JP4178988B2 - Start-up control device for compression ignition internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a start control device that controls fuel injection timing at the start of a compression ignition internal combustion engine.
[0002]
[Prior art]
In the compression ignition internal combustion engine, the fuel injection timing at the start is controlled so as to advance the fuel injection timing to the advance side according to the coolant temperature and the engine speed of the compression ignition internal combustion engine. Thus, the startability is improved by adjusting the ignition timing of the fuel at the start (see, for example, Patent Document 1).
[0003]
However, when such control is performed, the fuel injection timing advances further toward the advance side as the engine speed of the compression ignition internal combustion engine increases at the start. Originally, the fuel injected in the compression ignition internal combustion engine is ignited near the top dead center of the compression stroke and explodes and expands efficiently. As a result, the fuel injection timing is further advanced. As a result, the injected fuel may ignite during the compression stroke. In such a case, since the compression work of the piston in the compression ignition internal combustion engine is hindered, the engine speed of the compression ignition internal combustion engine decreases or stagnates, and there is a possibility that the internal combustion engine cannot be started smoothly.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-103129
[Patent Document 2]
JP-A-8-296477
[0005]
[Problems to be solved by the invention]
In the control of the fuel injection timing at the start of the compression ignition internal combustion engine, in order to smoothly start the internal combustion engine, it is necessary to perform the fuel injection at an appropriate timing. In particular, if the fuel injection timing is advanced too far, the injected fuel will not ignite near the compression top dead center, but will ignite in the middle of the compression stroke. Hinder. Therefore, in the present invention, at the time of starting the compression ignition internal combustion engine, the injection that smoothly starts the compression ignition internal combustion engine by adjusting the fuel injection timing so that the injected fuel is ignited near the compression ignition top dead center. The purpose is to provide a control device.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention focuses on fluctuations in the engine speed during the start-up period of the compression ignition internal combustion engine. That is, in the start-up period of the compression ignition internal combustion engine , So that the ignition timing of the fuel in the compression ignition internal combustion engine is near the top dead center of the compression stroke, At least for engine speed As the rise The fuel injection timing On the advance side A start control device for controlling the compression ignition internal combustion engine during a start period; The fuel injection timing is advanced too far and the fuel is ignited during the compression stroke. An injection timing correction means for correcting the fuel injection timing in the compression ignition internal combustion engine to the retard side based on the amount of change in the engine speed when the engine speed decreases or stagnates; The injection timing correction means increases the correction amount to the retard side of the fuel injection timing in the compression ignition internal combustion engine as the amount of decrease in the engine speed increases. .
[0007]
When starting the compression ignition internal combustion engine, the start control device controls the fuel injection timing based on the engine speed of the compression ignition internal combustion engine in consideration of the time until the injected fuel is ignited. . Specifically, the ignition timing of the injected fuel is secured by advancing the fuel injection timing in accordance with the increase in the engine speed during the start period, and the compression ignition internal combustion engine is started. . Here, the start period is one of the purposes to increase the engine speed of the internal combustion engine to a predetermined engine speed by performing the start control of the compression ignition internal combustion engine as described above. It is a certain period. In starting a compression ignition internal combustion engine, the fuel injection timing may be controlled based on not only the engine speed but also the coolant temperature of the internal combustion engine.
[0008]
Thus, although the fuel injection timing is controlled in the start period, the engine speed of the compression ignition internal combustion engine does not increase, but may decrease or stagnate, and smooth start may not be performed. This is because, as described above, the fuel injection timing is advanced to the advance side so that the injected fuel ignites and explodes in the middle of the compression stroke, not in the vicinity of the compression top dead center. This results in the fact that the compression work of the piston is hindered, and as a result, the average effective pressure of the compression ignition internal combustion engine is lowered, and as a result, the increase in the smooth engine speed is hindered.
[0009]
Therefore, when the engine speed of the compression ignition internal combustion engine does not increase and decreases or stagnates and smooth start is not performed, the fuel injection timing is corrected to the retard side. By correcting in this way, the ignition timing of the fuel resulting from the fuel injection timing that has advanced too far to the advance side can be made near the top dead center of the compression stroke.
[0010]
The amount of correction to the retard side is the amount of change in the engine speed of the compression ignition internal combustion engine, that is, the amount of decrease when the engine speed is decreasing, and the amount of engine speed when it is stagnant. It is determined on the basis that the rise is zero. That is, the large change amount (decrease amount) of the engine speed of the compression ignition internal combustion engine is considered to be because the fuel injection timing is excessively advanced to the advance side, and the retard side of the fuel injection timing there. Is determined based on the amount of change (decrease amount) in the engine speed of the compression ignition internal combustion engine. As a result, it is possible to smoothly increase the engine speed without reducing the average effective pressure of the compression ignition internal combustion engine.
[0011]
Here, when controlling the fuel injection timing based on the engine speed of the compression ignition internal combustion engine, the acquisition of the engine speed is performed based on the engine speed estimated from the operating state of the compression ignition internal combustion engine, etc. And the case where the detection is performed based on the engine speed detected from the detection device or the like.
[0012]
First, when the fuel injection timing is controlled based on the engine speed estimated from the operating state of the compression ignition internal combustion engine, first, based on the time elapsed since the compression ignition internal combustion engine started. presume. Further, in such a case, the decrease in the engine speed is assumed to occur when the operation state of the compression ignition internal combustion engine meets a predetermined condition, so that the fuel injection timing is retarded. May be corrected.
[0013]
Next, a case where the fuel injection timing is controlled based on the engine speed detected from the detection device or the like will be described. The above-described start-up control device for a compression ignition internal combustion engine, further comprising engine speed detection means for detecting the engine speed of the compression ignition internal combustion engine, wherein the injection timing correction means starts the compression ignition internal combustion engine. When the engine speed detected by the engine speed detecting means decreases or stagnates during the period, the fuel injection timing in the compression ignition internal combustion engine is corrected to the retard side based on the amount of change in the engine speed. It is characterized by that.
[0014]
Thus, the fuel injection timing can be controlled more accurately based on the engine speed of the compression ignition internal combustion engine detected by the engine speed detecting means. Then, when the engine speed of the compression ignition internal combustion engine does not increase and decreases or stagnates and smooth start is not performed, the fuel injection timing is corrected to the retarded angle side, so that it proceeds too far to the advanced angle side. The ignition timing of the fuel due to the fuel injection timing can be set near the top dead center of the compression stroke. As a result, it is possible to smoothly increase the engine speed without reducing the average effective pressure of the compression ignition internal combustion engine.
[0015]
Further, as described above, the correction to the retarded side of the fuel injection timing performed when the engine speed of the compression ignition internal combustion engine does not increase, decreases or stagnates and smooth start is not performed, This is based on the number change. For example, the correction is to increase the correction amount to the retard side of the fuel injection timing in the compression ignition internal combustion engine as the amount of decrease in the engine speed increases.
[0016]
As described above, when the fuel injection timing of the compression ignition internal combustion engine is corrected, the fuel is ignited when the amount of decrease in the engine speed is large, that is, at a relatively early time during the compression stroke. When it is considered that the advance to the advance angle side is large, the correction amount of the fuel injection timing by the correction becomes large. On the other hand, when the amount of decrease in the engine speed is small, that is, in the later stage of the compression stroke and earlier than the vicinity of the top dead center of the compression stroke, the advance of the fuel injection timing to the advance side is If it is considered that this is not so large, the correction amount of the fuel injection timing by the correction is changed in accordance with the advance of the fuel injection timing to the advance angle side, so that the correction amount is smaller than the correction amount described above. By such correction, the fuel ignition timing becomes close to the top dead center of the compression stroke, and the average effective pressure of the compression ignition internal combustion engine does not decrease, so that the engine speed can be increased smoothly.
[0017]
Further, in order to solve the above-described problems, attention was paid to fluctuations in the average effective pressure of the compression ignition internal combustion engine during the start-up period of the compression ignition internal combustion engine. That is, at the start of the compression ignition internal combustion engine The fuel ignition timing in the compression ignition internal combustion engine is at least as the engine speed increases so that the fuel ignition timing is near the top dead center of the compression stroke. The fuel injection timing On the advance side A start control device for controlling, the mean effective pressure detecting means for detecting the mean effective pressure of the compression ignition internal combustion engine, and at the start of the compression ignition internal combustion engine The fuel injection timing is advanced to the advance side, and the fuel is ignited in the middle of the compression stroke. When the average effective pressure of the compression ignition internal combustion engine decreases or stagnates, an injection timing correction means for correcting the fuel injection timing in the compression ignition internal combustion engine to the retard side based on the amount of change in the average effective pressure. Preparation The injection timing correction means increases the correction amount to the retard side of the fuel injection timing in the compression ignition internal combustion engine as the amount of decrease in the average effective pressure increases. .
[0018]
The correction of the fuel injection timing described above is performed based on the amount of change in the engine speed when the engine speed decreases or stagnates in the start engine of the compression ignition internal combustion engine. In the apparatus, the fuel injection timing is corrected based on the amount of change in the average effective pressure of the compression ignition internal combustion engine, which is a factor such as a decrease in the engine speed. The average effective pressure of the compression ignition internal combustion engine is detected by an average effective pressure detecting means. Further, the correction of the fuel injection timing is the same as the correction based on the engine speed described above. The average effective pressure of the compression ignition internal combustion engine is derived from the pressure in the combustion chamber obtained by a detection device provided in the combustion chamber of the compression ignition internal combustion engine, or in the operating state of the compression ignition internal combustion engine. May be estimated based on.
[0019]
Therefore, when the average effective pressure of the compression ignition internal combustion engine does not increase and decreases or stagnates and smooth start is not performed, the fuel injection timing is corrected to the retarded side, so that it proceeds too far to the advanced side. The ignition timing of the fuel due to the fuel injection timing can be set near the top dead center of the compression stroke. As a result, it is possible to achieve a smooth start without reducing the average effective pressure of the compression ignition internal combustion engine.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
<First embodiment>
Here, an embodiment of an exhaust emission control device for a compression ignition internal combustion engine according to the present invention will be described based on the drawings. FIG. 1 is a diagram showing a schematic configuration of a compression ignition internal combustion engine to which the present invention is applied and an exhaust purification device thereof, and a schematic configuration of a control system thereof.
[0021]
The compression ignition internal combustion engine 1 includes a fuel injection valve 3 that directly injects fuel into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber 4 that accumulates fuel at a predetermined pressure. The pressure accumulating chamber 4 communicates with a fuel pump 6 via a fuel supply pipe 5. The fuel pump 6 is a pump that operates by using the rotational torque of the output shaft (crankshaft) of the compression ignition internal combustion engine 1 as a drive source. A pump pulley 6 a attached to the input shaft of the fuel pump 6 includes a compression ignition internal combustion engine 1. Is connected to a crank pulley 1a attached to an output shaft (crankshaft) of the first through a belt 7. In the fuel injection system configured as described above, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 transmits the rotational torque transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure according to the pressure.
[0022]
The fuel discharged from the fuel pump 6 is supplied to the pressure accumulating chamber 4 through the fuel supply pipe 5, accumulated at a predetermined pressure in the pressure accumulating chamber 4, and distributed to the fuel injection valves 3 of each cylinder 2. When a drive current is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.
[0023]
Next, an intake branch pipe 8 is connected to the compression ignition internal combustion engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 through an intake port (not shown). Yes. The intake branch pipe 8 is connected to an intake pipe 9. An air flow meter 10 that outputs an electrical signal corresponding to the mass of the intake air flowing through the intake pipe 9 is attached to the intake pipe 9. An intake throttle valve 13 for adjusting the flow rate of the intake air flowing through the intake pipe 9 is provided at a portion of the intake pipe 9 located immediately upstream of the intake branch pipe 8. The intake throttle valve 13 is provided with an intake throttle actuator 14 that is configured by a step motor or the like and that drives the intake throttle valve 13 to open and close.
[0024]
Here, the intake pipe 9 located between the air flow meter 10 and the intake throttle valve 13 is provided with a compressor housing 11a of a centrifugal supercharger (turbocharger) 11 that operates using exhaust energy as a drive source. The intake pipe 9 downstream of the housing 11a is provided with an intercooler 12 for cooling the intake air that has been compressed in the compressor housing 11a and has reached a high temperature. In the intake system configured as described above, intake air flows into the compressor housing 11 a via the intake pipe 9.
[0025]
The intake air flowing into the compressor housing 11a is compressed by the rotation of the compressor wheel built in the compressor housing 11a. The intake air that has been compressed in the compressor housing 11 a and has reached a high temperature is cooled by the intercooler 12, and then the flow rate is adjusted by the intake throttle valve 13 as necessary to flow into the intake branch pipe 8. The intake air that has flowed into the intake branch pipe 8 is distributed to the combustion chambers of the respective cylinders 2 through the respective branch pipes, and is burned using the fuel injected from the fuel injection valves 3 of the respective cylinders 2 as an ignition source.
[0026]
On the other hand, an exhaust branch pipe 17 is connected to the compression ignition internal combustion engine 1, and each branch pipe of the exhaust branch pipe 17 communicates with the combustion chamber of each cylinder 2 via an exhaust port (not shown). The exhaust branch pipe 17 is connected to the exhaust turbine housing 11 b of the centrifugal supercharger 11. The exhaust turbine housing 11b is connected to an exhaust pipe 18, and the exhaust pipe 18 is connected downstream to a muffler (not shown). An exhaust purification catalyst 19 that purifies exhaust exhausted from the compression ignition internal combustion engine 1 is provided in the middle of the exhaust pipe 18. Examples of the exhaust purification catalyst 19 include a storage reduction type NOx catalyst, a particulate filter carrying a storage reduction type NOx catalyst, a selective reduction type NOx catalyst, a three-way catalyst, and the like.
[0027]
Further, an exhaust throttle valve 15 for adjusting the flow rate of the exhaust gas flowing through the exhaust pipe 18 is provided in the exhaust pipe 18 positioned downstream of the exhaust purification catalyst 19. The exhaust throttle valve 15 is provided with an exhaust throttle actuator 16 that is configured by a step motor or the like and that drives the exhaust throttle valve 15 to open and close.
[0028]
In the exhaust system configured as described above, the air-fuel mixture (burned gas) combusted in each cylinder 2 of the compression ignition internal combustion engine 1 is discharged as exhaust to the exhaust branch pipe 17 through the exhaust port, and then the exhaust branch pipe. 17 flows into the exhaust turbine housing 11 b of the centrifugal supercharger 11. The exhaust gas that has flowed into the exhaust turbine housing 11b rotates the turbine wheel that is rotatably supported in the exhaust turbine housing 11b using the energy of the exhaust gas. At that time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 11a described above. Further, the exhaust discharged from the turbine housing 24b flows into the exhaust purification catalyst 19, so that NOx and the like contained in the exhaust are removed. The exhaust gas that has passed through the exhaust purification catalyst 19 is discharged into the atmosphere through the muffler after the flow rate is adjusted by the exhaust throttle valve 15 as necessary.
[0029]
Next, the control system of the compression ignition internal combustion engine 1 will be described. The ECU 50 comprises a digital computer and is connected to each other via a bidirectional bus 51, a CPU (microprocessor) 52, a ROM (read only memory) 53, a RAM (random access memory) 54, an input port 56 and an output port. 57. Further, an A / D converter 55 that digitally converts an analog signal input from the outside of the ECU 50 and inputs the analog signal to the input port 56 is connected to the input port 56.
[0030]
An accelerator opening sensor 20 that outputs a voltage proportional to the depression amount of the accelerator pedal to the ECU 50 is input to the input port 56 via the A / D converter 55. The crank position sensor 21 provided in the compression ignition internal combustion engine 1 generates an output pulse each time the crankshaft rotates 30 °, for example, and this output pulse is input to the input port 56. The CPU 52 integrates the engine rotation speed Ne of the compression ignition internal combustion engine 1 and the engine rotation speed based on the output pulse of the crank position sensor 21 or the like in a vehicle equipped with the compression ignition internal combustion engine 1. The travel distance is calculated.
[0031]
Further, the compression ignition internal combustion engine 1 is provided with a cooling water temperature sensor 22 for detecting the temperature of the cooling water circulating in the compression ignition internal combustion engine 1, and the sensor outputs an output voltage corresponding to the temperature of the cooling water. Is input to the input port 56. Further, the cylinder 2 (the fourth cylinder in the present embodiment, hereinafter referred to as “cylinder 2 # 4”) is provided with an in-cylinder pressure sensor 23 for detecting the in-cylinder pressure in the combustion chamber therein. The sensor inputs an output voltage corresponding to the in-cylinder pressure of the cylinder 2 # 4 to the input port 56. Based on the signal from the in-cylinder pressure sensor 23, the CPU 52 calculates an average effective pressure of the compression ignition internal combustion engine 1 and the like. In addition to this, various signals are input to the input port 56, but are not shown in the present embodiment because they are not important for explanation.
[0032]
The output port 57 is electrically connected to the fuel injection valve 3 of each cylinder 2, and the ECU 50 controls the opening of each fuel injection valve 3 according to the operating state of the compression ignition internal combustion engine 1. Control the injection amount. In addition, various signals are output from the output port 57, but in the present embodiment, they are not shown because they are not important for explanation.
[0033]
Here, the start of the compression ignition internal combustion engine 1 in the present embodiment will be described. The starting of the internal combustion engine means that the mechanical rotation speed is gradually increased from a state where the engine rotation of the compression ignition internal combustion engine 1 is stopped to obtain a predetermined mechanical rotation speed, and a period required for this is called a start period.
[0034]
During the start-up period, fuel is injected in the compression ignition internal combustion engine 1, and the engine speed gradually increases. At this time, the fuel injected from the fuel injection valve 3 into the combustion chamber in the cylinder 2 requires a substantially constant time (hereinafter referred to as “ignition delay time”) from ignition to ignition. Therefore, taking into consideration that the engine speed increases with the passage of time from the start of the start, the fuel injection timing is advanced further in the combustion cycle, and a time corresponding to the ignition delay time is secured, thereby ensuring the cylinder. The fuel injected into the combustion chamber in 2 ignites, burns and explodes near the top dead center of the compression stroke, and the compression ignition internal combustion engine 1 is efficiently started.
[0035]
However, there is a possibility that the engine speed of the compression ignition internal combustion engine 1 does not increase smoothly as the timing of injection from the fuel injection valve 3 advances toward the advance side. This will be described with reference to FIGS. 2 (a) and 2 (b). 2A shows the time transition of the engine speed during the start-up period of the compression ignition internal combustion engine 1, and FIG. 2B shows the time transition of the average effective pressure during the start-up period of the compression ignition internal combustion engine 1, respectively. FIG. 2A represents the engine speed of the compression ignition internal combustion engine 1, and the vertical axis of FIG. 2B represents the average effective pressure of the compression ignition internal combustion engine 1. 2 (a) and 2 (b) indicate the elapsed time from the start of the compression ignition internal combustion engine 1, and the elapsed time corresponds in both figures, and the engine speed at the same elapsed time and It shows the transition of average effective pressure.
[0036]
Here, when the fuel injection timing from the fuel injection valve 3 advances excessively, the ignition timing of the fuel injected as a result does not become near the top dead center of the compression stroke, but in the middle of the compression stroke. There is a case. When the fuel ignites and explodes in the compression stroke before the top dead center of the compression stroke, work that becomes a load is generated on the piston that performs the compression work of the air-fuel mixture in the combustion chamber. Therefore, the average effective pressure of the compression ignition internal combustion engine 1 decreases, and the engine speed that has been increasing during the start-up period decreases or stagnates to obey the average effective pressure, thereby preventing a smooth increase in engine speed. Here, in the period represented by the section B in FIG. 2, a decrease in the engine speed or the like due to the excessive advance of the fuel injection timing occurs. Further, in the period represented by the section A in FIG. 2, the fuel injection timing is appropriately advanced to the advance side, so that the injected fuel is ignited in the vicinity of the top dead center of the compression stroke. The average effective pressure of the ignition internal combustion engine 1 increases, and the engine speed increases smoothly.
[0037]
Therefore, control of the fuel injection timing by the fuel injection valve 3 in order to smoothly increase the engine speed during the start-up period in which the compression ignition internal combustion engine 1 is started will be described with reference to FIG. Here, FIG. 3 is a flowchart showing control of the fuel injection timing during the start-up period of the compression ignition internal combustion engine 1. The start control in FIG. 3 is a control executed by the ECU 50, and includes the injection timing correction means in the start device for the compression ignition internal combustion engine according to the present invention.
[0038]
In S101, the ECU 50 acquires the engine speed Ne of the compression ignition internal combustion engine 1. More specifically, the angular speed of the crankshaft is detected based on the signal from the crank position sensor 21, and the engine speed Ne is obtained therefrom. When the process of S101 ends, the process proceeds to S102.
[0039]
In S102, the ECU 50 acquires the temperature Thw of the cooling water flowing through the compression ignition internal combustion engine 1. This cooling water mainly removes the heat generated in the compression ignition internal combustion engine 1 to remove adverse effects on the operation of the compression ignition internal combustion engine 1 due to heat, but conversely detects the temperature of the cooling water. Thus, it is possible to detect how much the compression ignition internal combustion engine 1 has been warmed up. Specifically, the ECU 50 acquires the coolant temperature based on a signal from the coolant temperature sensor 22. When the process of S102 ends, the process proceeds to S103.
[0040]
In S103, the engine speed fluctuation ΔNe of the engine speed Ne of the compression ignition internal combustion engine 1 is calculated. That is, the difference between the engine speed Ne acquired in S101 and the engine speed Ne already acquired in the previous S101 is calculated as ΔNe. When the process of S103 ends, the process proceeds to S104.
[0041]
In S104, the base injection timing Binj is calculated. The base injection timing Binj is a basic injection timing for injecting fuel from the fuel injection valve 3. In this embodiment, the base injection timing Binj is stored in the ROM 53 in the form of a map shown in FIG. By accessing, the base injection timing Binj is calculated. The map shown in FIG. 4 is a two-dimensional map that uses the temperature Thw of the cooling water and the engine speed Ne as parameters, and accesses the map based on the values acquired in S102 and S101, respectively, and the corresponding base injection timing. Binj is calculated. As described above, when the compression ignition internal combustion engine 1 is started, the fuel injection timing is advanced to the advance side as the engine speed increases. Therefore, for example, when the engine speed is 50 and 100, the value of the base injection timing Binj in FIG. 4 is the value of the fuel injection timing advanced to the advance side when the engine speed is 100. It has become. Note that the values shown in FIG. 4 are merely examples, and the cooling water temperature Thw and the engine speed Ne that are not shown are appropriately created. When the process of S104 ends, the process proceeds to S105.
[0042]
In S105, it is determined whether or not the value of ΔNe calculated in S103 is 0 or less. If the value of ΔNe is 0 or less, it means that the engine speed has decreased or stagnated during the start-up period, and the engine speed has not been increased smoothly. If the value of ΔNe exceeds 0, It means that the engine speed is smooth. That is, in S105, whether the engine speed of the compression ignition internal combustion engine 1 that has been started is changing as shown in the period A shown in FIG. This is done based on the value of the engine speed fluctuation ΔNe. If the value of ΔNe exceeds 0, that is, if the engine speed is increasing smoothly, the process proceeds to S106. On the other hand, if the value of ΔNe is 0 or less, that is, if the engine speed has not increased smoothly, the process proceeds to S107.
[0043]
In S106, the value of the corrected injection timing ΔINJ is set to zero. The corrected injection timing ΔINJ is a value for correcting the fuel injection timing of the base injection timing Binj calculated in S104. In S106, since it is determined in S105 that the value of the engine speed fluctuation ΔNe exceeds 0, the engine speed of the compression internal combustion engine 1 is smoothly increased. Accordingly, since it is considered unnecessary to correct the base fuel injection timing Binj, 0 is set to the correction injection timing ΔINJ which is the correction value. When the process of S106 ends, the process proceeds to S108.
[0044]
In S107, the corrected injection timing ΔINJ is calculated. Here, the calculation of the corrected injection timing ΔINJ will be described with reference to FIG. FIG. 5 is a diagram showing a function for calculating the corrected injection timing ΔINJ including the corrected injection timing ΔINJ set in S106 described above. The horizontal axis in FIG. 5 is the engine speed fluctuation ΔNE calculated in S103, and the vertical axis in FIG. 5 is the corrected injection timing ΔINJ to be calculated. Therefore, the function shown in FIG. 5 is a function for calculating the corrected injection timing ΔINJ from the value of the engine speed fluctuation ΔNe.
[0045]
Here, in S107, since it is determined in S105 that the engine speed fluctuation ΔNe is 0 or less, the function for calculating the corrected injection timing ΔINJ is a function represented by a straight line L1. In the function represented by the straight line L1 in FIG. 5, the value of the injection correction timing ΔINJ is a negative value as the engine speed fluctuation ΔNe is a value of 0 or less and the absolute value is large. growing. Note that a negative value of ΔINJ means a correction value for shifting the fuel injection timing to the retarded angle side. The function represented by the straight line L2 is a function that means that the value of the corrected injection timing ΔINJ is set to 0 in S106. When the process of S107 ends, the process proceeds to S108.
[0046]
In S108, the final fuel injection timing INJ is calculated. Here, the final fuel injection timing INJ is calculated as the sum of the base injection timing Binj calculated in S104 and the corrected injection timing ΔINJ set and calculated in S106 or S107. That is, the value of the base injection timing Binj, which is the basic fuel injection timing, is corrected based on the engine speed fluctuation ΔNe of the compression ignition internal combustion engine 1. For example, when the value of the engine speed fluctuation ΔNe is 0 or less, a negative value is calculated for the corrected injection timing ΔINJ in S107, and as a result, the final fuel injection timing INJ is retarded from the base injection timing Binj. The value moved to.
[0047]
Further, in the function represented by the straight line L1 in FIG. 5 used in calculating the corrected injection timing ΔINJ in S107, the engine speed fluctuation ΔNe is a negative value and the absolute value thereof is larger, that is, the compression is performed. As the amount of decrease in the engine speed of the ignition internal combustion engine 1 increases, the value of the correction injection timing ΔINJ becomes a correction amount that shifts the fuel injection timing to the retard side. This is because the amount of decrease in the engine speed Ne is large, because the injected fuel ignites and explodes at a relatively early time during the compression stroke, and the average effective pressure of the compression ignition internal combustion engine 1 decreases. Depends on being relatively large. Accordingly, when the engine speed of the compression ignition internal combustion engine 1 is greatly reduced, the ignition timing of the injected fuel is made near the compression top dead center by correcting the fuel injection timing to a larger retard side. is there. When the process of S108 ends, the process proceeds to S109.
[0048]
In S109, fuel is injected from the fuel injection valve 3 in accordance with the final fuel injection timing INJ calculated in S108. When the process of S109 ends, the process proceeds to S110.
[0049]
In S110, it is determined whether or not the engine speed Ne exceeds a predetermined engine speed Ne1. Here, the predetermined engine speed Ne1 refers to an engine speed that is a judgment for ending the start control in the compression ignition internal combustion engine 1. Accordingly, when the engine speed Ne exceeds the predetermined engine speed Ne1, the process proceeds to S111 and this control is terminated. When the engine speed Ne does not exceed the predetermined engine speed, the start control of the compression ignition internal combustion engine 1 is continued, and the processes after S101 are performed again.
[0050]
In this embodiment, at the start of the compression ignition internal combustion engine, the fuel injection timing is advanced toward the advance side as the engine speed increases, so that the ignition delay time of the injected fuel is secured, and the ignition timing of the fuel is The engine speed is increased by being near the top dead center of the compression stroke. At that time, if the engine speed decreases or stagnates, the injected fuel is dead in the compression stroke by correcting the fuel injection timing to the retard side based on the amount of change in the engine speed. By igniting near the point, the compression ignition internal combustion engine can be started smoothly.
[0051]
Further, in S104 of the start control flow chart shown in FIG. 3 of the present embodiment, the cooling water temperature Thw and the engine speed Ne are used as parameters in calculating the base injection timing Binj, which is the basic fuel injection timing. A two-dimensional map is accessed. The map may be a one-dimensional map that parameters at least the engine speed Ne, and is a multi-dimensional map that uses elements other than the temperature of the cooling water as parameters. Also good.
[0052]
Further, in S107 of the flowchart of the start control shown in FIG. 3 of the present embodiment, the corrected injection timing ΔINJ is calculated according to the function indicated by the straight line L1 in FIG. 5, but the function for calculating the corrected injection timing ΔINJ is a straight line. The correction injection timing ΔINJ may be calculated by an arbitrary function according to the characteristics of the compression ignition internal combustion engine 1 without being limited to L1.
[0053]
In this embodiment, the engine speed of the compression ignition internal combustion engine 1 is calculated based on a signal detected by the crank position sensor 21 and is used in the start control shown in FIG. It is also possible to estimate the engine speed from the operating state of 1 and other engine elements and perform the start control shown in FIG. 3 based on the estimated engine speed. For example, the engine speed is estimated using the elapsed time from the start of the compression ignition internal combustion engine 1 as a parameter. In such a case, fluctuations in the engine speed of the compression ignition internal combustion engine 1, in particular, reduction or stagnation of the engine speed, can be estimated. For example, the output of the engine element connected to the crankshaft can be estimated. From the above, it is estimated that the engine speed of the compression ignition internal combustion engine 1 is not increasing smoothly, and the fuel injection timing is corrected to the retard side based on the estimated amount of change in the engine speed. The correction amount to the retard side of the fuel injection timing is determined based on the estimated engine speed fluctuation.
[0054]
<Second embodiment>
Here, another embodiment of the start control of the compression ignition internal combustion engine 1 will be described with reference to FIG. FIG. 6 is a flowchart showing control of the fuel injection timing during the start-up period of the compression ignition internal combustion engine 1. The start control in FIG. 6 is a control executed by the ECU 50, and includes the injection timing correction means in the start device for the compression ignition internal combustion engine according to the present invention. The start control in this embodiment will be described below. In the flowchart shown in FIG. 6, the same processes as those in the flowchart of the start control shown in FIG. 3 are denoted by the same reference numerals as those in FIG.
[0055]
In the present embodiment, when the process of S102 ends, the process proceeds to S201. In S201, the average effective pressure Mep of the compression ignition internal combustion engine 1 is acquired. Specifically, the ECU 50 calculates the pressure based on the pressure in the combustion chamber in the cylinder 2 # 4 detected by the cylinder pressure sensor 23 provided in the cylinder 2 # 4. It may be calculated from the engine output of the compression ignition internal combustion engine 1. When the process of S201 ends, the process proceeds to S202.
[0056]
In S202, the average effective pressure fluctuation ΔMep of the average effective pressure Mep of the compression ignition internal combustion engine 1 is calculated. That is, the difference between the average effective pressure Mep acquired in S201 and the average effective pressure Mep already acquired in the previous S201 is calculated as ΔMep. When the process of S202 ends, the process proceeds to S104. The processing in S104 is as described above. Then, when the process of S104 ends, the process proceeds to S203 in the present embodiment.
[0057]
In S203, it is determined whether or not the value of ΔMep calculated in S202 is 0 or less. If the value of ΔMep is 0 or less, it means that the engine speed has decreased or stagnated during the start-up period, and the engine speed has not been increased smoothly. If the value of ΔMep exceeds 0, It means that the engine speed is smooth. That is, in S203, whether the engine speed of the compression ignition internal combustion engine 1 that has been started is changing as shown in the period A shown in FIG. Is determined based on the value of the average effective pressure fluctuation ΔMep. If the value of ΔMep exceeds 0, that is, if the engine speed is increasing smoothly, the process proceeds to S204. On the other hand, if the value of ΔMep is 0 or less, that is, if the engine speed has not risen smoothly, the process proceeds to S205.
[0058]
The processing in S204 and the processing in S205 are essentially the same as the processing in S106 and the processing in S107 shown in FIG. 3, respectively, and the average effective pressure fluctuation ΔMep calculated in S202 is calculated when the corrected injection timing ΔINJ is calculated. The difference is based on the value. Therefore, the function for calculating the corrected injection timing ΔINJ can be represented by a function with the horizontal axis representing the average effective pressure fluctuation ΔMep instead of the function whose horizontal axis is represented by the engine speed fluctuation ΔNe in FIG. When the process of S204 or S205 is completed, the process proceeds to S108. The processing after S108 is as described in FIG.
[0059]
In this embodiment, when starting the compression ignition internal combustion engine, if the average effective pressure of the compression ignition internal combustion engine decreases or stagnates, the fuel injection timing is shifted to the retard side based on the amount of change in the average effective pressure. By correcting the above, the injected fuel is ignited in the vicinity of the top dead center of the compression stroke, and the compression ignition internal combustion engine can be started smoothly.
[0060]
【The invention's effect】
When the compression ignition internal combustion engine starts, if the engine speed does not increase smoothly and the engine speed decreases or stagnates, the fuel injection timing is retarded according to the fluctuation of the engine speed. As a result of the correction, the injected fuel is ignited in the vicinity of the top dead center of the compression stroke, and the compression ignition internal combustion engine can be started smoothly.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine having an exhaust gas purification apparatus for an internal combustion engine according to the present embodiment and a control system thereof.
FIG. 2 is a diagram showing a time transition of an engine speed during a start period and a time transition of an average effective pressure of a compression ignition internal combustion engine in a start ignition control apparatus for a compression ignition internal combustion engine.
FIG. 3 is a flowchart showing start control performed during a start period in the start control device for a compression ignition internal combustion engine according to the present embodiment.
FIG. 4 is a diagram showing a map for storing base injection timing in the start-up control apparatus for a compression ignition internal combustion engine according to the present embodiment.
FIG. 5 is a diagram showing a function for determining a correction amount of fuel injection timing in the start-up control device for a compression ignition internal combustion engine according to the present embodiment.
FIG. 6 is a second flowchart showing the start control performed during the start period in the start control device for the compression ignition internal combustion engine according to the present embodiment.
[Explanation of symbols]
1 ... Compression ignition internal combustion engine
3. Fuel injection valve
21 ... Crank position sensor
23 ... In-cylinder pressure sensor
50 .... ECU

Claims (2)

In the starting period of a compression ignition internal combustion engine, the ignition timing of fuel in said compression ignition internal combustion engine so that the vicinity of top dead center compression stroke, to control the injection timing of the fuel to the advance side in accordance with increase of at least the engine speed A start control device,
Wherein the start-up period of a compression ignition internal combustion engine, when the injection timing of the fuel proceeds too fuel to the advance side decreases or stagnant agencies rotational speed due to ignition during the compression stroke, the engine An injection timing correction means for correcting the fuel injection timing in the compression ignition internal combustion engine to the retard side based on the amount of change in the rotational speed ;
In the compression ignition internal combustion engine, the injection timing correction means increases the correction amount to the retard side of the fuel injection timing in the compression ignition internal combustion engine as the amount of decrease in the engine speed increases. Start control device. At the start of a compression ignition internal combustion engine, the ignition timing of fuel in said compression ignition internal combustion engine so that the vicinity of top dead center compression stroke, to control the injection timing of the fuel to the advance side in accordance with increase of at least the engine speed A start control device,
Mean effective pressure detecting means for detecting an average effective pressure of the compression ignition internal combustion engine;
At the start of the compression ignition internal combustion engine, the injection timing of the fuel advances proceeds too fuel to the corner side mean effective pressure is reduced or stagnation in the way due to ignite the compression ignition internal combustion engine of the compression stroke The injection timing correction means for correcting the fuel injection timing in the compression ignition internal combustion engine to the retard side based on the amount of change in the average effective pressure ,
In the compression ignition internal combustion engine, the injection timing correction means increases the correction amount to the retard side of the fuel injection timing in the compression ignition internal combustion engine as the amount of decrease in the average effective pressure increases. Start control device.

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