JP2014137020A - Control device and control method of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further suppress unburned HC during an ignition timing lag operation after a cold start.SOLUTION: A standard deviation σI20 of a crank angle position at which an ion current generating rate per cycle is 20% is obtained for previous 16 times of combustion (S7). If this standard deviation σI20 is smaller than a predetermined threshold σI20 th (S8), then the combustion of an internal combustion engine 1 is regarded as stable, and a lag increment R1 of ignition timing ADV gradually increases (S9). If the standard deviation σI20 is equal to or larger than the threshold σI20 th, then the combustion is regarded as unstable, and the lag increment R1 gradually decreases (S11). Therefore, the ignition timing ADV lags up to a maximum and an exhaust temperature rises up to a maximum in a range in which a combustion stable state nears a limit.

Description

  The present invention relates to a control device and a control method for an internal combustion engine that retards an ignition timing after start-up of a cold engine and promotes warm-up of an exhaust system catalyst device.

  It is known to perform an operation in which the ignition timing is retarded so that the catalyst in the exhaust system catalytic device is activated early after the internal combustion engine is cold-started. The ignition timing retard amount during such retard operation is variably set based on, for example, the coolant temperature in order to avoid instability of the internal combustion engine.

  Patent Document 1 discloses a technique for determining a stable state of an internal combustion engine using an ionic current in a combustion chamber so that ignition timing retarding control is started when the combustion state is stabilized after the internal combustion engine is started. Is disclosed. That is, in the apparatus of Patent Document 1, an ion current is detected through an ignition plug, a crank angle period from ignition to ion current disappearance is measured in each cycle, and an average value of, for example, eight cycles of this measured value and Whether or not to retard the ignition timing is determined based on the deviation of each measured value.

JP 2006-57559 A

  In the apparatus of Patent Document 1, it is merely determined whether or not to retard the ignition timing based on the determination of the combustion stability using the ionic current. It is determined regardless of the current measurement. Therefore, while the ignition timing is retarded as if combustion is stable, it is not necessarily delayed to the limit of combustion stability, and there is still room for improvement in exhaust performance. .

The present invention relates to a control device for an internal combustion engine that retards the ignition timing after the cold start of the internal combustion engine and promotes warm-up of the exhaust catalyst device.
Combustion detection means for generating an output correlated with the amount of heat generated in the cylinder;
Predetermined rate crank angle detection means for obtaining a crank angle position at which the heat generation rate in combustion in each cycle becomes a predetermined rate based on the output of the combustion detection means,
During the ignition timing retarding operation, if the variation in the crank angle position at which the heat generation rate is the predetermined rate is smaller than the predetermined variation, the ignition timing retard amount is increased and the residual gas amount in the cylinder is increased. Alternatively, the air-fuel ratio is made lean.

  In the above configuration, an output correlated with the amount of heat generated in the cylinder is obtained by the combustion detection means comprising an ion current detection device, an in-cylinder pressure sensor, etc., and the ratio of the integrated value so far to the total (integrated value) of one cycle As a result, a heat generation rate is obtained. The crank angle position at which this heat generation rate becomes a predetermined rate depends on the variation in initial combustion that has a great influence on the combustion stability. Therefore, if the variation in the crank angle position is small, it can be determined that the combustion is stable, and accordingly, the ignition timing retard amount is increased, the residual gas amount in the cylinder is increased, or the air-fuel ratio is made lean. Is called.

  For example, by increasing the ignition timing retard amount, the ignition timing is retarded to the limit at which combustion becomes actually unstable, and the maximum exhaust gas temperature can be raised and unburned HC can be suppressed.

  Further, for example, by increasing the amount of residual gas in the cylinder by expanding the valve overlap, the temperature of the intake port of the internal combustion engine in the cold state or the cylinder rises due to high residual gas, and the fuel vaporization is good. As a result, unburned HC is reduced.

  In a state where combustion is stable, the unburned HC can also be reduced by making the air-fuel ratio lean.

  According to the control apparatus for an internal combustion engine according to the present invention, unburned HC can be suppressed to the maximum extent that the combustion does not actually become unstable during the ignition timing retarding operation after the cold start.

BRIEF DESCRIPTION OF THE DRAWINGS The structure explanatory drawing which shows one Example of the control apparatus of the internal combustion engine which concerns on this invention. The flowchart of 1st Example which increases ignition timing retard amount. The flowchart of 2nd Example which advances the intake valve opening timing. The flowchart of 3rd Example which makes the air-fuel ratio lean. The flowchart of 4th Example which considered the crank angle position from which a heat generation rate becomes a 2nd predetermined rate. The characteristic view which showed the crank angle position I20 corresponding to the characteristic of an ionic current generation | occurrence | production ratio, and 20%. The characteristic view which showed the crank angle position I70 corresponding to the characteristic of an ionic current generation | occurrence | production ratio, and 70%.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows the system configuration of an automotive internal combustion engine 1 to which the present invention is applied. The internal combustion engine 1 is, for example, an inline 4-cylinder port injection type spark ignition internal combustion engine, and includes a fuel injection valve 3 that injects fuel toward the intake port 2 for each cylinder. The spark plug 4 provided in each cylinder is provided with an ion current detector 5 for detecting an ion current correlated with the in-cylinder combustion pressure or the combustion temperature. The ion current detection device 5 uses the spark plug 4 itself as a detection probe, and is actually configured as a single unit including an ignition coil as an ignition plug drive circuit with an ion current detection function.

  The combustion chamber of each cylinder includes an intake valve 6 and an exhaust valve 7. The intake valve 6 includes a variable valve device 8 that can variably control the opening / closing timing (at least the opening timing) of the intake valve 6. I have. The variable valve device 8 and the spark plug drive circuit are controlled by the engine controller 10.

  An electronically controlled throttle valve 13 whose opening is controlled by a control signal from the engine controller 10 is interposed upstream of the intake collector 12 of the intake passage 11 connected to the intake port 2, and further upstream On the side, an air flow meter 14 for detecting the amount of intake air is disposed.

  The exhaust passage 15 is provided with a catalyst device 16 made of a three-way catalyst, and an air-fuel ratio sensor 17 for detecting the air-fuel ratio is disposed upstream of the catalyst device 16.

  The engine controller 10 includes the ion current detector 5, the air flow meter 14, the air-fuel ratio sensor 17, the crank angle sensor 18 for detecting the engine speed, the water temperature sensor 19 for detecting the cooling water temperature, and the driver. Detection signals of sensors such as an accelerator opening sensor 20 that detects the amount of depression of the accelerator pedal operated by the are input. Based on these detection signals, the engine controller 10 optimally controls the fuel injection amount and injection timing by the fuel injection valve 3, the ignition timing by the spark plug 4, the opening and closing timing of the intake valve 6, the opening of the throttle valve 13, and the like. doing.

  Next, the control immediately after the cold engine start of the internal combustion engine 1 will be described. Before that, the ion current generation ratio will be described based on FIG. It can be said that the ion current detected by the ion current detection device 5 using the spark plug 4 itself as a detection probe correlates with the combustion pressure or combustion temperature in the cylinder and indicates the amount of heat generated in the cylinder. Therefore, in this embodiment, when the total (integrated value) of the ionic currents generated in one cycle is 100 (%), the ratio (%) of the integrated value of the ionic currents up to that is expressed as the ionic current generation rate. Define. As shown in FIG. 6, the ion current generation rate increases with the progress of combustion in each cycle. In other words, the characteristics of the ion current generation ratio shown in FIG. 6 are scaled so that the increase characteristic of the total heat generated in each cycle becomes 100 (%) at the end of combustion regardless of the absolute value of the ion current. It can also be said to be a thing.

  In the example of FIG. 6, the characteristics of the ion current generation rate in four cycles are illustrated on the assumption that the variation in combustion is relatively large. However, in this embodiment, the ion current generation rate is a predetermined rate, for example, 20%. The crank angle position I20 (hereinafter referred to as “20% combustion crank angle I20”) indicates the variation in combustion in each cycle. The predetermined ratio serving as the threshold is not limited to 20%, but is preferably in the range of 10 to 50%, for example, and how the initial combustion greatly affects the combustion stability of the internal combustion engine 1. It is possible to accurately evaluate whether it has occurred. Then, in order to evaluate the variation of the 20% combustion crank angle I20, the standard deviation σI20 is obtained for the 16 20% combustion crank angles I20 in the most recent predetermined number of times, for example, 16 cycles of combustion, and the standard deviation σI20 is predetermined. If the threshold value σI is less than 20th, the combustion of the internal combustion engine 1 is regarded as being stable.

  FIG. 2 shows a first embodiment of the control immediately after starting a specific cold machine. The routine of this flowchart is repeatedly executed every time each cylinder burns after the internal combustion engine 1 is started. In step 1, the intake air amount Qa, the engine speed Ne, the coolant temperature Tw, The 20% combustion crank angle I20 (n) in the combustion of the immediately preceding cycle is read. “N” indicates the number of combustions after the complete explosion, that is, the nth combustion cycle of the internal combustion engine 1 as a whole. In step 2, the basic ignition timing ADV0 is calculated from a predetermined map based on the intake air amount Qa and the engine speed Ne. The basic ignition timing ADV0 is advanced as the value increases.

  In step 3, the coolant temperature Tw is compared with a predetermined temperature Twth. The predetermined temperature Twth is a water temperature that is a threshold value for determining whether or not to perform ignition timing retardation control for promoting warm-up of the catalyst device 16, and if the cooling water temperature Tw is equal to or higher than the predetermined temperature Twth, Assuming completion, the process proceeds to step 12, and the basic ignition timing ADV0 is set as the ignition timing ADV as it is.

  If the cooling water temperature Tw is lower than the predetermined temperature Twth at the cold start, the process proceeds to step 4 to calculate the basic ignition timing retardation amount R0 based on the cooling water temperature Tw. The basic ignition timing retard amount R0 is set to such an extent that the combustion of the internal combustion engine 1 does not become unstable in the cold state.

  In step 5, it is determined whether the number of combustions after starting n has reached a predetermined number of times, for example, 16 times, and the process proceeds to step 6 until n = 16, and from the basic ignition timing ADV to the basic ignition timing retard amount R0. Is subtracted to obtain the ignition timing ADV. That is, until 16 pieces of data necessary for the calculation of the standard deviation σI20 are collected, the ignition timing retardation control is started with the basic ignition timing retardation amount R0 corresponding to the coolant temperature Tw.

  When 16 combustions (for example, four cylinders each in a four-cylinder engine) are completed and the number of combustions n is 16 or more in step 5, the process proceeds from step 5 to step 7 thereafter. In step 7, the standard deviation σI20 is calculated using the latest 16 20% combustion crank angle I20 (n) data. In step 8, the standard deviation σI20 indicating this variation is compared with a predetermined threshold σI20th. Note that “16” of the number of data described above is merely an example, and can be set to an appropriate number. In this example, the standard deviation is used to evaluate the data variation, but other parameters such as variance may be used.

  If the standard deviation σI20 is less than the threshold σI20th in step 8, it is considered that the combustion of the internal combustion engine 1 is stable, and the routine proceeds to step 9, where a minute amount ΔR1 is added to the retard increase amount R1. R1z represents the previous value of the retard increase amount R1. In step 10, the ignition timing ADV is set as “ADV = ADV0−R0−R1”. That is, while it is determined that the combustion of the internal combustion engine 1 is stable based on the standard deviation σI20, the retard increase amount R1 gradually increases and the final ignition timing ADV is gradually delayed. I will horn.

  On the other hand, if the standard deviation σI20 is greater than or equal to the threshold σI20th in step 8, it is considered that the combustion of the internal combustion engine 1 has become unstable, the process proceeds to step 11, and the delay increase amount R1 is a minute amount ΔR1 from the previous value R1z. Reduce. In step 10, retard control of the ignition timing ADV is performed using the retard increase amount R1. Therefore, if it is determined that the internal combustion engine 1 is destabilized based on the standard deviation σI20, the retard increase amount R1 gradually decreases, and the final ignition timing ADV is delayed from the basic ignition timing ADV0. Angular amount decreases.

  As described above, in the above-described embodiment, the retardation increase amount R1 is repeatedly increased and decreased based on the determination of the variation of the 20% combustion crank angle I20 (standard deviation σI20) that well represents the state of the initial combustion in each combustion cycle. The maximum ignition timing retardation is performed so that the actual combustion stable state of the internal combustion engine 1 is maintained near a predetermined limit. Therefore, after the internal combustion engine 1 is cold started, the ignition timing is retarded with the maximum possible retard amount, and the early activation of the catalyst due to the maximum increase in the exhaust temperature and the suppression of unburned HC due to afterburning. Can be planned.

  When the ignition timing changes, the combustion timing also changes. Therefore, the crank angle position itself, which is the 20% combustion crank angle I20, that is, the ionic current generation rate of 20%, changes, but in steps 7 and 8, the standard deviation σI20 ( That is, since the variation of each data) is evaluated, it is not affected by the retard of the ignition timing.

  Next, FIG. 3 shows a second embodiment of the control immediately after the specific cold start. In this embodiment, the intake valve opening timing (in other words, valve overlap) is controlled in accordance with the stable combustion state of the internal combustion engine 1 during the ignition timing retarding operation after the cold start. That is, when the intake valve opening timing is advanced via the variable valve operating device 8 during the ignition timing retarding operation, the temperature of the intake port 2 of the internal combustion engine 1 in the cold state is changed to the residual gas due to the expansion of the valve overlap. The fuel wall flow is suppressed. In addition, since the temperature in the cylinder rises due to the residual gas, fuel vaporization is improved and unburned HC is reduced. Furthermore, unburned HC discharged to the exhaust port at the end of the exhaust stroke is sucked back to the intake side, and this also reduces unburned HC. These effects are particularly effective in suppressing unburned HC that is finally discharged to the outside because the catalyst is inactive.

  The processing in each step is similar to the processing in each step of the first embodiment described above. In step 101, the intake air amount Qa, the engine speed Ne, the cooling water temperature Tw, and the combustion in the immediately preceding cycle are performed. 20% combustion crank angle I20 (n) is read. In step 102, the basic ignition timing ADV0 is calculated based on the intake air amount Qa and the engine speed Ne, and the basic intake cam phase advance amount VTC0 in the variable valve gear 8 is calculated from a predetermined map. As the basic intake cam phase advance amount VTC0 is larger, the intake valve opening timing is advanced.

  In step 103, the coolant temperature Tw is compared with a predetermined temperature Twth. If the coolant temperature Tw is equal to or higher than the predetermined temperature Twth, the routine proceeds to step 112, where the basic ignition timing ADV0 is used as it is as the ignition timing ADV. Further, the intake cam phase advance amount VTC of the variable valve apparatus 8 is also maintained as the basic intake cam phase advance amount VTC0.

  If the cooling water temperature Tw is lower than the predetermined temperature Twth, the routine proceeds to step 104, and the basic ignition timing retardation amount R0 is calculated based on the cooling water temperature Tw as in step 4 described above.

  In step 105, it is determined whether the number of combustions after starting n has reached a predetermined number of times, for example, 16 times, and until n = 16, the routine proceeds to step 106 and the basic ignition timing retard amount R0 from the basic ignition timing ADV. Is set to the ignition timing ADV, and the basic intake cam phase advance amount VTC0 is set as the intake cam phase advance amount VTC of the variable valve apparatus 8. That is, the basic intake cam phase determined from the intake air amount Qa and the engine speed Ne during the ignition timing retarded operation by the basic ignition timing retard amount R0 until 16 data necessary for the calculation of the standard deviation σI20 are collected. The advance amount VTC0 is maintained.

  When the combustion of 16 times (for example, 4 times for each cylinder in a 4-cylinder engine) is finished and the number of combustions n becomes 16 or more in Step 105, the process proceeds from Step 105 to Step 107 and Step 108. These steps 107 and 108 are the same as steps 7 and 8 described above, and in step 107, the standard deviation σI20 is calculated using the latest 16 20% combustion crank angle I20 (n) data. In step 108, the standard deviation σI20 indicating this variation is compared with a predetermined threshold σI20th.

  If the standard deviation σI20 is less than the threshold σI20th in step 108, it is considered that the combustion of the internal combustion engine 1 is stable, and the routine proceeds to step 109 where the minute amount ΔVTC1 is set to the previous value VTC1z of the intake cam phase feedback advance amount VTC1. Add. In step 110, the intake cam phase advance amount VTC is set as “VTC = VTC0 + VTC1”. That is, while it is determined that the combustion of the internal combustion engine 1 is stable based on the standard deviation σI20, the intake cam phase advance amount VTC gradually increases and the intake valve opening timing gradually advances. I will horn. As in step 106, the ignition timing ADV is set as the basic ignition timing ADV0 minus the basic ignition timing retard amount R0.

  On the other hand, if the standard deviation σI20 is greater than or equal to the threshold σI20th in step 108, it is considered that the combustion of the internal combustion engine 1 has become unstable, and the routine proceeds to step 111 where the intake cam phase feedback advance amount VTC1 is determined from the previous value VTC1z. Decrease minute amount ΔVTC1. In step 110, the intake cam phase feedback advance amount VTC is set using the intake cam phase feedback advance amount VTC1. Accordingly, when it is determined that the internal combustion engine 1 is destabilized based on the standard deviation σI20, the intake cam phase feedback advance amount VTC1 gradually decreases, and the advance amount of the final intake valve opening timing. VTC is decreasing.

  As described above, in the above embodiment, while the coolant temperature Tw is lower than the predetermined temperature Twth, the ignition timing retarding operation is executed with the basic ignition timing retard amount R0 corresponding to the coolant temperature Tw. Then, during this ignition timing retarding operation, the intake cam phase feedback advance amount VTC1 is increased or decreased based on the determination of the variation of the 20% combustion crank angle I20 (standard deviation σI20) that well represents the initial combustion state of each combustion cycle. As a result, the intake valve opening timing is advanced to the maximum so that the actual stable combustion state of the internal combustion engine 1 is maintained near a predetermined limit. In other words, along with the ignition timing retard control, the residual gas amount is increased to the maximum, and unburned HC can be suppressed at the catalyst inactive stage.

  Further, since the same effect can be obtained by controlling the amount of residual gas by controlling the closing timing of the exhaust valve 7, a variable valve device capable of variably controlling the closing timing of the exhaust valve 7 is provided to determine the standard deviation σI20. On the basis of the feedback control of the exhaust valve closing timing (when the standard deviation σI20 is less than the threshold σI20th, the exhaust valve closing timing is retarded, and when the standard deviation σI20 is greater than or equal to the threshold σI20th, the exhaust valve closing timing is advanced). It may be.

  In the second embodiment, the ignition timing retard amount R0 is constant regardless of the combustion stable state. However, as in the first embodiment, the ignition timing retard amount R0 also increases or decreases according to the combustion stable state. You may make it make it.

  Next, FIG. 4 shows a third embodiment of the control immediately after the specific cold start. In this embodiment, the air-fuel ratio is made leaner during the ignition timing retarding operation after the cold start. In a state in which the combustion of the internal combustion engine 1 is stable, unburned HC decreases basically as the air-fuel ratio becomes leaner.

  The process of each step in FIG. 4 is similar to the process of each step of the first and second embodiments described above. In step 201, the intake air amount Qa, the engine speed Ne, the cooling water temperature Tw, The 20% combustion crank angle I20 (n) in the combustion of the immediately preceding cycle is read. In step 202, the basic ignition timing ADV0 is calculated based on the intake air amount Qa and the engine speed Ne, and the basic fuel injection amount (injection pulse width) Tp of the fuel injection valve 3 is calculated. The basic fuel injection amount Tp is set so as to be the stoichiometric air-fuel ratio under each operating condition.

  In step 203, the cooling water temperature Tw is compared with a predetermined temperature Twth. If the cooling water temperature Tw is equal to or higher than the predetermined temperature Twth, the routine proceeds to step 212, where the basic ignition timing ADV0 is used as it is as the ignition timing ADV. The basic fuel injection amount Tp is set as the fuel injection amount Ti.

  If the cooling water temperature Tw is less than the predetermined temperature Twth, the routine proceeds to step 204, and the basic ignition timing retardation amount R0 is calculated based on the cooling water temperature Tw as in steps 4 and 104 described above.

  In step 205, it is determined whether the number of combustions after starting n has reached a predetermined number of times, for example, 16 times. The process proceeds to step 206 until n = 16, and the basic ignition timing retard amount R0 from the basic ignition timing ADV. Is set to the ignition timing ADV, and the basic fuel injection amount Tp is set as the fuel injection amount Ti. That is, the air-fuel ratio is maintained at the stoichiometric air-fuel ratio during the ignition timing retarding operation with the basic ignition timing retarding amount R0 until 16 pieces of data necessary for the calculation of the standard deviation σI20 are collected.

  When the combustion of 16 times (for example, 4 times for each cylinder in a 4-cylinder engine) is completed and the number of combustions n becomes 16 or more in step 205, the process proceeds from step 205 to step 207 and step 208. These steps 207 and 208 are the same as steps 7 and 8 described above, and in step 207, the standard deviation σI20 is calculated using the latest 16 20% combustion crank angle I20 (n) data. In step 208, the standard deviation σI20 indicating this variation is compared with a predetermined threshold σI20th.

  If the standard deviation σI20 is less than the threshold σI20th in step 208, it is considered that the combustion of the internal combustion engine 1 is stable, and the routine proceeds to step 209, where the minute amount ΔTFBYA is subtracted from the previous value TFBYAz of the target equivalent ratio TFBYA. In step 210, the fuel injection amount Ti is set as “Ti = Tp × TFBYA”.

  The target equivalent ratio TFBYA is a correction coefficient for the fuel injection amount. The smaller the value, the leaner the air-fuel ratio. Here, the target equivalence ratio TFBYA is limited to a range from the maximum value 1 to the minimum value 0.9 by processing not shown. The maximum value 1 corresponds to the theoretical air fuel ratio, and the minimum value 0.9 corresponds to an air fuel ratio of about 16.

  That is, while it is determined that the combustion of the internal combustion engine 1 is stable based on the standard deviation σI20, the air-fuel ratio is gradually made lean by the process of step 210. As in step 206, the ignition timing ADV is set as the basic ignition timing ADV0 minus the basic ignition timing retard amount R0.

  On the other hand, if the standard deviation σI20 is greater than or equal to the threshold σI20th in step 208, it is considered that the combustion of the internal combustion engine 1 has become unstable, and the routine proceeds to step 211, where the minute value ΔTFBYA is set to the previous value TFBYAz as the target equivalent ratio TFBYA. Add. In step 210, the fuel injection amount Ti is set by multiplying the basic fuel injection amount Tp by the target equivalent ratio TFBYA. Therefore, if it is determined that the internal combustion engine 1 is destabilized based on the standard deviation σI20, the lean air / fuel ratio approaches the stoichiometric air / fuel ratio.

  As described above, in the above embodiment, while the coolant temperature Tw is lower than the predetermined temperature Twth, the ignition timing retarding operation is executed with the basic ignition timing retard amount R0 corresponding to the coolant temperature Tw. Then, during this ignition timing retarding operation, the result of feedback control of the fuel injection amount Ti based on the determination of the variation (standard deviation σI20) of the 20% combustion crank angle I20 that well represents the initial combustion state of each combustion cycle The air-fuel ratio is leaned to the maximum within a range in which the actual combustion stable state of the internal combustion engine 1 is maintained near a predetermined limit. As a result, unburned HC can be suppressed at the catalyst inactive stage.

  In the third embodiment, the ignition timing retardation amount R0 is constant regardless of the stable combustion state. However, as in the first embodiment, the ignition timing retardation amount R0 also increases or decreases depending on the stable combustion state. You may make it make it.

  Next, FIG. 5 shows a fourth embodiment of the control immediately after the specific cold start. In this embodiment, as in the first embodiment, the ignition timing ADV is further retarded in accordance with the stable combustion state. On the other hand, when the end of combustion is excessively delayed due to this retardation, the ignition timing ADV is further increased. Without retarding, unburned HC is suppressed by the advance of the intake valve opening timing as in the second embodiment.

  In order to evaluate whether or not the end of the combustion is excessively delayed as described above, in this embodiment, as shown in FIG. 7, the second ion ion generation rate indicating the heat generation rate is relatively large. A crank angle position I70 (hereinafter referred to as “70% combustion crank angle I70”) at a predetermined ratio, for example, 70% is obtained and compared with a predetermined threshold value I70th. That is, it is determined whether the position is on the advance side or the retard side with respect to the crank angle position I70th that is a predetermined threshold value. The ionic current generation ratio is not limited to 70%, but is set to a value that is at least larger than a first predetermined ratio (for example, 20% described above) corresponding to initial combustion for evaluation of the combustion stable state. For example, it is set within a range of 60% to 90%. The threshold value I70th is set, for example, so that combustion ends before the exhaust valve 7 is opened.

  In step 301 of FIG. 5, the intake air amount Qa, engine speed Ne, cooling water temperature Tw, 20% combustion crank angle I20 (n) and 70% combustion crank angle I70 in the previous cycle combustion are read. . In step 302, the basic ignition timing ADV0 is calculated based on the intake air amount Qa and the engine speed Ne, and the basic intake cam phase advance amount VTC0 in the variable valve gear 8 is calculated from a predetermined map.

  In step 303, the coolant temperature Tw is compared with a predetermined temperature Twth. If the cooling water temperature Tw is equal to or higher than the predetermined temperature Twth, the process proceeds to step 316, and the basic ignition timing ADV0 is set as the ignition timing ADV as it is. Further, the intake cam phase advance amount VTC of the variable valve apparatus 8 is also maintained as the basic intake cam phase advance amount VTC0.

  If the cooling water temperature Tw is lower than the predetermined temperature Twth, the routine proceeds to step 304, and the basic ignition timing retardation amount R0 is calculated based on the cooling water temperature Tw as in step 4 and the like described above.

  In step 305, as in step 5 and the like described above, it is determined whether the number of combustions n after starting has reached a predetermined number of times, for example, 16 times, and the process proceeds to step 306 until n = 16 and the basic ignition timing ADV is reached. Then, the basic ignition timing retard amount R0 is subtracted to obtain the ignition timing ADV, and the basic intake cam phase advance amount VTC0 is set as the intake cam phase advance amount VTC of the variable valve system 8. That is, until 16 pieces of data necessary for the calculation of the standard deviation σI20 are collected, the ignition timing retarding operation with the basic ignition timing retarding amount R0 is continued, and the basic determined by the intake air amount Qa and the engine speed Ne. The intake cam phase advance amount VTC0 is maintained.

  When the combustion of 16 times (for example, 4 times for each cylinder in a 4-cylinder engine) is completed and the number of combustions n becomes 16 or more in step 305, the process proceeds from step 305 to step 307 and step 308. These steps 307 and 308 are the same as the above-described steps 7 and 8 and the like. In step 307, the standard deviation σI20 is calculated using the latest 16 20% combustion crank angle I20 (n) data. . In step 308, the standard deviation σI20 indicating this variation is compared with a predetermined threshold σI20th.

  If the standard deviation σI20 is less than the threshold σI20th in step 308, it can be considered that the combustion of the internal combustion engine 1 is stable. In this embodiment, however, the routine further proceeds to step 309, where 70% combustion in the immediately preceding combustion is performed. It is determined whether or not the crank angle I70 is less than the threshold value I70th. If it is less than the threshold value I70th in step 309, it is determined that there is no excessive delay at the end of combustion, and the routine proceeds to step 310, where a minute amount ΔR1 is added to the previous value R1z of the retard increase amount R1. In step 311, the ignition timing ADV is set as “ADV = ADV0−R0−R1”. That is, while it is determined that the combustion of the internal combustion engine 1 is stable based on the standard deviation σI20, the retardation increase amount R1 gradually increases on the condition that the end of combustion is not excessively delayed. The final ignition timing ADV is gradually retarded.

  If it is greater than or equal to the threshold value I70th at step 309, it is determined that combustion cannot be delayed any further, and the routine proceeds to step 312, where a minute amount ΔVTC1 is added to the previous value VTC1z of the intake cam phase feedback advance amount VTC1. In step 311, the intake cam phase advance amount VTC is set as “VTC = VTC 0 + VTC 1”. That is, when the 70% combustion crank angle I70 is equal to or greater than the threshold value I70th, the ignition timing ADV is retarded further while it is determined that the combustion of the internal combustion engine 1 is stable based on the standard deviation σI20. Without this, the intake cam phase advance amount VTC gradually increases, and the intake valve opening timing gradually advances. By the advance angle of the intake valve opening timing, the action of suppressing unburned HC is obtained as in the second embodiment described above.

  On the other hand, if the standard deviation σI20 is greater than or equal to the threshold σI20th in step 308, it can be considered that the combustion of the internal combustion engine 1 has become unstable. In this embodiment, however, the process also proceeds to step 313 and step 309 is performed. Similarly, it is determined whether or not the 70% combustion crank angle I70 in the immediately preceding combustion is less than the threshold value I70th. If it is less than the threshold value I70th in step 313, it is determined that there is no excessive delay at the end of combustion, and the routine proceeds to step 314 where the minute amount ΔVTC1 is subtracted from the previous value VTC1z as the intake cam phase feedback advance amount VTC1. In step 311, the intake cam phase feedback advance amount VTC is set using the intake cam phase feedback advance amount VTC1.

  That is, when it is determined that the internal combustion engine 1 is destabilized based on the standard deviation σI20, if the 70% combustion crank angle I70 is less than the threshold value I70th, the main factor of destabilization is the intake valve opening timing. Since it is considered that the advance angle is excessive, the intake cam phase feedback advance amount VTC1 is gradually decreased.

  On the other hand, if it is equal to or greater than the threshold value I70th in step 313, the process proceeds to step 315, and the minute amount ΔR1 is subtracted from the previous value R1z as the retardation increase amount R1. In step 311, the retard control of the ignition timing ADV is performed using the retard increase amount R1. Therefore, the amount of retardation of the final ignition timing ADV from the basic ignition timing ADV0 decreases.

  That is, when the combustion of the internal combustion engine 1 is unstable and the 70% combustion crank angle I70 is equal to or greater than the threshold value I70th, the main factor of instability of the internal combustion engine 1 is an excessive retardation of the ignition timing ADV. Since it is possible, gradually reduce the retard amount.

  As described above, in the above embodiment, during the ignition timing retard operation after the cold start, the determination of the variation (standard deviation σI20) of the 20% combustion crank angle I20 that well represents the initial combustion state of each combustion cycle and the end of combustion. Based on the comparison between the 70% combustion crank angle I70 and the threshold value I70th, the correction of the retard amount of the ignition timing ADV and the increase / decrease correction of the intake cam phase feedback advance amount VTC1 are appropriately combined. As a result, it is possible to effectively suppress unburned HC in the catalyst inactive stage without excessively delaying the end of combustion in each cycle.

  Although several embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made. For example, in the above embodiment, the ion current detection device 5 is used, but the amount of heat generated in the cylinder can be obtained using an in-cylinder pressure sensor. Further, an increase in the ignition timing retardation amount, an increase in the residual gas amount in the cylinder, and a lean air-fuel ratio based on the stable combustion state can be executed in an appropriate combination.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 3 ... Fuel injection valve 4 ... Spark plug 5 ... Ion current detection apparatus 8 ... Variable valve operating apparatus 10 ... Engine controller

Claims (5)

In the control device for an internal combustion engine that retards the ignition timing after the cold start of the internal combustion engine and promotes warm-up of the exhaust catalyst device,
Combustion detection means for generating an output correlated with the amount of heat generated in the cylinder;
Predetermined rate crank angle detection means for obtaining a crank angle position at which the heat generation rate in combustion in each cycle becomes a predetermined rate based on the output of the combustion detection means,
During the ignition timing retarding operation, when the variation in crank angle at which the heat generation rate is the predetermined rate is smaller than the predetermined variation, the ignition timing retard amount is increased and the residual gas amount in the cylinder is increased. Or a control device for an internal combustion engine, wherein the air-fuel ratio is made lean.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the combustion detecting means comprises an ion current detecting device.   The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the predetermined ratio is set within a range of 10% to 50%. A second predetermined ratio crank angle detecting means for obtaining a crank angle position at which a heat generation ratio in combustion in each cycle is a second predetermined ratio larger than the predetermined ratio based on the output of the combustion detecting means;
During the ignition timing retarding operation, when the variation in the crank angle position where the heat generation rate becomes the predetermined rate is smaller than the predetermined variation,
If the crank angle position at which the heat generation rate is the second predetermined rate is on the advance side of the predetermined threshold, the ignition timing retard amount is increased, and if the crank angle position is on the retard side of the predetermined threshold, the residual gas The control device for an internal combustion engine according to any one of claims 1 to 3, wherein the amount is increased. In the control method of an internal combustion engine that retards the ignition timing after the cold start of the internal combustion engine and promotes warm-up of the exhaust catalyst device,
During the above ignition timing retarded operation,
By detecting the amount of heat generated in the cylinder, the crank angle position where the heat generation rate in the combustion of each cycle is a predetermined rate is obtained,
When the variation in the crank angle position at which the heat generation rate becomes the predetermined rate is smaller than the predetermined variation, the ignition timing retard amount is increased, the residual gas amount in the cylinder is increased, or the air-fuel ratio is made lean. A control method for an internal combustion engine.

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