JP4830986B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to a control apparatus suitable for use in an internal combustion engine that detects abnormal combustion such as knocking and performs control for suppressing abnormal combustion.

  Conventionally, for example, in Patent Document 1, a heat generation rate is calculated based on an output value of an in-cylinder pressure sensor, and knocking of a spark ignition internal combustion engine that determines whether knocking has occurred or not is determined according to a slope of the calculated heat generation rate. A control device is disclosed. Further, in this conventional control device, when it is determined that knocking has occurred, knocking suppression means such as ignition retard is executed.

Japanese Patent No. 2826591 JP 2005-030332 A JP 2002-332908 A JP 2001-055955 A JP 2000-170589 A

  By the way, deposits (combustion deposits) existing in the cylinder of the internal combustion engine can cause sudden abnormal combustion (such as knocking and surface ignition). In the conventional technique described above, it is determined whether or not the current state of the internal combustion engine is just before the occurrence of knocking based on the detection result of the in-cylinder pressure for one cycle of combustion. For this reason, depending on the deposit state in the cylinder, there may be a case where knocking cannot be suppressed because the correction amount of the knocking suppression means is insufficient. On the other hand, in consideration of the secular change of the internal combustion engine and the machine difference variation, there is a possibility that the output performance of the internal combustion engine is unnecessarily lowered by performing excessive correction for suppressing knocking.

  The present invention has been made to solve the above-described problems, and an internal combustion engine control device that can detect whether or not abnormal combustion has occurred in advance in consideration of deposit accumulation in a cylinder. The purpose is to provide.

The first invention comprises an in-cylinder pressure measuring means for measuring the in-cylinder pressure,
In-cylinder pressure estimating means for estimating the in-cylinder pressure during combustion based on the operating conditions of the internal combustion engine;
An unburned gas amount acquisition means for acquiring an estimated value of the unburned gas amount based on a difference between an actual measured value of the in-cylinder pressure and a predicted value of the in-cylinder pressure;
Abnormal combustion determination means for determining that abnormal combustion occurs when an integrated value of the estimated value of the amount of unburned gas reaches a predetermined determination value;
It is characterized by providing.

Further, the second invention is an air-fuel ratio measuring means for measuring the exhaust air-fuel ratio of the internal combustion engine,
Target air-fuel ratio acquisition means for acquiring a control target air-fuel ratio of the internal combustion engine;
Unburned fuel amount acquisition means for acquiring an estimated value of the unburned fuel amount based on a difference between the control target air-fuel ratio and an actual measurement value of the exhaust air-fuel ratio;
Operation parameter acquisition means for acquiring a parameter indicating an operation condition of the internal combustion engine;
Based on the estimated value of the unburned fuel amount and the parameter, an unburned gas amount acquisition means for acquiring an estimated value of the unburned gas amount;
Abnormal combustion determination means for determining that abnormal combustion occurs when an integrated value of the estimated value of the amount of unburned gas reaches a predetermined determination value;
It is characterized by providing.

According to a third aspect of the present invention, in the first or second aspect of the invention, when the integrated value of the unburned gas amount reaches the determination value, a correction for calculating a correction amount of the actuator for suppressing abnormal combustion. Further comprising an amount calculating means,
Even when the integrated value of the unburned gas amount does not reach the determination value, the correction amount calculating means determines that the degree of increase in the integrated value is higher than a predetermined reference. The correction amount of the actuator is calculated.

  According to a fourth aspect, in the third aspect, the correction amount calculating means increases the correction amount as the degree of increase in the integrated value increases.

  According to the first invention, the estimated value of the unburned gas amount is acquired based on the difference between the predicted value of the in-cylinder pressure and the actually measured value. The unburned gas amount is proportional to the in-cylinder deposit amount. For this reason, by comparing the accumulated value of the estimated value of the unburned gas amount with a predetermined judgment value, the presence or absence of sudden abnormal combustion can be confirmed in consideration of the deposit state in the cylinder. Can be detected.

  According to the second invention, the estimated value of the unburned gas amount is acquired based on the difference between the control target air-fuel ratio and the actual measured value of the exhaust air-fuel ratio. The unburned gas amount is proportional to the in-cylinder deposit amount. For this reason, by comparing the accumulated value of the estimated value of the unburned gas amount with a predetermined judgment value, the presence or absence of sudden abnormal combustion can be confirmed in consideration of the deposit state in the cylinder. Can be detected.

  According to the third aspect of the invention, the minimum necessary correction for suppressing abnormal combustion is executed according to the degree of increase in the integrated value of the unburned gas amount. That is, it is possible to calculate an appropriate correction amount for suppressing abnormal combustion in accordance with the degree of increase that is proportional to the deposit amount in the cylinder.

  According to the fourth aspect of the invention, it is possible to calculate an optimal correction amount for suppressing abnormal combustion according to the degree of increase.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10. The internal combustion engine 10 of the present embodiment is an internal combustion engine having a plurality of cylinders such as an in-line four-cylinder type. A piston 12 that reciprocates inside the cylinder of the internal combustion engine 10 is provided. Further, the internal combustion engine 10 includes a cylinder head 14. A combustion chamber 16 is formed between the piston 12 and the cylinder head 14. An intake passage 18 and an exhaust passage 20 communicate with the combustion chamber 16. An intake valve 22 and an exhaust valve 24 are disposed in the intake passage 18 and the exhaust passage 20, respectively.

  In the vicinity of the inlet of the intake passage 18, an air flow meter 26 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 18 is provided. A throttle valve 28 is provided downstream of the air flow meter 26. The throttle valve 28 is an electronically controlled throttle valve that can control the throttle opening TA independently of the accelerator opening.

  A spark plug 30 is attached to the cylinder head 14 so as to protrude into the combustion chamber 16 from the top of the combustion chamber 16. The cylinder head 14 is provided with a combustion injection valve 32 that injects fuel into the cylinder. Further, the cylinder head 14 incorporates an in-cylinder pressure sensor 34 for detecting the in-cylinder pressure P. More specifically, it is assumed that the in-cylinder pressure sensor 34 is arranged in each cylinder and can acquire the in-cylinder pressure P for each cylinder.

  Further, the internal combustion engine 10 includes a crank angle sensor 36 for detecting the engine speed NE in the vicinity of the crankshaft. Further, an A / F sensor 38 for detecting the exhaust air-fuel ratio at that position is disposed in the exhaust passage 20. More specifically, according to such an A / F sensor 38, the sensor output is acquired according to the timing at which the exhaust gas discharged from the combustion chamber 16 of each cylinder reaches the A / F sensor 38. By doing so, the exhaust air-fuel ratio information of each cylinder can be acquired for each cylinder.

  The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 40. In addition to the various sensors described above, the ECU 40 is connected to an accelerator opening sensor 42 for detecting the accelerator opening, and the ECU 40 is connected to the various actuators described above. The ECU 40 can control the operating state of the internal combustion engine 10 based on the sensor outputs.

  FIG. 2 is a diagram for explaining the outline of the abnormal combustion detection method in the first embodiment of the present invention. FIG. 2 shows the waveform of the in-cylinder pressure P in the compression stroke and the expansion stroke in relation to the crank angle. More specifically, a waveform represented by a solid line in FIG. 2 indicates a predicted value of the in-cylinder pressure (combustion pressure) P when the combustion of the internal combustion engine 10 is normally performed. On the other hand, the waveform represented by the broken line in FIG. 2 indicates the waveform of the in-cylinder pressure P during actual combustion measured by the in-cylinder pressure sensor 34.

  As in the case shown in FIG. 2, when the measured value is lower than the predicted value of the in-cylinder pressure P, it can be determined that the fuel supplied into the combustion chamber 16 is not sufficiently burned. . If the combustion is not performed sufficiently, the amount of unburned gas will increase. More specifically, the amount of unburned gas is proportional to the difference between the predicted value of the in-cylinder pressure P and the measured value thereof, and increases as the difference increases.

Further, as the amount of unburned gas increases, the amount of deposit deposited in the cylinder also increases. The existence of such a deposit amount can cause sudden abnormal combustion (knocking, surface ignition, etc.). Therefore, in the present embodiment, the combustion pressure waveform measured by the in-cylinder pressure sensor 34 and the combustion pressure waveform of the in-cylinder pressure P predicted from the operating conditions of the internal combustion engine 10 (engine speed NE, load, etc.) Compare. Then, when the predicted value is lower than the actual measurement value, it is determined that the supplied fuel has not sufficiently burned, and the estimated value Gas _unig of the unburned gas amount is calculated from the difference between the predicted value and the actual measurement value. did.

In addition, in this embodiment, the estimated value Gas _unig of the unburned gas amount for each combustion cycle is integrated for each cylinder of the internal combustion engine 10, and abnormal combustion occurs when the integrated value Σ (Gas _unig ) exceeds a predetermined value. Predicted the occurrence of

FIG. 3 is a flowchart of a main routine executed by the ECU 40 in the first embodiment in order to realize the above function. In the main routine shown in FIG. 3, first, the in-cylinder pressure P during combustion (see FIG. 2) is acquired by the in-cylinder pressure sensor 34 (step 100). Next, calculation of an estimated value Gas _unig of the unburned gas amount is executed (step 102). The estimated value Gas _unig is calculated by a subroutine shown in FIG. 4 executed in parallel with this routine.

In the subroutine shown in FIG. 4, first, a predicted value (see FIG. 2) of the in-cylinder pressure P at the time of normal combustion is calculated based on the operating condition (engine speed NE and load) of the internal combustion engine 10 (step 200). ). Next, an estimated value Gas _unig of the unburned gas amount is calculated based on the difference between the predicted value of the in-cylinder pressure P calculated in step 200 and the actually measured value of the in-cylinder pressure P acquired in step 100. (Step 202).

More specifically, the estimated value Gas _unig is a value obtained by multiplying the difference (predicted value−actually measured value) of the in-cylinder pressure P by a predetermined proportional coefficient K acquired according to the map shown in FIG. Calculated. As shown in FIG. 5, the proportional coefficient K is set so as to increase as the engine speed NE increases and as the load increases. According to such a map setting, it can be estimated that the amount of unburned gas increases under the operating condition where the intake air amount increases.

Next, in the main routine shown in FIG. 3, determination of the unburned gas integrated amount Σ (Gas _unig ) is executed (step 104). More specifically, in this step 104, the accumulated value Σ (Gas _unig ) of the estimated value Gas _unig of the unburned gas amount sequentially accumulated for each combustion cycle for each cylinder is _{equal to} or greater than a predetermined determination value Gas _preig . It is determined whether or not there is. The integrated value Σ (Gas _unig ) corresponds to a value obtained by multiplying the area of the broken line in FIG. 2 by the proportional coefficient K.

As a result, if it is determined that the integrated value Σ (Gas _unig ) ≧ determination value Gas _preig is satisfied, it is predicted that abnormal combustion will occur if it remains as it is (step 106). Next, a correction amount A is calculated for suppressing abnormal combustion such as ignition retard and fuel injection amount reduction (step 108).

According to the routine shown in FIGS. 3 and 4 described above, the estimated value Gas _unig of the unburned gas amount is calculated based on the difference between the predicted value (estimated value) of the in-cylinder pressure P and the actually measured value. . The estimated value Gas _unig of the unburned gas amount is proportional to the in-cylinder deposit amount. For this reason, the accumulated value Σ (Gas _unig ) of the estimated value Gas _unig of the unburned gas amount is compared with the predetermined determination value Gas _preig for each cylinder in consideration of the deposit state in the cylinder. Thus, it is possible to detect in advance whether or not sudden abnormal combustion has occurred.

Further, according to the method of the present embodiment described above, the occurrence of abnormal combustion is not predicted from the result of one combustion cycle, but Σ (Gas _unig) which is an integrated value of the result of such one combustion cycle. ) To determine the presence or absence of abnormal combustion. For this reason, it becomes possible to acquire the correction amount A for suppressing abnormal combustion as an appropriate value without excess or deficiency.

  In the first embodiment described above, the ECU 40 executes the process of step 100, so that the “in-cylinder pressure measuring means” in the first invention executes the process of step 200. The “in-cylinder pressure estimating means” in the first invention executes the process of step 202 (102), so that the “unburned gas amount acquiring means” in the first invention performs the processes of steps 104 and 106. By executing this, the “abnormal combustion determination means” in the first aspect of the invention is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 6 and FIG.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIGS. 6 and 7 described later instead of the routine shown in FIGS. 3 and 4 using the hardware configuration shown in FIG. It can be done.

In the first embodiment described above, the estimated value Gas _unig of the unburned gas amount is calculated based on the difference between the predicted value (estimated value) of the in-cylinder pressure P and the actually measured value. On the other hand, in this embodiment, the estimated value of the unburned fuel amount is calculated from the difference between the measured value of the exhaust air / fuel ratio by the A / F sensor 38 and the control target A / F. The estimated value of the unburned fuel amount is calculated as an estimated value Gas _unig of the unburned gas amount in consideration of the operating conditions (engine speed NE, load, etc.) of the internal combustion engine 10.

  FIG. 6 is a flowchart of a main routine executed by the ECU 40 in the second embodiment in order to detect sudden abnormal combustion of the internal combustion engine 10 in advance. In FIG. 6, the same steps as those shown in FIG. 3 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the routine shown in FIG. 6, first, an actual value of the exhaust air / fuel ratio is acquired using the A / F sensor 38 (step 300). Next, calculation of an estimated value Gas _unig of the unburned gas amount is executed (step 302). The calculation of the estimated value Gas _unig in the present embodiment is performed by the subroutine of FIG. 7 executed in parallel with the present routine.

  In the routine shown in FIG. 7, first, the current control target A / F of the internal combustion engine 10 is acquired (step 400). Next, an estimated value of the unburned fuel amount is calculated based on the difference between the control target A / F acquired in step 400 and the actual measured value of the exhaust air / fuel ratio acquired in step 300 (step 402). ).

Next, the estimated value of the unburned fuel amount calculated in step 402 is multiplied by a predetermined proportionality coefficient K ′ acquired according to a map (not shown) defined in the same relationship as the map shown in FIG. As an estimated value, an estimated value Gas _unig of the unburned gas amount is calculated (step 404). According to the process of this step, it can be estimated that the amount of unburned gas increases under the operating condition where the amount of intake air increases.

In the routine shown in FIG. 6, next, as in the routine shown in FIG. 3, determination of the unburned gas integrated amount Σ (Gas _unig ) (step 104), prediction of occurrence of abnormal combustion (step 106), and abnormal combustion A series of processing such as calculation of the correction amount A for suppression (step 108) is executed.

According to the routines shown in FIGS. 6 and 7 described above, an estimated value of the unburned fuel amount is calculated based on the difference between the control target A / F and the actual measured value of the exhaust air / fuel ratio, and then the internal combustion engine is calculated. An estimated value Gas _unig of the unburned gas amount that is proportional to the in-cylinder deposit amount is calculated in consideration of the ten operating conditions. For this reason, also by the method of the present embodiment, by _comparing the integrated value Σ (Gas _unig ) of such an estimated value Gas _unig of the unburned gas amount with the predetermined determination value Gas _preig for each cylinder, It is possible to detect in advance whether or not sudden abnormal combustion has occurred in consideration of deposit accumulation.

Further, as in the first embodiment, since the presence or absence of abnormal combustion is determined using ΣGas _unig , which is an integrated value of the result for one cycle of combustion, the correction amount A for suppressing abnormal combustion is excessively _exceeded. It can be acquired as an appropriate value without a shortage.

  In the second embodiment described above, the ECU 40 executes the process of step 300, so that the “air-fuel ratio measuring means” in the second invention executes the process of step 400. The “target air-fuel ratio acquisition means” in the second aspect of the invention executes the process of step 402, so that the “unburned fuel amount acquisition means” of the second aspect of the invention executes the process of step 404 (302). As a result, the “operating parameter acquisition means” and the “unburned gas amount acquisition means” in the second invention perform the processing of the above steps 104 and 106, thereby the “abnormal combustion determination means” in the second invention. , Each has been realized.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to FIG. 8 and FIG.
The system of the present embodiment can be realized by causing the ECU 40 to execute a routine shown in FIG. 8 described later instead of the routine shown in FIGS. 3 and 4 using the hardware configuration shown in FIG. is there.

In the above-described first embodiment, _when the integrated value Σ (Gas _unig ) of the estimated value Gas _unig of the unburned gas amount does not reach the predetermined determination value Gas _preig , nothing is done to suppress abnormal combustion. The control is not performed. On the other hand, in this embodiment, _{even if} the integrated value Σ (Gas _unig ) of the estimated value Gas _unig of the unburned gas amount does not reach the predetermined determination value Gas _preig , the slope (increase of the unburned gas integrated amount) _Degree ) Δ (Σ (Gas _unig )), that is, the difference Δ (Σ (Gas _unig )) between the current integrated value Σ (Gas _unig ) and the previous integrated value Σ (Gas _unig ) is a predetermined determination value. When it is equal to or greater than (predetermined reference) ΔGas _preig , control for suppressing abnormal combustion such as ignition retard is performed.

  FIG. 8 is a flowchart of a routine executed by the ECU 40 in the third embodiment in order to realize the above function. In FIG. 8, the same steps as those shown in FIG. 3 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the routine shown in FIG. 8, if it is determined in step 104 that the integrated value Σ (Gas _unig ) ≧ the determination value Gas _preig is not established, then the unburned gas integrated amount slope Δ (Σ (Gas _unig It is determined whether or not)) is _{equal to} or greater than a predetermined determination value ΔGas _preig (step 500).

As a result, the slope Δ (Σ (Gas _unig )) of the unburned gas integrated amount, that is, the difference Δ (Σ (Gas _unig ) between the current integrated value Σ (Gas _unig ) and the previous integrated value Σ (Gas _unig ). )) Is determined to be _{equal to} or greater than the determination value ΔGaspreig, a correction amount B for controlling suppression of abnormal combustion such as ignition retard is calculated (step 502). The correction amount B in this step 502 is basically a correction amount smaller than the correction amount A.

More specifically, the correction amount B in this step 502 is acquired according to the map relationship shown in FIG. FIG. 9 is a diagram showing the characteristics of a map that defines the relationship between the correction amount B for suppressing abnormal combustion and the slope Δ (Σ (Gas _unig )) of the unburned gas integrated amount. In the map shown in FIG. 9, the correction amount B is set to increase as the slope Δ (Σ (Gas _unig )) of the unburned gas integrated amount increases. According to such a map setting, the correction amount B for preventing abnormal combustion can be appropriately set according to the magnitude of the slope Δ (Σ (Gas _unig )) of the unburned gas integrated amount. .

According to the routine shown in FIG. 8 described above, even if the integrated value Σ (Gas _unig ) of the estimated value Gas _unig of the unburned gas amount does not reach the predetermined judgment value Gas _preig , When the slope Δ (Σ (Gas _unig )) is _greater than or equal to a predetermined determination value ΔGas _preig , the minimum necessary for suppressing abnormal combustion according to the magnitude of the slope Δ (Σ (Gas _unig )) Correction is executed. That is, the optimum correction amount B for suppressing abnormal combustion can be calculated according to the magnitude of the slope Δ (Σ (Gas _unig )) that is proportional to the deposit amount in the cylinder. Thus, according to the processing of the present embodiment, the influence of the secular change of the internal combustion engine 10 can be learned well.

By the way, in Embodiment 3 mentioned above, although the method of calculating the estimated value Gas _unig of unburned gas quantity based on the difference of the predicted value of the cylinder pressure P and its measured value is used, the said estimated value _As a method for calculating Gas _unig, the method using the air-fuel ratio difference in the second embodiment described above may be combined.

  In the third embodiment described above, the “correction amount calculating means” in the third aspect of the present invention is implemented by the ECU 40 executing the processing of steps 108, 500, and 502 described above.

It is a figure for demonstrating the structure of Embodiment 1 of this invention. It is a figure for demonstrating the outline | summary of the detection method of the abnormal combustion in Embodiment 1 of this invention. It is a flowchart of the main routine performed in Embodiment 1 of the present invention. It is a flowchart of the subroutine performed in Embodiment 1 of this invention. It is a figure which shows an example of the map of the proportionality coefficient K referred in the subroutine shown in FIG. It is a flowchart of the main routine performed in Embodiment 2 of the present invention. It is a flowchart of the subroutine performed in Embodiment 2 of this invention. It is a flowchart of the main routine performed in Embodiment 3 of the present invention. It is a figure showing the characteristic of the map which defined the relationship between the corrected amount B for suppression of abnormal combustion, and inclination ( _delta ) (Σ (Gas _unig )) of unburned gas integrated amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 16 Combustion chamber 26 Air flow meter 28 Throttle valve 30 Spark plug 32 Combustion injection valve 34 In-cylinder pressure sensor 36 Crank angle sensor 38 A / F sensor 40 ECU (Electronic Control Unit)
42 Accelerator position sensor

Claims (4)

In-cylinder pressure measuring means for measuring the in-cylinder pressure;
In-cylinder pressure estimating means for estimating the in-cylinder pressure during combustion based on the operating conditions of the internal combustion engine;
An unburned gas amount acquisition means for acquiring an estimated value of the unburned gas amount based on a difference between an actual measured value of the in-cylinder pressure and a predicted value of the in-cylinder pressure;
Abnormal combustion determination means for determining that abnormal combustion occurs when an integrated value of the estimated value of the amount of unburned gas reaches a predetermined determination value;
A control device for an internal combustion engine, comprising: Air-fuel ratio measuring means for measuring the exhaust air-fuel ratio of the internal combustion engine;
Target air-fuel ratio acquisition means for acquiring a control target air-fuel ratio of the internal combustion engine;
Unburned fuel amount acquisition means for acquiring an estimated value of the unburned fuel amount based on a difference between the control target air-fuel ratio and an actual measurement value of the exhaust air-fuel ratio;
Operation parameter acquisition means for acquiring a parameter indicating an operation condition of the internal combustion engine;
Based on the estimated value of the unburned fuel amount and the parameter, an unburned gas amount acquisition means for acquiring an estimated value of the unburned gas amount;
Abnormal combustion determination means for determining that abnormal combustion occurs when an integrated value of the estimated value of the amount of unburned gas reaches a predetermined determination value;
A control device for an internal combustion engine, comprising: A correction amount calculating means for calculating a correction amount of an actuator for suppressing abnormal combustion when the integrated value of the unburned gas amount reaches the determination value;
Even when the integrated value of the unburned gas amount does not reach the determination value, the correction amount calculating means determines that the degree of increase in the integrated value is higher than a predetermined reference. 3. The control apparatus for an internal combustion engine according to claim 1, wherein the correction amount of the actuator is calculated.   4. The control apparatus for an internal combustion engine according to claim 3, wherein the correction amount calculation means increases the correction amount as the degree of increase in the integrated value increases.

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