JP2015158163A - Spark-ignition internal combustion engine controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect and suppress the occurrence of preignition without detecting a cylinder pressure.SOLUTION: In Step S101, it is determined whether a cylinder lower than the other cylinders in an exhaust gas temperature in the same cycle by a set amount ΔTex or more is present. If a determination result of Step S101 is YES, it is determined that preignition occurs in Step S103. In subsequent cycles, a preignition avoidance control is executed over at least the cylinder for which it is determined that the preignition occurs.

Description

  The present invention relates to a control device for a spark ignition type internal combustion engine, and more particularly to control for suppressing preignition (premature ignition) of a spark ignition type internal combustion engine.

  In a spark ignition internal combustion engine, abnormal combustion due to pre-ignition may occur. Preignition is a phenomenon in which an air-fuel mixture in a cylinder is self-ignited by the heat of the spark plug itself or exfoliated carbon before the normal ignition timing by the spark plug. This pre-ignition tends to occur repeatedly once it occurs. If pre-ignition occurs repeatedly, the in-cylinder pressure may rise abnormally high and the engine may be damaged. Therefore, it is desirable to detect and suppress the occurrence of pre-ignition.

  In the following Patent Document 1, the occurrence of preignition is detected from the compression pressure ratio between the compression pressure at the top dead center and the reference in-cylinder pressure during the compression stroke, and the rate of change of the in-cylinder pressure with respect to the crank angle. In the following Patent Document 2, the occurrence of pre-ignition is detected by comparing the in-cylinder pressure predicted by the physical model with the actual in-cylinder pressure. In Patent Document 3 below, an index value of the calorific value is calculated from the in-cylinder pressure measurement value, and the occurrence of pre-ignition is detected from the index value.

JP 2005-9457 A JP 2010-71284 A JP 2012-225321 A JP 2003-206796 A

  In Patent Documents 1 to 3, an in-cylinder pressure sensor for detecting the pressure in the engine cylinder is necessary to detect the occurrence of pre-ignition. Since the in-cylinder pressure sensor is installed in the engine cylinder, it may break due to abnormal combustion such as pre-ignition or knocking, and it is necessary to ensure durability against high-pressure and high-temperature in-cylinder gas immediately after combustion. Furthermore, the in-cylinder pressure sensor is expensive, resulting in high costs.

  An object of the present invention is to detect and suppress the occurrence of pre-ignition without detecting the in-cylinder pressure.

  The control device for a spark ignition internal combustion engine according to the present invention employs the following means in order to achieve the above-described object.

  A control device for a spark ignition type internal combustion engine according to the present invention is a control device for a spark ignition type internal combustion engine having a plurality of cylinders, wherein an exhaust state in which a physical quantity representing an exhaust gas state of each cylinder is measured for each cycle. Pre-ignition to different cylinders based on the exhaust conditions in which there are cylinders whose physical quantities differ by more than a set amount compared to other cylinders in the physical quantity of each cylinder in the same cycle measured by the measuring means and the exhaust state measuring means Pre-ignition determination means for determining that pre-ignition has occurred, and pre-ignition avoidance for executing pre-ignition avoidance control for at least a cylinder determined to have generated pre-ignition in a cycle after it is determined that pre-ignition has occurred And a means.

  In one aspect of the present invention, the physical quantity is an exhaust gas temperature, and the pre-ignition determination means includes a cylinder having an exhaust gas temperature that is lower than a set amount by the exhaust gas temperature of each cylinder in the same cycle as compared to other cylinders. It is preferable to determine that pre-ignition has occurred in the low cylinder based on the existing exhaust conditions.

  In one aspect of the present invention, the pre-ignition determination means satisfies the exhaust condition, and further, in the low cylinder, the difference between the exhaust gas temperature and the intake gas temperature is a predetermined value or more, or the exhaust gas temperature is a lower limit. When the value is equal to or greater than the value, it is preferable to determine that preignition has occurred in the low cylinder.

  In one aspect of the present invention, the physical quantity is an exhaust gas pressure, and the pre-ignition determination means includes a cylinder having an exhaust gas pressure that is lower than a set amount by the exhaust gas pressure of each cylinder in the same cycle. It is preferable to determine that pre-ignition has occurred in the low cylinder based on the existing exhaust conditions.

  In one aspect of the present invention, the pre-ignition determination means satisfies the exhaust condition, and further, in the low cylinder, the difference between the exhaust gas pressure and the intake gas pressure is a predetermined value or more, or the exhaust gas pressure is a lower limit. When the value is equal to or greater than the value, it is preferable to determine that preignition has occurred in the low cylinder.

  In one aspect of the present invention, the physical quantity is a hydrocarbon concentration in the exhaust gas, and the pre-ignition determination means has a hydrocarbon concentration in the exhaust gas of each cylinder in the same cycle as compared with other cylinders. It is preferable to determine that pre-ignition has occurred in the high cylinder based on an exhaust condition in which there is a cylinder having a concentration higher than the set amount.

  In one aspect of the present invention, the pre-ignition determination means determines that pre-ignition has occurred in the high cylinder when the exhaust condition is satisfied and the hydrocarbon concentration in the high cylinder is not more than an upper limit value. Is preferred.

  In one aspect of the present invention, the physical quantity is a nitrogen oxide concentration in the exhaust gas, and the pre-ignition determination means is compared with other cylinders in the nitrogen oxide concentration in the exhaust gas of each cylinder in the same cycle. It is preferable to determine that pre-ignition has occurred in the high cylinder based on the exhaust conditions in which there is a cylinder having a nitrogen oxide concentration higher than a set amount.

  Further, the control device for the spark ignition type internal combustion engine according to the present invention includes an exhaust state measuring means for measuring a physical quantity representing the state of the exhaust gas of the cylinder for each cycle, and each cycle measured by the exhaust state measuring means. Pre-ignition determination means for determining that pre-ignition has occurred, based on exhaust conditions in which the physical amount differs by a set amount or more compared to the previous cycle in which the fuel injection amount and ignition timing are substantially the same, and pre-ignition has occurred And a pre-ignition avoidance unit that executes pre-ignition avoidance control in a cycle after the determination is made.

  In one aspect of the present invention, the physical quantity is an exhaust gas temperature, and the pre-ignition determination means has an exhaust gas temperature at the exhaust gas temperature in each cycle as compared with the previous cycle in which the fuel injection amount and the ignition timing are substantially the same. It is preferable to determine that pre-ignition has occurred based on the exhaust conditions lower than the set amount.

  In one aspect of the present invention, the pre-ignition determination unit is configured such that when the exhaust condition is satisfied and the difference between the exhaust gas temperature and the intake gas temperature is a predetermined value or more, or the exhaust gas temperature is a lower limit value or more. In addition, it is preferable to determine that pre-ignition has occurred.

  In one aspect of the present invention, the physical quantity is an exhaust gas pressure, and the pre-ignition determination means has an exhaust gas pressure compared to the previous cycle in which the fuel injection amount and the ignition timing are substantially the same in the exhaust gas pressure in each cycle. It is preferable to determine that pre-ignition has occurred based on the exhaust conditions lower than the set amount.

  In one aspect of the present invention, the pre-ignition determination means is configured such that when the exhaust condition is satisfied and the difference between the exhaust gas pressure and the intake gas pressure is a predetermined value or more, or the exhaust gas pressure is a lower limit value or more. In addition, it is preferable to determine that pre-ignition has occurred.

  In one aspect of the present invention, the physical quantity is a hydrocarbon concentration in the exhaust gas, and the pre-ignition determination means has substantially the same fuel injection amount and ignition timing in the hydrocarbon concentration in the exhaust gas in each cycle. It is preferable to determine that pre-ignition has occurred based on exhaust conditions in which the hydrocarbon concentration is higher than the set amount by comparison with the previous cycle.

  In one aspect of the present invention, it is preferable that the pre-ignition determination means determine that pre-ignition has occurred when the exhaust condition is satisfied and the hydrocarbon concentration is equal to or lower than an upper limit value.

  In one aspect of the present invention, the physical quantity is a nitrogen oxide concentration in the exhaust gas, and the pre-ignition determination means has substantially the same fuel injection amount and ignition timing in the nitrogen oxide concentration in the exhaust gas in each cycle. It is preferable to determine that pre-ignition has occurred based on exhaust conditions in which the nitrogen oxide concentration is higher than the set amount by comparison with the previous cycle.

  In one aspect of the present invention, it is preferable that the pre-ignition avoidance unit executes pre-ignition avoidance control for all cylinders in a cycle after it is determined that pre-ignition has occurred.

  In one aspect of the present invention, the pre-ignition avoidance control is preferably control for increasing the fuel injection amount.

  In one aspect of the present invention, the preignition avoidance control is preferably control for stopping fuel injection.

  According to the present invention, in the physical quantity representing the state of the exhaust gas in each cylinder in the same cycle, the exhaust condition in which there is a cylinder having a physical quantity different from the other cylinder by a set amount or more compared to the other cylinders, or the state of the exhaust gas in each cycle In-cylinder pressure is detected by determining the occurrence of pre-ignition based on exhaust conditions in which the physical quantity differs by a set amount or more compared to the previous cycle in which the fuel injection amount and ignition timing are substantially the same. The occurrence of pre-ignition can be detected and suppressed.

It is a figure showing an example of composition of a spark ignition type internal combustion engine to which a control device concerning an embodiment of the present invention is applied. It is a figure which shows the structural example of each cylinder of a spark ignition type internal combustion engine. It is a figure which shows an example of the change with respect to the crank angle of the in-cylinder pressure when preignition occurs. It is a flowchart which shows an example of the preignition detection and avoidance control which are performed by the electronic controller. It is a figure which shows the other structural example of each cylinder of a spark ignition type internal combustion engine.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  1 and 2 are diagrams illustrating a configuration example of a spark ignition internal combustion engine 1 to which a control device according to an embodiment of the present invention is applied. FIG. 1 shows an example of the overall configuration of a spark ignition type internal combustion engine 1, and FIG. 2 shows an example of the configuration of each cylinder 11 of the spark ignition type internal combustion engine 1. Although FIG. 2 shows a configuration for one cylinder, the other cylinders have the same configuration. The spark ignition internal combustion engine 1 is constituted by a gasoline engine, for example, and has a plurality of cylinders 11. Although FIG. 1 shows an example of four cylinders, the number of cylinders can be arbitrarily set. The plurality of cylinders 11 are formed by a cylinder block 9 and a cylinder head 10, and a piston 12 that reciprocates in the axial direction is accommodated in each cylinder 11. A space surrounded by the top surface 12 a of the piston 12, the inner wall surface 9 a of the cylinder block 9, and the lower surface 10 a of the cylinder head 10 forms a combustion chamber 13. An intake port 14 that communicates with the combustion chamber 13 and an exhaust port 15 that communicates with the combustion chamber 13 are formed in the cylinder head 10. Further, an intake valve 16 that opens and closes the boundary between the intake port 14 and the combustion chamber 13 and an exhaust valve 17 that opens and closes the boundary between the exhaust port 15 and the combustion chamber 13 are provided. Further, the cylinder head 10 is provided with a fuel injection valve (injector) 19 and a spark plug (ignition plug) 23 facing the inside of the combustion chamber 13. In the following description, when it is necessary to distinguish a plurality (four) of cylinders 11, the following description will be made using reference numerals 11-1 to 11-4.

  In the spark ignition internal combustion engine 1, one cycle is constituted by the intake stroke, the compression stroke, the expansion stroke, and the exhaust stroke. For example, fuel (for example, hydrocarbon fuel such as gasoline) is directly injected into the combustion chamber 13 from the fuel injection valve 19 in the intake stroke or compression stroke, and a mixture of fuel and air is formed in the cylinder 11. Here, it is possible to pressurize the intake gas into the cylinder 11 with a supercharger such as a turbocharger. Then, by spark-igniting the air-fuel mixture in the combustion chamber 13 by spark discharge of the spark plug 23 at the ignition timing, the air-fuel mixture in the combustion chamber 13 is subjected to flame propagation combustion. Power for rotating a crankshaft (not shown) is generated by this flame propagation combustion. The exhaust gas after combustion in the combustion chamber 13 is discharged to the exhaust port 15 by opening the exhaust valve 17 in the exhaust stroke. The fuel injection amount from the fuel injection valve 19 and the ignition timing by the spark plug 23 are controlled by an electronic control unit (ECU) 30 based on the engine speed and the engine load (engine torque), and each cylinder 11-1 to 11- The fuel injection amount and the ignition timing in the same cycle of 4 are controlled to be equal to each other.

  In the spark ignition internal combustion engine 1, abnormal combustion may occur due to pre-ignition (premature ignition). Preignition is a phenomenon in which the air-fuel mixture in the combustion chamber 13 is self-ignited by the heat of the spark plug 23 itself, exfoliated carbon, etc. before the normal ignition timing by the spark plug 23. When pre-ignition occurs, As shown in FIG. 3, as compared with the normal combustion by the spark plug 23, the combustion timing is greatly advanced and the in-cylinder pressure rises abnormally high. Once pre-ignition occurs, it tends to occur repeatedly, and pre-ignition is likely to occur particularly in a low-rotation and high-load operation region or a supercharged engine. Hereinafter, control for detecting occurrence of pre-ignition and avoiding continuous occurrence of pre-ignition will be described. In the following description, the case where pre-ignition occurs in the cylinder 11-1 will be described, but the same applies to the case where pre-ignition occurs in any of the other cylinders 11-2 to 11-4.

  In the cylinder head 10, an exhaust gas temperature sensor 25 is installed facing the exhaust port 15 corresponding to each cylinder 11-1 to 11-4. The exhaust gas temperature sensor 25 is responsive enough to measure the temperature for each cycle, and is preferably arranged upstream of the exhaust port 15 (side closer to the combustion chamber 13) within a range not interfering with the exhaust valve 17. . The exhaust gas temperature sensor 25 measures the exhaust gas temperatures Tex1 to Tex4 of the cylinders 11-1 to 11-4 for each cycle as physical quantities representing the exhaust gas states of the cylinders 11-1 to 11-4. Signals indicating the exhaust gas temperatures Tex1 to Tex4 for each cycle measured by the exhaust gas temperature sensor 25 are input to the electronic control unit 30.

  In the electronic control unit 30, the pre-ignition determination unit 32 (exhaust gas temperatures Tex1 to Tex4 of the cylinders 11-1 to 11-4 in the same cycle measured by the exhaust gas temperature sensor 25 (physical quantity indicating the state of the exhaust gas). ) Are compared with each other, and the occurrence of pre-ignition is determined based on the exhaust conditions in which there are cylinders whose exhaust gas temperature is lower than the set amount ΔTex compared to other cylinders. At that time, as the exhaust gas temperatures Tex1 to Tex4 in one cycle, the exhaust gas temperature when the exhaust valve 17 is open (exhaust stroke) is used. When pre-ignition occurs in a certain cylinder, the fuel injection amount and the ignition timing are the same because the combustion timing is greatly advanced compared to a cylinder in which pre-ignition has not occurred (a cylinder in which normal combustion is performed by the spark plug 23). However, the state of the exhaust gas is different. For example, if pre-ignition occurs in a certain cylinder and the combustion timing is greatly advanced, the amount of heat that escapes to the surroundings after combustion increases compared to a cylinder that does not generate pre-ignition, so the exhaust gas temperature decreases. Therefore, the occurrence of pre-ignition can be detected by detecting the decrease in the exhaust gas temperature. For example, when an exhaust condition in which the exhaust gas temperature Tex1 of the cylinder 11-1 is lower than the exhaust gas temperatures Tex2 to Tex4 of the other cylinders 11-2 to 11-4 by a set amount ΔTex is satisfied in the same cycle (current cycle). The pre-ignition determination unit 32 determines that pre-ignition has occurred in the cylinder 11-1 whose exhaust gas temperature Tex1 is low (exhaust gas state is different). On the other hand, in the exhaust gas temperatures Tex1 to Tex4 of the respective cylinders 11-1 to 11-4 in the current cycle, when there is no cylinder whose exhaust gas temperature is lower than the set amount ΔTex as compared with other cylinders, the preignition determination unit No. 32 determines that pre-ignition has not occurred in each of the cylinders 11-1 to 11-4. Here, the set amount ΔTex is set to a value larger than the variation in the exhaust gas temperature during normal combustion under the same conditions for the fuel injection amount and the ignition timing, for example, a value of about 10 ° C.

  The pre-ignition avoidance control unit 34 performs pre-ignition avoidance control in a cycle after the pre-ignition determination unit 32 determines that pre-ignition has occurred. For example, if it is determined that pre-ignition has occurred in the cylinder 11-1, pre-ignition avoidance control is executed on at least the cylinder 11-1. On the other hand, when the pre-ignition determination unit 32 determines that pre-ignition has not occurred, the pre-ignition avoidance control unit 34 does not execute pre-ignition avoidance control for all the cylinders 11-1 to 11-4. .

  As an example of pre-ignition avoidance control, control is performed to stop fuel injection to the cylinder 11-1 for several cycles after it is determined that pre-ignition has occurred in the cylinder 11-1. By performing fuel cut for several cycles, it is possible to avoid repeated pre-ignition. Further, as preignition avoidance control, during several cycles after it is determined that preignition has occurred in the cylinder 11-1, control is performed to increase the fuel injection amount of the cylinder 11-1 compared to when preignition occurs. Is also possible. By increasing the fuel injection amount for several cycles, it is possible to reduce the gas temperature in the cylinder 11-1 and to suppress the pre-ignition.

  Further, the pre-ignition avoidance control may be executed not only on the cylinder 11-1 determined to have generated the pre-ignition but also on the other cylinders 11-2 to 11-4 in which the pre-ignition has not occurred. It is possible, and it is also possible to carry out with respect to all the cylinders 11-1 to 11-4. For example, during several cycles after it is determined that pre-ignition has occurred in the cylinder 11-1, not only the fuel injection amount of the cylinder 11-1 but also the fuel injection amounts of the other cylinders 11-2 to 11-4 are pre-ignition. It is also possible to perform control to increase from the determination of occurrence, and it is also possible to perform control to increase the fuel injection amount of all the cylinders 11-1 to 11-4. Thus, preignition that may occur in the other cylinders 11-2 to 11-4 can be suppressed in advance.

  An example of pre-ignition detection and avoidance control executed by the electronic control unit 30 is shown in the flowchart of FIG. In step S101, the pre-ignition determination unit 32 determines whether or not there is a cylinder whose exhaust gas temperature in the same cycle is lower than the set amount ΔTex compared to other cylinders. If the determination result in step S101 is NO, the pre-ignition determination unit 32 determines that the pre-ignition is not detected in step S102, and the pre-ignition avoidance control is not executed. On the other hand, if the determination result in step S101 is YES, the pre-ignition determination unit 32 determines that pre-ignition is detected in step S103, and the pre-ignition avoidance control is executed in the pre-ignition avoidance control unit 34 in step S104. The

  According to the present embodiment described above, the physical quantity representing the state of the exhaust gas is different from the other cylinders 11-2 to 11-4 in the same cycle by a set amount or more (the exhaust gas temperature is lower than the set amount ΔTex). It can be detected that pre-ignition has occurred in the cylinder 11-1 based on the exhaust conditions in which 11-1 exists. At that time, since the exhaust gas temperature sensor 25 that detects the exhaust gas temperatures Tex1 to Tex4 is detected at a position that is not in the cylinder, compared to the in-cylinder pressure sensor that detects the pressure in the cylinder, There is no need to increase durability and the cost can be reduced. In a cycle after it is determined that pre-ignition has occurred, the pre-ignition continuous control can be avoided by executing pre-ignition avoidance control on at least the cylinder 11-1. Therefore, the occurrence of pre-ignition can be detected and suppressed by an inexpensive method without detecting the pressure in each of the cylinders 11-1 to 11-4 using an expensive in-cylinder pressure sensor.

  Hereinafter, another method for detecting occurrence of pre-ignition will be described.

  In the present embodiment, as shown in FIG. 5, in addition to the exhaust gas temperature sensor 25, an intake gas temperature sensor 24 is installed facing the intake port 14 for each of the cylinders 11-1 to 11-4. It may be. The intake gas temperature sensor 24 has a response sufficient to measure the temperature for each cycle, and is preferably disposed downstream of the intake port 14 (side closer to the combustion chamber 13) within a range not interfering with the intake valve 16. . The intake gas temperature sensor 24 measures the intake gas temperatures Tin1 to Tin4 of the cylinders 11-1 to 11-4 for each cycle as a physical quantity representing the state of the intake gas of the cylinders 11-1 to 11-4. Signals indicating the intake gas temperatures Tin <b> 1 to Tin <b> 4 for each cycle measured by the intake gas temperature sensor 24 are input to the electronic control unit 30.

  The pre-ignition determination unit 32 determines the occurrence of pre-ignition as a condition for determining the occurrence of pre-ignition, in addition to the exhaust condition in which there exists a cylinder whose exhaust gas temperature is lower than the set amount ΔTex in comparison with other cylinders in the same cycle. It is also possible to add a condition in which the difference between the exhaust gas temperature and the intake gas temperature is equal to or greater than a predetermined value ΔTg in a cylinder having a low value. At this time, the intake gas temperature when the intake valve 16 is open (intake stroke) is used as the intake gas temperatures Tin1 to Tin4 in one cycle. In addition to abnormal combustion due to pre-ignition, the exhaust gas temperature also decreases in the case of misfire due to poor ignition. However, when misfire occurs, the temperature of the intake gas rises due to compression, but when the temperature decreases due to expansion and is discharged as exhaust gas, it is heated by the combustion chamber 13 or cooled by the latent heat of the fuel. The temperature changes to a small extent, and the temperature difference between the exhaust gas and the intake gas is small. Therefore, when the exhaust gas temperature and the intake gas temperature are compared and the temperature difference is sufficiently large, it can be determined that there is no misfire. For example, in the same cycle (current cycle), an exhaust condition is established in which the exhaust gas temperature Tex1 of the cylinder 11-1 is lower than the exhaust gas temperatures Tex2 to Tex4 of the other cylinders 11-2 to 11-4 by a set amount ΔTex. When the difference Tex1-Tin1 between the exhaust gas temperature Tex1 and the intake gas temperature Tin1 in the current cycle in the cylinder 11-1 is equal to or greater than the predetermined value ΔTg, the preignition determination unit 32 causes misfire in the cylinder 11-1. It is determined that pre-ignition has occurred. On the other hand, if the difference Tex1-Tin1 between the exhaust gas temperature Tex1 and the intake gas temperature Tin1 in the current cycle in the cylinder 11-1 is smaller than the predetermined value ΔTg even if the above exhaust condition is satisfied, the preignition determination unit 32 Determines that pre-ignition has not occurred in the cylinder 11-1 and misfire has occurred. The predetermined value ΔTg here is set to a value larger than the temperature difference between the exhaust gas and the intake gas at the time of misfire occurrence, for example, set to a value of about 50 ° C. According to this configuration example, it is possible to improve the determination accuracy of occurrence of pre-ignition. At this time, since the intake gas temperature sensor 24 is also detected at a position other than in the cylinder, it is not necessary to increase durability against high pressure and high temperature as compared with an in-cylinder pressure sensor that detects pressure in the cylinder. Is cheaper.

  The pre-ignition determination unit 32 determines the occurrence of pre-ignition as a condition for determining the occurrence of pre-ignition, in addition to the exhaust condition in which there exists a cylinder whose exhaust gas temperature is lower than the set amount ΔTex in comparison with other cylinders in the same cycle. It is also possible to add a condition in which the exhaust gas temperature of the cylinder with low is not less than the lower limit value Tlim. When a misfire occurs, the amount of decrease in the exhaust gas temperature is greatly increased compared to when pre-ignition occurs, so it can be determined from the exhaust gas temperature whether it is a pre-ignition or a misfire. . For example, in the same cycle (current cycle), an exhaust condition is established in which the exhaust gas temperature Tex1 of the cylinder 11-1 is lower than the exhaust gas temperatures Tex2 to Tex4 of the other cylinders 11-2 to 11-4 by a set amount ΔTex. When the exhaust gas temperature Tex1 in the current cycle in the cylinder 11-1 is equal to or higher than the lower limit value Tlim, the preignition determination unit 32 determines that no misfire has occurred in the cylinder 11-1 and that preignition has occurred. . On the other hand, if the exhaust gas temperature Tex1 in the current cycle in the cylinder 11-1 is lower than the lower limit value Tlim even if the above exhaust condition is satisfied, the preignition determination unit 32 generates preignition in the cylinder 11-1. It is determined that misfire has occurred. The lower limit value Tlim here is set to a value higher than the exhaust gas temperature at the time of misfire occurrence, for example, set to a value of about 50 to 300 ° C. Also in this configuration example, the determination accuracy of the occurrence of pre-ignition can be improved, and the intake gas temperature sensor 24 becomes unnecessary.

  In the present embodiment, instead of the exhaust gas temperature sensor 25, an exhaust gas pressure sensor may be installed facing the exhaust port 15 corresponding to each cylinder 11-1 to 11-4. The exhaust gas pressure sensor is also preferably arranged on the upstream side (side closer to the combustion chamber 13) of the exhaust port 15 within a range that does not interfere with the exhaust valve 17 and has a response that can measure the pressure for each cycle. The exhaust gas pressure sensors measure the exhaust gas pressures Pex1 to Pex4 of the cylinders 11-1 to 11-4 for each cycle as physical quantities representing the exhaust gas states of the cylinders 11-1 to 11-4. Signals indicating the exhaust gas pressures Pex <b> 1 to Pex <b> 4 for each cycle measured by the exhaust gas pressure sensor are input to the electronic control unit 30.

  The pre-ignition determination unit 32 compares the exhaust gas pressures Pex1 to Pex4 of the cylinders 11-1 to 11-4 in the same cycle measured by the exhaust gas pressure sensor with each other, and compares the exhaust gas with other cylinders. It is also possible to determine the occurrence of pre-ignition based on the exhaust conditions where there is a cylinder whose pressure is lower than the set amount ΔPex. At that time, as the exhaust gas pressures Pex1 to Pex4 in one cycle, the exhaust gas pressure when the exhaust valve 17 is open (exhaust stroke) is used. When preignition occurs in a certain cylinder and the combustion timing is greatly advanced, the expansion period of the in-cylinder gas after combustion is longer than that of a cylinder where no preignition has occurred (normal combustion cylinder by the spark plug 23). It becomes longer and the exhaust gas pressure decreases. Therefore, the occurrence of pre-ignition can be detected by detecting the decrease in the exhaust gas pressure. For example, when an exhaust condition in which the exhaust gas pressure Pex1 of the cylinder 11-1 is lower than the exhaust gas pressures Pex2 to Pex4 of the other cylinders 11-2 to 11-4 by a set amount ΔPex is satisfied in the same cycle (current cycle). The pre-ignition determination unit 32 determines that pre-ignition has occurred in the cylinder 11-1 having a low exhaust gas pressure Pex1. On the other hand, in the exhaust gas pressures Pex1 to Pex4 of the respective cylinders 11-1 to 11-4 in the current cycle, when there are no cylinders whose exhaust gas pressure is lower than the set amount ΔPex as compared with other cylinders, the preignition determination unit No. 32 determines that pre-ignition has not occurred in each of the cylinders 11-1 to 11-4. Here, the set amount ΔPex is set to a value larger than the variation of the exhaust gas pressure during normal combustion under the same conditions, for example, the fuel injection amount and the ignition timing, and is set to a value of about 20 kPa, for example. Since the exhaust gas pressure sensors that detect the exhaust gas pressures Pex1 to Pex4 are also detected at a position that is not in the cylinder, it is necessary to increase durability against high pressure and high temperature compared to the in-cylinder pressure sensor that detects the pressure in the cylinder. There is no cost.

  Furthermore, instead of the intake gas temperature sensor 24, an intake gas pressure sensor may be installed facing the intake port 14 corresponding to each cylinder 11-1 to 11-4. The intake gas pressure sensor is also preferably arranged on the downstream side (side closer to the combustion chamber 13) of the intake port 14 within a range that does not interfere with the intake valve 16 and has a response that can measure the pressure for each cycle. By the intake gas pressure sensor, the intake gas pressures Pin1 to Pin4 of each cylinder 11-1 to 11-4 are measured for each cycle as a physical quantity representing the state of the intake gas of each cylinder 11-1 to 11-4. A signal indicating the intake gas pressures Pin1 to Pin4 for each cycle measured by the intake gas pressure sensor is input to the electronic control unit 30.

  The pre-ignition determination unit 32 determines the occurrence of pre-ignition as a condition for determining the occurrence of pre-ignition, in addition to the exhaust condition in which the exhaust gas pressure is lower than the other cylinder by a set amount ΔPex in the same cycle. It is also possible to add a condition that the difference between the exhaust gas pressure and the intake gas pressure is equal to or greater than a predetermined value ΔPg in a cylinder with a low value. At that time, the intake gas pressure when the intake valve 16 is open (intake stroke) is used as the intake gas pressures Pin1 to Pin4 in one cycle. In addition to abnormal combustion due to pre-ignition, the exhaust gas pressure also decreases in the case of misfire due to poor ignition. However, when a misfire occurs, the pressure difference between the exhaust gas and the intake gas is greatly reduced as compared to the case where pre-ignition occurs. Therefore, when the exhaust gas pressure is compared with the intake gas pressure and the pressure difference is sufficiently large, it can be determined that there is no misfire. For example, in the same cycle (current cycle), an exhaust condition in which the exhaust gas pressure Pex1 of the cylinder 11-1 is lower than the exhaust gas pressures Pex2 to Tex4 of the other cylinders 11-2 to 11-4 by a set amount ΔPex is satisfied. When the difference Pex1-Pin1 between the exhaust gas pressure Pex1 and the intake gas pressure Pin1 in the current cycle in the cylinder 11-1 is equal to or greater than the predetermined value ΔPg, the preignition determination unit 32 causes a misfire in the cylinder 11-1. It is determined that pre-ignition has occurred. On the other hand, if the difference Pex1-Pin1 between the exhaust gas pressure Pex1 and the intake gas pressure Pin1 in the current cycle in the cylinder 11-1 is smaller than the predetermined value ΔPg even if the above exhaust condition is satisfied, the preignition determination unit 32 Determines that pre-ignition has not occurred in the cylinder 11-1 and misfire has occurred. The predetermined value ΔPg here is set to a value larger than the pressure difference between the exhaust gas and the intake gas at the time of misfiring, for example, a value of about 0.05 MPa. Also in this configuration example, it is possible to improve the determination accuracy of occurrence of pre-ignition. At that time, since the intake gas pressure sensor is also detected at a position other than in the cylinder, it is not necessary to increase the durability against high pressure and high temperature compared to the in-cylinder pressure sensor that detects the pressure in the cylinder, and the cost is also increased. It's cheap.

  Further, the pre-ignition determination unit 32 determines the occurrence of pre-ignition as a condition for determining the occurrence of pre-ignition, in addition to the exhaust condition in which there is a cylinder whose exhaust gas pressure is lower than the set amount ΔPex in comparison with other cylinders in the same cycle. It is also possible to add a condition in which the exhaust gas pressure of the cylinder with a low is not less than the lower limit Plim. When misfire occurs, the amount of decrease in exhaust gas pressure is significantly increased compared to when pre-ignition occurs, so it is possible to determine whether pre-ignition or misfire from the exhaust gas pressure. . For example, in the same cycle (current cycle), an exhaust condition is established in which the exhaust gas pressure Pex1 of the cylinder 11-1 is lower than the exhaust gas pressures Pex2 to Pex4 of the other cylinders 11-2 to 11-4 by a set amount ΔPex. When the exhaust gas pressure Pex1 in the current cycle in the cylinder 11-1 is equal to or higher than the lower limit value Plim, the preignition determination unit 32 determines that no misfire has occurred in the cylinder 11-1 and that preignition has occurred. . On the other hand, if the exhaust gas pressure Pex1 in the current cycle in the cylinder 11-1 is lower than the lower limit value Plim even if the above exhaust condition is satisfied, the preignition determination unit 32 generates preignition in the cylinder 11-1. It is determined that misfire has occurred. Here, the lower limit value Plim is set to a value higher than the exhaust gas pressure at the time of misfire occurrence, for example, a value of about the intake gas pressure +20 kPa. Also in this configuration example, it is possible to improve the determination accuracy of occurrence of pre-ignition.

  In this embodiment, instead of the exhaust gas temperature sensor 25 and the exhaust gas pressure sensor, a hydrocarbon concentration sensor (HC concentration sensor) is provided in the exhaust port 15 corresponding to each cylinder 11-1 to 11-4. It may be installed facing you. The HC concentration sensor is also responsive enough to measure the hydrocarbon concentration (HC concentration) for each cycle, and is arranged upstream of the exhaust port 15 (side closer to the combustion chamber 13) within a range not interfering with the exhaust valve 17. It is preferable to do. By the HC concentration sensor, the unburned hydrocarbon concentration (unburned HC concentration) Hex1 to Hex1 in the exhaust gas of each cylinder 11-1 to 11-4 as a physical quantity representing the state of the exhaust gas of each cylinder 11-1 to 11-4. Hex4 is measured for each cycle. A signal indicating the unburned HC concentration Hex1 to Hex4 for each cycle measured by the HC concentration sensor is input to the electronic control unit 30.

  Then, the preignition determination unit 32 compares the unburned HC concentrations Hex1 to Hex4 of the cylinders 11-1 to 11-4 in the same cycle measured by the HC concentration sensor with each other, and unburned compared to other cylinders. It is also possible to determine the occurrence of pre-ignition based on the exhaust conditions in which there are cylinders whose HC concentration is higher than the set amount ΔHex. At that time, as the unburned HC concentration Hex1 to Hex4 in one cycle, the unburned HC concentration when the exhaust valve 17 is open (exhaust stroke) is used. When pre-ignition occurs in a cylinder and the combustion timing is greatly advanced, the in-cylinder gas temperature in the expansion stroke decreases as compared to a cylinder in which pre-ignition does not occur (cylinder of normal combustion by the spark plug 23). As a result, the unburned HC concentration in the exhaust gas increases. Therefore, the occurrence of pre-ignition can be detected by detecting the increase in the unburned HC concentration. For example, in the same cycle (current cycle), an exhaust condition is established in which the unburned HC concentration Hex1 of the cylinder 11-1 is higher than the unburned HC concentrations Hex2 to Hex4 of the other cylinders 11-2 to 11-4 by a set amount ΔHex. At this time, the preignition determination unit 32 determines that preignition has occurred in the cylinder 11-1 having a high unburned HC concentration Hex1. On the other hand, in the unburned HC concentrations Hex1 to Hex4 of the cylinders 11-1 to 11-4 in the current cycle, when there are no cylinders whose unburned HC concentration is higher than the set amount ΔHex compared to other cylinders, pre-ignition The determination unit 32 determines that pre-ignition has not occurred in each of the cylinders 11-1 to 11-4. Here, the set amount ΔHex is set to a value larger than the variation in the unburned HC concentration during normal combustion under the same conditions for the fuel injection amount and the ignition timing, for example, set to a value of about 500 ppm. The HC concentration sensor that detects the unburned HC concentration Hex1 to Hex4 is also detected at a position that is not in the cylinder, so it is necessary to increase durability against high pressure and high temperature compared to the in-cylinder pressure sensor that detects pressure in the cylinder. There is no cost.

  Further, the pre-ignition determination unit 32 determines the occurrence of pre-ignition as a condition for determining the occurrence of pre-ignition, in addition to the exhaust condition in which there is a cylinder in which the unburned HC concentration is higher than the set amount ΔHex in comparison with other cylinders in the same cycle. It is also possible to add a condition in which the unburned HC concentration of the cylinder having a high HC concentration is not more than the upper limit value Hlim. In addition to abnormal combustion due to pre-ignition, in the case of misfire due to poor ignition, the unburned HC concentration in the exhaust gas also increases. However, if a misfire occurs, the amount of increase in the unburned HC concentration in the exhaust gas will increase significantly compared to when pre-ignition occurs. It can be determined whether there is. For example, an exhaust condition in which the unburned HC concentration Hex1 of the cylinder 11-1 is higher than the unburned HC concentrations Hex2 to Hex4 of the other cylinders 11-2 to 11-4 by a set amount ΔHex or more is established in the same cycle (current cycle). Furthermore, when the unburned HC concentration Hex1 in the current cycle in the cylinder 11-1 is equal to or less than the upper limit value Hlim, the preignition determination unit 32 has not misfired in the cylinder 11-1, and has generated preignition. Is determined. On the other hand, even if the above exhaust condition is satisfied, when the unburned HC concentration Hex1 in the current cycle in the cylinder 11-1 is higher than the upper limit value Hlim, the preignition determination unit 32 causes preignition to occur in the cylinder 11-1. It is determined that a misfire has not occurred. The upper limit value Hlim here is set to a value lower than the unburned HC concentration at the time of misfire occurrence, for example, about 0.1 to 2%. Also in this configuration example, it is possible to improve the determination accuracy of occurrence of pre-ignition.

  In the present embodiment, instead of the exhaust gas temperature sensor 25, the exhaust gas pressure sensor, and the HC concentration sensor, a nitrogen oxide concentration sensor (NOx concentration sensor) is provided for each cylinder 11-1 to 11-4. It may be installed facing the exhaust port 15. The NOx concentration sensor is also responsive enough to measure the nitrogen oxide concentration (NOx concentration) for each cycle, and upstream of the exhaust port 15 (side closer to the combustion chamber 13) within a range not interfering with the exhaust valve 17. It is preferable to arrange. By the NOx concentration sensor, nitrogen oxide concentrations (NOx concentrations) Nex1 to Nex4 in the exhaust gases of the cylinders 11-1 to 11-4 are respectively represented as physical quantities representing the exhaust gas states of the cylinders 11-1 to 11-4. Measured every cycle. A signal indicating the NOx concentration Nex1 to Nex4 for each cycle measured by the NOx concentration sensor is input to the electronic control unit 30.

  Then, the pre-ignition determination unit 32 compares the NOx concentrations Nex1 to Nex4 of the cylinders 11-1 to 11-4 in the same cycle measured by the NOx concentration sensor with each other, and the NOx concentration is set as compared with the other cylinders. It is also possible to determine the occurrence of pre-ignition based on the exhaust conditions in which there are cylinders higher than the amount ΔNex. At that time, as the NOx concentration Nex1 to Nex4 in one cycle, the NOx concentration when the exhaust valve 17 is open (exhaust stroke) is used. If preignition occurs in a certain cylinder and the combustion timing is greatly advanced, the combustion temperature becomes higher than in a cylinder in which preignition does not occur (normal combustion cylinder by the spark plug 23), and in the exhaust gas. The NOx concentration increases. Therefore, the occurrence of pre-ignition can be detected by detecting the increase in the NOx concentration. For example, in the same cycle (current cycle), when an exhaust condition in which the NOx concentration Nex1 of the cylinder 11-1 is higher than the NOx concentrations Nex2 to Nex4 of the other cylinders 11-2 to 11-4 by a set amount ΔNex is satisfied. The ignition determination unit 32 determines that pre-ignition has occurred in the cylinder 11-1 having a high NOx concentration Nex1. On the other hand, in the NOx concentrations Nex1 to Nex4 of the respective cylinders 11-1 to 11-4 in the current cycle, when there is no cylinder having a NOx concentration higher than the set amount ΔNex as compared with the other cylinders, the preignition determination unit 32 It is determined that no pre-ignition has occurred in each of the cylinders 11-1 to 11-4. Here, the set amount ΔNex is set to a value larger than the variation in the NOx concentration during normal combustion under the same conditions for the fuel injection amount and the ignition timing, for example, a value of about 300 ppm. Since the NOx concentration sensor that detects the NOx concentrations Nex1 to Nex4 is also detected at a position that is not in the cylinder, there is no need to increase durability against high pressure and high temperature compared to an in-cylinder pressure sensor that detects pressure in the cylinder. The cost is low. Note that when misfire due to poor ignition occurs, the concentration of NOx in the exhaust gas decreases, unlike when preignition occurs.

  In the above embodiment, the occurrence of pre-ignition is determined by comparing the physical quantities representing the exhaust gas states of the cylinders 11-1 to 11-4 in the same cycle. However, in this embodiment, it is also possible to determine the occurrence of pre-ignition by comparing physical quantities representing the exhaust gas states of the cylinders 11-1 to 11-4 in different cycles. In the following description, the case where pre-ignition occurs in the cylinder 11-1 will be described, but the same applies to the case where pre-ignition occurs in any of the other cylinders 11-2 to 11-4.

  The pre-ignition determination unit 32 performs fuel at the exhaust gas temperatures Tex1 (t) to Tex4 (t) (t is time) of each cylinder 11-1 to 11-4 in each cycle measured by the exhaust gas temperature sensor 25. It is also possible to determine the occurrence of pre-ignition based on exhaust conditions in which there are cylinders in which the exhaust gas temperature in the current cycle is lower than the set amount ΔTex compared to the previous cycle in which the injection amount and ignition timing are the same (or substantially the same). Is possible. At this time, as the exhaust gas temperatures Tex1 (t) to Tex4 (t) in one cycle, the exhaust gas temperature when the exhaust valve 17 is open (exhaust stroke) is used. When pre-ignition occurs in a certain cycle, the fuel injection amount and ignition timing are reduced by a large advance of the combustion timing compared to the previous cycle where no pre-ignition has occurred (the normal combustion cycle by the spark plug 23). Despite being the same, the state of the exhaust gas is different. For example, if pre-ignition occurs in a certain cycle and the combustion timing is greatly advanced, the amount of heat that escapes to the surroundings after combustion increases compared to the previous cycle where pre-ignition has not occurred, so the exhaust gas temperature decreases. . Therefore, the occurrence of pre-ignition can be detected by detecting the decrease in the exhaust gas temperature. For example, in the cylinder 11-1, the exhaust gas temperature Tex1 (m) in the previous cycle (for example, one cycle before) in which the exhaust gas temperature Tex1 (n) in the current cycle has the same (or almost the same) fuel injection amount and ignition timing. When the exhaust condition lower than the set amount ΔTex is established as compared with (n> m), the preignition determination unit 32 determines that preignition has occurred in the cylinder 11-1. On the other hand, when the exhaust condition is not satisfied, the preignition determination unit 32 determines that preignition has not occurred in the cylinder 11-1. According to this configuration example, in the cylinder 11-1, the physical quantity indicating the state of the exhaust gas in the current cycle is the set amount, although the fuel injection amount and the ignition timing are the same (or almost the same) as in the previous cycle. Based on the different exhaust conditions (exhaust gas temperature is lower than the set amount ΔTex), it can be detected that preignition has occurred in the cylinder 11-1. Therefore, it can be applied not only to a multi-cylinder engine but also to a single-cylinder engine.

  Further, the pre-ignition determination unit 32 determines the occurrence of pre-ignition as a condition for determining the occurrence of pre-ignition, and the exhaust gas temperature in the current cycle is equal to or greater than the set amount ΔTex compared to the previous cycle in which the fuel injection amount and the ignition timing are the same (or substantially the same). In addition to the exhaust condition in which a low cylinder exists, it is also possible to add a condition in which the difference between the exhaust gas temperature in the current cycle and the intake gas temperature is equal to or greater than a predetermined value ΔTg in a cylinder with a low exhaust gas temperature. At that time, the intake gas temperature when the intake valve 16 is open (intake stroke) is used as the intake gas temperature Tin1 (t) to Tin4 (t) in one cycle. In addition to abnormal combustion due to pre-ignition, in the case of misfire due to poor ignition, the exhaust gas temperature also decreases, but if the temperature difference is sufficiently large by comparing the exhaust gas temperature and the intake gas temperature, it is determined that there is no misfire be able to. For example, in the cylinder 11-1, the exhaust gas temperature Tex1 (m) in the previous cycle (for example, one cycle before) in which the exhaust gas temperature Tex1 (n) in the current cycle has the same (or almost the same) fuel injection amount and ignition timing. The exhaust condition lower than the set amount ΔTex is established, and the difference Tex1 (n) −Tin1 (n) between the exhaust gas temperature Tex1 (n) of the current cycle and the intake gas temperature Tin1 (n) in the cylinder 11-1. ) Is equal to or greater than the predetermined value ΔTg, the preignition determination unit 32 determines that no misfire has occurred in the cylinder 11-1 and that preignition has occurred. On the other hand, even if the above exhaust condition is satisfied, the difference Tex1 (n) −Tin1 (n) between the exhaust gas temperature Tex1 (n) of the current cycle and the intake gas temperature Tin1 (n) in the cylinder 11-1 is a predetermined value. When smaller than ΔTg, the pre-ignition determination unit 32 determines that pre-ignition has not occurred in the cylinder 11-1 and misfire has occurred. According to this configuration example, it is possible to improve the determination accuracy of occurrence of pre-ignition.

  Further, the pre-ignition determination unit 32 determines that the occurrence of pre-ignition is a condition for the exhaust gas temperature of the current cycle to be equal to or greater than the set amount ΔTex as compared to the previous cycle in which the fuel injection amount and the ignition timing are the same (or substantially the same). In addition to the exhaust condition in which a low cylinder exists, it is possible to add a condition in which the exhaust gas temperature of the cylinder having a low exhaust gas temperature is equal to or higher than the lower limit value Tlim. When a misfire occurs, the amount of decrease in the exhaust gas temperature is greatly increased compared to when pre-ignition occurs, so it can be determined from the exhaust gas temperature whether it is a pre-ignition or a misfire. . For example, in the cylinder 11-1, the exhaust gas temperature Tex1 (m) in the previous cycle (for example, one cycle before) in which the exhaust gas temperature Tex1 (n) in the current cycle has the same (or almost the same) fuel injection amount and ignition timing. When the exhaust condition lower than the set amount ΔTex is established and the exhaust gas temperature Tex1 (n) in the current cycle in the cylinder 11-1 is equal to or higher than the lower limit value Tlim, the preignition determination unit 32 It is determined that pre-ignition has occurred because no misfire has occurred in -1. On the other hand, even if the above exhaust condition is satisfied, if the exhaust gas temperature Tex1 (n) in the current cycle in the cylinder 11-1 is lower than the lower limit value Tlim, the preignition determination unit 32 pre-applies to the cylinder 11-1. It is determined that no ignition has occurred and misfire has occurred. Also in this configuration example, the determination accuracy of the occurrence of pre-ignition can be improved, and the intake gas temperature sensor 24 becomes unnecessary.

  Further, the pre-ignition determination unit 32 determines the fuel injection amount and the ignition in the exhaust gas pressures Pex1 (t) to Pex4 (t) of each cylinder 11-1 to 11-4 in each cycle measured by the exhaust gas pressure sensor. It is also possible to determine the occurrence of pre-ignition based on the exhaust conditions in which there is a cylinder in which the exhaust gas pressure in the current cycle is lower than the set amount ΔPex compared to the previous cycle having the same (or almost the same) timing. At that time, as the exhaust gas pressures Pex1 (t) to Pex4 (t) in one cycle, the exhaust gas pressure when the exhaust valve 17 is open (exhaust stroke) is used. When pre-ignition occurs in a certain cycle and the combustion timing is greatly advanced, the in-cylinder gas expansion period after combustion is compared with the previous cycle in which pre-ignition has not occurred (the normal combustion cycle by the spark plug 23) Becomes longer and the exhaust gas pressure decreases. Therefore, the occurrence of pre-ignition can be detected by detecting the decrease in the exhaust gas pressure. For example, in the cylinder 11-1, the exhaust gas pressure Pex1 (m) in the previous cycle (for example, one cycle before) in which the exhaust gas pressure Pex1 (n) in the current cycle has the same (or almost the same) fuel injection amount and ignition timing. When the exhaust condition lower than the set amount ΔPex is established, the preignition determination unit 32 determines that preignition has occurred in the cylinder 11-1. On the other hand, when the exhaust condition is not satisfied, the preignition determination unit 32 determines that preignition has not occurred in the cylinder 11-1.

  Further, the pre-ignition determination unit 32 determines the occurrence of pre-ignition as a condition for determining the occurrence of pre-ignition, and the exhaust gas pressure in the current cycle is greater than or equal to the set amount ΔPex compared to the previous cycle in which the fuel injection amount and ignition timing are the same (or substantially the same) In addition to the exhaust condition in which a low cylinder exists, it is also possible to add a condition in which the difference between the exhaust gas pressure in the current cycle and the intake gas pressure is greater than or equal to a predetermined value ΔPg in a cylinder with a low exhaust gas pressure. At that time, the intake gas pressure when the intake valve 16 is open (intake stroke) is used as the intake gas pressure Pin1 (t) to Pin4 (t) in one cycle. In addition to abnormal combustion due to pre-ignition, in the case of misfiring due to poor ignition, the exhaust gas pressure decreases, but if the pressure difference is sufficiently large by comparing the exhaust gas pressure and the intake gas pressure, it is determined that there is no misfire be able to. For example, in the cylinder 11-1, the exhaust gas pressure Pex1 (m) in the previous cycle (for example, one cycle before) in which the exhaust gas pressure Pex1 (n) in the current cycle has the same (or almost the same) fuel injection amount and ignition timing. Exhaust condition lower than the set amount ΔPex is established, and the difference Pex1 (n) −Pin1 (n) between the exhaust gas pressure Pex1 (n) and the intake gas pressure Pin1 (n) in the current cycle in the cylinder 11-1 ) Is equal to or greater than the predetermined value ΔPg, the preignition determination unit 32 determines that no misfire has occurred in the cylinder 11-1 and that preignition has occurred. On the other hand, even if the above exhaust condition is satisfied, the difference Pex1 (n) −Pin1 (n) between the exhaust gas pressure Pex1 (n) and the intake gas pressure Pin1 (n) of the current cycle in the cylinder 11-1 is a predetermined value. When it is smaller than ΔPg, the preignition determination unit 32 determines that no preignition has occurred in the cylinder 11-1 and misfire has occurred. According to this configuration example, it is possible to improve the determination accuracy of occurrence of pre-ignition.

  Further, the pre-ignition determination unit 32 determines that the occurrence of pre-ignition is a condition in which the exhaust gas pressure in the current cycle is equal to or greater than the set amount ΔPex as compared to the previous cycle in which the fuel injection amount and the ignition timing are the same (or substantially the same). In addition to the exhaust condition in which a low cylinder exists, it is also possible to add a condition in which the exhaust gas pressure in a cylinder with a low exhaust gas pressure is equal to or higher than the lower limit value Plim. When misfire occurs, the amount of decrease in exhaust gas pressure is significantly increased compared to when pre-ignition occurs, so it is possible to determine whether pre-ignition or misfire from the exhaust gas pressure. . For example, in the cylinder 11-1, the exhaust gas pressure Pex1 (m) in the previous cycle (for example, one cycle before) in which the exhaust gas pressure Pex1 (n) in the current cycle has the same (or almost the same) fuel injection amount and ignition timing. When the exhaust condition lower than the set amount ΔPex is satisfied and the exhaust gas pressure Pex1 (n) in the current cycle in the cylinder 11-1 is equal to or higher than the lower limit value Plim, the preignition determination unit 32 It is determined that pre-ignition has occurred because no misfire has occurred in -1. On the other hand, even if the above exhaust condition is satisfied, when the exhaust gas pressure Pex1 (n) in the current cycle in the cylinder 11-1 is lower than the lower limit value Plim, the preignition determination unit 32 applies pre-compression to the cylinder 11-1. It is determined that no ignition has occurred and misfire has occurred. Also in this configuration example, the determination accuracy of the occurrence of pre-ignition can be improved, and an intake gas pressure sensor becomes unnecessary.

  Further, the pre-ignition determination unit 32 determines the fuel injection amount and the ignition in the unburned HC concentrations Hex1 (t) to Hex4 (t) of the cylinders 11-1 to 11-4 in each cycle measured by the HC concentration sensor. It is also possible to determine the occurrence of pre-ignition based on the exhaust conditions in which there is a cylinder in which the unburned HC concentration in the current cycle is higher than the set amount ΔHex compared to the previous cycle having the same (or almost the same) timing. . At that time, as the unburned HC concentration Hex1 (t) to Hex4 (t) in one cycle, the unburned HC concentration when the exhaust valve 17 is open (exhaust stroke) is used. When pre-ignition occurs in a certain cycle and the combustion timing is greatly advanced, the in-cylinder gas temperature in the expansion stroke is higher than that in the previous cycle in which pre-ignition has not occurred (the normal combustion cycle by the spark plug 23). By decreasing, the unburned HC concentration in the exhaust gas increases. Therefore, the occurrence of pre-ignition can be detected by detecting the increase in the unburned HC concentration. For example, in the cylinder 11-1, the unburned HC concentration Hex1 (n) in the current cycle is the same as (or almost the same as) the fuel injection amount and the ignition timing. When the exhaust condition higher than the set amount ΔHex is established as compared with m), the preignition determination unit 32 determines that preignition has occurred in the cylinder 11-1. On the other hand, when the exhaust condition is not satisfied, the preignition determination unit 32 determines that preignition has not occurred in the cylinder 11-1.

  Further, the pre-ignition determination unit 32 sets the unburned HC concentration in the current cycle to a set amount ΔHex as a condition for determining the occurrence of pre-ignition as compared to the previous cycle in which the fuel injection amount and the ignition timing are the same (or substantially the same). In addition to the exhaust conditions in which there are high cylinders, it is possible to add a condition in which the unburned HC concentration of the cylinder having a high unburned HC concentration is equal to or lower than the upper limit value Hlim. When misfire occurs, compared to the case where pre-ignition occurs, the amount of increase in unburned HC concentration in the exhaust gas greatly increases, so whether it is pre-ignition or misfire from the unburned HC concentration Can be determined. For example, in the cylinder 11-1, the unburned HC concentration Hex1 (n) in the current cycle is the same as (or almost the same as) the fuel injection amount and the ignition timing. m), when the exhaust condition higher than the set amount ΔHex is satisfied and the unburned HC concentration Hex1 (n) in the current cycle in the cylinder 11-1 is equal to or lower than the upper limit value Hlim, the preignition determination unit 32 In 11-1, it is determined that no misfire has occurred and pre-ignition has occurred. On the other hand, even if the above exhaust condition is satisfied, when the unburned HC concentration Hex1 (n) in the current cycle in the cylinder 11-1 is higher than the upper limit value Hlim, the preignition determination unit 32 sets the cylinder 11-1 to the cylinder 11-1. It is determined that pre-ignition has not occurred and misfire has occurred. Also in this configuration example, it is possible to improve the determination accuracy of occurrence of pre-ignition.

  The pre-ignition determination unit 32 determines the fuel injection amount and the ignition timing in the NOx concentrations Nex1 (t) to Nex4 (t) of the cylinders 11-1 to 11-4 in each cycle measured by the NOx concentration sensor. It is also possible to determine the occurrence of pre-ignition based on the exhaust conditions in which there are cylinders in which the NOx concentration in the current cycle is higher than the set amount ΔNex compared to the same (or almost the same) previous cycle. At that time, as the NOx concentrations Nex1 (t) to Nex4 (t) in one cycle, the unburned HC concentration when the exhaust valve 17 is open (exhaust stroke) is used. If pre-ignition occurs in a certain cycle and the combustion timing is greatly advanced, the combustion temperature becomes higher in the exhaust gas as compared to the previous cycle in which pre-ignition has not occurred (the normal combustion cycle by the spark plug 23). NOx concentration increases. Therefore, the occurrence of pre-ignition can be detected by detecting the increase in the NOx concentration. For example, in the cylinder 11-1, the NOx concentration Nex1 (n) in the current cycle is compared with the NOx concentration Nex1 (m) in the previous cycle (for example, one cycle before) in which the fuel injection amount and the ignition timing are the same (or substantially the same). When the exhaust condition higher than the set amount ΔNex is established, the preignition determination unit 32 determines that preignition has occurred in the cylinder 11-1. On the other hand, when the exhaust condition is not satisfied, the preignition determination unit 32 determines that preignition has not occurred in the cylinder 11-1.

  Note that the pre-ignition determination unit 32 can detect the occurrence of pre-ignition by combining a plurality of the above-described pre-ignition determination methods.

  In the above embodiment, the spark ignition internal combustion engine 1 is a direct injection internal combustion engine in which fuel is directly injected into the combustion chamber 13. However, in the present embodiment, the spark ignition internal combustion engine 1 may be an internal combustion engine that injects fuel into the intake port 14.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to such embodiment at all, and it can implement with a various form in the range which does not deviate from the summary of this invention. Of course.

  DESCRIPTION OF SYMBOLS 1 Spark ignition internal combustion engine, 9 cylinder block, 10 cylinder head, 11 cylinder, 12 piston, 13 combustion chamber, 14 intake port, 15 exhaust port, 16 intake valve, 17 exhaust valve, 19 fuel injection valve, 23 spark plug, 24 Intake gas temperature sensor, 25 Exhaust gas temperature sensor, 30 Electronic control unit, 32 Preignition determination unit, 34 Preignition avoidance control unit

Claims (19)

A control device for a spark ignition internal combustion engine having a plurality of cylinders,
An exhaust state measuring means for measuring a physical quantity representing an exhaust gas state of each cylinder for each cycle;
In the physical quantity of each cylinder in the same cycle measured by the exhaust state measuring means, pre-ignition has occurred in the different cylinders based on the exhaust condition in which there are cylinders whose physical quantities differ by more than a set amount compared to other cylinders. Pre-ignition determining means for determining;
Pre-ignition avoidance means for performing pre-ignition avoidance control on at least a cylinder determined to have generated pre-ignition in a cycle after it has been determined that pre-ignition has occurred;
A control device for a spark ignition type internal combustion engine. A control device for a spark ignition internal combustion engine according to claim 1,
The physical quantity is the exhaust gas temperature,
The pre-ignition determination means generates pre-ignition in the low cylinders based on the exhaust conditions in which there is a cylinder whose exhaust gas temperature is lower than the set amount by the exhaust gas temperature of each cylinder in the same cycle. A control device for a spark ignition type internal combustion engine, which is determined to have been. A control device for a spark ignition internal combustion engine according to claim 2,
The pre-ignition determination means, when the exhaust condition is satisfied, and further, in the low cylinder, when the difference between the exhaust gas temperature and the intake gas temperature is a predetermined value or more, or the exhaust gas temperature is a lower limit value or more, A control device for a spark ignition internal combustion engine, which determines that pre-ignition has occurred in the low cylinder. A control device for a spark ignition internal combustion engine according to claim 1,
The physical quantity is the exhaust gas pressure;
The pre-ignition judgment means generates pre-ignition in the low cylinder based on the exhaust condition in which the exhaust gas pressure of each cylinder in the same cycle is lower than the other cylinders by a set amount or lower than the other cylinders. A control device for a spark ignition type internal combustion engine, which is determined to have been. A control device for a spark ignition internal combustion engine according to claim 4,
The pre-ignition determination means, when the exhaust condition is satisfied, and further, in the low cylinder, the difference between the exhaust gas pressure and the intake gas pressure is a predetermined value or more, or the exhaust gas pressure is a lower limit value or more, A control device for a spark ignition internal combustion engine, which determines that pre-ignition has occurred in the low cylinder. A control device for a spark ignition internal combustion engine according to claim 1,
The physical quantity is a hydrocarbon concentration in the exhaust gas,
The pre-ignition determination means determines the high cylinder based on the exhaust conditions in which there is a cylinder whose hydrocarbon concentration in the exhaust gas of each cylinder in the same cycle is higher than the other cylinder by a predetermined amount or more compared to the other cylinders. A control device for a spark ignition internal combustion engine that determines that pre-ignition has occurred. A control device for a spark ignition type internal combustion engine according to claim 6,
The pre-ignition determination means determines whether pre-ignition has occurred in the high cylinder when the exhaust condition is satisfied and the hydrocarbon concentration in the high cylinder is not more than an upper limit value. Control device. A control device for a spark ignition internal combustion engine according to claim 1,
The physical quantity is the nitrogen oxide concentration in the exhaust gas,
The pre-ignition determination means has a high nitrogen oxide concentration in the exhaust gas of each cylinder in the same cycle based on an exhaust condition in which there is a cylinder having a nitrogen oxide concentration higher than a set amount by comparison with other cylinders. A control device for a spark ignition internal combustion engine that determines that pre-ignition has occurred in a cylinder. A control device for a spark ignition internal combustion engine,
Exhaust state measuring means for measuring a physical quantity representing the state of the exhaust gas of the cylinder for each cycle;
It is determined that pre-ignition has occurred based on the exhaust conditions where the physical quantity in each cycle measured by the exhaust state measurement means differs from the previous cycle in which the fuel injection quantity and ignition timing are substantially the same by at least the set quantity. Pre-ignition determination means for
Pre-ignition avoidance means for executing pre-ignition avoidance control in a cycle after it is determined that pre-ignition has occurred,
A control device for a spark ignition type internal combustion engine. The spark ignition type internal combustion engine control device according to claim 9,
The physical quantity is the exhaust gas temperature,
The pre-ignition determination means is that the pre-ignition occurred at the exhaust gas temperature in each cycle based on the exhaust conditions in which the exhaust gas temperature is lower than the set amount compared to the previous cycle in which the fuel injection amount and the ignition timing are substantially the same. A control device for a spark ignition internal combustion engine. A control device for a spark ignition internal combustion engine according to claim 10,
The pre-ignition determination means generates pre-ignition when the exhaust condition is satisfied and the difference between the exhaust gas temperature and the intake gas temperature is a predetermined value or more, or the exhaust gas temperature is a lower limit value or more. A control device for a spark ignition internal combustion engine. The spark ignition type internal combustion engine control device according to claim 9,
The physical quantity is the exhaust gas pressure;
The pre-ignition determination means is that the pre-ignition occurs in the exhaust gas pressure in each cycle based on the exhaust condition in which the exhaust gas pressure is lower than the set amount compared to the previous cycle in which the fuel injection amount and the ignition timing are substantially the same. A control device for a spark ignition internal combustion engine. A control device for a spark ignition internal combustion engine according to claim 12,
The pre-ignition determination means generates pre-ignition when the exhaust condition is satisfied and the difference between the exhaust gas pressure and the intake gas pressure is a predetermined value or more, or the exhaust gas pressure is a lower limit value or more. A control device for a spark ignition internal combustion engine. The spark ignition type internal combustion engine control device according to claim 9,
The physical quantity is a hydrocarbon concentration in the exhaust gas,
The pre-ignition determination means is based on exhaust conditions in which the hydrocarbon concentration in the exhaust gas in each cycle is higher than the set amount by the hydrocarbon concentration compared to the previous cycle in which the fuel injection amount and ignition timing are substantially the same. A control device for a spark ignition type internal combustion engine, which determines that an ignition has occurred. The control device for a spark ignition type internal combustion engine according to claim 14,
The pre-ignition determination means is a control device for a spark ignition internal combustion engine, which determines that pre-ignition has occurred when the exhaust condition is satisfied and the hydrocarbon concentration is equal to or lower than an upper limit value. The spark ignition type internal combustion engine control device according to claim 9,
The physical quantity is the nitrogen oxide concentration in the exhaust gas,
The pre-ignition determination means is based on the exhaust conditions in which the nitrogen oxide concentration in the exhaust gas in each cycle is higher than the set amount by the nitrogen oxide concentration compared to the previous cycle where the fuel injection amount and ignition timing are substantially the same. A control device for a spark ignition internal combustion engine that determines that pre-ignition has occurred. A control device for a spark ignition type internal combustion engine according to any one of claims 1 to 16,
The pre-ignition avoidance means is a control device for a spark ignition internal combustion engine that executes pre-ignition avoidance control for all cylinders in a cycle after it is determined that pre-ignition has occurred. A control device for a spark ignition type internal combustion engine according to any one of claims 1 to 17,
The preignition avoidance control is a control device for a spark ignition internal combustion engine, which is control for increasing the fuel injection amount. A control device for a spark ignition type internal combustion engine according to any one of claims 1 to 17,
The preignition avoidance control is a control device for a spark ignition type internal combustion engine, which is control for stopping fuel injection.

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