JP2009057867A - Fuel injection control device and fuel injection system using the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for highly accurately correcting an injection quantity of rear-stage injection in the whole use range area of an interval time of multistage injection. <P>SOLUTION: A shape of a reference injection characteristic is not changed by a machine difference or a change with the lapse of time of a fuel injection valve, but since an initially-set valve closing delay time Tde1 and a valve opening delay time Tds1 vary as Tde2 and Tds2 as indicated in signs 210 and 212, a phase difference indicated in (ΔINT1+ΔINT2) is generated between a point 220 of a target interval time and a point 222 of an actual interval time. Even if the interval time varies by a machine difference or the change with the lapse of time, since an actual injection characteristic varies only in a phase of the interval time of the reference injection characteristic, a phase difference between the reference injection characteristic and actually measured actual injection characteristic data is calculated, and the injection quantity of the rear-stage injection is corrected by the reference injection characteristic corrected by being shifted by an amount of the phase difference. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection control device that controls an injection amount of a fuel injection valve that performs multi-stage injection in one combustion cycle, and a fuel injection system using the same.

  In a common rail type fuel injection system, multistage injection is performed in which pilot injection, post injection, and the like are performed before and after the main injection that generates main torque for the purpose of reducing combustion noise or regenerating an exhaust filter. .

  Thus, in a multi-stage injection type fuel injection valve that injects fuel multiple times during one combustion cycle, pressure pulsation is generated by a water hammer effect when the fuel injection valve is closed and the injection is terminated in each stage. Since the magnitude of the pressure pulsation changes depending on the elapsed time from the end of each stage of injection, if a pressure pulsation occurs due to the preceding stage in multistage injection, the subsequent stage injection amount to be injected following the preceding stage injection It varies depending on the interval time from the end of injection to the start of subsequent injection.

Therefore, it is conceivable to measure the characteristics of the interval time and pressure pulsation in advance at the time of shipment and set a reference correction map for correcting the injection amount with respect to the interval time.
However, since the injection characteristics of the fuel injection valve vary due to machine differences or changes with time for each fuel injection valve, a deviation occurs between the target interval time and the actual interval time set in the reference correction map. As a result, even if the injection amount of the post-injection at the target interval time is corrected based on the reference correction map, the post-injection amount deviates from the target injection amount.

Therefore, in Patent Document 1, an actual injection amount when multi-stage injection is performed is calculated, and an attempt is made to learn a difference in interval time due to machine difference or temporal change based on the difference between the actual injection amount and the target injection amount.
JP 2007-132334 A

  However, in Patent Document 1, learning is performed on the interval time in a part of the usage range in which the post-stage injection is performed over the entire range of use of the interval time, and applied to the part of the usage range in which the learned time gap is learned. is doing. As a result, it is necessary to newly learn a gap in the interval time in another usage range within the entire usage range of the interval time.

  On the other hand, as shown in FIG. 7, the actual injection amount 200 is measured by performing two-stage injection at the front stage and the rear stage at the detection points in the entire use range of the interval time. It is conceivable to learn the change in the injection amount of the post-injection due to the pressure pulsation with respect to the interval time in the entire use range from the difference between the total injection amount of the pre-stage and the post-stage that has been measured.

  Since the upstream and downstream injection amounts are measured by single-stage injection, the reference injection amount 202 is an injection amount that is not affected by pressure pulsation. In order to learn the change in the injection amount of the post-stage injection due to the pressure pulsation, the injection quantity in the pre-stage and the post-stage may be the same, and twice the measured single-stage injection quantity may be set as the reference injection quantity. In this case, the actual injection amount is a measured value of the injection amount in which the same injection amount is commanded at the front stage and the rear stage and the two-stage injection is performed.

  However, since the measurement of the single-stage injection quantity and the two-stage injection quantity includes an error, the difference in the injection quantity between the actual injection quantity 200 including the error and the reference injection quantity 202 causes the post-stage injection due to the pressure pulsation with respect to the interval time. When learning the change in the injection amount, there is a problem that the learning accuracy is lowered.

  The present invention has been made to solve the above-described problem, and a fuel injection control device that accurately corrects the injection amount of the subsequent injection in the entire use range of the interval time of the multi-stage injection, and a fuel injection system using the same The purpose is to provide.

  As shown in FIG. 6 (A), the present inventor, even if the command injection amount is different and the injection rate during injection and the internal pressure of the fuel injection valve (INJ) are different, It was found that the change in pressure, that is, the characteristics of pressure pulsation, is almost the same as the elapsed time from the end of injection.

Then, as shown in FIG. 6B, the present inventor shows that the characteristic of the injection amount of the rear (second stage) injection that changes due to the pressure pulsation generated at the end of the front stage injection in the multi-stage injection is It has been found that even if the injection amount of the injection is different, the injection end timing of the front injection and the command injection amount of the rear injection are the same with respect to the interval time if they are the same. In FIG. 6B, the interval when the injection amount of the front-stage injection is changed to, for example, 50 mm ³ / st, 10 mm ³ / st, and 2 mm ³ / st, and the command injection amount of the rear-stage injection is set to 2 mm ³ / st. The characteristic of the injection quantity of the latter stage injection with respect to time is shown. That is, the variation in the injection characteristic with respect to the interval time due to machine difference or change over time is only the variation in the interval time due to the variation in the on-off valve delay time of the fuel injection valve. Therefore, the injection characteristic with respect to the interval time is only shifted in phase of the reference injection characteristic.

  Therefore, in the inventions according to claims 1 to 6, the interval time between the reference injection characteristic with respect to the interval time in the entire use range of the interval time between the pre-stage injection and the post-stage injection and the actual injection characteristic data with respect to the actually acquired interval time. And the injection amount of the subsequent injection is corrected based on the reference injection characteristic corrected by shifting the calculated phase difference.

  As a result, if the reference injection characteristics are measured with high accuracy, even if the injection characteristics of the fuel injection valve vary due to machine differences or changes over time by shifting the phase difference of the reference injection characteristics, The injection amount of the subsequent injection can be corrected with high accuracy.

According to the second aspect of the present invention, since the reference injection characteristics are stored as a map, the reference injection characteristics can be acquired from the map in a short time.
In the invention according to claim 3, since the reference injection characteristic is stored as a mathematical expression, the storage capacity for storing the reference injection characteristic is reduced.

  As in the invention according to claim 4 or 5, the reference injection characteristic and the actual injection characteristic data may represent a relationship between the interval time and the correction value of the injection amount of the post-stage injection, or the interval time and the pre-stage injection and You may represent the relationship with the total injection quantity of back | latter stage injection.

  The functions of the plurality of means provided in the present invention are realized by hardware resources whose functions are specified by the configuration itself, hardware resources whose functions are specified by a program, or a combination thereof. The functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
A fuel injection system according to an embodiment of the present invention is shown in FIG.
(Fuel injection system 10)
A fuel injection system 10 according to one embodiment of the present invention is shown in FIG.

  The accumulator fuel injection system 10 includes a feed pump 14, a high pressure pump 16, a common rail 20, a pressure sensor 22, a fuel injection valve 30, an electronic control unit (ECU) 40, and the like. Fuel is injected into each cylinder of the diesel engine 60.

  The feed pump 14 sucks fuel from the fuel tank 12 and supplies it to a high-pressure pump 16 that is a fuel supply pump. The high-pressure pump 16 is a known pump that pressurizes fuel sucked into a pressurizing chamber by a plunger reciprocatingly moved by a drive shaft interlocked with rotation of the crankshaft 66. By controlling the current value supplied to the metering valve 18 of the high-pressure pump 16 by the ECU 40, the fuel suction amount that the high-pressure pump 16 sucks in the suction stroke is metered. Then, by adjusting the fuel intake amount, the fuel discharge amount of the high-pressure pump 16 is adjusted.

  The common rail 20 accumulates fuel pumped by the high-pressure pump 16 and holds the fuel pressure at a predetermined high pressure according to the engine operating state. The pressure sensor 22 detects the fuel pressure inside the common rail 20 and outputs it to the ECU 40.

  The fuel injection valve 30 is installed in each cylinder of the four-cylinder diesel engine 60, and injects the fuel accumulated in the common rail 20 into the cylinder. The fuel injection valve 30 performs multistage injection including pilot injection, post injection, and the like before and after main injection that generates main torque in one combustion cycle of a diesel engine.

  As shown in FIG. 2, the fuel injection valve 30 is a known electromagnetically driven valve that controls the fuel injection amount by controlling the pressure in the control chamber 100 that applies fuel pressure to the nozzle needle 32 in the valve closing direction. . High pressure fuel is supplied from the common rail 20 to the periphery of the injection hole 34 of the fuel injection valve 30 and to the control chamber 100.

  In the state shown in FIG. 2 in which the control valve 36 blocks communication between the control chamber 100 and the low pressure side, the nozzle needle 32 closes the nozzle hole 34 by the fuel pressure applied from the control chamber 100 to the nozzle needle 32. .

  When the control valve 36 causes the control chamber 100 to communicate with the low pressure side, the amount of fuel flowing out from the control chamber 100 to the low pressure side becomes larger than the amount of fuel flowing into the control chamber 100 from the common rail 20. descend. As a result, the nozzle needle 32 is lifted and fuel is injected from the injection hole 34.

  As shown in FIG. 1, a microcomputer 50 mounted on an ECU 40 as a fuel injection control device includes a rewritable nonvolatile memory such as a CPU 52, a ROM 54, a RAM 56, and an EEPROM 58, various input / output ports, and the like. . A control program that causes the ECU 40 to function as an actual injection characteristic acquisition unit, a phase difference calculation unit, a phase correction unit, and an injection correction unit, and a reference injection characteristic for the interval time are stored in a storage device such as a ROM 54 or an EEPROM 58. Yes. The reference injection characteristics may be stored as a map, or may be stored as a mathematical expression such as an approximate expression. In the case of a map, the reference injection characteristics can be acquired in a short time. In the case of the mathematical formula, the storage capacity for storing the reference injection characteristics becomes small.

  The ECU 40 determines the operating state of the diesel engine 60 from detection signals of various sensors such as an accelerator sensor that detects the opening (ACC) of the accelerator pedal, a temperature sensor, a pressure sensor 22, and an NE sensor that detects the engine speed (NE). get. The ECU 40 controls energization to the metering valve 18 and the fuel injection valve 30 based on the acquired engine operating state in order to control the diesel engine 60 to an optimal operating state.

  The ECU 40 controls the injection timing and the injection amount of each stage of the fuel injection valve 30 that performs multi-stage injection according to the engine operating state obtained from various sensors including the pressure sensor 22. The ECU 40 outputs a pulse signal as an injection command signal for controlling the injection timing and the injection amount of the fuel injection valve 30.

  The piston 64 accommodated in the cylinder 62 of the diesel engine 60 so as to be reciprocally movable is reciprocally driven when the fuel injected from the fuel injection valve 30 into the combustion chamber 110 burns and expands. The piston 64 is connected to the crankshaft 66 through a connecting rod 65. As the piston 64 reciprocates, the crankshaft 66 rotates.

  The inflow of intake air into the combustion chamber 110 is controlled by opening and closing the intake valve 70, and the exhaust discharged from the combustion chamber 110 is controlled by opening and closing the exhaust valve 74. The intake valve 70 and the exhaust valve 74 are driven to open and close by rotation of cams provided on the cam shafts 72 and 76.

(Change in injection amount due to pressure pulsation)
As shown in FIG. 3, when the fuel injection valve 30 is closed in the multi-stage injection and the pre-stage injection is completed, pressure pulsation is generated in the fuel in the fuel injection valve 30 by the water hammer action. Since this pressure pulsation is transmitted to the common rail 20 as well, the injection timing of the subsequent injection changes depending on the magnitude of the pressure pulsation. As a result, the injection amount of the subsequent injection changes depending on the magnitude of the pressure pulsation.

  Further, as shown in FIG. 4, a valve closing delay occurs in the closing of the pre-injection of the fuel injection valve 30 with respect to the falling timing of the drive current that is the injection command signal, and with respect to the rising timing of the driving current. A valve opening delay occurs in the opening of the subsequent injection of the fuel injection valve 30. Therefore, the target interval time (target INT) is set in consideration of the valve closing delay time Tde1 and the valve opening delay time Tds1 with respect to the command interval time (command INT) between the front injection and the rear injection commanded by the drive current. It is necessary. The target interval time is expressed by the following equation (1).

Target INT = command INT−Tde1 + Tds1 (1)
However, since the initial valve closing delay time Tde1 and the valve opening delay time Tds1 vary as Tde2 and Tds2 as indicated by reference numerals 210 and 212 due to machine differences or changes with time of the fuel injection valve 30, the target interval time and the actual interval A time difference represented by (ΔINT1 + ΔINT2), that is, a phase difference occurs between the time and the time. As a result, if the post-injection injection amount is corrected at the target interval time point 220 without considering machine differences and changes over time, the post-injection injection amount is corrected at a point different from the actual interval time point 222 to be corrected. Will do.

  As described above, even if the command injection amount for the front stage injection is different and the injection rate during the injection and the internal pressure of the fuel injection valve 30 are different, the pressure pulsation characteristics are the interval time from the end of the front stage injection to the start of the rear stage injection. Is almost the same.

  The characteristic of the injection amount of the subsequent injection that changes due to the pressure pulsation is that the injection end timing of the preceding injection and the command injection amount of the subsequent injection are the same with respect to the interval time even if the injection amount of the preceding injection is different. Are almost identical. Therefore, even if the interval time varies due to machine differences or changes over time, the actual injection characteristic with respect to the interval time is only the phase of the reference injection characteristic shifted. Therefore, it is considered that the phase difference between the reference injection characteristic and the actually measured actual injection characteristic data is calculated, and the injection amount of the subsequent stage injection is corrected by the reference injection characteristic corrected by shifting the phase difference.

(Each means of ECU40)
The ROM 54 or EEPROM 58 of the ECU 40 functions as storage means for storing reference injection characteristics described below. The ECU 40 functions as the following units according to a control program stored in a storage unit such as the ROM 54 or the EEPROM 58.

(1) Storage means In one combustion cycle, the correction value of the injection amount of the post-injection with respect to the entire use range of the interval time is the reference in the entire use range of the interval time between the pre-stage injection and the post-stage injection injected following the pre-stage injection. The ejection characteristics are stored in the ROM 54, the EEPROM 58 or the like. The correction value for the injection amount of the post-stage injection is a correction value for the falling timing of the injection command pulse width of the drive current that controls the injection quantity of the post-stage injection. Since the length of the injection command pulse width is changed by changing the falling timing of the injection command pulse width of the drive current, the injection amount of the post-stage injection is changed. The reference injection characteristics are initially set when the fuel injection valve 30 is shipped.

(2) Actual injection characteristic acquisition means The ECU 40 determines that the learning condition is satisfied if the accelerator-off non-injection deceleration operation is being performed, and at a plurality of interval time points in a part of the interval time use range. Subsequent injection is carried out following pre-injection and pre-injection, and an actual injection amount that is a total injection amount by two-stage injection of the pre-injection and the post-injection is measured. The ECU 40 detects a change in the engine speed due to the two-stage injection, converts the engine speed into engine torque, and further converts it into an injection quantity to measure the actual injection quantity. The ECU 40 calculates a correction value for the falling timing of the injection command pulse width of the drive current for controlling the injection amount of the subsequent injection from the actual injection amount measured at each point of the interval time, and calculates the actual injection characteristic data. Get as.

(3) Phase difference calculation means The ECU 40 calculates the phase difference between the reference injection characteristic and the actual injection characteristic data.
(4) Phase correction means The ECU 40 corrects the reference injection characteristic by shifting the reference injection characteristic toward the calculated phase difference and actual injection characteristic data.

(5) Injection correction means The ECU 40 corrects the injection amount of the subsequent injection based on the reference injection characteristic corrected by shifting the phase difference.

(Interval time phase difference learning)
Next, phase difference learning between the reference injection characteristic and the actual injection characteristic with respect to the interval time will be described with reference to FIG. In FIG. 5, “S” represents a step. The learning routine shown in FIG. 5 is always executed during operation of the diesel engine 60.

  In S300, the ECU 40 determines whether or not a non-injection deceleration operation is being performed when the accelerator is off as a phase difference learning condition. If the learning condition is not satisfied, the ECU 40 ends this routine.

  When the learning condition is satisfied, the ECU 40 performs the post-injection subsequent to the pre-injection for each interval time point, and measures the total injection amount of the pre-stage and the post-stage as the actual injection amount. Then, the ECU 40 calculates, for each measurement point, a correction value for the falling timing of the injection command pulse width of the drive current for controlling the injection amount of the post-stage injection from the actual injection amount measured at each interval time point. Obtained as characteristic data.

In S304, the ECU 40 calculates a phase difference between the reference injection characteristic stored in the ROM 54 or the EEPROM 58 and the acquired actual injection characteristic data.
In S306, the ECU 40 corrects the calculated phase difference and reference injection characteristic by shifting to the actual injection characteristic data side, and ends this routine.

The ECU 40 corrects the injection amount of the post-stage injection when performing the multi-stage injection based on the reference injection characteristic shifted in phase difference.
As described above, in this embodiment, even if the interval time varies due to machine differences or changes over time, the deviation of the reference injection characteristic with respect to the interval time is not the deviation of the offset direction, period, amplitude, etc., but only the phase direction. I focused on that. Then, by shifting the reference injection characteristic with respect to the interval time in the entire range of use of the interval time by the phase difference from the actual injection characteristic data and correcting the post-injection amount, the post-injection of the post-injection can be accurately performed over the entire use range of the interval time. The injection amount can be corrected.

[Other Embodiments]
In the above-described embodiment, the injection amount of the post-stage injection is corrected by correcting the falling timing of the injection command signal for the post-stage injection and correcting the injection pulse width. On the other hand, the injection amount of the post-stage injection may be corrected by correcting only the injection timing without changing the pulse width of the injection command signal for the post-stage injection.

  Moreover, in the said embodiment, the correction value of the injection quantity of the back | latter stage injection with respect to interval time was employ | adopted as reference | standard injection characteristic and actual injection characteristic data. On the other hand, you may employ | adopt the total injection quantity of the front | former stage injection and back | latter stage injection with respect to interval time as a reference | standard injection characteristic and real injection characteristic data.

Further, in the multi-stage injection, the front stage injection and the rear stage injection may be combined in any way.
As described above, the present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

The block diagram which shows the fuel-injection system by this embodiment. The typical sectional view showing the composition of a fuel injection valve. Explanatory drawing explaining generation | occurrence | production of a pressure pulsation. The time chart explaining the gap | interval of interval time. The flowchart which shows a phase difference learning routine. (A) shows the relationship between the elapsed time after the end of injection, the injection rate, and the pressure in the fuel injection valve, and (B) is a time chart showing the relationship between the interval time and the injection amount of the post-stage injection. The time chart which shows the relationship between the interval time measured in the whole use range, and the injection quantity.

Explanation of symbols

10: fuel injection system, 16: high pressure pump (fuel supply pump), 20: common rail, 30: fuel injection valve, 40: ECU (fuel injection control device, storage means, actual injection characteristic acquisition means, phase difference calculation means, phase Correction means, injection correction means), 54: ROM (storage means), 58: EEPROM (storage means), 60: Diesel engine (internal combustion engine)

Claims (6)

In a fuel injection control device that controls an injection amount of a fuel injection valve that performs multi-stage injection during one combustion cycle,
Storage means for storing reference injection characteristics with respect to the interval time in the entire use range of the interval time between the preceding injection and the subsequent injection that is injected following the preceding injection;
Actual injection characteristic acquisition means for acquiring actual actual injection characteristic data for the interval time;
A phase difference calculating means for calculating a phase difference between the reference injection characteristic and the actual injection characteristic data with respect to the interval time;
Phase correction means for correcting the reference injection characteristic by shifting the phase difference;
Injection correction means for correcting the injection amount of the post-stage injection based on the corrected reference injection characteristics;
A fuel injection control device comprising:   The fuel injection control apparatus according to claim 1, wherein the storage means stores the reference injection characteristic as a map.   The fuel injection control apparatus according to claim 1, wherein the storage means stores the reference injection characteristic as a mathematical expression.   The said reference | standard injection characteristic and the said actual injection characteristic data represent the relationship between the said interval time and the correction value of the injection quantity of the said back | latter stage injection, The Claim 1 characterized by the above-mentioned. Fuel injection control device.   The said reference | standard injection characteristic and the said actual injection characteristic data represent the relationship between the said interval time and the total injection quantity of the said front stage injection and the said back | latter stage injection, The Claim 1 characterized by the above-mentioned. The fuel injection control device described. A fuel supply pump that pressurizes and pumps fuel; and
A common rail for accumulating fuel pumped by the fuel supply pump;
A fuel injection valve for injecting fuel accumulated in the common rail into a cylinder of an internal combustion engine;
A fuel injection control device according to any one of claims 1 to 5,
A fuel injection system comprising:

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