JP2011208540A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine inhibiting inflow of unburnt gas into an exhaust system even when failure in flame propagation occurs due to abnormal combustion.SOLUTION: The control device of the internal combustion engine calculates an actual heat release amount in a cylinder based on an actual measurement of a cylinder pressure sensor at a predetermined crank angle in a combustion stroke, and acquires an ideal heat release amount in the cylinder based on a fuel injection amount. The control device determines whether or not the actual heat release amount is smaller than a predetermined percentage of the ideal heat release amount, and when the actual heat release amount is smaller than the predetermined percentage of the ideal heat release amount, causes an ignition plug to ignite near the bottom dead center before an exhaust stroke.

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable for executing control of an internal combustion engine mounted on a vehicle.

  Conventionally, as disclosed in, for example, Patent Literature 1, an internal combustion engine including an in-cylinder pressure sensor is known. This publication also compares the measured value of the in-cylinder pressure measured by the in-cylinder pressure sensor with the estimated value of the in-cylinder pressure calculated based on the engine speed and load, and based on this comparison value, abnormal combustion is performed. Is determined to occur.

JP 2009-002241 A JP 2007-170345 A

  By the way, flame propagation failure may occur due to abnormal combustion. In the conventional internal combustion engine, if flame propagation failure occurs, unburned gas flows into the exhaust system. If unburned gas flows into the exhaust system, the catalyst may be overheated and exhaust emission may be deteriorated.

  The present invention has been made to solve the above-described problems, and is an internal combustion engine capable of suppressing the inflow of unburned gas into the exhaust system even when flame propagation failure occurs due to abnormal combustion. An object of the present invention is to provide an engine control device.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An in-cylinder pressure sensor for measuring the in-cylinder pressure;
An actual heat generation amount calculating means for calculating an actual heat generation amount in the cylinder based on an actual measurement value of the in-cylinder pressure sensor at a predetermined crank angle during a combustion stroke;
An ideal heat generation amount acquisition means for acquiring an ideal heat generation amount in the cylinder based on the fuel injection amount;
Heat generation amount determination means for determining whether the actual heat generation amount is lower than a predetermined ratio of the ideal heat generation amount;
And a retard ignition means for igniting a spark plug in the vicinity of bottom dead center before the exhaust stroke when the actual heat generation amount is lower than a predetermined ratio of the ideal heat generation amount.

The second invention is the first invention, wherein
An estimated in-cylinder pressure calculating means for calculating an estimated value of the in-cylinder pressure that changes until the ignition timing by the spark plug (hereinafter referred to as a reference ignition timing) based on the intake pipe pressure;
Abnormal combustion determination that determines that abnormal combustion occurs when the measured value of the in-cylinder pressure sensor at a predetermined crank angle up to the reference ignition timing is higher than the estimated value calculated by the estimated in-cylinder pressure calculating means by a predetermined value or more. Means further comprising:
The retard ignition means is in the vicinity of the bottom dead center before the exhaust stroke when it is determined that the abnormal combustion occurs and the actual heat generation amount is lower than a predetermined ratio of the ideal heat generation amount. The spark plug is ignited.

The third invention is the second invention, wherein
When it is determined that the abnormal combustion occurs, it further includes ignition cut means for cutting ignition by the spark plug at the reference ignition timing.

Moreover, 4th invention is 2nd or 3rd invention,
Operation region determination means for determining whether or not the operation region is an abnormal combustion occurrence region;
In the abnormal combustion occurrence region, it further comprises a reference ignition timing retarding means for retarding the reference ignition timing.

The fifth invention is the third or fourth invention, wherein
Maximum in-cylinder pressure estimating means for estimating the maximum value of in-cylinder pressure based on the crank angle and the compression end temperature determined to cause the abnormal combustion;
Durability determination means for determining whether the maximum value of the in-cylinder pressure is larger than a set value related to the durability of the internal combustion engine;
The ignition cut means cuts the ignition by the spark plug at the reference ignition timing when it is determined that the abnormal combustion occurs when the maximum value of the in-cylinder pressure is larger than the set value; It is characterized by.

  According to the first invention, when the actual heat generation amount is lower than a predetermined ratio of the ideal heat generation amount, the spark plug can be ignited near the bottom dead center before the exhaust stroke. Therefore, the unburned gas remaining in the cylinder due to flame propagation failure can be burned. As a result, unburned gas can be prevented from flowing into the exhaust system, and the catalyst can be prevented from overheating. For this reason, according to the present invention, even when flame propagation failure occurs due to abnormal combustion, exhaust emission can be suitably maintained.

  According to the second aspect of the present invention, it is possible to determine that abnormal combustion occurs when the measured value of the in-cylinder pressure sensor at the predetermined crank angle up to the reference ignition timing is higher than the estimated value by a predetermined value or more. Therefore, it can be determined in advance that abnormal combustion occurs, and control for abnormal combustion can be performed in the cylinder in the current cycle.

  According to the third invention, when it is determined that abnormal combustion occurs, ignition by the spark plug at the reference ignition timing can be cut. By using the ignition energy due to abnormal combustion as the energy for flame formation, it is possible to suppress an excessive increase in the in-cylinder pressure. Therefore, the durability of the engine can be maintained.

  According to the fourth aspect of the invention, the reference ignition timing is retarded in the abnormal combustion occurrence region. Therefore, it is possible to delay the final period at which abnormal combustion can be determined. As a result, the range in which abnormal combustion can be determined before the reference ignition timing is widened, and abnormal combustion occurring near the compression top dead center can also be determined with high accuracy.

  According to the fifth aspect, even when it is determined that abnormal combustion occurs, if the estimated maximum value of the in-cylinder pressure is equal to or less than the set value, the ignition cut is not performed. Therefore, in a situation where the durability of the engine is ensured, it is possible to suppress overheating of the catalyst due to unburned gas and deterioration of drivability. On the other hand, when the maximum value of the in-cylinder pressure is larger than the set value, ignition cut is performed. Therefore, damage to the engine can be prevented. Therefore, according to the present invention, it is possible to minimize catalyst overheating and drivability deterioration due to unburned gas while preventing engine damage.

It is a figure for demonstrating the system configuration | structure which concerns on Embodiment 1 of this invention. It is a figure for demonstrating the relationship between the estimated value of the in-cylinder pressure calculated based on (1) Formula in the normal combustion cycle, and the actual value measured by the in-cylinder pressure sensor 13. It is a figure for demonstrating the deviation rate of the actual value measured by the in-cylinder pressure sensor 13 with respect to the estimated value of the in-cylinder pressure calculated based on (1) Formula in a normal combustion cycle. It is a figure for demonstrating the pressure deviation amount of the measured value with respect to the estimated value of the in-cylinder pressure at the time of normal combustion and the time of abnormal combustion. It is a conceptual diagram showing the situation where pre-ignition occurs at the outer edge of the piston crown surface and then spark ignition is performed by the spark plug 14. It is a figure which shows the change of the cylinder pressure at the time of ignition cut. It is a figure for demonstrating the change of the combustion ratio in a normal combustion cycle. In Embodiment 1 of this invention, it is a flowchart of the control routine which ECU50 performs. In Embodiment 2 of this invention, it is a flowchart of the control routine which ECU50 performs. It is a relationship map which showed the relationship between the torque used by control in Embodiment 2 of this invention, and ignition timing. It is a figure which shows the relationship between a heat generation position and the maximum value of in-cylinder pressure. In Embodiment 3 of this invention, it is a flowchart of the control routine which ECU50 performs. It is a figure for demonstrating the change of the in-cylinder pressure by preignition.

  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 according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an internal combustion engine (hereinafter simply referred to as an engine) 10. The internal combustion engine 10 is mounted on a vehicle or the like and used as a power source. Although the internal combustion engine 10 shown in FIG. 1 is an in-line four-cylinder type, in the present invention, the number of cylinders and the cylinder arrangement are not limited thereto.

  The internal combustion engine 10 is a spark ignition type internal combustion engine. Each cylinder of the internal combustion engine 10 is provided with an injector 12 that directly injects fuel into the cylinder, an in-cylinder pressure sensor 13 for detecting the in-cylinder pressure (combustion pressure), and a spark plug 14. The present invention is not limited to such a cylinder injection type internal combustion engine, but is a port injection type internal combustion engine that injects fuel into an intake port, or an internal combustion engine that uses both a cylinder injection type and a port injection type. The same applies to the above.

  The exhaust gas discharged from each cylinder of the internal combustion engine 10 is collected by the exhaust manifold 16 and flows into the exhaust passage 18. The internal combustion engine 10 includes a turbocharger 20 that performs supercharging with the energy of exhaust gas. The turbocharger 20 includes a turbine 20a that is rotated by the energy of exhaust gas, and a compressor 20b that is integrally connected to the turbine 20a and rotates. The turbine 20 a is arranged in the middle of the exhaust passage 18, and the compressor 20 b is arranged in the middle of the intake passage 22.

  A start catalyst (S / C) 24 for purifying harmful components in the exhaust gas is installed in the exhaust passage 18 on the downstream side of the turbine 20a. Since the start catalyst 24 is disposed at a position close to the exhaust port, the start catalyst 24 is warmed up in a short time from the start and can exhibit good exhaust purification performance. As the start catalyst 24, for example, a three-way catalyst is used.

  An air cleaner is provided near the inlet of the intake passage 22 of the internal combustion engine 10. An air flow meter 26 for detecting the intake air amount is attached in the vicinity of the downstream side of the air cleaner.

  An intercooler 28 for cooling the air compressed by the compressor 20b is installed in the intake passage 22 on the downstream side of the compressor 20b. A throttle valve 30 for adjusting the amount of air flowing through the intake passage 22 is disposed downstream of the intercooler 28. The throttle valve 30 is an electronically controlled valve that is driven by a throttle motor (not shown). A surge tank 32 is disposed downstream of the throttle valve 30. An intake pressure sensor 34 for detecting intake pressure (supercharging pressure) is attached to the surge tank.

  The internal combustion engine 10 includes an EGR passage 36 capable of performing EGR (Exhaust Gas Recirculation) for returning a part of the exhaust gas to the intake passage 22. The EGR passage 36 is configured to communicate the exhaust passage 18 upstream from the turbine 20a and the intake passage 22 downstream from the compressor 20b. In the middle of the EGR passage 36, an EGR cooler 38 for cooling the EGR gas and an EGR valve 40 for adjusting the flow rate of the external EGR gas are provided in this order from the exhaust passage 18 side.

  The system of this embodiment further includes an ECU (Electronic Control Unit) 50. In addition to the in-cylinder pressure sensor 13, the air flow meter 26, and the intake pressure sensor 34 described above, a crank angle sensor 42 for detecting the engine speed, and an air-fuel ratio for detecting the air-fuel ratio of the exhaust gas are input to the input portion of the ECU 50. Various sensors for detecting the operating state of the internal combustion engine 10 such as a sensor 44 and an intake air temperature sensor 46 for detecting the temperature of the intake air are connected. Also, various actuators for controlling the operating state of the internal combustion engine 10 such as the injector 12, the spark plug 14, the throttle valve 30, the EGR valve 40, etc., are connected to the output portion of the ECU 50. The ECU 50 controls the operating state of the internal combustion engine 10 by operating various actuators according to a predetermined program based on the outputs of the various sensors.

[Characteristic Control in Embodiment 1]
By the way, in the system provided with the turbocharger 20 described above, there is a possibility that sudden abnormal combustion, specifically, pre-ignition may occur in a low rotation and high load region. FIG. 13 is a diagram for explaining a change in in-cylinder pressure due to pre-ignition. As shown in the experimental results of FIG. 13, in the normal combustion cycle, the maximum value of the in-cylinder pressure is about 7 MPa, whereas in the abnormal combustion cycle in which pre-ignition occurs (hereinafter referred to as pre-ignition generation cycle), the in-cylinder pressure. May reach a maximum of 20 MPa. Further, the in-cylinder pressure change in the pre-ignition generation cycle has a large variation compared to the normal combustion cycle.

  As factors of pre-ignition, various factors such as oil, deposit / particulate of combustion chamber, hot spot, heterogeneity of air-fuel mixture, increase in residual gas, A / F lean, etc. can be considered. However, since these affect unavoidable factors such as deposits on the EGR passage 36 and the EGR valve 40 due to aging and wear of the piston ring, it is extremely difficult to design the occurrence of abnormal combustion to be zero. On the other hand, even when abnormal combustion occurs, in order to maintain the durability of the engine, it is necessary to perform control for preventing the engine from being damaged. In particular, in the supercharged engine like this embodiment, the necessity is high.

  Therefore, in the system of the present embodiment, the occurrence of abnormal combustion is determined before the ignition timing by the ignition plug 14, and when it is determined that abnormal combustion occurs, the ignition by the ignition plug 14 is controlled. . An outline of more specific control will be described with reference to FIGS. In this specification, the control of the system of this embodiment will be described by dividing it into first to third processes.

(First process)
First, the 1st process in the system of this embodiment is demonstrated using FIGS. The first process is an abnormal combustion determination process for determining whether or not abnormal combustion occurs in the cylinder in the current cycle before the ignition timing by the spark plug 14.

  Equation (1) is established as a state equation during adiabatic compression. In the equation (1), P is the in-cylinder pressure, V is the combustion chamber volume, and κ is the polytropic index (for example, κ = 1.32).

PV ^κ = const (1)

  FIG. 2 is a diagram for explaining the relationship between the estimated value of the in-cylinder pressure calculated based on the equation (1) in the normal combustion cycle and the actually measured value measured by the in-cylinder pressure sensor 13. Here, the normal combustion cycle refers to a cycle in which the air-fuel mixture in the cylinder is spark-ignited by the spark plug 14 and sequentially propagates in the flame from the vicinity of the spark plug and is suitably burned. FIG. 3 is a diagram for explaining the deviation rate of the actually measured value measured by the in-cylinder pressure sensor 13 with respect to the estimated value of the in-cylinder pressure calculated based on the equation (1) in the normal combustion cycle. In the present embodiment, the reference ignition timing by the ignition plug 14 is assumed to be the top dead center (TDC) of the compression stroke. The setting of the reference ignition timing is for ease of explanation and is not limited to this.

Estimate of the in-cylinder pressure in FIG. 2, the bottom dead center of the intake stroke: cylinder pressure P ₀ in (BDC Bottom Dead Center) assuming the intake pipe pressure, the cylinder pressure P _0, the combustion chamber volume at bottom dead center V It is calculated for each crank angle based on the equations ₀ and (1). As shown in FIG. 2, in the normal combustion cycle, the measured value of the in-cylinder pressure from the bottom dead center of the intake stroke to the reference ignition timing is substantially equal to the estimated value. Specifically, as shown in FIG. 3, in the normal combustion cycle, the deviation rate of the actually measured value from the estimated value of the in-cylinder pressure is as high as within 3%.

  On the other hand, in the pre-ignition generation cycle which is an abnormal combustion cycle, the actual measurement value with respect to the estimated value of the in-cylinder pressure largely deviates as shown in FIG. FIG. 4 is a diagram for explaining the pressure divergence amount of the actually measured value with respect to the estimated value of the in-cylinder pressure during normal combustion and abnormal combustion. As shown in FIG. 4, at the time of abnormal combustion, the measured value greatly increases and deviates from the estimated value before the reference ignition timing. Here, a section in which abnormal combustion occurs (hereinafter referred to as abnormal combustion determination section) is a section immediately before the reference ignition timing, and is, for example, within 20 degrees before compression top dead center (BTDC). In the abnormal combustion determination section, the pressure divergence rate between the estimated value of the in-cylinder pressure and the actually measured value is as high as 3% or less as shown in FIG. 3, so the actually measured value is higher than the estimated value, and the divergence rate is When it is larger than the predetermined threshold, it is determined that abnormal combustion due to pre-ignition has occurred. In the present embodiment, the abnormal combustion determination period is from 20 deg before compression top dead center to the reference ignition timing.

  Therefore, in the first process of the present embodiment, the estimated value of the in-cylinder pressure calculated based on the equation (1) is compared with the actually measured value measured by the in-cylinder pressure sensor 13 and estimated before the reference ignition timing. When the measured value is higher than the measured value and the deviation rate of the measured value from the estimated value is larger than a predetermined threshold, it is determined that abnormal combustion due to pre-ignition occurs in the cylinder in the current cycle. .

  According to the first process, it is possible to predict that abnormal combustion will occur before ignition by the spark plug, using simple in-cylinder pressure estimation. Therefore, the second to third processes described later can be suitably performed in the cylinder in the current cycle. Further, by setting the abnormal combustion determination section from 20 deg before compression top dead center to the reference ignition timing, the processing amount of the ECU 50 can be reduced.

(Second process)
Next, the second process in the system according to the present embodiment will be described with reference to FIGS. The second process is a process after the occurrence of abnormal combustion that is performed in order to prevent the engine from being damaged when an abnormal combustion that ignites other than the ignition type of the spark plug 14 occurs.

  FIG. 5 is a conceptual diagram showing a situation in which pre-ignition occurs at the outer edge portion of the piston crown surface and then spark ignition is performed by the spark plug 14. If ignition by spark ignition is further performed at the reference ignition timing after ignition by pre-ignition, extra spark ignition energy is given even though ignition has already been performed. Given excessive ignition energy, rapid flame propagation occurs at multiple locations. As a result, the in-cylinder pressure greatly increases, which causes the durability of the engine to deteriorate.

  Therefore, in the second process of the present embodiment, when it is determined by the first process described above that abnormal combustion occurs before the reference ignition timing, spark ignition by the spark plug 14 is performed in the cylinder in the current cycle. It was decided to cut.

  According to the second process, when pre-ignition occurs, the spark ignition by the spark plug is cut, so that ignition by pre-ignition can be used as energy for forming a flame without adding extra energy. FIG. 6 is a diagram showing a change in the in-cylinder pressure at the time of ignition cut. As shown in FIG. 6, by performing the ignition cut, it is possible to suppress an excessive increase in the in-cylinder pressure while avoiding rapid combustion at a plurality of locations. Therefore, damage to the engine can be prevented.

(Third process)
Subsequently, a third process in the system of the present embodiment will be described with reference to FIG. The third process is the occurrence of abnormal combustion that is performed in order to suppress overheating (OT) of the start catalyst 24 while preventing engine breakage when abnormal combustion that occurs other than the ignition type of the spark plug 14 occurs. It is a later process.

  FIG. 7 is a diagram for explaining the change in the combustion ratio in the normal combustion cycle. A solid line 60 is a line representing a change in in-cylinder pressure. A solid line 62 is a line representing a change in the combustion rate when the air-fuel mixture is normally combusted. As shown by the solid line 62, the air-fuel mixture is burned almost completely after ignition at the reference ignition timing and after 90 deg after the top dead center (ATDC) of the compression stroke. On the other hand, when flame propagation failure occurs, unburned gas remains in the cylinder. If this unburned gas flows into the exhaust passage 18, it will cause the start catalyst 24 to overheat. In particular, when the ignition cut is performed using the second process, an increase in the in-cylinder pressure can be suppressed, but a flame propagation defect is likely to occur due to a shortage of ignition energy, and there is a high possibility that unburned gas remains. Therefore, when the second treatment is used, there is a concern about overheating of the start catalyst 24 in particular.

  Therefore, in the third process of the present embodiment, when it is determined by the first process described above that abnormal combustion occurs before the reference ignition timing, the in-cylinder pressure sensor 13 at a predetermined crank angle during the combustion stroke is used. When the actual heat generation amount in the cylinder based on the actually measured value is lower than a predetermined ratio of the ideal heat generation amount in the cylinder based on the fuel injection amount, spark ignition by the spark plug 14 is performed near the bottom dead center of the combustion stroke. We decided to carry out.

  According to the third process, it is possible to detect a decrease in the combustion ratio due to defective flame propagation that occurs when abnormal combustion occurs, and to reignite the unburned gas. Therefore, it is possible to prevent the unburned gas from flowing into the exhaust passage 18 and overheating the bed temperature of the start catalyst 24. In particular, by using together with the second treatment, it is possible to prevent the start catalyst from being overheated while suppressing an increase in the in-cylinder pressure, thereby effectively preventing engine damage.

(Control routine)
FIG. 8 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described operation. This routine is executed for each cycle and each cylinder. In the routine shown in FIG. 8, first, in step 100, it is determined whether or not abnormal combustion due to pre-ignition occurs.

As the abnormal combustion determination process, the first process described above is used. Specifically, first, the in-cylinder pressure P ₀ at the intake stroke bottom dead center is acquired by the in-cylinder pressure sensor 13 as the intake pipe pressure. In the ECU 50, a relationship map between the crank angle and the combustion chamber volume V is stored in advance. Then, the estimated in-cylinder pressure Pe at the current crank angle is sequentially calculated based on the combustion chamber volume V _{0 at} the bottom dead center, the above-described in-cylinder pressure P _0, and the equation (1). Further, the actual in-cylinder pressure Pr is sequentially detected by the in-cylinder pressure sensor 13. If the actual in-cylinder pressure Pr becomes higher than the estimated in-cylinder pressure Pe before the reference ignition timing and the deviation rate of the actual in-cylinder pressure Pr from the estimated in-cylinder pressure Pe becomes larger than a predetermined threshold value α, It is determined that preignition occurs in the cylinder. For example, 3σ is used as the threshold value α. σ is a conforming value related to pressure variation determined for each load. Note that the section in which the abnormal combustion determination process is performed is from 20 deg before compression top dead center to the reference ignition timing.

  If it is determined in step 100 that pre-ignition will occur, then, in step 110, the second process described above is performed. Specifically, the ECU 50 cuts off spark ignition by the spark plug 14 in the cylinder in the current cycle.

  Thereafter, in step 120 to step 150, the third process described above is performed. First, in step 120, the ideal heat generation amount in the cylinder corresponding to the fuel injection amount is calculated. Specifically, the ECU 50 stores a relationship map in which the relationship between the fuel injection amount and the ideal heat generation amount when the fuel injection amount is completely burned is determined by experiment or the like for each operating condition. An ideal heat generation amount corresponding to the fuel injection amount is calculated from this relationship map. The fuel injection amount is calculated from the control value to the injector 12.

  In step 130, the actual amount of heat generated in the cylinder corresponding to the actual cylinder pressure Pr at a predetermined crank angle during the combustion stroke is calculated. Specifically, the ECU 50 stores a relationship map in which the relationship between the in-cylinder pressure and the actual heat generation amount is determined by experiment or the like for each operating condition. From this relationship map, the actual heat generation amount corresponding to the actual in-cylinder pressure Pr at a predetermined crank angle during the combustion stroke measured by the in-cylinder pressure sensor 13 is calculated. As the predetermined crank angle during the combustion stroke, for example, 60 deg before bottom dead center is used. According to the inventor's knowledge, 60 deg before the bottom dead center is an intersection where the slope of the heat generation amount changes and is appropriate as a value.

  In step 140, it is determined whether or not the actual heat generation amount / ideal heat generation amount × 100 is lower than the threshold value β (%). The threshold value β is a determination value for determining a flame propagation failure. As the threshold value β, as shown by the solid line 60 in FIG. 7, the threshold value β is approximately the combustion ratio at the maximum in-cylinder pressure, so 60 to 70% is appropriate as the value.

  If the determination condition in step 140 is satisfied, it can be determined that a flame propagation failure has occurred due to a lack of ignition energy and combustion has deteriorated. Therefore, in step 150, the ECU 50 performs spark ignition by the spark plug 14 near the bottom dead center before the exhaust stroke. Thereafter, the processing of this routine is terminated. If the determination condition in step 100 or 140 is not satisfied, the process of this routine is terminated.

  As described above, according to the routine shown in FIG. 8, it is possible to predict the occurrence of pre-ignition and perform the ignition cut. Therefore, even if abnormal combustion occurs, ignition energy can be suppressed and engine damage can be prevented. Furthermore, according to this routine, even if flame propagation failure occurs due to ignition cut and unburned gas remains, reignition can be performed before the exhaust stroke. Therefore, overheating of the start catalyst 24 due to inflow of unburned gas into the exhaust passage 18 can be prevented. For this reason, according to the system of this embodiment, engine durability and emission can be improved.

  By the way, in the system of the first embodiment described above, the third process is used in combination with the first process and the second process, but the present invention is not limited to this. For example, the third process alone or the first process and the second process may be used in combination. This point is the same in the following embodiments.

  In the system of the first embodiment described above, the abnormal combustion determination section in the first process is set from 20 deg before compression top dead center to the reference ignition timing, but is not limited to this. For example, the abnormal combustion determination section may be from the bottom dead center of the intake stroke to the reference ignition timing.

  In the first embodiment described above, the in-cylinder pressure sensor 13 corresponds to the “in-cylinder pressure sensor” according to the first aspect of the present invention. Further, here, the ECU 50 executes the process of step 100, so that the “estimated in-cylinder pressure calculating means” and the “abnormal combustion determining means” in the second invention execute the process of step 110. The “ignition cut means” in the third invention executes the process of step 120, and the “ideal heat generation amount acquisition means” in the first invention executes the process of step 130. When the “actual heat generation amount calculation means” in the first invention executes the process of step 140, the “heat generation amount determination means” in the first invention executes the process of step 150. The “retarding ignition means” in the first invention is realized.

Embodiment 2. FIG.
[System Configuration of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 9 described later in the configuration shown in FIG.

[Characteristic Control in Embodiment 2]
In the first embodiment described above, the occurrence of pre-ignition can be determined by the first process before the reference ignition timing by the spark plug 14. By the way, abnormal combustion occurs due to various factors. For example, when an increase in the frequency of occurrence of abnormal combustion due to oil accumulation or the like is taken into account, abnormal combustion may occur continuously in a short time. Further, not only pre-ignition, but also the possibility of large knocking occurring immediately after ignition by the spark plug 14 is conceivable. Specifically, as shown in FIG. 4 described above, the timing at which abnormal combustion is determined may be very close to the reference ignition timing. Further, according to the inventor's knowledge, there is a case where it intersects with the ignition timing. Such abnormal combustion becomes conspicuous in an operation region (abnormal combustion occurrence region) such as a low rotation high load region.

  Therefore, in the system of the present embodiment, the reference ignition timing is retarded in the abnormal combustion occurrence region.

(Control routine)
FIG. 9 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described function. This routine is the same as the routine shown in FIG. 8 except that the process of step 200 is added before step 100. In FIG. 9, the same steps as those shown in FIG. 8 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 9, first, in step 200, it is determined whether or not the operation region is an abnormal combustion occurrence region. For example, when the operation region is a low rotation and high load, it is determined that the region is in the abnormal combustion occurrence region. The abnormal combustion occurrence region differs depending on the internal combustion engine, and a condition value based on an experiment or the like is stored in the ECU 50 in advance. When it is determined that the region is the abnormal combustion occurrence region, the ECU 50 retards the reference ignition timing. Specifically, the ECU 50 stores a relationship map showing the relationship between torque and ignition timing shown in FIG. The retard amount of the reference ignition timing is calculated from this engagement map within a range that satisfies the required torque.

  As described above, according to the routine shown in FIG. 9, the final period at which abnormal combustion can be determined can be delayed by retarding the basic ignition timing in accordance with the operating region. Therefore, the range in which abnormal combustion can be determined before the reference ignition timing is widened, and abnormal combustion that occurs near the compression top dead center can also be determined with high accuracy. In addition, since the second process (ignition cut control) of the first embodiment described above can be performed with high certainty, engine damage can be prevented.

  In the second embodiment described above, the ECU 50 executes the processing of step 200 to realize the “operation region determination means” and the “reference ignition timing retarding means” in the fourth invention. .

Embodiment 3 FIG.
[System Configuration of Embodiment 3]
Next, a third embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 12 described later in the configuration shown in FIG.

[Characteristic Configuration in Embodiment 3]
In the first embodiment described above, when it is determined that abnormal combustion occurs before the reference ignition timing, ignition cut control for cutting off the ignition by the spark plug 14 is performed by the second process, and the engine is damaged. Can be prevented. However, there may be a case where unburned gas is generated or drivability deteriorates by performing the ignition cut control. It is more desirable to prevent engine breakage and to solve these problems.

  Next, an outline of control of this embodiment that solves such a problem will be described with reference to FIG. FIG. 11 is a diagram showing the relationship between the heat generation position and the maximum value of the in-cylinder pressure. As shown in FIG. 11, if the intake air amount and the air-fuel ratio are constant, the sensitivity of the maximum value of the in-cylinder pressure has a large sensitivity at the heat generation position (ignition timing). According to the inventor's knowledge, it is possible to easily estimate the maximum value of the in-cylinder pressure from the compression end temperature and the ignition timing by estimating the compression end temperature based on the intake air temperature and the in-cylinder air amount. I found out that

  Therefore, in the system of the present embodiment, first, the maximum value of the in-cylinder pressure is estimated from the ignition timing at which abnormal combustion is determined to occur and the compression end temperature. Then, when the estimated maximum value of the in-cylinder pressure is equal to or less than a set value related to engine durability, the above-described ignition cut control is not performed. On the other hand, when it is larger than the set value, the above-described ignition cut control is performed.

  FIG. 12 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described function. This routine is the same as the routine shown in FIG. 9 except that steps 300 to 320 are added between step 100 and step 110. In FIG. 12, the same steps as those shown in FIG. 9 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 12, first, in step 300, the ignition timing and the compression end temperature when it is determined that abnormal combustion occurs are acquired. Here, the ignition timing is the crank angle at the time of abnormality determination in step 100 described above. The compression end temperature can be calculated from the state equation based on the in-cylinder intake air amount and the intake air temperature.

  Next, in step 310, the maximum in-cylinder pressure in the cylinder in the current cycle is estimated. Specifically, the ECU 50 stores a relationship map indicating the relationship between the heat generation position (ignition timing) and the maximum value of the in-cylinder pressure shown in FIG. 12 described above for each compression end temperature. Using the compression end temperature and ignition timing acquired in step 300, the maximum in-cylinder pressure Pmax in the cylinder in the current cycle is estimated from this relationship map.

  Subsequently, it is determined whether the maximum in-cylinder pressure Pmax estimated in step 310 is larger than a set value determined by engine design requirements (including a safety factor) (step 320). When the estimated maximum in-cylinder pressure Pmax is larger than the set value, the processing after step 200 is performed to perform the ignition cut. On the other hand, if it is lower than this set value, the routine is terminated without performing the ignition cut.

  As described above, according to the routine shown in FIG. 12, the ignition cut control is performed when the estimated maximum in-cylinder pressure Pmax is equal to or lower than the set value even when it is determined that abnormal combustion occurs. do not do. Therefore, even if it is determined that abnormal combustion occurs, under conditions where the durability of the engine is sufficiently ensured, it is possible to suppress overheating of the catalyst and deterioration of drivability due to unburned gas. . Further, when the estimated maximum in-cylinder pressure Pmax is higher than the set value, the ignition cut control can be performed with certainty, so that the engine can be prevented from being damaged. For this reason, according to the system of the present embodiment, it is possible to minimize overheating of the catalyst and deterioration of drivability due to unburned gas while preventing damage to the engine.

  In the third embodiment described above, the ECU 50 executes the process of step 310, whereby the “maximum in-cylinder pressure estimating means” in the fifth aspect of the invention executes the process of step 320. The “durability determination means” in the fifth invention is realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Injector 13 In-cylinder pressure sensor 14 Spark plug 18 Exhaust passage 20 Turbo supercharger 22 Intake passage 24 Start catalyst 26 Air flow meter 30 Throttle valve 34 Intake pressure sensor 42 Crank angle sensor 44 Air fuel ratio sensor 46 Intake temperature sensor 50 ECU

Claims (5)

An in-cylinder pressure sensor for measuring the in-cylinder pressure;
An actual heat generation amount calculating means for calculating an actual heat generation amount in the cylinder based on an actual measurement value of the in-cylinder pressure sensor at a predetermined crank angle during a combustion stroke;
An ideal heat generation amount acquisition means for acquiring an ideal heat generation amount in the cylinder based on the fuel injection amount;
Heat generation amount determination means for determining whether the actual heat generation amount is lower than a predetermined ratio of the ideal heat generation amount;
Retard ignition means for igniting the spark plug near the bottom dead center before the exhaust stroke when the actual heat generation amount is lower than a predetermined ratio of the ideal heat generation amount;
A control device for an internal combustion engine, comprising: An estimated in-cylinder pressure calculating means for calculating an estimated value of the in-cylinder pressure that changes until the ignition timing by the spark plug (hereinafter referred to as a reference ignition timing) based on the intake pipe pressure;
Abnormal combustion determination that determines that abnormal combustion occurs when the measured value of the in-cylinder pressure sensor at a predetermined crank angle up to the reference ignition timing is higher than the estimated value calculated by the estimated in-cylinder pressure calculating means by a predetermined value or more. Means further comprising:
The retard ignition means is in the vicinity of the bottom dead center before the exhaust stroke when it is determined that the abnormal combustion occurs and the actual heat generation amount is lower than a predetermined ratio of the ideal heat generation amount. Igniting the spark plug,
The control device for an internal combustion engine according to claim 1. When it is determined that the abnormal combustion occurs, further comprising ignition cut means for cutting ignition by the spark plug at the reference ignition timing;
The control device for an internal combustion engine according to claim 2. Operation region determination means for determining whether or not the operation region is an abnormal combustion occurrence region;
4. The control apparatus for an internal combustion engine according to claim 2, further comprising reference ignition timing retarding means for retarding the reference ignition timing in the abnormal combustion occurrence region. Maximum in-cylinder pressure estimating means for estimating the maximum value of in-cylinder pressure based on the crank angle and the compression end temperature determined to cause the abnormal combustion;
Durability determination means for determining whether the maximum value of the in-cylinder pressure is larger than a set value related to the durability of the internal combustion engine;
The ignition cut means cuts the ignition by the spark plug at the reference ignition timing when it is determined that the abnormal combustion occurs when the maximum value of the in-cylinder pressure is larger than the set value;
The control apparatus for an internal combustion engine according to claim 3 or 4, characterized by the above.

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