Control device for internal combustion engine

Abstract

To suppress combustion noise while improving fuel economy.SOLUTION: A control device 100 for an internal-combustion engine includes a spark-ignition internal-combustion engine 1 to which alcohol fuel containing alcohol is supplied, a sensor 3a that detects an alcohol concentration of the alcohol fuel to be supplied to the internal-combustion engine 1, and an ignition timing control unit 12 that controls an ignition timing of the internal-combustion engine 1 to a reference ignition timing that is a later ignition timing of a predetermined optimal ignition timing and a predetermined knock ignition timing. In a case where the alcohol concentration is higher than a predetermined concentration, when the internal combustion engine 1 is operated in a predetermined region, the ignition timing control unit 12 calculates a target delay amount based on the alcohol concentration, and corrects the reference ignition timing to be delayed by the target delay amount.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] In recent years, research and development has been conducted into improving fuel efficiency, contributing to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy. A known technology related to this type of device is one that improves fuel efficiency while suppressing knocking (see, for example, Patent Document 1). The device described in Patent Document 1 improves fuel efficiency by advancing the ignition timing beyond the optimal ignition timing within a range that does not cause knocking. Furthermore, the higher the alcohol concentration in the fuel, the greater the advance amount. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-013052 Summary of the Invention [Problem to be solved by the invention]

[0004] However, simply increasing the amount of advance as the alcohol concentration in the fuel increases, as in the device of Patent Document 1, makes it difficult to suppress combustion noises such as abnormal noises caused by vibrations of the crankshaft or pistons, and combustion noises when the cylinder pressure level is high. [Means for solving the problem]

[0005] An internal combustion engine control device according to one aspect of the present invention includes a spark-ignition internal combustion engine supplied with alcohol fuel containing alcohol, a sensor for detecting the alcohol concentration of the alcohol fuel supplied to the internal combustion engine, and an ignition timing control unit that controls the ignition timing of the internal combustion engine to a reference ignition timing that is the later of a predetermined optimum ignition timing and a predetermined knock ignition timing that is predetermined to prevent knocking. When the alcohol concentration is higher than a predetermined concentration and the internal combustion engine is operating within a predetermined range, the ignition timing control unit calculates a target retard amount based on the alcohol concentration and corrects the reference ignition timing to be retarded by the target retard amount. [Effects of the Invention]

[0006] According to the present invention, combustion noise can be suppressed while improving fuel efficiency. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a block diagram that schematically shows an example of the overall configuration of a control device for an internal combustion engine according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram for explaining the operating range of the engine in FIG. 1; [Figure 3] 2 is a diagram for explaining the pressure inside the cylinder during high load operation of the engine of FIG. 1; [Figure 4] FIG. 4 is a diagram for explaining cylinder pressure levels corresponding to FIG. 3; [Figure 5] FIG. 2 is a block diagram illustrating an example of a main configuration of the device in FIG. 1. [Figure 6] 6 is a diagram for explaining the ignition timing set by the ignition timing control unit of FIG. 5. [Figure 7] 6 is a diagram for explaining the setting of ignition timing by the ignition timing control unit of FIG. 5; [Figure 8] 8 is a diagram for explaining the second retardation amount in FIG. 7 when the alcohol concentration of the fuel is not taken into consideration. [Figure 9] 8 is a diagram for explaining the second retardation amount in FIG. 7 when the alcohol concentration of the fuel is taken into consideration. FIG. [Figure 10] 8 is a diagram for explaining a case where the second delay amount in FIG. 7 is set to "0." [Figure 11] Similar to Figure 3 for alcohol fuel. [Figure 12] 6 is a flowchart showing an example of processing executed by the ECU of FIG. 5; DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to Figures 1 to 12. A control device for an internal combustion engine according to an embodiment of the present invention can be applied to a vehicle equipped with a spark-ignition internal combustion engine to which alcohol fuel containing alcohol (ethanol) is supplied.

[0009] 1 is a block diagram showing an example of the overall configuration of an internal combustion engine control device (hereinafter referred to as device) 100 according to an embodiment of the present invention. As shown in Fig. 1, device 100 mainly includes engine 1, which is a spark-ignition internal combustion engine mounted on a vehicle (not shown), a fuel tank 2 that stores fuel to be supplied to engine 1, and an electronic control unit (ECU (Electronic Control Unit)) 10 that controls engine 1.

[0010] Engine 1 is provided with an intake amount sensor 1a that detects the amount of intake air of engine 1, a rotation speed sensor 1b that detects the rotation speed (engine rotation speed Ne) of engine 1, and a knock sensor 1c that detects knocking by detecting vibrations of the cylinder block of engine 1. A concentration sensor 3a that detects the alcohol concentration E of the fuel supplied from fuel tank 2 to engine 1 is provided in a fuel supply passage 3 between a fuel pump of fuel tank 2 and an injector of engine 1. Intake amount sensor 1a, rotation speed sensor 1b, knock sensor 1c, and concentration sensor 3a are connected to ECU 10, and signals indicating the detection results of intake amount sensor 1a, rotation speed sensor 1b, knock sensor 1c, and concentration sensor 3a are input to ECU 10.

[0011] FIG. 2 is a diagram illustrating the operating range of engine 1, FIG. 3 is a diagram illustrating the in-cylinder pressure during high-load operation of engine 1, and FIG. 4 is a diagram illustrating cylinder pressure levels corresponding to FIG. 3. The operating range of engine 1 is determined by the engine speed (engine speed Ne) and load of engine 1. The load of engine 1 can be expressed, for example, as the torque or charging efficiency ηc of engine 1. The charging efficiency ηc is the ratio (percentage) of the intake amount per cycle (volume under standard conditions) to the cylinder volume (displacement) of engine 1, and can be calculated based on the intake amount from intake amount sensor 1a. The torque is proportional to the charging efficiency ηc.

[0012] In an operating range higher than the optimal operating line, where the engine 1's net fuel consumption rate is highest, as shown in FIG. 2, particularly in a high-load range near the full-throttle operating line, combustion noise due to combustion may occur. In the high-load range, fluctuations in the engine 1's in-cylinder pressure (combustion pressure) increase, as shown in FIG. 3, and the cylinder pressure level increases, as shown in FIG. 4, exciting vibrations of the engine 1's crankshaft and pistons. In this case, in the high-load range of a predetermined engine speed Ne (Ne1≦Ne≦Ne2, for example, approximately 1800 to 4200 rpm) shown in FIG. 2, vibrations at frequencies (e.g., approximately 200 to 770 Hz) that vehicle occupants may recognize as abnormal noise may increase. Furthermore, in the maximum output range of high-speed, high-load engines (near maximum rotation and full throttle), where the engine 1's output is maximized, the fluctuations in the engine 1's in-cylinder pressure and the cylinder pressure level become extremely large, and the combustion noise itself becomes louder, so that the combustion noise may be recognized as an abnormal noise by vehicle occupants.

[0013] In the abnormal noise generation region AR where combustion noise that can be recognized as abnormal noise occurs, retarding the ignition timing θ of the engine 1 and slowing the combustion speed can smooth fluctuations in the cylinder pressure, lower the cylinder pressure level, and suppress abnormal noise without limiting torque. However, if the ignition timing θ is retarded beyond the optimal ignition timing θm at which the torque of the engine 1 is maximized, the combustion efficiency of the engine 1 decreases and fuel economy deteriorates. Therefore, in this embodiment, the device 100 is configured as follows so that the amount of retardation required to suppress combustion noise can be minimized, thereby suppressing combustion noise while improving the fuel economy of the engine 1.

[0014] 5 is a block diagram showing an example of a configuration of a main part of the device 100. As shown in FIGS. 1 and 5, the device 100 mainly includes an ECU 10, to which an intake air amount sensor 1a, a rotation speed sensor 1b, a knock sensor 1c, a concentration sensor 3a, and the engine 1 are connected. The ECU 10 includes a computer having a processor such as a CPU, memories such as RAM and ROM, and other peripheral circuits. The ECU 10 has an octane number estimation unit 11 and an ignition timing control unit 12 as functional components, and functions as the octane number estimation unit 11 and the ignition timing control unit 12.

[0015] The octane number estimation unit 11 estimates the octane number of the fuel supplied to the engine 1. For example, when the change in the engine speed Ne or the load is small, the ignition timing θ is gradually advanced, and the octane number corresponding to the ignition timing at which knocking is detected by the knock sensor 1c is estimated as the octane number of the fuel supplied to the engine 1. The octane number estimated by the octane number estimation unit 11 (estimated octane number RON (Research Octane Number)) is stored in the memory of the ECU 10.

[0016] Fig. 6 is a diagram for explaining the ignition timing θ of the engine 1 set by the ignition timing control unit 12, and shows an example of the characteristics of the ignition timing θ with respect to the charging efficiency ηc at a specific engine speed Ne (Ne1≦Ne≦Ne2). Fig. 7 is a diagram for explaining the setting of the ignition timing θ by the ignition timing control unit 12.

[0017] The characteristics of the optimum ignition timing θm at which the torque of the engine 1 is maximized are determined in advance according to the engine speed Ne and the charging efficiency ηc through combustion tests, and are stored as a characteristics map in the memory of the ECU 10. The characteristics of the knock ignition timing θk, which is the most advanced ignition timing at which knocking does not occur, are also determined in advance according to the engine speed Ne and the charging efficiency ηc through combustion tests, and are stored as a characteristics map in the memory of the ECU 10. As shown in Figures 6 and 7, the ignition timing that is more retarded between the optimum ignition timing θm and the knock ignition timing θk is set as the reference ignition timing θ0 at which the torque is maximized within the range at which knocking does not occur.

[0018] The characteristics of the optimal ignition timing θm and the knock ignition timing θk are determined by conducting combustion tests for each octane rating. The octane rating of the reference fuel determined for each vehicle is stored in the memory of the ECU 10 as the reference octane rating. In the case of alcohol fuel, the higher the alcohol concentration E, the higher the octane rating and the more difficult it tends to burn. Therefore, the optimal ignition timing θm is shifted to the advanced side as the alcohol concentration E and octane rating of the fuel supplied to the engine 1 increases, and shifted to the retarded side as the alcohol concentration E and octane rating of the fuel decrease. On the other hand, knocking is less likely to occur with a higher octane rating of the fuel and more likely to occur with a lower octane rating of the fuel. Therefore, the knock ignition timing θk is shifted to the advanced side as the alcohol concentration E and octane rating of the fuel increase, and shifted to the retarded side as the alcohol concentration E and octane rating of the fuel decrease.

[0019] Ignition timing control unit 12 calculates the difference ΔRON between the estimated octane number RON and the reference octane number, and calculates a first retard amount Δθ1 by multiplying a predetermined retard amount Δθ by the difference ΔRON (Δθ1=ΔRON×Δθ). If the estimated octane number RON exceeds the reference octane number, ignition timing control unit 12 corrects the knock ignition timing θk so that it is advanced by the first retard amount Δθ1, and if the estimated octane number RON is lower than the reference octane number, ignition timing control unit 12 corrects the knock ignition timing θk so that it is retarded by the first retard amount Δθ1.

[0020] In this way, fuel economy can be improved while suppressing knocking by correcting the ignition timing θ according to the octane number (estimated octane number RON) of the fuel actually supplied to the engine 1 and adjusting the ignition timing to the advance side within a range where knocking does not occur. The predetermined retard amount Δθ is the retard amount when the difference ΔRON between the estimated octane number RON and the reference octane number is "1", and is determined in advance by a combustion test and stored in the memory of the ECU 10.

[0021] Ignition timing control unit 12 calculates the charging efficiency ηc based on the intake air amount detected by intake air amount sensor 1a. Then, referring to the characteristics of the optimum ignition timing θm and the knock ignition timing θk, it determines the reference ignition timing θ0 corresponding to the engine speed Ne and the charging efficiency ηc (load). That is, in the low load region, the optimum ignition timing θm is set as the reference ignition timing θ0, and in the high load region, the knock ignition timing θk is set as the reference ignition timing θ0.

[0022] When the engine 1 is operated in a predetermined abnormal noise generation region AR (for example, Ne1≦Ne≦Ne2 and α≦ηc≦100), the ignition timing control unit 12 corrects the reference ignition timing θ0 to be retarded by a second retard amount Δθ2. In the abnormal noise generation region AR, the reference ignition timing θ0 is retarded and the combustion speed is slowed down, thereby slowing fluctuations in the cylinder pressure, lowering the cylinder pressure level, and suppressing abnormal noise.

[0023] 8 to 10 are diagrams for explaining the second retard amount Δθ2, and show examples of setting the ignition timing θ in the abnormal noise generation region AR. Fig. 8 shows a case where the second retard amount Δθ2 is set taking into consideration only the estimated octane number RON, without considering the alcohol concentration E of the fuel. As shown in Fig. 8, in the case of gasoline fuel (E0) that does not contain alcohol, the estimated octane number RON is high, and the more the knock ignition timing θk, which corresponds to the reference ignition timing θ0 in the abnormal noise generation region AR, is set to the advanced side, the higher the combustion pressure becomes, and the more likely combustion noise is to occur.

[0024] When the estimated octane number RON exceeds a predetermined octane number, the knock ignition timing θk advances relative to the limit ignition timing θmax corresponding to the combustion pressure at which combustion noise occurs, causing combustion noise. For gasoline fuel (E0), the combustion noise can be suppressed by setting the second retard amount Δθ2 so that the ignition timing θ is retarded relative to the limit ignition timing θmax. In this case, the second retard amount Δθ2 can be calculated as the difference between the reference ignition timing θ0 (knock ignition timing θk) and the limit ignition timing θmax.

[0025] The characteristics of the second retard amount Δθ2 for gasoline fuel (E0), i.e., the characteristics of the second retard amount Δθ2 when the alcohol concentration E is "0", are determined in advance according to the engine speed Ne, the charging efficiency ηc, and the estimated octane number RON, and are stored in the memory of the ECU 10 as a characteristics map. That is, the second retard amount Δθ2 is determined as a value greater than "0" within the abnormal noise generation region AR (for example, Ne1≦Ne≦Ne2 and α≦ηc≦100) and when the estimated octane number RON exceeds a predetermined octane number. Also, outside the abnormal noise generation region AR (Ne<Ne1またはNe> Ne2 or ηc<α) or an estimated octane number RON below a specified octane number is defined as "0".

[0026] The second retardation amount Δθ2 may be determined as a constant value within the abnormal noise generation region AR, or may be determined as a value that varies depending on the engine speed Ne or the charging efficiency ηc. The charging efficiency ηc of the engine 1 is correlated with the in-cylinder pressure of the engine 1, and is correlated with the cylinder pressure level that excites vibrations that lead to abnormal noise. By determining the characteristics of the second retardation amount Δθ2 depending on such charging efficiency ηc, it is possible to accurately calculate an appropriate second retardation amount Δθ2 for suppressing abnormal noise.

[0027] 9 and 10 show a case where the second retard amount Δθ2 is set taking into account the alcohol concentration E of the fuel. FIG. 11 is a diagram similar to FIG. 3 for an alcohol fuel containing alcohol. As shown in FIGS. 9 and 10, in the case of alcohol fuel, the higher the alcohol concentration E, the higher the estimated octane number RON, and the knock ignition timing θk, which corresponds to the reference ignition timing θ0 in the abnormal noise generation region AR, is set to the advanced side. Here, alcohol has a slower combustion speed than gasoline and burns relatively gently. For this reason, as shown in FIG. 11, in the case of alcohol fuel, the alcohol concentration E and the estimated octane number RON are high, and even if the knock ignition timing θk is set to the advanced side, the combustion pressure does not increase as much as with gasoline fuel.

[0028] 9 and 10, in the case of alcohol fuel, the limit ignition timing θe, which corresponds to the combustion pressure at which combustion noise occurs, shifts more toward the advance side as the alcohol concentration E increases. With alcohol fuel, combustion noise can be suppressed by setting the second retard amount Δθ2 so that the ignition timing θ is more retarded than the limit ignition timing θe. In this case, the second retard amount Δθ2 can be calculated as the difference between the reference ignition timing θ0 (knock ignition timing θk) and the limit ignition timing θe.

[0029] In the example of FIG. 9 , when the alcohol concentration E exceeds a predetermined alcohol concentration Ex, the knock ignition timing θk becomes more advanced than the limit ignition timing θmax and θe. In other words, when the alcohol concentration is equal to or less than the predetermined alcohol concentration Ex, the knock ignition timing θk becomes more retarded than the limit ignition timing θmax and θe, and when the alcohol concentration is equal to or greater than the predetermined alcohol concentration Ex, the knock ignition timing θk becomes more advanced than the limit ignition timing θmax and θe. In this case, when the alcohol concentration E is higher than the predetermined alcohol concentration Ex, the knock ignition timing θk becomes more advanced than the limit ignition timing θmax and θe, generating combustion noise. In such a case, the combustion noise can be suppressed by setting the second retard amount Δθ2 so that the ignition timing θ becomes more retarded than the limit ignition timing θe when the alcohol concentration E is higher than the predetermined alcohol concentration Ex.

[0030] The characteristics of the second retard amount Δθ2 for alcohol fuel are determined in advance according to the engine speed Ne, the charging efficiency ηc, and the alcohol concentration E, and are stored as a characteristic map in the memory of the ECU 10. That is, the second retard amount Δθ2 is determined to be a value greater than "0" within the abnormal noise generation region AR (for example, Ne1≦Ne≦Ne2 and α≦ηc≦100) and at an alcohol concentration E that exceeds a predetermined alcohol concentration Ex.<Ne1またはNe> Ne2 or ηc<α) or is defined as "0" at an alcohol concentration E less than a predetermined alcohol concentration Ex.

[0031] In the example of Figure 10, when the alcohol concentration E is equal to or less than the predetermined alcohol concentration Ex, the knock ignition timing θk is more advanced than the limit ignition timing θe, and when the alcohol concentration E is equal to or greater than the predetermined alcohol concentration Ex, the knock ignition timing θk is more retarded than the limit ignition timing θe. In this case, even if the alcohol concentration E exceeds the predetermined alcohol concentration Ex and the knock ignition timing θk is more advanced than the limit ignition timing θmax, the knock ignition timing θk is more retarded than the limit ignition timing θe, so combustion noise does not occur. In such a case, there is no need to perform retard correction even when the alcohol concentration E exceeds the predetermined alcohol concentration Ex, so the second retard amount Δθ2 is set to "0."

[0032] The ignition timing control unit 12 refers to a characteristic map stored in the memory of the ECU 10 and calculates a second retard amount Δθ2 corresponding to the engine speed Ne, the charging efficiency ηc, the estimated octane number RON, and the alcohol concentration E. As a result, when the engine 1 is operated in the abnormal noise generation region AR, the second retard amount Δθ2 is calculated based on the alcohol concentration E, and the reference ignition timing θ0 is corrected so as to be retarded by the second retard amount Δθ2, on the condition that the limit ignition timing θe is later than the reference ignition timing θ0 (knock ignition timing θk).

[0033] FIG. 12 is a flowchart showing an example of a process executed by ECU 10. The process shown in this flowchart starts when the vehicle is started and ECU 10 is activated, and is repeated at predetermined time intervals. As shown in FIG. 12, first, in step S1, a difference ΔRON between the estimated octane number RON and a reference octane number is calculated, and a first retard amount Δθ1 is calculated by multiplying a predetermined retard amount Δθ by the difference ΔRON. Next, in step S2, the knock ignition timing θk is corrected so as to be advanced or retarded by the first retard amount Δθ1 (FIG. 6). Next, in step S3, the more retarded ignition timing of the optimal ignition timing θm and the knock ignition timing θk corresponding to the engine speed Ne and the charging efficiency ηc is set as the reference ignition timing θ0 (FIGS. 6 and 7).

[0034] Next, in step S4, it is determined whether the engine 1 is operating in the abnormal noise generation region AR based on the engine speed Ne and the charging efficiency ηc (FIG. 2). If the result in step S4 is affirmative, the process proceeds to step S5, and if the result in step S4 is negative, the process ends. In step S5, a characteristic map stored in the memory of the ECU 10 is referenced, and a second retard amount Δθ2 corresponding to the engine speed Ne, the charging efficiency ηc, the estimated octane number RON, and the alcohol concentration E is calculated (FIGS. 7 to 10). Next, in step S6, the reference ignition timing θ0 is corrected so as to be retarded by the second retard amount Δθ2 (FIGS. 6 and 7).

[0035] By controlling the ignition of the engine 1 using the reference ignition timing θ0 that is retarded between the optimal ignition timing θm and the knock ignition timing θk, it is possible to improve fuel economy while suppressing knocking (step S3). Furthermore, by retarding the reference ignition timing θ0 by the second retard amount Δθ2 in the abnormal noise generation region AR, it is possible to suppress combustion noise while suppressing knocking and improving fuel economy (steps S4, S6). Furthermore, by setting the second retard amount Δθ2 for combustion noise suppression in consideration of the alcohol concentration E of the fuel supplied to the engine 1, it is possible to suppress excessive retardation, suppress knocking, further improve fuel economy, and suppress combustion noise (step S5, FIGS. 8 and 9).

[0036] According to the embodiment of the present invention, the following advantageous effects can be achieved. (1) The device 100 includes an engine 1, which is a spark-ignition internal combustion engine supplied with alcohol fuel containing alcohol, a concentration sensor 3a that detects an alcohol concentration E of the alcohol fuel supplied to the engine 1, and an ignition timing control unit 12 that controls the ignition timing θ of the engine 1 to a reference ignition timing θ0, which is the later of a predetermined optimum ignition timing θm and a predetermined knock ignition timing θk that is determined so as not to cause knocking (step S3 in FIGS. 1, 5, 6, 7, and 12). When the alcohol concentration E is higher than a predetermined alcohol concentration Ex and the engine 1 is operating in a predetermined abnormal noise generation region AR, the ignition timing control unit 12 calculates a second retard amount Δθ2 based on the alcohol concentration E and corrects the reference ignition timing θ0 to be retarded by the second retard amount Δθ2 (steps S4 and S6 in FIGS. 2, 6 to 10, and 12).

[0037] In this way, by controlling the ignition of the engine 1 using the reference ignition timing θ0 that is retarded between the optimal ignition timing θm and the knock ignition timing θk, it is possible to improve fuel economy while suppressing knocking. Furthermore, in the abnormal noise generation region AR, it is possible to suppress combustion noise while suppressing knocking and improving fuel economy by retarding the reference ignition timing θ0 by the second retard amount Δθ2 that corresponds to the alcohol concentration E of the fuel supplied to the engine 1. Furthermore, by setting the second retard amount Δθ2 for combustion noise suppression in consideration of the alcohol concentration E of the fuel supplied to the engine 1, it is possible to suppress excessive retardation, thereby suppressing knocking, further improving fuel economy, and suppressing combustion noise.

[0038] (2) The second retard amount Δθ2 is the difference between the reference ignition timing θ0 and the limit ignition timing θe that is predetermined according to the alcohol concentration E (FIG. 9). The ignition timing control unit 12 corrects the reference ignition timing θ0 to be retarded by the second retard amount Δθ2, on the condition that the limit ignition timing θe is later than the reference ignition timing θ0 (FIGS. 9 and 10). This makes it possible to reliably suppress knocking while suppressing combustion noise.

[0039] (3) The abnormal noise generation region AR is the operating region on the high-load side of the optimal operating line where engine 1's net fuel consumption rate is highest, or the operating region where engine 1 output is at its maximum (Fig. 2). By limiting the ignition timing retard correction for combustion noise suppression to a specific operating region where the combustion pressure peaks sharply and combustion noise is likely to occur, it is possible to minimize the decline in combustion efficiency.

[0040] In the above embodiment, an example was described in which the filling efficiency ηc was calculated based on the intake air amount detected by the intake air amount sensor 1a and used as a physical quantity representing the load on the engine 1, but a sensor that detects torque may also be used as the load on the engine 1.

[0041] The above description is merely an example, and the present invention is not limited to the above-described embodiment and modifications, as long as the features of the present invention are not impaired. One or more of the above-described embodiment and modifications can be arbitrarily combined, and modifications can also be combined with each other. [Explanation of symbols]

[0042] 1 engine, 1a intake air volume sensor, 1b rotation speed sensor, 1c knock sensor, 2 fuel tank, 3 fuel supply passage, 3a concentration sensor, 10 electronic control unit (ECU), 11 octane number estimation section, 12 ignition timing control section, 100 control device (device) of internal combustion engine

Claims

1. a spark-ignition internal combustion engine supplied with alcohol fuel containing alcohol; a sensor for detecting the alcohol concentration of the alcohol fuel supplied to the internal combustion engine; an ignition timing control unit that controls the ignition timing of the internal combustion engine to a reference ignition timing that is a later ignition timing between a predetermined optimum ignition timing and a predetermined knock ignition timing that is determined so as not to cause knocking, the ignition timing control unit calculates a target retard amount based on the alcohol concentration when the alcohol concentration is higher than a predetermined concentration and the internal combustion engine is operated in a predetermined range, and corrects the reference ignition timing so as to retard by the target retard amount.

2. 2. The control device for an internal combustion engine according to claim 1, the target retard amount is a difference between the reference ignition timing and a limit ignition timing that is predetermined according to the alcohol concentration, The ignition timing control unit corrects the reference ignition timing to be retarded by the target retard amount, on the condition that the limit ignition timing is later than the reference ignition timing.

3. 3. The control device for an internal combustion engine according to claim 1, A control device for an internal combustion engine, characterized in that the specified region is an operating region on the high load side of an optimal operating line where the net fuel consumption rate of the internal combustion engine is highest, or an operating region where the output of the internal combustion engine is maximum.

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