIG. 6 is a schematic diagram showing a map showing a relationship between a standard deviation σITQr of indicated torque and an operation amount ΔSAr of ignition timing.

Explanation of symbols

40 ECU
44 In-cylinder pressure sensor

Claims (8)

In-cylinder pressure acquisition means for acquiring in-cylinder pressure;
A combustion rate calculating means for calculating a combustion rate based on the in-cylinder pressure;
An indicated torque calculating means for calculating an indicated torque based on the in-cylinder pressure;
Crank angle position calculating means for calculating a crank angle position at which the combustion ratio becomes a predetermined value;
Combustion rate crank angle position distribution calculating means for calculating distribution of the crank angle position in a plurality of cycles;
Illustrated torque distribution calculating means for calculating the distribution of the indicated torque in the plurality of cycles;
Combustion rate crank angle position distribution estimating means for estimating the distribution of the crank angle position when the ignition timing is retarded;
Based on the distribution of the indicated torque and the estimated distribution of the crank angle position, the indicated torque distribution estimating means for estimating the distribution of the indicated torque when the ignition timing is retarded;
Ignition timing calculation means for obtaining an ignition timing retarded under the condition that the torque fluctuation of the internal combustion engine falls within a predetermined range based on the distribution of the indicated torque;
Ignition timing retardation control execution means for executing ignition timing retardation control based on the ignition timing calculated by the ignition timing calculation means;
A control apparatus for an internal combustion engine, comprising: 2. The internal combustion engine according to claim 1, wherein the ignition timing calculation means obtains an ignition timing that is most retarded under a condition in which a torque fluctuation of the internal combustion engine falls within the predetermined range, based on the distribution of the indicated torque. Engine control device. The combustion ratio crank angle position distribution estimation means is based on the fact that a value obtained by dividing a standard deviation representing the distribution of the crank angle position by a value including an average value of the crank angle position becomes a substantially constant value regardless of the ignition timing. The control apparatus for an internal combustion engine according to claim 1 or 2 , wherein a distribution of the crank angle position when the ignition timing is retarded is estimated. The indicated torque distribution estimating means uses an equation or map that defines the relationship between the standard deviation representing the distribution of the crank angle position divided by the standard deviation representing the distribution of the indicated torque and the ignition timing, and The control device for an internal combustion engine according to any one of claims 1 to 3, wherein a distribution of the indicated torque when the timing is retarded is estimated. The mathematical expression or the map is defined by a linear function that defines a relationship between a value obtained by dividing a standard deviation representing the distribution of the crank angle position by a standard deviation representing the distribution of the indicated torque and an ignition timing. The control apparatus for an internal combustion engine according to claim 4 . Control apparatus for an internal combustion engine according to claim 4 or 5 further characterized in that said formula or map further comprising a correction means for correcting in accordance with the aging or instrumental error of the internal combustion engine. Shaft torque distribution calculating means for calculating the distribution of the shaft torque of the crankshaft of the internal combustion engine based on the estimated distribution of the indicated torque,
The ignition timing calculation means obtains an ignition timing retarded under a condition in which the torque fluctuation of the internal combustion engine falls within a predetermined range based on the distribution of the shaft torque calculated from the distribution of the indicated torque. The control device for an internal combustion engine according to any one of claims 1 to 6 . The combustion rate crank angle position distribution estimating means increases the retard amount of the ignition timing when estimating the crank angle position distribution as the indicated torque distribution calculated by the indicated torque distribution calculating means is smaller. The control device for an internal combustion engine according to any one of claims 1 to 7 , wherein:

Images