JP2005076561A - Fuel injection device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device for an internal combustion engine for accurately controlling an injection amount to be a target value. <P>SOLUTION: The fuel injection device comprises a common-rail 13 and a fuel injection valve 3 connected to the common-rail 13. When pilot injection is started, injection pressure is pulsated. At this time, the injection amount of main injection is changed in a certain change pattern. The amount of pilot injection, when increased or reduced, has a change pattern similar thereto except that its time axis is simply lined off. The change amount of the injection amount of the main injection is found by using such characteristics. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel injection device for an internal combustion engine.

2. Description of the Related Art An internal combustion engine in which a fuel injection valve is connected to a common rail via a high-pressure line and performs a plurality of fuel injections in one cycle, for example, two pilot injections and subsequent main injections is known ( For example, Patent Document 1). In this internal combustion engine, the main injection amount is calculated from the map, and the injection amount and injection timing of the first and second pilot injections are calculated from the map based on the main injection amount and the engine speed.
JP 2000-18074 A

However, when such a common rail is used, when fuel injection, for example, pilot injection is performed, the pressure wave generated in the nozzle chamber of the fuel injection valve at that time propagates in the high pressure line and reaches the common rail. Is reflected by the common rail, and this time advances in the high-pressure line toward the nozzle chamber, causing intense pulsation of the fuel pressure in the nozzle chamber. If main injection is performed at this time, the injection amount of main injection will fluctuate | deviate widely and will shift | deviate from a regular amount to a large.
However, in this case, the main injection amount fluctuates with a certain variation pattern according to the pilot injection amount, and when the pilot injection amount is not so large, each variation pattern is merely shifted in time. It turns out that there is. Therefore, if this is utilized and the main injection amount is corrected by a variation amount that varies according to the variation pattern, the main injection amount can always be maintained at the target value.

  That is, according to the present invention, a common rail and a fuel injection valve connected to the common rail are provided, and at least two fuel injections of the previous injection and the subsequent injection are performed from each fuel injection valve during one cycle of the engine. In the injection control device for an internal combustion engine in which the amount of variation of the injection amount of the subsequent injection with respect to the target value changes according to the interval time from the previous injection to the subsequent injection being performed, the previous injection is performed in advance. Storage means for storing the reference fluctuation amount of the subsequent injection that changes along the reference fluctuation pattern with an increase in the interval time at the predetermined reference injection amount, and when the previous injection is not the reference injection amount Calculating means for estimating a deviation amount between a fluctuation pattern of a fluctuation amount of the subsequent injection and a reference fluctuation pattern, and calculating a fluctuation amount of the subsequent injection from the deviation amount, the reference fluctuation amount, and the interval time; And a control means for controlling the target value injection amount using the fluctuation amount calculated by the means.

  Even if the previous injection amount changes, the total injection amount can be accurately controlled to the target value by a simple method.

  Referring to FIG. 1, 1 is a compression ignition type internal combustion engine body, 2 is a combustion chamber of each cylinder, 3 is a fuel injection valve for injecting fuel into each combustion chamber 2, 4 is an intake manifold, 5 is exhaust Each shows a manifold. The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 through the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 8. A throttle valve 9 driven by a step motor is disposed in the intake duct 6. On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7.

  The exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 10, and an electronically controlled EGR control valve 11 is disposed in the EGR passage 10. On the other hand, each fuel injection valve 3 is connected to a common rail 13 through a fuel supply pipe 12. Fuel is supplied from a fuel tank 15 into the common rail 13 by an electronically controlled fuel pump 14 with variable discharge amount, and the fuel supplied into the common rail 13 is supplied to the fuel injection valve 3 through each fuel supply pipe 12. Is done. A fuel pressure sensor 16 for detecting the fuel pressure in the common rail 13 is attached to the common rail 13, and the fuel pump 14 is configured so that the fuel pressure in the common rail 16 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 16. The discharge amount is controlled.

  The electronic control unit 20 comprises a digital computer and is connected to each other by a bidirectional bus 21. A ROM (read only memory) 22, a RAM (random access memory) 23, a CPU (microprocessor) 24, an input port 25 and an output port 26 are connected. It comprises. The output signal of the fuel pressure sensor 16 is input to the input port 25 via the corresponding AD converter 27. On the other hand, a load sensor 18 that generates an output voltage proportional to the depression amount L of the accelerator pedal 17 is connected to the accelerator pedal 17, and the output voltage of the load sensor 18 is input to the input port 25 via the corresponding AD converter 27. Is done. Further, the input port 25 is connected to a crank angle sensor 19 that generates an output pulse every time the crankshaft rotates, for example, 15 °. On the other hand, the output port 26 is connected to the fuel injection valve 3, the throttle valve 9 driving step motor, the EGR control valve 11, and the fuel pump 14 via corresponding drive circuits 28.

  FIG. 2 shows an enlarged view of the fuel injection valve 3. As shown in FIG. 2, the fuel injection valve 3 includes a needle valve 31 that can be seated on a valve seat 30, a sac chamber 32 formed around the tip of the needle valve 31, and the sac chamber 32 into the combustion chamber 2. An extending nozzle hole 33 and a nozzle chamber 34 formed around the needle valve 31 are provided. The nozzle chamber 34 is connected to the common rail 13 through a high-pressure fuel supply passage extending in the main body of the fuel injection valve 3 and the fuel supply pipe 12, a so-called high-pressure line 35, and the high-pressure fuel in the common rail 13 is this high-pressure fuel. It is supplied into the nozzle chamber 34 via the line 35.

  A pressure control chamber 36 is formed in the fuel injection valve 3 so as to face the back surface of the needle valve 31. A compression spring 37 that presses the needle valve 31 toward the valve seat 30 is formed in the pressure control chamber 36. Has been placed. The pressure control chamber 36 is connected on the one hand to the middle of the high-pressure line 35 via an inlet side throttle 38, and on the other hand, a fuel overflow port 41 that is controlled to open and close by an overflow control valve 40 via an outlet side throttle 39. It is connected to. High pressure fuel is always supplied to the pressure control chamber 36 through the throttle 38, and therefore the pressure control chamber 36 is filled with fuel.

  When the fuel overflow port 41 is closed by the overflow control valve 40, as shown in FIG. 2, the needle valve 31 is seated on the valve seat 30, so that the fuel injection is stopped. At this time, the inside of the nozzle chamber 34 and the inside of the pressure control chamber 36 have the same fuel pressure. When the overflow control valve 40 is opened, that is, when the fuel overflow port 41 is opened, the high-pressure fuel in the pressure control chamber 36 flows out from the fuel overflow port 41 through the throttle 39, and thus in the pressure control chamber 36. The pressure of gradually decreases. When the pressure in the pressure control chamber 36 decreases, the needle valve 31 rises and fuel injection is started from the injection hole 33.

  That is, a throttle 39 is provided between the pressure control chamber 36 and the fuel overflow port 41, and after a while after the overflow control valve 40 is opened due to other delay elements, fuel injection is performed. Be started. Next, when the overflow control valve 40 is closed, that is, when the fuel overflow port 41 is closed, the pressure in the pressure control chamber 36 is gradually increased by the fuel supplied into the pressure control chamber 36 through the throttle 38. After a while after the overflow control valve 40 is closed, the fuel injection is stopped.

  In the present invention, at least two fuel injections are performed from each fuel injection valve 3 during the engine cycle, that is, the previous injection and the subsequent injection. FIG. 3 shows two typical fuel injection methods. FIG. 3A shows a case where the pilot injection P is performed before the main injection M. In this case, the pilot injection P is the previous injection, and the main injection M is the subsequent injection.

On the other hand, FIG. 3B shows a case where a plurality of pilot injections P ₁ and P ₂ are performed before the main injection M, and a plurality of post injections P ₃ and P ₄ are performed after the main injection M. ing. In this case, if the pilot injection P ₂ is the subsequent injection, the pilot injection P ₁ is the previous injection, and if the main injection M is the subsequent injection, the pilot injections P ₁ and P ₂ are the previous injections and the post injection P _3. Is the subsequent injection, the pilot injections P ₁ and P ₂ and the main injection M are the previous injections.

  In the following, the present invention will be described with reference to an example in which pilot injection P is performed before main injection M as shown in FIG.

  In the embodiment of the present invention, the target total injection amount QT is previously stored in the ROM 22 in the form of a map as a function of the depression amount of the accelerator pedal 17, that is, the accelerator opening L and the engine speed N, as shown in FIG. Is stored within. Further, the target main injection amount QM is stored in advance in the ROM 22 in the form of a map as a function of the total injection amount QT and the engine speed N as shown in FIG. On the other hand, the target pilot injection amount QP is obtained by subtracting the main injection amount QM from the total injection amount QT.

  The injection start timing θM of the main injection M is stored in advance in the ROM 22 in the form of a map as a function of the total injection amount QT and the engine speed N as shown in FIG. Further, a time interval from the previous injection to the subsequent injection, that is, an interval time is set in advance. In the embodiment according to the present invention, the interval time TI from the start of the pilot injection P to the start of the main injection M is a function of the total injection amount QT and the engine speed N as shown in FIG. Is stored in advance in the ROM 22 in the form of a map, and the injection start timing θP of the pilot injection P is calculated from the injection start timing θM of the main injection M and the interval time TI.

  In the embodiment according to the present invention, the target rail pressure in the common rail 13 is set in advance. In general, the target rail pressure increases as the total injection amount QT increases.

  Now, when the needle valve 31 is opened in FIG. 2 and fuel injection is started, the pressure in the nozzle chamber 34 rapidly decreases. Thus, when the pressure in the nozzle chamber 34 rapidly decreases, a pressure wave is generated, and this pressure wave propagates in the high-pressure line 35 toward the common rail 13. This pressure wave is then reflected at the open end of the high-pressure line 35 into the common rail 13, this time this pressure wave is in the high-pressure line 35 with the pressure reversed relative to the average pressure, ie in the form of a high-pressure pressure wave. To the nozzle chamber 34, and a high pressure is temporarily generated in the nozzle chamber 34. For example, if pilot injection is performed, a high pressure is temporarily generated in the nozzle chamber 34 by a reflected wave on the common rail 13 for a while after that.

  On the other hand, when the needle valve 31 is closed, the flow of fuel is suddenly blocked, so that the pressure in the nozzle chamber 34 temporarily rises and a pressure wave is generated. This pressure wave also propagates in the high-pressure line 35, is reflected by the common rail 13, and returns to the nozzle chamber 34.

  Further, the pressure wave propagating into the nozzle chamber 34 is also generated by the opening / closing operation of the overflow control valve 40. That is, if the overflow control valve 40 is opened, the pressure of the fuel overflow port 41 is suddenly reduced, so that a pressure wave is generated. If the overflow control valve 40 is closed, the pressure of the fuel overflow port 41 is increased. A pressure wave is generated due to the rapid rise. These pressure waves propagate through the pair of throttles 39 and 38 into the nozzle chamber 34 to increase or decrease the pressure in the nozzle chamber 34. At the same time, the pressure waves are reflected in the nozzle chamber 34 and reflected to the common rail 13 or Propagates toward the fuel overflow port 41.

  Thus, when the pilot injection P is performed, the fuel pressure in the nozzle chamber 34 pulsates due to the pressure wave generated by the opening / closing operation of the needle valve 31 and the opening / closing operation of the overflow control valve 40. Next, the main injection M is performed when the fuel pressure in the nozzle chamber 34 is pulsating as described above. However, if the main injection M is performed when the fuel pressure in the nozzle chamber 34 is pulsating as described above, the injection amount increases when the fuel pressure in the nozzle chamber 34 increases, and the fuel in the nozzle chamber 34 increases. When the pressure decreases, the injection amount decreases, so the injection amount of the main injection M varies.

  Next, the fluctuation amount of the injection amount of the main injection M will be described with reference to FIGS. 6A shows the injection command pulse of the pilot injection P, FIG. 6B shows the lift amount of the needle valve 31, and FIG. 6C shows the fuel pressure in the nozzle chamber 34. 7A and 7B, the horizontal axis Ti represents the interval time from when the pilot injection P is started until the main injection M is started, and the vertical axis dQ is the injection of the main injection M. It represents the amount of change with respect to the target value.

6 and 7, the thick line indicates the previous injection, that is, when the injection amount of the pilot injection P is the reference injection amount. In the embodiment according to the present invention, this reference injection amount is 2 (mm ³ ). Referring to the case indicated by the thick line in FIG. 6, the needle valve 31 starts to open after a delay time τ has elapsed since the injection command pulse of the pilot injection P was issued. When fuel injection is started after the needle valve 31 starts to open, the fuel pressure in the nozzle chamber 34 gradually decreases. Next, after a while after the injection command pulse falls, the lift amount of the needle valve 31 becomes maximum, and then the needle valve 31 starts to close. On the other hand, the fuel pressure in the nozzle chamber 34 is minimized at the same time as the lift amount of the needle valve 31 is maximized, and then the fuel pressure in the nozzle chamber 34 starts to rise. Next, when the lift amount of the needle valve 31 becomes zero, the fuel pressure in the nozzle chamber 34 returns to the original fuel pressure.

  On the other hand, when the needle valve 31 is opened and the fuel pressure in the nozzle chamber 34 temporarily decreases as indicated by R, a pressure wave is generated thereby, and this pressure wave is reflected by the common rail 13 and becomes the fuel pressure. On the other hand, the pressure wave is reversed and returns to the nozzle chamber 34. As a result, a pressure pulsation as indicated by S occurs in the nozzle chamber 34. T1 in FIG. 6C indicates a period from when the fuel pressure drop R in the nozzle chamber 34 occurs when the needle valve 31 is opened to when the pressure pulsation S is generated. Since the pressure wave attenuates when reflected, the pressure pulsation S has a smaller fluctuation amount than the fuel pressure drop R as shown in FIG. 6C, but the fluctuation pattern of the pressure pulsation S is the fluctuation of the fuel pressure drop R. It has almost the same shape as the pattern.

  FIG. 6C schematically shows the fluctuation of the fuel pressure in the nozzle chamber 34, and the actual fluctuation of the fuel pressure in the nozzle chamber 34 is more complicated. On the other hand, the thick line in FIG. 7 represents the reference fluctuation amount dQ with respect to the target value of the injection amount of the main injection M when the pilot injection P is the reference injection amount. The fluctuation pattern of the reference fluctuation amount dQ at this time is the reference fluctuation pattern. Called. If the reference fluctuation amount is obtained and stored in advance, when the pilot injection P is the reference injection amount, the fluctuation amount dQ corresponding to each interval time Ti can be obtained from the reference fluctuation amount that changes with this reference fluctuation pattern.

  Now, as shown by the broken line X in FIG. 6A, when the time length of the injection command pulse is increased by ΔτX to increase the pilot injection amount, the lift amount of the needle valve 31 becomes maximum accordingly. Is delayed by ΔtX, and at the same time the fuel pressure in the nozzle chamber 34 is minimized by ΔtX. At this time, the peak occurrence time of the pressure pulsation, which is a reflected wave on the common rail 13, is also delayed by ΔtX, and the pressure pulsation cycle T2 is the same as the cycle T1 when the pilot injection is the basic injection amount. Accordingly, at this time, as indicated by a broken line X in FIG. 7A, the fluctuation pattern of the fluctuation amount dQ is shifted from the reference fluctuation pattern.

  On the other hand, when the time length of the injection command pulse is shortened by ΔτY to decrease the pilot injection amount as indicated by the chain line Y in FIG. 6A, the lift amount of the needle valve 31 is maximized accordingly. Is accelerated by ΔtY, and at the same time, the fuel pressure in the nozzle chamber 34 is minimized by ΔtY. At this time, the peak occurrence time of the pressure pulsation, which is a reflected wave on the common rail 13, is also advanced by ΔtY, and the period of the pressure pulsation is the same as the period T1 when the pilot injection is the basic injection amount. Therefore, at this time, as indicated by a broken line Y in FIG. 7B, the fluctuation pattern of the fluctuation amount dQ is shifted from the reference fluctuation pattern.

  Here, the reference fluctuation amount dQ changing along the reference fluctuation pattern is obtained in advance by experiments, and the fluctuation pattern of the fluctuation amount dQ indicated by the broken lines X and Y in FIGS. 7A and 7B and the thick line. If the deviation amount from the indicated reference fluctuation pattern is known, the fluctuation amount dQ of the main injection M when the pilot injection is not the reference injection amount can be calculated from the deviation amount and the reference fluctuation amount as indicated by broken lines X and Y. It will be possible.

  That is, in the present invention, when using a general expression, the reference fluctuation amount of the subsequent injection that changes along the reference fluctuation pattern as the interval time Ti increases when the previous injection is a predetermined reference injection quantity Is stored, and when the previous injection is not the reference injection amount, the deviation amount between the fluctuation pattern of the subsequent injection and the reference fluctuation pattern is estimated, and the deviation amount, the reference fluctuation amount, and the interval time are estimated. The variation amount of the subsequent injection is calculated, and the injection amount is controlled to the target value using the calculated variation amount. In this case, it is only necessary to store the reference fluctuation amount, and there is an advantage that the memory capacity can be reduced because it is not necessary to store the fluctuation amounts in various fluctuation patterns other than the reference fluctuation pattern.

  When the pilot injection is not the reference injection amount, the deviation amount between the fluctuation pattern of the fluctuation amount dQ and the reference fluctuation pattern are roughly divided into two deviation amounts. The first deviation amount is the deviation amount in the time axis direction of the interval time Ti, that is, the fluctuation time difference between the fluctuation pattern when the pilot injection is not the reference injection quantity and the reference fluctuation pattern. 7A and 7B, the second deviation amount is the deviation amount in the vertical axis direction, that is, the fluctuation amount between the fluctuation pattern when the pilot injection at the same interval time Ti is not the reference injection quantity and the reference fluctuation pattern. It is a difference.

  First, the shift amount in the time axis direction of the interval time Ti between the variation patterns, that is, the variation time difference will be described. This variation time difference is indicated by ΔtXX in FIG. 7A and indicated by ΔtYY in FIG. 7B.

  In FIG. 7A, the fluctuation amount dQ on the fluctuation pattern X in a certain interval time TiX is the reference fluctuation in the corrected interval time (TiX−ΔtXX) obtained by subtracting the fluctuation time difference ΔtXX from this certain interval time TiX. It matches the reference fluctuation amount dQ on the pattern. That is, when the fluctuation pattern X is delayed by ΔtXX with respect to the reference fluctuation pattern, if this fluctuation time difference ΔtXX is known, the correction interval time (TiX) is obtained by subtracting the fluctuation time difference ΔtXX from the interval time TiX determined from the operating state. -ΔtXX) is obtained, and the reference fluctuation amount corresponding to the correction interval time (TiX-ΔtXX) is the obtained fluctuation amount.

  On the other hand, the fluctuation amount dQ on the fluctuation pattern Y in a certain interval time TiY in FIG. 7B is the reference fluctuation in the corrected interval time (TiY + ΔtYY) obtained by adding the fluctuation time difference ΔtYY to this certain interval time TiX. It matches the reference fluctuation amount dQ on the pattern. That is, when the variation pattern Y is preceded by ΔtYY with respect to the reference variation pattern, if the variation time difference ΔtYY is known, the modified interval time ( TiY + ΔtYY) is obtained, and the reference fluctuation amount corresponding to the correction interval time (TiY + ΔtYY) is the obtained fluctuation amount.

  As described above, in the present invention, the shift amount between the fluctuation patterns, in this embodiment, the fluctuation time differences ΔtXX and ΔtYY are estimated. Next, various embodiments for estimating the fluctuation time differences ΔtXX and ΔtYY will be described.

  As shown in FIG. 6, when the time when the lift amount of the needle valve 31 is maximized is delayed by ΔtX, the variation pattern is delayed by ΔtXX with respect to the reference variation pattern, and the lift amount of the needle valve 31 is maximized. Is advanced by ΔtY, the fluctuation pattern precedes the reference fluctuation pattern by ΔtYY. Therefore, it is estimated that the shift time ΔtX, ΔtY at the time when the lift amount of the needle valve 31 is maximum is equal to the variation time difference ΔtXX, ΔtYY.

  Therefore, in one embodiment according to the present invention, the time when the lift amount of the needle valve 31 of the fuel injection valve 3 becomes maximum when the previous injection is performed with the reference injection amount is stored as the reference time. The timing when the lift amount of the needle valve 31 is maximum when the injection is not the reference injection amount is detected, and the difference between this timing and the reference timing is set as the fluctuation time differences ΔtXX and ΔtYY.

  Further, as shown in FIG. 6, when the time when the fuel pressure in the nozzle chamber 34 becomes minimum is delayed by ΔtX, the fluctuation pattern is delayed by ΔtXX with respect to the reference fluctuation pattern, and the fuel pressure in the nozzle chamber 34 is changed. When the minimum time is advanced by ΔtY, the variation pattern precedes the reference variation pattern by ΔtYY. Accordingly, it is estimated that the time difference ΔtX, ΔtY at which the fuel pressure in the nozzle chamber 34 becomes minimum is equal to the variation time difference ΔtXX, ΔtYY.

  Therefore, in one embodiment according to the present invention, the time at which the fuel pressure in the nozzle chamber 34 of the fuel injection valve 3 becomes minimum when the previous injection is performed with the reference injection amount is stored as the reference time. When the fuel injection in the nozzle chamber 34 is not the reference injection amount, the timing at which the fuel pressure in the nozzle chamber 34 becomes minimum is detected, and the difference between this timing and the reference timing is set as the variation time differences ΔtXX and ΔtYY.

Further, as shown in FIG. 6, when the time length of the drive command pulse is increased by ΔτX time, the fluctuation pattern is delayed by ΔtXX with respect to the reference fluctuation pattern, and the time length of the drive command pulse is ΔτY time. If it is made shorter, the fluctuation pattern precedes the reference fluctuation pattern by ΔtYY. Accordingly, it is estimated that the increase time or shortening time ΔτX, ΔτY of the time length of the drive command pulse is equal to the variation time difference ΔtXX, ΔtYY.

  Therefore, in one embodiment according to the present invention, the time length of the drive command pulse of the fuel injection valve 3 when the previous injection is performed with the reference injection amount is stored as the reference time length. The difference between the time length of the drive command pulse and the reference time length when the injection amount is not the reference is set as the fluctuation time differences ΔtXX and ΔtYY.

  Further, when the fuel pressure in the nozzle chamber 34 varies, the rail pressure also varies. Therefore, the fluctuation time differences ΔtXX and ΔtYY can be estimated from the fluctuation of the rail pressure.

  Next, as a deviation amount, a variation amount difference between the fluctuation pattern when the pilot injection is not the reference injection amount and the reference fluctuation pattern, that is, the deviation amount in the vertical axis direction in FIGS. 7A and 7B is used. Will be described. This variation amount difference is indicated by QX1 and QX2 in FIG. 7A, and is indicated by QY1 and QY2 in FIG. 7B.

  In FIG. 7A, the fluctuation amount dQ on the fluctuation pattern X can be calculated by adding QX1 to the reference fluctuation amount on the reference fluctuation pattern, or subtracting QX2 from the reference fluctuation amount. In FIG. 7B, the fluctuation amount dQ on the fluctuation pattern Y can be calculated by subtracting QY1 from the reference fluctuation amount or adding QY2 to the reference fluctuation amount. When the fluctuation amount difference QX1, QX2, QY1, QY2 is added and subtracted when the fluctuation pattern X is delayed with respect to the reference fluctuation pattern as shown in FIG. When the time increases with time, the variation difference is subtracted, and when it decreases, the variation difference is added. As shown in FIG. 7B, when the fluctuation pattern Y precedes the reference fluctuation pattern, the above is reversed.

Next, an estimation method of the fluctuation amount differences QX1, QX2, QY1, QY2 will be described.
The further away the pilot injection amount is from the reference injection amount, the larger the fluctuation time differences ΔtXX, ΔtYY of the fluctuation pattern, and the fluctuation amount differences QX1, QX2, QY1, QY2. Therefore, this fluctuation amount difference is proportional to the injection amount difference between the pilot injection amount and the reference injection amount. That is, if the proportionality constant is k, the variation difference is expressed by
Fluctuation amount difference = 1 pilot injection amount−reference injection amount 1 · k
Therefore, the fluctuation amount dQ when the pilot injection is not the reference injection amount is expressed by the following equation.
dQ = reference fluctuation amount + variation amount difference

On the other hand, as shown in FIGS. 7A and 7B, the difference in fluctuation amount gradually decreases as the interval time Ti increases. Therefore, the fluctuation amount difference can also be obtained from the following equation.
Variation amount difference = 1 pilot injection amount−reference injection amount 1 · k · [interval time / (interval time−reference interval time)]
Here, the reference interval time is obtained from an experiment.

  Next, an example of fuel injection control for controlling the injected fuel to the target value will be described with reference to the fuel injection control routine shown in FIG.

  Referring to FIG. 8, first, at step 100, the total injection amount QT is calculated from the map shown in FIG. Next, at step 101, the main injection amount QM is calculated from the map shown in FIG. Next, at step 102, the pilot injection amount QP is calculated by subtracting the main injection amount QM from the total injection amount QT. Next, at step 103, the main injection start timing θM is calculated from the map shown in FIG. Next, at step 104, the interval time TI is calculated from the map shown in FIG. Next, at step 105, the pilot injection start timing θP is calculated from the main injection start timing θM and the interval time TI.

  Next, at step 106, the reference fluctuation amount stored in advance in the ROM 22 is read. Next, at step 107, the fluctuation amount dQ of the main injection M is calculated using one of the various methods described so far. Next, at step 108, the command value for main injection is corrected so that the actual injection amount becomes the target value based on the fluctuation amount dQ. For example, when the fluctuation amount dQ is positive, the fluctuation amount dQ is subtracted from the main injection amount QM calculated in step 101, and the main injection amount (QM-dQ) is obtained by subtracting the actual injection amount. The command value is corrected. On the other hand, if the fluctuation amount dQ is negative, the fluctuation amount dQ is added to the main injection amount QM, and the main injection command value is corrected so as to be the main injection amount (QM + dQ) obtained by adding the actual injection amount. The In this way, the actual injection amount is controlled to the target value QT. Next, at step 109, pilot injection and main injection are performed.

FIG. 1 is an overall view of a compression ignition type internal combustion engine. It is side surface sectional drawing which shows the front-end | tip part of a fuel injection valve. It is a figure which shows an injection pattern. It is a figure which shows the map of injection amount. It is a figure which shows maps, such as main injection time. It is a figure which shows the lift amount of the needle valve at the time of pilot injection, and the fuel pressure in a nozzle chamber. It is a figure which shows the variation | change_quantity of main injection. It is a flowchart which shows fuel-injection control.

Explanation of symbols

2 ... Combustion chamber 3 ... Fuel injection valve 12 ... Fuel supply pipe 13 ... Common rail 31 ... Needle valve 34 ... Nozzle chamber

Claims (9)

  A common rail and a fuel injection valve connected to the common rail, each fuel injection valve performing at least two fuel injections of one injection and one subsequent injection during one cycle of the engine. In an internal combustion engine injection control device in which the amount of fluctuation of the injection amount of the subsequent injection changes with respect to the target value according to the interval time from the start to the subsequent injection, when the previous injection is a predetermined reference injection amount Storage means for storing the reference fluctuation amount of the subsequent injection that changes along the reference fluctuation pattern as the interval time increases, and the fluctuation amount of the subsequent injection when the previous injection is not the reference injection amount Calculating means for estimating the amount of deviation between the fluctuation pattern of the engine and the reference fluctuation pattern and calculating the fluctuation amount of the subsequent injection from the deviation amount, the reference fluctuation amount and the interval time; Fuel injection device for an internal combustion engine and a control means for controlling the target value injection amount using the fluctuation amount more was calculated.   The amount of deviation is the variation time difference between the variation pattern of the variation amount of the subsequent injection when the previous injection is not the reference injection amount and the reference variation pattern. By adding or subtracting this variation time difference to the interval time, The fuel injection device for an internal combustion engine according to claim 1, wherein a correction interval time is obtained, and the fluctuation amount of the subsequent injection is calculated from the correction interval time and the reference fluctuation amount.   The time when the lift amount of the needle valve of the fuel injection valve becomes maximum when the previous injection is performed with the reference injection amount is stored as the reference time, and the needle valve when the previous injection is not the reference injection amount 3. The fuel injection device for an internal combustion engine according to claim 2, wherein a timing at which the lift amount of the engine is maximized is detected and a difference between the timing and the reference timing is set as the variation time difference.   The timing at which the fuel pressure in the nozzle chamber of the fuel injection valve becomes minimum when the previous injection is performed with the reference injection amount is stored as the reference timing, and when the previous injection is not the reference injection amount, the nozzle chamber 3. The fuel injection device for an internal combustion engine according to claim 2, wherein a time at which the fuel pressure of the engine is minimum is detected, and a difference between the time and the reference time is set as the variation time difference.   The time length of the fuel injection valve drive command pulse when the previous injection is performed with the reference injection amount is stored as the reference time length, and the drive command pulse when the previous injection is not the reference injection amount The fuel injection device for an internal combustion engine according to claim 2, wherein a difference between the time length and the reference time length is the variation time difference.   The fuel injection device for an internal combustion engine according to claim 2, further comprising a detecting means for detecting a rail pressure, wherein the fluctuation time difference is estimated from the fluctuation of the rail pressure.   The amount of deviation is the difference between the fluctuation pattern of the fluctuation quantity of the subsequent injection and the reference fluctuation pattern when the previous injection is not the reference injection quantity, and this fluctuation quantity difference is added to or subtracted from the reference fluctuation quantity. The fuel injection device for an internal combustion engine according to claim 1, wherein the fluctuation amount is calculated by doing so.   The fuel injection device for an internal combustion engine according to claim 7, wherein the fluctuation amount difference is calculated from an injection amount difference between a previous injection amount and the reference injection amount, and the fluctuation amount difference increases as the injection amount difference increases. .   The fuel injection device for an internal combustion engine according to claim 8, wherein the fluctuation amount difference is a function of an interval time, and the fluctuation amount difference is reduced as the interval time becomes longer.

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