JP6431826B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

The present invention relates to a fuel injection control device for an internal combustion engine, for example, a fuel injection control device for an internal combustion engine that can suppress variations in fuel injection amount.

  Conventionally, in a system for fuel injection, fuel is supplied by a plurality of fuel injections (multistage injection) from a fuel injection device having a fuel injection valve that is electromagnetically driven in a cylinder 1 operation cycle of an internal combustion engine to a combustion chamber. Has been done.

  In such a fuel injection device, the boosting power source is generally composed of a boosting circuit including an inductive element and a switching element, and a capacitor for storing boosted power. When the fuel injection valve is energized from the boosting power source, power is supplied by discharging from the capacitor. For this reason, when a current is supplied from the boosting power source, the voltage of the capacitor drops due to discharging.

  The capacitor is charged by the booster circuit after discharging and returns to the boosted predetermined voltage. However, when multiple injections are performed in a relatively short time, the charge is not in time for the second and subsequent injections. Sometimes.

  For example, in Patent Document 1, the boosted voltage obtained by boosting the battery voltage is monitored by an engine controller unit, and when the boosted voltage drops below a set normal voltage, the valve opening time Pi of the fuel injection valve is extended and fuel injection is performed. A structure that secures the drive current necessary for the valve operation realizes a highly reliable fuel injection system by performing the maximum number of injections that can be performed for the required number of injections even when the boosted voltage drops. doing.

JP 2011-185157 A

  However, in a fuel injection device for an internal combustion engine, the demand for multi-stage injection is increasing year by year. On the other hand, for the purpose of purifying exhaust gas, it is possible to inject fuel in a short period so that the boosted voltage cannot be charged in time. It has been demanded. If the next injection is performed before the charging of the boosted voltage is completed, the suction energy of the plunger of the fuel injection valve decreases due to insufficient boosted voltage, delaying the opening of the fuel injection valve, and the variation in the injection amount increases. . In particular, in the low injection pulse region, this influence is significant, and correction control is required to suppress variations in the injection amount due to valve opening delay.

  In addition, when performing injection such that the injection timings are close to each other during multi-stage injection, delaying the injection timing in order to secure the charging time of the boosted voltage makes it possible to achieve both engine output, exhaust gas purification, and fuel efficiency improvement at a high level. Even if the required injection timing is set for this purpose, fuel injection may not be executed at a desired timing.

The present invention has been made in view of such a problem, and the object of the present invention is when a short-term injection is required such that the injection timing is close and the charge of the boost voltage is not in time. Another object of the present invention is to provide a fuel injection control device for an internal combustion engine that can satisfy a demand for a desired injection timing and suppress variation in fuel injection amount due to injection of boosted voltage during charging.

To achieve the above object, a fuel injection control apparatus for an internal combustion engine according to the present invention boosts the driving voltage of the fuel injection valve for injecting fuel into a combustion chamber of an internal combustion engine to high reference voltage than the voltage of the battery a fuel injection control device for an internal combustion engine having a booster circuit, a voltage estimating means for estimating a voltage increase amount is boosted by the booster circuit with estimating the amount of voltage drop of the reference voltage to lower the fuel injection, Correction amount calculation means for calculating a correction amount for correcting the fuel injection amount at the time of fuel injection based on the voltage drop amount and the voltage increase amount obtained by the voltage estimation means.

  According to the present invention, the fuel injection amount can be corrected in accordance with the estimated boosted voltage even when the boosted voltage of the booster circuit drops below the set reference voltage due to multi-stage injection. Variations in the fuel injection amount can be suppressed without shifting the injection timing.

1 is an overall configuration diagram of an internal combustion engine including an embodiment of a fuel injection control device for an internal combustion engine according to the present invention. The control block diagram which shows the engine control unit of FIG. The control block diagram of the fuel-injection control apparatus of this invention. The timing chart which showed the relationship between the drive current of the fuel injection valve, the boost voltage, and the boost recovery time. The timing chart which shows an example of the request | requirement operation | movement at the time of multistage injection. The timing chart which shows the other example of the request | requirement operation | movement at the time of multistage injection. The timing chart which shows the further another example of the request | requirement operation | movement at the time of multistage injection. The timing chart which shows the relationship between the battery voltage and the reset reference time of a boost voltage. 4 is a timing chart showing a relationship between a boosted voltage estimated value and a boosted voltage estimated correction amount according to the present invention. The flowchart of the fuel-injection control by this invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a fuel injection control device for an internal combustion engine according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows a basic configuration of an internal combustion engine system provided with a fuel injection control device according to the present invention.

  In FIG. 1, the internal combustion engine 1 includes a piston 2, an intake valve 3, and an exhaust valve 4 in a cylinder. The fuel injection valve 5 directly injects fuel into the combustion chamber in the cylinder, and the cylinder head is provided with an ignition plug 6 and an ignition coil 7. The water jacket of the cylinder is provided with a coolant temperature sensor 8. Air sucked into the internal combustion engine 1 passes through an AFM (Air Flow Meter) 20 and is sucked in the order of a throttle valve 19 and a collector 15, and then an intake pipe 10 and an intake valve 3 provided in each cylinder. To be supplied to the combustion chamber 21.

  On the other hand, fuel is sent from a fuel tank 23 to a high-pressure fuel pump 25 provided in the internal combustion engine 1 by a low-pressure fuel pump 24, and the high-pressure fuel pump 25 is based on a control command value from an ECU (Engine Control Unit) 9. The pressure is controlled to a desired pressure. Thus, the high pressure fuel is sent to the fuel injection valve 5 through the high pressure fuel pipe 29, and the fuel injection valve 5 supplies the fuel to the combustion chamber based on a command from the fuel injection valve control device 27 provided in the ECU 9. It injects into 21.

  The internal combustion engine 1 is provided with a fuel pressure sensor 26 for measuring the pressure in the high-pressure fuel pipe 29 in order to control the high-pressure fuel pump 25, and the ECU 9 determines the fuel in the high-pressure fuel pipe 29 based on this sensor value. So-called feedback control is performed so that the pressure becomes a desired pressure. Further, the internal combustion engine 1 is provided with the ignition coil 7 and the ignition plug 6, and the ECU 9 is configured to perform energization control on the ignition coil 7 and ignition control by the ignition plug 6 at a desired timing. .

  As a result, the intake air and the fuel are combusted by the spark emitted from the spark plug 6 in the combustion chamber 21. The exhaust gas generated by the combustion is discharged to the exhaust pipe 11 through the exhaust valve 4, and a three-way catalyst 12 for purifying the exhaust gas is provided in the middle of the exhaust pipe. An oxygen sensor 13 for detecting the oxygen concentration in the exhaust gas is installed upstream of the three-way catalyst 12.

  The ECU 9 includes the fuel injection control device 27 described above, and detects a crank angle sensor 16 that measures a crankshaft (not shown) angle of the internal combustion engine 1, an AFM 20 that indicates the intake air amount, and an oxygen concentration in the exhaust gas. Signals such as an oxygen sensor 13 that performs the operation, an accelerator opening sensor 22 that indicates the opening of the accelerator operated by the driver, and a fuel pressure sensor 26 are input.

  The signal input from each sensor will be further described. The ECU 9 calculates the required torque of the internal combustion engine 1 from the accelerator opening signal of the accelerator opening sensor 22, and determines whether or not the engine is in an idle state. . The ECU 9 also includes a rotation speed detection means for calculating the rotation speed (hereinafter referred to as engine rotation speed) of the internal combustion engine 1 from the signal of the crank angle sensor 16, the cooling water temperature of the internal combustion engine 1 obtained from the water temperature sensor 8, and the internal combustion engine. Means or the like is provided for determining whether or not the three-way catalyst 12 is in a warmed-up state from the elapsed time after the start.

  Further, the ECU 9 calculates the intake air amount necessary for the internal combustion engine 1 from the above-described required torque, and outputs an opening signal corresponding to the intake air amount to the throttle valve 19, and the fuel injection control device 27 responds to the intake air amount. The calculated fuel amount is calculated, a fuel injection signal is output to the fuel injection valve 15, and an ignition signal is output to the ignition coil 17. The exhaust pipe 11 and the collector 15 are connected by an EGR (exhaust gas recirculation) passage 18, and an EGR valve 14 is provided in the middle of the EGR passage 18. The opening degree of the EGR valve 14 is controlled by the ECU 9, and the exhaust gas in the exhaust pipe 11 is recirculated to the intake pipe 10 and recombusted.

  Next, the ECU 9 will be described with reference to FIG. FIG. 2 shows a control block diagram of the ECU 9. The fuel injection control device 27 is built in the ECU 9 and includes a microcomputer 34, a driver IC 45, a booster circuit 41, an upper driver 42, and a lower driver 43.

  The battery voltage from the battery 31, which is a vehicle power supply, is supplied to the ECU 9 to be supplied to the power supply IC 33, the driver IC 45 of the fuel injection control circuit 27, the booster circuit 41 for driving the fuel injection device, the upper driver 42, and the like. Is done. The voltage from the power supply IC 33 is supplied to a microcomputer 34, a driver IC 45, etc. as control means. The booster circuit 41 boosts the driving voltage of the fuel injection valve 5 to a reference voltage higher than the voltage of the battery 31, and the voltage is raised to about 65 volts, which is higher than 12 volts of the battery voltage.

  The driver IC 45 of the fuel injection control device 27 includes a communication unit 39 with the microcomputer 34, a booster circuit drive unit 40, and a driver drive unit 38, and sends a switching signal from the booster circuit drive unit 40 to the booster circuit 41. The boosted voltage is supplied to the upper driver 42. Further, the voltage boosted by the booster circuit 41 is fed back to the booster circuit drive unit 40 of the driver IC 45, and the driver IC 45 thereby determines whether or not to send a switching signal again.

  The voltage boosted by the booster circuit 41 is fed back to the A / D converter 35 of the microcomputer 34, and the microcomputer 34 can send a signal to the driver IC 45 from the communication unit 36 based on the A / D value. . The microcomputer 34 can input and monitor signals from a fuel pressure sensor and a temperature sensor (including the ambient temperature of the ECU 9, the substrate temperature, and the temperature of the booster circuit) in addition to the boosted voltage via the A / D converter 35. is there. In addition to this, the microcomputer 34 has an input / output port 32 for driving an external load and monitoring an external signal. The microcomputer 34 includes a ROM and a RAM (not shown), and has a function of storing set values and the like.

  The microcomputer 34 includes the fuel injection control unit 28 as a component thereof. Specifically, as shown in FIG. 3, the voltage at which the reference voltage decreases when the fuel injection valve 5 injects fuel. In addition to estimating the amount of decrease, voltage estimation means 52 for estimating the amount of voltage increase boosted by the booster circuit 41 is incorporated. Further, the microcomputer 34 includes a correction amount calculation unit 53 that calculates a correction amount for correcting the fuel injection amount at the time of fuel injection based on the voltage drop amount and the voltage increase amount obtained by the voltage estimation unit. .

  The upper driver 42 of the fuel injection control device 27 has a boosted voltage driver 42 a that drives the coil load 44 by the boosted voltage of the booster circuit 41 and a battery voltage driver 42 b that drives the coil load 44 by the battery voltage from the battery 31. The upper driver 42 supplies a current to a coil load 44 such as a fuel injection valve having an electromagnetic coil by the driving signal A and the driving signal B of the driver driving unit 38 of the driver IC 45. The drive signal A triggers the boosted voltage driver 42a by the boosted voltage, and the drive signal B triggers the battery voltage driver 42b by the battery voltage. Further, the lower driver 43 causes the current from the coil load 44 to flow to the ground potential by the drive signal C of the driver drive unit 38.

  At least one of the upper driver 42 and the lower driver 43 has a current detection unit and a terminal voltage detection unit using a shunt resistor or the like, and driver drive control for detecting and feeding back the current value flowing through the driver and the coil load 44 It is carried out. Also, it is possible to detect an overcurrent to the driver, a terminal power supply fault, and a ground fault with these functions.

  Here, in this embodiment, the booster circuit 41, the upper driver 42, and the lower driver 43 are provided separately from the driver IC 45, but these may be provided inside the driver IC 45. That is, the driver IC 45 may be used as either a driver or a pre-driver.

  FIG. 3 relates to the fuel injection control unit 28 of the fuel injection valve according to the present invention, and shows an example of a control block diagram for correcting the fuel injection pulse width by the estimated boosted voltage. The fuel injection timing calculation means 51 is a means for calculating the fuel injection timing, and calculates the injection timing for each cylinder based on conditions such as the engine speed, engine water temperature, and injection stroke information. The boost voltage estimation means 52 is a boost voltage monitored by the boost circuit driver 40 from the fuel injection timing for each cylinder, the ambient temperature of the ECU 9, the substrate temperature of the ECU 9, the temperature of the boost circuit, the battery voltage, or the battery voltage smoothed value. As a starting point, the boosted voltage is estimated and the boosted voltage estimated value is calculated. Specifically, the voltage drop amount of the fuel injection valve that decreases due to fuel injection is estimated, and the voltage increase amount of the fuel injection valve that is boosted by the booster circuit 41 is estimated. A method of calculating the boost voltage estimated value will be described later.

  The boosted voltage estimated correction amount calculation means 53 calculates a correction amount based on the boosted voltage estimated value so as to suppress fuel variation due to the boosted voltage drop. The basic control value calculation means 54 calculates a basic control value according to conditions such as engine speed, load, and engine water temperature. In the fuel injection pulse width calculating means 55, the fuel correction amount based on the boosted voltage estimated value calculated by the boosted voltage estimating means 52 and the corrected amount calculating means 53 described later, which is a feature of the present invention, with respect to the basic control value. And the injection pulse width is calculated. When performing multistage injection, the pulse width for injecting multiple times according to the number of multistage injections and the division ratio is calculated. The fuel injection valve driving means 56 is a means for driving the fuel injection valve 9, and outputs a drive current to the fuel injection valve 5 to inject fuel according to the fuel injection timing and the fuel injection pulse width. Run.

Next, calculation of the boosted voltage drop amount per one drive of the fuel injection valve and the drop time will be described with reference to FIG. FIG. 4 is a timing chart showing the relationship between the drive current of the fuel injection valve, the boosted voltage, and the boost return time. In this waveform, the electric charge consumed when one fuel injection valve is driven is indicated by the area of ΔQ (401), and ΔQ can be calculated by the following equation (1) from dt (402) and ip (403).
ΔQ = dt × ip / 2 (1)

  dt (402) is the time from when the drive current of the fuel injection valve flows until the peak current is reached, and is equivalent to the drop time ΔT (404) of the boosted voltage (Vboost). The dt (402) is set by any two or more of the battery voltage, the battery voltage smoothed value, the ambient temperature of the ECU, the substrate temperature of the ECU, or the temperature of the booster circuit. Here, the battery voltage smoothing value is obtained by suppressing the fluctuation of the battery voltage by applying a weighted average filter to the battery voltage.

  ip (403) is the peak current of the fuel injection valve, and is preset as the valve opening current I peak according to the fuel pressure used. In the fuel injection valve drive current waveform, the rising portion indicates the effective pulse width w1, and the falling portion and the injection current I hold extending flatly indicate the invalid pulse width w2. In the present invention, the correction amount for correcting the fuel injection amount extends or shortens the invalid pulse width w2 to suppress variations in the fuel injection amount. When the amount of voltage drop due to fuel injection is larger than the amount of voltage rise by the booster circuit 41, the drive voltage is lower than the reference voltage. In this case, it is possible to extend the valve opening time by extending the ineffective pulse width by extending the injection current, thereby increasing the fuel injection amount and suppressing variations in the fuel injection amount.

Further, from the charge calculation formula (Q = CV), the boost voltage drop amount ΔV (405) per one fuel injection valve drive can be calculated by the following formula (2) (ΔV is called the boost voltage drop amount).
ΔV = ΔQ / C (2)

The capacitance C is determined according to the capacitor used in the booster circuit 41. However, since the capacitor includes variations due to temperature, it is preferable to correct the capacitance by a temperature sensor. According to the charge calculation formula, when two fuel injection valves are driven simultaneously, the consumed charge ΔQ (401) is doubled, and the boost voltage drop amount ΔV (405) is also doubled. Further, dtc (406) is the boost voltage recovery time, and the current (ic) charged in the boost circuit can be calculated by the following equation (3).
ic = ΔQ / dtc (3)

From the charge calculation formula, the above formula can be converted into the following formula (4).
ΔV = ic × dtc / C (4)

  When the charged current (ic) and the capacitance (C) are fixed values, when the boost voltage drop amount ΔV (405) doubles, the boost voltage recovery time: dtc (406) also doubles. Become.

  Here, the preset power consumption amount described in the claims represents a boost voltage drop amount ΔV (405) and a drop time ΔT (404) each time fuel is injected per one fuel injection valve drive. By calculating the amount of power consumption, the amount of decrease in the boosted voltage when driving one fuel injection valve can be estimated, and the reference voltage may be estimated by decreasing by a predetermined value. Further, the amount of power supplied when one fuel injection valve is driven represents an increase (recovery) amount ΔV (405) of the boost voltage and a boost voltage return time dtc (406).

  FIG. 5 is a timing chart showing an example of the required operation during multistage injection. The timing chart shows the injection pulse width, the fuel injection valve current waveform, and the boosted voltage (Vboost) in order from the top, and the case where multistage injection of the same cylinder is performed three times during a predetermined period (507 to 508) of 180 deg. The requested operation will be described as an example. When the power is turned on, the boosted voltage (Vboost) is boosted to the reference voltage 501 and is held constant at the reference voltage 501.

  Further, as indicated by the solid line 502 of the boosted voltage, the voltage drops by a predetermined amount per injection at the timing (time point) of the first injection (503), the second injection (504), and the third injection (505), and thereafter Is boosted toward the reference voltage 501. If the boosted voltage returns to the reference voltage 501 as in the second injection timing 504, a stable fuel injection amount can be injected. However, as in the third injection timing 505, the boosted voltage (Vboost) is the reference. If the next injection is performed before the charging to the voltage 501 is completed, the suction energy of the plunger of the fuel injection valve decreases due to insufficient boosted voltage, delaying the opening of the fuel injection valve, and the injection amount variation becomes large. In particular, this effect is significant in the low injection pulse region, and correction control that suppresses variations in the injection amount due to valve opening delay is necessary. In addition, when performing injection such that the injection timings are close to each other during multi-stage injection, delaying the injection timing in order to secure the charging time of the boosted voltage makes it possible to achieve both engine output, exhaust gas purification, and fuel efficiency improvement at a high level. Even though the required injection timing is set for this purpose, fuel injection cannot be executed at a desired timing.

  Therefore, in order to cope with the case where the next injection is performed before the boosted voltage (Vboost) is charged up to the reference voltage 501 as in the timing 505 for the third injection, the timing 505 before driving the fuel injection valve is 2 By calculating from the time difference (Δt1) between the second injection start time 504 and the third injection start time 505, the voltage drop of the boost voltage for the second injection and the boost voltage at the third injection timing 505 are estimated.

  Since the boosted voltage estimated at the third injection timing 505 is estimated to be lower than the reference voltage 501, the current waveform of the fuel injection valve is also corrected 506b by extending the injection pulse width as shown by the hatched portion of the correction 506a. The hatched portion shown in FIG. 6 is extended, and variations in the fuel injection amount can be suppressed. Although the details of the method for estimating the boost voltage will be described later, the present invention can satisfy the demand of the desired injection timing when short-term injection is required so that the charge of the boost voltage is not in time. The fuel injection amount variation due to the injection during charging can be suppressed.

  FIG. 6 is a timing chart showing another example different from that shown in FIG. 5 as the requested operation during multi-stage injection. The timing chart shows, in order from the top, the injection pulse width, the current waveform of the fuel injection valve, and the boosted voltage (Vboost), and the case where multistage injection of the same cylinder is performed twice during a predetermined period (607 to 608) of 180 deg. The requested operation will be described as an example. When the power is turned on, the boosted voltage (Vboost) is boosted to the reference voltage 601 and is held constant at the reference voltage 601. Also, as indicated by the solid line 602 of the boosted voltage, the voltage drops by a predetermined amount per injection at the timing 605 of the first injection during the first injection 603, the second injection 604, and the next 180 deg predetermined period (608 to 609). Thereafter, the voltage is boosted toward the reference voltage 601. If the boosted voltage returns to the reference voltage 601 as in the second injection timing 604, a stable fuel injection amount can be injected. However, as in the first stroke injection 605, the boosted voltage (Vboost) If the next injection is performed before the charging is completed up to the reference voltage 601, the suction energy of the plunger of the fuel injection valve decreases due to insufficient boosted voltage, delaying the opening of the fuel injection valve, and variation in the injection amount increases. .

  Therefore, in order to cope with the case where the next injection is performed before the boosted voltage (Vboost) is charged to the reference voltage 601 as in the timing 605 of the first injection in the next stroke, the timing 605 before driving the fuel injection valve. Thus, when there is a decision REF interruption 608 for the injection timing 604 between the second injections of the previous stroke injection, the boosted voltage and the injection timing decision point 608 measured at the injection timing decision point 608 and the first injection timing 605 after the decision. , The boost voltage at the first injection timing 605 after the determination is estimated.

  Of course, by calculating from the time difference (Δt3) between the second injection timing 604 and the first injection timing 605 after confirmation, the voltage drop of the boost voltage for the second injection and the boost voltage at the first injection timing 605 after confirmation Can also be estimated. Thus, the voltage increase amount at the current injection timing can be estimated from the elapsed time from the previous injection timing and the boosting characteristic by the booster circuit, and the calculation load of the microcomputer 34 can be reduced.

  Since the estimated boosted voltage at the first injection timing 605 after the determination is estimated to be lower than the reference voltage 601, the current waveform of the fuel injection valve is extended by extending the injection pulse width as shown by the hatched portion of the correction 606a. In addition, the hatched portion shown in the correction 606b is extended, and variations in the fuel injection amount can be suppressed.

  FIG. 7 is a timing chart showing an example different from those shown in FIGS. 5 and 6 as the required operation during multi-stage injection. The timing chart shows, from the top, (A) n cylinder injection pulse width, (B) n cylinder fuel injection current waveform, (C) n + 1 cylinder injection pulse width, (D) n + 1 cylinder fuel injection current waveform, (E) The boosted voltage (Vboost) is shown. This figure shows a case in which multi-stage injection is performed three times within a stroke of a crank angle of 180 deg in a predetermined period (705 to 706) and once in the next stroke in a combination of different cylinders (A) and (C). ing. The rising edge of the first injection pulse is shifted by (Δt4) from the rising edge of the second and third injection pulses, and the rising edge of the fourth injection pulse is shifted from the BTDC 10 deg by (Δt5) after a large delay. .

  When the first injection and the second injection, the second injection and the third injection are close to each other, and (E) the next injection is executed before the boosted voltage (Vboost) is charged to the reference voltage 701, the solid line 702 As shown, the boosted voltage is further lowered at the second injection from the first injection and at the third injection from the second injection. When the boosted voltage at the time of fuel injection is lower than the reference voltage 701, the fuel injection amount decreases. Therefore, the fuel with the injection pulse width at the hatched portions indicated by the correction 703a for the second injection and the correction 704a for the third injection The increase correction is performed according to the boosted voltage estimated value. In this case, since the boost voltage of the third injection is lower than that of the second injection, the time w4 of the third injection correction 704a is set longer than the time w3 of the correction 703a of the second injection. Along with this correction of the injection pulse width, the hatched portions indicated by the correction 703b of the current waveform (D) 703b and the correction 704b of the current waveform (B) of the fuel injection valve are extended, and variations in the fuel injection amount can be suppressed. In the fourth injection, since the boosted voltage has returned to the reference voltage 701, correction for the injection pulse width of the fourth injection is not performed.

  Next, the details of the method of calculating the boosted voltage estimated value in the present invention will be described. In the present embodiment, the estimated boosted voltage value is calculated by determining the time difference between the previous injection start time and the current injection start time (the timing difference between 503 and 504 in FIG. 5 and the timing difference between 504 and 505) or when the injection timing is determined. Estimate the boost voltage at the time of injection from the time-time difference from REF to the first injection (the timing difference between 603 and 607 and the timing difference between 605 and 608 in FIG. 6), the boost voltage recovery time, the supplied power amount, and the consumed power amount. To do. The estimated boost voltage is calculated by the following formula.

C1, when the boosted voltage measured at the injection timing determination time is not used C2, the injection voltage determination REF is interrupted between the nth injection and the (n + 1) th injection using the boosted voltage measured at the injection timing determination time. When C3, the boosted voltage actually measured at the time when the injection timing is determined is used, and there is no interruption of the determination REF of the injection timing between the nth injection and the n + 1th injection

In the case of C1 or C3 above,
Boost voltage estimated value = boosted voltage at the start of previous injection−post-injection boost voltage drop amount + post-injection boost voltage drop amount × (boosted voltage return time−dt (402)) / (recovery reference time−dt (402)) · (5)

In the case of C2 above,
Boosted voltage estimated value = boosted voltage monitored when injection timing is determined + post-injected boosted voltage drop amount × (boosted voltage return time−dt (402)) / (recovery reference time−dt (402)) (6) )

  However, the maximum value of the estimated boosted voltage has the reference voltage as the upper limit. The estimated boosted voltage value for the initial fuel injection after the vehicle power source (battery) is turned on or the initial fuel injection after idle stop is used as the reference voltage. By making the maximum value of the boosted voltage estimated value the upper limit of the reference voltage, it is possible to avoid erroneous calculation of the microcomputer 34. By using the estimated boosted voltage value for the initial fuel injection after idle stop as the reference voltage, the estimated number of times of the reference voltage measurement can be increased, and a highly accurate estimated value can be calculated even when the idle stop vehicle is restarted.

  The reference voltage in the present embodiment is a boosted voltage monitored after the initial power-on of the vehicle power source (battery) and before fuel injection or after idle stop and before fuel injection, and is stored in the microcomputer 34. In the boost voltage estimated value calculation formula, the boost voltage recovery time is calculated by the following formula.

In the case of C1 or C3 above,
Boosted voltage recovery time = Injection n + 1 injection timing−Injection nth injection timing (7)

In the case of C2 above,
Boosted voltage recovery time = Injection n + 1 first injection timing−Injection timing determination timing (8)

  In order to correctly correct the variation in fuel injection amount during multi-stage injection, it is necessary to grasp the amount of boost voltage drop in real time. It is several ms, and monitoring in real time is not preferable because the calculation load of the microcomputer increases. For this reason, when using the boosted voltage monitored when the injection timing is determined, the boosted voltage in the booster circuit drive unit 40 described above is set before a predetermined period in this embodiment (507 and 508 in FIG. 5, and in FIG. 6). (Timing of 607, 608, 609), A / D (analog signal to digital signal conversion) and capture for each cylinder. The measured value of the boosted voltage is hereinafter referred to as a boosted voltage AD value.

  Further, in the formula for calculating the boost voltage estimated value, the return reference time is set to the actual value of the boost voltage reference return time. The boost voltage recovery reference time will be described with reference to FIG.

  FIG. 8 is a chart showing the relationship (boost characteristic) between the battery voltage and the return reference time of the boost voltage. A curve 801 indicates a case where the ECU board temperature is high, and a curve 802 indicates a case where the ECU board temperature is low. This indicates that the boosted voltage recovery time becomes longer as the battery voltage becomes lower and the ECU board temperature becomes higher. Although the ECU substrate temperature is used here, any one or more of the ambient temperature of the ECU and the temperature of the booster circuit may be used. Further, although the battery voltage is used here, it may be a battery voltage smoothed value. With the means described so far, an estimated value of the boosted voltage can be obtained.

Next, a means for calculating the injection pulse width and the boost voltage estimation correction will be described. The boost voltage estimation correction is calculated at the start of the current injection.
Injection pulse width by cylinder = basic control value × division ratio × fuel pressure correction coefficient + invalid pulse width + boosted voltage estimation correction (9)

  Here, the basic control value is a value calculated by the basic control value calculation means 54 of FIG. 3, and the division ratio is a ratio of the value calculated by the basic control value calculation means 54 to the current injection, and the fuel pressure correction. The coefficient is a correction coefficient based on the fuel injection pressure at the start of the current injection.

  The boosted voltage estimation correction is a correction amount calculated by the boosted voltage estimated correction amount calculating means 53, and the fuel injection amount is reduced as the amount of drop with respect to the reference voltage due to the boosted voltage being injected during charging increases. Since the amount also increases, it is set so as to suppress a decrease in the fuel injection amount, and is calculated as a pulse width by the fuel injection pulse width calculation means 55. A specific setting example is shown in FIG.

  FIG. 9 is an example of a chart (boost characteristic) for setting the boost voltage estimation correction amount according to the boost voltage estimated value according to the present invention. A solid line 901 is a boost voltage estimation correction amount. As the boost voltage becomes lower than the reference voltage, the correction amount is increased to extend the fuel injection pulse width. On the other hand, in the region where the boost voltage is higher than the reference voltage 903, the correction amount This is an example in which the correction amount is set so as to reduce the fuel injection pulse width by decreasing the. A dotted line 902 indicates that in the state where the boosted voltage is charged near the reference voltage 903, the boosted voltage estimation correction amount is invalidated and the injection pulse width is not extended or reduced. In this embodiment, since the boosted voltage estimation correction is corrected by adding or subtracting to the injection pulse width, “0” is substantially invalid.

  FIG. 10 is a flowchart of the fuel injection control according to the present invention. This flow is calculated by interruption every fuel injection.

  In step S1001, input parameters such as the above-described Vboost reference voltage, BTDC boost voltage AD value, ECU substrate temperature, ECU ambient temperature, boost circuit temperature, battery voltage, and battery voltage annealing value are captured. In step S1002, it is determined whether or not the first injection after the start. The first injection for the idle stop restart is also defined as the first injection. In the case of the first injection, the process proceeds to step S1003, where the Vboost reference voltage is the estimated boosted voltage value at the time of the first injection. When the condition of step S1002 is not satisfied, that is, when it is not the first injection, the process proceeds to step S1004, and it is determined whether or not the BTDC boost voltage AD value is required.

  When using the BTDC boost voltage AD value in step S1004, the process proceeds to step S1005 to determine whether there is a BTDC interruption between the previous injection and the current injection. When there is an interruption, the process proceeds to step S1006, where the boosted voltage AD value at BTDC is measured and set as the boosted voltage value at the previous injection. When the BTDC boost voltage AD value in step S1004 is not used, and when there is no interruption in step S1005, the process proceeds to step S1007 to calculate the boost voltage value at the time of the current injection. Next, in step S1008, an estimated value of the boost voltage at the current injection is calculated from the boost voltage value at the time of the current injection, the boost voltage return time, and the like.

  In the calculation of the boost voltage estimated value of the current injection in step S1008, the ECU substrate temperature, the ambient temperature of the ECU, the temperature of the boost circuit, the battery voltage, or the battery voltage smoothing value is used. Sets the boost voltage recovery reference time. A highly accurate estimated value can be calculated by using two or more parameters with which the boost voltage varies.

In step S1009, a boost voltage estimation correction amount as shown in FIG. 9 is calculated from the boost voltage estimation value of the current injection. In step S1010, the fuel injection pulse width is calculated by reflecting the boost voltage estimation correction amount in the basic control value. Next, in step S1011, the calculated fuel injection pulse width and fuel injection timing are set in the driver IC 45 of the fuel injection control device 27, and the driver IC 45 outputs a driving current to control the fuel injection valve 5.

  From the above, when a short-term injection that does not allow the boosted voltage to be charged in time is required, the invalid pulse width w2 of the fuel injection pulse width (w1 + w2) can be extended to satisfy the desired injection timing requirement. Thus, it is possible to suppress variations in the fuel injection amount due to the boosted voltage being injected during charging. Since the calculation of the boost voltage estimation correction amount in S1009 is calculated individually for the fuel injection, a highly accurate estimated value can be obtained.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, for example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described.

  In addition, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files that realize each function can be stored in a storage device such as a memory, a hard disk, or an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, or a DVD.

  Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  As an application example of the present invention, in addition to an internal combustion engine for automobiles, it can be applied to an internal combustion engine for other purposes.

1: internal combustion engine (engine), 5: fuel injection valve, 9: ECU (engine control unit), 27: fuel injection control device, 28: fuel injection control unit, 31: battery (power source for vehicle), 32: input / output Port: 33: Power supply IC, 34: Microcomputer, 38: Driver drive unit, 40: Boost circuit drive unit, 41: Boost circuit, 42a: Boost voltage driver, 42b: Battery voltage driver, 44: Coil load (fuel injection valve 5 ), 45: Driver IC (fuel injection control device), 51: Fuel injection timing calculation means, 52: Boost voltage estimation means (voltage estimation means), 53: Boost voltage estimation correction amount calculation means (correction amount calculation means), 55 : Fuel injection pulse width calculation means 56: fuel injection valve driving means

Claims (9)

A fuel injection control device for an internal combustion engine having a booster circuit that boosts the driving voltage of the fuel injection valve for injecting fuel into a combustion chamber of an internal combustion engine to high reference voltage than the voltage of the battery,
A voltage estimating means for estimating a voltage increase amount is boosted by the booster circuit with estimating the amount of voltage drop of the reference voltage to lower the fuel injection, the voltage drop amount and the voltage increase amount obtained by the voltage estimating means and a correction amount calculating means for calculating a correction amount for correcting the fuel injection quantity of fuel injection based on,
Said voltage estimating unit, based on the power consumption amount set in advance each time the fuel injection per drive of the fuel injection valve one, characterized that you estimate the voltage drop amount the reference voltage is lowered a predetermined value A fuel injection control device for an internal combustion engine. A fuel injection control device for an internal combustion engine having a booster circuit that boosts the driving voltage of the fuel injection valve for injecting fuel into a combustion chamber of an internal combustion engine to high reference voltage than the voltage of the battery,
A voltage estimating means for estimating a voltage increase amount is boosted by the booster circuit with estimating the amount of voltage drop of the reference voltage to lower the fuel injection, the voltage drop amount and the voltage increase amount obtained by the voltage estimating means and a correction amount calculating means for calculating a correction amount for correcting the fuel injection quantity of fuel injection based on,
The reference voltage, the internal combustion engine fuel injection control apparatus characterized by boosted voltage and to Rukoto actually measured before power after and fuel injection of the battery or before idle stop after fuel injection. The fuel for an internal combustion engine according to claim 1 or 2 , wherein the voltage estimation means estimates the amount of voltage increase at the current injection time based on an elapsed time from the previous injection time and a boosting characteristic by the boosting circuit. Injection control device. 3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the voltage estimation unit estimates the voltage increase amount with the reference voltage as an upper limit. 4. The boost characteristic, the temperature of the substrate temperature or the booster circuit, the ambient temperature or control apparatus, the battery voltage or the battery voltage moderated value, or the control unit, is set by any two or more, characterized in Rukoto The fuel injection control device for an internal combustion engine according to claim 3. The correction amount for the fuel injection, the fuel injection control apparatus for an internal combustion engine according to claim 1 or 2, characterized in Rukoto calculated separately. The correction amount, when the boost voltage is lower than the reference voltage, the invalid pulse width relating to the opening time of the fuel injection valve extends, and corrected characterized Rukoto to extend the fuel injection pulse width The fuel injection control device for an internal combustion engine according to claim 1 , 2 or 6. The correction amount, when the boosted voltage is higher than the reference voltage, reduces the invalid pulse width relating to the opening time of the fuel injection valve is corrected so as to shorten the fuel injection pulse width and said Rukoto The fuel injection control device for an internal combustion engine according to claim 1 , 2 or 6. The voltage estimation means estimates a boost voltage at the current injection time from a voltage measured at a predetermined timing between a previous injection time and a current injection time, an elapsed time from the predetermined timing, and a boost characteristic by the booster circuit. The fuel injection control device for an internal combustion engine according to claim 1 or 2 .

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