JP2014031790A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device of an internal combustion engine capable of calculating estimated valve opening timing which approximates actual valve opening timing of a fuel injection valve through a relatively simple operation.SOLUTION: A fuel injection control device of an internal combustion engine: obtains a first approximation line LA1 by using electric current values ID1 and ID2 sampled at first and second time points tS1 and tS2 which are set anterior to a range of normal valve opening timing of a fuel injection valve; obtains a second approximation line LA2 by using the electric current values ID3 and ID4 sampled at third and fourth time points tS3 and tS4 which are set posterior to the range of the normal valve opening timing; and calculates estimated valve opening timing tAOPE which approximates actual valve opening timing of the fuel injection valve by obtaining the time point corresponding to an inflection point of current change characteristics through identification of an intersection of the first approximation line LA1 and the second approximation line LA2.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and in particular, a fuel injection that controls the amount of fuel supplied into a combustion chamber by electromagnetically opening and closing a fuel injection valve that injects fuel directly into the combustion chamber of the internal combustion engine. The present invention relates to a control device.

  Patent Document 1 discloses a method for monitoring the operation of a solenoid valve. According to this method, the valve opening start timing of the solenoid valve is detected at the time when the rate of change of the current change line representing the time change of the drive current of the solenoid valve changes from positive to negative.

JP 2005-61583 A

  In a fuel injection valve that directly injects fuel into the combustion chamber of an internal combustion engine, the pressure of the pressurized fuel and the biasing force of the spring are applied to the valve body in the valve closing direction. The actual valve opening operation is started with a delay from the supply start time. Therefore, in order to increase the control accuracy of the fuel injection amount, it is effective to detect the actual opening timing of the fuel injection valve and correct the valve opening command signal in accordance with the detected actual opening timing.

  Since the structure of the electromagnetic valve disclosed in Patent Document 1 is different from the structure of the fuel injection valve, the drive current change characteristic is different from the drive current change characteristic of the fuel injection valve. Therefore, even if the method disclosed in Patent Document 1 is applied as it is, the actual opening timing of the fuel injection valve cannot be obtained.

  The present invention has been made paying attention to this point, and it is possible to calculate the estimated valve opening timing that approximates the actual valve opening timing of the fuel injection valve that directly injects fuel into the combustion chamber by a relatively simple calculation. An object of the present invention is to provide a fuel injection control device for an internal combustion engine.

  In order to achieve the above object, a first aspect of the present invention is a fuel injection valve (2) for directly injecting fuel into a combustion chamber of an internal combustion engine (1), which is closed by the pressure of the fuel and the biasing force of a spring. A fuel injection valve (2) comprising a valve body (32) biased in the valve direction and an electromagnetic actuator (35, 36, 38, 39) biasing the valve body in the valve opening direction; A valve opening command signal output means for outputting a valve opening command signal for driving the electromagnetic actuator, in a fuel injection control device for an internal combustion engine that controls the amount of fuel supplied to the combustion chamber by opening and closing through the valve; The drive at a predetermined timing during a current increase period from the supply start time (tIS) of the drive current (ID) of the electromagnetic actuator to the time (tSW) at which the drive current becomes maximum. Based on the sampling means for sampling the flow value (ID (k)) and the sampling value (ID (k)) by the sampling means, the valve element (32) is in the valve seat (37) during the current increase period. An inflection point acquiring means for acquiring a time point (tAOPE) corresponding to an inflection point (PX) in the change characteristic of the drive current, which appears by moving away from the vehicle, and a time point corresponding to the inflection point as the fuel injection valve. And an estimated valve opening timing calculating means for calculating an estimated valve opening timing (tAOPE) that approximates the actual valve opening timing.

  According to this configuration, the value of the drive current is sampled at a predetermined timing during the current increase period from the start of supplying the drive current of the electromagnetic actuator to the time when the drive current becomes maximum, and the current is determined based on the sampled value. A time point corresponding to the inflection point that appears when the valve body of the fuel injection valve moves away from the valve seat during the increase period is acquired, and the time point corresponding to the inflection point approximates the actual opening timing of the fuel injection valve. Calculated as the estimated valve opening time. In a fuel injection valve that directly injects fuel into the combustion chamber, the solenoid's inductance decreases and the current increase rate changes as the relative position of the solenoid and the movable member that displaces the valve element in the valve opening direction in the electromagnetic actuator changes. Increases relatively remarkably. Therefore, the estimated valve opening timing can be calculated by acquiring the time corresponding to the inflection point by a relatively simple calculation.

  According to a second aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first aspect, the sampling means has elapsed a first time (TS1) from the start of supplying the drive current (ID) of the electromagnetic actuator. The first time point (tS1), the second time point (tS2) that has passed the second time (TS2) from the first time point (tS1), and the third time point that has passed the third time (TS3) from the second time point (tS2) (TS3) and the fourth time point (tS4) after the fourth time (TS4) from the third time point (tS3), the value of the drive current is sampled, and the first and second time points are sampled. First approximate line acquisition means for obtaining a first approximate line (LA1) that approximates the current change characteristic from the first time point to the second time point using the first and second current values (ID1, ID2); 3 And a second approximate line (LA2) that approximates the current change characteristic from the third time point to the fourth time point using the third and fourth current values (ID3, ID4) sampled at the fourth time point. 2 approximate line acquisition means, and the estimated valve opening timing calculation means corresponds to a point of time corresponding to the intersection of the first approximate line (LA1) and the second approximate line (LA2) to the inflection point. Calculated as a time point (tAOPE), the second time point (tS2) is set to a time point before the normal valve opening timing range of the fuel injection valve, and the third time point (tS3) is set from the normal valve opening time range. It is set at a later time, and the fourth time (tS4) is set at a time before the time when the drive current becomes maximum.

  According to this configuration, the first approximate straight line is obtained using the current values sampled at the first and second time points set before the normal opening timing range of the fuel injector, and the normal opening timing range is set. A second approximate line is obtained using the current values sampled at the third and fourth time points set later, and the time corresponding to the intersection of the first approximate line and the second approximate line is the actual value of the fuel injection valve. It is calculated as an estimated valve opening time that approximates the valve opening time. Therefore, since an estimated valve opening timing that approximates the actual valve opening timing can be obtained by an approximate calculation using four sampling data, an expensive high-speed sampling circuit becomes unnecessary, reducing costs and reducing the load on the arithmetic unit. can do.

  According to a third aspect of the present invention, in the fuel injection control apparatus for an internal combustion engine according to the second aspect, the intermediate failure range (a1NGL) set outside the range in which the slope (a1) of the first approximate straight line is normal. ≦ a1 <a1THNL, a1THNH <a1 ≦ a1NGH) First intermediate failure determination means for determining that the fuel injection valve (2) is in an intermediate failure state, and inclination (a1) of the first approximate straight line Is a complete failure range (a1 <a1NGL, a1> a1NGH) set outside the intermediate failure range, and further includes first complete failure determination means for determining that the fuel injection valve is in a complete failure state. The valve opening command signal output means supplements the valve opening command signal (TINJCMD) according to the determined failure state when it is determined that the fuel injection valve is in the intermediate failure state. Characterized in that it.

  According to this configuration, when the slope of the first approximate line is in the intermediate failure range set outside the normal range, it is determined that the fuel injection valve is in the intermediate fault state, and the slope of the first approximate line is Is in the complete failure range set outside the intermediate failure range, it is determined that the fuel injection valve is in a complete failure state, and when it is determined that the fuel injection valve is in an intermediate failure state, it is determined The valve opening command signal is corrected according to the failure state. Therefore, a failure determination corresponding to the failure degree of the fuel injection valve can be performed, and in the intermediate failure state, the valve opening command signal is corrected according to the failure state, so that the fuel injection amount deviates from a desired value. Can be suppressed.

  According to a fourth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the second aspect, the inclination (a1) of the first approximate line and the inclination (a2) of the second approximate line are compared. The method further comprises first failure determination means for determining failure of the fuel injection valve.

  According to this configuration, the failure determination of the fuel injection valve is performed by comparing the slope of the first approximate line and the slope of the second approximate line. If the fuel injection valve is normal, the slope of the second approximate line is larger than the slope of the first approximate line by a predetermined value or more, so that failure determination can be easily made based on the difference between the two slopes.

  According to a fifth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the fourth aspect, the valve opening command signal output means is configured such that the slope (a1) of the first approximate line is the slope of the second approximate line ( When smaller than a2), the valve opening command signal (TINJCMD) is corrected according to the slope (a2) of the second approximate straight line.

  According to this configuration, when the slope of the first approximate line is smaller than the slope of the second approximate line, the valve opening command signal is corrected according to the slope of the second approximate line. When the slope of the first approximate straight line is smaller than the slope of the second approximate straight line, the fuel injection valve is normal or in an intermediate failure state, and when it is in the intermediate failure state, the deviation amount of the slope of the second approximate straight line Greatly contributes to the fuel injection amount, so that the deviation of the fuel injection amount can be suppressed by performing the correction according to the deviation amount.

  According to a sixth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first aspect, the inflection point acquiring means uses the sampling value (ID (k)) to calculate the integral value (SAID) of the driving current. (k)) and an integral value change amount calculating means for calculating the change amount (DSAID (k)) of the integral value, and the integral value change amount (DSAID (k)). The time point corresponding to the inflection point is determined from the time point when it is determined that is equal to or greater than a predetermined amount (DSAIDTH).

  According to this configuration, the integral value of the electromagnetic actuator drive current is calculated, the change amount of the integral value is further calculated, and the time point corresponding to the inflection point is determined from the time when the integral value change amount is determined to be equal to or greater than the predetermined amount. Since the determination is made, the time corresponding to the inflection point can be obtained by a relatively simple calculation.

  A seventh aspect of the invention is the internal combustion engine fuel injection control apparatus according to the first aspect of the invention, wherein the inflection point obtaining means calculates the sampling value change amount (DID (k)). A quantity calculating means is provided, and a time point corresponding to the inflection point is determined from a time point when the sampling value change amount (DID (k)) is determined to be equal to or greater than a predetermined amount (DIDTH).

  According to this configuration, the change amount of the sampling value is calculated, and the time point corresponding to the inflection point is determined from the time point when the change amount of the sampling value is determined to be equal to or greater than the predetermined amount. The time corresponding to the music point can be acquired.

  According to an eighth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the sixth or seventh aspect, the time point (tAOP) corresponding to the inflection point from the supply start time (tIS) of the drive current of the electromagnetic actuator. ) And a first slope calculating means for calculating a first slope (a1) that is a slope of a straight line approximating the current change characteristic in the period up to and including the first slope (a1). Second intermediate failure determination means for determining that the fuel injection valve is in an intermediate failure state when the intermediate failure range (a1NGL ≦ a1 <a1THNL, a1THNH <a1 ≦ a1NGH), and the first inclination is the intermediate failure A second complete failure determination that determines that the fuel injection valve is in a complete failure state when it is within a complete failure range (a1 <a1NGL, a1> a1NGH) set outside the range. And the valve opening command signal output means, when it is determined that the fuel injection valve is in the intermediate failure state, the valve opening command signal output signal for the fuel injection valve according to the determined failure state. (TINJCMD) is corrected.

  According to this configuration, the first slope that is the slope of the straight line that approximates the current change characteristic in the period from the start of supplying the drive current of the electromagnetic actuator to the time corresponding to the inflection point is calculated, and the first slope is calculated. When the fuel injection valve is determined to be in an intermediate failure state when in the intermediate failure range set outside the normal range, and the first slope is in the complete failure range set outside the intermediate failure range When the fuel injection valve is determined to be in a complete failure state and the fuel injection valve is determined to be in an intermediate failure state, the fuel injection valve opening command signal is corrected according to the determined failure state. The Therefore, a failure determination corresponding to the failure degree of the fuel injection valve can be performed, and in the intermediate failure state, the valve opening command signal is corrected according to the failure state, so that the fuel injection amount deviates from a desired value. Can be suppressed.

  According to a ninth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the eighth aspect, the current from the time point (tAOP) corresponding to the inflection point to the time point (tSW) at which the drive current becomes maximum. By comparing the first inclination (a1) and the second inclination (a2) with the second inclination calculating means for calculating the second inclination (a2), which is the inclination of the straight line approximating the change characteristic, the fuel The apparatus further comprises second failure determination means for determining a failure of the injection valve.

  According to this configuration, the second slope (a2) that is the slope of a straight line that approximates the current change characteristic from the time point (tAOP) corresponding to the inflection point to the time point (tSW) at which the drive current becomes maximum is calculated. By comparing the first inclination (a1) and the second inclination (a2), a failure of the fuel injection valve is determined. If the fuel injection valve is normal, the second inclination is larger than the first inclination by a predetermined value or more, so that failure determination can be easily performed based on the difference between both inclinations.

  According to a tenth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the ninth aspect, the valve opening command signal output means has the first inclination (a1) smaller than the second inclination (a2). In this case, the valve opening command signal for the fuel injection valve is corrected in accordance with the second inclination (a2).

  According to this configuration, when the first inclination is smaller than the second inclination, the valve opening command signal of the fuel injection valve is corrected according to the second inclination. When the first slope is smaller than the second slope, the fuel injection valve is normal or in an intermediate failure state, and when it is in the intermediate failure state, the deviation amount of the second inclination greatly contributes to the fuel injection amount. Therefore, by performing the correction according to the deviation amount, the deviation of the fuel injection amount can be suppressed.

  The invention according to claim 11 is the fuel injection control device for an internal combustion engine according to any one of claims 1 to 10, wherein the drive current of the electromagnetic actuator is supplied from a battery (6), and the output of the battery Battery voltage detection means for detecting the voltage (VB), theoretical injection time calculation means for calculating the theoretical injection time (TINJTH) according to the operating state of the engine, and the theory according to the detected battery voltage (VB). And a corrected injection time calculating means for calculating a corrected injection time (TINJ) by correcting an injection time (TINJTH), wherein the valve opening command signal output means is configured to calculate the estimated valve opening timing (tAOPE) and the corrected injection. The valve opening command signal is output based on time (TINJ).

  According to this configuration, the corrected injection time is calculated by correcting the theoretical injection time according to the engine operating state according to the battery voltage, and the fuel injection is performed based on the calculated actual valve opening timing and the corrected injection time. A valve opening command signal is output. Therefore, the drive control of the fuel injection valve in which the delay from the output start timing of the valve opening command signal to the actual opening of the fuel injection valve is accurately reflected can be performed, and the control accuracy of the fuel injection amount can be improved.

1 is a diagram illustrating an internal combustion engine and a fuel injection device thereof according to an embodiment of the present invention. It is sectional drawing for demonstrating the structure of the principal part of the fuel injection valve shown in FIG. It is a circuit diagram for demonstrating the structure of the fuel injection valve drive part contained in the electronic control unit (ECU5) shown in FIG. It is a figure which shows the waveform of the drive voltage (VD) applied to the solenoid of a fuel injection valve, and the drive current (ID) supplied when opening a fuel injection valve. It is a figure for demonstrating the method of calculating the estimated valve opening time (tAOPE) which approximates the actual valve opening time of a fuel injection valve. It is a flowchart (1st Embodiment) for demonstrating the fuel-injection control process which performs fuel-injection control. It is a figure which shows the table referred by the process of FIG. It is a flowchart of the process which performs failure determination of a fuel injection valve. It is a flowchart of the modification of the process shown in FIG. It is a time chart for demonstrating the specific method of estimated valve opening time (tAOPE) (2nd Embodiment). It is a flowchart for demonstrating a fuel-injection control process (2nd Embodiment). It is a flowchart of the process which performs failure determination of a fuel injection valve (2nd Embodiment). It is a flowchart of the modification of the process shown in FIG. It is a flowchart of the modification of the process shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 shows an internal combustion engine (hereinafter referred to as “engine”) 1 and its fuel injection device according to an embodiment of the present invention. A four-cylinder engine 1 has four fuel injection valves 2 corresponding to each cylinder. I have. The fuel injection valve 2 injects fuel directly into the combustion chamber of the engine 1.

  A starter motor 4 is provided so as to be able to drive the crankshaft 3 of the engine 1, and the starter motor 4 is connected to a battery 6 via a switch circuit 7. Driving power is supplied from the battery 6 to the starter motor 4. The switch circuit 7 is connected to an electronic control unit (hereinafter referred to as “ECU”) 5, and on / off control is performed by the ECU 5.

  Each of the four fuel injection valves 2 is connected to the ECU 5, and its operation is controlled by the ECU 5. A battery 6 is connected to the ECU 5, and electric power for operating the ECU 5 and electric power for driving the fuel injection valve 2 are supplied from the battery 6.

  FIG. 2 is a cross-sectional view for explaining a configuration of a main part of the fuel injection valve 2. The fuel injection valve 2 includes a valve shaft 31, a valve body 32 fixed to the tip of the valve shaft 31, and a valve shaft 31. Flanges 33, 34 fixed to the core, a core 35 on which electromagnetic force acts, a first spring 36 provided between the core 35 and the flange 34, a valve seat 37, a sleeve 38, a solenoid 39, A second spring 40 that urges the flange 34 in the valve closing direction (downward in the figure) and an inner collar 41 having a hollow portion that functions as a fuel passage are provided.

  When the drive current is supplied to the solenoid 39, the core 35 moves upward in the figure, the valve shaft 31 and the valve body 32 similarly move upward, and the fuel injection valve 2 opens. The pressure of the fuel supplied from above in the figure and the urging force of the second spring 40 are applied to the valve body 32. Therefore, a biasing force in the valve opening direction that is larger than the biasing force in the valve closing direction acts on the valve body 32 by the drive current supplied to the solenoid 39, and the fuel injection valve 2 is opened.

  The ECU 5 includes an engine speed sensor 21 that detects the engine speed NE, an intake air flow sensor 22 that detects the intake air flow rate GAIR of the engine 1, an intake air temperature sensor 23 that detects the intake air temperature TA, and an engine cooling water temperature TW. Various sensors for detecting the engine operating state such as the cooling water temperature sensor 24 for detecting the engine are connected, and detection signals from these sensors are supplied to the ECU 5.

  The fuel injection valve 2 is connected to a delivery pipe 9 via a fuel passage 8, and fuel pressurized by a high-pressure pump 16 is supplied to the delivery pipe 9 via a passage 17. A fuel pressure adjusting mechanism 15 is provided in the middle of the passage 17, and the operation of the fuel pressure adjusting mechanism 15 is controlled by the ECU 5. The ECU 5 adjusts the fuel pressure PF in the delivery pipe 9 via the fuel pressure adjusting mechanism 15 in accordance with detection signals from the above-described sensors and other sensors (not shown).

  FIG. 3 is a circuit diagram for explaining the configuration of the fuel injection valve drive unit included in the ECU 5, and shows a circuit configuration for supplying a drive current to the solenoid 39 that drives the fuel injection valve 2 of one cylinder. . The circuits for driving the fuel injection valves of the other cylinders are similarly configured.

  3 includes field effect transistors (hereinafter referred to as “FETs”) Q1 and Q2 as switching elements for switching the power supply voltage supplied to one end of the solenoid 39, the other end of the solenoid 39 and the ground. FET Q3 as a switching element for switching between connection and non-connection, diodes D1 to D3, resistor R1, booster circuit 10, CPU 11, drive circuit 12, power supply circuit 13, capacitors C21 and C22, The control signal is supplied from the CPU 11 to the FETs Q1 to Q3 and the booster circuit 10.

  The booster circuit 10 is a circuit that boosts the output voltage VB (for example, 13V) of the battery 6 and outputs the first power supply voltage VS1 (for example, 40V), and includes a series circuit of a coil L11 and a diode D11, a capacitor C11, a resistor R11, R12, FETQ11, and drive circuit 14 are provided.

  The CPU 11 controls the duty ratio DTY of the on / off switching signal SSW of the FET Q11 output from the output terminal DCSW according to the feedback voltage VFB input to the input terminal VIN. Specifically, the duty ratio DTY is controlled so that the feedback voltage VFB matches the target voltage VFBX, and the target voltage VFBX is set to a value corresponding to a state in which the first power supply voltage VS1 is 40V, for example.

  The power supply circuit 13 stabilizes the battery output voltage VB, outputs a second power supply voltage VS2 (for example, 6V), and supplies it to the CPU 11 as a power supply voltage. Capacitors C21 and C22 are provided to prevent the second power supply voltage VS2 from temporarily decreasing, particularly when the engine that starts the starter motor 4 is started.

  The battery output voltage VB is supplied to one end of the solenoid 39 through the FET Q2 and the diode D1, and the first power supply voltage VS1 is supplied to one end of the solenoid 39 through the FET Q1. The other end of the solenoid 39 is connected to the ground via the FET Q3 and the resistor R1, and the diode D3 is disposed between the other end of the solenoid 39 and the output of the booster circuit 10.

  The second voltage control signal SDVS2 and the first voltage control signal SDVS1 output from the output terminals HSW1 and HSW2 of the CPU 11 are supplied to the gates of the FETs Q1 and Q2 via the drive circuit 12, and are output from the output terminal LSW of the CPU 11. The low-side control signal SDL is supplied to the gate of the FET Q3 through the drive circuit 12. The CPU 11 controls the drive current supplied to the solenoid 39 by performing on / off control of the FETs Q1 to Q3, and opens and closes the fuel injection valve 2.

  A connection point between the resistor R1 and the FET Q3 is connected to the current detection terminal VIDIN of the CPU 11. Since the input voltage of the current detection terminal VIDIN is proportional to the drive current ID flowing through the solenoid 39, the drive current ID can be detected. In the present embodiment, the battery voltage input terminal VBIN of the CPU 11 is connected to the output terminal of the battery 6 in order to correct the fuel injection time according to the battery voltage VB.

  4A and 4B are diagrams showing waveforms of the drive voltage VD applied to the solenoid 39 and the drive current ID supplied to the solenoid 39 when the fuel injection valve 2 is opened. (C) shows the valve opening command signal SCTL. The valve opening command signal SCTL is supplied in a period from time tIS to tIE. In a period TVS1 from time tIS to tSW, the FET Q1 is turned on and the first power supply voltage VS1 is supplied. During the period TVB from time tSW to tIE, the FET Q1 is turned off, and the FET Q2 is subjected to on / off duty control so that the holding current IHLD for holding the opened state of the fuel injection valve 2 matches the target current ICMD.

  The actual opening timing tAOP at which the fuel injection valve 2 is actually opened is in the vicinity of the time corresponding to the inflection point PX in the process in which the drive current change curve LID shown in FIG. It has been confirmed that there is. Therefore, the actual valve opening period TIACT of the fuel injection valve 2 is a period from time tAOP to tIE.

  FIG. 5 is a diagram for explaining a method of calculating the estimated valve opening timing tAOPE that approximates the actual valve opening timing tAOP, and is an enlarged view of the vicinity of the inflection point PX in FIG. In this embodiment, the estimated valve opening timing tAOPE is calculated according to the following procedure.

1) The first current value ID1 (first sample point PS1) at the first time point tS1 after the first time TS1 has elapsed from the supply start time (time tIS) of the drive current ID, and the second time TS2 has elapsed from the first time point tS1. A first approximate straight line LA1 passing through the first and second sample points PS1 and PS2 is obtained using the second current value ID2 (second sample point PS2) at the subsequent second time point tS2. Specifically, the coefficients a1 and b1 of the following formula (1) are calculated by the following formulas (2) and (3).
ID = a1 * t + b1 (1)
a1 = (ID2-ID1) / (tS2-tS1) (2)
b1 = (ID1 * tS2-ID2 * tS1) / (tS2-tS1) (3)

2) At the third current value ID3 (third sample point PS3) at the third time point tS3 after the lapse of the third time TS3 from the second time point tS2, and at the fourth time point tS4 after the lapse of the fourth time TS4 from the third time TS3. A second approximate straight line LA2 passing through the third and fourth sample points PS3 and PS4 is obtained using the fourth current value ID4 (fourth sample point PS4). Specifically, the coefficients a2 and b2 of the following formula (4) are calculated by the following formulas (5) and (6).
ID = a2 × t + b2 (4)
a2 = (ID4-ID3) / (tS4-tS3) (5)
b2 = (ID3 * tS4-ID4 * tS3) / (tS4-tS3) (6)

3) The time corresponding to the intersection of the approximate straight lines LA1 and LA2 is set as the estimated valve opening timing tAOPE. Specifically, the estimated valve opening timing tAOPE is calculated by the following equation (7).
tAOPE = (b1-b2) / (a2-a1) (7)

  In this way, the estimated valve opening timing tAOPE that approximates the actual valve opening timing tAOP is obtained by the approximate calculation using the four sample points PS1 to PS4, so that an expensive high-speed sampling circuit is not required and the cost is reduced. At the same time, the calculation load on the CPU 11 can be reduced.

  Note that since the rising portion of the drive current waveform shown in FIG. 4B is substantially the same regardless of the fuel injection amount, the first to fourth times TS1 to TS4 use experimentally obtained times in advance. . However, the second time point tS2 is set to a time point before the normal valve opening timing range, the third time point tS3 is set to a time point after the normal valve opening time range, and the fourth time point tS4 has the maximum drive current ID. Is set to a time point before the time point tSW.

FIG. 6 is a flowchart for explaining processing for calculating the estimated valve opening timing tAOPE by the above-described method and performing fuel injection control.
In step S11, a fuel injection execution timer is set based on the calculated fuel injection command time TINJCMD and fuel injection start command time TICMD (see step S29), and the fuel injection valve 2 ( Supply of the drive current ID to the solenoid 39) is started (step S12, time tIS in FIG. 4).

  In step S13, it is determined whether or not the first time TS1 has elapsed from time tIS, and the system waits until it elapses. When the answer to step S13 is affirmative (YES), that is, at the first time point tS1, the first current value ID1 is sampled (step S14). In step S15, it is determined whether or not the second time TS2 has elapsed from the first time point tS1, and the process waits until it elapses. When the answer to step S15 is affirmative (YES), that is, the second current value ID2 is sampled at the second time point tS2 (step S16).

  In step S18, it is determined whether or not the third time TS3 has elapsed since the second time point tS2, and the process waits until it elapses. When the answer to step S18 is affirmative (YES), that is, the third current value ID3 is sampled at the third time point tS3 (step S19). In step S20, it is determined whether or not the fourth time TS4 has elapsed from the third time point tS3, and the process waits until it elapses. When the answer to step S20 is affirmative (YES), that is, the fourth current value ID4 is sampled at the fourth time point tS4 (step S21).

  In parallel with the processing of steps S18 to S21, step S17 is executed, and the coefficients a1 and b1 are calculated by the above equations (2) and (3). Further, after step S21 is executed, the coefficients a2 and b2 are calculated by the above equations (5) and (6) in step S22.

  In step S23, the estimated valve opening timing tAOPE is calculated by the above equation (7). Considering the case where the estimated valve opening timing tAOPE cannot be calculated due to inappropriate detection data, in step S24, it is determined whether or not the calculation of the estimated valve opening timing tAOPE has been completed. If this answer is negative (NO), it is determined that there is an abnormality (step S25).

When the estimated valve opening timing tAOPE is calculated, the process proceeds to step S26, and the estimated valve opening timing tAOPE and the drive current supply start timing tIS are applied to the following equation (8) to calculate the injection delay time TIDLY.
TIDLY = tAOPE-tIS (8)

  In step S27, the theoretical injection time TINJTH is calculated according to the engine operating state (for example, the engine speed NE, the intake air flow rate GAIR, the intake air temperature TA, etc.). The theoretical injection time TINJTH is a fuel injection time corresponding to the fuel injection amount required in the detected engine operating state.

In step S28, the theoretical injection time TINJTH is applied to the following equation (9) to calculate the fuel injection time TINJ.
TINJ = KVB × TINJTH (9)

  KVB in equation (9) is a correction coefficient calculated by searching the KVB table shown in FIG. 7 according to the detected battery voltage VB. The KVB table is set so that the correction coefficient KVB decreases as the battery voltage VB decreases. Even when the valve opening command time is the same, the actual valve opening time of the fuel injection valve 2 becomes longer as the battery voltage VB decreases.

In step S29, the fuel injection command time TINJCMD is calculated by applying the fuel injection time TINJ and the injection delay time TIDLY to the following equation (10), and the theoretical injection start time TITH corresponding to the engine operating state is calculated as the injection delay time TIDLY. The fuel injection start command time TISCMD is calculated by correcting according to the above. The fuel injection start command time TISCMD corresponds to a standby time from the start time of the crank angle period in which fuel injection is to be executed to the valve opening command signal output start time (tIS).
TINJCMD = TINJ + TIDLY (10)

  Based on the fuel injection command time TINJCMD and the fuel injection start command time TICMD calculated in step S29, the next fuel injection is executed.

  FIG. 8 is a flowchart of a process for determining a failure of the fuel injection valve 2 based on a coefficient (hereinafter referred to as “first inclination”) a1 indicating the inclination of the first approximate straight line LA1. In this process, it is determined whether the fuel injection valve 2 is normal, in an intermediate failure state, or in a complete failure state. The intermediate failure state corresponds to a usable state although the actual fuel injection amount corresponding to the fuel injection command time TINJCMD deviates from a desired value, and the complete failure state corresponds to an unusable state.

  In step S30, the process waits until the calculation of the first inclination a1 is completed. When the calculation is completed, the process proceeds to step S31, whether the first inclination a1 is within the normal range, that is, the first inclination a1 is the lower normal threshold. It is determined whether or not a1THNL is equal to or greater than the upper normal threshold a1THNH.

  When the answer to step S31 is affirmative (YES), it is determined that the fuel injection valve 2 is normal (step S34). If the answer to step S31 is negative (NO), it is determined whether or not the first slope a1 is smaller than the lower NG determination threshold value a1NGL (<a1THNL) (step S32). If this answer is negative (NO), it is further determined whether or not the first slope a1 is larger than the upper NG determination threshold value a1NGH (> a1THNH) (step S33).

  When the answer to step S33 is negative (NO), that is, when a1NGL ≦ a1 <a1THNL or a1THNH <a1 ≦ a1NGH is satisfied, it is determined that the fuel injection valve 2 is in an intermediate failure state (step S35). When the answer to step S32 or S33 is affirmative (YES), it is determined that the fuel injection valve 2 is in a complete failure state (step S36).

When it is determined that the fuel injection valve 2 is in an intermediate failure state, the fuel injection command time TINJCMD is corrected as follows.
1) When a1NGL ≦ a1 <a1THNL, since the first slope a1 is smaller than the normal state, the fuel injection command time TINJCMD is corrected in the increasing direction.
2) When a1THNH <a1 ≦ a1NGH, since the first slope a1 is larger than the normal state, the fuel injection command time TINJCMD is corrected in the decreasing direction.

  As described above, in the present embodiment, the drive current values ID1 to ID1 at the predetermined timings tS1 to tS4 during the current increase period from the start of supply of the drive current ID to the solenoid 39 to the time tSW at which the drive current ID becomes maximum. The time point corresponding to the inflection point PX that appears when ID4 is sampled and the valve body 32 of the fuel injection valve 2 moves away from the valve seat 37 during the current increase period is based on the drive current values ID1 to ID4. It is calculated as an estimated valve opening timing tAOPE that approximates the actual valve opening timing tAOP of the valve 2. In the fuel injection valve 2 that directly injects fuel into the combustion chamber, the relative position between the core 35 and the solenoid 39 that displaces the valve body 32 in the valve opening direction by energization of the solenoid 39 changes, whereby the inductance of the solenoid 39 is changed. Decreases, and the current increase rate (slope) of the drive current ID increases relatively remarkably. Therefore, the estimated valve opening timing tAOPE can be calculated by acquiring the time corresponding to the inflection point by a relatively simple calculation.

  More specifically, the first and second current values ID1 and ID2 sampled at the first and second time points tS1 and tS2 set before the normal opening timing range of the fuel injection valve 2 are used for the first. The approximate straight line LA1 is obtained, and the second approximate straight line LA2 is obtained using the third and fourth current values ID3 and ID4 sampled at the third and fourth time points tS3 and tS4 set after the normal valve opening timing range. The obtained time point corresponding to the intersection of the first approximate line LA1 and the second approximate line LA2 is calculated as an estimated valve opening time tAOPE that approximates the actual valve opening time tAOP of the fuel injection valve 2. Therefore, an estimated valve opening timing tAOPE that approximates the actual valve opening timing can be obtained by an approximate calculation using four sampling data, so that an expensive high-speed sampling circuit is not required, and the calculation load of the CPU 11 is reduced. Can be reduced.

  Also, when the first slope a1 that is the slope of the first approximate line is in the intermediate failure range (a1NGL ≦ a1 <a1THNL or a1THNH <a1 ≦ a1NGH) set outside the normal range (a1THNL to a1THNH) When the fuel injection valve 2 is determined to be in the intermediate failure state and the first slope a1 is within the complete failure range (a1 <a1NGL or a1> a1NGH) set outside the intermediate failure range, the fuel injection valve When it is determined that 2 is in the complete failure state and the fuel injection valve 2 is determined to be in the intermediate failure state, the fuel injection start command time TISCMD is corrected according to the determined failure state. Therefore, the failure determination corresponding to the failure degree of the fuel injection valve 2 can be performed, and in the intermediate failure state, the fuel injection start command time TISCMD is corrected according to the failure state. It can suppress that it shifts from.

  Further, the fuel injection time TINJ is calculated by correcting the theoretical injection time TINJTH corresponding to the engine operating state in accordance with the detected battery voltage VB, and based on the calculated estimated valve opening timing tAOPE and fuel injection time TINJ. Thus, the fuel injection command time TINJCMD and the fuel injection start command time TICMD are calculated. Therefore, the drive control of the fuel injection valve 2 in which the injection delay time TIDLY until the fuel injection valve 2 actually opens from the output start timing of the valve opening command signal is accurately reflected is performed, and the control accuracy of the fuel injection amount is increased. Can be increased.

  In the present embodiment, the core 35, the first spring 36, the sleeve 38, and the solenoid 39 constitute an electromagnetic actuator, and the CPU 11 of the ECU 5 performs valve opening command signal output means, sampling means, inflection point acquisition means, estimated valve opening. Timing calculation means, first approximate straight line acquisition means, second approximate straight line acquisition means, first intermediate failure determination means, first complete failure determination means, battery voltage detection means, theoretical injection time calculation means, correction injection time means, and open Valve command signal output means is configured.

[Modification]
The failure determination process shown in FIG. 8 may be replaced with the process shown in FIG. The process shown in FIG. 9 performs failure determination using the first inclination a1 and a coefficient (hereinafter referred to as “second inclination”) a2 indicating the inclination of the second approximate line LA2.

  In steps S40 and S41, the calculation of the first inclination a1 and the second inclination a2 is awaited. When the calculation of the two inclinations is completed, the process proceeds to step S42, where the difference Da (= It is determined whether a2-a1) is equal to or greater than a predetermined threshold value DaFTH set to a value close to “0”. If this answer is negative (NO) and the difference Da is a value near “0” or a negative value, it is determined that the fuel injection valve 2 is in a complete failure state (step S46).

  If the answer to step S42 is affirmative (YES), it is determined whether or not the second slope a2 is not less than the lower normal threshold value a2THNL and not more than the upper normal threshold value a2THNH (step S43). When this answer is affirmative (YES), it is determined that the fuel injection valve 2 is normal (step S44), and when it is negative (NO), that is, when a2 <a2THNL or a2> a2THNH, the fuel It is determined that the injection valve 2 is in an intermediate failure state (step S45).

When it is determined that there is an intermediate failure state, the fuel injection command time TINJCMD is corrected as follows, as in the above-described embodiment.
1) When a2 <a2THNL, since the second slope a2 is smaller than the normal state, the fuel injection command time TINJCMD is corrected in the increasing direction.
2) When a1THNH <a2, since the second slope a2 is larger than the normal state, the fuel injection command time TINJCMD is corrected in the decreasing direction.

  In this modification, the failure of the fuel injection valve 2 is determined by comparing the slope a1 of the first approximate line LA1 and the slope a2 of the second approximate line LA2. If the fuel injection valve 2 is normal, the second inclination a2 is larger than the first inclination a1 by a predetermined threshold value DaFTH or more, so that the failure determination can be easily performed based on the difference Da.

  When the second inclination a2 is larger than the first inclination a1 by a predetermined threshold value DaFTH or more, no correction or the correction 1) or 2) is selected according to the second inclination a2. Since the deviation amount of the second inclination a2 greatly contributes to the fuel injection amount, deviation of the fuel injection amount can be suppressed by performing correction according to the deviation amount.

[Second Embodiment]
In the present embodiment, the time point corresponding to the inflection point PX is specified by a method different from that in the first embodiment, and is the same as the first embodiment except for the points described below.

  FIG. 10 is a time chart for explaining a method for specifying an inflection point corresponding time point (tAOPE) in the present embodiment, and schematically shows a change in the drive current ID. Focusing on the fact that the slope of the straight line approximating the change characteristic of the drive current ID increases after the inflection point PX, it is specified as follows. That is, by integrating the product of the drive current value ID (k) sampled every predetermined sampling period DTS and the predetermined sampling period DTS (the rectangular area value shown in FIG. 10), the integrated value SAID (k) is obtained. The time point one sampling period before the time point tPXP when the change amount DSAID (k) of the integrated value SAID (k) exceeds the determination threshold value DSAIDTH is specified as the inflection point corresponding time point. k is a discretization time discretized at a predetermined sampling period DTS.

  FIG. 11 is a flowchart for explaining the fuel injection control in this embodiment. Steps S24 and S25 in FIG. 6 are deleted, steps S14 to S23 are changed to steps S51 to S58, and step S26 is executed after step S58 is executed. It is intended to proceed to.

In step S51, the elapse of a predetermined sampling period DTS is waited, and when it elapses, the drive current value ID (k) is sampled (step S52). The discretization time k is initialized to “1” at the start of this process. In step S53, the integrated value SAID (k) is calculated by the following equation (11). SAID (0) is initialized to “0”.
SAID (k) = SAID (k−1) + ID (k) × DTS (11)

In step S54, the integrated value change amount DSAID (k) is calculated by the following equation (12), and in step S55, it is determined whether or not the integrated value change amount DSAID (k) is greater than or equal to the determination threshold value DSAIDTH.
DSAID (k) = SAID (k) −SAID (k−1) (12)

While the answer to step S55 is negative (NO), the discretization time k is increased by “1” (step S56), and the process returns to step S51. When the integrated value change amount DSAID (k) becomes equal to or greater than the determination threshold value DSAIDTH, the process proceeds to step S57, and a value obtained by subtracting “1” from the discretization time k at that time is stored as the discretized estimated valve opening timing kAOPE. In step S58, the calculated inflection point corresponding time is calculated as the estimated valve opening timing tAOPE by the following equation (13).
tAOPE = tS1 + DTS × kAOPE (13)

  FIG. 12 is a flowchart of the failure determination process for the fuel injection valve 2 in the present embodiment. In this process, step S30 in FIG. 8 is deleted, steps S60 to S62 are added, and when the answer to step S62 is affirmative (YES), the process proceeds to step S31. This process is executed in a period during which the first power supply voltage VS1 (see FIG. 4) is supplied, that is, a period in which the drive current ID is increasing.

In step S60, it is determined whether or not a period TVS1 (see FIG. 4) in which the first power supply voltage VS1 is supplied has elapsed. If the period TVS1 has elapsed, the process ends. When the answer to step S60 is negative (NO), a first inclination a1 corresponding to the inclination of the first approximate line LA1 in the first embodiment is calculated (steps S61 and S62). This calculation is performed by using appropriate two (for example, ID (1) and ID (kAOPE)) among the drive current values ID (k) sampled by the processing of FIG.
When the calculation of the first inclination a1 is completed, the process proceeds from step S62 to step S31.

  In the present embodiment, an integrated value SAID (k) of the sampled drive current value ID (k) is calculated, a change amount DSAID (k) of this integrated value is calculated, and the integrated value change amount DSAID (k) is calculated. Since the time point one sampling period before the time point determined to be equal to or greater than the determination threshold value DSAIDTH is determined as the time point corresponding to the inflection point PX, the time point corresponding to the inflection point can be specified by relatively simple calculation. it can.

[Modification 1]
The process shown in FIG. 11 may be modified as shown in FIG. The process shown in FIG. 13 is obtained by deleting step S53 of FIG. 11 and replacing steps S54 and S55 with steps S54a and S55a, respectively.

In step S54a, the drive current change amount DID (k) is calculated by the following equation (14).
DID (k) = ID (k) −ID (k−1) (14)
In step S55a, it is determined whether or not the drive current change amount DID (k) is greater than or equal to the determination threshold value DIDTH. While this answer is negative (NO), the process proceeds to step S56. Proceed to

  As apparent from FIG. 10, since the amount of change in the drive current value ID (k) changes before and after the inflection point PX, one sampling at the time when the amount of change in the drive current DID (k) becomes equal to or greater than the determination threshold DIDTH. The time point before the cycle can be specified as the time point corresponding to the inflection point PX. Therefore, it is possible to specify a time point corresponding to the inflection point PX by a relatively simple calculation.

[Modification 2]
In the second embodiment or the first modification, the process illustrated in FIG. 12 may be replaced with the process illustrated in FIG. The process shown in FIG. 14 is obtained by deleting steps S40 and S41 of the process shown in FIG. 9 and adding steps S60 to S64. Steps S60 to S62 are the same as the processing shown in FIG.

When the calculation of the first inclination a1 is completed, the process proceeds from step S62 to step S63, and the second inclination a2 that is the inclination of the second approximate line LA2 in the first embodiment is calculated. This calculation can be performed in the same manner as in the first embodiment. Further, the sampling of the sampling period DTS may be continued even after the inflection point corresponding time point has passed, and may be calculated using the drive current value ID (k) obtained by the sampling.
When the calculation of the second inclination a2 is completed, the process proceeds from step S64 to step S42.

  According to this modification, as in the modification of the first embodiment (FIG. 9), failure determination can be easily performed based on the difference Da between the first inclination a1 and the second inclination a2, and further, the intermediate In the failure state, the deviation of the fuel injection amount can be suppressed by performing the correction according to the deviation amount of the second inclination a2.

  The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, an example in which the present invention is applied to a fuel injection control device for a four-cylinder engine has been described. Applicable to the device. The present invention can also be applied to a fuel injection control device such as a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Fuel injection valve 6 Battery 11 CPU (Valve opening command signal output means, sampling means, inflection point acquisition means, estimated valve opening timing calculation means, first approximate straight line acquisition means, second approximate straight line acquisition means, battery Voltage detection means, theoretical injection time calculation means, correction injection time means, valve opening command signal output means)
35 core (electromagnetic actuator)
36 First spring (electromagnetic actuator)
38 Sleeve (Electromagnetic actuator)
39 Solenoid (electromagnetic actuator)

Claims (11)

A fuel injection valve for directly injecting fuel into a combustion chamber of an internal combustion engine, a valve body biased in a valve closing direction by the pressure of the fuel and a biasing force of a spring, and biasing the valve body in a valve opening direction A fuel injection control device for an internal combustion engine that controls the amount of fuel to be supplied into the combustion chamber by opening and closing a fuel injection valve provided with the electromagnetic actuator, through the electromagnetic actuator;
A valve opening command signal output means for outputting a valve opening command signal for driving the electromagnetic actuator;
Sampling means for sampling the value of the drive current at a predetermined timing during a current increase period from the start of supply of the drive current of the electromagnetic actuator to the time when the drive current becomes maximum,
An inflection point acquisition means for acquiring a time point corresponding to an inflection point in the change characteristic of the drive current, which appears when the valve element moves away from the valve seat during the current increase period, based on a sampling value by the sampling means. When,
A fuel injection control device for an internal combustion engine, comprising: estimated valve opening timing calculating means for calculating a time corresponding to the inflection point as an estimated valve opening timing approximating the actual valve opening timing of the fuel injection valve; . The sampling means includes a first time point after the first time has elapsed from the start of supplying the drive current of the electromagnetic actuator, a second time point after the second time has elapsed since the first time point, and a third time point after the third time has elapsed since the second time point. Sampling the value of the drive current at a third time point and a fourth time point after a fourth time from the third time point;
First approximate line acquisition means for obtaining a first approximate line that approximates the current change characteristic from the first time point to the second time point, using the first and second current values sampled at the first and second time points. When,
Second approximate line acquisition means for obtaining a second approximate line that approximates the current change characteristic from the third time point to the fourth time point by using the third and fourth current values sampled at the third and fourth time points. And further comprising
The estimated valve opening timing calculating means calculates a time point corresponding to an intersection of the first approximate line and the second approximate line as a time point corresponding to the inflection point,
The second time point is set to a time point before the normal valve opening timing range of the fuel injector, the third time point is set to a time point after the normal valve opening time range, and the fourth time point is the drive 2. The fuel injection control apparatus for an internal combustion engine according to claim 1, wherein the fuel injection control apparatus is set to a time point before a time point at which the current becomes maximum. First intermediate failure determination means for determining that the fuel injection valve is in an intermediate failure state when the slope of the first approximate straight line is in an intermediate failure range set outside a normal range;
First complete failure determination means for determining that the fuel injection valve is in a complete failure state when the slope of the first approximate straight line is in a complete failure range set outside the intermediate failure range;
The valve opening command signal output means corrects the valve opening command signal according to the determined failure state when it is determined that the fuel injection valve is in the intermediate failure state. 3. A fuel injection control device for an internal combustion engine according to 2.   The first failure determination means for determining a failure of the fuel injection valve by comparing the inclination of the first approximate line and the inclination of the second approximate line, according to claim 2. A fuel injection control device for an internal combustion engine.   The valve opening command signal output means corrects the valve opening command signal according to the slope of the second approximate line when the slope of the first approximate line is smaller than the slope of the second approximate line. The fuel injection control device for an internal combustion engine according to claim 4. The inflection point acquisition means includes
An integral value calculating means for calculating an integral value of the drive current using the sampling value;
An integral value change amount calculating means for calculating the change amount of the integral value;
The fuel injection control device for an internal combustion engine according to claim 1, wherein a time point corresponding to the inflection point is determined from a time point when the integrated value change amount is determined to be equal to or greater than a predetermined amount. The inflection point acquisition means includes
A sampling value change amount calculating means for calculating the change amount of the sampling value;
The fuel injection control device for an internal combustion engine according to claim 1, wherein a time point corresponding to the inflection point is determined from a time point when the sampling value change amount is determined to be equal to or greater than a predetermined amount. A first inclination calculating means for calculating a first inclination that is an inclination of a straight line approximating a current change characteristic in a period from a supply start time of driving current of the electromagnetic actuator to a time corresponding to the inflection point;
Second intermediate failure determination means for determining that the fuel injection valve is in an intermediate failure state when the first slope is in an intermediate failure range set outside a normal range;
Second complete failure determination means for determining that the fuel injection valve is in a complete failure state when the first slope is in a complete failure range set outside the intermediate failure range;
The valve opening command signal output means corrects the valve opening command signal of the fuel injection valve according to the determined failure state when it is determined that the fuel injection valve is in the intermediate failure state. A fuel injection control device for an internal combustion engine according to claim 6 or 7. A second inclination calculating means for calculating a second inclination that is an inclination of a straight line approximating a current change characteristic from a time corresponding to the inflection point to a time when the drive current becomes maximum;
9. The fuel injection of the internal combustion engine according to claim 8, further comprising second failure determination means for determining failure of the fuel injection valve by comparing the first inclination and the second inclination. Control device.   The valve opening command signal output means corrects the valve opening command signal of the fuel injection valve according to the second inclination when the first inclination is smaller than the second inclination. A fuel injection control device for an internal combustion engine according to claim 1. The drive current of the electromagnetic actuator is supplied from a battery,
Battery voltage detection means for detecting the output voltage of the battery;
Theoretical injection time calculating means for calculating the theoretical injection time according to the operating state of the engine;
A correction injection time calculating means for calculating a correction injection time by correcting the theoretical injection time according to the detected battery voltage;
The internal combustion engine according to any one of claims 1 to 10, wherein the valve opening command signal output means outputs the valve opening command signal based on the estimated valve opening timing and the corrected injection time. Fuel injection control device.

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