Control device of direct injection type internal combustion engine

Abstract

To provide a control device of a direct injection type internal combustion engine capable of reducing a portion of injected fuel not contributing to combustion in injected fuel, and suppressing extinguishing of spark from an ignition plug.SOLUTION: A control device for a direct injection internal combustion engine in which fuel containing alcohol is directly injected into a cylinder by an injector and ignited by a spark plug, is configured to, when a rising edge of an ignition signal to the spark plug is detected while fuel is being injected from the injector, stop the injection of fuel from the injector.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] Conventionally, in order to reliably supply the required amount of fuel according to the driving state of the vehicle to the cylinder, a direct injection type internal combustion engine is known in which fuel is directly injected into the cylinder. In addition, against the background of the recent rise in crude oil prices and the growing interest in global warming, etc., alcohol-mixed fuels, in which alcohol such as ethanol or methanol is mixed with gasoline, are sometimes used in internal combustion engines as a fuel to replace fossil fuels. However, alcohol has a higher boiling point and lower volatility than gasoline, and the higher the alcohol concentration, the more difficult it is for the fuel to atomize or vaporize. Therefore, the higher the alcohol concentration of the alcohol-mixed fuel is, or the lower the temperature is, the more difficult it is to burn. As a result, good combustion of the mixture cannot be obtained, which may cause a delayed or poor start of the internal combustion engine, or an increase in the emission of harmful substances.

[0003] In order to address these problems, a control has been disclosed in which fuel is injected at a high temperature near the top dead center of compression and with a high fuel injection pressure as an injection method for promoting the vaporization of high alcohol concentration fuel during cold start-up (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-037968 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when fuel is injected near the top dead center of the compression stroke, the injection timing and the ignition timing may overlap during the compression stroke due to factors such as the expansion or contraction of the control interval caused by structural variations in each internal combustion engine, or deviations in control calculations. When the injection timing and the ignition timing overlap in this way, there is still fuel injected after ignition, which does not contribute to combustion and may extinguish the spark of the spark plug due to the fuel injected during ignition.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a control device for a direct injection internal combustion engine that can reduce the amount of injected fuel that does not contribute to combustion and suppress the extinguishing of the spark from the spark plug. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the objective, the control device for a direct injection internal combustion engine of the present invention is a control device for a direct injection internal combustion engine in which fuel containing alcohol is directly injected into a cylinder by an injector and ignited by an ignition plug, and is characterized in that when fuel is being injected from the injector, if a rising edge of an ignition signal to the spark plug is detected, the injection of fuel from the injector is stopped. Effect of the Invention

[0008] According to the present invention, it is possible to reduce the amount of injected fuel that does not contribute to combustion, and to suppress extinguishing of the spark of the ignition plug. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of a schematic configuration of a direct injection type internal combustion engine according to a first embodiment. [Diagram 2] FIG. 2 is a diagram for explaining the operation of compression top dead center injection and multi-injection. [Diagram 3]FIG. 3 is a diagram for explaining switching of the injection method based on the alcohol concentration and temperature of the fuel. [Figure 4] FIG. 4 is a diagram for explaining the injection timing and the ignition timing of a conventional direct injection type internal combustion engine. [Diagram 5] FIG. 5 is a diagram showing an example of a timing chart illustrating the injection timing and the ignition timing of the internal combustion engine according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing an example of a timing chart illustrating the injection timing, the ignition timing, and the operation of the ignition retard control of the internal combustion engine according to the second embodiment. [Figure 7] FIG. 7 is a diagram showing an example of an ignition retard table used for the operation of the internal combustion engine according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of a control device for a direct injection internal combustion engine according to the present invention will be described in detail with reference to Figures 1 to 7. Furthermore, the present invention is not limited to the following embodiment, and the components in the following embodiment include those that a person skilled in the art can easily conceive, those that are substantially the same, and those that are within the scope of what is called equivalent. Furthermore, various omissions, substitutions, modifications, and combinations of the components can be made without departing from the spirit of the following embodiment.

[0011] [First embodiment] (Schematic configuration of a direct injection internal combustion engine) Fig. 1 is a diagram showing an example of a schematic configuration of a direct injection type internal combustion engine according to the first embodiment. With reference to Fig. 1, the schematic configuration of a direct injection type internal combustion engine 1 according to this embodiment will be described.

[0012] The internal combustion engine 1 shown in Fig. 1 is a direct injection reciprocating engine in which fuel is directly injected from an injector into a combustion chamber in a cylinder. As shown in Fig. 1, the internal combustion engine 1 includes a cylinder 10, a combustion chamber 11, an intake valve 12, an exhaust valve 13, an injector 14, a spark plug 15, an intake passage 21, an exhaust passage 22, and a throttle valve 23.

[0013] The cylinder 10 is a cylinder in which a piston (a piston 31 described below) reciprocates due to the force of combustion of fuel in a combustion chamber 11. The internal combustion engine 1 is provided with a plurality of cylinders 10.

[0014] The combustion chamber 11 is a space defined by the inner wall of the cylinder 10 and the upper surface of the piston, in which fuel is burned.

[0015] The intake valve 12 is a valve mechanism for controlling the air supplied into the combustion chamber 11 through the intake passage 21. The exhaust valve 13 is a valve mechanism for exhausting the combustion gas generated when the fuel is combusted in the combustion chamber 11.

[0016] The injector 14 is a device that injects alcohol-mixed fuel (hereinafter sometimes simply referred to as fuel) made by mixing alcohol with gasoline into the combustion chamber 11 in the form of a mist under the control of an ECU (Electronic Control Unit) 50 described later.

[0017] The ignition plug 15 is a device that ignites and burns (explodes) a mixture of air supplied to the combustion chamber 11 via the intake passage 21 and fuel injected by the injector 14. Specifically, the ignition plug 15 ignites the mixture just before the piston 31, which moves up and down inside the cylinder 10, reaches the top dead center.

[0018] The intake passage 21 is connected to the combustion chamber 11 via the intake valve 12 and is a passage for supplying air into the combustion chamber 11 via the intake valve 12. The intake passage 21 branches off at a position upstream of the intake valve 12 and is connected to the combustion chamber 11 of each cylinder 10. The exhaust passage 22 is connected to the combustion chamber 11 via the exhaust valve 13 and is a passage for discharging combustion gas after combustion in the combustion chamber 11 via the exhaust valve 13.

[0019] The throttle valve 23 is a valve device that is disposed in the intake passage 21 and has an opening controlled by the ECU 50 to adjust the flow rate of air flowing through the intake passage 21 .

[0020] As shown in FIG. 1, the internal combustion engine 1 further includes a piston 31, a connecting rod 32, a crankshaft 33, a flywheel , and a crank angle sensor .

[0021] The piston 31 is connected to the crankshaft 33 via the connecting rod 32, and is a member that moves up and down inside the cylinder 10 by receiving the expansion force caused by the combustion (explosion) of the air-fuel mixture in the combustion chamber 11. The connecting rod 32 is a member that connects the piston 31 and the crankshaft 33, and converts the up and down movement (reciprocating movement) of the piston 31 caused by the force caused by the combustion (explosion) of the air-fuel mixture in the combustion chamber 11 into the rotational movement of the crankshaft 33.

[0022] The crankshaft 33 is a rotating shaft that rotates when the force of the up and down movement of the piston 31 is transmitted by the connecting rod 32 .

[0023] The flywheel 34 is a wheel member that is fixed to the crankshaft 33 and rotates in conjunction with the rotation of the crankshaft 33. The flywheel 34 stabilizes the rotation of the crankshaft 33 by the moment of inertia generated by its rotation.

[0024] The crank angle sensor 40 is disposed near the flywheel 34 and detects the rotation angle of the crankshaft 33. The crank angle sensor 40 outputs information on the detected rotation angle to the ECU 50, and the ECU 50 calculates the rotation speed of the crankshaft 33, i.e., the engine speed, based on the received information on the rotation angle.

[0025] The ECU 50 is a control device (controller) that calculates the engine speed from the rotation angle of the crankshaft 33 detected by the crank angle sensor 40, and controls the operations of the injector 14, the spark plug 15, and the throttle valve 23. The ECU 50 includes a memory 51 that stores programs, various parameters, and the like.

[0026] (About compression top dead center injection and multi-injection) Fig. 2 is a diagram for explaining the operation of the compression top dead center injection and the multi-injection. Fig. 3 is a diagram for explaining switching of the injection method based on the alcohol concentration and temperature of the fuel. The compression top dead center injection and the multi-injection in the internal combustion engine 1 according to the present embodiment will be described with reference to Figs. 2 and 3.

[0027] First, multi-injection (stratified injection) will be described with reference to Fig. 2. Multi-injection is a control method in which fuel used in one combustion is not injected all at once when the injector 14 injects fuel into the combustion chamber 11, but is divided into several injections. For example, the example shown in Fig. 2 shows a multi-injection consisting of a first injection 101 that injects 20[%] of the fuel used in one combustion at a timing 260[%] advance from the top dead center (TDC) as the reference (0[deg]), a second injection 102 that injects 20[%] of the fuel at a timing 180[deg] advance from the top dead center, and a third injection 103 that injects the remaining 60[%] of the fuel at a timing 30[deg] advance from the top dead center, with one reciprocation of the piston 31 being a 360[deg] combustion cycle. 2 shows that after fuel is injected in three separate injections, a first injection 101, a second injection 102, and a third injection 103, ignition occurs at a timing 5° advanced from the top dead center. Note that, although the example shown in FIG. 2 shows an example in which the injection is divided into three separate injections as a multi-injection, the number of injections is not limited to three, and injection may be divided into other numbers of injections.

[0028] By injecting fuel into the combustion chamber 11 in several injections using this type of multi-injection control method, it is possible to easily atomize the fuel within the combustion chamber 11, improve premixing with the air supplied through the intake valve 12, and suppress the drop in temperature of the air-fuel mixture due to the latent heat of vaporization, making it easier to combust the mixture.

[0029] Next, the compression top dead center injection will be described. The compression top dead center injection is a control method in which, when the piston 31 reaches the vicinity of the top dead center, the fuel used for one combustion is injected into the combustion chamber 11 at once by utilizing the temperature of the compressed air in the combustion chamber 11 near the compression end (top dead center) temperature.

[0030] By injecting fuel into the combustion chamber 11 all at once near the compression end temperature using this control method of top dead center injection, the temperature near the compression end temperature can be utilized to promote fuel vaporization and burn the fuel in a state where it is combusted, thereby improving thermal efficiency.

[0031] Next, with reference to FIG. 3, the relationship between the alcohol concentration of the fuel (alcohol-blended fuel) being used and the temperature will be described.

[0032] FIG. 3 shows an example of the relationship between the alcohol concentration of the fuel (alcohol-mixed fuel) being used and the temperature. As shown in the example in FIG. 3, in the case of high concentration and low temperature, such as when the alcohol concentration of the fuel is 60[%] or more and the temperature is 20[°C] or less, both at the start of the internal combustion engine 1 and after the start, the internal combustion engine 1 is controlled by compression top dead center injection, which uses the temperature near the compression end temperature to inject and burn the fuel at once, and the fuel is burned in a state where the fuel vaporization is promoted. Also, when the alcohol concentration of the fuel is 650[%] or more and less than 60[%] and the temperature is 20[°C] or less, only at the start of the internal combustion engine 1, the internal combustion engine 1 is controlled by compression top dead center injection, which uses the temperature near the compression end temperature to inject and burn the fuel at once. In other alcohol concentration and temperature ranges, the internal combustion engine 1 is controlled by multi-injection both at the start of the internal combustion engine 1 and after the start of the internal combustion engine 1. Note that the switching of the control method shown in FIG. 3 is an example, and the control method can be appropriately switched depending on the characteristics of the fuel, and the characteristics or structure of the vehicle and the internal combustion engine 1.

[0033] (Problems with conventional control) 4 is a diagram for explaining the injection timing and ignition timing of a conventional direct injection internal combustion engine. With reference to FIG. 4, problems with the conventional direct injection internal combustion engine will be explained.

[0034] Fig. 4 explains the operation of injecting and igniting fuel three times using a multi-injection control method in a conventional direct injection internal combustion engine. Specifically, the example shown in Fig. 4 shows a multi-injection consisting of a first injection 111 which is the first injection, a second injection 112 which is the second injection, and a third injection 113 which is the third (last) injection.

[0035] The last injection of the multiple injections (third injection 113 in FIG. 3) needs to be injected as late as possible because the temperature near the compression end is used to promote vaporization, and because injection at an advanced timing cools the air-fuel mixture already in the combustion chamber 11. In addition, the ignition timing needs to be as early as possible on the advanced side within the range in which the piston 31 does not rotate in the reverse direction, because ignition on the retarded side reduces the thermal efficiency of combustion and also reduces torque.

[0036] As a result, as shown in Figure 4, an event may occur in which the final injection timing overlaps with the ignition timing. When this event occurs, the fuel after ignition does not contribute to combustion, so there is a problem that the unburned fuel is exhausted and the fuel is wasted. In addition, since the fuel is ignited by the spark plug while it is being injected from the injector, there is a problem that the ignition spark may be extinguished due to the turbulence of the injected fuel in the combustion chamber. Note that the above problem can occur not only with a control method using multiple injections, but also with a control method using compression top dead center injection.

[0037] In this embodiment, the control operation for solving the above-mentioned problems will be described in detail below.

[0038] (Control operation for the internal combustion engine according to this embodiment) 5 is a diagram showing an example of a timing chart illustrating the injection timing and the ignition timing of the internal combustion engine according to the first embodiment. With reference to FIG. 5, the control operation by the ECU 50 for the internal combustion engine 1 according to the present embodiment will be described.

[0039] The timing chart shown in FIG. 5(a) shows the operation in which the last injection timing overlaps with the ignition timing in the multi-injection in a conventional direct injection internal combustion engine. As shown in FIG. 5(a), when the injection signal for the injector goes from a low level to an intermediate level (a level between a low level and a high level), preparation for the injection operation is performed, and when it goes from the intermediate level to a high level, fuel is injected into the combustion chamber. The three sections in which the injection signal shown in FIG. 5(a) is at a high level correspond to the first injection 111, the second injection 112, and the third injection 113 shown in FIG. 4, respectively. Then, as shown in FIG. 5(a), during the third injection, the ignition signal goes from a low level to a high level, and the spark plug is ignited. As a result, as described above, the fuel after ignition does not contribute to combustion, so that unburned fuel is exhausted, wasting fuel, and there is a risk that the ignition spark will be extinguished due to the turbulence of the fuel in the combustion chamber caused by the injection.

[0040] Therefore, the ECU 50 according to this embodiment executes the control shown in the timing chart shown in FIG. 5(b) for the internal combustion engine 1. That is, as shown in FIG. 5(b), when the ECU 50 detects that the ignition signal to the spark plug 15 has changed from a low level to a high level (detects the rising edge of the ignition signal) while the injection signal for the last injection (here, the third injection) is being output to the injector 14 at a high level, that is, during the injection of fuel by the injector 14, the ECU 50 stops output of the injection signal (sets the injection signal to a low level) and stops the injection of fuel from the injector 14. As a result, fuel is not injected during the ignition of the spark plug 15, so that fuel that does not contribute to combustion can be eliminated and the ignition spark of the spark plug 15 due to injection can be prevented from being blown out. In addition, since the blowing out of the ignition spark can be prevented, the robustness of the internal combustion engine 1 at the time of starting can be improved, the deterioration of combustion can be suppressed, and further, the output fluctuation between the cylinders can be suppressed and the vibration can be suppressed. In addition, because it is possible to eliminate fuel that does not contribute to combustion, exhaust gases are improved compared to conventional control, unburned gases and CO can be reduced, and fuel economy can also be improved.

[0041] 5(b), some fuel will not be completely blown off because fuel injection is stopped, but in this case, when ECU 50 detects that the ignition signal has changed from a low level to a high level (detects the rising edge of the ignition signal), it may perform control to temporarily increase the pressure (fuel pressure) of the fuel injection from injector 14 and blow off the amount of fuel to be injected, thereby stopping the injection. This allows the fuel to be completely blown off in the third injection, and makes it possible to suppress a decrease in torque due to a decrease in the amount of fuel contributing to combustion.

[0042] In addition, the control operation of the ECU 50 according to the present embodiment described above and shown in FIG. 5(b) for the internal combustion engine 1 is not limited to the case of multi-injection, but can also be applied to the case of compression top dead center injection.

[0043] As described above, in the ECU 50 that controls the internal combustion engine 1 according to the present embodiment, when the rising edge of the ignition signal for the spark plug 15 is detected while fuel is being injected from the injector 14 into the direct injection type internal combustion engine 1 in which fuel containing alcohol is directly injected into the cylinder 10 (combustion chamber 11) by the injector 14 and ignited by the spark plug 15, the ECU 50 stops the injection of fuel from the injector 14. This reduces the amount of fuel that does not contribute to combustion in the injected fuel, and prevents the spark of the spark plug 15 from being blown out. In addition, since the blowing out of the ignition spark can be prevented, the robustness of the internal combustion engine 1 at the time of starting can be improved, the deterioration of combustion can be suppressed, and further, output fluctuation between cylinders can be suppressed and vibration can be suppressed. In addition, since the fuel that does not contribute to combustion can be eliminated, exhaust gas is improved compared to conventional control, unburned gas and CO can be reduced, and fuel efficiency can be improved.

[0044] [Second embodiment] The control operation of the ECU 50 that controls the internal combustion engine 1 according to the second embodiment will be described, focusing on the differences from the first embodiment. In the first embodiment, the control focusing on a specific cylinder 10 of the internal combustion engine 1 was described. In this embodiment, when the above-mentioned control of the injection timing and ignition timing of a specific cylinder 10 occurs, the control operation for other cylinders 10 that is executed in conjunction with the above-mentioned control will be described. Note that the configurations of the internal combustion engine 1 and the ECU 50 according to this embodiment are similar to those described in the first embodiment.

[0045] (Control operation for the internal combustion engine according to this embodiment) Fig. 6 is a diagram showing an example of a timing chart showing the operation of the injection timing, ignition timing, and ignition retard control of the internal combustion engine according to the second embodiment. Fig. 7 is a diagram showing an example of an ignition retard table used in the operation of the internal combustion engine according to the second embodiment. The control operation by the ECU 50 for the internal combustion engine 1 according to this embodiment will be described with reference to Figs. 6 and 7.

[0046] The timing chart shown in FIG. 6(a) shows the operation in which the final injection timing overlaps with the ignition timing in multiple injections in a conventional direct injection internal combustion engine, and is similar to the timing chart shown in FIG. 5(a) described above.

[0047] Among the timing charts shown in Fig. 6(b), the timing charts for the injection signal and the ignition signal are the same as those shown in Fig. 5(b) above. As a result, fuel is not injected during ignition of the spark plug 15, so that fuel that does not contribute to combustion can be eliminated, but combustion with the amount of fuel that should be injected is not performed, and the rotation speed (engine speed) of the internal combustion engine 1 may decrease. In this case, the ignition timing is retarded for the cylinders 10 other than the cylinders 10 for which the above-mentioned control of the injection timing and ignition timing was performed, and further, the ignition timing is retarded in the next combustion cycle for the cylinders 10 for which the control of the injection timing and ignition timing was performed, thereby suppressing and recovering the decrease in the engine speed.

[0048] Specifically, as shown in FIG. 6(b), when the ECU 50 detects that the ignition signal to the spark plug 15 has changed from a low level to a high level (detects the rising edge of the ignition signal) and stops outputting the injection signal (sets the injection signal to a low level), it turns on the cut flag. After turning on the cut flag, the ECU 50 determines whether the engine speed calculated from the output of the crank angle sensor 40 has decreased. Then, for example, when the difference between the immediately preceding engine speed (for example, the engine speed a predetermined unit time ago) and the current engine speed is set to ΔNE [rpm], if the absolute value of the ΔNE becomes equal to or greater than a predetermined threshold, the ECU 50 performs control to retard the ignition timing according to the amount of decrease in the engine speed for cylinders 10 other than the cylinder 10 for which the control of the injection timing and ignition timing has been performed, as shown in FIG. 6(b) (hereinafter, this may be referred to as ignition retard control). In this case, the ECU 50 stores in advance in the memory 51 an ignition retard table in which ΔNE (absolute value) as shown in FIG. 7 corresponds to the retard amount of the ignition timing, and executes the ignition retard control by the retard amount corresponding to the absolute value of the calculated ΔNE (negative value when the engine speed is decreasing) by referring to the ignition retard table. Furthermore, the ECU 50 executes the ignition retard control in the next combustion cycle for the cylinders 10 for which the control of the injection timing and the ignition timing has been performed. As a result, the injection time of the fuel before ignition is extended in each cylinder 10, so that the stability of combustion is improved, the torque is improved, and the engine speed can be increased. On the other hand, when the absolute value of ΔNE is less than a predetermined threshold value, the ECU 50 may continue the current control for the different cylinders 10. Then, the ECU 50 advances the ignition timing stepwise for each cylinder 10 for which the ignition retard control has been performed in response to the recovery (increase) of the engine speed, and returns the ignition timing to the original ignition timing.

[0049] As described above, in the ECU 50 that controls the internal combustion engine 1 according to this embodiment, when the engine speed of the internal combustion engine 1 drops after the fuel injection from the injector 14 is stopped, the ignition timing is retarded in the cylinders 10 other than the cylinder 10 in which the fuel injection from the injector 14 is stopped according to the amount of decrease in the engine speed, and the ignition timing is retarded in the next combustion cycle for the cylinder 10 in which the fuel injection is stopped. As a result, the fuel injection time before ignition is extended in all cylinders 10, improving the stability of combustion and improving the torque, thereby making it possible to increase the engine speed. In addition, since the ignition retard control is executed only when the engine speed drops, the effect of cutting the fuel injection amount can be maximized unless the engine speed drops. In addition, even if the engine speed drops, the retard amount is set according to ΔNE, so that the effect of cutting the injection amount can be obtained while compensating for the drop in the engine speed when the injection amount is cut. Furthermore, the ignition retard control increases the amount of fuel injection and the amount of atomization in the cylinder 10 that is the target of the ignition retard control, thereby stabilizing combustion. [Explanation of symbols]

[0050] 1. Internal combustion engine 10 cylinders 11 Combustion chamber 12 Intake valve 13 Exhaust valve 14 Injector 15 Spark plug 21 Intake passage 22 Exhaust passage 23 Throttle valve 31 Piston 32 Connecting rod 33 Crankshaft 34 Flywheel 40 Crank angle sensor 50 ECU 51 Memory 101 1st injection 102 2nd injection 103 3rd injection 111 1st injection 112 The 2nd Jet 113 The 3rd Jet

Claims

1. A control device for a direct injection internal combustion engine in which fuel containing alcohol is directly injected into a cylinder by an injector and ignited by an ignition plug, comprising: A control device for a direct injection internal combustion engine that stops fuel injection from the injector when it detects a rising edge of an ignition signal for the spark plug while fuel is being injected from the injector.

2. 2. A control device for a direct injection internal combustion engine according to claim 1, wherein when a rising edge of the ignition signal for the spark plug is detected while fuel is being injected from the injector, the fuel pressure of the fuel injected from the injector is temporarily increased, and the injection is stopped by blowing off the amount of fuel scheduled to be injected.

3. 2. A control device for a direct injection internal combustion engine according to claim 1, wherein, when the rotation speed of the direct injection internal combustion engine decreases after fuel injection from the injector is stopped, the ignition timing of cylinders other than the cylinder for which fuel injection from the injector is stopped is retarded in accordance with the amount of decrease in the rotation speed, and the ignition timing of the cylinder for which fuel injection is stopped is retarded in the next combustion cycle.

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