JP2013100730A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the presence or absence of abnormal combustion in a combustion chamber by a simple configuration without depending on a cylinder inner pressure sensor.SOLUTION: An internal combustion engine 1 includes a crankcase inner pressure sensor 51 for detecting the inner pressure of a crankcase. An electronic control device 50 determines the presence or absence of abnormal combustion in a combustion chamber 16 based on the detection result of the crankcase inner pressure sensor 51. More specifically, the electronic control device detects the presence of abnormal combustion when crankcase inner pressure detected by the crankcase inner pressure sensor 51 reaches predetermined pressure or higher that exceeds an upper limit of pressure generated when combustion is carried out normally in the operating state of the engine at that time.

Description

  The present invention relates to a control device for an internal combustion engine that determines whether or not abnormal combustion such as pre-ignition has occurred in a combustion chamber.

  Conventionally, as a control device of this type of internal combustion engine, for example, there is a device described in Patent Document 1. Conventional internal combustion engine control devices including the device described in Patent Document 1 include an in-cylinder pressure sensor for detecting the pressure in the cylinder, and abnormal combustion such as pre-ignition is performed based on the detection result of the sensor. It is determined whether or not it has occurred.

JP 2007-170345 A

  Incidentally, when an abnormality occurs in the in-cylinder pressure sensor, it is impossible to determine whether or not the abnormal combustion has occurred. In particular, an internal combustion engine equipped with a supercharger has a higher combustion pressure than a naturally aspirated internal combustion engine. Therefore, when the above-described abnormal combustion occurs, the pressure in the cylinder is further increased, and an abnormality is likely to occur in the in-cylinder pressure sensor.

  Such a problem is particularly noticeable in a control device for an internal combustion engine equipped with a supercharger, but it occurs in the same way even in an internal combustion engine not equipped with a supercharger although the frequency is low.

  The present invention has been made in view of such circumstances, and an object of the present invention is to control an internal combustion engine that can determine whether or not abnormal combustion has occurred in a combustion chamber with a simple configuration without relying on an in-cylinder pressure sensor. Is to provide.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
(1) The invention according to claim 1 is a control device for controlling an internal combustion engine, comprising a crankcase internal pressure sensor for detecting a pressure in a crankcase of the internal combustion engine, and combustion based on a detection result of the crankcase internal pressure sensor. The gist is to determine the presence or absence of abnormal combustion in the room.

  When abnormal combustion such as pre-ignition occurs in the combustion chamber, the pressure in the cylinder increases, and the pressure in the crankcase increases accordingly. According to the above configuration, the crankcase pressure sensor detects the crankcase pressure, and the presence or absence of abnormal combustion in the combustion chamber is determined based on the detection result. For this reason, the presence or absence of the abnormal combustion can be determined by only one crankcase internal pressure sensor. Therefore, the presence or absence of abnormal combustion in the combustion chamber can be determined with a simple configuration without depending on the in-cylinder pressure sensor.

  (2) According to the invention described in claim 1, as in the invention described in claim 2, the pressure in the crankcase detected by the crankcase internal pressure sensor is such that normal combustion is performed in the engine operating state at that time. This embodiment can be embodied in such a manner that it is determined that the abnormal combustion has occurred when the pressure exceeds a predetermined pressure that is greater than the upper limit value of the pressure that is generated.

(3) The gist of the invention described in claim 3 is that, in the control device for an internal combustion engine according to claim 2, the predetermined pressure is variably set according to the engine operating state at that time.
The pressure in the crankcase when the combustion is normally performed in the combustion chamber (hereinafter referred to as normal pressure) varies depending on the engine operating state at that time, for example, the engine speed and the engine load. Further, the pressure in the crankcase when abnormal combustion occurs in the combustion chamber (hereinafter referred to as abnormal pressure) becomes higher than the normal pressure in the engine operating state at that time. Therefore, if the predetermined pressure used for determining abnormal combustion is a fixed value corresponding to only a specific engine operating state, the abnormal combustion can be accurately determined only in the specific engine operating state, and abnormal combustion Opportunities that allow accurate determination are limited.

  In this regard, according to the above configuration, the predetermined pressure used for the determination of abnormal combustion is variably set according to the engine operating state at that time, so that the determination of abnormal combustion can be accurately performed regardless of the engine operating state. become able to. Therefore, it is possible to accurately increase the execution chance of the abnormal combustion determination.

(4) The invention according to claim 4 is the gist of the control device for an internal combustion engine according to claim 3, wherein the predetermined pressure is learned and updated for each engine operating state.
Even in the same engine operating state, the normal-time pressure changes as the internal combustion engine changes with time. Therefore, if the predetermined pressure used for abnormality determination is a fixed value with respect to a predetermined engine operating state, the presence or absence of occurrence of abnormal combustion in the combustion chamber is determined when the internal-combustion engine changes over time due to changes over time, etc. There is a possibility that it cannot be determined accurately.

  In this regard, according to the above configuration, since the predetermined pressure used for abnormality determination is learned and updated for each engine operating state, the predetermined pressure can be updated to an appropriate value according to the state of the internal combustion engine at that time. become able to. Therefore, it is possible to accurately determine whether or not abnormal combustion has occurred in the combustion chamber.

  (5) The invention according to claim 5 is the control apparatus for an internal combustion engine according to any one of claims 2 to 4, wherein the crankcase pressure detected by the crankcase internal pressure sensor is predetermined. The gist is not to determine that the abnormal combustion has occurred when the pressure exceeds the predetermined pressure over a period of time.

  The internal combustion engine is provided with a blow-by gas recirculation device for recirculating blow-by gas in the crankcase to the intake passage for processing. In such an internal combustion engine, the pressure in the crankcase may increase due to the passage connecting the crankcase and the intake passage being blocked. For this reason, when it is determined that the abnormal combustion has occurred only when the crankcase pressure detected by the crankcase internal pressure sensor becomes equal to or higher than the predetermined pressure, abnormal combustion actually occurs. There is a risk of misjudgment that abnormal combustion has occurred even though it is not.

  Here, when abnormal combustion such as pre-ignition occurs in the combustion chamber, the pressure increase in the crankcase accompanying this is an instantaneous phenomenon, whereas the passage connecting the crankcase and the intake passage is blocked. The resulting increase in pressure in the crankcase is a phenomenon that continues for a long time.

  According to the above configuration, when the pressure in the crankcase detected by the crankcase internal pressure sensor becomes equal to or higher than the predetermined pressure for a predetermined time or more, it is not determined that the abnormal combustion has occurred. Accordingly, it is possible to accurately suppress erroneous determination that abnormal combustion has occurred even though abnormal combustion has not actually occurred.

  (6) The invention according to claim 6 is the control apparatus for an internal combustion engine according to any one of claims 1 to 5, further comprising an in-cylinder pressure sensor for detecting a pressure in the cylinder for each cylinder. The gist is to determine whether or not the abnormal combustion has occurred based on the detection result of the in-cylinder pressure sensor.

  The in-cylinder pressure sensor directly detects the pressure in the combustion chamber, whereas the crankcase internal pressure sensor detects the pressure in the crankcase that changes according to the pressure in the combustion chamber. Therefore, even if abnormal combustion occurs in the combustion chamber, if the degree is small, the occurrence of abnormal combustion can be accurately determined from the detection result of the in-cylinder pressure sensor, but from the detection result of the crankcase internal pressure sensor. May not be able to determine the occurrence of the abnormal combustion.

  According to the above configuration, since the presence / absence of occurrence of the abnormal combustion is determined based on the detection result of the in-cylinder pressure sensor, it is possible to accurately determine the occurrence of abnormal combustion with a small degree. Further, even when an abnormality occurs in the crankcase internal pressure sensor, it is possible to accurately determine whether or not the abnormal combustion has occurred.

  (7) The invention according to claim 7 is the control device for an internal combustion engine according to claim 6, wherein the abnormality is generated based on a detection result of the crankcase internal pressure sensor when an abnormality occurs in the in-cylinder pressure sensor. The gist is to determine whether combustion has occurred.

  According to this configuration, when abnormality occurs in the in-cylinder pressure sensor, the presence or absence of occurrence of abnormal combustion in the combustion chamber is determined based on the detection result of the crankcase internal pressure sensor. Therefore, even when an abnormality occurs in the in-cylinder pressure sensor, it is possible to determine whether or not the abnormal combustion has occurred. Further, when there is no abnormality in the in-cylinder pressure sensor, the abnormal combustion is not determined based on the detection result of the crankcase internal pressure sensor. Therefore, in comparison with the control configuration for determining the presence or absence of occurrence of abnormal combustion based on the detection result of the in-cylinder pressure sensor, and in parallel to this, determining whether or not occurrence of abnormal combustion is based on the detection result of the crankcase internal pressure sensor, An increase in calculation load in the control device can be suitably suppressed.

  (8) The invention according to claim 8 is the internal combustion engine control apparatus according to claim 6, wherein the occurrence of abnormal combustion is detected based on the detection result of the crankcase internal pressure sensor and the detection result of the in-cylinder pressure sensor. And determining from the detection result of the crankcase internal pressure sensor that the abnormal combustion has occurred and from the detection result of the crankcase internal pressure sensor to determine that the abnormal combustion has not occurred. On the other hand, the gist is that the execution mode of the subsequent fail-safe process of the internal combustion engine is made different from the case where it is determined from the detection result of the in-cylinder pressure sensor that the abnormal combustion has occurred.

  The in-cylinder pressure sensor directly detects the pressure in the combustion chamber, whereas the crankcase internal pressure sensor detects the pressure in the crankcase that changes according to the pressure in the combustion chamber. Therefore, even if abnormal combustion occurs in the combustion chamber, if the degree is small, the occurrence of abnormal combustion can be accurately determined from the detection result of the in-cylinder pressure sensor, but from the detection result of the crankcase internal pressure sensor. May not be able to determine the occurrence of the abnormal combustion. From this, when it is determined from the detection result of the crankcase internal pressure sensor that the abnormal combustion has occurred, it can be said that the degree of the abnormal combustion is large. On the other hand, if it is determined from the detection result of the crankcase internal pressure sensor that the abnormal combustion has not occurred, and it is determined from the detection result of the in-cylinder pressure sensor that the abnormal combustion has occurred, the degree of the abnormal combustion Is small. According to the said structure, the execution aspect of the subsequent fail safe process of an internal combustion engine changes with the grades of the said abnormal combustion. Therefore, an appropriate fail-safe process can be performed according to the situation of the internal combustion engine.

Incidentally, as such fail-safe processing, a conventionally known method such as a method of reducing the intake air amount and the fuel injection amount or a method of retarding the ignition timing may be used.
(9) The invention according to claim 9 is characterized in that, in the control device for an internal combustion engine according to any one of claims 1 to 8, the internal combustion engine includes a supercharger.

  In an internal combustion engine equipped with a supercharger, in particular, since the combustion pressure becomes high and the pressure at the time of abnormality becomes high, abnormality tends to occur in the in-cylinder pressure sensor. In this regard, if the present invention is applied to a control device for an internal combustion engine equipped with a supercharger, the presence or absence of occurrence of abnormal combustion in the combustion chamber can be determined with a simple configuration without depending on the in-cylinder pressure sensor. become. Therefore, the configuration of the control device for the internal combustion engine can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows schematic structure of an internal combustion engine and an electronic control apparatus about the control apparatus of the internal combustion engine which concerns on 1st Embodiment of this invention. The flowchart which shows the procedure of the abnormal combustion determination process using the crankcase internal pressure sensor in the embodiment. The flowchart which shows the procedure of the predetermined pressure learning process in the embodiment. The graph which shows an example of transition of the crankcase internal pressure in the embodiment. The schematic diagram which shows schematic structure of an internal combustion engine and an electronic control apparatus about the control apparatus of the internal combustion engine which concerns on 2nd Embodiment of this invention. The flowchart which shows the procedure of the abnormal combustion determination process using the cylinder pressure sensor and crankcase internal pressure sensor in the embodiment. The flowchart which shows the procedure of the abnormal combustion determination process using the cylinder pressure sensor in 3rd Embodiment of this invention. The flowchart which shows the procedure of the fail safe process of the internal combustion engine in the embodiment.

[First Embodiment]
A first embodiment in which the control device for an internal combustion engine according to the present invention is embodied as a control device for an in-vehicle internal combustion engine equipped with an exhaust turbine supercharger will be described below with reference to FIGS. The internal combustion engine of this embodiment is an in-line 4-cylinder gasoline internal combustion engine that directly injects fuel into the cylinder.

FIG. 1 shows a schematic configuration of an internal combustion engine 1 of this embodiment and an electronic control device 50 that is a control device thereof. In FIG. 1, the cross-sectional structure of one cylinder 10 is shown.
A cylinder 10 is formed in the cylinder head 11 and the cylinder block 12 of the internal combustion engine 1, and a piston 14 is provided in the cylinder 10 so as to be capable of reciprocating. A combustion chamber 16 is defined by the top surface of the piston 14, the inner peripheral surface of the cylinder 10 formed in the cylinder head 11 and the cylinder block 12.

The internal combustion engine 1 is provided with an intake passage 2 for sucking air into the combustion chamber 16 and an exhaust passage 3 for discharging exhaust generated in the combustion chamber 16.
In the intake passage 2, a compressor housing 31, an intercooler 21, and a throttle body 22 are provided in this order from the upstream side.

  An impeller 32 that constitutes a compressor together with the compressor housing 31 is provided in the compressor housing 31. The impeller 32 is connected via a shaft to a turbine wheel (not shown) provided in the exhaust passage. The turbine wheel is surrounded by a turbine housing (not shown). The turbine is constituted by the turbine housing and the turbine wheel. The turbine and the compressor constitute an exhaust turbine supercharger (hereinafter referred to as a supercharger 30). In the internal combustion engine 1 provided with such a supercharger 30, when the turbine wheel is rotationally driven by the energy of the exhaust gas, the impeller 32 is rotationally driven along with this and supercharging is performed.

The intercooler 21 is a device for cooling air that has been supercharged by a compressor and has risen in temperature.
A throttle valve 23 that is opened and closed by a throttle motor 24 is provided in the throttle body 22. A surge tank is provided downstream of the throttle body 22 in the intake passage 2. An intake manifold is provided downstream of the surge tank in the intake passage 2, and a plurality of branch pipes of the intake manifold are connected to the intake ports of the respective cylinders 10. In the internal combustion engine 1, the flow rate of air supplied to the combustion chamber 16 is adjusted by changing the opening of the throttle valve 23. The opening degree control of the throttle valve 23 is performed by the electronic control unit 50.

  The cylinder head 11 is provided with a fuel injection valve 17 that directly injects fuel into the cylinder 10. The cylinder head 11 is provided with an ignition plug 18 for igniting an air-fuel mixture in which air supplied into the cylinder 10 and fuel injected from the fuel injection valve 17 are mixed. The fuel injection control by the fuel injection valve 17 and the ignition control by the ignition plug 18 are performed by the electronic control unit 50.

  A crankshaft 15 as an engine output shaft is rotatably provided in the crankcase 13 of the internal combustion engine 1. The crankshaft 15 is connected to the piston 14 via a connecting rod.

  Further, the internal combustion engine 1 is provided with a blow-by gas recirculation device 40 that treats the blow-by gas in the crankcase 13 by returning it to the intake passage 2 and combusting it with the air-fuel mixture in the combustion chamber 16. The blow-by gas recirculation device 40 includes a recirculation passage 41 that connects the inside of the crankcase 13 and the upstream side of the compressor housing 31 in the intake passage 2, and an electric PCV valve 42 provided in the middle of the recirculation passage 41. Yes. By changing the opening degree of the PCV valve 42, the flow rate of the blow-by gas recirculated from the crankcase 13 to the intake passage 2 is adjusted. The opening degree of the PCV valve 42 is controlled by the electronic control unit 50.

  Various controls of the internal combustion engine 1 are performed by the electronic control unit 50. The electronic control unit 50 temporarily stores a central processing unit (CPU) that performs arithmetic processing related to various controls, a read-only memory (ROM) that stores various control programs and data, and results of arithmetic processing. It comprises a random access memory (RAM) for storing. Then, the electronic control unit 50 reads the detection signals of various sensors, executes various arithmetic processes, and comprehensively controls the internal combustion engine 1 based on the results.

  The various sensors include an engine speed sensor that detects the engine speed NE, a throttle sensor that detects the throttle opening TA, which is the opening of the throttle valve 23, an air flow meter that detects the intake air amount, and a supercharging pressure. A supercharging pressure sensor, an air-fuel ratio sensor for detecting the air-fuel ratio of exhaust, a water temperature sensor for detecting the temperature of engine cooling water, and the like are provided. In addition, an accelerator sensor that detects an accelerator operation amount, a brake sensor that detects a brake operation amount, a vehicle speed sensor that detects a vehicle speed that is the traveling speed of the vehicle, and the like are provided. In the present embodiment, a crankcase internal pressure sensor 51 that detects the pressure in the crankcase 13 (hereinafter, crankcase internal pressure Pcrnk) is provided. The crankcase internal pressure sensor 51 is attached to the crankcase 13. These various sensors are electrically connected to the electronic control device 50. In the present embodiment, an in-cylinder pressure sensor that detects an in-cylinder pressure that is a pressure in each cylinder is not provided.

  By the way, in such an internal combustion engine 1, an oil mist contained in blow-by gas or the like flows into the combustion chamber 16, a deposit or the like attached to the top surface of the piston 14 serves as an ignition source, and an ignition plug There is a possibility that so-called pre-ignition occurs in which the air-fuel mixture is ignited earlier than the ignition timing by 18. As described above, when abnormal combustion occurs in the combustion chamber 16, the pressure in the cylinder 10 rises excessively. When the abnormal pressure increase in the cylinder 10 is repeated, there arises a problem that the durability of the internal combustion engine 1 is lowered.

  As described above, conventionally, an in-cylinder pressure sensor for detecting the pressure in the cylinder (hereinafter referred to as in-cylinder pressure) is provided for each cylinder, and whether abnormal combustion such as pre-ignition has occurred based on the detection result of each in-cylinder pressure sensor. Judgment is made.

  However, when an abnormality occurs in the in-cylinder pressure sensor, it is impossible to determine whether or not the abnormal combustion has occurred. Moreover, in the internal combustion engine 1 equipped with the supercharger 30, the combustion pressure is higher than that of the naturally aspirated internal combustion engine, and therefore the in-cylinder pressure when abnormal combustion occurs is further increased. Therefore, an abnormality is likely to occur in the in-cylinder pressure sensor.

  Therefore, in the present embodiment, in order to solve such inconvenience, the presence or absence of occurrence of abnormal combustion in the combustion chamber 16 is determined based on the detection result of the crankcase internal pressure sensor 51 through the electronic control unit 50.

  Next, an abnormal combustion determination process using the crankcase internal pressure sensor 51 will be described with reference to FIG. FIG. 2 is a flowchart showing the procedure of the abnormal combustion determination process. This series of processes is repeatedly executed at predetermined intervals by the electronic control unit 50 during engine operation.

As shown in FIG. 2, in this series of processes, first, in step S1, a predetermined pressure Pth used for the determination is set based on the engine speed NE and the engine load KL.
The predetermined pressure Pth is set to a value larger than the upper limit value of the pressure (normal pressure) generated when the crankcase internal pressure Pcrnk is normally combusted in the engine operating state at that time. The value is variably set according to the speed NE and the engine load KL. Specifically, the normal pressure increases as the engine speed NE increases and as the engine load KL increases. For this reason, the predetermined pressure Pth is set to a larger value as the engine speed NE is higher and as the engine load KL is higher.

  Here, the reason why the predetermined pressure Pth is variably set according to the engine operating state will be described. That is, the normal pressure varies depending on the engine operating state at that time, for example, the engine speed NE and the engine load KL. Further, the crankcase internal pressure Pcrnk (hereinafter referred to as abnormal pressure) when abnormal combustion occurs in the combustion chamber 16 becomes higher than the normal pressure in the engine operating state at that time. Therefore, if the predetermined pressure Pth used for the determination of abnormal combustion is a fixed value corresponding to only a specific engine operating state, the abnormal combustion can be accurately determined only in the specific engine operating state. Opportunities for making this determination with high accuracy are limited.

  Therefore, in this embodiment, the predetermined pressure Pth used for the determination of abnormal combustion is variably set according to the engine operating state at that time, so that the determination of abnormal combustion can be performed accurately regardless of the engine operating state. ing.

  If the predetermined pressure Pth used for the determination is set in step S1, the process proceeds to step S2, and it is determined whether or not the crankcase internal pressure Pcrnk is equal to or higher than the predetermined pressure Pth. Here, when it is determined that the crankcase internal pressure Pcrnk is not equal to or higher than the predetermined pressure Pth (step S2: “NO”), it is determined that no abnormal combustion has occurred, and this series of processes is temporarily terminated.

  On the other hand, when it is determined in step S2 that the crankcase internal pressure Pcrnk is equal to or higher than the predetermined pressure Pth (step S2: “YES”), the process proceeds to step S3, where the crankcase internal pressure Pcrnk is equal to or higher than the predetermined pressure Pth. It is determined whether or not the state duration time Δt is shorter than a predetermined time Δtth (for example, 1 second).

  In the internal combustion engine 1, for example, when the PCV valve 42 is in a closed state and the recirculation passage 41 that connects the crankcase 13 and the intake passage 2 is closed, the blow-by gas in the crankcase 13 is sucked. The crankcase internal pressure Pcrnk may increase due to the inability to return to the passage 2. Therefore, if it is determined that the abnormal combustion has occurred only when the crankcase internal pressure Pcrnk detected by the crankcase internal pressure sensor 51 becomes equal to or higher than the predetermined pressure Pth, abnormal combustion actually occurs. There is a possibility that it is erroneously determined that abnormal combustion has occurred even though it is not.

  When abnormal combustion such as pre-ignition occurs in the combustion chamber 16, the accompanying increase in pressure in the crankcase 13 is an instantaneous phenomenon, whereas the crankcase 13 resulting from the blockage of the recirculation passage 41. The increase in pressure is a phenomenon that continues for a long time. Therefore, in the present embodiment, the predetermined time Δtth is set in advance through experiments or the like by paying attention to the fact that the period during which the crankcase internal pressure Pcrnk excessively increases differs between abnormal combustion and other times. ing.

  If it is determined in step S3 that the continuation time Δt in which the crankcase internal pressure Pcrnk is equal to or higher than the predetermined pressure Pth is not less than the predetermined time Δtth (step S3: “NO”), the cause of the high crankcase internal pressure Pcrnk is abnormal. This series of processes is once terminated, assuming that it is not due to combustion.

  On the other hand, when it is determined in step S3 that the duration Δt of the crankcase internal pressure Pcrnk being equal to or higher than the predetermined pressure Pth is shorter than the predetermined time Δtth (step S3: “YES”), it is determined that abnormal combustion has occurred. Then, this series of processes is temporarily ended.

  By the way, the normal-time pressure changes with a change with time of the internal combustion engine 1 even in the same engine operating state. Therefore, if the predetermined pressure Pth used for abnormality determination is a fixed value with respect to a predetermined engine operating state (in this embodiment, the engine rotational speed NE and the engine load KL), the internal pressure of the internal combustion engine 1 changes with time, etc. If the change occurs, the presence or absence of abnormal combustion in the combustion chamber 16 may not be accurately determined.

Therefore, in this embodiment, in order to solve such inconvenience, the predetermined pressure Pth is learned and updated for each engine operating state.
Next, a process for learning and updating a predetermined pressure (hereinafter, a predetermined pressure learning process) will be described with reference to FIG. FIG. 3 is a flowchart showing the procedure of the predetermined pressure learning process. Further, this series of processing is repeatedly executed at predetermined intervals during engine operation.

  As shown in FIG. 3, in this series of processing, first, in step S11, a predetermined pressure Pth that is a target of learning update is set based on the engine speed NE and the engine load KL. Then, the process proceeds to step S12, and the average value Pave of the crankcase internal pressure Pcrnk at that time is set to the learning value α. Here, the average value Pave of the crankcase internal pressure is an arithmetic average value of a plurality of crankcase internal pressures Pcrnk detected by the crankcase internal pressure sensor 51 in the engine operating state (engine speed NE, engine load KL) at that time. .

  After the learning value α is set in this way, the process proceeds to step S13, where a value obtained by adding the margin x to the learning value α is set as a new predetermined pressure Pth, and this series of processes is temporarily ended. Here, the reason why the margin x is added to the learning value α is to make the predetermined pressure Pth larger than the upper limit value of the normal pressure in the engine operating state at that time. The margin x is set in advance through experiments or the like.

FIG. 4 shows an example of the transition of the crankcase internal pressure Pcrnk.
As shown in FIG. 4, the normal pressure does not exceed the predetermined pressure Pth. Here, when abnormal combustion such as pre-ignition occurs at time t1, the crankcase internal pressure Pcrnk instantaneously increases and exceeds the predetermined pressure Pth (pressure at the time of abnormality). However, the increase in the crankcase internal pressure Pcrnk due to abnormal combustion is completed within a predetermined time Δtth.

Next, the operation of this embodiment will be described.
When abnormal combustion such as pre-ignition occurs in the combustion chamber 16, the pressure in the cylinder 10 increases, and the crankcase internal pressure Pcrnk increases accordingly. In the present embodiment, the crankcase internal pressure sensor 51 detects the crankcase internal pressure Pcrnk, and based on the detection result, the presence or absence of occurrence of abnormal combustion in the combustion chamber 16 is determined. For this reason, the presence or absence of the occurrence of the abnormal combustion can be determined by only one crankcase internal pressure sensor 51.

According to the control apparatus for an internal combustion engine according to the present embodiment described above, the following effects can be obtained.
(1) A crankcase internal pressure sensor 51 for detecting the crankcase internal pressure Pcrnk is provided, and whether or not abnormal combustion has occurred in the combustion chamber 16 is determined based on the detection result of the crankcase internal pressure sensor 51 through the electronic control unit 50. Yes. Specifically, the crankcase internal pressure Pcrnk detected by the crankcase internal pressure sensor 51 is equal to or higher than a predetermined pressure Pth that is larger than the upper limit value of the pressure generated when combustion is normally performed in the engine operating state at that time. When this happens, it is determined that the abnormal combustion has occurred. According to such a configuration, whether or not abnormal combustion has occurred in the combustion chamber 16 can be determined with a simple configuration without depending on the in-cylinder pressure sensor.

  (2) The predetermined pressure Pth is variably set in accordance with the engine operating state at that time, specifically, the engine speed NE and the engine load KL. According to such a configuration, it is possible to accurately increase the execution opportunity for the determination of abnormal combustion.

  (3) The predetermined pressure Pth is learned and updated for each engine operating state. According to such a configuration, it is possible to accurately determine whether or not abnormal combustion has occurred in the combustion chamber 16.

  (4) When the crankcase internal pressure Pcrnk detected by the crankcase internal pressure sensor 51 becomes equal to or higher than the predetermined pressure Pth for a predetermined time Δtth or higher, it is not determined that the abnormal combustion has occurred. According to such a configuration, it is possible to accurately suppress erroneous determination that abnormal combustion has occurred even though abnormal combustion has not actually occurred.

  (5) The internal combustion engine 1 of the present embodiment is not provided with an in-cylinder pressure sensor. According to such a configuration, since it is possible to determine whether or not abnormal combustion has occurred in the combustion chamber 16 without providing an in-cylinder pressure sensor in each cylinder 10, the number of parts can be reduced. Therefore, the configuration of the internal combustion engine 1 and the electronic control device 50 can be simplified.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6.
FIG. 5 shows a schematic configuration of the internal combustion engine 1 of this embodiment and an electronic control device 50 that is a control device thereof.

  As shown in FIG. 5, in this embodiment, in addition to the various sensors exemplified in the first embodiment, an in-cylinder pressure sensor 52 that detects a pressure in each cylinder 10 (hereinafter, in-cylinder pressure Pcyl) is provided in the cylinder 10. It is provided for each. Since the other configuration is the same as the configuration of the first embodiment, the same description will be omitted by attaching the same reference numeral to the same configuration.

  The in-cylinder pressure sensor 52 directly detects the pressure in the combustion chamber 16, whereas the crankcase internal pressure sensor 51 detects the pressure in the crankcase 13 that changes according to the pressure in the combustion chamber 16. It is. Therefore, even if abnormal combustion occurs in the combustion chamber 16, if the degree is small, the occurrence of the abnormal combustion can be accurately determined from the detection result of the in-cylinder pressure sensor 52, but the crankcase internal pressure sensor 51 The occurrence of abnormal combustion may not be determined from the detection result.

  Therefore, in the present embodiment, the presence or absence of occurrence of abnormal combustion in the combustion chamber 16 is determined based on the detection result of the in-cylinder pressure sensor 52, while the crankcase internal pressure sensor 51 is in an abnormal state. Whether or not the abnormal combustion has occurred is determined based on the detection result.

  Next, an abnormal combustion detection process using the in-cylinder pressure sensor 52 and the crankcase internal pressure sensor 51 will be described with reference to FIG. FIG. 6 is a flowchart showing the procedure of the abnormal combustion determination process. This series of processes is repeatedly executed at predetermined intervals by the electronic control unit 50 during engine operation.

  As shown in FIG. 6, in this series of processes, it is first determined in step S <b> 20 whether or not an abnormality has occurred in the in-cylinder pressure sensor 52. Here, based on a signal output from the in-cylinder pressure sensor 52 provided in each cylinder 10 to the electronic control unit 50, it is determined whether or not an abnormality has occurred in at least one in-cylinder pressure sensor 52.

  If it is determined in step S20 that an abnormality has occurred in the in-cylinder pressure sensor 52 (step S20: “NO”), the crankcase internal pressure sensor 51 is replaced with the abnormal combustion determination process using the in-cylinder pressure sensor 52. Next, in order to perform the abnormal combustion determination process used, the process proceeds to step S1 of the flowchart shown in FIG. The subsequent steps are the same as those in the first embodiment.

  On the other hand, when it is determined in step S20 that no abnormality has occurred in the in-cylinder pressure sensor 52 (step S20: “YES”), the process proceeds to step S21, and the process is performed based on the engine speed NE and the engine load KL. A predetermined pressure Pth1 used for determination is set.

  The predetermined pressure Pth1 is set to a value larger than the upper limit value of the pressure (normal in-cylinder pressure) generated when the in-cylinder pressure Pcyl is normally burned in the engine operating state at that time. The value is variably set according to the rotational speed NE and the engine load KL. Specifically, the normal cylinder pressure increases as the engine speed NE increases and as the engine load KL increases. For this reason, the higher the engine speed NE and the higher the engine load KL, the larger the predetermined pressure Pth1 is set.

  The reason why the predetermined pressure Pth1 is variably set according to the engine operating state is the same as the reason why the predetermined pressure Pth is variably set according to the engine operating state as described in the first embodiment.

  When the predetermined pressure Pth1 used for determination is set in step S21, the process proceeds to step S22, and it is determined whether or not the in-cylinder pressure Pcyl is equal to or higher than the predetermined pressure Pth1. Here, when it is determined that the in-cylinder pressure Pcyl is not equal to or higher than the predetermined pressure Pth1 (step S22: “NO”), this series of processes is temporarily terminated, assuming that abnormal combustion has not occurred.

  On the other hand, if it is determined in step S22 that the in-cylinder pressure Pcyl is equal to or higher than the predetermined pressure Pth1 (step S22: “YES”), it is determined that abnormal combustion has occurred, and this series of processes is temporarily terminated.

  The in-cylinder pressure at normal time varies with a change in the internal combustion engine 1 with time even in the same engine operating state. Therefore, if the predetermined pressure Pth1 used for abnormality determination is set to a fixed value with respect to a predetermined engine operating state (in this embodiment, the engine speed NE and the engine load KL), the internal combustion engine 1 changes with time, etc. When the internal pressure changes, it may not be possible to accurately determine whether or not abnormal combustion has occurred in the combustion chamber 16.

  Therefore, in this embodiment, in order to solve such inconveniences, the predetermined pressure Pth1 is learned and updated for each engine operating state in the same manner as the predetermined pressure learning process in the first embodiment.

Next, the operation of this embodiment will be described.
When abnormality occurs in the in-cylinder pressure sensor 52, the presence or absence of occurrence of abnormal combustion in the combustion chamber 16 is determined based on the detection result of the crankcase internal pressure sensor 51.

  Further, when there is no abnormality in the in-cylinder pressure sensor 52, the abnormal combustion is not determined based on the detection result of the crankcase internal pressure sensor 51. Therefore, compared to a control configuration for determining whether or not abnormal combustion has occurred based on the detection result of the in-cylinder pressure sensor 52, and for determining whether or not abnormal combustion has occurred based on the detection result of the crankcase internal pressure sensor 51 in parallel therewith. Thus, an increase in calculation load in the electronic control unit 50 is suppressed.

According to the control apparatus for an internal combustion engine according to the present embodiment described above, the following effects (6) and (7) are newly obtained in addition to the effects (1) to (4) of the first embodiment. Be able to.
(6) An in-cylinder pressure sensor 52 that detects the in-cylinder pressure Pcyl is provided for each cylinder 10, and based on the detection result of the in-cylinder pressure sensor 52, the presence or absence of occurrence of abnormal combustion in the combustion chamber 16 is determined. According to such a configuration, since the presence or absence of the abnormal combustion is determined based on the detection result of the in-cylinder pressure sensor 52, it is possible to accurately determine the occurrence of the abnormal combustion with a small degree.

  (7) When an abnormality occurs in the in-cylinder pressure sensor 52, the presence or absence of the abnormal combustion is determined based on the detection result of the crankcase internal pressure sensor 51. According to such a configuration, even if an abnormality occurs in the in-cylinder pressure sensor 52, it is possible to determine whether or not the abnormal combustion has occurred. Compared to a control configuration for determining whether or not abnormal combustion has occurred based on the detection result of the in-cylinder pressure sensor 52 and for determining whether or not abnormal combustion has occurred based on the detection result of the crankcase internal pressure sensor 51 in parallel therewith. Thus, an increase in calculation load in the electronic control unit 50 can be suitably suppressed.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIGS.
This embodiment is different from the second embodiment in that the presence or absence of occurrence of the abnormal combustion is separately determined based on the detection result of the crankcase internal pressure sensor 51 and the detection result of the in-cylinder pressure sensor 52.

Hereinafter, the difference from the second embodiment will be mainly described.
In the present embodiment, an abnormality using the following in-cylinder pressure sensor 52 is performed in parallel with the abnormal combustion determination process using the crankcase internal pressure sensor 51 illustrated with reference to FIGS. 2 and 3 in the first embodiment. A combustion determination process is executed.

  Next, with reference to FIG. 7, the procedure of the abnormal combustion determination process using the in-cylinder pressure sensor 52 in the present embodiment will be described. FIG. 7 is a flowchart showing the procedure of the abnormal combustion determination process. This series of processes is repeatedly executed at predetermined intervals by the electronic control unit 50 during engine operation.

As shown in FIG. 7, a series of processing from step 31 to step S33 is the same as a series of processing from step S21 to step S23 in FIG.
As described above, the in-cylinder pressure sensor 52 directly detects the pressure in the combustion chamber 16, whereas the crankcase internal pressure sensor 51 changes in accordance with the pressure in the combustion chamber 16. It detects the internal pressure. Therefore, even if abnormal combustion occurs in the combustion chamber 16, if the degree is small, the occurrence of the abnormal combustion can be accurately determined from the detection result of the in-cylinder pressure sensor 52, but the crankcase internal pressure sensor 51 The occurrence of abnormal combustion may not be determined from the detection result. From this, when it is determined from the detection result of the crankcase internal pressure sensor 51 that the abnormal combustion has occurred, it can be said that the degree of the abnormal combustion is large. On the other hand, when it is determined from the detection result of the crankcase internal pressure sensor 51 that the abnormal combustion has not occurred, and when it is determined from the detection result of the in-cylinder pressure sensor 52 that the abnormal combustion has occurred, the abnormal combustion is performed. It can be said that the degree of is small.

  Therefore, in this embodiment, when it is determined that the abnormal combustion has occurred from the detection result of the crankcase internal pressure sensor 51, and from the detection result of the crankcase internal pressure sensor 51, it is determined that the abnormal combustion has not occurred. On the other hand, the execution mode of the subsequent fail-safe process of the internal combustion engine is made different when it is determined from the detection result of the in-cylinder pressure sensor 52 that the abnormal combustion has occurred.

  Next, with reference to FIG. 8, the fail safe process of the internal combustion engine 1 will be described. FIG. 8 is a flowchart showing the procedure of the fail-safe process. This series of processes is executed every time both the abnormal combustion determination process using the crankcase internal pressure sensor 51 and the abnormal combustion determination process using the in-cylinder pressure sensor 52 are completed.

  As shown in FIG. 8, in this series of processes, first, in step S41, it is determined whether or not it is determined that abnormal combustion has occurred in the determination process using the crankcase internal pressure sensor 51. Here, when it is determined that the abnormal combustion has occurred (step S41: “NO”), the process proceeds to step S43, where the first fail-safe process is executed, and this series of operations is performed. The process is temporarily terminated. In the first fail-safe process, the occurrence of abnormal combustion is suppressed by using a conventionally well-known method of correcting the intake air amount and the fuel injection amount to decrease and correcting the ignition timing retarded.

  On the other hand, if it is not determined in step S41 that the abnormal combustion has occurred (step S41: “YES”), the process proceeds to step S42, where abnormal combustion is performed in the determination process using the in-cylinder pressure sensor 52. It is determined whether or not it has been determined that occurrence has occurred. Here, when it is determined that the abnormal combustion has occurred (step S42: “NO”), the process proceeds to step S44, where the second fail-safe process is executed, and this series of operations is performed. The process is temporarily terminated. It can be said that when the second fail-safe process is executed, the degree of abnormal combustion is lower than when the first fail-safe process is executed. Therefore, in the second fail-safe process, the correction amount of the control amount of the internal combustion engine 1 is set smaller than that in the first fail-safe process. Specifically, in the second fail-safe process, the reduction correction amount of the intake air amount and the fuel injection amount is made smaller and the retard correction amount of the ignition timing is made smaller than in the first fail-safe process.

  Further, when it is not determined in step S42 that the abnormal combustion has occurred (step S42: “YES”), even a small degree of abnormal combustion has not occurred, and it is necessary to perform fail-safe processing. As a result, the series of processes is temporarily terminated.

According to the control apparatus for an internal combustion engine according to the present embodiment described above, the following effect (8) can be newly obtained in addition to the effects (1) to (4) of the first embodiment. Become.
(8) Based on the detection result of the crankcase internal pressure sensor 51 and the detection result of the in-cylinder pressure sensor 52, the presence or absence of occurrence of the abnormal combustion is separately determined. On the other hand, when it is determined from the detection result of the crankcase internal pressure sensor 51 that the abnormal combustion has occurred, and from the detection result of the crankcase internal pressure sensor 51, it is determined that the abnormal combustion has not occurred. Depending on the detection result of the sensor 52, it is determined that the abnormal combustion has occurred, and the execution mode of the subsequent fail-safe process of the internal combustion engine is made different. According to such a configuration, the execution mode of subsequent fail-safe processing of the internal combustion engine 1 varies depending on the degree of abnormal combustion. Therefore, an appropriate fail-safe process can be performed according to the situation of the internal combustion engine 1.

  Note that the control device for an internal combustion engine according to the present invention is not limited to the configuration exemplified in the above embodiment, and can be implemented as, for example, the following forms appropriately modified. In each of the above embodiments, the internal combustion engine 1 including the supercharger 30 has been illustrated, but the internal combustion engine according to the present invention is not limited to the one equipped with the supercharger. That is, a naturally aspirated internal combustion engine may be used.

  In the third embodiment, when it is determined from the detection result of the crankcase internal pressure sensor 51 that the abnormal combustion has occurred, and from the detection result of the crankcase internal pressure sensor 51, the abnormal combustion has not occurred. On the other hand, the execution mode of the subsequent fail-safe process of the internal combustion engine is made different from the case where it is determined from the detection result of the in-cylinder pressure sensor 52 that the abnormal combustion has occurred. However, the present invention is not limited to this, and the execution mode of fail-safe processing performed in both cases may be the same.

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Intake passage, 3 ... Exhaust passage, 10 ... Cylinder, 11 ... Cylinder head, 12 ... Cylinder block, 13 ... Crankcase, 14 ... Piston, 15 ... Crankshaft, 16 ... Combustion chamber, 17 ... Fuel injection valve, 18 ... spark plug, 21 ... intercooler, 22 ... throttle body, 23 ... throttle valve, 24 ... throttle motor, 30 ... supercharger, 31 ... compressor housing, 32 ... impeller, 40 ... blow-by gas recirculation device , 41... Reflux passage, 42... PCV valve, 50... Electronic control device, 51.

Claims (9)

In a control device for controlling an internal combustion engine,
A crankcase internal pressure sensor for detecting the pressure in the crankcase of the internal combustion engine;
A control apparatus for an internal combustion engine, wherein the presence or absence of occurrence of abnormal combustion in a combustion chamber is determined based on a detection result of the crankcase internal pressure sensor. The control apparatus for an internal combustion engine according to claim 1,
When the pressure in the crankcase detected by the crankcase internal pressure sensor is equal to or higher than a predetermined pressure greater than the upper limit value of the pressure generated when combustion is normally performed in the engine operating state at that time It is determined that the abnormal combustion has occurred. A control device for an internal combustion engine, characterized in that: The control apparatus for an internal combustion engine according to claim 2,
The control apparatus for an internal combustion engine, wherein the predetermined pressure is variably set according to an engine operating state at that time. The control apparatus for an internal combustion engine according to claim 3,
The control apparatus for an internal combustion engine, wherein the predetermined pressure is learned and updated for each engine operating state. The control device for an internal combustion engine according to any one of claims 2 to 4,
The control apparatus for an internal combustion engine, wherein when the pressure in the crankcase detected by the crankcase internal pressure sensor has exceeded the predetermined pressure for a predetermined time or more, it is not determined that the abnormal combustion has occurred. In the control device for an internal combustion engine according to any one of claims 1 to 5,
An in-cylinder pressure sensor for detecting the pressure in the cylinder is further provided for each cylinder,
A control apparatus for an internal combustion engine, wherein the presence or absence of occurrence of the abnormal combustion is determined based on a detection result of the in-cylinder pressure sensor. The control apparatus for an internal combustion engine according to claim 6,
A control device for an internal combustion engine, wherein when abnormality occurs in the in-cylinder pressure sensor, the presence or absence of occurrence of the abnormal combustion is determined based on a detection result of the crankcase internal pressure sensor. The control apparatus for an internal combustion engine according to claim 6,
Based on the detection result of the crankcase internal pressure sensor and the detection result of the in-cylinder pressure sensor, the presence or absence of occurrence of the abnormal combustion is determined separately,
While it is determined from the detection result of the crankcase internal pressure sensor that the abnormal combustion has occurred, and from the detection result of the crankcase internal pressure sensor, it has been determined that the abnormal combustion has not occurred, while the in-cylinder pressure sensor A control apparatus for an internal combustion engine, wherein the execution mode of subsequent fail-safe processing of the internal combustion engine is made different from the case where it is determined from the detection result that abnormal combustion has occurred. In the control device for an internal combustion engine according to any one of claims 1 to 8,
The internal combustion engine is provided with a supercharger.