JP2019019740A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

To provide a fuel injection control device of an internal combustion engine which can exactly correct an injection amount.SOLUTION: A fuel injection system of an engine 10 comprises a fuel injection valve 30, a microcomputer 41 as a control part, and a drive IC 42. An ECU 40 comprises: a first information acquisition part for performing first electricity-carrying for carrying electricity to the fuel injection valve 30 in a form that a valve body 34 is driven, and acquiring first drive information as information related to a drive characteristic of the fuel injection valve 30 on the basis of a terminal voltage of the fuel injection valve 30 after a finish of the carrying of electricity of the first electricity-carrying; a second information acquisition part for performing second electricity-carrying for carrying electricity to the fuel injection valve 30 in a form that the valve body 34 is not driven, and acquires second drive information as information related to the drive characteristic on the basis of the terminal voltage after a finish of the carrying of electricity of the second electricity-carrying; and an injection amount calculation part for calculating an injection correction amount of the fuel injection valve 30 on the basis of the first drive information and the second drive information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  2. Description of the Related Art As a fuel injection valve that supplies fuel to each cylinder of an internal combustion engine mounted on a vehicle or the like, for example, an electromagnetic solenoid type is known. In this type of fuel injection valve, by controlling the energization timing and energization time to the coil built in the fuel injection valve body and driving the valve body (needle) in the valve opening direction, the fuel injection timing and fuel injection are controlled. The amount is controlled.

  In order to improve engine output, fuel consumption, exhaust emission, and the like, it is necessary to accurately control the fuel injection amount. Thus, various techniques related to correction of injection amount variation have been proposed (see, for example, Patent Document 1). Patent Document 1 discloses that a magnetic circuit is energized with a predetermined energization pulse within a range in which the valve body of the fuel injection valve is not driven, and a magnetic circuit variation value is calculated based on a negative terminal voltage of the fuel injection valve at that time. Has been.

JP, 2006-205276, A

  It is conceivable that the variation in the injection amount is influenced not only by the individual difference on the fuel injection valve side but also by the individual difference on the control unit side that controls the drive of the fuel injection valve. In order to control the fuel injection amount with high accuracy, it is necessary to detect the injection amount variation with high accuracy.

  The present invention has been made in view of the above problems, and a main object of the present invention is to provide a fuel injection control device for an internal combustion engine that can perform accurate injection amount correction.

  Hereinafter, means for solving the above-described problems and the effects thereof will be described. In the following, for ease of understanding, the reference numerals of the corresponding components in the embodiments of the invention are appropriately shown in parentheses, but are not limited to the specific configurations shown in parentheses.

  The present invention relates to a fuel injection control device for an internal combustion engine applied to a fuel injection system of an internal combustion engine (10) comprising a fuel injection valve (30) and a control unit (41, 42) for driving the fuel injection valve. . According to the first aspect of the present invention, the first energization for energizing the fuel injection valve is performed in such a manner that the valve element (34) of the fuel injection valve is driven, and the fuel after the energization of the first energization is completed. A first information acquisition unit that acquires first drive information as information relating to drive characteristics of the fuel injection valve based on a terminal voltage of the injection valve, and a second that energizes the fuel injection valve in a manner in which the valve body is not driven. Acquired by the first information acquisition unit, and a second information acquisition unit that acquires second drive information as information related to the drive characteristics based on the terminal voltage after the energization of the second energization is completed. And an injection amount calculation unit that calculates an injection correction amount of the fuel injection valve based on the first drive information and the second drive information acquired by the second information acquisition unit.

  In the above configuration, by using the terminal voltage of the fuel injection valve after the end of the first energization, as the information regarding the drive characteristics of the fuel injection valve, the injection amount variation caused by the lift behavior of the fuel injection valve, and the control unit It is possible to acquire information (first drive information) including the injection amount variation caused by the circuit elements. Further, by using the terminal voltage of the fuel injection valve after the end of the second energization, the information regarding the drive characteristics of the fuel injection valve does not include the injection amount variation due to the lift behavior of the fuel injection valve, and the control unit Information (second drive information) including variations in the injection amount caused by the circuit elements can be acquired. Therefore, according to the first drive information and the second drive information, it is possible to distinguish between the injection amount variation caused by the lift behavior of the fuel injection valve and the injection amount variation caused by the circuit element of the control unit. As a result, it is possible to accurately grasp the individual injection amount variations of the fuel injection valve and the control unit, and thus correct injection amount correction.

The schematic block diagram of an engine control system. It is a figure which shows the drive state of a fuel injection valve, (a) is a full lift state, (b) is a figure which shows a partial lift state. The figure which shows a partial lift area | region and a full lift area | region. The figure showing the behavior when fuel is injected from a fuel injection valve. The time chart showing transition of the minus terminal voltage after injection pulse off, and threshold arrival time. The figure which shows the difference in the waveform of the flyback voltage resulting from mechanical variation and electrical variation. The functional block diagram of fuel-injection control. The functional block diagram of fuel-injection control. The flowchart which shows the process sequence of a variation value calculation process. The flowchart which shows the process sequence of the calculation process of threshold value arrival time. The flowchart which shows the process sequence of a zero lift learning process. The time chart showing the specific aspect in the case of switching from normal mode to zero lift learning mode. The time chart showing the specific aspect in the case of switching from zero lift learning mode to normal mode.

  Hereinafter, embodiments will be described with reference to the drawings. This embodiment is embodied as a control system for controlling an in-cylinder multi-cylinder gasoline engine for a vehicle. First, a schematic configuration of the engine control system will be described with reference to FIG. In the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings, and the description of the same reference numerals is used.

  In the engine 11, an air cleaner 13 is provided in the uppermost stream portion of the intake pipe 12, and an air flow meter 14 that detects an intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  A surge tank 18 is provided downstream of the throttle valve 16, and an intake pipe pressure sensor 19 that detects the intake pipe pressure is provided in the surge tank 18. An intake manifold 20 that introduces air into each cylinder 21 of the engine 11 is connected to the surge tank 18. Each cylinder 21 of the engine 11 is provided with an electromagnetic fuel injection valve 30 that directly injects fuel into the cylinder. A spark plug 22 is attached to the cylinder head of the engine 11 for each cylinder 21, and the air-fuel mixture in the cylinder is ignited by spark discharge of the spark plug 22 of each cylinder 21.

  The exhaust pipe 23 of the engine 11 is provided with an exhaust sensor 24 that detects the air-fuel ratio or rich / lean of the air-fuel mixture using exhaust as a detection target. The exhaust sensor 24 is an air-fuel ratio sensor, an oxygen sensor, or the like. A catalyst 25 such as a three-way catalyst for purifying exhaust gas is provided on the downstream side of the exhaust sensor 24.

  A cooling water temperature sensor 26 that detects the cooling water temperature and a knock sensor 27 that detects knocking are attached to the cylinder block of the engine 11. A crank angle sensor 29 that outputs a pulse signal every time the crankshaft 28 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 28. Based on the crank angle signal of the crank angle sensor 29, the crank angle and the engine speed are detected. The outputs of these various sensors are input to the ECU 40.

  The ECU 40 is an electronic control unit mainly composed of a microcomputer, and performs various controls of the engine 11 based on detection signals from various sensors using a control program stored in a built-in ROM (storage medium). To do. The ECU 40 corresponds to a fuel injection control device. The ECU 40 calculates a required injection amount according to the engine operating state, controls the drive of the fuel injection valve 30 based on the required injection amount, and controls the ignition timing of the spark plug 22.

  Specifically, the fuel injection control includes an ECU 40 for controlling the engine, and a drive IC 42 for driving the fuel injection valve. The microcomputer 41 calculates a required injection amount based on the engine operating state and calculates an injection pulse width based on the calculated required injection amount. Further, the calculated ejection pulse width is output to the drive IC 42. The drive IC 42 drives the fuel injection valve 30 with an injection pulse generated based on the injection pulse width. Thereby, the fuel for the required injection amount is injected from the fuel injection valve 30.

  In the present embodiment, the engine 11 is a four-cylinder gasoline engine, and outputs an injection pulse in each of an intake stroke and a compression stroke within one combustion cycle as fuel injection by a fuel injection valve 30 provided in each cylinder. Inject. Note that the combustion order of the first cylinder # 1 to the fourth cylinder # 4 is # 1 → # 3 → # 4 → # 2. In the fuel injection, two cylinders with every other combustion order are grouped into drive groups 1 and 2, and each fuel injection valve 30 is driven by a drive system for each drive group. In the present embodiment, the first cylinder # 1 and the fourth cylinder # 4 belong to the drive group 1, and the second cylinder # 2 and the third cylinder # 3 belong to the drive group 2.

  The fuel injection valve 30 is provided with a voltage sensor 43 that detects a negative terminal voltage Vm and a current sensor 44 that detects an energization current flowing through an electromagnetic part (coil). The detection results of the voltage sensor 43 and the current sensor 44 are sequentially input to the ECU 40.

  In the fuel injection control of the present embodiment, the valve body of the fuel injection valve 30 is made to reach the full lift position, and a full lift injection for injecting a desired amount of fuel in the full lift state, and the valve body of the fuel injection valve 30 is brought to the full lift position. In the partial lift state before reaching, the movement of the valve body to the valve opening side is completed, and a desired minute amount of fuel is injected in this state. Partial lift injection is performed, for example, in fuel injection (in this embodiment, compression stroke injection) that is performed after main injection (in this embodiment, intake stroke injection).

  Full lift injection and partial lift injection will be described with reference to FIG. In FIG. 2, (a) shows the operation during full lift injection, and (b) shows the operation during partial lift injection.

  As shown in FIG. 2, the fuel injection valve 30 includes a coil 31 as an electromagnetic part that generates an electromagnetic force when energized, a fixed core 32 made of a magnetic material, and a fixed core 32 made of a magnetic material. The movable core 33 to be sucked, the needle-like valve body 34 that is driven integrally with the movable core 33, the first spring 35 that biases the valve body 34 toward the valve closing side, and the movable core 33 to be anti-closed And a second spring 36 biased to the side. As the coil 31 is energized, the valve element 34 moves away from the valve seat and moves toward the valve opening side, whereby the fuel injection valve 30 is opened and fuel injection is performed. The urging force of the second spring 36 is set smaller than the urging force of the first spring 35.

  2A and 2B, the injection pulse width is different. As shown in FIG. 2A, when the valve body lift amount is the full lift amount, the injection pulse width is relatively long. In this case, the valve body 34 reaches the full lift position where the movable core 33 abuts against the stopper 32a on the fixed core 32 side. On the other hand, as shown in FIG. 2B, when the valve body lift amount becomes the partial lift amount, the injection pulse width becomes relatively short. In this case, the valve body 34 is in a state before the movable core 33 abuts against the stopper 32a, and is in a partial lift state that does not reach the full lift position. When the energization of the coil 31 is stopped with the falling of the injection pulse, the movable core 33 and the valve body 34 return to the valve closing position, whereby the fuel injection valve 30 is closed, and fuel injection is stopped. Since the movable core 33 and the valve body 34 are configured separately, the valve body 34 is held in the closed position when the valve body 34 reaches the closed position, whereas the movable core 33 33 moves to the tip side more independently.

  FIG. 3 is a diagram illustrating a partial lift region in which partial lift injection is performed and a full lift region in which full lift injection is performed. As shown in FIG. 3, in both the partial lift region and the full lift region, the fuel injection amount tends to increase linearly as the injection pulse width (that is, energization time) is longer.

  Here, in the in-cylinder injection engine 11 that injects high-pressure fuel into the cylinder from the fuel injection valve 30, the linearity (linearity) of the change characteristic of the fuel injection amount with respect to the injection pulse width is likely to deteriorate in the partial lift region. The individual difference in the fuel injection amount corresponding to the injection pulse width tends to increase. On the other hand, if the variation in the injection amount is large, the amount of fuel injected from the fuel injection valve 30 cannot be precisely adjusted, and there is a concern that exhaust emissions, drivability, and the like may be deteriorated. In particular, in partial lift injection, the injection amount is very small, and the influence of variations in the injection amount tends to increase due to this small injection. For this reason, it is necessary to accurately detect individual injection amount variations for each injection system of each fuel injection valve 30 and ECU 40 and to perform injection amount control according to the injection amount variations.

  The injection amount variation of the fuel injection valve 30 includes a variation caused by individual differences in lift behavior of the fuel injection valve 30 (hereinafter, also referred to as “mechanical variation”), and a microcomputer 41 that controls driving of the fuel injection valve 30. And variations due to individual differences in circuit elements of the drive IC 42 (hereinafter also referred to as “electrical variations”). The mechanical variation is a variation in the injection amount on the side of the fuel injection valve 30 that is an actuator for performing fuel injection, and is caused by, for example, the assembled state of the fixed core 32 and the movable core 33, the ease of movement of the valve body 34, and the like. Occur. On the other hand, the electrical variation is a variation in the injection amount on the ECU 40 side that controls the driving of the fuel injection valve 30, and is caused by, for example, the magnetic efficiency in the circuit elements of the microcomputer 41 and the drive IC 42. In this case, the larger the magnetic loss in the circuit element of the ECU 40 (that is, the lower the magnetic efficiency), the shorter the required time from when the injection pulse to the fuel injection valve 30 is turned off until the valve is closed, and the valve closing timing Becomes faster.

  Therefore, in the present embodiment, among the injection amount variations of the fuel injection valve 30, an electrical variation value that is an injection correction amount for correcting the electrical variation and a machine that is the injection correction amount for correcting the mechanical variation. The fuel injection amount correction amount (injection correction amount) is calculated based on the calculated electrical variation value and mechanical variation value. The mechanical variation corresponds to the first correction amount, and the electrical variation value corresponds to the second correction amount. The injection amount variation calculation process of this embodiment will be described in detail below.

  In the fuel injection valve 30, the negative terminal voltage Vm changes due to the dielectric electromotive force as the injection pulse is turned off. This characteristic will be described with reference to FIG. FIG. 4 shows the behavior when the valve body 34 of the fuel injection valve 30 is driven to inject a predetermined amount of fuel from the fuel injection valve 30. 4, (a) is the positive terminal voltage Vp of the fuel injection valve 30, (b) is the negative terminal voltage Vm, (c) is the injector drive current, (d) is the injection rate of the fuel injection valve 30. The behavior is shown respectively. As can be seen from FIG. 4, when the coil 31 of the fuel injection valve 30 is energized and opened, and then energization is stopped after the passage of time corresponding to the injection pulse width, the battery voltage is reduced for a predetermined period immediately after the energization is turned off. A flyback voltage (back electromotive voltage) higher than VB is generated (see FIG. 4B).

  In the present specification, the magnitude of the negative terminal voltage Vm is expressed as an absolute value. For example, “Vm is larger than a predetermined value” means that Vm is a value larger on the negative side than the predetermined value.

  By using such a flyback voltage, it is possible to detect the actual valve closing timing in the fuel injection valve 30 (see FIG. 5). Specifically, the ECU 40 sets the minus terminal voltage Vm after the injection pulse is turned off during the fuel injection by partial lift injection as the cutoff frequency at the first frequency f1 lower than the noise component frequency. A first filter voltage Vsm1 filtered by the first low-pass filter (smoothing process) is calculated. The first low-pass filter is a low-pass filter whose pass band is a frequency band lower than the cutoff frequency (first frequency f1).

  In addition, the ECU 40 performs a filtering process (smoothing process) on the minus terminal voltage Vm after the injection pulse is turned off using a second low-pass filter having a second frequency f2 lower than the first frequency f1 as a cutoff frequency. The filter voltage Vsm2 is calculated. The filter process using the first low-pass filter and the filter process using the second low-pass filter are performed for each cylinder of the engine 11. By such processing, the ECU 40 calculates the first filter voltage Vsm1 obtained by removing the noise component from the negative terminal voltage Vm and the second filter voltage Vsm2 for detecting the valve closing position. The second low-pass filter is a low-pass filter whose pass band is a frequency band lower than the cutoff frequency (second frequency f2).

  Subsequently, a difference Vdiff (= Vsm1−Vsm2) between the first filter voltage Vsm1 and the second filter voltage Vsm2 is calculated. Further, the time required from the reference timing after the injection pulse is turned off (t3 in FIG. 5) to the timing at which the difference Vdiff exceeds the threshold Vt (t4 in FIG. 5) is calculated, and this is defined as the threshold arrival time Tdiff. In this embodiment, focusing on the fact that there is a correlation between the difference Vdiff and the valve closing timing, the timing at which the difference Vdiff exceeds the threshold value Vt is detected as the valve closing timing. Note that the threshold reaching time Tdiff is calculated for each cylinder of the engine 11 and the valve closing timing is calculated for each cylinder. The threshold arrival time Tdiff corresponds to “information relating to the drive characteristics of the fuel injection valve 30”.

  Regarding the reference timing In this embodiment, the timing at which the minus terminal voltage Vm falls below the determination value Voff after the injection pulse is turned off (in other words, the first timing at which the shift from the larger value to the smaller value than the determination value Voff) is used as the reference timing. . The reference timing may be set when the injection pulse is on (t1 in FIG. 5) or when the injection pulse is off (t2 in FIG. 5). The threshold value Vt may be a variable value according to the fuel pressure, the fuel temperature, or the like, or may be a fixed value set in advance.

  Furthermore, in the present embodiment, the mechanical variation value and the electrical variation value are calculated based on the behavior of the minus terminal voltage Vm after the injection pulse is turned off by using the flyback voltage generated when the power supply to the coil 31 is turned off. doing. Specifically, the ECU 40 performs lift learning for calculating a threshold arrival time Tdiff (corresponding to the first drive information) based on the minus terminal voltage Vm after power-off when the partial lift injection is performed. Further, the ECU 40 energizes the fuel injection valve 30 with a predetermined injection pulse in a range where the valve element 34 is not driven during a period in which fuel is not injected from the fuel injection valve 30 (in the present embodiment, during fuel cut). Zero lift learning for calculating a threshold arrival time Tdiff (corresponding to the second drive information) based on the minus terminal voltage Vm after turning off the power is performed. A threshold arrival time Tdiff calculated by lift learning (hereinafter also referred to as “threshold arrival time Tdiff — 1”), a threshold arrival time Tdiff calculated by zero lift learning (hereinafter also referred to as “threshold arrival time Tdiff — 2”), and Based on the above, a mechanical variation value and an electrical variation value are calculated. The electrical variation value corresponds to the “first correction amount”, and the mechanical variation value corresponds to the “second correction amount”.

  FIG. 6 shows the difference in flyback voltage waveform caused by mechanical and electrical variations. In FIG. 6, (a) shows the time of lift learning, and (b) shows the time of zero lift learning. In FIG. 6, it is assumed that the magnetic efficiency of the circuit element of the ECU 40 is worse than the nominal, and the flyback voltage converges quickly.

  In zero lift learning, the coil 31 is energized, but the valve element 34 is not driven. In this case, the minus terminal voltage Vm after the injection pulse is off is not affected by the mechanical variation, but deviates from the nominal value due to the electrical variation. That is, as shown in FIG. 6B, the deviation amount (S1 in FIG. 6) from the nominal value of the minus terminal voltage Vm when energization is performed with an injection pulse in a range where the valve element 34 is not driven is electrical. It can be considered that it originates in dispersion | variation.

  On the other hand, in the lift learning, the valve element 34 is driven by energizing the coil 31 to inject fuel from the fuel injection valve 30. In this case, the minus terminal voltage Vm after the injection pulse is off is deviated from the nominal value under the influence of both mechanical and electrical variations. That is, as shown in FIG. 6A, the amount of deviation from the nominal value of the minus terminal voltage Vm when energization is performed with an injection pulse in the range where the valve element 34 is driven is the amount of deviation caused by electrical variation. (S1 in FIG. 6) and the amount of deviation due to mechanical variation (S2 in FIG. 6) can be regarded as the sum. Therefore, if the deviation amount S1 in the zero lift learning is excluded, the deviation amount due to the mechanical variation can be acquired.

  The mechanical variation is a value determined for each fuel injection valve 30, and the electrical variation is a value determined for each drive system of the ECU 40. According to the lift learning and the zero lift learning, the mechanical variation for each fuel injection valve 30 can be acquired, and the electrical variation for each drive system of the ECU 40 can be acquired.

  7 and 8 are functional block diagrams of the fuel injection control of the present embodiment. As shown in FIG. 7, the microcomputer 41 of the ECU 40 includes an injection pulse calculation unit 51 and a storage unit 52. The injection pulse calculation unit 51 calculates a basic injection amount based on the engine operating state (for example, engine speed, engine load, etc.). Further, the required injection amount is calculated by reading the correction parameter stored in the storage unit 52 and correcting the basic injection amount based on the read correction parameter. In the present embodiment, the correction parameter includes a mechanical variation value and an electrical variation value. The injection pulse calculation unit 51 generates a signal representing the injection pulse width Ti corresponding to the required injection amount, and outputs the signal to the drive IC 42.

  The drive IC 42 includes a drive control unit 53 and a calculation unit 54. The drive control unit 53 inputs a signal representing the injection pulse width Ti from the injection pulse calculation unit 51, and opens the fuel injection valve 30 with the injection pulse generated based on the injection pulse width Ti. The calculation unit 54 includes a zero lift learning unit 55 and a lift learning unit 56 as means for calculating the correction amount (deviation amount) of the fuel injection amount based on the behavior of the minus terminal voltage Vm after the injection pulse is turned off. Yes.

As shown in FIG. 8, the zero lift learning unit 55 includes a Tdiff calculation unit 55A, a reference value storage unit 55B, a correction amount calculation unit 55C, and a correction amount storage unit 55D. When a predetermined zero lift learning execution condition is satisfied, the Tdiff calculation unit 55A energizes the fuel injection valve 30 with an injection pulse in a range where the valve body 34 of the fuel injection valve 30 is not driven, and calculates a threshold arrival time Tdiff_2. The correction amount calculation unit 55C receives the threshold arrival time Tdiff_2 from the Tdiff calculation unit 55A and acquires a reference value (nominal value, constant) from the reference value storage unit 55B. Then, an electrical variation value Q1 is calculated as a deviation amount of the threshold arrival time Tdiff_2 with respect to the reference value. The electrical variation value Q1 is expressed by, for example, the following formula (1).
Q1 = (Threshold arrival time Tdiff_2) / reference value (1)
The calculated electrical variation value Q1 is stored in the correction amount storage unit 55D.

  As shown in FIG. 8, the lift learning unit 56 includes a Tdiff calculation unit 56A, a first calculation unit 56B, an estimated injection amount calculation unit 56C, a reference injection amount storage unit 56D, and a second calculation unit 56E. ing. When a predetermined lift learning execution condition is satisfied, the Tdiff calculation unit 56A energizes the fuel injection valve 30 with an injection pulse that can displace the valve body 34 to a predetermined partial lift position, and calculates a threshold arrival time Tdiff_1. The first calculation unit 56B receives the threshold arrival time Tdiff_1 from the Tdiff calculation unit 56A and acquires the electrical variation value Q1 from the correction amount storage unit 55D. Then, the threshold arrival time Tdiff_1 is multiplied by the electrical variation value Q1 to calculate a corrected threshold arrival time Tdiff * Q1. The corrected threshold arrival time Tdiff * Q1 is information regarding the valve closing timing in which the electrical variation is removed from the threshold arrival time Tdiff_1 and the mechanical variation is included.

The estimated injection amount calculation unit 56C calculates the estimated injection amount R from the corrected threshold arrival time Tdiff * Q1. Here, the estimated injection amount R is calculated by multiplying the corrected threshold arrival time Tdiff * Q1 by the correction coefficient K. The second calculation unit 56E receives the estimated injection amount R from the estimated injection amount calculation unit 56C and acquires the reference injection amount (nominal value, constant) from the reference injection amount storage unit 56D. Then, a mechanical variation value Q2 is calculated as a deviation amount of the estimated injection amount R with respect to the reference injection amount. The mechanical variation value Q2 is expressed by, for example, the following formula (2).
Q2 = estimated injection amount / reference injection amount (2)

  The microcomputer 41 of the ECU 40 stores the electrical variation value Q1 and the mechanical variation value Q2 input from the drive IC 42 in the storage unit 52 as correction amounts for the injection amount variation. The microcomputer 41 corrects the basic injection amount using the electrical variation value Q1 and the mechanical variation value Q2 stored in the storage unit 52, and opens the fuel injection valve 30 based on the corrected injection pulse. . The lift learning unit 56 realizes the function of the “first information acquisition unit”, and the zero lift learning unit 55 realizes the function of the “second information acquisition unit”. Further, the lift learning unit 56 and the zero lift learning unit 55 realize the function of the “correction amount calculation unit”.

  When calculating the electrical variation value Q1, the threshold arrival time Tdiff_2 is acquired by performing energization for zero lift learning once, and the electrical variation value Q1 is calculated using the acquired threshold arrival time Tdiff_2. May be. Alternatively, a plurality of threshold arrival times Tdiff_2 may be obtained by performing energization for zero lift learning a plurality of times, and the electrical variation value Q1 may be calculated from the average value. Similarly, for the mechanical variation value Q2, the mechanical variation value Q2 may be calculated from one threshold arrival time Tdiff_1, and the mechanical variation is calculated from the average value of the threshold arrival times Tdiff_1 obtained by multiple fuel injections. The value Q2 may be calculated.

  Next, the processing procedure of the variation value calculation process in the present embodiment will be described with reference to the flowchart of FIG. This process is executed by the drive IC 42 every predetermined cycle (for example, every combustion cycle).

  In FIG. 9, in step S101, it is determined whether or not zero lift learning has been completed. If the zero lift learning has not been completed yet, the process proceeds to step S102, and it is determined whether or not the zero lift learning execution condition is satisfied.

The following conditions B1 to B7 are set as the zero lift learning execution conditions, and when all of these conditions B1 to B7 are satisfied, an affirmative determination is made in step S102.
B1: Zero lift learning has not been completed yet in this driving cycle.
B2: Fuel is being cut during deceleration for all cylinders.
B3: The engine rotation speed is equal to or higher than a predetermined return rotation speed at which the fuel cut state returns to the combustion state.
B4: The pressure (fuel pressure) of the fuel injected from the fuel injection valve 30 is equal to or higher than a predetermined fuel pressure that can avoid unintended fuel injection by energization for zero lift learning.
B5: The battery voltage is equal to or higher than a predetermined voltage that can guarantee the operation of the fuel injection valve 30.
B6: The in-cylinder pressure is equal to or higher than a predetermined pressure at which unintended fuel injection due to energization for zero lift learning can be avoided.
B7: Fail-safe is not being executed.

  If the zero lift learning execution condition is not satisfied, this routine is terminated as it is. On the other hand, when the zero lift learning execution condition is satisfied, the process proceeds to step S103, and zero lift learning is executed according to the flowchart shown in FIG. Thereafter, in step S104, the electrical variation value Q1 calculated by the zero lift learning is output to the microcomputer 41 and stored or updated in the storage unit 52 of the microcomputer 41.

  When the zero lift learning is completed, an affirmative determination is made in step S101 and the process proceeds to step S105. In step S105, it is determined whether lift learning execution conditions are satisfied. The lift learning execution conditions include at least the conditions that zero lift learning has been completed, fuel cut is not in progress, and catalyst early warm-up is in progress, and all these conditions are satisfied A positive determination is made.

  If the lift learning execution condition is satisfied, the process proceeds to step S106 and lift learning is executed. In step S107, the mechanical variation value Q2 calculated by the lift learning is output to the microcomputer 41 and stored or updated in the storage unit 52 of the microcomputer 41.

  Next, processing for calculating the threshold arrival time Tdiff in lift learning and zero lift learning will be described with reference to the flowchart of FIG. This process is executed by the drive IC 42 every predetermined period (for example, every several msec).

In FIG. 10, in step S201, the minus terminal voltage Vm of the fuel injection valve 30 is acquired. In subsequent step S202, the negative terminal voltage Vm is filtered by the first low-pass filter to calculate the first filter voltage Vsm1. The first low-pass filter uses the previous value Vsm1 (k−1) of the first filter voltage and the current value Vm (k) of the minus terminal voltage to obtain a current value Vsm1 (k) of the first filter voltage. It is implemented by the following equation (3).
Vsm1 (k) =
{(N1-1) / n1} * Vsm1 (k-1) + (1 / n1) * Vm (k) (3)

The time constant n1 of the first low-pass filter is the following (4) using the sampling frequency fs (= 1 / Ts) of the negative terminal voltage Vm and the cut-off frequency (first frequency f1) of the first low-pass filter. It is set so as to satisfy the expression relationship.
1 / fs: 1 / f1 = 1: (n1-1) (4)

In subsequent step S203, a second filter voltage Vsm2 obtained by filtering the minus terminal voltage Vm with a second low-pass filter having a second frequency f2 lower than the first frequency f1 as a cutoff frequency is calculated. The second low-pass filter uses the previous value Vsm2 (k−1) of the second filter voltage and the current value Vm (k) of the negative terminal voltage to obtain a current value Vsm2 (k) of the second filter voltage. It is implemented by the following equation (5).
Vsm2 (k) =
{(N2-1) / n2} * Vsm2 (k-1) + (1 / n2) * Vm (k) (5)
The time constant n2 of the second low-pass filter is the following (6) using the sampling frequency fs (= 1 / Ts) of the negative terminal voltage Vm and the cutoff frequency (second frequency f2) of the second low-pass filter. It is set so as to satisfy the expression relationship.
1 / fs: 1 / f2 = 1: (n2-1) (6)

  In subsequent step S204, a difference Vdiff (= Vsm1−Vsm2) between the first filter voltage Vsm1 and the second filter voltage Vsm2 is calculated. Note that it is possible to extract only a minus component by performing a guard process so that the difference Vdiff does not become 0 or more.

  In subsequent step S205, the threshold value Vt is acquired, and the previous value Tdiff (k-1) of the threshold arrival time is acquired. In step S206, it is determined whether the injection pulse is off. If an affirmative determination is made in step S206, the process proceeds to step S207, and whether or not it is a timing at which the minus terminal voltage Vm of the fuel injection valve 30 falls below the determination value Voff (a timing at which the negative value becomes larger than the determination value Voff). Determine. If an affirmative determination is made in step S207, the process proceeds to step S209, and the current value Tdiff (k) of the voltage inflection time is reset to “0”.

  On the other hand, if a negative determination is made in step S207, the process proceeds to step S208, and whether or not the difference Vdiff between the first filter voltage Vsm1 and the second filter voltage Vsm2 exceeds the threshold value Vt (smaller to larger than the threshold value Vt). Or not). If a negative determination is made in step S208, the process proceeds to step S210, where a predetermined value Ts (the calculation cycle of this routine) is added to the previous value Tdiff (k−1) of the threshold arrival time, and the current value Tdiff of the threshold arrival time. By obtaining (k), the threshold arrival time Tdiff is counted up.

  On the other hand, if it is determined in step S208 that the difference Vdiff has exceeded the threshold value Vt, the process proceeds to step S211, and the current value Tdiff (k) of the threshold arrival time is held at the previous value Tdiff (k−1). Thus, the time from the timing (reference timing) when the negative terminal voltage Vm of the fuel injection valve 30 falls below the determination value Voff after the injection pulse is turned off to the timing when the difference Vdiff exceeds the threshold value Vt is calculated as the threshold arrival time Tdiff.

  If it is determined in step S206 that the injection pulse is not off (that is, the injection pulse is on), the current value Tdiff (k) is held at the previous value Tdiff (k−1), and the threshold is reached. The calculated value of time Tdiff is held until the next reference timing.

  Next, the processing procedure of zero lift learning will be described using the flowchart of FIG. This process is executed by the drive IC 42 at a predetermined calculation cycle (for example, every injection update timing).

  In FIG. 11, in step S301, it is determined whether or not the zero lift learning execution condition (B1 to B7) is satisfied. If the zero lift learning execution condition is satisfied, the process proceeds to step S302, the execution condition satisfaction flag is set, and the injection mode for zero lift learning is set. Specifically, the fuel injection in each cylinder is set to one intake stroke. In addition, the injection timing is set to a predetermined time for zero lift learning, and the injection time is set to a predetermined time Doff for zero lift learning. The predetermined time Doff is set to a value corresponding to the energization pulse width in which the valve element 34 of the fuel injection valve 30 is not driven (see FIG. 6B).

  In step S303, the zero lift learning counter is counted up. In a succeeding step S304, it is determined whether or not the zero lift learning counter is larger than the first determination value TH1. If the zero lift learning counter is equal to or less than the first determination value TH1, this routine is once ended. On the other hand, if the zero lift learning counter is larger than the first determination value TH1, the process proceeds to step S305, the injector drive current is set to a predetermined current value Aoff for zero lift learning, and the fuel injection valve 30 is driven during fuel cut. Allow. Here, the predetermined current value Aoff is a current value at which the valve body 34 of the fuel injection valve 30 is not driven. The predetermined current value Aoff may be variably set according to the engine operating state (for example, fuel pressure), or may be a fixed value.

  In a succeeding step S306, it is determined whether or not the zero lift learning counter is larger than the second determination value TH2. The process proceeds to step S307 on condition that the zero lift learning counter is larger than the determination value TH2. In step S307, detection of a value for zero lift learning (in this embodiment, threshold arrival time Tdiff_2) is permitted. In step S308, the electrical variation value Q1 is calculated based on the threshold arrival time Tdiff_2.

  If the zero lift learning execution condition is not satisfied, the process proceeds to step S309, and the injection mode is set to the normal mode. In step S310, the zero lift learning counter is reset and the detection of the zero lift learning value is prohibited. Thereafter, this routine is terminated.

  According to the flowchart of FIG. 11, the ECU 40 changes the injection mode from the normal mode, which is the normal fuel injection mode, to acquire the threshold arrival time Tdiff by energizing the valve body 34 of the fuel injection valve 30 without being driven. In the case of switching to the zero lift learning mode, even if the zero lift learning execution condition is satisfied, the zero lift learning mode is not switched immediately, but the zero lift learning mode is switched after a predetermined delay time has elapsed. On the other hand, when switching from the zero lift learning mode to the normal mode, the mode is immediately switched to the normal mode when the zero lift learning execution condition is not satisfied. This control will be described with reference to the time charts of FIGS. Note that black triangles in FIGS. 12 and 13 indicate the injection update timing.

  First, switching from the normal mode to the zero lift learning mode will be described with reference to FIG. In FIG. 12, a case where the fuel cut is started at time t11 and the zero lift learning execution condition is satisfied at time t12 of the subsequent injection update timing is considered. In this case, at time t12, the injection timing is set to a predetermined time for learning zero lift, and the injection time is set to a predetermined time for learning zero lift. Also, the zero lift learning counter is incremented by one.

  The zero lift learning counter is counted up at each injection update timing, and when the zero lift learning counter exceeds the first determination value TH1 ("2" in FIG. 12), the fuel injection valve 30 during fuel cut is driven at time t14. And the injector drive current is set to a predetermined current value Aoff for zero lift learning. Thus, each fuel injection valve 30 is energized with a predetermined current value Aoff in a range where the valve element 34 is not driven at a predetermined timing for zero lift learning. In FIG. 12, after the zero lift learning execution condition is established, first, the fuel injection valve 30 of the second cylinder # 2 is energized for zero lift learning in the intake stroke of the second cylinder # 2, and then The fuel injection valve 30 of the first cylinder # 1 is energized for zero lift learning during the intake stroke of the first cylinder # 1. When the zero lift learning counter exceeds the second determination value TH2 (“4” in FIG. 12), acquisition of the zero lift learning value is permitted at time t16 of the subsequent injection update timing, and the electrical variation value Q1 is Calculated.

  Next, the case of switching from the zero lift learning mode to the normal mode will be described with reference to FIG. In FIG. 13, when the fuel cut is completed at time t21, the injection timing and the injection time are set to the values of the normal mode because it is determined that the zero lift learning execution condition is not satisfied at the time t22 of the injection update timing immediately after that. Can be switched. Further, the zero lift learning counter is reset to zero, and the injector drive current is switched to the normal mode value.

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

  The threshold arrival time Tdiff_1 calculated based on the minus terminal voltage Vm after the energization of the partial lift injection is turned off is an injection amount variation (mechanical variation) caused by the lift behavior of the fuel injection valve 30 and an injection caused by a circuit element of the ECU 40. Amount variation (electrical variation). On the other hand, the threshold arrival time Tdiff_2 calculated based on the minus terminal voltage Vm after turning off the energization pulse in a range where the valve element 34 is not driven is information obtained in a state where the valve element 34 is not driven, and therefore mechanical variation. And electrical variation. Therefore, according to the threshold arrival time Tdiff_1 and the threshold arrival time Tdiff_2, it is possible to separate the injection amount deviation amount due to mechanical variation and the injection amount deviation amount due to electrical variation. Therefore, it is possible to accurately grasp the variations in the injection amounts of the fuel injection valve 30 and the ECU 40, and to correct the injection amount accurately.

  Since the condition for executing the zero lift learning is that the fuel is being cut when the vehicle is decelerated, it is not necessary to perform the fuel cut for the zero lift learning. Moreover, since the vehicle is being decelerated during the fuel cut execution period, even if fuel is injected from the fuel injection valve 30 by energization for zero lift learning, the influence on drivability should be reduced. Can do.

  Since the zero lift learning is executed on condition that the fuel pressure injected from the fuel injection valve 30 is equal to or higher than a predetermined fuel pressure that can avoid unintended fuel injection due to energization for zero lift learning, the back pressure is sufficiently high. Learning can be performed in a situation where the valve body 34 is difficult to open. Thereby, it can be prevented that fuel is actually injected by energization of the fuel injection valve 30.

(Other embodiments)
The present invention is not limited to the contents of the above embodiment, and may be implemented as follows, for example.

  In the above embodiment, the threshold arrival time Tdiff_1 calculated by lift learning is corrected with the electrical variation value Q1, and the estimated injection amount R is calculated from the corrected threshold arrival time Tdiff * Q1 to calculate the mechanical variation value Q2. However, after calculating the estimated injection amount from the threshold arrival time Tdiff_1, the mechanical variation value Q2 may be calculated by correcting the estimated injection amount with the electrical variation value Q1.

  In the above embodiment, the zero lift learning is performed during fuel cut at the time of vehicle deceleration, but the vehicle operation state may be an operation state in which the fuel injection valve 30 is not driven. For example, after the ignition is turned on, the zero lift learning may be performed before the engine is started. Further, zero lift learning may be performed during fuel cut while the vehicle is stopped.

  In the above embodiment, lift learning is performed in partial lift injection, but may be configured in full lift injection.

  -Each said component is conceptual and is not limited to the said embodiment. For example, the functions of one component may be realized by being distributed to a plurality of components, or the functions of a plurality of components may be realized by one component.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 30 ... Fuel injection valve, 34 ... Valve body, 40 ... ECU (1st information acquisition part, 2nd information acquisition part, injection amount correction | amendment part), 41 ... Microcomputer (control part), 42 ... Drive IC (control unit).

Claims (5)

Applied to a fuel injection system of an internal combustion engine (10) comprising a fuel injection valve (30) and a control unit (41, 42) for controlling the drive of the fuel injection valve;
Based on the terminal voltage of the fuel injection valve after the end of energization of the first energization, while performing the first energization to energize the fuel injection valve in a manner in which the valve body (34) of the fuel injection valve is driven. A first information acquisition unit for acquiring first drive information as information relating to drive characteristics of the fuel injection valve;
Second energization for energizing the fuel injection valve in a mode in which the valve body is not driven is performed, and second drive information is provided as information on the drive characteristics based on the terminal voltage after energization of the second energization is completed. A second information acquisition unit to acquire;
A correction amount calculation unit that calculates an injection correction amount of the fuel injection valve based on the first drive information acquired by the first information acquisition unit and the second drive information acquired by the second information acquisition unit;
A fuel injection control device for an internal combustion engine, comprising: The correction amount calculation unit corrects the first correction amount for correcting the injection amount variation caused by the control unit and the injection amount variation caused by the lift behavior of the fuel injection valve as the injection correction amount. And a second correction amount of
2. The internal combustion engine according to claim 1, wherein the first correction amount is calculated using the second drive information, and the second correction amount is calculated using the first drive information and the first correction amount. Fuel injection control device.   3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the first drive information and the second drive information are information relating to a shift amount of a valve closing timing of the fuel injection valve.   The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3, wherein the second information acquisition unit performs the second energization during fuel cut during vehicle deceleration. The control unit is configured to perform full lift injection that opens the fuel injection valve with an injection pulse in which the lift amount of the valve body reaches a full lift position, and an injection pulse in which the lift amount of the valve body does not reach the full lift position. Performing partial lift injection that opens the fuel injection valve,
The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4, wherein the first information acquisition unit performs the first energization during an execution period of the partial lift injection.

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