JP2016125363A - Internal combustion engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine control device capable of appropriately curbing degradation of a combustion state in accordance with a control parameter state.SOLUTION: An internal combustion engine can execute: fuel injection amount feedback control which utilizes a crank angle period from ignition timing to timing when a certain crank angle leads to a predetermined combustion mass ratio; and ignition timing feedback control which utilizes a position of a combustion gravity center. When abnormality is found in the calculated crank angle period, the internal combustion engine stops execution of not only the ignition timing feedback control but also the fuel injection amount feedback control and sets respective correction values for the ignition timing and for the fuel injection amount at the values equal to the previous ones or closer to zero than the previous ones.SELECTED DRAWING: Figure 11

Description

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

  As a fuel efficiency technique for an internal combustion engine, it is known that a lean burn operation that operates at an air / fuel ratio that is leaner than the stoichiometric air / fuel ratio is effective. In general, the leaner the fuel fluctuation, the lower the fuel consumption and the lower the NOx emissions. Therefore, monitoring the engine state and controlling the air / fuel ratio as lean as possible within the range where the drivability does not deteriorate, That is, it can be said that lean limit control in which the air-fuel ratio is controlled near the lean limit is preferable.

For example, JP-A-2-153243 discloses that lean limit control is performed in accordance with torque fluctuation. Further, it is disclosed that when the environment changes during restart, the target air-fuel ratio changes, so that the target is first made rich and gradually changed.
The applicant has recognized the following documents including the above-mentioned documents as related to the present invention.

JP-A-2-153243 JP-A-1-290970

  In the lean limit control using torque fluctuation, torque fluctuation during operation is detected by statistically processing the torque, and the air-fuel ratio is controlled near the lean limit based on the detected torque fluctuation. However, since the torque fluctuation is a parameter based on statistical processing, it cannot be calculated until a predetermined number of times of combustion (for example, 100 times) has elapsed. In addition, since it is a value based on fluctuations in engine torque during steady operation, it must be grasped separately from transient changes in torque due to various factors (such as vehicle accelerator pedal operation and air and EGR gas response delays). Is difficult. Further, in order to increase the control opportunity, it is necessary to allow a transitional change, which reduces the calculation accuracy of torque fluctuation. As described above, the method using the torque fluctuation based on the statistical processing takes time and cannot be realized in the transient operation.

  In response to such a problem, the applicant of the present application disclosed in Japanese Patent Application No. 2013-235803 as a lean limit control method using the detected value of the in-cylinder pressure sensor in a method that does not depend on the statistical method, and combustion from the ignition timing (SA). The feedback control of the fuel injection amount using the crank angle period (SA-CA10) up to CA10 which is the crank angle when the mass ratio becomes 10% as a control parameter, and the change of the air-fuel ratio accompanying the execution of the feedback control As an ignition timing control for eliminating the influence of the change in the optimum ignition timing (MBT) caused by the above, it is proposed to perform cooperatively the ignition timing feedback control using the CA50 indicating the combustion center of gravity position as a control parameter. . In this lean limit control method, the fuel injection amount feedback control using the SA-CA10 is performed so that the ignition timing is a predetermined target ignition efficiency (maximum efficiency when MBT is MBT) by the ignition timing feedback control using the CA50. It is assumed that the ignition timing is controlled accordingly.

  By the way, when an abnormality occurs in the control parameter based on the detection value of the in-cylinder pressure sensor, the ignition timing and the fuel injection amount are erroneously corrected by the two feedback controls described above, and on the contrary, the fuel consumption deteriorates, the emission increases, the drivability deteriorates, etc. May be caused. Therefore, it is necessary to determine the control parameter abnormality and perform appropriate control. Although it is conceivable that abnormality is determined for each of the control parameters real CA50 and real SA-CA10 and processing according to the combination of abnormality types is executed, the processing becomes complicated and the calculation load increases.

  The present invention has been made in order to solve the above-described problem.Feedback control of the fuel injection amount using a crank angle period from the ignition timing to a crank angle at which a predetermined combustion mass ratio is achieved as a control parameter; In an internal combustion engine capable of performing feedback control of ignition timing based on the position of the center of combustion, an internal combustion engine control apparatus capable of appropriately suppressing deterioration of the combustion state according to the state of the control parameter while suppressing the calculation load The purpose is to provide.

In order to solve the above-described problems, the present invention provides a control device for an internal combustion engine,
In-cylinder pressure detecting means for detecting in-cylinder pressure;
Crank angle detecting means for detecting the crank angle;
Combustion mass ratio calculating means for calculating a combustion mass ratio based on the detected in-cylinder pressure and the detected crank angle;
Ignition timing determination means for determining the ignition timing by correcting the basic ignition timing according to the operating state with the ignition timing correction value;
Combustion center-of-gravity position calculating means for calculating a combustion center-of-gravity position based on the calculated combustion mass ratio;
Ignition timing adjustment means for adjusting the ignition timing correction value so that the calculated combustion center of gravity position coincides with the target combustion center of gravity position corresponding to the target ignition efficiency;
Fuel injection amount determination means for determining the fuel injection amount by correcting the basic injection amount according to the operating state with the injection amount correction value;
A crank angle period calculating means for calculating a crank angle period from an ignition timing to a crank angle at a predetermined combustion mass ratio lower than the combustion center of gravity;
Injection amount adjusting means for adjusting the injection amount correction value so that the calculated crank angle period coincides with the target crank angle period;
Crank angle period abnormality determining means for determining whether or not the calculated crank angle period is abnormal;
Stop means for stopping adjustment by the ignition timing adjusting means and the injection amount adjusting means when it is determined that the calculated crank angle period is abnormal;
When it is determined that the calculated crank angle period is abnormal, the ignition timing correction value and the injection amount correction value are set to the previous value, the average value in the most recent cycle, or a value closer to zero than the previous value, respectively. Correction value setting means.

  According to the present invention, when the value of the control parameter (calculated crank angle period) is abnormal, not only the adjustment of the fuel injection amount by the injection amount adjustment means but also the adjustment of the ignition timing by the ignition timing adjustment means. Stopped. Thereby, the deterioration of the combustion state by incorrect adjustment can be suppressed. Further, the calculation load can be suppressed by performing the abnormality determination only for the calculated crank angle period. Further, when adjustment by both adjusting means is stopped, the ignition timing correction value and the injection amount correction value can be set so as to leave the effect of adjustment by the ignition timing adjusting means and the injection amount adjusting means.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 1 of this invention. It is a figure showing the ignition timing and the waveform of a combustion mass ratio. It is a figure showing the relationship between each of NOx emission amount, fuel consumption, torque fluctuation, and SA-CA10 and the air-fuel ratio (A / F). It is a figure showing the relationship between MBT and the combustion gravity center position (CA50 which is a 50% combustion point) at the time of MBT control with respect to the air fuel ratio in the vicinity of the lean limit. It is a figure showing the relationship between the air fuel ratio at the time of a lean limit, and ignition timing. It is a block diagram for demonstrating the outline | summary of the feedback control using SA-CA10 which concerns on Embodiment 1 of this invention, and the feedback control using CA50. It is a flowchart which shows the control routine which ECU40 performs in order to implement | achieve feedback control using SA-CA10 which concerns on Embodiment 1 of this invention, and feedback control using CA50. It is a flowchart which shows the subroutine which ECU40 performs in order to implement | achieve feedback control using SA-CA10 which concerns on Embodiment 1 of this invention. It is a figure which shows the list | wrist of corresponding | compatible control in this embodiment. It is a figure for demonstrating the combination of the abnormal kind of control parameter, the abnormal kind of control parameter (SA-CA10), and corresponding | compatible control. 4 is a flowchart showing a control routine executed by the ECU 40 in order to realize appropriate ignition timing control and fuel injection control when an abnormality occurs in a control parameter in Embodiment 1 of the present invention. In Embodiment 1 of this invention, it is a flowchart which shows the control routine of the process A which ECU40 performs. In Embodiment 1 of this invention, it is a flowchart which shows the control routine of process B-1 which ECU40 performs. In Embodiment 1 of this invention, it is a flowchart which shows the control routine of process B-2 which ECU40 performs. 1 is a block diagram of a control device for an internal combustion engine according to the present invention. FIG.

  Hereinafter, embodiments of the present invention will be described in detail 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.

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration of an internal combustion engine according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes a spark ignition type internal combustion engine 10. A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in the cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  The intake port of the intake passage 16 is provided with an intake valve 20 that opens and closes the intake port. An exhaust valve 22 for opening and closing the exhaust port is provided at the exhaust port of the exhaust passage 18. The intake passage 16 is provided with an electronically controlled throttle valve 24.

  Each cylinder of the internal combustion engine 10 has a fuel injection device 26 (in the figure, a fuel injection valve constituting the fuel injection device) for directly injecting fuel into the combustion chamber 14 (inside the cylinder), and An ignition device 28 for igniting the air-fuel mixture (in the figure, a spark plug as a component of the ignition device 28 is shown) is provided. Further, an in-cylinder pressure sensor 30 for detecting the in-cylinder pressure is incorporated in each cylinder.

  Furthermore, the system of the present embodiment includes an ECU (Electronic Control Unit) 40. The ECU 40 includes a memory for storing various programs and data, a processor for executing and calculating various programs, an input interface for inputting data used for calculation of various programs, and an output interface for outputting instructions based on the calculation results of the various programs. Prepare.

  In addition to the in-cylinder pressure sensor 30 described above, the input interface of the ECU 40 includes an operating state of the internal combustion engine 10 such as a crank angle sensor 42 for acquiring the engine rotation speed and an air flow meter 44 for measuring the intake air amount. Various sensors for acquiring are connected. Further, various actuators for controlling the operation of the internal combustion engine 10, such as the throttle valve 24, the fuel injection device 26, and the ignition device 28, are connected to the output interface of the ECU 40. The ECU 40 performs predetermined engine control such as fuel injection control and ignition control by driving the various actuators based on the sensor output and a predetermined program. Further, the ECU 40 has a function of acquiring an output signal of the in-cylinder pressure sensor 30 by performing AD conversion in synchronization with the crank angle. Thereby, the in-cylinder pressure at an arbitrary crank angle timing can be detected within a range allowed by the AD conversion resolution. Further, the ECU 40 has a function of calculating the value of the cylinder volume determined by the position of the crank angle according to the crank angle.

[Control of Embodiment 1]
(Ignition timing and combustion mass ratio)
FIG. 2 is a diagram showing the ignition timing and the combustion mass ratio waveform. According to the system of this embodiment including the in-cylinder pressure sensor 30 and the crank angle sensor 42, in-cycle pressure data (in-cylinder pressure waveform) can be acquired on a crank angle (CA) basis in each cycle of the internal combustion engine 10. . A combustion mass ratio (hereinafter referred to as “MFB”) having a waveform as shown in FIG. 2 can be calculated using the in-cylinder pressure waveform after the absolute pressure correction is performed by a known method.

  More specifically, the in-cylinder heat generation amount Q at an arbitrary crank angle θ can be calculated according to the following equation (1) using in-cylinder pressure data. Then, the MFB at an arbitrary crank angle θ can be calculated according to the following equation (2) using the calculated calorific value Q in the cylinder. Therefore, the crank angle (hereinafter referred to as “CAα”) when the MFB is a predetermined ratio α (%) can be obtained by using the equation (2).

In the above equation (1), P is the in-cylinder pressure, V is the in-cylinder volume, and κ is the specific heat ratio of the in-cylinder gas. Further, P ₀ and V ₀ are the calculation start point θ ₀ (the predetermined crank angle θ during the compression stroke (with the intake valve 20 closed) determined with a margin with respect to the assumed combustion start point). In-cylinder pressure and in-cylinder volume. In the above equation (2), θ _sta is the combustion start point (CA0), and θ _fin is the combustion end point (CA100).

  Here, a typical crank angle CAα will be described with reference to FIG. Combustion in the cylinder starts with a delay in ignition after the air-fuel mixture is ignited at the ignition timing (SA). This combustion start point, that is, the point where the MFB rises is referred to as CA0. The crank angle period (CA0-CA10) from CA0 to MFB when the MFB is 10% corresponds to the initial combustion period, and the crank angle period from CA10 to the crank angle CA90 when the MFB is 90% ( CA10-CA90) corresponds to the main combustion period. Further, the crank angle CA50 when the MFB is 50% corresponds to the combustion gravity center position. In the present embodiment, the crank angle period from SA to CA10 is referred to as “SA-CA10”.

(Lean limit control using SA-CA10)
FIG. 3 is a diagram showing the relationship between the NOx emission amount, fuel consumption, torque fluctuation, and SA-CA10 and the air-fuel ratio (A / F). As a fuel efficiency technique for an internal combustion engine, a lean burn operation performed at an air / fuel ratio that is leaner than a stoichiometric air / fuel ratio is effective. As shown in the graph relating to the NOx emission amount and the graph relating to the fuel efficiency in FIG. However, if the air-fuel ratio is made too lean, combustion deteriorates and fuel efficiency deteriorates. On the other hand, the torque fluctuation gradually increases as the air-fuel ratio becomes lean, and rapidly increases when the air-fuel ratio exceeds a certain value, as shown in the graph relating to torque fluctuation in FIG. The torque fluctuation here is a fluctuation value with respect to a time-series torque value. Hereinafter, the air-fuel ratio at the lean combustion limit of the air-fuel mixture, more specifically, the air-fuel ratio when the torque fluctuation value reaches the threshold value that becomes the limit from the viewpoint of drivability of the internal combustion engine 10 is referred to as “lean limit”.

  In order to realize low fuel consumption and low NOx emission from the graph relating to the NOx emission amount, the graph relating to the fuel consumption, and the graph relating to torque fluctuation in FIG. 3, the state of the internal combustion engine 10 can be monitored and drivability cannot be deteriorated. It can be said that it is preferable to control the air-fuel ratio so as to be lean only, that is, to control the air-fuel ratio in the vicinity of the lean limit. Hereinafter, such air-fuel ratio control is referred to as “lean limit control”.

  In the present embodiment, as lean limit control, feedback control of the fuel injection amount using SA-CA10 is performed for each cylinder. In the feedback control using SA-CA10, the fuel injection amount is adjusted so that the difference between a predetermined target SA-CA10 (target crank angle period) near the lean limit and the actual SA-CA10 is zero. It is. More specifically, when the actual SA-CA10 is smaller than the target SA-CA10, the actual SA-CA with respect to the fuel injection amount for the next cycle based on the basic injection amount corresponding to the intake air amount of each cylinder. A decrease correction amount for bringing CA10 closer to the target SA-CA10 is added. On the other hand, when the actual SA-CA10 is larger than the target SA-CA10, the actual SA-CA10 is set to the target SA for the fuel injection amount for the next cycle based on the basic injection amount corresponding to the intake air amount of each cylinder. -An increase correction amount for approaching CA10 is added.

  The advantage of using SA-CA10 as a parameter of the lean limit control of this embodiment is demonstrated. SA-CA10 is a parameter representing ignition delay. As shown in the graph relating to SA-CA10 in FIG. 3, SA-CA10 has a high correlation with the air-fuel ratio, and maintains good linearity with respect to the air-fuel ratio even near the lean limit. For this reason, the use of SA-CA10 facilitates feedback control of the air-fuel ratio in the vicinity of the lean limit.

  Further, it can be said that SA-CA10 is more representative of the lean limit than the air-fuel ratio itself for the following reason. That is, although the air-fuel ratio that becomes the lean limit changes depending on the operating conditions (for example, the engine water temperature), the SA-CA10 is less likely to change depending on the operating conditions than the air-fuel ratio. It has been confirmed. In other words, since the air-fuel ratio that becomes the lean limit largely depends on the ignition factor of the air-fuel mixture, it can be said that the SA-CA10 that represents the ignition delay is less affected by the operating conditions than the air-fuel ratio itself. However, since the time per crank angle changes when the engine speed changes, the target SA-CA10 that is the target value of SA-CA10 is preferably set according to the engine speed. More preferably, since SA-CA10 also changes depending on the engine load factor, the target SA-CA10 may be set according to the engine load factor instead of or together with the engine rotation speed.

(Cooperation between feedback control of fuel injection amount using SA-CA10 and ignition timing feedback control using CA50)
FIG. 4 is a diagram showing the relationship between MBT and the combustion gravity center position (CA50 which is a 50% combustion point) during MBT control with respect to the air-fuel ratio in the vicinity of the lean limit. FIG. 5 is a diagram showing the relationship between the air-fuel ratio at the time of the lean limit and the ignition timing.

  As shown in the graph relating to MBT in FIG. 4, the ignition timing at which MBT occurs varies according to the air-fuel ratio. This is because the combustion speed changes according to the change in the air-fuel ratio. More specifically, when the air-fuel ratio becomes lean, combustion is delayed. As a result, since it is necessary to ignite earlier, the MBT changes to the advance timing. In particular, in the lean air-fuel ratio region in the vicinity of the lean limit, the optimal ignition timing changes even with a minute change in the air-fuel ratio. On the other hand, the CA50 when MBT is obtained is substantially constant at the air-fuel ratio near the lean limit, as shown in the graph relating to CA50 in FIG.

  When the fuel injection amount is adjusted so that the difference between the target SA-CA10 and the actual SA-CA10 becomes zero by the feedback control of the fuel injection amount using the SA-CA10 in the first embodiment described above, the air-fuel ratio becomes smaller. Change. More specifically, when this feedback control is executed, as illustrated in the graph relating to MBT in FIG. 4, the air-fuel ratio varies with a certain fluctuation width with respect to the air-fuel ratio corresponding to a certain target SA-CA10. As a result, the MBT also fluctuates with a certain amplitude. On the other hand, the air-fuel ratio at the time of the lean limit changes under the influence of the ignition timing as shown in FIG. Accordingly, if the MBT has changed due to the change in the air-fuel ratio accompanying the control of the fuel injection amount using the SA-CA10, but the ignition timing remains fixed at the MBT before the change, this ignition timing is As a result, it deviates from the true MBT corresponding to the current air-fuel ratio. For example, if the ignition timing remains fixed in the MBT before the change even though the MBT has changed to the advance side, the current ignition timing becomes the timing on the retard side with respect to the true MBT, From the relationship shown in FIG. 5, the air-fuel ratio at the lean limit becomes richer than when the ignition timing is controlled to true MBT. As a result, there is a concern that misfire may occur when the air-fuel ratio fluctuates to a lean value by feedback control of the fuel injection amount using the SA-CA10.

  From the above, when the feedback control of the fuel injection amount using the SA-CA10 is performed, the ignition timing control for eliminating the influence of the change in the MBT due to the change in the air-fuel ratio accompanying the execution of the feedback control is performed. It can be said that this is preferably performed for each cylinder. Therefore, in this embodiment, in addition to the feedback control of the fuel injection amount using the SA-CA10, the ignition timing feedback control using the CA50 is cooperatively performed in order to eliminate the influence of the MBT change.

  As described above with reference to the graph relating to CA50 in FIG. 4, the CA50 when MBT is obtained does not substantially change with respect to the air-fuel ratio in the vicinity of the lean limit. Therefore, assuming that the CA50 when MBT is obtained is the target CA50 (target combustion center of gravity position), there is no difference between the CA50 obtained from the analysis result of the in-cylinder pressure data (hereinafter referred to as “actual CA50”) and the target CA50. By correcting the ignition timing, the ignition timing can be adjusted to MBT without being affected by the above-described change in the air-fuel ratio. Thus, it can be said that the use of CA50 is suitable for controlling the ignition timing in this case. Note that the ignition timing control using the CA50 here is not necessarily limited to control to obtain MBT. That is, the ignition timing control using the CA50 is used by setting the target CA50 according to the ignition efficiency described later even when an ignition timing other than the MBT is set as the target ignition timing as in the so-called retarded combustion. can do.

(Set the execution order and response speed of the two feedback controls)
In this embodiment, the feedback control of the fuel injection amount using the SA-CA10 is not freely performed, but the difference between the target CA50 and the actual CA50 becomes a predetermined value or less by the feedback control of the ignition timing using the CA50. In this state, the feedback control of the fuel injection amount using the SA-CA10 is performed.

  Further, in the present embodiment, the control is configured such that the response speed of the feedback control of the ignition timing using the CA50 is higher than the response speed of the feedback control of the fuel injection amount using the SA-CA10.

(Outline of feedback control of Embodiment 1)
FIG. 6 is a block diagram for explaining an overview of feedback control using SA-CA 10 and feedback control using CA 50 according to Embodiment 1 of the present invention.

  In the system according to the first embodiment of the present invention, the ECU 40 performs engine control such as fuel injection control and ignition control as described above as a premise of each feedback control shown in FIG. In fuel injection control, the basic injection amount corresponding to the operating state (specifically, engine speed and engine load factor) is corrected with an injection amount correction value indicating an increase / decrease correction amount, and each cycle is changed for each cylinder. The fuel injection amount is determined and injected into the fuel injection device 26 at a predetermined timing. In the ignition control, the basic ignition timing corresponding to the operating state is corrected with the ignition timing correction value indicating the advance / retard angle correction amount, and the ignition timing of each cycle is determined for each cylinder, and the determined ignition timing is determined. The ignition device 28 is ignited.

  In FIG. 6, the feedback control using SA-CA10 is performed so that the difference between the predetermined target SA-CA10 near the lean limit and the actual SA-CA10 becomes zero (that is, the actual SA-CA10 is the target SA-CA10). The fuel injection amount of the next cycle is adjusted by adjusting the injection amount correction value so that the fuel injection amount coincides with In the feedback control using the CA50, the ignition timing correction value is adjusted so that the difference between the target CA50 and the actual CA50 becomes zero (that is, the actual CA50 matches the target CA50). The time is adjusted.

  In feedback control using SA-CA10, as shown in FIG. 6, a target SA-CA10 is set according to the engine operating state (specifically, the engine speed and the engine load factor). The actual SA-CA10 here is a crank angle period from the ignition timing to CA10 obtained from an analysis result of in-cylinder pressure data obtained using the in-cylinder pressure sensor (CPS) 30 and the crank angle sensor 42. This is a calculated value. The actual SA-CA10 is calculated for each cycle in each cylinder.

  In feedback control using SA-CA10, PI control is used as an example to adjust the fuel injection amount so that there is no difference between target SA-CA10 and actual SA-CA10. In this PI control, the difference between the target SA-CA10 and the actual SA-CA10 and a predetermined PI gain (proportional term gain and integral term gain) are used, and the injection amount according to the difference and the magnitude of the integrated value. A correction value is calculated. The injection amount correction value calculated for each cylinder is reflected in the fuel injection amount of the target cylinder. Thus, the fuel injection amount supplied to each cylinder of the internal combustion engine (ENG) 10 is adjusted (corrected) by the feedback control.

  In feedback control using CA50, PI control is used as an example for feedback control using CA50 in order to correct the ignition timing so that there is no difference between target CA50 and actual CA50. In this PI control, using the difference between the target CA50 and the actual CA50 and a predetermined PI gain (proportional term gain and integral term gain), the ignition timing correction value according to the difference and the integrated value of the difference. Is calculated. The ignition timing correction value calculated for each cylinder is reflected in the ignition timing of the target cylinder. Thereby, the ignition timing in each cylinder of the internal combustion engine (ENG) 10 is adjusted (corrected) by the feedback control.

  In the present embodiment, in order to make the response speed of the feedback control of the ignition timing using the CA50 higher than the response speed of the feedback control of the fuel injection amount using the SA-CA10, these feedback controls are performed. The following consideration is given to the PI gain used in. That is, the PI gain used in the feedback control using CA50 is set to a larger value than the PI gain used in the feedback control using SA-CA10.

(Specific processing of feedback control of Embodiment 1)
FIG. 7 is a flowchart showing a control routine executed by the ECU 40 in order to realize feedback control using the SA-CA 10 and feedback control using the CA 50 according to Embodiment 1 of the present invention. Note that this routine is repeatedly executed for each cycle at a predetermined timing after the end of combustion in each cylinder.

  In the routine shown in FIG. 7, the ECU 40 first determines whether or not the lean burn operation is being performed (step 100). In the internal combustion engine 10, a lean burn operation is performed at an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a predetermined operating region. Here, it is determined whether or not it corresponds to an operation region in which such lean burn operation is performed.

  If it is determined in step 100 that the lean burn operation is being performed, the engine speed and the engine load factor are acquired using the crank angle sensor 42 and the air flow meter 44 (step 102). The engine load factor can be calculated based on the engine speed and the intake air amount.

  Next, the ECU 40 acquires the target ignition efficiency (step 104). The target ignition efficiency is an index indicating a maximum value when the ignition timing is MBT and indicating a degree of deviation of the target ignition timing from MBT. The ECU 40 stores a map (not shown) in which the target ignition efficiency is determined according to the operating conditions of the internal combustion engine 10, and in this step 104, the target ignition efficiency is acquired with reference to such a map.

  Next, the ECU 40 calculates a target CA50 (step 106). The target CA50 is set based not only on the engine rotation speed and engine load factor acquired in step 102 but also on the target ignition efficiency acquired in step 104. More specifically, when the target ignition efficiency is 1, that is, when MBT is set as the target ignition timing, CA50 when MBT is obtained is used as target CA50. Further, when the target ignition efficiency is a predetermined value smaller than 1, that is, when the target ignition timing is a predetermined timing on the advance side or the retard side with respect to MBT, the time when the predetermined timing is obtained CA50 is used as the target CA50.

  Next, the ECU 40 acquires in-cylinder pressure data measured during combustion using the in-cylinder pressure sensor 30 and the crank angle sensor 42 (step 108).

  Next, after acquiring the in-cylinder pressure data in step 108, the ECU 40 calculates the actual CA 50 using the analysis result of the acquired in-cylinder pressure data (step 110).

  Next, the ECU 40 calculates the difference between the target CA50 calculated in step 106 and step 110 and the actual CA50 (step 112).

  Next, the ECU 40 uses the difference calculated in step 112 and a predetermined PI gain (proportional term gain and integral term gain) to calculate an ignition timing correction value according to the difference and the magnitude of the integrated value. (Step 114). As described above, the PI gain used in the feedback control using CA50 is set to a larger value than the PI gain used in the feedback control using SA-CA10.

  Next, the ECU 40 corrects the ignition timing used in the next cycle based on the ignition timing correction value calculated in step 114 (step 116). Specifically, there is a substantially one-to-one relationship between the CA50 and the ignition timing. For example, when the actual CA50 is larger than the target CA50 (that is, the actual CA50 is retarded than the target CA50). ), The ignition timing is advanced in order to accelerate combustion.

  Next, the ECU 40 determines whether or not the difference (absolute value) between the target CA50 and the actual CA50 is equal to or less than a predetermined value (step 118). As a result, when it is determined that the difference is not less than the predetermined value, that is, when it can be determined that the actual CA50 has not sufficiently converged in the vicinity of the target CA50 by the ignition timing feedback control using the CA50, the ECU 40 Terminates this routine and starts the routine again in the next cycle of the same cylinder. That is, in the cycle in which the determination in step 118 is not established, the fuel injection amount feedback control using the SA-CA 10 is not executed.

  On the other hand, when the determination in step 118 is satisfied, that is, when it can be determined that the actual CA50 has sufficiently converged in the vicinity of the target CA50 by feedback control of the ignition timing using the CA50, the ECU 40 determines that the SA− In order to execute the feedback control of the fuel injection amount using the CA 10, the subroutine processing shown in FIG. 8 is executed.

  FIG. 8 is a flowchart showing a subroutine executed by the ECU 40 in order to realize feedback control using the SA-CA 10 according to Embodiment 1 of the present invention.

  In the routine shown in FIG. 8, the ECU 40 first calculates the target SA-CA10 (step 120). Target SA-CA10 is set as a value based not only on the engine speed and engine load factor but also on the target ignition efficiency acquired in step 106. More specifically, the reference value of the target SA-CA10 is set as a value when an MBT set based on the engine rotation speed and the engine load factor is assumed. The final target SA-CA10 is set according to the target ignition efficiency (that is, according to the deviation amount of the target ignition timing from the MBT). More specifically, the final target SA-CA10 is set such that the larger the retard amount of the ignition timing with respect to the MBT, the smaller the reference value, and conversely, the ignition timing with respect to the MBT. The larger the advance amount, the larger the value relative to the reference value.

  Next, the ECU 40 calculates the actual SA-CA10 (step 122). The actual SA-CA10 is calculated as a crank angle period from the ignition timing in the current cycle to CA10 obtained as an analysis result of the in-cylinder pressure data acquired in step 108.

  Next, the ECU 40 calculates the difference between the target SA-CA10 calculated in step 120 and step 122 and the actual SA-CA10 (step 124).

  Next, the ECU 40 uses the difference calculated in step 124 and a predetermined PI gain (proportional term gain and integral term gain) to calculate an injection amount correction value corresponding to the difference and the magnitude of the integrated value. (Step 126).

  Next, the ECU 40 corrects the fuel injection amount used in the next cycle based on the calculated injection amount correction value (step 128). Specifically, for example, when the actual SA-CA10 is larger than the target SA-CA10, the air-fuel ratio is shifted to the lean side from the target value due to the relationship shown in the graph regarding the SA-CA10 in FIG. Therefore, the fuel injection amount is increased with respect to the basic injection amount in order to perform rich correction of the air-fuel ratio.

  According to the routines shown in FIGS. 7 and 8 described above, the feedback control of the ignition timing using the CA50 and the feedback control of the fuel injection amount using the SA-CA10 are performed in a coordinated manner. According to this feedback control of the ignition timing, the value of the time when the MBT is obtained is utilized by utilizing the characteristic of the CA50 that hardly changes depending on the air-fuel ratio in the vicinity of the lean limit (that is, the relationship between the MBT and the air-fuel ratio is determined by the ignition timing). The ignition timing can be appropriately controlled to true MBT (without the need for consideration for control). Then, by executing feedback control of the fuel injection amount using SA-CA10 with the ignition timing controlled to MBT, the SA-CA10 having linearity with respect to the air-fuel ratio in the vicinity of the lean limit is executed. Using the characteristics, the air-fuel ratio can be suitably controlled near the lean limit during the lean burn operation.

[Characteristic Control in Embodiment 1]
(Control of ignition timing and fuel injection amount according to abnormal types of control parameters)
By the way, although noise is added to the output signal of the in-cylinder pressure sensor 30, the lower the in-cylinder pressure is, the smaller the sensor output signal is and the greater the noise is. It will be high. Further, CA10 whose ignition timing is close is more susceptible to the ignition timing than CA50. Therefore, when the actual SA-CA10 calculated based on the detection value of the in-cylinder pressure sensor 30 is compared with the actual CA50, it can be said that the actual CA50 is a more robust control parameter.

  When an abnormality occurs in the control parameter based on the detection value of the in-cylinder pressure sensor 30, the ignition timing and the fuel injection amount are erroneously corrected by the above-described two feedback controls, and on the contrary, fuel consumption deterioration, emission increase, drivability deterioration, etc. There is a risk of causing it. Therefore, it is necessary to determine the control parameter abnormality and perform appropriate control.

  However, if abnormality determination is performed for each of the real CA 50 and the real SA-CA 10, processing according to the combination of abnormality types is required, the processing becomes complicated, and the calculation load increases. Further, if the abnormality determination is performed only for the real CA50, even if the real SA-CA10 is abnormal, if the real CA50 is normal, it is determined as normal as a whole. As a result, the abnormality of the actual SA-CA10 that is a control parameter with low robustness is overlooked, and the fuel injection amount feedback control using the SA-CA10 is executed, so that the fuel injection amount is erroneously corrected, and on the contrary, the fuel consumption There is a risk of causing deterioration or the like.

  On the other hand, if the abnormality determination is performed for only the real SA-CA10, the real CA50 having high robustness is normal when the real SA-CA10 is normal, and the real CA50 is normal / normal when the real SA-CA10 is abnormal. Although it is one of abnormalities, if at least SA-CA10 is abnormal, CA50 is not overlooked if CA50 is also considered abnormal. Also, the calculation load can be kept low.

  Therefore, in the system of the present embodiment, abnormality determination is performed only for the real SA-CA10, and when the real SA-CA10 is abnormal, not only feedback control using the SA-CA10 but also feedback control using the CA50 is performed. It will be stopped.

  On the other hand, when the feedback control is stopped together with the abnormality detection of the actual SA-CA10, the state in which the correction amount is optimized by the feedback control is canceled. Response at the time of feedback stop is important because it leads to deterioration of fuel consumption, emission and drivability. Therefore, in the system of the present embodiment, an attempt is made to leave the effect of feedback control as much as possible according to the state of the control parameter.

  In the following description, the ignition timing feedback control using the CA50 is also referred to as “CA50FB control”, and the fuel injection amount feedback control using the SA-CA10 is also referred to as “SA-CA10FB control”.

  FIG. 9 is a diagram showing a list of correspondence control in the present embodiment. If the correspondence control in this embodiment is classified, it is classified into two, A and B.

  In the correspondence control A, both CA50FB control and SA-CA10FB control are stopped. Then, the ignition timing correction value indicating the correction amount for correcting the basic ignition timing of the next cycle is held as the previous value. Similarly, the injection amount correction value indicating the correction amount for correcting the basic injection amount of the next cycle is also held as the previous value. Note that an average value in the most recent cycle may be used instead of the previous value.

  In the response control B, both CA50FB control and SA-CA10FB control are stopped. The ignition timing correction value is set to a value closer to zero than the previous value. Similarly, the injection amount correction value is also set to a value closer to zero than the previous value.

  FIG. 10 is a diagram for explaining a combination of a control parameter abnormality type, a control parameter (SA-CA10) abnormality type, and corresponding control. As shown in FIG. 10, the types of abnormalities include continuous abnormalities and short-term abnormalities.

  The continuation abnormality refers to a state in which a situation in which the control parameter exceeds a predetermined range set to about the parameter fluctuation range occurs continuously for a set number of cycles or more. For example, ± 3σ may be used as the predetermined range. Although the standard deviation σ can be calculated during operation, since data of several hundred cycles is required, a map that predetermines the relationship between the engine speed and the engine load factor and a predetermined range is stored in the ECU 40. It is desirable to keep it. The number of set cycles is, for example, 5 to 10 cycles (at 1200 rpm to 1500 rpm), and may be changed according to the operating state. Moreover, a short-term abnormality refers to a state in which a situation in which the control parameter exceeds the above-described predetermined range continuously occurs for less than 1 to the set number of cycles.

  If the actual SA-CA10 is abnormal (whether it is a short-term abnormality or a continuation abnormality), any one of the above-described corresponding controls A and B is executed, and not only the SA-CA10FB control but also the CA50FB control is stopped. . As a result, the fuel injection amount is erroneously corrected by the SA-CA10FB control, and on the contrary, it is possible to avoid the deterioration of fuel consumption, the increase of emissions, the deterioration of drivability, and the like.

(About correspondence control A)
When the real SA-CA10 is a short-term abnormality, the real CA50 having high robustness is considered normal or a short-term abnormality, and the response control A is executed. In the corresponding control A, the actual SA-CA10 (and the actual CA50), which is a short-term abnormality, is expected to return to the normal value thereafter, so that the ignition timing correction value and the injection amount correction value are respectively the previous value or the average in the most recent cycle Held in value.

(About correspondence control B)
When the actual CA-CA10 is a continuation abnormality, the real CA50 may also be a continuation abnormality, so the response control B is executed. In response control B, in order to suppress further deterioration in combustion, the ignition timing correction value and the injection amount correction value are each set to a value closer to zero than the previous value.

  Preferably, in the corresponding control B, the amount of change in which each of the ignition timing correction value and the injection amount correction value approaches zero is greater than the case where the previous value of each correction value indicates a decrease correction, as compared to the case where the increase correction is indicated. Many are set.

  More specifically, when the actual SA-CA10 is a continuation abnormality and the previous value of the injection amount correction value indicates a decrease correction, the ignition timing correction value and the injection amount correction value are set to zero, respectively. (Correspondence control B-1). As a result, the fuel injection amount is not corrected to decrease, and the fuel injection amount of the next cycle is injected at the basic injection amount, so that the air-fuel ratio is enriched compared to the previous cycle, and misfire can be avoided.

  On the other hand, when the actual CA50 is a continuation abnormality and the previous value of the injection amount correction value indicates an increase correction, the ignition timing correction value and the injection amount correction value are set to values closer to zero than the previous value, respectively. The correction amount is gradually decreased for each cycle (corresponding control B-2). The continuation abnormality during the increase correction is thought to be due to the deterioration of fuel consumption and emission, but if the correction amount is set to zero immediately, there is a risk of misfire due to significant leaning, so engine torque can be reduced by gradually reducing the correction amount. While checking, make the correction amount close to zero. In this case, when the engine torque analogy means (torque meter or crank angular velocity) is used and the generated torque becomes equal to or less than a predetermined value (a value indicating a torque decrease that causes deterioration in drivability), or the torque fluctuation becomes equal to or greater than a predetermined value. In such a case, or when the crank angular speed fluctuation becomes a predetermined value or more, it is desirable to stop the reduction of the correction amount.

  As described above, in the system according to the present embodiment, the CA50 abnormality determination is not performed, and only the SA-CA10 abnormality determination is performed. Therefore, the calculation load can be reduced. Further, when there is an abnormality in the value of SA-CA10 and both feedback controls are stopped, by executing appropriate response control according to the continuation state of the abnormality of the control parameter, CA50FB control and The effect of adjusting the ignition timing correction value and the injection amount correction value by the SA-CA10FB control can be left, and fuel consumption deterioration / emission deterioration and drivability deterioration can be suppressed.

(flowchart)
FIG. 11 shows a control routine executed by the ECU 40 in order to realize appropriate ignition timing control and fuel injection control when an abnormality occurs in the control parameter (SA-CA10) in the first embodiment of the present invention. It is a flowchart. Note that this routine is repeatedly executed for each cycle at a predetermined timing after the end of combustion in each cylinder.

  In the routine shown in FIG. 11, the ECU 40 first determines whether or not the actual SA-CA 10 is normal (step 200). The ECU 40 determines whether or not the actual SA-CA10 obtained from the analysis result of the in-cylinder pressure data in the current cycle is outside a predetermined range. As the predetermined range, a predetermined fluctuation range determined based on experiments or the like is set. It is conceivable to use ± 3σ as an index for determining a predetermined fluctuation range. Although the standard deviation σ can be calculated during operation, since data of several hundred cycles is required, a map that predetermines the relationship between the engine speed and the engine load factor and a predetermined range is stored in the ECU 40. Let me.

  When it is determined in step 200 that the actual SA-CA10 is normal, that is, when the actual SA-CA10 and the actual CA50 are normal, the ECU 40 executes the CA40FB control and the SA-CA10FB control as usual ( Step 202).

  On the other hand, when it is determined in step 200 that the actual SA-CA10 is abnormal, the ECU 40 determines whether or not the actual SA-CA10 abnormality continues for a predetermined number of times (step 204). The predetermined number of times is, for example, 5 to 10 cycles (at 1200 rpm to 1500 rpm), and may be changed according to the operating state.

  When it is determined in step 204 that the abnormality of the actual CA 50 has not continued for a predetermined number of times (short-term abnormality), the ECU 40 executes a control routine of process A corresponding to the above-described response control A.

  FIG. 12 is a flowchart showing a control routine of the process A executed by the ECU 40 in the first embodiment of the present invention. In the routine of process A, the ECU 40 stops the execution of the CA50FB control and stops the adjustment of the ignition timing correction value by the CA50FB control (step A10). Next, the ECU 40 sets the ignition timing correction value to the previous value or the average value in the most recent cycle (step A12). Further, the ECU 40 stops the execution of the SA-CA10FB control and stops the adjustment of the injection amount correction value by the SA-CA10FB control (step A14). Next, the ECU 40 sets the injection amount correction value to the previous value or the average value in the most recent cycle (step A16). Thereafter, the routine returns to FIG. Note that steps A14 and A16 may be executed before steps A10 and A12.

  If it is determined in step 204 in FIG. 11 that the abnormality of the actual CA 50 has continued for a predetermined number of times (continuation abnormality), the ECU 40 determines that the previous value of the injection amount correction value or the average value of the most recent cycle is the reduction correction. It is determined whether or not the value is indicated (step 206).

  When it is determined in step 206 that the value indicates a decrease correction, the ECU 40 executes a control routine of a process B-1 corresponding to the above-described corresponding control B-1.

  FIG. 13 is a flowchart showing a control routine of process B-1 executed by ECU 40 in the first embodiment of the present invention. In the routine of process B-1, the ECU 40 stops the execution of the CA50FB control and stops the adjustment of the ignition timing correction value by the CA50FB control (step B10). Next, the ECU 40 changes the ignition timing correction value to zero (step B12). Further, the ECU 40 stops the execution of the SA-CA10FB control and stops the adjustment of the injection amount correction value by the SA-CA10FB control (step B14). Next, the ECU 40 changes the injection amount correction value to zero (step B16). Thereafter, the routine returns to FIG. Note that steps B14 and B16 may be executed before steps B10 and B12.

  If it is determined in step 206 in FIG. 11 that the value is not a value indicating the weight reduction correction, the ECU 40 executes a control routine of a process B-2 corresponding to the above-described corresponding control B-2.

  FIG. 14 is a flowchart showing a control routine of process B-2 executed by ECU 40 in the first embodiment of the present invention. In the routine of process B-2, the ECU 40 stops the execution of the CA50FB control and stops the adjustment of the ignition timing correction value by the CA50FB control (step B20). Next, the ECU 40 changes the ignition timing correction value to a value closer to zero than the previous value (step B22). Specifically, the correction amount for the basic ignition timing is gradually reduced each time this routine is executed, and the ignition timing correction value is changed so as to become zero after a predetermined cycle. Further, the ECU 40 stops the execution of the SA-CA10FB control and stops the adjustment of the injection amount correction value by the SA-CA10FB control (step B24). Next, the ECU 40 changes the basic injection amount to a value closer to zero than the previous value, as the injection amount correction value (step B26). Specifically, the correction amount for the basic injection amount is gradually reduced each time this routine is executed, and the injection amount correction value is changed so as to become zero after a predetermined cycle. Thereafter, the routine returns to FIG. Note that steps B24 and B26 may be executed before steps B20 and B22.

  As described above, according to the routine shown in FIG. 11 and the subroutine shown in FIGS. 12 to 14, when there is an abnormality in the value of the control parameter (SA-CA10) and the feedback control is stopped, the control parameter The ignition timing correction value and the injection amount correction value can be set so as to retain the effect of each feedback control as much as possible according to the abnormal continuation state. In addition, when the control parameter returns to the normal range, each feedback control can be resumed using these ignition timing correction value and injection amount correction value, and the ignition timing and fuel injection amount converge to the target value at an early stage. Can be made.

  By the way, in Embodiment 1 mentioned above, it is supposed that CA10 which is a 10% combustion point is used as a predetermined | prescribed crank angle which prescribes | regulates a crank angle period between ignition timings. However, the combustion point in the present invention is not limited to CA10, and may be CAα which is a crank angle when a combustion mass ratio (α%) lower than the combustion center of gravity is obtained. In addition, it can be said that the use of CA10 is preferable to the use of other combustion points for the following reasons. That is, when the combustion point in the main combustion period (CA10-CA90) after CA10 is used, the obtained crank angle period is a parameter (EGR rate, intake air temperature and intake temperature) that affects combustion when the flame spreads. Greatly affected by the tumble ratio). That is, the crank angle period obtained in this case is not purely focused on the air-fuel ratio, and is weak against disturbance. In order to eliminate the influence of such disturbance, the configuration in which the crank angle period is corrected in accordance with the above parameters increases the number of man-hours for adaptation. On the other hand, when the combustion point in the initial combustion period (CA0-CA10) is used, the obtained crank angle period is not easily influenced by the above parameters, and the influence of the factors affecting the ignition appears well. It becomes. As a result, controllability is improved. On the other hand, the combustion start point (CA0) and the combustion end point (CA100) are likely to have errors due to the influence of noise superimposed on the output signal from the in-cylinder pressure sensor 30 acquired by the ECU 40. The influence of this noise decreases as the distance from the combustion start point (CA0) or combustion end point (CA100) increases. Therefore, when considering noise resistance and reduction of the number of man-hours, it can be said that the CA10 is the most excellent as used in this embodiment.

  Note that if it is assumed that the ignition timing is unlikely to deviate between the indicated value and the actual value, the actual SA-CA10 abnormality may be regarded as the CA10 abnormality.

  FIG. 15 is a block diagram of an internal combustion engine control apparatus according to the present invention. In the block showing the ECU 40, some of the various processes provided in the ECU 40 are represented by blocks. Computing resources are allocated to each of these blocks. A program corresponding to each block is prepared in the memory in the ECU 40, and the processing of each block is realized in the ECU 40 by executing them by the processor.

  The correspondence relationship between the various types of processing described in Embodiment 1 and the present invention will be described with reference to FIG. The in-cylinder pressure sensor 30 corresponds to “in-cylinder pressure detection means” in the present invention, and the rank angle sensor 42 corresponds to “crank angle detection means” in the present invention. The above-described fuel injection control and ignition control executed by the ECU 40 correspond to the “fuel injection amount determining means” and the “ignition timing determining means” in the present invention, respectively.

  Further, when the ECU 40 executes the process of step 110, the “combustion mass ratio calculating means” and the “combustion gravity center position calculating means” in the present invention execute the processes of the above steps 102 to 116. When the “ignition timing adjusting means” in the engine executes the process in step 122, the “crank angle period calculating means” in the present invention executes the processes in steps 120 to 128 in the present invention. The “adjusting means” executes the processing of step 200 described above, thereby realizing “crank angle period abnormality determining means” in the present invention. Further, the ECU 40 executes at least one of the corresponding controls A and B described above, thereby realizing the “stop unit” and the “correction value setting unit” in the present invention.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Piston 14 Combustion chamber 16 Intake passage 18 Exhaust passage 20 Intake valve 22 Exhaust valve 24 Throttle valve 26 Fuel injection device 28 Ignition device 30 In-cylinder pressure sensor 40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 Air flow meter

Claims (1)

In-cylinder pressure detecting means for detecting in-cylinder pressure;
Crank angle detecting means for detecting the crank angle;
Combustion mass ratio calculating means for calculating a combustion mass ratio based on the detected in-cylinder pressure and the detected crank angle;
Ignition timing determination means for determining the ignition timing by correcting the basic ignition timing according to the operating state with the ignition timing correction value;
Combustion center-of-gravity position calculating means for calculating a combustion center-of-gravity position based on the calculated combustion mass ratio;
Ignition timing adjustment means for adjusting the ignition timing correction value so that the calculated combustion center of gravity position coincides with the target combustion center of gravity position corresponding to the target ignition efficiency;
Fuel injection amount determination means for determining the fuel injection amount by correcting the basic injection amount according to the operating state with the injection amount correction value;
A crank angle period calculating means for calculating a crank angle period from an ignition timing to a crank angle at a predetermined combustion mass ratio lower than the combustion center of gravity;
Injection amount adjusting means for adjusting the injection amount correction value so that the calculated crank angle period coincides with the target crank angle period;
Crank angle period abnormality determining means for determining whether or not the calculated crank angle period is abnormal;
Stop means for stopping adjustment by the ignition timing adjusting means and the injection amount adjusting means when it is determined that the calculated crank angle period is abnormal;
When it is determined that the calculated crank angle period is abnormal, the ignition timing correction value and the injection amount correction value are set to the previous value, the average value in the most recent cycle, or a value closer to zero than the previous value, respectively. Correction value setting means to perform,
A control device for an internal combustion engine, comprising:

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