Control device for internal combustion engine

Abstract

To suppress a calculation load required for controlling ignition timing .SOLUTION: A control device for an internal combustion engine includes: a spark-ignition type internal combustion engine; a sensor that detects speed and a load; and an ignition timing control section that controls ignition timing on the basis of the speed, the load and characteristics of reference ignition timing defined as later ignition timing among predetermined optimum ignition timing and knock ignition timing. The optimum ignition timing is defined to maximize torque, and the knock ignition timing is defined to prevent occurrence of knocking when fuel of a reference octane value is supplied. The ignition timing control section makes a timing delay correction of the knock ignition timing only by a first timing delay amount obtained by multiplying a difference between an octane value of supplied fuel and the reference octane value by a predetermined timing delay amount, and when either one of a load region on a high load side of an optimum operation line or a maximum output region where output becomes maximum is reached, makes the timing delay correction of the reference ignition timing only by a second timing delay amount based on the predetermined timing delay amount.SELECTED DRAWING: Figure 6

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 and 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 a device that reduces crankshaft rattle noise while preventing a deterioration in the fuel economy of an internal combustion engine (see, for example, Patent Document 1). The device described in Patent Document 1 uses a knock sensor and a bandpass filter to detect crankshaft rattle noise in a predetermined frequency band, compares the detected crankshaft rattle noise with multiple thresholds, and switches between multiple ignition maps used for ignition timing control depending on the comparison results. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-173081 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the ignition timing characteristics are stored in advance as multiple maps and switched depending on the occurrence of crankshaft noise, as in the device of Patent Document 1, the computational load on the device required to control the ignition timing may become excessive. [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, a sensor for detecting the engine speed and load, and an ignition timing control unit for controlling the ignition timing of the internal combustion engine based on the engine speed and load detected by the sensor and characteristics of a reference ignition timing that is determined as the later ignition timing of an optimal ignition timing predetermined according to the engine speed and load or a knock ignition timing. The optimal ignition timing is predetermined to maximize torque according to the engine speed and load. The knock ignition timing is predetermined to prevent knocking when fuel with a reference octane rating is supplied to the internal combustion engine. The ignition timing control unit calculates a first retard amount by multiplying the difference between the octane number of the fuel being supplied to the internal combustion engine and a reference octane number by a predetermined retard amount, and corrects the knock ignition timing to be retarded by the first retard amount. When the operating range of the internal combustion engine defined by the rotation speed and load based on the rotation speed and load detected by the sensor becomes either a predetermined load range on the higher load side than an optimal operating line where the net fuel consumption rate of the internal combustion engine is highest, or a maximum output range where the output of the internal combustion engine is maximum, the ignition timing control unit calculates a second retard amount based on the predetermined retard amount, and corrects the reference ignition timing to be retarded by the second retard amount. [Effects of the Invention]

[0006] According to the present invention, it is possible to reduce the calculation load on the device required to control the ignition timing. [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] 2 is a diagram for explaining pseudo-speed change rotation speed control of the motor generator by the ECU of FIG. 1; [Figure 3] 2 is a diagram for explaining the operating range of the engine in FIG. 1 when pseudo-speed change rotation speed control is performed; [Figure 4] 2 is a diagram for explaining the pressure inside the cylinder during high load operation of the engine of FIG. 1; [Figure 5]FIG. 5 is a diagram for explaining cylinder pressure levels corresponding to FIG. 4. [Figure 6] FIG. 2 is a block diagram illustrating an example of a main configuration of the device in FIG. 1. [Figure 7] 7 is a diagram for explaining the ignition timing set by the ignition timing control unit of FIG. 6. [Figure 8] 7 is a diagram for explaining the setting of ignition timing by the ignition timing control unit of FIG. 6; [Figure 9] FIG. 9 is a diagram for explaining the characteristics of the coefficients in FIG. 8. [Figure 10] 7 is a flowchart showing an example of processing executed by the ECU of FIG. 6; DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of the present invention will be described below with reference to Figures 1 to 10. An internal combustion engine control device according to an embodiment of the present invention can be applied to a vehicle equipped with a spark-ignition internal combustion engine. In particular, an example of application to a series hybrid vehicle (Hybrid Electric Vehicle) that runs by driving a generator using the spark-ignition internal combustion engine and driving an electric motor using the generated electricity will be described below. Note that the present invention can also be applied to vehicles that can switch between a driving mode driven by a generator and a driving mode driven by an internal combustion engine, and to gasoline vehicles that do not have a generator.

[0009] Fig. 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 motor generator 2 connected to the output shaft of engine 1, and an electronic control unit (ECU (Electronic Control Unit)) 10 that controls engine 1 and motor generator 2. A drive shaft 3 of the vehicle is connected to the output shaft of motor generator 2.

[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 of engine 1 (engine rotation speed Ne), and a knock sensor 1c that detects knocking by detecting vibrations of the cylinder block of engine 1. Drive shaft 3 is provided with a vehicle speed sensor 3a that detects vehicle speed V via the rotation speed of drive shaft 3. Intake amount sensor 1a, rotation speed sensor 1b, knock sensor 1c, and vehicle speed sensor 3a are connected to ECU 10, and signals indicative of the detection results of intake amount sensor 1a, rotation speed sensor 1b, knock sensor 1c, and vehicle speed sensor 3a are input to ECU 10.

[0011] 2 is a diagram for explaining pseudo-shift rotation speed control of the motor generator 2 by the ECU 10. Operating the engine 1 so that the power generation efficiency (net fuel consumption rate) is high regardless of the vehicle speed V can improve fuel economy, but it may cause the driver of the vehicle to feel uncomfortable. By simulating a state in which the engine 1 and the drive shaft 3 are connected via a stepped transmission and controlling the engine speed Ne to increase or decrease according to the vehicle speed V (pseudo-shift rotation speed control), it is possible to prevent the driver from feeling uncomfortable.

[0012] The ECU 10 controls the engine speed Ne via the rotation speed of the motor generator 2. More specifically, as shown in FIG. 2, the engine speed Ne is increased or decreased depending on the vehicle speed V between a predetermined upper limit rotation speed NeH and a predetermined lower limit rotation speed NeL. For example, the engine speed Ne is increased or decreased depending on the vehicle speed V at a rate of change R1 when the vehicle speed V is equal to or greater than 0 and less than a threshold value V1, at a rate of change R2 when the vehicle speed V is equal to or greater than the threshold value V1 and less than a threshold value V2, at a rate of change R3 when the vehicle speed V is equal to or greater than the threshold value V2 and less than a threshold value V3, at a rate of change R4 when the vehicle speed V is equal to or greater than the threshold value V3 and less than a threshold value V4, and at a rate of change R5 when the vehicle speed V is equal to or greater than the threshold value V4 (0 <V1<V2<V3<V4,0<R1<R2<R3<R4<R5)。

[0013] FIG. 3 is a diagram for explaining the operating range of the engine 1 when performing pseudo-shift rotation speed control. The operating range of the engine 1 is defined by the rotation speed (engine rotation speed Ne) and load of the engine 1. The load of the engine 1 can be expressed, for example, as the torque Tq or charging efficiency ηc of the 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 the engine 1, and can be calculated based on the intake amount from the intake amount sensor 1a. The torque Tq is proportional to the charging efficiency ηc.

[0014] As shown in Figure 3, when pseudo-shift rotation speed control is not performed, an operating range along the optimal operating line that maximizes the net fuel consumption rate is used. On the other hand, when pseudo-shift rotation speed control is performed, the engine rotation speed Ne is determined according to the vehicle speed V (Figure 2), and the torque Tq is determined according to the engine rotation speed Ne and the amount of power generated by the motor-generator 2, so a wide operating range including the high-load range near the full-throttle operating line is used.

[0015] FIG. 4 is a diagram illustrating the in-cylinder pressure during high-load operation of the engine 1, and FIG. 5 is a diagram illustrating the cylinder pressure level corresponding to FIG. 4. In the high-load region, the fluctuations in the in-cylinder pressure (combustion pressure) of the engine 1 as shown in FIG. 4 increase, resulting in an increase in the cylinder pressure level as shown in FIG. 5, which excites vibrations of the crankshaft of the engine 1 and other components. In this case, in the operating region (abnormal noise generating region AR) of a predetermined engine speed Ne (Ne1≦Ne≦Ne2, for example, approximately 1800 to 4200 rpm) shown in FIG. 3, vibrations at a frequency (for example, approximately 200 to 770 Hz) that a vehicle occupant may recognize as abnormal noise may increase. The abnormal noise generating region AR is a high-load region near the full-throttle operating line, and is an operating region at least on the higher-load side than the optimal operating line. Hereinafter, the abnormal noise generating region AR may be referred to as the "load region."

[0016] In such an abnormal noise generating region AR, by retarding the ignition timing θ of the engine 1 and slowing the combustion speed, it is possible to moderate fluctuations in the cylinder pressure, lower the cylinder pressure level, and suppress abnormal noise without restricting the torque Tq. For example, by defining different characteristics of the ignition timing θ (characteristic maps of the ignition timing θ according to the engine speed Ne and load) for the abnormal noise generating region AR and other operating regions, and switching between these according to the current operating region, it is possible to retard the ignition timing θ in the abnormal noise generating region AR.

[0017] However, depending on the number of gears (five in the example of FIG. 2) in the pseudo speed change rotation speed control and the change rates R1 to R5, the abnormal noise generation region AR may be used frequently, making it necessary to frequently switch the characteristic map of the ignition timing θ. In this case, the calculation load required for controlling the ignition timing θ may become excessive. Therefore, in this embodiment, the device 100 is configured as follows to reduce the calculation load required for controlling the ignition timing θ to suppress abnormal noise by correcting the ignition timing θ according to the operating region of the engine 1.

[0018] 6 is a block diagram showing an example of a configuration of a main part of the device 100. As shown in FIGS. 1 and 6, 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 vehicle speed sensor 3a, the engine 1, and the motor generator 2 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 a rotation speed control unit 11, an octane number estimation unit 12, and an ignition timing control unit 13 as functional components, and functions as the rotation speed control unit 11, the octane number estimation unit 12, and the ignition timing control unit 13.

[0019] The rotation speed control unit 11 controls the engine rotation speed Ne via the rotation speed of the motor generator 2 based on the vehicle speed V detected by the vehicle speed sensor 3a and a predetermined characteristic (FIG. 2).

[0020] The octane number estimation unit 12 estimates the octane number of the fuel supplied to the engine 1. For example, when the engine speed Ne or the load changes little, 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 12 (estimated octane number) is stored in the memory of the ECU 10. Alternatively, the octane number (estimated octane number) of a designated fuel (e.g., regular gasoline, a blended fuel of ethanol and gasoline (E100, E85), etc.) designated for each vehicle may be estimated as the octane number (estimated octane number) of the fuel supplied to the engine 1. In this case, for example, the average octane number of the designated fuel (e.g., RON91 regular gasoline) available on the market is stored in advance in the memory of the ECU 10 as the designated octane number. Then, the octane number estimation unit 12 reads out the designated octane number stored in the memory of the ECU 10, and estimates it as the octane number of the fuel being supplied to the engine 1 (estimated octane number).

[0021] Fig. 7 is a diagram for explaining the ignition timing θ of the engine 1 set by the ignition timing control unit 13, 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. 8 is a diagram for explaining the setting of the ignition timing θ by the ignition timing control unit 13.

[0022] The characteristics of the optimum ignition timing θm at which the torque Tq 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 7 and 8, 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 Tq is maximized within the range at which knocking does not occur.

[0023] The characteristics of the optimum ignition timing θm and the knock ignition timing θk are determined by supplying fuel of a reference octane rating to the engine 1 and conducting a combustion test. The reference octane rating is the octane rating of a reference fuel (e.g., high-octane gasoline), and for example, the average octane rating of commercially available reference fuel (e.g., RON95 high-octane gasoline) is stored as the reference octane rating in the memory of the ECU 10. The optimum ignition timing θm is a constant ignition timing regardless of the octane rating. On the other hand, the lower the octane rating of the fuel, the more likely it is that knocking will occur, so the knock ignition timing θk is shifted to the retard side as the octane rating decreases.

[0024] The ignition timing control unit 13 subtracts the reference octane number from the estimated octane number to calculate the difference ΔRON between the estimated octane number and the reference octane number. If the estimated octane number is lower than the reference octane number (ΔRON<0), the ignition timing control unit 13 multiplies the predetermined delay amount Δθ by the difference ΔRON to calculate a first delay amount Δθ1 (Δθ1=ΔRON×Δθ), and corrects the knock ignition timing θk to be retarded by the first delay amount Δθ1. In this way, if the octane number (estimated octane number) of the fuel supplied to the engine 1 is lower than the reference octane number and knocking is likely to occur, the knock ignition timing θk can be retarded to adjust the ignition timing to a range where knocking does not occur. The predetermined delay amount Δθ is the delay amount when the difference ΔRON between the estimated octane number and the reference octane number is "1." It is determined in advance through combustion tests and stored in the memory of the ECU 10.

[0025] Ignition timing control unit 13 calculates 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, determines a reference ignition timing θ0 corresponding to the engine speed Ne and 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.

[0026] When the engine speed Ne is equal to or greater than the first speed Ne1 and equal to or less than the second speed Ne2 and the charging efficiency ηc is equal to or greater than a predetermined value α, the ignition timing control unit 13 corrects the reference ignition timing θ0 to be retarded when the engine enters a predetermined abnormal noise generation region AR. More specifically, the ignition timing control unit 13 calculates a second retard amount Δθ2 by multiplying the predetermined retard amount Δθ by a predetermined coefficient k (Δθ2 = k × Δθ), and corrects the reference ignition timing θ0 to be retarded by the second retard amount Δθ2. In this way, by retarding the reference ignition timing θ0 in the abnormal noise generation region AR and slowing the combustion speed, fluctuations in the cylinder pressure are slowed, the cylinder pressure level is lowered, and abnormal noise can be suppressed.

[0027] The ignition timing control unit 13 may correct the reference ignition timing θ0 to be retarded, as in the abnormal noise generation region AR, even in the maximum power range where the engine 1 outputs a maximum amount of power at high speeds and high loads (near maximum speeds and near full throttle). In the maximum power range, the fluctuations in the cylinder pressure of the engine 1 (FIG. 4) and the cylinder pressure level (FIG. 5) are larger than in the abnormal noise generation region AR, and the combustion noise itself becomes louder, which may cause the vehicle occupants to recognize the combustion noise as an abnormal noise. In this maximum power range, as in the abnormal noise generation region AR, the ignition timing control unit 13 calculates a second retard amount Δθ2 by multiplying the predetermined retard amount Δθ by a predetermined coefficient k (Δθ2 = k × Δθ), and corrects the reference ignition timing θ0 to be retarded by the second retard amount Δθ2. By retarding the reference ignition timing θ0 even in the maximum power range and slowing the combustion speed, the fluctuations in the cylinder pressure are slowed, the cylinder pressure level is lowered, and the abnormal noise can be suppressed.

[0028] In this way, by performing retard control of the ignition timing θ by correction rather than switching characteristic maps, the computational load is reduced, and timely retard control can be reliably performed even when the abnormal noise occurrence region AR is frequently used by pseudo-shift rotation speed control. Furthermore, by calculating the second retard amount Δθ2 of the reference ignition timing θ0 for suppressing abnormal noise using a common predetermined retard amount Δθ as well as the first retard amount Δθ1 of the knock ignition timing θk corresponding to the octane number of the fuel, the computational load required for controlling the ignition timing θ can be further reduced. In other words, by performing the retard correction for adjusting the ignition timing to a range where knocking does not occur and the retard correction for suppressing abnormal noise in the same way using a common predetermined retard amount Δθ, the computational load required for controlling the ignition timing θ can be further reduced.

[0029] FIG. 9 is a diagram for explaining the characteristics of the coefficient k. The characteristics of the coefficient k are determined in advance according to the engine speed Ne and the charging efficiency ηc through combustion tests, and are stored in the memory of the ECU 10 as a characteristics map. As shown in FIG. 9, the coefficient k is determined to be a value greater than "0" (for example, a natural number) within the abnormal noise generation region AR (Ne1≦Ne≦Ne2 and α≦ηc≦100), and is determined to be a value greater than "0" (for example, a natural number) outside the abnormal noise generation region AR (Ne<Ne1またはNe> Coefficient k may be set to a constant value within the abnormal noise occurrence region AR, or may be set to a value that varies depending on the engine speed Ne or the charging efficiency ηc. Coefficient k may be set depending on the octane number of the fuel supplied to engine 1, in addition to the engine speed Ne and the charging efficiency ηc.

[0030] Although not shown in the figures, when retarding the reference ignition timing θ0 to suppress abnormal noise even in the maximum output range, the coefficient k is set to a value greater than "0" not only in the abnormal noise generation range AR but also in the maximum output range. The coefficient k in the maximum output range may be set to the same value as in the abnormal noise generation range AR, or may be set to a different value. The coefficient k in the maximum output range may also be set according to the octane number of the fuel supplied to the engine 1, in addition to the engine speed Ne and the charging efficiency ηc.

[0031] The charging efficiency ηc of the engine 1 is correlated with the cylinder pressure of the engine 1, and is also correlated with the cylinder pressure level that excites vibrations that lead to abnormal noise. By determining the characteristics of the coefficient k according to such a charging efficiency ηc, it is possible to accurately calculate an appropriate second retard amount Δθ2 for suppressing abnormal noise.

[0032] 10 is a flowchart showing an example of processing executed by the ECU 10. The processing shown in this flowchart is started when the vehicle is started and the ECU 10 is started, and is repeated at predetermined time intervals.

[0033] As shown in Fig. 10, first, in step S1, the difference ΔRON between the estimated octane number and the reference octane number is calculated, and it is determined whether the difference ΔRON is smaller than "0." If the result in step S1 is affirmative, it is determined that the estimated octane number is lower than the reference octane number, and the process proceeds to step S2. If the result in step S1 is negative, it is determined that the estimated octane number is not lower than the reference octane number, and the process proceeds to step S3. In step S2, a first retard amount Δθ1 is calculated by multiplying the predetermined retard amount Δθ by the difference ΔRON, and the knock ignition timing θk is corrected so as to be retarded by the first retard amount Δθ1.

[0034] In step S3, it is determined whether the current operating range corresponding to the engine speed Ne and the charging efficiency ηc (load) is within the abnormal noise generation range AR or the maximum output range. If the result in step S3 is affirmative, the process proceeds to step S4, and if the result in step S3 is negative, the process ends. In step S4, the predetermined retard amount Δθ is multiplied by a coefficient k corresponding to the current engine speed Ne and the charging efficiency ηc (load) to calculate a second retard amount Δθ2, and the reference ignition timing θ0 is corrected so as to be retarded by the second retard amount Δθ2.

[0035] 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; sensors (intake air flow sensor 1a, engine speed sensor 1b) for detecting the engine 1's speed (engine speed Ne) and load (torque Tq, charging efficiency ηc); and an ignition timing control unit 13 for controlling the ignition timing θ of the engine 1 based on the speed and load detected by the sensors and the characteristics of a reference ignition timing θ0, which is determined as the later of an optimal ignition timing θm and a knock ignition timing θk, both of which are predetermined according to the speed and load (FIGS. 1, 6, and 7). The optimal ignition timing θm is predetermined to maximize torque Tq according to the speed and load. The knock ignition timing θk is predetermined to prevent knocking when fuel with a reference octane rating is supplied to the engine 1.

[0036] Ignition timing control unit 13 calculates a first retard amount Δθ1 by multiplying a difference ΔRON between the octane number (estimated octane number) of the fuel supplied to engine 1 and a reference octane number by a predetermined retard amount Δθ, and corrects knock ignition timing θk so as to retard by the first retard amount Δθ1 (steps S1 to S2 in FIGS. 7 and 10). Furthermore, when the operating region of engine 1 defined by the rotation speed and load detected by the sensor is either a predetermined load region (abnormal noise generation region AR) on the higher load side of the optimal operation line where the net fuel consumption rate of engine 1 is highest, or a maximum output region where the output of engine 1 is maximum, ignition timing control unit 13 calculates a second retard amount Δθ2 based on the predetermined retard amount Δθ, and corrects reference ignition timing θ0 so as to retard by the second retard amount Δθ2 (steps S3 to S4 in FIGS. 7 to 9 and 10).

[0037] This allows the reference ignition timing θ0 to be retarded in the abnormal noise generation region AR and the maximum output region without switching characteristic maps, thereby reducing the computational load of the device 100 required to control the ignition timing θ. Furthermore, by performing retard correction using a common predetermined retard amount Δθ for adjusting the knock ignition timing θk according to the fuel octane rating (all regions) and for adjusting the reference ignition timing θ0 for abnormal noise suppression (in the abnormal noise generation region AR and maximum output region), the computational load required to control the ignition timing θ can be further reduced. In other words, the retard correction of the knock ignition timing θk, which is performed when fuel with a lower octane rating than the reference fuel corresponding to the predetermined knock ignition timing θk is supplied, is also applied to the retard correction of the reference ignition timing θ0, which is performed to suppress abnormal noise. This eliminates the need for a separate control for abnormal noise suppression, and by simplifying the overall control of the ignition timing θ, the computational load required to control the ignition timing θ can be further reduced.

[0038] (2) The ignition timing control unit 13 calculates the second delay amount Δθ2 by multiplying the predetermined delay amount Δθ by a predetermined coefficient k (FIG. 8).

[0039] (3) The device 100 further includes a motor-generator 2 connected to the engine 1 and a rotation speed control unit 11 that controls the rotation speed of the engine 1 via the rotation speed of the motor-generator 2 (FIG. 6). When the rotation speed of the engine 1 is controlled via the rotation speed of the motor-generator 2, the torque Tq is determined based on the engine rotation speed Ne and the amount of power generated by the motor-generator 2, allowing for a wide operating range, including a high-load range. In the high-load range, the cylinder pressure level increases due to large fluctuations in the in-cylinder pressure, which may excite vibrations of the crankshaft of the engine 1 and cause abnormal noise. By determining in advance an abnormal noise generation range AR in which such abnormal noise may occur and correcting the reference ignition timing θ0 so that it is retarded within the abnormal noise generation range AR, abnormal noise can be suppressed while reducing the computational load.

[0040] (4) The rotation speed control unit 11 increases or decreases the engine rotation speed Ne at a plurality of different change rates R1 to R5 according to the traveling speed (vehicle speed V) of the vehicle driven by the motor generator 2 (Fig. 2). When performing this type of pseudo-shift rotation speed control, the abnormal noise generation region AR is frequently used depending on the gear position and change rates R1 to R5. Therefore, if retard control of the ignition timing θ is performed by switching characteristic maps, the computational load becomes excessive, and timely retard control may become difficult. By performing retard control of the ignition timing θ by correction rather than switching characteristic maps, the computational load is reduced, and timely retard control can be reliably performed even when the abnormal noise generation region AR is frequently used by pseudo-shift rotation speed control.

[0041] The above embodiment can be modified in various ways. Modifications will be described below. In the above embodiment, an example has been described in which the charging efficiency ηc is 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. However, the sensor for detecting the load on a spark-ignition internal combustion engine is not limited to this. For example, a sensor for detecting torque Tq may be used as the load on the engine 1. In the above embodiment, the predetermined value α is illustrated as a constant independent of the engine speed Ne in FIG. 9 and other figures, but the predetermined value α may be set to change depending on the engine speed Ne.

[0042] 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]

[0043] 1 engine, 1a intake air volume sensor, 1b rotation speed sensor, 1c knock sensor, 2 motor generator, 3 drive shaft, 3a vehicle speed sensor, 10 electronic control unit (ECU), 11 rotation speed control section, 12 octane number estimation section, 13 ignition timing control section, 100 control device (device) of internal combustion engine

Claims

1. A spark-ignition internal combustion engine, a sensor for detecting the rotation speed and load of the internal combustion engine; an ignition timing control unit that controls ignition timing of the internal combustion engine based on the rotation speed and the load detected by the sensor and characteristics of a reference ignition timing that is determined as a later ignition timing between an optimum ignition timing that is predetermined in accordance with the rotation speed and the load and a knock ignition timing, the optimal ignition timing is determined in advance so as to maximize torque according to the rotation speed and the load; the knock ignition timing is determined in advance so as not to cause knocking when fuel having a reference octane number is supplied to the internal combustion engine, The ignition timing control unit calculating a first delay amount by multiplying a difference between the octane number of the fuel supplied to the internal combustion engine and the reference octane number by a predetermined delay amount, and correcting the knock ignition timing so as to delay by the first delay amount; a control device for an internal combustion engine, wherein, when an operating region of the internal combustion engine defined by the rotational speed and the load detected by the sensor becomes either a predetermined load region on the higher load side of an optimal operating line where the net fuel consumption rate of the internal combustion engine is highest, or a maximum output region where the output of the internal combustion engine is maximum, a second retard amount is calculated based on the predetermined retard amount, and the reference ignition timing is corrected to be retarded by the second retard amount.

2. 2. The control device for an internal combustion engine according to claim 1, The control device for an internal combustion engine, wherein the ignition timing control unit calculates the second delay amount by multiplying the predetermined delay amount by a predetermined coefficient.

3. 3. The control device for an internal combustion engine according to claim 1, a motor generator connected to the internal combustion engine; a rotation speed control unit that controls the rotation speed of the internal combustion engine via the rotation speed of the motor generator.

4. 4. The control device for an internal combustion engine according to claim 3, a rotational speed control unit that increases or decreases the rotational speed of the internal combustion engine at a plurality of different change rates according to the traveling speed of a vehicle driven by the motor generator.

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