JP2007085250A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of highly maintaining the control accuracy of fuel injection irrespective of whether a fuel pressure is varied or not between conversion timings by an A/D converter. <P>SOLUTION: A fuel injection frequency is "90° CA", a fuel force-feed frequency to feed a fuel to a common rail is "144° CA", and an A/D conversion frequency of the output of a fuel pressure sensor detecting the fuel pressure in the common rail is "180° CA". For example, when the fuel injection of a second cylinder is controlled, an A/D conversion value immediately before the injection of a fourth cylinder which is a conversion timing immediately before the injection is corrected on the basis of the lowered amount of the fuel pressure due to a fuel injection into the fourth cylinder and the raised amount of the fuel pressure due to the force-feed of the fuel by a second plunger. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel for an in-vehicle internal combustion engine comprising: a pressure accumulating chamber that stores fuel in a high pressure state; a fuel pump that pressurizes and supplies the fuel to the pressure accumulating chamber; The present invention relates to a fuel injection control device that performs fuel injection control by operating the injection device.

  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. According to this common rail type diesel engine, the fuel pressure in the common rail can be freely controlled according to the engine operating condition, and as a result, the fuel pressure supplied to the fuel injection valve can be freely controlled.

  The fuel injection control in the diesel engine is normally performed by setting the operation amount (command injection period) of the fuel injection valve based on the detected value of the fuel pressure in the common rail and the required injection amount. That is, since the injection amount increases as the fuel pressure increases even during the same injection period, the command injection period is set using a two-dimensional map of the required injection amount and the fuel pressure.

  However, in the case of an asynchronous fuel injection device in which a cylinder in which the fuel pressure supply (pressure feeding) period from the fuel pump to the common rail and the fuel injection period overlap and a cylinder that does not overlap exist, the fuel pressure by pumping There are cylinders that are affected by changes in the number of cylinders and cylinders that are not. In this case, if the fuel pressure detected prior to fuel injection is used, the required amount of fuel cannot be injected.

  Therefore, conventionally, as can be seen, for example, in the following Patent Document 1 (paragraph [0009]), the fuel pressure is redetected immediately before fuel injection, and the command injection period is recalculated based on the redetected fuel pressure. An injection control device has also been proposed. Thereby, an appropriate command injection period can be calculated based on the fuel pressure at the time of fuel injection.

By the way, the fuel injection control device is usually provided with an A / D converter that converts the output of the fuel pressure sensor that detects the fuel pressure in the common rail into digital data. Converted. Various restrictions may be imposed on this conversion cycle, and it is not always possible to convert the output of the fuel pressure sensor by the A / D converter immediately before fuel injection. For this reason, even if the conversion value at the latest conversion timing by the A / D converter is used, an appropriate command injection period may not be set due to a change in fuel pressure between the conversion timing and fuel injection. there were.
JP 2004-316460 A

  The present invention has been made to solve the above-described problems, and the object thereof is to maintain high control accuracy of fuel injection regardless of a change in fuel pressure between conversion timings by the A / D converter. A fuel injection control device is provided.

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

  According to a first aspect of the present invention, there is provided a converter for converting the output of the detecting means for detecting the fuel pressure in the pressure accumulating chamber into digital data at a predetermined conversion cycle, the fuel pressure in the pressure accumulating chamber and the required injection amount. In the fuel injection control by the operation of the fuel injection valve and the calculation means for calculating the operation amount of the fuel injection valve, the fuel pressure in the pressure accumulating chamber in the period from the latest conversion timing of the converter to the start of the fuel injection Information about storage means for storing processing information for performing processing for calculating the manipulated variable according to a change, information about a conversion value at the latest conversion timing, and timing of the fuel injection is stored in the processing information. And setting means for setting the operation amount by reflecting.

  In the above configuration, there is processing information for calculating the operation amount by the calculating means according to the change in the fuel pressure in the pressure accumulating chamber in the period from the latest conversion timing by the converter to the start of the fuel injection valve. For this reason, according to the said structure, regardless of the change of the fuel pressure after the conversion timing by a converter, the operation amount of a fuel injection valve can be calculated appropriately.

  According to a second aspect of the present invention, in the first aspect of the present invention, the conversion cycle is set longer than the cycle of the fuel injection timing, and the change of the fuel pressure includes the latest conversion by the converter. A reduction amount of the fuel pressure in the pressure accumulating chamber due to another fuel injection performed from timing to setting of the operation amount is included.

  In the above configuration, since the conversion cycle is longer than the cycle of the fuel injection timing, the conversion value at a certain timing may be used as the latest conversion value in a plurality of times of fuel injection control. For this reason, in particular, the fuel pressure in the pressure accumulating chamber changes due to the injection performed earlier in the multiple times of fuel injection control. In this regard, in the above configuration, since the subsequent fuel injection is performed by the operation amount of the fuel injection valve calculated by the calculation means in accordance with the amount of decrease in the fuel pressure due to the previous injection, the subsequent fuel injection is also performed. The control accuracy of the injection can be kept high.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the change in the fuel pressure may be caused by pressurizing fuel supplied between the latest conversion timing by the converter and the setting of the manipulated variable. The fuel pressure change in the pressure accumulating chamber is included.

  In the above configuration, since it has processing information for calculating the operation amount by the calculation means according to the change in the fuel pressure by the pressure supply performed from the latest conversion timing to the setting of the operation amount, the fuel pressure by the pressure supply is changed. Regardless of the change, the control accuracy of fuel injection can be maintained high.

  According to a fourth aspect of the present invention, there is provided the invention according to any one of the first to third aspects, wherein a relationship among a period of pressurized fuel supply by the fuel pump, a period of the fuel injection timing, and the conversion period is predetermined. And the processing information includes a map for determining a correction value for correcting the latest conversion value for each fuel injection within a predetermined cycle with respect to the rotation angle of the internal combustion engine, and And the information that causes the calculation means to calculate the manipulated variable using the latest conversion value corrected by the correction value.

  In the above-described configuration, the relationship between the cycle of pressurized fuel supply by the fuel pump, the cycle of the fuel injection timing, and the conversion cycle is set at a predetermined integer ratio. For this reason, even if the relationship between the fuel injection timing, the pressure supply timing, and the conversion timing changes, these relationships coincide with each other with respect to a predetermined cycle of the rotation angle of the internal combustion engine. For this reason, the amount of deviation of the actual fuel pressure from the latest conversion value at the fuel injection timing tends to be substantially equal in a predetermined cycle. In this regard, in the above configuration, the predetermined cycle is set as a predetermined cycle, and a map for determining a correction value for correcting the latest conversion value individually for each fuel injection performed within the cycle is provided. The operation amount corresponding to the change in the fuel pressure until the start can be appropriately calculated. In particular, the calculation load of the fuel injection control device can be reduced by providing the map.

  According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the map sets the correction value based on at least one of a rotational speed of the internal combustion engine and the latest conversion value for each fuel injection. It is characterized by being.

  In the above configuration, when the rotational speed of the internal combustion engine changes, the time from the latest conversion timing to the fuel injection timing changes. Due to this time change, the amount of fuel leaking from the pressure accumulating chamber may change from the latest conversion timing to the fuel injection timing. Further, the amount of change in the fuel pressure during the period from the latest conversion timing to the fuel injection timing depends on the amount of fuel injected from the fuel injection valve and the amount of fuel supplied under pressure from the fuel pump. The injection amount and the pressurized supply amount usually have a correlation with the fuel pressure in the pressure accumulating chamber. This is because the target fuel pressure in the pressure accumulating chamber is set according to the injection amount and the rotational speed. In this regard, in the above configuration, the correction value is set according to at least one of the rotation speed and the conversion value, so that the dependency of the change in the fuel pressure on the rotation speed, the injection amount, and the pressurized supply amount can be taken into consideration. Thus, the manipulated variable can be calculated more appropriately reflecting the change in the fuel pressure.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to third aspects, the processing information is determined based on the latest conversion timing of the converter when fuel injection control is performed by operating the fuel injection valve. Information for determining the presence or absence of another fuel injection in the period until the start of injection, information for calculating the amount of change in the fuel pressure in the pressure accumulating chamber accompanying the fuel injection when it is determined that there is fuel injection, and the period Information for determining whether or not the pressurized supply is present and information for calculating the amount of change in the fuel pressure in the pressure accumulator chamber when the pressurized supply is determined. .

  In the above configuration, in each fuel injection control, if there is another fuel injection or pressurized supply of fuel to the pressure accumulating chamber in the period from the latest conversion timing to the start of the fuel injection, the amount of change in the fuel pressure due to these fuel injections Is calculated. For this reason, the operation amount of the fuel injection valve can be appropriately calculated by the calculation means using the calculated change amount of the fuel pressure.

  The invention according to claim 7 is the invention according to claim 6, wherein the conversion cycle is a rotation angle cycle of the internal combustion engine.

  In the above configuration, since the conversion cycle is a rotation angle cycle, the relationship between the conversion timing and the fuel injection timing, and the relationship between the conversion timing and the pressure supply timing are easily expressed by the rotation angle. . For this reason, the presence or absence of another fuel injection or pressurized fuel supply to the pressure accumulating chamber during the period can be easily grasped based on the rotation angle.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the internal combustion engine is a multi-cylinder internal combustion engine, and the fuel injection device includes the timing of the fuel injection and the pressurization supply. Is a non-corresponding one-to-one system, and the conversion cycle is longer in the rotation angle cycle than the fuel injection timing cycle.

  In the above configuration, since the fuel injection device is an asynchronous system, the relationship between the timing of fuel injection and the timing of pressure supply by the fuel pump may vary among cylinders. In addition, in the above configuration, since the conversion cycle is longer than the cycle of fuel injection, the single conversion value may be used as the latest conversion value in a plurality of fuel injections. . In this case, the shift of the fuel pressure with respect to the latest conversion value at the timing of one fuel injection of the plurality of fuel injections may be different from the shift with respect to the latest conversion value of the fuel pressure at the timing of injection after the one injection. . For this reason, in the said structure, if the conversion value by a converter is used, it will be a structure where it is difficult to set appropriately the operation amount of the fuel injection valve in each cylinder. For this reason, the said structure becomes a structure which can show | play notably the effect which the said process information has.

  The invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein the internal combustion engine is a multi-cylinder internal combustion engine, and the processing information includes a fuel injection valve and a pressure accumulating chamber of each cylinder. Further comprising information for compensating for a deviation between the fuel pressure in the vicinity of the connection position between the high-pressure fuel passage connecting the fuel injection valve and the fuel injection valve of each cylinder and the fuel pressure in the vicinity of the detection means, and the setting means in the fuel injection, The operation amount is set by reflecting information on the cylinder number in the processing information.

  In the above configuration, the difference between the fuel pressure in the vicinity of the connection position and the fuel pressure in the vicinity of the detection means may be different for each cylinder. For this reason, even if the operation amount is set so as to compensate for the deviation between the fuel pressure in the vicinity of the connection position and the fuel pressure in the vicinity of the detection means for a specific cylinder, depending on the compensation mode, The deviation cannot be compensated appropriately.

  In this regard, in the above configuration, by knowing which cylinder should be compensated for by the cylinder number, it is possible to compensate for the deviation by effectively using the information for compensating the deviation for each cylinder. .

  According to a tenth aspect of the present invention, in the ninth aspect of the invention, the processing information further includes information for compensating for the deviation according to at least one of a temperature of fuel in the pressure accumulating chamber and a rotation angle of the internal combustion engine. It is characterized by that.

  In the above configuration, when the temperature of the fuel in the pressure accumulation chamber changes, the propagation speed of the fuel pressure in the pressure accumulation chamber may change due to the change in the viscosity of the fuel. For this reason, even if the processing information has information for compensating the deviation at a certain temperature, there is a concern that the deviation cannot be compensated with high accuracy by the processing information when the temperature of the fuel is different. . In addition, when the relationship between the fuel injection timing of each cylinder and the fuel pressure supply timing changes according to the rotation angle of the internal combustion engine, the deviation was compensated by a uniform method for each cylinder. Missing compensation cannot be performed with high accuracy.

  In this regard, in the above configuration, the relationship between the fuel injection timing and the fuel pressure supply timing of each cylinder changes according to the rotation angle of the internal combustion engine by using the fuel temperature and the rotation angle to compensate for the deviation. Even if the fuel temperature changes, this can be compensated according to the change in deviation caused by them.

(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 the plunger reciprocates between the top dead center and the 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 pumped fuel is stored in a high pressure state at the common rail 12 and is supplied to the fuel injection valve 16 of each cylinder (here, eight 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 a fuel pressure sensor 20 that detects the fuel pressure in the common rail 12, a fuel temperature sensor 22 that detects the temperature of the fuel in the fuel pump 6, a crank angle sensor 24 that detects the rotation angle of the crankshaft 8, and the like. Various sensors are provided for detecting the operating state of the engine and the operating environment. The engine system also includes an accelerator sensor 26 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) takes in the outputs of the various sensors and controls the output of the diesel engine based on this. Specifically, the ECU 30 includes a central processing unit (CPU 31), a read only memory (ROM 32), a random access memory (RAM 33), an electrically rewritable read only memory (EEPROM 34), and the like. Further, the ECU 30 includes an analog / digital converter (A / D converter 35) for converting the outputs of the various sensors into digital data. The outputs of the various sensors are converted into digital data by the A / D converter 35 and taken into the CPU 31. Thereby, in CPU31, various calculations for the output control of a diesel engine are performed.

  In order to appropriately perform the output control, the ECU 30 performs fuel injection control. Incidentally, in this fuel injection control, in order to feedback control the fuel pressure in the common rail 12 to the target fuel pressure set according to the operating state and operating environment of the diesel engine, the fuel pump 6 (more specifically, the intake metering valve 10). ).

  Here, the fuel injection control performed by the ECU 30 will be further described with reference to FIG. FIG. 2A shows the conversion timing of the output of the fuel pressure sensor 20 by the A / D converter 35 into digital data. FIG. 2B shows the command injection period (valve opening operation period) for the fuel injection valve 16, and FIG. 2C shows the behavior of the fuel pressure in the common rail 12. Further, FIG. 2D shows the transition of the fuel discharge mode by one plunger (first plunger) of the fuel pump 6, and FIG. 2E shows the other plunger (second plunger) of the fuel pump 6. Shows the transition of the fuel discharge mode.

  As shown in the figure, in the present embodiment, conversion by the A / D converter 35 is performed at a “180 ° CA” cycle, fuel is injected at a “90 ° CA” cycle, and at a “144 ° CA” cycle. Fuel is pumped.

  Here, the fuel injection control is performed by setting a command injection period for the fuel injection valve 16 in accordance with the required injection amount. This setting is performed based on the map shown in FIG. In FIG. 3, the injection period is set by the required injection amount and the fuel pressure. For example, when the fuel pressure is constant, the injection period is set longer as the required injection amount is larger. For example, if the required injection amount is constant, the injection period is set shorter as the fuel pressure is higher. By using the map shown in FIG. 3, the command injection period can be set appropriately.

  However, as shown in FIG. 2 above, since the conversion by the A / D converter 35 is “180 ° CA”, even if the conversion value at the latest conversion timing is used to determine the command injection period, The fuel pressure at the start of fuel injection may be significantly deviated from the fuel pressure at the conversion timing. For example, in FIG. 2, the fuel pressure at the start of the command injection period (command injection timing) in the third cylinder is greatly deviated from the fuel pressure immediately before the command injection timing of the seventh cylinder, which is the latest conversion timing. . This is because there is fuel injection of the seventh cylinder and fuel pumping by the fuel pump 6 between the latest conversion timing and the command injection timing of the third cylinder.

  The change in the fuel pressure from the latest conversion timing to the command injection timing is different for each cylinder. That is, for example, the command injection timing of the second cylinder overlaps with the pumping period of the fuel pump 6, but the command injection timing of the third cylinder is immediately after the end of pumping of the fuel pump 6. However, the crank angle interval between the top dead center of each cylinder and the latest conversion timing closest thereto, and the crank angle interval between the top dead center of each cylinder and the top dead center of each fuel pump (top dead center of each plunger) Are constant.

  Therefore, in the present embodiment, the EEPROM 34 is provided with a map shown in FIG. 4 that defines a correction value for calculating the command injection period corresponding to the change in the fuel pressure for each cylinder. Then, at the time of fuel injection of each cylinder, the command injection period calculated by the map shown in FIG. 3 is corrected using the latest conversion value by the correction value determined by the map shown in FIG.

  Further, in the present embodiment, a correction amount for compensating for a deviation between the fuel pressure in the vicinity of the connection position between the fuel injection valve 16 and the high-pressure fuel passage 14 of each cylinder and the fuel pressure in the vicinity of the fuel pressure sensor 20 is added to the correction value. It is included. In other words, since the distance between the fuel pressure sensor 20 and the connection position is different between the cylinders, there is a specific deviation for each cylinder between the fuel pressure detected by the fuel pressure sensor 20 and the fuel pressure in the vicinity of the connection position. Since this deviation is determined by the arrangement position of the fuel pressure sensor 20 and the distance between the fuel pump 6 and the fuel injection valve 16 via the high-pressure fuel passage 14, it is unique to each fuel injection device.

  Note that the process of correcting the command injection period calculated by the map shown in FIG. 3 using the latest conversion value using the map shown in FIG. 4 is performed by the CPU 31 as the process of the program stored in the ROM 32. It is executed by.

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

  (1) The command injection period calculated by the map shown in FIG. 3 is corrected according to the change in the fuel pressure in the common rail 12 during the period from the latest conversion timing of the A / D converter 35 to the command injection timing. did. Thereby, irrespective of the change of the fuel pressure after the conversion timing by the A / D converter 35, the command injection period can be calculated appropriately.

  (2) The conversion cycle by the A / D converter 35 is set longer than the cycle of the fuel injection timing (the timing of the top dead center of each cylinder). As the change in the fuel pressure, the A / D converter 35 The amount of decrease in the fuel pressure in the common rail 12 due to the fuel injection of another cylinder performed from the latest conversion timing to the command injection timing is included. As a result, the subsequent fuel injection (by the command injection period calculated according to the amount of decrease in the fuel pressure by the first injection (in FIG. 2, the first cylinder, the fourth cylinder, the seventh cylinder, the sixth cylinder)) In FIG. 2, since the eighth cylinder, the second cylinder, the third cylinder, and the fifth cylinder) are made, the control accuracy of the subsequent fuel injection can be maintained high.

  (3) As the change in the fuel pressure, the change in the fuel pressure in the common rail 12 due to the fuel pumping from the latest conversion timing by the A / D converter 35 to the command injection timing is included. Thereby, the control accuracy of fuel injection can be maintained high regardless of the change in the fuel pressure due to the pressure feeding.

  (4) By using a map that determines a correction value for correcting the command injection period for each cylinder, the calculation load on the ECU 30 can be reduced when calculating the correction value.

  (5) The correction value shown in FIG. 4 includes a correction amount that compensates for a deviation between the fuel pressure in the vicinity of the connection position between the fuel injection valve 16 and the high-pressure fuel passage 14 of each cylinder and the fuel pressure in the vicinity of the fuel pressure sensor 20. . As a result, the deviation can be compensated for each cylinder.

(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, the latest conversion value is corrected instead of the command injection period. Then, a correction value for correcting the conversion value is variably set in accordance with the latest conversion value and the rotational speed of the crankshaft 8 of the diesel engine in addition to the cylinder number. Specifically, as shown in FIG. 5, the EEPROM 34 is provided with a map that defines the relationship between the cylinder number, fuel pressure (PC), rotational speed (NE), and correction value (ΔPC). Based on the latest conversion value, the rotational speed detected by the crank angle sensor 24, and the cylinder number, the correction value is map-calculated.

  Here, the fuel pressure is a parameter having a correlation with the amount of fuel injected through the fuel injection valve 16 and the amount of fuel pumped from the fuel pump 6. This is because the target fuel pressure in the common rail 12 is normally set based on the injection amount and the rotational speed, and the fuel pressure in the common rail 12 is feedback controlled so as to follow the target fuel pressure thus set. It is. And if the injection quantity and the pumping quantity change, the mode of change of the fuel pressure in the period from the latest conversion timing to the command injection timing may change. On the other hand, the rotational speed is a factor that changes the time from the latest conversion timing to the command injection timing. For this reason, when the rotational speed changes, the time from the latest conversion timing to the command injection timing changes, and as a result, the amount of fuel leaking from the common rail 12 to the low pressure fuel passage 18 via the fuel injection valve 16 may change. . For this reason, in the present embodiment, the correction value is variably set according to not only the cylinder number but also the rotation speed and the fuel pressure.

  According to the present embodiment described above, in addition to the effects according to the above (1) to (5) of the first embodiment, the following effects can be further obtained.

  (6) A correction value is set for each cylinder based on the rotation speed and the latest conversion value. Thereby, it is possible to consider the dependency of the change in the fuel pressure on the rotational speed, the injection amount, and the pumping amount, and thus the command injection period can be calculated by appropriately reflecting the change in the fuel pressure.

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

  In the present embodiment, the process of determining the presence or absence of another fuel injection or the presence or absence of pumping in the period from the latest conversion timing to the command injection timing and calculating the change in fuel pressure due to another fuel injection or pumping is performed.

  FIG. 6 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 S10, the cylinder number for fuel injection is fetched. In the subsequent step S12, the A / D conversion value of the detection value of the fuel pressure sensor 20 is captured. Furthermore, in step S14, it is determined whether or not there is injection in another cylinder during the period from the conversion timing to the command injection timing. For example, in the example shown in FIG. 2 above, it is determined that there is no injection of another cylinder in the period from the latest conversion timing to the command injection timing of the fourth cylinder during the injection of the fourth cylinder. At the time of injection, it is determined that there is another cylinder (4th cylinder) injection in the period from the latest conversion timing to the command injection timing of the 2nd cylinder.

  If it is determined in step S14 that there is injection in another cylinder, the process proceeds to step S16. In this step S16, a command injection amount (required injection amount) of another cylinder is captured. In the subsequent step S18, the amount of decrease in fuel pressure is calculated based on the command injection amount. This amount of decrease in fuel pressure leaks from the high-pressure fuel passage 14 to the low-pressure fuel passage 18 via the fuel injection valve 16 of another cylinder during the injection by the fuel injection valve 16 of another cylinder. This is the amount of decrease in fuel pressure due to the amount of fuel to be used. This may be calculated by map calculation based on the command injection amount, for example.

  On the other hand, when it is determined in step S14 that there is no injection in another cylinder, or when the process of step S18 is completed, the process proceeds to step S20. In step S <b> 20, it is determined whether or not fuel is being pumped from the fuel pump 6 to the common rail 12 during the period from the conversion timing to the command injection timing. For example, in the example shown in FIG. 2, it is determined that there is no pumping in the period from the conversion timing to the command injection timing when the fourth cylinder is injected, and the command injection is performed from the conversion timing when the second cylinder is injected. It is determined that there is pumping in the period up to the time.

  If it is determined in step S20 that there is pumping, the pumping amount is estimated in step S22. This pumping amount is, for example, a dynamic leak amount that flows out from the common rail 12 due to fuel injection, and a static leak that leaks from the high pressure fuel passage 14 to the low pressure fuel passage 18 via the clearance of the fuel injection valve 16 in addition to fuel injection. It can be calculated by adding the fuel amount corresponding to the change in the target fuel pressure to the fuel amount that compensates for the target leak amount. Here, since the fuel amount for compensating the dynamic leak amount is the leak amount compensated by one pumping, it can be calculated as a fuel amount “8/5” times the required injection amount. Further, the amount of fuel that compensates for the static leak amount is a leak amount that is compensated by one pumping, and thus is calculated as a static leak amount in the pumping cycle. The fuel amount corresponding to the change in the target fuel pressure is obtained by multiplying the change amount in the target fuel pressure by the sum V of the volume from the fuel pump 6 to the common rail 12 and the volume of the common rail 12 and dividing by the bulk modulus E. This can be calculated.

  In the subsequent step S24, the change amount of the fuel pressure accompanying the pumping (the change amount of the fuel pressure in the period from the latest conversion timing to the command injection timing) is calculated. Here, first, the pumping start timing is calculated based on the pumping amount estimated in step S22. That is, considering that the pumping start timing is earlier as the pumping amount is larger, the pumping start timing is calculated based on the pumping amount. Actually, the pumping start timing changes according to not only the pumping amount but also the fuel pressure in the common rail 12, the fuel temperature, and the like, so the latest conversion value and the detection value of the fuel temperature sensor 22 are taken into account. The pumping start timing may be calculated. Subsequently, the amount of change in the fuel pressure accompanying the pumping is calculated based on the pumping amount in the period from the pumping start timing to the command injection timing. That is, since the relationship between the rotation angle of the plunger of the fuel pump 6 and the rotation angle of the crankshaft 8 is uniquely determined from these geometric structures, the pumping amount up to the command injection timing is determined geometrically. It is possible to calculate based on a simple structure. Then, when the pumping amount in the period from the pumping start timing to the command injection timing is calculated, the change in the fuel pressure is calculated by multiplying this by the volume elastic modulus E and dividing this by the sum V. Can do.

  When it is determined in step S20 that there is no pumping or when the process of step S24 is completed, the process proceeds to step S26. In step S26, the fuel pressure at the command injection timing is estimated based on the latest converted value by the A / D converter 35 and the amount of change in the fuel pressure calculated in steps S18 and S24 (No in steps S14 and S20). When it is judged, the latest conversion value is used as it is).

  In the subsequent step S28, based on the fuel pressure estimated in step S26, a command injection period is set using the map shown in FIG. 3, and this series of processes is temporarily terminated. In addition, when estimating a fuel pressure in the said aspect, the shift | offset | difference of the fuel pressure near the fuel pressure sensor 20 and the fuel pressure near the connection position of the fuel injection valve 16 and the high pressure fuel passage 14 cannot be compensated. For this reason, in this embodiment, in the map shown in FIG. 4, the correction value is set as a correction amount for compensating for these deviations, and the command injection period calculated based on the estimated fuel pressure is further set for each cylinder. Correction is performed with a correction value calculated by the map.

  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.

(Fourth embodiment)
Hereinafter, the fourth embodiment will be described with reference to the drawings with a focus on differences from the third embodiment.

  In this embodiment, as shown in FIG. 7, a 4-cylinder diesel engine is used, the injection cycle is “180 ° CA”, the discharge cycle is “144 ° CA”, and the conversion cycle by the A / D converter 35 is used. Is “360 ° CA”. In this case, the relationship (crank angle interval) between the top dead center of each cylinder and the pumping timing (or pumping top dead center) of the fuel pump 6 is not uniquely determined. For example, for the first cylinder, the injection timing at the left end in FIG. 7 coincides with the bottom dead center of the plunger, the next injection timing overlaps with the pressure feeding, and the next injection timing is after the pressure feeding. Then, the above three patterns are periodically generated with a period of “1440 ° CA”.

  Even in this case, the command injection period can be set according to the fuel pressure change from the latest timing to the command injection timing by the process shown in FIG. However, in this case, since the relationship between the top dead center of each cylinder and the pressure top dead center of the fuel pump 6 is not uniquely determined, the fuel pressure in the vicinity of the fuel pressure sensor 20, the fuel injection valve 16, and the high-pressure fuel passage 14. Deviation from the fuel pressure in the vicinity of the connection position cannot be properly compensated. That is, since the fuel pressure change in the common rail 12 is caused by the fuel pumping to the common rail 12, the difference between the fuel pressure in the vicinity of the fuel pressure sensor 20 and the fuel pressure in the vicinity of the connection position may vary depending on the fuel pumping condition to the common rail 12. It will be different.

  Therefore, in the present embodiment, as shown in FIG. 8, a correction value is calculated from three parameters of the cylinder number, the fuel temperature, and the crank angle. FIG. 8 shows a three-dimensional map in which correction values are determined by cylinder number, fuel temperature, and crank angle.

  Here, the crank angle is set as an angle within “1440 ° CA”. That is, as described above, the relationship between the top dead center of each cylinder and the pumping top dead center coincide with each other in the “1440 ° CA” cycle, and during this period, these relationships have three patterns. Set a different correction value.

  On the other hand, the temperature of the fuel is a parameter for considering that the viscosity coefficient decreases and the pressure propagation speed changes as the fuel temperature increases. That is, when the pressure propagation speed changes, the manner of deviation between the temperature in the vicinity of the fuel pressure sensor 20 and the temperature in the vicinity of the connection position tends to be different, so that the deviation is accurately compensated regardless of the change in the pressure propagation speed. Therefore, the correction value is variably set based on the fuel temperature.

  According to the present embodiment described above, the following effects can be obtained in addition to the effects of the third embodiment.

  (7) Connection between the fuel injection valve 16 and the high-pressure fuel passage 14 in accordance with the temperature of the fuel in the common rail 12 (more precisely, the temperature of the fuel of the fuel pump 6 detected by the fuel temperature sensor 22) and the crank angle. A correction value that compensates for the difference between the temperature near the position and the temperature near the fuel pressure sensor 20 was calculated. As a result, even if the relationship between the fuel injection timing of each cylinder and the fuel pumping timing changes in accordance with the crank angle or the fuel temperature changes, the deviation caused by them changes. This can be compensated accordingly.

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

  For example, in the first embodiment, instead of providing different correction values for each cylinder, (a) injection immediately after the conversion timing (4th cylinder, 7th cylinder, 6th cylinder, 1st cylinder), ) For each of the second injection (second cylinder, third cylinder, fifth cylinder, and eighth cylinder) after the conversion timing, different correction values may be simply provided.

  In the second embodiment, the fuel pressure is used as a parameter having a correlation with the injection amount or the pumping amount. However, instead of this, the injection amount or the pumping amount itself may be used as a parameter.

  In the second and third embodiments, the latest conversion value is corrected in accordance with the change in fuel pressure from the latest conversion timing to the command injection timing, and the command injection timing is calculated using the corrected conversion value. However, it is not limited to this. For example, the latest conversion value may be corrected according to the change in fuel pressure from the latest conversion timing to the actual injection start timing. This can be performed by using a known method for calculating a map of the delay amount of the injection start timing with respect to the command injection timing based on the interval from the preceding injection to the current injection and the fuel pressure.

  Furthermore, a correction value corresponding to a change in fuel pressure in a period from the latest conversion timing to the setting of the command injection period may be calculated. Here, for example, regarding the change in fuel pressure due to the overlap of the fuel injection period and the pumping period, a map as illustrated in FIG. 3 is provided separately depending on whether the pumping period and the fuel injection period overlap. There are things to deal with. That is, there are various well-known techniques for taking into account the change in the fuel pressure after the calculation of the command injection period. However, in such a well-known technique, when there is a change in the fuel pressure during the period from the latest conversion timing to the calculation of the command injection period, this cannot be appropriately reflected. For this reason, it is effective to correct the conversion value according to the change in the fuel pressure in at least the period from the latest conversion timing to the calculation of the command injection period. That is, after correcting the conversion value according to the change in the fuel pressure in the period from the latest conversion timing to the calculation of the command injection period, the fuel injection is performed while taking into account the change in the fuel pressure after the calculation of the command injection period using a known technique. May be performed.

  In the second and third embodiments, instead of calculating the correction value of the latest conversion value, a correction value for correcting the command injection period calculated based on the latest conversion value may be calculated.

  In the fourth embodiment, the map may be used to calculate a correction value corresponding to the change in fuel pressure in the period from the latest conversion timing to the command injection timing. However, in this case, in each cylinder, a map is set for determining different correction values for each of the three injections within the crank angle period of “1440 ° CA”. Alternatively, a map may be used that determines different correction values for each of “12” fuel injections within the crank angle period of “1440 ° CA”. Further, in addition to the rotation angle, this map may determine a correction value according to the rotation speed and the fuel pressure.

  In the fourth embodiment, the correction value that compensates for the difference between the fuel pressure near the connection position and the fuel pressure near the fuel pressure sensor 20 is set according to the cylinder number, the rotation angle, and the fuel temperature. Not exclusively. In view of the fact that the deviation amount of the fuel pressure also depends on the injection amount and the pumping amount, it is desirable to calculate the correction value based on the fuel pressure as in the second embodiment. Further, the correction value may be calculated based on the injection amount and the pumping amount instead of the fuel pressure.

  The correction value for compensating for the difference between the fuel pressure in the vicinity of the connection position and the fuel pressure in the vicinity of the fuel pressure sensor 20 may be a correction value for the fuel pressure (latest converted value) instead of the correction value for the command injection period.

  In each of the above embodiments, the relationship between the fuel injection timing cycle, the conversion cycle by the A / D converter 35, and the pumping cycle is set to a predetermined integer ratio. As a result, the relationship between the top dead center of each cylinder and the top dead center of pumping (plunger top dead center) coincides with each other at a predetermined crank angle cycle, so that it is easy to calculate a correction value by map calculation. Become. However, even if these do not become a predetermined integer ratio, the change in the fuel pressure in the period from the latest timing to the start of fuel injection can be calculated in the manner shown in FIG.

  -The fuel injection device is not limited to an asynchronous system. For example, even in the case of a synchronous type, when the conversion cycle is longer than the timing of fuel injection, it is effective to calculate the command injection period according to the amount of decrease in fuel pressure due to the injection of another cylinder. .

  The storage means for storing the map data, the program for calculating the correction value based on the map and calculating the fuel pressure based on the map data, and the program for performing the processing shown in FIG. 6 may be changed as appropriate. However, a non-volatile memory that stores and holds the data is desirable regardless of whether or not power is supplied to the fuel injection control device (ECU 30).

  The operation amount of the fuel injection valve 16 is not limited to the command injection period. For example, as described in US Pat. No. 6,520,423, if the fuel injection valve 16 can continuously adjust the lift amount of the nozzle needle in accordance with the displacement of the actuator, the injection period, the fuel pressure, Therefore, the injection amount cannot be determined uniquely. In this case, the operation amount of the fuel injection valve is determined by, for example, the amount of energy applied to the actuator and the period during which energy is applied (injection period), and the injection amount is determined by the fuel pressure, the energy amount, and the injection period. .

  The conversion cycle by the A / D converter 35 is not limited to the crank angle cycle. For example, even if it is a time period, when a plurality of fuel injections occur within the period, the operation amount of the fuel injection valve is calculated according to the change in fuel pressure in the period from the latest conversion timing to the start of fuel injection. It is effective.

  The internal combustion engine is not limited to a diesel engine, and may be, for example, a cylinder injection gasoline engine. Further, the fuel pump 6 is not limited to the one provided with the intake metering valve 10.

The figure which shows the whole structure of the engine system concerning 1st Embodiment. The time chart which shows the aspect of the fuel-injection control concerning the embodiment. The figure which shows the map which calculates an injection period from a fuel pressure and the request | requirement injection quantity in the same embodiment. The figure which shows the map which defines the relationship between the cylinder number and the correction value of a command injection period in the same embodiment. The figure which shows the map which defines the relationship between the correction number of the cylinder number, fuel pressure, rotation speed, and the latest conversion value in 2nd Embodiment. The flowchart which shows the procedure of the process concerning calculation of the command injection period concerning 3rd Embodiment. The time chart which shows the aspect of the fuel-injection control concerning 4th Embodiment. The figure which shows the map which defines the relationship between a cylinder number, fuel temperature, a crank angle, and a correction value in the embodiment.

Explanation of symbols

  6 ... Fuel pump, 12 ... Common rail, 16 ... Fuel injection valve, 30 ... ECU, 35 ... A / D converter.

Claims (10)

A fuel injection device for an in-vehicle internal combustion engine 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. In a fuel injection control device that performs fuel injection control by operating the injection device,
A converter for converting the output of the detecting means for detecting the fuel pressure in the pressure accumulating chamber into digital data at a predetermined conversion cycle;
Calculating means for calculating an operation amount of the fuel injection valve in accordance with a fuel pressure in the pressure accumulating chamber and a required injection amount;
When performing fuel injection control by operating the fuel injection valve, the calculation means calculates the operation amount according to a change in fuel pressure in the pressure accumulating chamber during a period from the latest conversion timing of the converter to the start of the fuel injection. Storage means for storing processing information for performing processing;
A fuel injection control device comprising: setting means for setting the manipulated variable by reflecting information on a conversion value at the latest conversion timing and the timing of fuel injection in the processing information. The conversion cycle is set longer than the cycle of the fuel injection timing,
The change in the fuel pressure includes a decrease amount of the fuel pressure in the pressure accumulating chamber due to another fuel injection performed between the latest conversion timing by the converter and the setting of the operation amount. The fuel injection control device according to claim 1.   The change in the fuel pressure includes a change in the fuel pressure in the pressure accumulating chamber due to the pressurized supply of fuel performed between the latest conversion timing by the converter and the setting of the manipulated variable. The fuel injection control device according to claim 1 or 2. The relationship between the cycle of pressurized fuel supply by the fuel pump, the cycle of the fuel injection timing, and the conversion cycle is set to a predetermined integer ratio; and
The processing information includes a map for determining a correction value for correcting the latest conversion value for each fuel injection within a predetermined period with respect to the rotation angle of the internal combustion engine, and the latest information corrected by the correction value. The fuel injection control device according to claim 1, further comprising information that causes the calculation unit to calculate the operation amount using a conversion value.   5. The fuel injection control according to claim 4, wherein the map sets the correction value for each fuel injection based on at least one of a rotational speed of the internal combustion engine and the latest conversion value. apparatus.   In the fuel injection control by operating the fuel injection valve, the processing information includes information for determining the presence or absence of another fuel injection in a period from the latest conversion timing of the converter to the start of the fuel injection, and the fuel injection Information for calculating the amount of change in the fuel pressure in the pressure accumulating chamber accompanying the fuel injection when it is determined to be present, information for determining the presence or absence of the pressurized supply during the period, and the presence of the pressurized supply The fuel injection control device according to any one of claims 1 to 3, further comprising information for calculating a change amount of a fuel pressure in the pressure accumulating chamber sometimes accompanying the pressurized supply.   The fuel injection control device according to claim 6, wherein the conversion cycle is a rotation angle cycle of the internal combustion engine. The internal combustion engine is a multi-cylinder internal combustion engine;
The fuel injection device is an asynchronous system in which the fuel injection timing and the pressurization supply timing do not correspond one-to-one.
The fuel injection control device according to any one of claims 1 to 7, wherein the conversion cycle is a rotation angle cycle longer than a cycle of the fuel injection timing. The internal combustion engine is a multi-cylinder internal combustion engine;
The processing information compensates for a deviation between a fuel pressure in the vicinity of a connection position between the fuel injection valve of each cylinder and the fuel injection valve in each cylinder and a fuel pressure in the vicinity of the detection means. Have more information,
The fuel according to any one of claims 1 to 8, wherein the setting means sets the operation amount by reflecting information on the cylinder number in the processing information at the time of the fuel injection. Injection control device.   10. The fuel injection control device according to claim 9, wherein the processing information further includes information for compensating for the deviation according to at least one of a temperature of fuel in the pressure accumulating chamber and a rotation angle of the internal combustion engine.

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