JP2007023988A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of suitably suppressing the lowering of the accuracy of fuel injection control due to dispersions resulting from a difference in the nature of fuel pump and deterioration with elapsed time. <P>SOLUTION: The discharge frequency of the fuel pump having a first plunger and a second plunger is "180° CA", whereas the frequency of fuel injection is "144° CA". When a fuel is jetted from a fourth cylinder, for example, a predicted fuel pressure "NPC(i)+NPCM-NPC(i-1)" in jetting fuel is calculated by using a fuel pressure NPC(i-1) at a measurement point A, a fuel pressure NPCM at a measurement point B, and a fuel pressure NPC(i) at a measurement point C. Then, a command jetting time is calculated by using the predicted fuel pressure and the command jetting amount. When a jetting period and a force-feed period are overlapped with each other, the command jetting period is corrected according to discharge characteristics specific to a plunger performing force-feeding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection device comprising a pressure accumulating chamber for storing fuel in a high pressure state, a fuel pump for pressurizing fuel to the pressure accumulating chamber, and a fuel injection valve for injecting fuel stored in the pressure accumulating chamber. The present invention relates to a fuel injection control device that performs fuel injection control of an internal combustion engine by operating this.

  As this type of fuel injection device, one having a common pressure accumulation chamber (common rail) for supplying high-pressure fuel to a fuel injection valve of each cylinder of a diesel engine is well known. The fuel injection control device in this common rail type diesel engine sets a command injection period when operating the fuel injection valve based on the required fuel amount and the fuel pressure in the common rail.

  However, since the fuel pressure in the common rail fluctuates due to the pressurized supply (pumping) of fuel from the fuel pump, the same injection period is determined depending on whether the fuel pumping period from the fuel pump overlaps with the fuel injection period. Even if it is set, the amount of fuel actually injected varies.

  Therefore, conventionally, as seen in Patent Document 1 below, for calculating the fuel injection period between the cylinder in which the fuel pumping period by the fuel pump and the fuel injection period by the fuel injection valve overlap and the cylinder that does not overlap, Control devices using different maps have also been proposed. Thereby, an appropriate fuel injection period can be set according to the presence or absence of an overlapping period.

  By the way, in an actual fuel injection device, the fuel discharge characteristics of the fuel pump have variations due to individual differences and changes with time. Therefore, in the above control device, even if the commanded discharge amount by the fuel pump is fixed, the actual injection amount changes to the required injection amount because the amount of fuel actually discharged changes due to individual differences and changes over time. There is a risk of dislodging.

Further, when the fuel pump is provided with a plurality of plungers, and the fuel is sucked and pumped by the reciprocating motion of the plungers, the discharge characteristics may be different for each plunger. For this reason, when applying an asynchronous system in which a plunger whose fuel injection period and pumping period overlap in a specific cylinder changes over time to a multi-cylinder internal combustion engine or the like, a deviation in injection amount due to variations in the discharge characteristics of these plungers Cannot be compensated by learning control of the injection amount for each cylinder. For this reason, when a fuel pump including a plurality of plungers is applied to an asynchronous system, the influence of the individual difference and the change over time becomes particularly serious.
JP 2003-222046 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to suitably suppress deterioration in the accuracy of fuel injection control due to individual differences in fuel pumps and variations due to changes over time. An object of the present invention is to provide a fuel injection control device that can be used.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  According to the first aspect of the present invention, when it is determined that the influence of the pressurization supply is exerted when the fuel injection valve is operated and the means for taking in the detection result of the detection means for detecting the fuel pressure in the pressure accumulating chamber Setting means for setting the operation amount of the fuel injection valve separately when it is determined that there is no influence, and a detection value based on the detection result of the fuel discharge characteristic value of the fuel pump is predetermined. On the basis of the difference from the reference value, it is determined that the calculation means for calculating the correction amount for the operation amount of the fuel injection valve, and that the pressurization supply is affected when the fuel injection valve is operated. And a correction unit that corrects an operation amount set by the setting unit based on a correction amount calculated by the calculation unit.

  In the above configuration, the operation amount of the fuel injection valve is set for each of the time when it is determined that the influence of the pressurized supply is exerted when the operation of the fuel injection valve is performed and the case where it is determined that the influence is not exerted. The For this reason, when the fuel injection valve is operated, it is possible to suitably suppress the actual injection amount from deviating from the required injection amount due to the fluctuation of the fuel pressure in the pressure accumulating chamber due to the pressurized supply. In addition, the operation amount set by the setting means to compensate for the influence due to the fluctuation of the fuel pressure is corrected by the correction amount. This correction amount compensates for the deviation of the actual injection amount from the required injection amount due to the deviation of the discharge characteristic of the fuel pump from the reference value. For this reason, according to the said structure, it can suppress suitably that the precision of fuel-injection control falls by the dispersion | variation resulting from the individual difference of a fuel pump, or a time-dependent change.

  According to a second aspect of the present invention, in the first aspect of the present invention, the calculating means includes a reference value corresponding to a discharge amount of the fuel pump with respect to any one of a discharge start timing and a discharge end timing of the fuel pump, and the Based on at least one of the difference between the detection value based on the detection result and the difference between the reference value corresponding to the discharge amount and the detection value based on the detection result for the amount of increase in the fuel pressure in the pressure accumulating chamber, the correction amount is It is characterized by calculating.

  In the above configuration, if there is no variation due to individual differences or changes with time in the discharge characteristics of the fuel pump, each timing is uniquely determined by the discharge amount. If there is no variation due to individual differences or changes over time in the discharge characteristics of the fuel pump, the amount of increase in fuel pressure is uniquely determined by the discharge amount. For this reason, in the said structure, the dispersion | variation resulting from the individual difference about a discharge characteristic of a fuel pump and a time-dependent change can be quantified by the difference between the reference value and detection value of each said timing and the raise amount.

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the fuel pump includes a plurality of plungers, and sucks and pressurizes and supplies fuel by reciprocating movement of the plungers. The calculation means calculates the correction amount for each plunger based on a difference between a value unique to each plunger and a reference value for the detected value of the discharge characteristic value, and the correction means When it is determined that the influence of pressurized supply of fuel by an arbitrary plunger when the operation of the fuel injection valve is performed, the correction amount corresponding to the plunger among the correction amounts calculated by the calculation means is The operation amount set by the setting means is corrected.

  In the above configuration, the discharge characteristics may vary for each plunger. In this regard, according to the above configuration, when it is determined that the pressurized supply of fuel to the pressure accumulation chamber affects the operation of the fuel injection valve, the setting means uses the correction amount corresponding to the plunger involved in the pressurized supply. The set operation amount is corrected. For this reason, according to the said structure, it can suppress suitably that the actual injection quantity shifts | deviates from the request | requirement injection quantity resulting from the individual difference of each plunger, or a time-dependent change.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the internal combustion engine is a multi-cylinder internal combustion engine, and the fuel injection device includes a plunger of each of the plurality of plungers and a pressurized supply of fuel by the plunger. It is an asynchronous system that does not correspond one-to-one with a cylinder that performs injection close to the timing.

  In the above configuration, when fuel is pressurized and supplied to the pressure accumulating chamber during fuel injection in each cylinder, the plunger involved in this pressure supply changes with time. For this reason, the deviation from the required injection amount of the actual injection amount due to the individual difference of the plungers cannot be appropriately compensated by determining the correction amount for each cylinder. For this reason, the said structure can show | play the effect of the structure of Claim 3 especially suitably.

  According to a fifth aspect of the present invention, in the fourth aspect of the invention, the fuel discharge period of the fuel pump and the fuel injection period of the multi-cylinder internal combustion engine are set at a predetermined integer ratio. The setting means takes into account the behavior of the fuel pressure detected during the previous operation of the fuel injection valve when setting the operation amount of the fuel injection valve.

In the above configuration, since the discharge cycle and the fuel injection cycle are set at a predetermined integer ratio, the following case occurs.
Case A. If the plungers are not distinguished, the relationship between the fuel injection timing and the pressure supply timing of a specific cylinder is exactly the same periodically.
Case B. If the plungers are not distinguished, the relationship between the fuel injection timing and the pressure supply timing of one cylinder is periodically exactly the same as the relationship between the fuel injection timing and the pressure supply timing of another cylinder. Case.

  In case A, except for individual differences and changes over time of the plunger, the behavior of the fuel pressure during the current period of fuel injection is predicted based on the behavior of the fuel pressure during the fuel injection during the previous period while the fuel injection during the current period. The operation amount can be set.

  In case B, except for individual differences and changes over time of the plunger and the fuel injection valve, while predicting the behavior of fuel pressure at the time of fuel injection of another cylinder based on the behavior of fuel pressure at the time of fuel injection of another cylinder, The operation amount at the time of fuel injection of the cylinder can be set.

  According to such control, although the operation amount for the operation is set prior to the operation of the fuel injection valve, the behavior of the fuel pressure predicted when this operation is performed is reflected in the setting of the operation amount. Therefore, the operation amount can be set more appropriately. Then, the operation amount set in this way is corrected by a correction amount corresponding to the individual difference of the plunger and the change over time, so that the plunger related to the pressurized supply at the time of detecting the fuel pressure used for prediction is different from the current one. However, the operation amount can be set appropriately.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the setting means overlaps a period of the pressurization supply by the fuel pump and a period of fuel injection by the fuel injection valve. First and second setting means for determining a basic operation amount when operating the fuel injection valve from the detected fuel pressure and the required injection amount, Two weighting factors are calculated on the basis of the overlap between the pressure supply period and the injection period, and the two basic operation amounts determined by the first setting means and the second setting means are calculated. And a means for determining the manipulated variable by performing a weighted average process using the two weighting factors.

  In the above configuration, the basic operation amount when there is no overlap between the pressurized supply period and the injection period is determined by the first setting means, and the basic operation amount when there is an overlap is the second operation amount. It is determined by setting means. However, an appropriate value as a basic operation amount when there is an overlap varies depending on the overlap mode. In this regard, in the above configuration, it is possible to set an appropriate operation amount according to the operation mode by performing a weighted average process on the two basic operation amounts determined by the first setting unit and the second setting unit. it can.

(First embodiment)
Hereinafter, a first embodiment in which a fuel injection control device according to the present invention is applied to a fuel injection control device of a diesel engine will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of the engine system according to the present embodiment.

  As shown in the figure, the fuel in the fuel tank 2 is pumped up by the fuel pump 6 through the fuel filter 4. The fuel pump 6 is powered by a crankshaft 8 that is an output shaft of a diesel engine and discharges fuel. Specifically, the fuel pump 6 includes an intake metering valve 10, and the amount of fuel discharged to the outside is determined by operating the intake metering valve 10. The fuel pump 6 includes two plungers, and these plungers reciprocate between a top dead center and a bottom dead center, whereby fuel is sucked and discharged.

  The fuel from the fuel pump 6 is pressurized and supplied (pressure fed) to the common rail 12. The common rail 12 stores the fuel pumped from the fuel pump 6 in a high pressure state, and supplies the fuel to the fuel injection valve 16 of each cylinder (here, five cylinders are illustrated) via the high pressure fuel passage 14. The fuel injection valve 16 is connected to the fuel tank 2 via a low pressure fuel passage 18.

  The engine system includes various sensors that detect the operating state and operating environment of the diesel engine, such as a fuel pressure sensor 20 that detects the fuel pressure in the common rail 12 and a crank angle sensor 22 that detects the rotation angle of the crankshaft 8. Yes. Further, the engine system includes an accelerator sensor 24 that detects an operation amount of an accelerator pedal operated in response to a user's acceleration request.

  On the other hand, the electronic control unit (ECU 30) is composed mainly of a microcomputer, takes in the detection results of the various sensors, and controls the output of the diesel engine based on this.

  The ECU 30 performs fuel injection control so as to appropriately control the output of the diesel engine. In this fuel injection control, the fuel pressure in the common rail 12 is feedback-controlled to a target fuel pressure that is set according to the operating state and operating environment of the diesel engine.

  Here, the fuel injection control according to the present embodiment will be further described with reference to FIG.

  2 (a) to 2 (e) respectively show fuel injection command periods (command injection periods) for the fuel injection valves 16 of the first cylinder to the fifth cylinder (in this case, here, one-stage pilot injection p) And one stage of main injection m). FIG. 2F shows the transition of the fuel pressure in the common rail 12. Also, FIG. 2 (g) shows the transition of the fuel intake and discharge (pressure feed) mode by one plunger (first plunger), and FIG. 2 (h) shows the fuel intake by the other plunger (second plunger). The transition of the discharge (pressure feeding) mode is shown respectively.

  As shown in the drawing, the amount of suction is determined by the operation mode of the suction metering valve 10 when the first plunger and the second plunger are displaced toward the bottom dead center. Then, when the first plunger or the second plunger is displaced toward the top dead center next time, the fuel sucked last time is discharged.

  In the present embodiment, the fuel pumping cycle by the first plunger or the second plunger is “480 ° CA”, and the fuel pumping cycle by the fuel pump 6 is “240 ° CA”. On the other hand, the cycle in which the fuel is injected is every “144 ° CA”. For this reason, the fuel injection device in the present embodiment is an asynchronous system in which the pressure feeding timing by the first plunger or the second plunger and the fuel injection timing of each cylinder do not correspond one to one.

  Since the pumping cycle by the fuel pump 6 and the fuel injection cycle are set to an integer ratio (here, “5: 3”), the relationship between the pumping timing by the fuel pump 6 and the fuel injection timing is predetermined. Equal to each other. Here, this period is “720 ° CA”. For example, as shown in the drawing, the fuel injection of the fourth cylinder is performed in a period between the previous pumping by the fuel pump and the current pumping. The intervals between the pumping period and the fuel injection timing are the same crank angle in the current injection and the previous injection.

  Incidentally, the amount of fuel injected through the fuel injection valve 16 is determined by the command injection period of the fuel injection valve 16 and the fuel pressure in the common rail 12. For this reason, when determining the command injection period, it is desirable to use the fuel pressure detected by the fuel pressure sensor 20 during fuel injection. Therefore, in the present embodiment, the fuel pressure at the current fuel injection is estimated based on the fuel pressure detected at the time of fuel injection before “720 ° CA”, and the current command injection period is determined based on this. Thus, the command injection period can be set appropriately while the command injection period is determined prior to the operation of the fuel injection valve 16. That is, as described above, since the timing relationship between the pumping period and the injection period is the same between the injection before “720 ° CA” and the current injection, the behavior of the fuel pressure before “720 ° CA” This is considered to be similar to the behavior of fuel pressure. For this reason, the behavior of the current fuel pressure can be estimated based on the behavior of the fuel pressure before “720 ° CA”.

  Specifically, prior to fuel injection, the fuel pressure in the common rail 12 is detected at a timing before a predetermined crank angle from the top dead center of the cylinder performing injection (measurement points A and C in the figure). Further, the fuel pressure is also detected during the main injection (here, the start timing of the command injection period) (measurement point B in the figure). Here, in this embodiment, the detection value (detection value at the measurement point A) prior to the previous injection is defined as the fuel pressure NPC (i-1), and the detection value at the previous injection (detection value at the measurement point B). Is the fuel pressure NPCM, the detection value prior to the current injection (the detection value at the measurement point C) is the fuel pressure NPC (i), and the fuel pressure at the time of the current fuel injection is “NPC (i) + NPCM−NPC (i−1) ) ”. Based on this, the current command injection period is calculated.

  However, in the injection before “720 ° CA” and the current injection, the plungers involved in the pressure feeding at timings close to these timings are different. For example, as shown in the example of the fourth cylinder in FIG. 2, the previous injection was performed after the pumping by the first plunger and before the pumping by the second plunger. After the pumping by the two plungers and before the pumping by the first plunger. For this reason, when there is a variation in discharge characteristics due to individual differences or changes over time between the first plunger and the second plunger, the relationship between the timing of injection and the timing of pressure feeding close to this due to this variation Changes. This may cause the actual fuel amount to deviate from the required fuel amount.

  The decrease in control accuracy due to the above-described variation is eliminated by estimating the fuel pressure during the current injection based on the fuel pressure during the injection before “1440 ° CA”. This is because in this embodiment, the timing relationship between the fuel injection and the pumping by the plunger is equal for every “1440 ° CA”. However, from the viewpoint of maintaining high accuracy in estimating the fuel pressure during the current injection, it is desirable that the interval between the detection of the fuel pressure used for the estimation and the current injection is short.

  Therefore, in the present embodiment, the fuel pressure at the time of the current injection is estimated based on the fuel pressure at the time of injection before “720 ° CA”, and the command injection period determined based on the estimated fuel pressure is set to each plunger of the fuel pump 6. The correction is made on the basis of the inherent discharge characteristics. This will be described below.

  FIG. 3 shows a procedure of processing relating to the calculation of the correction amount for the command injection period based on the specific discharge characteristics. This process is repeatedly executed by the ECU 30, for example, at a predetermined cycle.

  In this series of processing, first, in step S12, the current pumping amount of the fuel pumped to the common rail 12 by the fuel pump 6 is estimated. This pumping amount is calculated on the assumption that the amount of fuel injected by the fuel injector 16 and the amount of leaked fuel leaking from the fuel injector 16 to the low-pressure fuel passage 18 during fuel injection are compensated by the feedback control. Can do. Incidentally, the injection amount can be a required injection amount for generating a required torque based on the operation amount of the accelerator pedal detected by the accelerator sensor 24 and the rotational speed detected by the crank angle sensor 22. In other words, this is a command injection amount for the fuel injection valve 16. Further, the amount of leaked fuel can be calculated from this map by preparing in advance a map that defines the relationship between the fuel pressure in the common rail 12, the rotational speed, and the like. Incidentally, when the target fuel pressure in the common rail 12 changes, a fuel amount for following this change is added to the pumping amount by feedback control. However, instead of this, it is more desirable that the steady state in which the target fuel pressure does not change be the execution condition of the process shown in FIG.

  In subsequent step S14, the pumping start timing is calculated based on the pumping amount estimated in step S12. Since the fuel pump 6 includes the intake metering valve 10 as described above, the discharge start timing changes according to the intake amount. For this reason, the pumping start timing changes according to the suction amount (pumping amount). The calculation of the pumping start timing is performed assuming that the discharge characteristic of the fuel pump 6 is a reference characteristic. Here, the reference may be, for example, an average discharge characteristic (center characteristic value) when a plurality of fuel pumps 6 are manufactured. Accordingly, since the fuel pump 6 is an engine-driven pump, if the individual difference of the fuel pump 6 and the change with time are ignored, the crank angle (or cam angle) for starting the pumping is uniquely determined by the pumping amount. be able to. This step S14 may be a process using a map that defines the relationship between the pumping amount and the pumping start timing. Also, geometric information about the change in the stroke of the plunger of the fuel pump 6 and the shape of the plunger, the pumping The pumping start timing may be calculated based on the amount. The pumping start timing may be a timing at which the fuel pump 6 starts to discharge the fuel. However, a delay time until the fuel discharged from the fuel pump 6 is pumped to the common rail 12 through the fuel passage is used. You may consider it.

  In subsequent step S16, it is determined from the rotation angle of the crankshaft 8 whether the plunger involved in the current pressure feeding is the first plunger or the second plunger. Further, in step S18, it is determined whether or not the pumping period and the injection period overlap. This process is performed in order to eliminate the influence of the decrease in the fuel pressure due to the injection when the pumping start timing is detected as a change in the fuel pressure in the common rail 12. Specifically, this determination is made based on, for example, the pumping start timing calculated in step S14 and the start timing of the current command injection period.

  When it is determined in step S18 that there is no overlap, the process proceeds to step S20. In this step S20, the pumping start timing is detected based on the fuel pressure rising start timing in the common rail 12.

  On the other hand, in step S22, the correction amount for each plunger is calculated based on the difference between the reference value calculated in step S14 and the detected value detected in step S20 regarding the pumping start timing. That is, when it is determined in step S16 that it is the first plunger, the first plunger correction amount ΔTQ1 is calculated, and when it is determined in step S16 that it is the second plunger, the second plunger correction amount ΔTQ2 is calculated. Is calculated.

  When it is determined in step S18 that they are duplicated or when the process of step S22 is completed, this series of processes is temporarily ended.

  Next, a process for calculating the command injection period using the correction amount and a process for operating the fuel injection valve 16 during the command injection period will be described.

  FIG. 4 shows the procedure of the above processing. This process is repeatedly executed by the ECU 30, for example, at a predetermined cycle.

  In this series of processing, first, in step 30, the command injection amount, the detected value of the fuel pressure by the fuel pressure sensor 20, the cylinder number in which the current fuel injection is performed, the number of the plunger that pumps the current fuel to the common rail 12, the injection start timing, The rotational speed of the crankshaft 8 is read. In the subsequent step S32, the pumping amount is estimated and the pumping start timing is calculated in the same manner as the processing in steps S12 and S14 of FIG. 3 based on the command injection amount and the rotational speed read in step S30.

  In the subsequent step S34, weighting coefficients α and β are calculated by quantifying the degree of influence of the fuel pumping from the fuel pump 6 into the common rail 12 during the current injection. Here, the weighting coefficients α and β are standardized and “α + β = 1”. The weighting factor α is “1” when there is no influence of pumping, and the weighting factor β is “0” when there is no influence of pumping.

  In subsequent step S36, the correction amount (correction amount ΔTQ1 or correction amount ΔTQ2) of the plunger corresponding to the plunger number read in step S30 among the correction amounts calculated by the processing shown in FIG. 3 is fetched.

  In the subsequent step S38, a command injection period TQ is calculated. This calculation is basically based on a map where the pumping period and the injection period do not overlap (when there is no influence of pumping) (in the figure, non-overlapping cylinders), and the pumping period and the injection period overlap. This is done using a map (pumped cylinder in the figure). These maps are used to calculate a basic command injection period TQB1 (TQB2) from the fuel pressure NPC (specifically, the predicted fuel pressure described with reference to FIG. 2) and the command injection amount QFIN.

  The map at the time of the overlap is a map when the injection timing and the overlap timing have a predetermined relationship. However, even if the pumping period and the injection period are overlapped, the overlapping modes are various. For example, in the example shown in FIG. 2, the cylinder No. 3 and the cylinder No. 4 both have the same pressure-feed period and injection period, but the overlap mode is different. For this reason, it is not possible to accurately calculate the command injection period at the time of overlap with only one map at the time of overlap shown in FIG. Therefore, in the present embodiment, the overlap mode is quantified by the weighting factors α and β calculated in step S34 as the degree of influence of pumping. As a result, the command injection period based on the degree of influence of pumping can be calculated by multiplying the values calculated from the two maps by the corresponding weighting factors α and β (weighted average processing). it can.

  However, at this time, if there is a variation in the discharge characteristics of each plunger of the fuel pump 6, using the command injection period calculated in the overlapping map will cause a deviation in the injection amount due to the variation in the discharge characteristics. May occur. Therefore, in the present embodiment, in the weighted average process, the correction amount ΔTQ1 (ΔTQ2) is added to the basic command injection period TQB2 calculated from the overlapping maps. Incidentally, the overlapping map is created on the assumption that the discharge characteristic of the fuel pump 6 is a reference value. The reference value may be an average discharge characteristic (center characteristic value) when a plurality of fuel pumps 6 are manufactured.

  By the process of step S38, the command injection period TQ is calculated as follows.

TQ = α × TQB1 + β {TQB2 + ΔTQ1}
Or
TQ = α × TQB1 + β {TQB2 + ΔTQ2}
When the command injection period TQ is calculated in step S38, the fuel injection valve 16 is operated based on the command injection period TQ in step S40.

  In addition, when the process of step S40 is completed, this series of processes is once complete | finished.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) The correction amount ΔTQ1 (ΔTQ2) of the command injection period is calculated based on the difference between the reference value and the detected value for the discharge start timing of the fuel pump 6. The difference between the reference value of the discharge start timing and the detected value can quantify the variation in the discharge characteristics of the fuel pump 6 due to individual differences and changes over time. For this reason, the deviation from the command injection quantity of the injection quantity resulting from the individual difference of the fuel pump 6 and the change with time can be suitably suppressed.

  (2) The fuel pump 6 is provided with two plungers and performs fuel suction and pressure supply by reciprocating movement of the plungers, and the correction amount of the command injection period is calculated for each plunger. Thereby, it can suppress suitably that the actual injection quantity shifts | deviates from instruction | command injection quantity resulting from the individual difference of each plunger, or a time-dependent change.

  (3) An asynchronous system in which each plunger of a plurality of plungers and a cylinder that injects fuel at a timing close to the pressure supply timing of fuel by the plunger does not correspond one-to-one to the fuel injection device. In this case, by determining the correction amount for each cylinder, it is not possible to appropriately compensate for the deviation in the injection amount due to the individual difference between the plungers. Therefore, the present embodiment has the effects (1) and (2) described above. It is also the structure which can be matched especially suitably.

  (4) When calculating the current command injection period, the fuel pressure at the current injection is estimated based on the fuel pressure detected at the time of fuel injection before “720 ° CA”, and the current command injection period is calculated based on this. . Thereby, a command injection period can be set more appropriately.

  (5) Two maps for calculating the basic command injection periods TQB1 and TQB2 corresponding to the overlap between the pumping period and the injection period are provided, and the command injection period TQ is set to two basic commands. The injection periods ΔTQB1 and ΔTQB2 were calculated by performing a weighted average process. Thereby, it is possible to set an appropriate operation amount in accordance with the overlap between the pumping period and the injection period.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, correction amounts ΔTQ1 and ΔTQ2 are calculated by the processing shown in FIG. FIG. 5 shows a processing procedure for calculating the correction amount. This process is repeatedly executed by the ECU 30, for example, at a predetermined cycle.

  In this series of processing, first, in step S52, the pumping amount is estimated in the same manner as in step S12 of FIG. In the subsequent step S54, the amount of increase in fuel pressure in the common rail 12 is calculated based on the pumping amount. For example, this is calculated by using the sum V of the volume of the fuel passage between the fuel pump 6 and the common rail 12 and the volume of the common rail 12, the volume expansion coefficient E of the fuel, and the pumping amount F. What is necessary is just to calculate as V.

  In subsequent steps S56 and S58, processing similar to that in steps S16 and S18 of FIG. 3 is performed. If it is determined in step S58 that there is no overlap, the amount of increase in the fuel pressure in the common rail 12 is detected in step S60. Here, for example, the peak value of the rising fuel pressure may be detected.

  In subsequent step S62, the correction amount for each plunger is calculated based on the difference between the reference value calculated in step S54 for the amount of increase and the detected value detected in step S60. That is, when it is determined in step S56 that it is the first plunger, the first plunger correction amount ΔTQ1 is calculated, and when it is determined in step S56 that it is the second plunger, the second plunger correction amount ΔTQ2 is calculated. Is calculated.

  Note that when it is determined in step S58 that there is an overlap, or when the process of step S62 is completed, this series of processes is temporarily terminated.

  Also according to the present embodiment described above, it is possible to obtain the effects according to the above (1) to (5) of the first embodiment.

(Other embodiments)
The above embodiments may be implemented with the following modifications.

  ・ Diesel engines are not limited to those with 5 cylinders. For example, any cylinder other than “5” may be used. However, in the case of a multi-cylinder internal combustion engine, it is particularly effective to make the fuel injection device an asynchronous system. This is because, when the pumping period and the injection period overlap, the plunger involved in pumping changes with time, so by determining the correction amount for each cylinder, the injection amount due to individual differences in the plunger and changes over time This is because the deviation cannot be compensated appropriately.

  At this time, it is desirable that the fuel injection and the discharge of the fuel pump be the crank angle period, and that a predetermined integer ratio is established between these periods. Thereby, the injection which becomes equal to the relationship between the injection timing at the time of arbitrary injection, and a pumping timing arises periodically. For this reason, at the time of this injection, the command injection period can be set more appropriately by referring to the fuel pressure at the time of the previous injection having the same relationship.

  FIG. 6A shows a case where the injection cycle is “180 ° CA” and the discharge cycle is “144 ° CA” in a four-cylinder internal combustion engine. In this case, for example, the relationship between the injection timing and the pumping timing of the first cylinder is equal to the relationship between the injection timing and the pumping timing of the fourth cylinder before “1080 ° CA”. For this reason, the fuel pressure at the time of injection of the first cylinder can be estimated using this relationship, and the command injection period can be determined based on this.

  FIG. 6B shows a case where the injection cycle is “180 ° CA” and the discharge cycle is “240 ° CA” in a four-cylinder internal combustion engine. In this case, for example, the relationship between the injection timing and the pumping timing of the first cylinder is equal to the relationship between the injection timing and the pumping timing of the first cylinder before “720 ° CA”. For this reason, the fuel pressure at the time of injection of the first cylinder can be estimated using this relationship, and the command injection period can be determined based on this.

  In both the examples shown in FIGS. 6A and 6B, the plungers are not the same in the shortest cycle in which the relationship between the injection timing and the pumping timing is equal. For this reason, it is particularly effective to calculate a unique correction amount for each plunger.

  -As a diesel engine, it is good also as a single cylinder internal combustion engine. Even in this case, when a fuel pump having a plurality of plungers is used, if the injection amount deviates from the required injection amount due to individual differences or changes with time of each plunger, a correction amount to compensate for this deviation is set. It is effective to calculate.

  -The number of plungers of the fuel pump is not limited to two and may be any plural number. Even in such a case, it is effective to calculate a correction amount that compensates for a deviation in the injection amount due to variations in the ejection characteristics due to individual differences among the plungers and changes over time. Furthermore, the number of plungers may be one. Even in this case, if the plunger discharge characteristics (in this case, the fuel pump discharge characteristics) vary due to individual differences or changes over time, the command injection period is not calculated based on the reference discharge characteristics. Since the actual injection amount deviates from the required injection amount, it is effective to calculate a correction amount that compensates for this.

  The method for calculating the command injection period according to the degree of pumping between the pumping period and the injection period is not limited to two maps according to the presence or absence of overlap, and weighted average processing of the values calculated by these maps . For example, based on the estimated pumping start timing, pumping amount, injection start timing, and command injection period, fuel pressure changes at the time of overlap may be averaged, and the command injection period may be calculated based on this. Even in this case, since it is necessary to use characteristics that serve as a reference for the discharge characteristics of the fuel pump 6 in estimating the pumping start timing, variations in the injection amount due to variations in the discharge characteristics of the fuel pumps (each plunger). The calculation of the correction amount for compensating for is effective.

  The pumping start timing used for calculating the command injection period may be estimated based on the discharge characteristics specific to each plunger detected in FIG. In this case, the pumping start timing corresponds to a correction amount for correcting the operation amount of the fuel injection valve.

  The fuel pump 6 is not limited to the one provided with the intake metering valve. For example, a fuel metering valve that controls the discharge amount at the time of discharge may be provided. In this case, it is desirable to set the pumping start timing in FIG. 3 as the pumping end timing.

  The method for calculating the correction amount for the command injection period is not limited to the one exemplified in the first embodiment and the second embodiment. For example, the correction amount may be calculated based on both the pumping start timing and the increase amount.

  The correction target may be the command injection amount instead of the command injection period. In this case, the required injection amount for generating the torque required by the operation amount of the accelerator pedal detected by the accelerator sensor 24 and the rotational speed of the crankshaft 8 is changed according to individual differences of fuel pumps (each plunger) or changes with time. The command injection amount is set by correcting with a correction amount used for compensating for the deviation of the actual injection amount due to the above.

  In addition, the internal combustion engine is not limited to a diesel engine, and may be, for example, a cylinder injection gasoline engine.

The figure which shows the whole structure of the engine system in 1st Embodiment. The time chart which shows the fuel-injection timing in the same embodiment. The flowchart which shows the process sequence of calculation of the corrected amount of the command injection period in the embodiment. The flowchart which shows the process sequence of calculation of the command injection period in the embodiment. The flowchart which shows the process sequence of calculation of the corrected amount of the command injection period in 2nd Embodiment. The time chart which illustrates an asynchronous system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 6 ... Fuel pump, 10 ... Inhalation metering valve, 12 ... Common rail, 16 ... Fuel injection valve, 30 ... ECU (one Embodiment of a fuel injection control apparatus).

Claims (6)

A fuel injection device including a pressure accumulator that stores fuel in a high pressure state, a fuel pump that pressurizes and supplies fuel to the pressure accumulator, and a fuel injection valve that injects fuel stored in the pressure accumulator is operated. In the fuel injection control device for performing the fuel injection control of the internal combustion engine,
Means for capturing the detection result of the detection means for detecting the fuel pressure in the pressure accumulation chamber;
Setting means for setting the operation amount of the fuel injection valve separately when it is determined that the influence of the pressurized supply is exerted when the fuel injection valve is operated and when it is determined that the influence is not exerted When,
Calculating means for calculating a correction amount for the operation amount of the fuel injection valve based on a difference between a detection value based on the detection result of the fuel discharge characteristic value of the fuel pump and a predetermined reference value;
Correction means for correcting an operation amount set by the setting means by a correction amount calculated by the calculation means when it is determined that the influence of the pressurized supply is exerted when the fuel injection valve is operated; A fuel injection control device comprising:   The calculation means includes a difference between a reference value corresponding to a discharge amount of the fuel pump and a detection value based on the detection result for any one of a discharge start timing and a discharge end timing of the fuel pump, and a fuel pressure in the pressure accumulation chamber 2. The fuel injection control device according to claim 1, wherein the correction amount is calculated based on at least one of a difference between a reference value corresponding to the discharge amount and a detection value based on the detection result. . The fuel pump is provided with a plurality of plungers, and performs suction and pressurization of fuel by reciprocating movement of each plunger.
The calculation means calculates the correction amount for each plunger based on a difference between a value specific to each plunger and a reference value for the detected value of the discharge characteristic value.
The correction means corresponds to the plunger of the correction amount calculated by the calculation means when it is determined that the influence of the pressurized supply of fuel by an arbitrary plunger is exerted when the fuel injection valve is operated. 3. The fuel injection control device according to claim 1, wherein the operation amount set by the setting means is corrected by the corrected amount. The internal combustion engine is a multi-cylinder internal combustion engine;
The fuel injection device is an asynchronous system in which each plunger of the plurality of plungers and a cylinder that performs injection close to a fuel pressure supply timing by the plunger do not correspond one-to-one. 3. The fuel injection control device according to 3. The fuel discharge period of the fuel pump and the fuel injection period of the multi-cylinder internal combustion engine are set at a predetermined integer ratio,
5. The fuel injection control device according to claim 4, wherein the setting means takes into account the behavior of the fuel pressure detected during the previous operation of the fuel injection valve when setting the operation amount of the fuel injection valve.   The setting means corresponds to the presence / absence of overlap between the period of the pressurized supply by the fuel pump and the period of fuel injection by the fuel injection valve, and the detected fuel pressure and the required injection amount, To calculate two weighting factors based on the first and second setting means for determining the basic operation amount when operating the fuel injection valve, and the overlap between the pressurized supply period and the injection period. And means for determining the operation amount by performing a weighted average process on the two basic operation amounts determined by the first setting means and the second setting means using the two weighting factors. The fuel injection control device according to any one of claims 1 to 5.

Images