JP2017166389A - Controller of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform ignition timing control while suppressing over-retardation of ignition timing, when retardation of ignition timing is requested.SOLUTION: A controller of an internal combustion engine is configured to: calculate, based on an output value of an in-cylinder pressure sensor, an actual combustion timing index value S106; calculate, based on the calculated actual combustion timing index value, an actual combustion timing index value in MBT as an actual value of a combustion timing index value that would be obtained if the internal combustion engine was operated at MBT ignition timing S108; and control ignition timing so that the difference between the actual combustion timing index value in MBT and a target combustion timing index value in MBT, which is a target value of a CA 50 when ignition is performed at the MBT ignition timing, is made small S118.SELECTED DRAWING: Figure 3

Description

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

  For example, Patent Document 1 discloses a control device for a spark ignition type internal combustion engine. In this control device, the following ignition timing control is executed in order to bring the ignition timing closer to the MBT ignition timing during steady operation in which both changes in the engine speed and the engine load are equal to or less than a predetermined value. That is, the ignition timing is feedback-controlled so that the crank angle when the combustion ratio is at the reference combustion ratio (50%) coincides with the 50% combustion point determined corresponding to the MBT ignition timing.

JP 2008-025406 A JP 2006-029084 A

  During engine operation, the ignition timing may be retarded for the purpose of suppressing knocking or suppressing engine torque. In the system described in Patent Document 1, when there is such a retardation request, the above-described ignition timing feedback control cannot be executed. For this reason, there is a possibility that the ignition timing is retarded excessively when trying to satisfy the retardation request. As a result, misfire may easily occur. In particular, during lean burn operation at an air / fuel ratio leaner than the stoichiometric air / fuel ratio, combustion tends to become unstable compared to during stoichiometric air / fuel ratio operation. For this reason, during lean burn operation, misfire is more likely to occur due to a small retardation of the ignition timing than during stoichiometric air-fuel ratio operation.

  The present invention has been made to solve the above-described problems, and is an internal combustion engine that can perform ignition timing control while suppressing over-retarding of the ignition timing when there is a request for retarding the ignition timing. An object is to provide a control device.

  An internal combustion engine control apparatus according to the present invention controls an internal combustion engine including an ignition device that ignites an air-fuel mixture in a cylinder and an in-cylinder pressure sensor that detects an in-cylinder pressure. The control device includes first calculation means, second calculation means, and ignition timing control means. The first calculation means calculates an actual combustion timing index value that is an actual value of the combustion timing index value based on the output value of the in-cylinder pressure sensor. The second calculating means is based on the calculated actual combustion timing index value, and the actual MBT time which is the actual value of the combustion timing index value that would have been obtained if operated at the MBT ignition timing. A combustion timing index value is calculated. The ignition timing control means reduces a difference between the actual MBT combustion timing index value and a target MBT combustion timing index value that is a target value of the combustion timing index value when ignition is performed at the MBT ignition timing. The ignition timing is controlled as follows.

  According to the present invention, based on the actual combustion timing index value calculated based on the output of the in-cylinder pressure sensor, the actual value of the combustion timing index value that would have been obtained if operated at the MBT ignition timing. An actual MBT combustion timing index value is calculated. The ignition timing is controlled so that the difference between the actual MBT combustion timing index value and the target MBT combustion timing index value, which is the target value of the combustion timing index value when ignition is performed at the MBT ignition timing, is reduced. Is done. By performing such control even when there is a request for retarding the ignition timing such as knock suppression, the ignition timing can be controlled while suppressing the excessive retard of the ignition timing.

It is a figure for demonstrating schematically the system configuration | structure of Embodiment 1 of this invention. It is a figure showing the waveform of the combustion mass ratio. It is a flowchart which shows the routine performed in order to calculate the retard amount AMBT of ignition timing. It is a flowchart which shows the routine performed in order to calculate target ignition timing. It is a figure for demonstrating the setting method of the correction coefficient K. FIG. It is a time chart for demonstrating operation | movement when control of Embodiment 2 of this invention is performed.

Embodiment 1 FIG.
[System configuration of the first embodiment]
FIG. 1 is a diagram for schematically explaining a system configuration according to the first embodiment of the present invention. An internal combustion engine 10 shown in FIG. 1 is a spark ignition engine (a gasoline engine as an example), which is mounted on a vehicle and used as a power source. An intake passage 12 and an exhaust passage 14 communicate with each cylinder of the internal combustion engine 10.

  An air cleaner 16 is provided near the inlet of the intake passage 12. The air cleaner 16 is provided with an air flow meter 18 that outputs a signal corresponding to the flow rate of the air taken into the intake passage 12. A compressor 20 a of the turbocharger 20 is disposed in the intake passage 12 on the downstream side of the air cleaner 16. The compressor 20 a is driven by a turbine 20 b disposed in the exhaust passage 14. An electronically controlled throttle valve 22 that opens and closes the intake passage 12 is disposed in the intake passage 12 on the downstream side of the compressor 20a.

  Each cylinder is provided with a fuel injection valve (for example, an in-cylinder injection valve) 26 for supplying fuel into the combustion chamber 24 and an ignition plug 28 for igniting the air-fuel mixture in the combustion chamber 24. Each cylinder is provided with an in-cylinder pressure sensor 30 for detecting the in-cylinder pressure.

  Furthermore, the system of this embodiment includes an electronic control unit (ECU) 40 and a drive circuit (not shown) for driving the following various actuators as a control device for controlling the internal combustion engine 10. In addition to the air flow meter 18 and the in-cylinder pressure sensor 30 described above, the ECU 40 is electrically connected to various sensors for acquiring the engine operating state such as a crank angle sensor 42 for detecting the crank angle. The ECU 40 is connected to an accelerator position sensor 44 for detecting the amount of depression of the accelerator pedal (accelerator opening) of the vehicle. Further, the ECU 40 is electrically connected to various actuators for controlling engine operation such as the throttle valve 22, the fuel injection valve 26, and the ignition device (not shown) using the spark plug 28. .

[Ignition timing control]
In the ignition timing control of the internal combustion engine 10, the target ignition timing is calculated. The target ignition timing is calculated as the sum of the base ignition timing ABSE based on the engine load and the engine speed and various correction amounts. Examples of various correction amounts (retard amount) include retard amounts AMBT, ATQ, and AKCS. The retard amount AMBT is basically a retard amount used to bring the ignition timing closer to the MBT ignition timing. The retard amounts ATQ and AKCS are retard amounts set when there is a request for retarding the ignition timing. More specifically, the retard amount ATQ is an ignition timing retard amount for suppressing engine torque (more specifically, a retard amount when there is a request to quickly suppress the generated torque). The quantity AKCS is a retardation amount for knock suppression.

ただし、上記（１）式において、θ_ｍｉｎは燃焼開始点であり、θ_ｍａｘは燃焼終了点である。 FIG. 2 is a diagram showing a waveform of the combustion mass ratio. According to the system of the present embodiment including the in-cylinder pressure sensor 30 and the crank angle sensor 42, it is possible to acquire actually measured data of the in-cylinder pressure in synchronization with the crank angle in each cycle of the internal combustion engine 10. The in-cylinder heat generation amount Q at an arbitrary crank angle θ can be calculated using the actually measured data of the in-cylinder pressure and the first law of thermodynamics. Then, the combustion mass ratio (hereinafter referred to as “MFB”) at an arbitrary crank angle θ is calculated according to the following equation (1) using the calculated actual heat generation amount Q in the cylinder. it can. In addition, by executing the MFB calculation process for each predetermined crank angle, it is possible to calculate measured data of the MFB in synchronization with the crank angle. FIG. 2 shows an example of the waveform of such measured data of MFB.

However, in the above equation (1), θ _min is the combustion start point, and θ _max is the combustion end point.

  As described above, when the MFB actual measurement data is obtained, the crank angle when the MFB becomes a specific ratio can be calculated. In the present embodiment, the crank angle (combustion center of gravity) when the MFB is 50% is referred to as “CA50”. The CA 50 is used for ignition timing control as described below.

  In this embodiment, in order to continue appropriate feedback control of the ignition timing even when there is a request for retarding the ignition timing, ignition according to the routine processing shown in FIGS. 3 and 4 described below is performed. Timing control is executed. That is, the following processing is executed regardless of whether or not there is a request for retarding the ignition timing.

  FIG. 3 is a flowchart showing a routine that is executed to calculate the retard amount AMBT of the ignition timing. FIG. 4 is a flowchart showing a routine executed for calculating the target ignition timing. The processing of these routines is executed for each combustion cycle in each cylinder.

  In the routine shown in FIG. 3, the ECU 40 first determines whether or not the fuel cut is being performed based on whether or not a predetermined fuel cut execution condition is satisfied (step 100). As a result, when the fuel cut is in progress, the count value cyc of the number of combustion cycles in step 110 described later is reset to zero (step 102).

  On the other hand, when the fuel cut is not being performed, that is, when combustion is being performed, the ECU 40 uses the in-cylinder pressure sensor 30 to acquire actually measured data of in-cylinder pressure including data on the combustion period of the current combustion cycle. (Step 104). Next, the ECU 40 calculates the actual CA 50 using the method described above with reference to FIG. 2 (step 106).

Next, ECU 40 calculates the actual CA50 _M (step 108). Here, CA50 _M corresponds to the value of CA50 that would have been obtained if operated at the MBT ignition timing. The magnitude of the amount of deviation of the ignition timing with respect to the MBT ignition timing in the vicinity of the MBT ignition timing and the magnitude of the amount of deviation of the CA 50 accompanying this deviation of the ignition timing can be regarded as substantially equal. Therefore, CA50 _M can be expressed as a value obtained by subtracting the sum of retardation amounts ATQ, AKCS, and AMBT from CA50 as shown in the following equation (2).

The actual CA50 _M can be calculated by substituting the actual CA50 (calculated value by the processing of step 106) for the right side of the equation (2). When there is no request for retarding the ignition timing, the retard amounts ATQ and AKCS are zero. On the other hand, when there is a request for retarding the ignition timing, the value calculated by the processing in step 202, step 208, or 212 described later is used as the retard amount ATQ or AKCS that is substituted into equation (2). . According to the processing of step 108, when there is a request for retarding the ignition timing, the actual CA50 calculated when the ignition timing is retarded based on the retardation request (that is, the calculated value by the processing of step 106). Based on this, the actual CA50 _M is calculated.

Next, the ECU 40 determines whether or not the count value cyc of the number of combustion cycles has reached a predetermined value A (step 110). The actual CA50 _M used for calculation of the retard amount AMBT by the process of step 118 described later may be a value of a certain combustion cycle, but in the present embodiment, the actual CA50 of the past predetermined number of cycles (predetermined value A). actual CA50 _M AVE is used is an average value of _M. The process for smoothing the actual CA50 _M is not limited to the use of a simple average, and for example, a primary smoothing process may be used.

Number of combustion cycles of calculation of the actual CA50 _M in step 110 if it is determined not reached the predetermined value A, ECU 40 adds the count value cyc by 1 (step 112). On the other hand, when the determination in step 110 is satisfied, the ECU 40 calculates actual CA50 _M AVE (step 114).

Then, ECU 40 is the difference between the target CA50 _M and the actual CA50 _M AVE ΔCA50 _M (= target CA50 _M - real CA50 _M AVE) is calculated (step 116). The target CA50 _M is an adaptive value of CA50 obtained when ignition is performed at the MBT ignition timing under each engine operating condition (engine speed and engine load), and is stored in the ECU 40.

Next, the ECU 40 calculates the retardation amount AMBT (step 118). As described above, the magnitude of the amount of deviation of the ignition timing with respect to the MBT ignition timing in the vicinity of the MBT ignition timing and the magnitude of the amount of deviation of the CA50 accompanying this deviation of the ignition timing can be regarded as substantially equal. Therefore, the retardation amount AMBT is expressed as the following equation (3).

  Next, in the routine shown in FIG. 4, the ECU 40 determines whether or not the target torque is lower than the expected torque (step 200). Here, it is assumed that the target torque is a driver request torque as an example. The required torque can be calculated based on the accelerator opening. The expected torque (estimated value of the generated torque) can be calculated by using in-cylinder pressure data acquired by the in-cylinder pressure sensor 30, for example.

  If it is determined in step 200 that the target torque is lower than the expected torque, the ECU 40 calculates a retard amount ATQ corresponding to the target torque (step 202). On the other hand, if it is determined that the target torque is greater than or equal to the expected torque, the ECU 40 resets the retardation amount ATQ to zero (step 204).

  Following the processing of step 202 or 204, the ECU 40 determines whether or not knocking has occurred in the current combustion cycle (step 206). The presence or absence of knocking can be determined using the output value of the in-cylinder pressure sensor 30, for example. If it is determined in step 206 that knock has occurred, the ECU 40 updates the retardation amount AKCS so as to be a value obtained by adding a predetermined value B to the current retardation amount AKCS (step 208).

  On the other hand, when it is determined in step 206 that no knock has occurred in the current combustion cycle, the ECU 40 determines whether or not the knock-free period has continued for a predetermined time (step 210). As a result, when this determination is not satisfied, the retardation amount AKCS is not corrected. On the other hand, when this determination is established, the ECU 40 updates the retardation amount AKCS so as to be a value obtained by subtracting the predetermined value C from the current retardation amount AKCS (step 212). However, the retardation amount AKCS is not corrected to less than zero by the processing of this step 212.

  Next, the ECU 40 calculates a final target ignition timing (step 214). The target ignition timing is calculated as the sum of the base ignition timing ABSE and the retard amounts ATQ, AKCS, and AMBT. As the base ignition timing ABSE, a value calculated as a value corresponding to the engine rotation speed and the engine load is used. As the retard amount AMBT, the calculated value in step 118 is used. The retardation amounts ATQ and AKCS are set to values that reflect the results of the processing in steps 200 to 212 described above.

According to the routine processing shown in FIGS. 3 and 4 described above, feedback control is executed when there is no request for retarding the ignition timing (that is, when the ignition timing is controlled so as to approach the MBT ignition timing). In addition, the ignition timing feedback control can be performed even when there is a delay angle request. More specifically, when there is a retardation request, based on the actual CA50 calculated when the ignition timing is retarded, the actual CA50 _M that would have been obtained if operated at the MBT ignition timing. Is calculated. Further, as described above, the target CA50 _M is the CA50 obtained when ignition is performed at the MBT ignition timing, and the target CA50 _M itself does not change much even if the engine operating conditions change. According to this routine, the ignition timing is feedback-controlled so that the difference between the target CA50 _M and the actual CA50 _M becomes small, so that when the ignition timing is requested to be retarded, the ignition timing is excessively delayed. Ignition timing control can be performed while suppressing the angle.

  In the first embodiment described above, the “first calculation means” in the present invention is realized by the ECU 40 executing the process of step 106, and the ECU 40 executes the process of step 108. The “second calculating means” in the present invention is realized, and the ECU 40 calculates the target ignition timing in step 214 using the retardation amount AMBT calculated in step 118, and based on the calculated target ignition timing. By controlling the ignition timing, the “ignition timing control means” in the present invention is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS.

The ignition timing control in the second embodiment is the same as the ignition timing control in the first embodiment except that the correction coefficient K is used as follows when calculating the actual CA50 _M and the retard amount AMBT. Therefore, the ignition timing control of the present embodiment can be realized by executing the routine processes shown in FIGS. 3 and 4 while correcting the processes of steps 108 and 118 as described below.

  FIG. 5 is a diagram for explaining a correction coefficient K setting method. FIG. 5 shows the relationship between the ignition timing (actual value) and the correction coefficient K. The retard amount of the ignition timing with respect to the MBT ignition timing is also referred to as “ΔSA”. The correction coefficient K corresponds to a change amount of CA50 per 1 ° CA in ΔSA. The correction coefficient K is set so that the value at the time of the MBT ignition timing is 1, and increases as ΔSA increases.

In the present embodiment, in the process corresponding to step 108 of the routine shown in FIG. 3, the actual CA50 _M is calculated in consideration of the correction coefficient K according to the following equation (4). That is, in the equation (4), the correction coefficient K is multiplied by the sum (ATQ + AKCS + AMBT) of various correction amounts (retard amount) corresponding to the retard amount ΔSA of the ignition timing from the MBT ignition timing.

According to the above equation (4), the larger the retard amount ΔSA of the ignition timing with respect to the MBT ignition timing, the greater the actual CA50 _M calculated as a value obtained by correcting the actual CA50 to the advance side with a larger correction amount. . For example, when the MBT ignition timing is 10 ° CA (BTDC), when the ignition timing is retarded by 5 ° CA and ignition is performed at 5 ° CA (BTDC), the actual CA50 is 16 ° CA (ATDC). ). The retard amounts ATQ, AKCS and AMBT are zero, and the correction coefficient K at 5 ° CA (BTDC) is 1.3. In this case, the actual CA50 _M is 9.5 ° CA (ATDC) obtained by subtracting the product of 5 and 1.3 from 16 by the equation (4). On the other hand, the actual CA50 _M calculated when the correction coefficient K is not considered is 11 ° CA (ATDC).

The larger the retard amount ΔSA of the ignition timing with respect to the MBT ignition timing, the slower the combustion. For this reason, the larger the retardation amount ΔSA, the larger the change amount of CA50 per 1 ° CA in ΔSA. According to the setting of the correction coefficient K and the equation (4) shown in FIG. 5, the actual CA50 _M can be calculated more precisely in consideration of the sensitivity of the CA50 with respect to the retard of the ignition timing.

In the present embodiment, in the process corresponding to step 118 of the routine shown in FIG. 3, the retardation amount AMBT is calculated in consideration of the correction coefficient K according to the following equation (5). That is, the right side of equation (5) is a value obtained by dividing the right side of equation (3) by the correction coefficient K.

According to the above equation (5), the retard amount AMBT is corrected to be smaller by the correction coefficient K as the retard amount ΔSA of the ignition timing with respect to the MBT ignition timing is larger. For example, it is assumed that ΔCA50 _M is 1.5 ° CA and the correction coefficient K is 1.3. In this case, according to the equation (5), the retardation amount AMBT is calculated as about 1.15 ° CA by dividing 1.5 by 1.3. On the other hand, the retardation amount AMBT calculated when the correction coefficient K is not considered is 1.5 ° CA. According to the equation (5) using the setting of the correction coefficient K shown in FIG. 5, the retard amount AMBT can be calculated more precisely in consideration of the sensitivity of the CA 50 with respect to the retard of the ignition timing.

  FIG. 6 is a time chart for explaining the operation when the control according to the second embodiment of the present invention is executed. As an example, FIG. 6 shows an operation example when a request for increasing the engine torque is issued. . More specifically, FIG. 6B shows an operation example of the ignition timing control of the present embodiment, and FIG. 6A shows an ignition timing control D referred to for comparison with the main ignition timing control. An example of the operation is shown.

  First, the ignition timing control D shown in FIG. The ignition timing control D is feedback control of the ignition timing so that the actual CA50 approaches the target CA50 (that is, ΔCA50 approaches zero). In the ignition timing control D, it is assumed that the feedback control is continued while retarding the target CA50 to a value that is suitable in relation to the target torque even when there is a request for retarding the ignition timing.

  In the period before time t0 in FIG. 6A, the ignition timing is controlled so that the MBT ignition timing is obtained. Time point t0 is a time point when the accelerator pedal is depressed. As the accelerator opening increases, the target torque is increased. As a result, the engine load increases. Further, in this example, the operation region corresponding to the target torque after the change is an operation region that requires a retard of the ignition timing in order to suppress knocking. As a result, the base ignition timing ABSE is less than the MBT ignition timing. Have been delayed.

  Since the instantaneous value of the actual CA 50 varies as shown in FIG. 6A, the actual CA 50 after the smoothing process (for example, the primary smoothing process) is calculated in the ignition timing control D. The waveform of ΔCA50 shown in FIG. 6A is a waveform of ΔCA50 as a difference from the actual CA50 after the target CA50, and becomes transiently large immediately after the ignition timing is retarded. In the ignition timing control D, a value obtained by adding ΔCA50 to the base ignition timing ABSE is calculated as the final target ignition timing. Therefore, as shown in FIG. 6A, the target ignition timing is transiently increased immediately after the ignition timing is retarded due to the influence of the change in ΔCA50. As a result, during execution of the ignition timing control D, there is a possibility that the ignition timing is excessively retarded immediately after the ignition timing is retarded and misfire is likely to occur.

Next, the operation of the ignition timing control of this embodiment will be described. FIG. 6B shows the waveform of the retard amount ΔSA of the ignition timing from the MBT ignition timing. In the present embodiment, the actual CA 50 is corrected by the product of the retardation amount ΔSA (= ATQ + AKCS + AMBT) and the correction coefficient K according to the equation (4). Here, a value obtained by adding a negative sign to this product is referred to as “CA50 _M correction amount”. More specifically, (4) from the relation of equation, as the sum of CA50 _M correction amount (negative value) and the instantaneous value of the actual CA50, the instantaneous value of the actual CA50 _M is calculated. Further, in the present ignition timing control, smoothing processing (for example, primary smoothing processing) is performed on the instantaneous value of the actual CA50 _M , and as shown in FIG. _M is calculated.

By performing CA50 _M correction amount correction using the (contents described with reference to FIG. 5) with respect to the actual CA50, it receives a retard request of the ignition timing, that the actual CA50 _M is greatly retarded It is suppressed. Further, the target CA50 _M is the CA50 obtained when ignition is performed at the MBT ignition timing as described above. For this reason, as shown in FIG. 6 (B), even if the ignition timing retardation request at time t0 is received, both the actual CA50 _M and the target CA50 _M are suppressed from being greatly retarded. . As a result, as shown in FIG. 6B, a change in ΔCA50 _M , which is the difference between the target CA50 _M and the actual CA50 _M , is also suppressed. Therefore, the final retard angle of the target ignition timing calculated based on the base ignition timing ABSE and ΔCA50 _M is suppressed as shown in FIG. The operation example in the ignition timing control of the first embodiment described above is the same as the operation example shown in FIG. 6B except for the difference due to the calculation of the CA50 _M correction amount without using the correction coefficient K. It will be a thing.

  By the way, in Embodiment 1 and 2 mentioned above, CA50 was illustrated as "a combustion time index value" which shows a combustion time. However, the “combustion timing index value” in the present invention may be an index value representing the combustion timing, and may be, for example, the in-cylinder pressure maximum crank angle θPmax instead of the exemplified CA50, or other than the CA50. Any specific ratio combustion point CAα may be used.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 18 Air flow meter 24 Combustion chamber 26 Fuel injection valve 28 Spark plug 30 In-cylinder pressure sensor 40 Electronic control unit (ECU)
42 Crank angle sensor 44 Accelerator position sensor

Claims (1)

A control device for controlling an internal combustion engine comprising an ignition device for igniting an air-fuel mixture in a cylinder and an in-cylinder pressure sensor for detecting an in-cylinder pressure,
First calculation means for calculating an actual combustion timing index value that is an actual value of the combustion timing index value based on an output value of the in-cylinder pressure sensor;
Based on the calculated actual combustion timing index value, an actual MBT combustion timing index value, which is an actual value of the combustion timing index value that would have been obtained if operated at the MBT ignition timing, is calculated. Two calculating means;
The ignition timing is controlled so that the difference between the actual MBT combustion timing index value and the target MBT combustion timing index value, which is the target value of the combustion timing index value when ignition is performed at the MBT ignition timing, is reduced. Ignition timing control means;
A control device for an internal combustion engine, comprising:

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