Control device for internal combustion engine

Abstract

To provide a control device of an internal combustion engine which can perform stable combustion.SOLUTION: A control device of an internal combustion engine having a fuel injection valve for injecting fuel into a cylinder comprises: an ignition timing control part for controlling ignition timing by an ignition plug of the internal combustion engine; an injection timing control part for controlling the injection timing of the fuel from the fuel injection valve; and a pressure control part for controlling the pressure of the fuel which is injected from the fuel injection valve. The ignition timing control part and the injection timing control part set the ignition timing and the injection timing as the same timing, the pressure control part lowers the pressure of the fuel as the ignition timing and the injection timing are closer to timing at which a piston of the internal combustion engine arrives at a top dead point, and the pressure control part raises the pressure of the fuel as the ignition timing and the injection timing are apart from timing at which the piston arrives at the top dead point.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] BACKGROUND ART Internal combustion engines in which a fuel injection valve injects fuel directly into a cylinder are known (see Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-177181 Summary of the Invention [Problem to be solved by the invention]

[0004] Stable combustion is possible by using the attraction effect of attracting sparks to the fuel spray. However, changing the ignition timing reduces the attraction effect, which can lead to unstable combustion. Therefore, the object of this invention is to provide a control device for an internal combustion engine that can ensure stable combustion. [Means for solving the problem]

[0005] The above object can be achieved by a control device for an internal combustion engine having a fuel injection valve that injects fuel into the inside of a cylinder, the control device comprising an ignition timing control unit that controls the timing of ignition by a spark plug of the internal combustion engine, an injection timing control unit that controls the timing of injection of fuel from the fuel injection valve, and a pressure control unit that controls the pressure of fuel injected from the fuel injection valve, wherein the ignition timing control unit and the injection timing control unit synchronize the ignition timing and the injection timing, and the closer the ignition timing and the injection timing are to the time when the piston of the internal combustion engine reaches top dead center, the lower the pressure of the fuel, and the farther the ignition timing and the injection timing are from the time when the piston reaches top dead center, the higher the pressure control unit increases the pressure of the fuel.

[0006] The ignition timing control unit may retard the ignition timing relative to the time when the piston reaches top dead center, and the pressure control unit may increase the fuel pressure when the ignition timing is retarded compared to the fuel pressure at the time when the piston reaches top dead center.

[0007] The spark plug and the fuel injection valve may be provided in a central portion of a ceiling of a combustion chamber of the internal combustion engine.

[0008] The fuel may contain alcohol, and the pressure control unit may control the pressure of the fuel based on the concentration of the alcohol in the fuel and the temperature of the cylinder.

[0009] The pressure control unit may correct the pressure of the fuel based on the temperature of the cylinder, and if the temperature inside the cylinder is higher than the boiling point of the alcohol, the pressure control unit may make the correction to increase the pressure of the fuel, and if the temperature inside the cylinder is lower than the boiling point of the alcohol, the pressure control unit may make the correction to decrease the pressure of the fuel. [Effects of the Invention]

[0010] A control device for an internal combustion engine that is capable of stable combustion can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating an engine system according to the first embodiment. [Figure 2] 2(a) and 2(b) are diagrams illustrating an internal combustion engine. [Figure 3] FIG. 3 is a flowchart illustrating the processing in the first embodiment. [Figure 4] 4(a) is a diagram illustrating fuel pressure, and FIG. 4(b) is a diagram illustrating penetration. [Figure 5] FIG. 5 is a flowchart illustrating the processing in the second embodiment. [Figure 6]6(a) is a diagram illustrating an example of a correction value for fuel pressure, and FIG. 6(b) is a diagram showing the relationship between temperature and fuel pressure. DETAILED DESCRIPTION OF THE INVENTION

[0012] First Embodiment The control device for an internal combustion engine according to this embodiment will be described below with reference to the drawings. Fig. 1 is a diagram illustrating an engine system 100 according to a first embodiment. As shown in Fig. 1, the engine system 100 includes an internal combustion engine 10 and an ECU (Electronic Control Unit) 40.

[0013] The internal combustion engine 10 burns fuel to generate power. The fuel is, for example, a mixture of gasoline and alcohol. The internal combustion engine 10 includes a cylinder head 12 and a cylinder block. The cylinder head 12 is attached to the top of the cylinder block.

[0014] An intake passage 20 and an exhaust passage 22 are connected to the cylinder head 12. A catalyst 24 is provided in the exhaust passage 22.

[0015] A piston 14 is provided inside a cylinder 11 of an internal combustion engine 10. The piston 14 defines a combustion chamber 13 inside the cylinder 11. A fuel injection valve 16 and a spark plug 18 are provided in the center of the roof of the combustion chamber 13. The center is between the part where an intake passage 20 is attached and the part where an exhaust passage 22 is attached. From right to left in FIG. 1, the intake passage 20, fuel injection valve 16, spark plug 18, and exhaust passage 22 are arranged in this order.

[0016] A fuel passage 17 is connected to the fuel injection valve 16. A fuel pump 30 is provided in the fuel passage 17. The fuel pump 30 draws up fuel from a tank (not shown) and supplies it to the fuel passage 17. The fuel passes through the fuel passage 17 and is supplied to the fuel injection valve 16. The fuel injection valve 16 injects the fuel. A regulator 32 adjusts the pressure of the fuel.

[0017] Air flows through intake passage 20 and is introduced into combustion chamber 13 when an intake valve (not shown) opens. Fuel injection valve 16 directly injects fuel into cylinder 11. The air and fuel form a mixture. Spark plug 18 ignites the mixture. The combustion of the mixture moves piston 14, generating power. When an exhaust valve (not shown) opens, exhaust gas generated by combustion is discharged from combustion chamber 13 into exhaust passage 22. Catalyst 24, for example a three-way catalyst, purifies the exhaust gas.

[0018] The ECU 40 is a control device that includes a central processing unit (CPU), random access memory (RAM), read-only memory (ROM), and other storage devices, and performs various controls by executing programs stored in the ROM and storage devices.

[0019] The ECU 40 is connected to the fuel injector 16, the spark plug 18, the temperature sensor 27, the concentration sensor 28, the fuel pump 30, and the regulator 32. The temperature sensor 27 detects the temperature inside the cylinder 11. The ECU 40 obtains the temperature from the temperature sensor 27. The concentration sensor 28 detects the alcohol concentration in the fuel. The ECU 40 obtains the alcohol concentration from the concentration sensor 28.

[0020] The ECU 40 functions as an ignition timing control unit that controls the ignition timing of the spark plug 18. The ECU 40 functions as an injection timing control unit that controls the injection timing of the fuel from the fuel injection valve 16. The ECU 40 synchronizes the ignition timing and the injection timing. The ignition timing and the injection timing may be exactly the same, or may differ by a few degrees in crank angle, for example. The ECU 40 functions as a pressure control unit that controls the pressure of the fuel (fuel pressure) using the regulator 32.

[0021] A spark is generated from the spark plug 18. A fuel spray is injected from the fuel injection valve 16. The air-fuel mixture can be stably burned by utilizing the attraction effect. The attraction effect is the process of attracting a spark to the spray, thereby igniting the air-fuel mixture.

[0022] The ECU 40 warms up the catalyst 24. The warm-up raises the temperature of the catalyst 24 to its activation temperature, improving the exhaust purification performance of the catalyst 24. In the warm-up control, the ECU 40 warms up the catalyst 24 by retarding the ignition timing.

[0023] The ECU 40 synchronizes the ignition timing and the fuel injection timing. If the ignition timing is retarded, the injection timing is also retarded. If the ignition timing and injection timing are changed, the position of the piston 14 when ignition and fuel injection occur changes.

[0024] 2(a) and 2(b) are diagrams illustrating an internal combustion engine 10. As shown in FIGS. 2(a) and 2(b), tumble flow occurs inside a combustion chamber 13. In FIG. 2(a), the position of the piston 14 is at top dead center (TDC). In FIG. 2(b), the position of the piston 14 is away from top dead center. The direction of the tumble flow changes depending on the position of the piston 14.

[0025] When the piston 14 is at top dead center as shown in Figure 2(a), the spray is closer to the center of the tumble flow and is more likely to ride on the tumble flow. As the spray flows toward the spark plug 18, the spark is attracted to the spray. This increases the attraction effect and stabilizes combustion.

[0026] As shown in FIG. 2(b), when the piston 14 moves away from the top dead center, the direction of the tumble flow deviates from the direction of the spray. This makes it difficult for the spray to be swept along by the tumble flow. This reduces the induction effect, which may result in unstable combustion. In the first embodiment, the induction effect is increased by controlling the fuel pressure.

[0027] 3 is a flowchart illustrating the processing in the first embodiment. The ECU 40 determines the ignition timing and the injection timing based on, for example, the intake air temperature and the rotation speed of the internal combustion engine 10 (step S10). The ECU 40 determines the fuel pressure based on the injection timing (step S12). The ECU 40 controls the fuel pressure using the regulator 32 to a desired level (step S14). This completes the processing in FIG. 3.

[0028] FIG. 4(a) is a diagram illustrating fuel pressure. The horizontal axis represents the position of the piston 14. The vertical axis represents fuel pressure. As shown in FIG. 4(a), when the piston 14 is at top dead center (TDC), fuel pressure is at a minimum. As the piston 14 advances or retards from TDC, fuel pressure increases.

[0029] Figure 4(b) is a diagram illustrating penetration. The horizontal axis represents fuel pressure, and the vertical axis represents the strength of spray penetration. As shown in Figure 4(b), the lower the fuel pressure, the weaker the penetration. The higher the fuel pressure, the stronger the penetration. Stronger penetration allows the spray to reach farther and diffuse closer to the spark, increasing the attraction effect.

[0030] According to the first embodiment, the ECU 40 synchronizes the ignition timing and the injection timing. The closer the ignition timing and the injection timing are to the time when the piston 14 reaches TDC (TDC time), the lower the fuel pressure is set by the ECU 40. The induction effect is high, which stabilizes combustion. The lower fuel pressure improves fuel economy. The further the ignition timing and the injection timing are from TDC, the higher the fuel pressure is set by the ECU 40. As shown in FIG. 4(b), the penetration of the spray becomes stronger. The induction effect is high, which stabilizes combustion. Stable combustion is possible regardless of the position of the piston 14.

[0031] The ECU 40 retards the ignition timing, for example, to warm up the catalyst 24. The ignition timing and injection timing are retarded from the TDC timing. The ECU 40 determines the fuel pressure based on the ignition timing and injection timing. During catalyst warm-up, the ECU 40 increases the fuel pressure to strengthen penetration. A spark is attracted to the spray and ignites it. Stable combustion is possible even during catalyst warm-up.

[0032] The fuel injection valve 16 and the spark plug 18 are located in the center of the ceiling of the combustion chamber 13. The spark generated by the spark plug 18 is attracted to the spray injected from the fuel injection valve 16. Ignition occurs due to the attraction effect, allowing for stable combustion.

[0033] The internal combustion engine 10 may have one or more cylinders 11. Each cylinder 11 is formed with a combustion chamber 13. The ECU 40 controls the ignition timing and injection timing for each combustion chamber 13, and also controls the fuel pressure. Stable combustion is possible in each combustion chamber 13.

[0034] Second Embodiment Description of the same configuration as in the first embodiment will be omitted. The configuration in FIG. 1 is also common to the second embodiment. The fuel injection valve 16 may inject a mixed fuel of alcohol and gasoline. Gasoline vaporizes within a certain temperature range (T1 to T2). On the other hand, alcohol does not vaporize easily at temperatures below its boiling point, but vaporizes rapidly at its boiling point. At temperatures where alcohol does not vaporize, the spray penetration is strong, and the attraction effect is large. At temperatures above the temperature where alcohol vaporizes, the spray penetration is weak, and the attraction effect is small. In the second embodiment, the attraction effect is increased by correcting the fuel pressure.

[0035] 5 is a flowchart illustrating the processing in the second embodiment. The ECU 40 performs steps S10 and S12 to determine the fuel pressure based on the ignition timing and the injection timing.

[0036] The ECU 40 acquires the temperature inside the cylinder 11 (in-cylinder temperature) from the temperature sensor 27 and acquires the alcohol concentration in the fuel from the concentration sensor 28 (step S20). The ECU 40 acquires a correction value for the fuel pressure based on the in-cylinder temperature and the alcohol concentration (step S22). The ECU 40 controls the fuel pressure based on the fuel pressure determined in step S12 and the correction value acquired in step S22 (step S24). The ECU 40 adds the correction value to the fuel pressure determined in step S12 to correct the fuel pressure. This completes the processing of FIG. 5.

[0037] FIG. 6(a) is a diagram illustrating an example of a correction value for fuel pressure. The horizontal axis represents the temperature inside the cylinder 11. The vertical axis represents the correction value for fuel pressure. Temperature Tb is the boiling point of alcohol. The left side of the horizontal axis represents temperatures lower than boiling point Tb. The right side represents temperatures higher than Tb. Temperature T1 is lower than boiling point Tb and is the temperature at which gasoline vaporizes. Temperature T2 is higher than boiling point Tb and is the temperature at which gasoline completely vaporizes. The dotted line in FIG. 6(a) represents an example where the alcohol concentration is 50%. The solid line represents an example where the alcohol concentration is 100%.

[0038] If the alcohol concentration is 0%, the correction value is 0 at any temperature. If the alcohol concentration is greater than 0%, the correction value will be a value other than 0. If the in-cylinder temperature is lower than the boiling point Tb, the correction value will be a negative value. If the in-cylinder temperature is higher than the boiling point Tb, the correction value will be a positive value. The closer the in-cylinder temperature is to the boiling point Tb, the larger the absolute value of the correction value. The farther the in-cylinder temperature is from the boiling point Tb, the smaller the absolute value of the correction value. The absolute value of the correction value when the alcohol concentration is 100% is larger than the absolute value of the correction value when it is 50%. The higher the alcohol concentration, the larger the absolute value of the correction value.

[0039] FIG. 6(b) is a diagram showing the relationship between temperature and fuel pressure. The horizontal axis represents the position of the piston 14. The vertical axis in the upper row represents the temperature inside the cylinder 11 (in-cylinder temperature). The vertical axis in the lower row represents fuel pressure. As shown in the upper row, when the position of the piston 14 is TDC, the in-cylinder temperature is at its highest and is higher than T2. ​​When the position of the piston 14 is retarded or advanced from TDC, the in-cylinder temperature becomes lower than T2. ​​The in-cylinder temperature can be higher or lower than the boiling point Tb of alcohol, or can be lower than T1.

[0040] In the lower part of Figure 6(b), the dotted line represents the fuel pressure without correction. The solid line represents the fuel pressure after correction. When the in-cylinder temperature is less than T1 or greater than T2, the fuel pressure is not corrected. When the in-cylinder temperature is greater than T1 and less than Tb, the correction value is negative. The corrected fuel pressure is lower than the dotted line example. When the in-cylinder temperature is greater than Tb and less than T2, the correction value is positive. The corrected fuel pressure is higher than the dotted line example. The closer the in-cylinder temperature is to the boiling point Tb, the larger the absolute value of the correction value. The corrected fuel pressure moves away from the dotted line. The farther the in-cylinder temperature is from the boiling point Tb, the smaller the absolute value of the correction value. The corrected fuel pressure moves closer to the dotted line.

[0041] According to the second embodiment, the ECU 40 controls the pressure of the fuel based on the alcohol concentration in the fuel and the temperature inside the cylinder 11. This can enhance the induction effect and enable stable combustion.

[0042] The ECU 40 corrects the fuel pressure. When the in-cylinder temperature is equal to or greater than T1 but less than Tb, alcohol is less likely to vaporize. Penetration is strong and the induction effect is high. The ECU 40 sets the correction value to a negative value. Because the negative correction value is added, the fuel pressure after correction is lower than before correction. Fuel efficiency can be improved. When the in-cylinder temperature is equal to or greater than Tb but less than T2, alcohol is more likely to vaporize. Penetration becomes weaker. The ECU 40 sets the correction value to a positive value. Because the positive correction value is added, the fuel pressure after correction is higher than before correction. Penetration becomes stronger and the induction effect becomes higher. Stable combustion is possible.

[0043] The higher the alcohol concentration, the larger the absolute value of the correction value. Higher fuel pressure results in stronger penetration and more stable combustion. The lower the alcohol concentration, the smaller the absolute value of the correction value. Lower fuel pressure improves fuel efficiency.

[0044] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims. [Explanation of symbols]

[0045] 10 internal combustion engines, 11 cylinders 12 cylinder head, 13 combustion chamber 14 pistons, 16 fuel injectors 17 fuel passage, 18 spark plug 20 intake passage, 22 exhaust passage 24 Catalyst, 27 Temperature sensor 28 concentration sensor, 30 fuel pump 32 regulators, 40 ECUs 100 Engine System

Claims

1. A control device for an internal combustion engine having a fuel injection valve that injects fuel into the inside of a cylinder, an ignition timing control unit that controls the ignition timing of the spark plug of the internal combustion engine; an injection timing control unit that controls the injection timing of fuel from the fuel injection valve; a pressure control unit that controls the pressure of fuel injected from the fuel injection valve, the ignition timing control unit and the injection timing control unit synchronize the ignition timing and the injection timing, the pressure control unit reduces the pressure of the fuel as the ignition timing and the injection timing approach the timing when the piston of the internal combustion engine reaches the top dead center; the pressure control unit increases the pressure of the fuel as the ignition timing and the injection timing become farther from the timing when the piston reaches the top dead center; the ignition timing control unit retards the ignition timing from a timing when the piston reaches top dead center, The pressure control unit increases the fuel pressure when the ignition timing is retarded compared to the fuel pressure when the piston reaches top dead center.

2. 2. The control device for an internal combustion engine according to claim 1, wherein the ignition plug and the fuel injection valve are provided in a central portion of a ceiling of a combustion chamber of the internal combustion engine.

3. the fuel comprises alcohol; 2. The control device for an internal combustion engine according to claim 1, wherein the pressure control unit controls the pressure of the fuel based on the concentration of the alcohol in the fuel and the temperature of the cylinder.

4. the pressure control unit corrects the pressure of the fuel based on the temperature of the cylinder; When the temperature inside the cylinder is higher than the boiling point of the alcohol, the pressure control unit performs the correction so as to increase the pressure of the fuel, 4. The control device for an internal combustion engine according to claim 3, wherein when the temperature inside the cylinder is lower than the boiling point of the alcohol, the pressure control unit performs the correction so as to lower the pressure of the fuel.

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