Control device of internal combustion engine

Abstract

To suppress the erroneous detection of the abnormal combustion of an internal combustion engine.SOLUTION: A control device 60 of an internal combustion engine of the present invention has: an abnormal combustion determination part 61 for determining the abnormal combustion of an engine 10 on the basis of a signal from a knock sensor 21; a control part 62 for performing control for avoiding the abnormal combustion of the engine 10 when the abnormal combustion of the engine 10 is determined by the abnormal combustion determination part 61; and a property determination part 63 for determining a property of fuel which is supplied to the engine 10. Since a setting part 64 changes and sets a detection region of the abnormal combustion according to the property of the fuel which is determined by the property determination part 63, the erroneous detection of the abnormal combustion of the engine 10 can be suppressed on the basis of a noise signal from the knock sensor 21.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known a control device for an internal combustion engine that performs control so as to avoid abnormal combustion when abnormal combustion in the internal combustion engine is detected. Patent Document 1 discloses an engine control device that, when the engine operating condition is in a knock detectable region, determines whether or not knocking is occurring for a predetermined time from the output signal of a knock sensor, and, if knocking is occurring, changes the ignition timing map in the knock detectable region. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 1-277661 [Patent Document 2] JP 2002-349319 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the engine control device of Patent Document 1, the region in which knocking is detected as abnormal combustion is always fixed. On the other hand, considering that the fuel supplied to the engine may be a low-octane fuel or poor quality fuel, it is preferable to expand the region in which abnormal combustion is detected in advance. However, if the region in which abnormal combustion is detected is expanded, although abnormal combustion can be detected when low-octane fuel or poor quality fuel is supplied, there is a risk that the frequency of erroneous detection of abnormal combustion based on a noise signal from the knock sensor increases. If abnormal combustion is erroneously detected, control is performed to avoid abnormal combustion, so that the output of the internal combustion engine is suppressed, and rapid acceleration is hindered even when acceleration is requested.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to suppress erroneous detection of abnormal combustion in an internal combustion engine. [Means for solving the problem]

[0006] The present invention is a control device for an internal combustion engine having abnormal combustion judgment means for judging abnormal combustion in an internal combustion engine based on a signal from a knock sensor in an abnormal combustion detection region, control means for performing control to avoid abnormal combustion in the internal combustion engine when abnormal combustion in the internal combustion engine is judged by the abnormal combustion judgment means, and property judgment means for judging the properties of fuel supplied to the internal combustion engine, and is characterized in having a setting means for changing and setting the abnormal combustion detection region in accordance with the fuel properties judged by the property judgment means. Effect of the Invention

[0007] According to the present invention, it is possible to suppress erroneous detection of abnormal combustion in an internal combustion engine. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a schematic configuration of a vehicle equipped with a control device for an internal combustion engine. [Diagram 2] FIG. 2 is a diagram illustrating an example of a functional configuration of a control device. [Diagram 3] FIG. 2 is a diagram showing an example of a pre-ignition detection region. [Figure 4] 5 is a flowchart showing an example of a process performed by a control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The embodiment according to the present invention is a control device 60 for an internal combustion engine, which includes an abnormal combustion determination unit 61 that determines abnormal combustion in the engine 10 based on a signal from the knock sensor 21 in a detection region of abnormal combustion, a control unit 62 that performs control to avoid abnormal combustion in the engine 10 when abnormal combustion is determined by the abnormal combustion determination unit 61, and a property determination unit 63 that determines the property of fuel supplied to the engine 10. The control device 60 includes a setting unit 64 that changes and sets the detection region of abnormal combustion in accordance with the property of the fuel determined by the property determination unit 63, thereby making it possible to suppress erroneous detection of abnormal combustion in the engine 10. EXAMPLES

[0010] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a diagram showing a schematic configuration of a vehicle 1 equipped with a control device for an internal combustion engine (hereinafter, referred to as the control device) according to this embodiment. Note that Fig. 1 is simplified for the sake of convenience in explaining this embodiment, and components that are normally equipped in a vehicle are assumed to be equipped even if they are not shown in the figure. A vehicle 1 according to this embodiment includes an engine 10 as an internal combustion engine, an intake passage 30, an exhaust passage 40, a fuel tank 50, a control device 60, and the like.

[0011] The engine 10 performs a series of strokes consisting of an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. The engine 10 has a piston 12 accommodated in a cylinder 11 so as to be capable of reciprocating motion, a spark plug 13 disposed in a combustion chamber 14, an intake valve 16 located between the combustion chamber 14 and an intake port 15, an exhaust valve 18 located between the combustion chamber 14 and an exhaust port 17, a crankshaft 20 to which the piston 12 is rotatably connected via a connecting rod 19, and the like.

[0012] During the intake stroke, the piston 12 descends from top dead center to bottom dead center, the intake valve 16 opens, and the exhaust valve 18 closes. As the piston 12 descends, the intake air and fuel mixture flows from the intake passage 30 into the combustion chamber 14. In the compression stroke, the piston 12 moves upward from the bottom dead center to the top dead center, and the intake valve 16 and the exhaust valve 18 close. As the piston 12 moves upward, the air-fuel mixture is compressed. During the combustion stroke, the compressed air-fuel mixture is ignited by the spark plug 13 and combusted, pushing the piston 12 downward, causing it to move from top dead center to bottom dead center. During the exhaust stroke, the piston 12 rises from the bottom dead center to the top dead center, the intake valve 16 closes, and the exhaust valve 18 opens. As the piston 12 rises, exhaust gas generated during the combustion stroke is discharged into the exhaust passage 40.

[0013] As the engine 10 repeats a series of processes, driving force is transmitted from the engine 10 to the drive wheels via the crankshaft 20, causing the vehicle to run. Note that the configuration of the engine 10 is not particularly limited, and various known engines can be applied.

[0014] The engine 10 also has a knock sensor 21, a crank angle sensor 22, and an engine speed sensor 23. The knock sensor 21 detects the frequency of vibration of the engine 10 and transmits the detected frequency information as a signal to the control device 60. If abnormal combustion such as knocking or pre-ignition occurs during the compression stroke or combustion stroke of the engine 10, a frequency different from the frequency during normal combustion is detected. The control device 60 determines whether or not abnormal combustion is occurring in the engine 10 based on the signal transmitted from the knock sensor 21.

[0015] The crank angle sensor 22 detects the crank angle (the rotation angle of the crankshaft 20) and transmits information about the detected crank angle to the control device 60. The control device 60 controls the ignition timing of the spark plug 13 based on the information about the crank angle detected by the crank angle sensor 22.

[0016] The engine speed sensor 23 detects the engine speed, specifically, information on the number of revolutions per unit time of the crankshaft 20, and transmits the detected engine speed information to the control device 60. The control device 60 uses the engine speed information detected by the engine speed sensor 23 when calculating the engine load factor.

[0017] The intake passage 30 is a passage that guides intake air taken in from outside the vehicle 1 to the combustion chamber 14 via the intake port 15. The intake passage 30 is formed, for example, by an intake pipe. In the intake passage 30, a throttle valve 31 and a fuel injector 32 are arranged in this order from the upstream side.

[0018] The throttle valve 31 adjusts the amount of intake air by opening and closing. The throttle valve 31 adjusts the amount of intake air based on the control of the control device 60. Fuel injector 32 injects fuel pumped from fuel tank 50 into intake passage 30. Fuel injector 32 adjusts the amount of fuel injected under the control of control device 60. Note that fuel injector 32 is not limited to injecting fuel into intake passage 30, and may be configured to inject fuel into intake port 15 or combustion chamber 14.

[0019] Further, an air flow sensor 33 and a throttle opening sensor 34 are disposed in the intake passage 30 (around the intake passage 30). The airflow sensor 33 detects information on the amount of intake air, and transmits the detected information on the amount of intake air to the control device 60. The control device 60 uses the information on the amount of intake air detected by the airflow sensor 33 when calculating the engine load factor. The throttle opening sensor 34 detects information on the throttle opening of the throttle valve 31, and transmits the detected throttle opening information to the control device 60. The control device 60 calculates the amount of fuel to be injected from the fuel injector 32 based on the throttle opening information detected by the throttle opening sensor 34.

[0020] The exhaust passage 40 is a passage through which exhaust gas combusted in the combustion chamber 14 is exhausted to the outside of the vehicle 1 via the exhaust port 17. The exhaust passage 40 is formed of, for example, an exhaust pipe. A catalytic converter 41 is disposed in the exhaust passage 40. The catalytic converter 41 purifies the exhaust gas by oxidizing and reducing toxic components contained in the exhaust gas.

[0021] The fuel tank 50 stores gasoline fuel to be supplied to the fuel injector 32. The gasoline fuel stored in the fuel tank 50 is sucked up by a fuel pump and pumped to the fuel injector 32. Note that fuel with different properties may be supplied to the fuel tank 50 depending on the person supplying the fuel. The vehicle 1 is equipped with an accelerator opening sensor 51. The accelerator opening sensor 51 detects the amount of accelerator pedal operation by the driver, and transmits information on the detected amount of operation to the control device 60.

[0022] The control device 60 controls the entire vehicle 1. For example, an ECU (Electronic Control Unit) can be used as the control device 60. The control device 60 has a CPU, a ROM, a RAM, etc. as a hardware configuration. The ROM stores programs and predetermined information for controlling the vehicle 1, the engine 10, etc. The RAM is a work memory that temporarily stores programs and data. The CPU reads out the programs stored in the ROM, expands them in the RAM, and executes them to control the vehicle 1, the engine 10, etc.

[0023] FIG. 2 is a diagram illustrating an example of a functional configuration of the control device 60. As shown in FIG. The control device 60 has an abnormal combustion determination unit 61 , a control unit 62 , a property determination unit 63 , and a setting unit 64 . The abnormal combustion determination unit 61 detects abnormal combustion in the engine 10 based on a signal from the knock sensor 21 in the abnormal combustion detection range. Here, abnormal combustion includes knocking, which is a phenomenon in which the combustion speed increases after the ignition of the spark plug 13, and pre-ignition, which is a phenomenon in which combustion starts before the ignition of the spark plug 13. Abnormal combustion such as knocking and pre-ignition causes the engine 10 to rotate poorly, which can cause damage to the engine 10. Note that abnormal combustion is likely to occur with gasoline fuel that has a low octane number or is of poor quality, and is unlikely to occur with gasoline fuel that has a high octane number.

[0024] Specifically, the abnormal combustion determination unit 61 determines that abnormal combustion has occurred when the current state of the engine 10 is in the detection range of abnormal combustion and the frequency detected by the knock sensor 21 is greater than a threshold value. Here, the current state of the engine 10 being in the detection range of abnormal combustion means that the current engine load factor is within the detection range of abnormal combustion that is changed and set according to the properties of the fuel. The processing by the abnormal combustion determination unit 61 will be described later.

[0025] The control unit 62 controls the entire vehicle 1. The control unit 62 controls the throttle valve 31 so that the target throttle opening is achieved based on the accelerator opening detected by the accelerator opening sensor 51. The control unit 62 also controls the fuel injector 32 so as to inject fuel at a fuel injection amount obtained by correcting a reference fuel injection amount calculated according to the engine speed detected by the engine speed sensor 23 and the intake amount detected by the airflow sensor 33 based on information from various sensors. Furthermore, the control unit 62 performs control to avoid abnormal combustion when abnormal combustion in the engine 10 is detected by the abnormal combustion determination unit 61. Specifically, the control unit 62 retards the ignition timing of the spark plug 13 to avoid abnormal combustion.

[0026] The property determination unit 63 determines the property of the fuel supplied to the engine 10. Here, the property of the fuel is the octane number of gasoline fuel. The method by which the property determination unit 63 determines the property of the fuel is not limited, and a known method can be used. For example, as shown in Patent Document 2, the property determination unit 63 may determine the property of the fuel by comparing the cylinder inflow fuel response during acceleration with a simulation response using a reference model constructed in advance. In addition, the property determination unit 63 may determine the property of the fuel from the deviation of the air-fuel ratio to the lean side during acceleration based on the air-fuel ratio detected by an air-fuel ratio sensor provided in the vehicle 1. In addition, the property determination unit 63 may determine the property of the fuel based on the specific gravity difference or vapor pressure difference of the fuel detected by a property sensor provided in the vehicle 1.

[0027] The setting unit 64 sets the abnormal combustion detection region in accordance with the fuel properties determined by the property determination unit 63. Specifically, the setting unit 64 sets the abnormal combustion detection region so as to expand as the octane number of the gasoline fuel decreases. In this embodiment, the setting unit 64 sets the pre-ignition detection region so as to expand as the octane number of the gasoline fuel decreases.

[0028] FIG. 3 is a diagram showing an example of a pre-ignition detection region which is a detection region for abnormal fuel. FIG. 3(a) is a diagram showing an example of the pre-ignition detection region A in the normal mode, that is, the pre-ignition detection region A when the octane number of the fuel is not low (when it is high). FIG. 3(b) is a diagram showing an example of the pre-ignition detection region B in the expanded mode, that is, the pre-ignition detection region B when the octane number of the fuel is low. In FIG. 3(a) and FIG. 3(b), the horizontal axis is the engine speed, the vertical axis is the engine load factor, and the shaded portion is the pre-ignition detection region. When the engine state is within the pre-ignition detection region, pre-ignition is determined based on the signal from the knock sensor 21. On the other hand, when the engine state is outside the pre-ignition detection region, pre-ignition is not determined even if the same signal is output from the knock sensor 21.

[0029] As shown in FIG. 3(a), the pre-ignition detection region A in normal mode is equal to or greater than the engine load factor a. The engine load factor a is the lower limit of the pre-ignition detection region A and is a constant value. The pre-ignition detection region A is determined to be smaller than the pre-ignition detection region B in the expanded mode shown in FIG. 3(b). The engine load factor a is higher than the engine load factor b of the pre-ignition detection region B in the expanded mode shown in FIG. 3(b). The reason why the engine load factor a, which is the lower limit of the pre-ignition detection region A, is high in this way is because pre-ignition does not occur when the engine load factor is low with fuel that has a high octane number.

[0030] As shown in FIG. 3(b), the pre-ignition detection region B in the expanded mode is equal to or greater than the engine load factor b. The engine load factor b is the lower limit of the pre-ignition detection region B and is determined according to the octane rating. The pre-ignition detection region B is determined to be expanded compared to the pre-ignition detection region A in the normal mode shown in FIG. 3(a). The engine load factor b is lower than the engine load factor a of the pre-ignition detection region A in the normal mode shown in FIG. 3(a). The reason why the engine load factor b, which is the lower limit of the pre-ignition detection region B, is low in this manner is that with fuel with a low octane rating, pre-ignition may occur even when the engine load factor is low.

[0031] Here, a case has been described in which the lower limit value of the pre-ignition detection region B in the expanded mode is the engine load rate b, but the setting unit 64 sets the pre-ignition detection region to be continuously expanded by setting the lower limit value lower as the octane number becomes lower. However, the setting unit 64 may also set the pre-ignition detection region to be expanded in stages by setting the lower limit value of the pre-ignition detection region to be gradually lower as the octane number becomes lower.

[0032] Next, an example of processing by the control device 60 will be described with reference to the flowchart of Fig. 4. The flowchart of Fig. 4 is realized, for example, by the ECU, which is the control device 60, executing a program. The flowchart of Fig. 4 is started when the engine 10 is started. Below, a case where the abnormal combustion is pre-ignition will be described.

[0033] In S10, the property determining unit 63 determines the property of the fuel supplied to the engine 10. Specifically, the property determining unit 63 determines the octane number of the gasoline fuel. As described above, the fuel property can be determined based on the cylinder inflow fuel response during acceleration, based on the deviation of the air-fuel ratio to the lean side during acceleration, or by using a property sensor.

[0034] In S11, the property determination unit 63 determines whether or not the fuel is prone to pre-ignition, which is abnormal combustion. Specifically, the property determination unit 63 determines that the fuel is prone to pre-ignition if the octane number is equal to or lower than a predetermined value. If the fuel is not prone to pre-ignition, the process proceeds to S12, and if the fuel is prone to pre-ignition, the process proceeds to S13.

[0035] In S12, the setting unit 64 sets the abnormal combustion detection region to the detection region for the normal mode. Specifically, the setting unit 64 sets the pre-ignition detection region for the normal mode. Therefore, the pre-ignition detection region A for the normal mode, whose lower limit value is the engine load factor a, is set as shown in FIG. 3(a). Information on the pre-ignition detection region A is stored in advance in the control device 60.

[0036] In S13, the setting unit 64 sets the abnormal combustion detection region to a detection region corresponding to the fuel properties. Specifically, the setting unit 64 sets the pre-ignition detection region in the expansion mode corresponding to the octane number. Therefore, the pre-ignition detection region B in the expansion mode, whose lower limit value is the engine load factor b, is set as shown in FIG. 3(b). The setting unit 64 changes and sets the pre-ignition detection region so as to be continuously expanded by setting the lower limit value lower as the octane number decreases.

[0037] In S14, the abnormal combustion determination unit 61 determines whether or not abnormal combustion is occurring in the engine 10 based on the signal from the knock sensor 21 in the abnormal combustion detection region. Specifically, the abnormal combustion determination unit 61 determines that pre-ignition is occurring when the current state of the engine 10 is within the pre-ignition detection region set in S12 or S13 and the frequency detected by the knock sensor 21 is greater than the threshold value. On the other hand, if the frequency detected by the knock sensor 21 is equal to or less than the threshold value, or if the frequency detected by the knock sensor 21 is greater than the threshold value but the current state of the engine 10 is outside the pre-ignition detection region set in S12 or S13, it determines that pre-ignition is not occurring.

[0038] Here, whether or not the current state of the engine 10 is within the pre-ignition detection region can be determined based on the current engine load factor. The engine load factor is the ratio of the current intake air amount to the maximum intake air amount according to the engine speed. The control device 60 stores maximum value data indicating the maximum intake air amount according to the engine speed in advance. Therefore, the abnormal combustion determination unit 61 obtains information on the current engine speed from the engine speed sensor 23 and obtains information on the current intake air volume from the air flow sensor 33. The abnormal combustion determination unit 61 obtains information on the maximum intake air volume corresponding to the current engine speed from the maximum value data. Next, the abnormal combustion determination unit 61 obtains information on the current engine load factor by calculating the ratio of the current intake air volume to the maximum intake air volume corresponding to the engine speed based on the obtained information on the maximum intake air volume and the current intake air volume. The abnormal combustion determination unit 61 determines that the current state of the engine 10 is within the pre-ignition detection region when the obtained current engine load factor is equal to or greater than the engine load factor that is the lower limit of the set pre-ignition detection region. On the other hand, the abnormal combustion determination unit 61 determines that the current state of the engine 10 is outside the pre-ignition detection region when the obtained current engine load factor is smaller than the engine load factor that is the lower limit of the set pre-ignition detection region.

[0039] If it is determined that pre-ignition, which is abnormal combustion, has occurred, the process proceeds to S15, and if it is determined that pre-ignition has not occurred, the process of the flowchart in FIG. 4 ends.

[0040] In S15, the control unit 62 performs control so as to avoid abnormal combustion in the engine 10. Specifically, the control unit 62 performs control so as to retard the ignition timing of the spark plug 13 in order to avoid pre-ignition. When the process of S15 ends, the process of the flowchart in Fig. 4 ends. The process of S14 and the process of S15 may be repeated until the engine 10 is stopped. That is, if it is determined in S14 that pre-ignition has occurred, control is performed in S15 to avoid pre-ignition. On the other hand, if it is determined in S14 that pre-ignition has not occurred, the determination of pre-ignition may be continued until pre-ignition occurs in S14.

[0041] In this way, according to this embodiment, the setting unit 64 changes and sets the abnormal combustion detection region depending on the fuel properties. In other words, the abnormal combustion detection region is not fixed, but is set to the normal mode detection region for fuels that are unlikely to cause abnormal combustion, and is set to the expanded mode detection region for fuels that are likely to cause abnormal combustion. Since the detection range in the normal mode is a fuel for which abnormal combustion is unlikely to occur, it is set smaller (reduced) than the detection range in the expanded mode by the amount of the detection range in which abnormal combustion does not occur. Therefore, it is only necessary to determine whether abnormal combustion has occurred when the engine state is within the reduced detection range in the normal mode, and if it is outside the detection range, the signal from the knock sensor 21 is not used to determine abnormal combustion, so that it is possible to suppress erroneous detection of abnormal combustion in the internal combustion engine based on the noise signal from the knock sensor 21.

[0042] On the other hand, the detection range in the expanded mode is set larger (expanded) by the amount of the detection range in which abnormal combustion may occur compared to the detection range in the normal mode, since the fuel is unlikely to cause abnormal combustion. Therefore, abnormal combustion is determined even when the engine state is within the expanded detection range in the expanded mode, so that abnormal combustion in the internal combustion engine can be detected with high accuracy according to the properties of the fuel.

[0043] Furthermore, according to this embodiment, the setting unit 64 sets the detection range for abnormal combustion to be expanded as the octane number of the fuel decreases. When fuel with a lower octane number than normal is supplied to the engine 10, abnormal combustion may occur in the internal combustion engine even if the engine load factor is low. Therefore, by expanding the detection range for abnormal combustion as the octane number of the fuel decreases, erroneous detection of abnormal combustion can be suppressed.

[0044] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and modifications and the like are possible within the scope of the present invention. In the above embodiment, the case where the abnormal combustion is pre-ignition has been described, but in the case where the abnormal combustion is knocking, the knocking detection region can be changed and set in accordance with the properties of the fuel. In addition, whether or not knocking is occurring can be determined when the frequency detected by the knock sensor 21 is greater than a threshold value for knocking determination. [Explanation of symbols]

[0045] 1: Vehicle 10: Engine 12: Piston 13: Spark plug 14: Combustion chamber 16: Intake valve 18: Exhaust valve 21: Knock sensor 22: Crank angle sensor 23: Engine speed sensor 31: Throttle valve 32: Fuel injector 33: Air flow sensor 34: Throttle opening sensor 60: Control device 61: Abnormal combustion determination unit 62: Control unit 63: Property determination unit 64: Setting unit

Claims

1. an abnormal combustion determination means for determining abnormal combustion in the internal combustion engine based on a signal from the knock sensor in a detection region of abnormal combustion; a control means for performing control so as to avoid abnormal combustion in the internal combustion engine when the abnormal combustion determination means determines that abnormal combustion has occurred in the internal combustion engine; A control device for an internal combustion engine having a property determination means for determining a property of fuel supplied to the internal combustion engine, 4. A control device for an internal combustion engine, comprising: a setting means for changing and setting a detection range for abnormal combustion in accordance with the fuel properties determined by said property determining means.

2. The setting means is 2. The control device for an internal combustion engine according to claim 1, wherein the detection range for abnormal combustion is set so as to be expanded as the octane number of the fuel determined by said property determining means becomes lower.

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