JP7035466B2 - Fuel injection control device - Google Patents

Description

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

In a fuel injection valve that injects and supplies fuel to each cylinder of an internal combustion engine mounted on a vehicle, etc., the valve body (needle) is driven in the valve opening direction by controlling the energization timing and energization time of the fuel injection valve body. The fuel injection timing and the fuel injection amount are controlled by (see, for example, Patent Document 1). In this type of fuel injection control, the operating characteristics of the fuel injection valve are detected, and the above control is performed using the correction value calculated based on the detection result, so that the required injection amount and the actual injection amount can be determined. The effect of reducing the error can be expected.

Japanese Unexamined Patent Publication No. 2016-75171

Here, in the above-mentioned fuel injection, the influence of the operation related to the fuel injection may remain after the energization is terminated and the valve body is returned to the closed state. As an effect of this, in the configuration in which the solenoid type fuel injection valve is adopted, it is considered that it takes a certain period of time for the magnetic flux to remain and the magnetic flux (residual magnetic flux) to disappear even after the valve body is restored.

When the correction value calculated under such an influence is used, the above effect of reducing the error between the required injection amount and the actual injection amount cannot be exerted well, and the fuel injection amount can be optimized. There is concern that it will hinder the plan. As described above, there is still room for improvement in fuel injection control in order to optimize the fuel injection amount while improving the combustion state.

The present invention has been made in view of the above problems, and a main object thereof is to provide a fuel injection control device for an internal combustion engine capable of performing appropriate fuel injection control.

Hereinafter, means for solving the above problems will be described.

The fuel injection control device of the present invention is applied to a fuel injection system including a fuel injection valve for injecting fuel in an internal combustion engine, and the change in energization current with respect to a drive command is detected as an energization characteristic in the fuel injection valve, and the detected energization is performed. It is a fuel injection control device that calculates a correction value for energization control of the fuel injection valve based on the characteristics, and is the injection interval from the previous fuel injection to the next fuel injection or its correlation when the fuel is injected by the fuel injection valve. Based on the information to be injected, the determination unit for determining whether or not the injection interval is larger than the predetermined time, and the next fuel injection when the determination unit determines that the injection interval is larger than the predetermined time. It is provided with a correction value calculation unit that permits the calculation of the correction value in the above and prohibits the calculation of the correction value in the next fuel injection when it is determined that the injection interval is smaller than a predetermined time. ing.

When it is determined that the injection interval from the previous fuel injection to the next fuel injection is larger than the predetermined time, the calculation of the correction value in the next fuel injection is permitted, and it is determined that the injection interval is smaller than the predetermined time. In this case, if the calculation of the correction value in the next fuel injection is prohibited, it is possible to prevent the accuracy of the correction value from being lowered due to the influence of one injection affecting the other injection. As a result, the deviation between the required injection amount and the actual injection amount can be alleviated, which can contribute to the optimization of the fuel injection amount.

The figure which shows the schematic structure of the engine control system in 1st Embodiment. The figure which shows the structure and the state of a fuel injection valve. A timing chart for explaining the driving operation of the fuel injection valve. A timing chart showing the difference in energization characteristics of the fuel injection valve. A timing chart illustrating the effect of residual magnetic flux. A flowchart showing the learning process. The flowchart which shows the process for single-shot injection. The flowchart which shows the process for multi-stage injection. A timing chart showing the relationship between the stroke and the injection. The schematic diagram which shows the relationship between the reference time and the possibility of learning. The schematic diagram which exemplifies the possibility of learning for each injection. The block diagram which shows the electric structure in 2nd Embodiment. The schematic diagram which shows the calculation example of an interval time. The flowchart which shows the learning process in 3rd Embodiment. The flowchart which shows the learning process in 4th Embodiment.

Hereinafter, embodiments in which the fuel injection control device of the present invention is embodied will be described with reference to the drawings.

<First Embodiment>
The first embodiment is embodied as a control system for controlling a gasoline engine for a vehicle. First, a schematic configuration of an engine control system will be described with reference to FIG.

An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 which is an in-cylinder injection type multi-cylinder internal combustion engine, and an air flow meter 14 for detecting the intake air amount is provided on the downstream side of the air cleaner 13. ing. On the downstream side of the air flow meter 14, a throttle valve 16 whose opening degree is adjusted by a motor 15 and a throttle opening degree sensor 17 for detecting the opening degree (throttle opening degree) of the throttle valve 16 are provided.

A surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 for detecting 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, and an electromagnetic fuel injection valve 30 that directly injects fuel into the cylinder is connected to each cylinder 21 of the engine 11. It is installed. 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 the spark discharge of the spark plug 22 of each cylinder 21.

The exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) that detects the air-fuel ratio of the air-fuel mixture or rich / lean based on the exhaust gas, and is downstream of the exhaust gas sensor 24. Is provided with a catalyst 25 such as a three-way catalyst that purifies the exhaust gas.

A cooling water temperature sensor 26 for detecting the cooling water temperature and a knock sensor 27 for detecting knocking are attached to the cylinder block of the engine 11. A crank angle sensor 29 that outputs a pulse signal each time the crank shaft 28 rotates a predetermined crank angle is attached to the outer peripheral side of the crank shaft 28, and the crank angle and engine rotation are based on the crank angle signal of the crank angle sensor 29. The speed is 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 by using detection signals of various sensors. The ECU 40 calculates the fuel injection amount according to the engine operating state to control the fuel injection of the fuel injection valve 30, and also controls the ignition timing of the spark plug 22. Electric power is supplied to the spark plug 22 and the fuel injection valve 30 from an in-vehicle battery 51.

The ECU 40 is composed of a microcomputer 41 for engine control (microcomputer for controlling the engine 11), a memory 42 for data backup, an electronic driving device (EDU: Electrical Driving Unit) 43 for driving an injector, and the like. The microcomputer 41 calculates the required injection amount according to the engine operating state (for example, engine rotation speed, engine load, etc.), generates an injection pulse from the injection time calculated based on the required injection amount, and outputs the injection pulse to the EDU 43. .. In the EDU 43, the fuel injection valve 30 is driven to open in response to the injection pulse to inject fuel corresponding to the required injection amount. The microcomputer 41 corresponds to the "fuel injection control device". The memory 42 is a storage unit such as a backup RAM or EEPROM that can retain the stored contents even after the IG switch is turned off.

The EDU 43 is provided with a drive IC 45, a low voltage power supply unit 46, a high voltage power supply unit 47, a voltage switching circuit 48, and a current detection circuit 49. The voltage switching circuit 48 is a circuit that switches the drive voltage applied to the fuel injection valve 30 of each cylinder 21 between the high voltage V2 and the low voltage V1. A drive current is supplied to the coil of the fuel injection valve 30 from either the power supply unit 46 or the high voltage power supply unit 47. The low voltage power supply unit 46 has a low voltage output circuit that applies the battery voltage (low voltage V1) of the battery 51 to the fuel injection valve 30. The high-voltage power supply unit 47 has a high-voltage output circuit (boost circuit) that applies a high voltage V2 (boost voltage) that boosts the battery voltage to a predetermined high voltage (for example, 40V to 70V) to the fuel injection valve 30. Therefore, these high voltage output circuits are provided for each fuel injection valve 30.

When the fuel injection valve 30 is driven to open by the injection pulse, the low voltage V1 and the high voltage V2 are switched and applied to the fuel injection valve 30 in chronological order. In this case, the high voltage V2 is applied at the initial stage of valve opening to ensure the valve opening responsiveness of the fuel injection valve 30, and the low voltage V1 is subsequently applied to ensure the valve opening state of the fuel injection valve 30. Is retained.

The current detection circuit 49 detects the energization current when the fuel injection valve 30 is driven to open, and the detection result is sequentially output to the drive IC 45. The current detection circuit 49 may have a well-known configuration, and has, for example, a shunt resistor and a comparator.

Here, the fuel injection valve 30 will be described with reference to FIG. The fuel injection valve 30 attaches a coil 31 that generates an electromagnetic force by energization, a needle 33 (valve body) that is integrally driven with the plunger 32 (movable core) by the electromagnetic force, and a plunger 32 in the valve closing direction. It has a spring member 34, a body 35 for accommodating a needle 33, and the like. The body 35 is a magnetic material and constitutes a magnetic circuit in the fuel injection valve 30.

When the energization of the coil 31 is started with the rise of the injection pulse, the plunger 32 and the needle 33 move to the valve opening position against the urging force of the spring member 34. As a result, the needle 33 is separated from the injection hole 36 of the body 35, the fuel injection valve 30 is opened, and fuel injection is performed. When the energization of the coil 31 is stopped due to the fall of the injection pulse, the plunger 32 and the needle 33 return to the valve closed position due to the urging force of the spring member 34, so that the fuel injection valve 30 is closed and the fuel injection is started. It will be stopped. In the following description, the position where the plunger 32 hits the stopper and further movement in the valve opening direction is restricted is referred to as a “full lift position” of the needle 33.

The body 35 is provided with a storage chamber 37 for accommodating the needle 33 and a pressure control chamber 38 for accommodating a command piston that slides in the valve opening direction and the valve closing direction according to a change in the fuel pressure inside. ing. The needle 33 is urged in the valve closing direction by applying fuel pressure to the plunger 32 via the command piston. As described above, in the configuration in which the needle 33 is urged to the valve closing position by using the fuel pressure, the higher the fuel pressure (fuel pressure), the lower the valve opening response at the time of fuel injection. When determining the injection pulse for the required injection amount, the injection pulse is adjusted according to the fuel pressure.

Next, with reference to FIG. 3, the driving operation of the fuel injection valve 30 carried out based on the injection pulse by the driving IC 45 and the voltage switching circuit 48 will be described.

At time ta1, a high voltage V2 is applied to the fuel injection valve 30 with the rise of the injection pulse. When the drive current reaches a predetermined target peak value Ip at time ta2, the application of the high voltage V2 is stopped. At this time, the needle lift is started at the timing when the drive current reaches the target peak value Ip or at the timing before and after that, and the fuel injection is started along with the needle lift. The determination of whether or not the drive current has reached the target peak value Ip is performed based on the detection current detected by the current detection circuit 49. That is, in the boosting period (ta1 to ta2), it is determined in the drive IC 45 whether or not the detected current is equal to or higher than Ip, and when the detected current ≥ the target peak value Ip, the voltage switching circuit 48 switches the applied voltage. (V2 application stop) is carried out.

At time ta3, the low voltage V1, which is the battery voltage, is applied to the fuel injection valve 30. As a result, after the needle 33 reaches the full lift position, the full lift state is maintained and fuel injection is continued. After that, when the injection pulse is turned off at time ta5, the voltage application to the fuel injection valve 30 is stopped and the drive current becomes zero. Then, the needle lift is terminated when the coil energization of the fuel injection valve 30 is stopped, and the fuel injection is stopped accordingly.

Here, the movement of the fuel injection valve 30 is affected by individual differences, deterioration over time, temperature, and the like. If the actual injection amount deviates from the required injection amount due to such an influence, it hinders the optimization of the fuel injection amount. Therefore, in the present embodiment, a correction value is calculated based on the energization characteristic which is a change in the energization current with respect to the drive command to the fuel injection valve 30, and the width of the injection pulse is increased or decreased by using the correction value. The excess and deficiency of fuel injection amount is reduced. Specifically, as shown in the example of FIG. 4, when the drive current of the fuel injection valve 30 changes to the actual waveform shown by the two-point chain line with respect to the target waveform shown by the solid line, comparing the two. , The slope in the current rising section when a high voltage is applied (that is, when energization starts), the integrated current value in the current rising section, the time until a predetermined current (for example, peak current) is reached, and the drive current after a predetermined time has elapsed. The sizes of the currents are different from each other. In such a case, in order to eliminate the difference from the target waveform, which is a predetermined standard waveform, a correction value is set with the above-mentioned current slope, current integrated value, arrival time of a predetermined current, and the like as parameters. For example, the correction value is set so that the output time of the injection pulse is extended when the injection amount is insufficient, and the output time of the injection pulse is shortened when the injection amount is excessive.

In the electromagnetically driven fuel injection valve 30, magnetic flux is generated as the fuel is energized. This magnetic flux increases as the current value rises and converges to a value corresponding to the current value (see, for example, time ta4 to ta5). The magnetic flux generated in this way does not disappear immediately after the end of energization, but remains in the magnetic material portion in the fuel injection valve 30 such as the coil 31, and gradually decreases with the passage of time. Then, the needle 33 disappears at the time ta7 after the time ta6 when the needle 33 returns to the valve closed position. In the following description, the magnetic flux remaining after the end of energization is referred to as a residual magnetic flux.

If the time from the end of the previous injection to the start of the next injection is less than the time required for the disappearance of the residual magnetic flux (several msec to several tens of msec), the effect of the residual magnetic flux is the next injection. If the required time is exceeded, the influence of the residual magnetic flux is prevented from extending to the next injection. For example, when the rotation speed is low, the interval time between injections becomes long, so that the influence of the residual magnetic flux can be easily avoided, and when the rotation speed is high, the interval time between injections becomes short, so that the residual magnetic flux The effect of is more likely to extend to the next injection.

Further, in the present embodiment, multi-stage injection in which fuel is injected a plurality of times in one combustion cycle is possible, and single-shot injection is executed in the case of low load and low rotation speed (for example, when idling). In other cases (for example, when the load is high or when acceleration is transient), multi-stage injection is executed. The interval time between the pre-stage injection (hereinafter referred to as the pre-stage injection) and the post-stage injection (hereinafter referred to as the post-stage injection) in the multi-stage injection is variable within a predetermined range and is set according to the engine rotation speed and the like. Here, if the interval time is shorter than the required time, the influence of the residual magnetic flux will affect the subsequent injection.

Hereinafter, the influence of the residual magnetic flux at the time of multi-stage injection will be described with reference to FIG. FIG. 5 exemplifies the pre-stage injection and the post-stage injection in the multi-stage injection, and for convenience of explanation, the changes in the current, the magnetic flux, and the position of the needle 33 when there is no influence of the residual magnetic flux are also shown by a two-dot chain line.

When energization for the previous stage injection is started at time tb1, the magnetic flux increases as the drive current increases. When the drive current decreases due to the end of application of the high voltage V2 (see tb2) and switching to the low voltage V1, the magnetic flux also decreases accordingly and converges to the value corresponding to the drive current at the low voltage V1 (time tb4). .. At the time tb5 when the energization is completed, the needle 33 starts moving from the full lift position to the valve closing position. Along with this, the residual magnetic flux will gradually decrease.

When the return of the needle 33 to the valve closed position is completed and the energization for the post-stage injection is started at the time tb6 where the magnetic flux remains, the current value rises rapidly under the influence of the residual magnetic flux, and the needle The movement of 33 in the valve opening direction is boosted. As described above, the responsiveness of the injection valve is higher than that in the case where there is no residual magnetic flux, so that the time required for the needle 33 to reach the full lift position is shortened (see time tb6 to tb8). As a result, when compared with the same pulse width, the time for the needle 33 to be held at the full lift position becomes longer than when there is no residual magnetic flux, and the actual fuel injection amount exceeds the required injection amount.

As already explained, the residual magnetic flux is most abundant immediately after the end of energization, and decreases with the passage of time. Therefore, the smaller the interval between the front and rear injections, the more remarkable the effect, and the larger the deviation between the actual fuel injection amount and the required injection amount.

Here, the above-mentioned correction value (correction value calculated based on the energization characteristic of the fuel injection valve 30) can be expected to be improved in certainty by obtaining an average or the like from the accumulated data in the past. However, the slope of the current waveform changes due to the influence of the residual magnetic flux. Therefore, it is feared that the calculation of the correction value based on the current waveform affected by the residual magnetic flux may reduce the certainty of the correction value and hinder the optimization of the fuel injection amount. Therefore, in the present embodiment, the correction value is calculated as a learning value based on the energization characteristic of the fuel injection valve 30, and whether or not the learning can be performed is determined by considering the influence of the residual magnetic flux when calculating the learning value. One of the features is to switch. In the present embodiment, in order to grasp the influence of the residual magnetic flux due to the previous fuel injection, the injection interval from the end of the previous fuel injection to the start of the next fuel injection is acquired as an interval time.

Specifically, as the learning process, the microcomputer 41 reaches the peak value (or a predetermined value before and after) the drive current after the start of application of the high voltage accompanying the on of the injection pulse as the energization characteristic of the fuel injection valve 30. During the period up to, the drive currents are sequentially integrated to calculate the current integrated value, and the learning value is calculated based on the difference between the current integrated value and the standard value of the predetermined current integrated value. The learning value is sequentially stored in the memory 42 for each learning area determined according to the engine operating state such as the engine rotation speed and the engine load. At this time, it is preferable that the previous value is updated by the current value while using the annealing process or the like. Then, the microcomputer 41 corrects the fuel injection amount by using the learning value when the fuel injection is performed. At this time, for example, various corrections such as water temperature and air-fuel ratio are performed on the basic injection amount calculated based on the engine rotation speed and the engine load, and further corrections are performed based on the learning value.

Hereinafter, the learning process will be described with reference to FIG. The learning process is a process that is periodically executed by the microcomputer 41, and is executed for each fuel injection valve 30.

In step S101 in the learning process, it is determined whether or not the injection pattern in the current fuel injection, specifically, the number of injections, the injection timing (interval time between injections), the injection amount, and the like are determined. In the present embodiment, for example, the injection pattern is determined near the exhaust top dead center. If a negative determination is made in step S101, this process ends as it is. If an affirmative determination is made in step S101, the process proceeds to step S102. In step S102, it is determined whether or not the current injection pattern is a single-shot injection. If it is determined that the single-shot injection is performed, the single-shot injection process is executed in step S103, and then this process is terminated. If it is determined that the injection is not a single injection but a multi-stage injection, the multi-stage injection process is executed in step S104, and then this process is terminated.

Here, the single-shot injection process will be described with reference to the flowchart of FIG. 7. In the single-injection process, first, in step S201, the interval time T1 in the front-rear cycle in the same fuel injection valve 30, specifically, the same fuel injection valve 30 is finally finished in the fuel injection in the previous cycle. The interval time T1 (intercycle interval time T1) from the start to the start of fuel injection in this cycle is acquired. In the present embodiment, the interval time T1 is the time from the end of the injection pulse in the previous fuel injection (timing of ta5 in FIG. 3) to the start of the injection pulse in the next fuel injection (timing of ta1 in FIG. 3). It is supposed to be.

In the following step S202, it is determined whether or not the interval time T1 is equal to or greater than the first reference time Ta. The first reference time Ta is a time specified based on the time required for the influence of the residual magnetic flux described above to disappear (specifically, a time equal to or longer than the required time).

If an affirmative judgment is made in step S202, learning about the current fuel injection is permitted and the present process is terminated. As a result, learning about the fuel injection this time will be executed. If a negative determination is made in step S202, learning about the fuel injection this time is prohibited and this process ends. As a result, learning is prohibited until the next injection pattern is determined.

Next, the multi-stage injection process will be described with reference to the flowchart of FIG. In the multi-stage injection process, first, in step S301, the interval time T1 in the front-rear cycle in the same fuel injection valve 30 is acquired. In the following step S302, the interval times T2 and T3 (interval interval times T2 and T3 in the cycle) between fuel injections in the same cycle are acquired. Specifically, when three fuel injections are carried out as multi-stage injection, the interval time T2 from the end of the first fuel injection to the start of the second fuel injection and the end of the second fuel injection. Then, the interval time T3 from that time to the start of the third fuel injection is acquired.

In the following step S303, it is determined whether or not the interval time T1 is equal to or greater than the first reference time Ta. If it is shorter than the first reference time Ta, learning is prohibited for all the first to third fuel injections in step S304, and this process is terminated.

Here, a specific embodiment of the multi-stage injection in the present embodiment will be supplementarily described with reference to FIG. 9, and learning is prohibited for all fuel injections when the interval time T1 between cycles is shorter than the first reference time Ta. Explain the reason for this.

The engine 11 shown in the present embodiment is a so-called four-cycle engine, and one cycle is composed of an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke. In the multi-stage injection, the first and second fuel injections are executed in the intake stroke, and the third fuel injection is executed in the compression stroke. The interval time T1 from the end of the last fuel injection in the previous cycle to the start of the first fuel injection in this cycle is from the length of two strokes (combustion stroke and exhaust stroke). Will also be longer. On the other hand, the interval time T2 from the end of the first fuel injection to the start of the second fuel injection and the interval time T3 from the second fuel injection time to the start of the third fuel injection are both two strokes. It will be shorter than the length of the minute. That is, when the interval time T1 which is the interval time between cycles is shorter than the first reference time Ta, both the interval times T2 and T3 which are the interval times in the cycle are shorter than the first reference time Ta. Therefore, when the interval time T1 is shorter than the first reference time Ta, learning is prohibited for all fuel injections.

Returning to the explanation of FIG. 8, when an affirmative judgment is made in step S303, that is, when the interval time T1 is equal to or longer than the first reference time Ta, learning about the first and second fuel injections in steps S305 to S309. Judge whether or not.

Specifically, the process first proceeds to step S305, and in this injection pattern, it is determined whether or not the interval time T2 from the end of the first fuel injection to the start of the second fuel injection is equal to or greater than the first reference time Ta. do. If an affirmative determination is made in step S305, the process proceeds to step S306 to permit learning about the first fuel injection.

If a negative determination is made in step S305, the process proceeds to step S307. In step S307, it is determined whether or not the interval time T2 is equal to or greater than the second reference time Tb. As shown in FIG. 10, the second reference time Tb is preferably shorter than the first reference time Ta and shorter than the difference from the first reference time Ta. It takes a certain amount of time for the arithmetic processing for learning in this embodiment. It is not preferable that the next learning is started even though the arithmetic processing is not completed because it hinders the normal progress of the arithmetic processing. The second reference time Tb is a time specified based on the time required for arithmetic processing (specifically, a time equal to or longer than the required time).

If an affirmative determination is made in step S307, that is, if the interval time T2 is shorter than the first reference time Ta and equal to or greater than the second reference time Tb, the process proceeds to step S308. In step S308, learning is permitted for the first fuel injection, and learning is prohibited for the second fuel injection.

If a negative determination is made in step S307, that is, if the interval time T2 is shorter than the second reference time Tb, the process proceeds to step S309. In step S309, learning about the first fuel injection and the second fuel injection is prohibited.

After the processing of steps S306, S308, and S309 is executed, it is determined in steps S310 to S317 whether or not learning is possible for the second and third fuel injections.

Specifically, first, the process proceeds to step S310, and it is determined whether or not the interval time T3 from the end of the second injection to the start of the third injection is equal to or greater than the first reference time Ta in the current injection pattern. If an affirmative determination is made in step S310, the process proceeds to step S311. In step S311, it is determined whether or not learning about the second fuel injection is prohibited. If an affirmative determination is made in step S311, the process is terminated after learning about the third fuel injection is permitted. If a negative determination is made in step S311, the process proceeds to step S313. In step S313, learning is permitted for the second fuel injection and the third fuel injection, and this process ends.

Returning to the description of step S310, if a negative determination is made in step S310, that is, if the interval time T3 is shorter than the first reference time Ta, the process proceeds to step S314. In step S314, it is determined whether or not the interval time T3 is equal to or longer than the second reference time Tb. If an affirmative determination is made in step S314, the process proceeds to step S315.

In step S315, it is determined whether or not learning about the second fuel injection is prohibited. If a negative determination is made in step S315, the process proceeds to step S316. In step S316, learning about the second fuel injection is permitted, and learning about the third fuel injection is prohibited.

If an affirmative determination is made in step S315 or a negative determination is made in step S314, the process proceeds to step S317. In step S317, learning about the second fuel injection and the third fuel injection is prohibited.

According to the above-mentioned multi-stage injection process, learning (calculation of correction value) for each fuel injection before and after the injection interval, provided that the injection interval (interval time) before and after the injection interval is larger than the first reference time Ta. Is permitted, while learning in the previous fuel injection of each fuel injection before and after the injection interval is permitted provided that the injection interval is smaller than the first reference time Ta and larger than the second reference time Tb. It has become so.

Here, with reference to the example of FIG. 11, the relationship between the change in the engine rotation speed and the learning possibility when the multi-stage injection is executed will be described. In FIG. 8, "〇" is shown for the subjects for which learning is permitted, and "x" is indicated for the subjects for which learning is prohibited.

As shown in FIG. 11A, when the rotation speed of the engine 11 is low, the influence of the residual magnetic flux disappears while the interval time between cycles elapses. Further, also for the second fuel injection and the third fuel injection, a sufficient length is secured in consideration of the disappearance of the residual magnetic flux in the interval time in the cycle. Therefore, learning is permitted for all fuel injections from the first to the third.

As shown in FIG. 11A → FIG. 11B, the rotation speed of the engine 11 is increased, so that the time required for one cycle, that is, the time required for each stroke is shortened. As a result, both the interval time between cycles and the interval time within the cycle are shortened. In the example shown in FIG. 8B, the interval time from the end of the second injection to the start of the third injection exceeds the first reference time Ta. That is, the residual magnetic flux generated by the second fuel injection is eliminated by the time the third fuel injection is started. On the other hand, the interval time from the end of the first injection to the end of the second injection is less than the first reference time Ta. That is, the residual magnetic flux generated by the first fuel injection is not eliminated by the second fuel injection. For this reason, learning about the third fuel injection is permitted, while learning about the second fuel injection is prohibited.

As shown in FIG. 11 (b) → FIG. 11 (c), when the rotation speed of the engine 11 further increases to a high rotation speed, the time required for one cycle, that is, the time required for each stroke is compared with the case of medium rotation. Is shortened. If the residual magnetic flux due to the first fuel injection is not eliminated by the second fuel injection, the learning about the third injection that was permitted until then is also prohibited, and the learning target is limited to the first fuel injection. The Rukoto.

According to the first embodiment described in detail above, the following excellent effects are obtained.

When fuel injection is repeated, the magnetic flux generated during the previous fuel injection may remain until the next fuel injection (specifically, the rising section of the current waveform). When learning is performed under the influence of such residual magnetic flux, there is a concern that the certainty of the correction value calculated by the learning will decrease. Therefore, as shown in this embodiment, the correction value is set so that learning is permitted only for fuel injection that is not affected by the residual magnetic flux, and learning is prohibited for fuel injection that is affected by the residual magnetic flux. It is possible to suppress the decrease in certainty.

In particular, in multi-stage injection in which fuel injection is executed a plurality of times in one combustion cycle, the interval time between fuel injections (intermbal time in the cycle) becomes short. Therefore, the influence of the previous fuel injection is more likely to extend to the next fuel injection as compared with the single injection in which the fuel injection is executed once in one combustion cycle. In the present embodiment, when multi-stage injection is executed, it is configured to determine whether or not learning is possible for each fuel injection in one combustion cycle, and those that are not affected by the residual magnetic flux are included in the learning target. This makes it possible to increase learning opportunities.

In a configuration in which a correction value is calculated based on past results, the time required for arithmetic processing tends to increase. If learning is newly started while the arithmetic processing is being executed, it may cause a malfunction of the arithmetic processing or the like. Therefore, as shown in the present embodiment, the second reference time Tb is set based on the time required for the calculation process, and the second reference time Tb is used to determine whether or not learning is possible, so that the calculation cannot be completed in time. In such a situation, learning related to the next fuel injection can be prohibited. Thereby, the occurrence of the above-mentioned inconvenience can be suitably suppressed.

A configuration in which the first reference time Ta corresponding to the residual magnetic flux and the second reference time Tb corresponding to the calculation processing of the correction value are used in combination to determine whether or not learning is possible for the first fuel injection and the next fuel injection. By doing so, the certainty of the correction value can be suitably improved. The second reference time Tb is shorter than the first reference time Ta. Therefore, it is suppressed that the learning opportunity is greatly reduced due to the existence of the second reference time Tb.

A configuration in which the high voltage V2 is applied by the high voltage power supply unit 47 and then the low voltage V1 is applied by the low voltage power supply unit 46 is preferable in order to stabilize the operation of the fuel injection valve 30. However, when the high voltage V2 is used, the generated magnetic flux becomes large, so that the influence of the magnetic flux easily extends to the next fuel injection. If a function for determining whether or not learning is possible is added to such a configuration in consideration of the influence of the residual magnetic flux, a practically preferable configuration can be realized.

<Second Embodiment>
In the first embodiment, the permission / prohibition of learning is determined based on the interval time between the previous fuel injection and the next fuel injection in the same cylinder. The configuration of the present embodiment is different from that of the first embodiment in that learning permission / prohibition is determined in consideration of not only fuel injection in the same cylinder but also fuel injection in other cylinders. .. Hereinafter, the premise configuration in the present embodiment will be described with reference to the block diagram of FIG. 12, focusing on the differences from the first embodiment.

The engine 11 is a 4-cylinder engine, and for convenience, the combustion order of each cylinder 21 is # 1 → # 2 → # 3 → # 4. The EDU 43 is provided with a first supply path for supplying electric power to the # 1 fuel injection valve and the # 3 fuel injection valve, and a second supply path for supplying electric power to the # 2 fuel injection valve and the # 4 fuel injection valve, respectively. Has been done.

A first voltage switching circuit 48a is provided in the first supply path, and the low voltage power supply unit 46 and the first high voltage power supply unit 47a are connected to the first voltage switching circuit 48a. A second voltage switching circuit 48b is provided in the second supply path, and the low voltage power supply unit 46 and the second high voltage power supply unit 47b are connected to the second voltage switching circuit 48b. The first high-voltage power supply unit 47a and the second high-voltage power supply unit 47b each have a storage unit such as a capacitor, and a high voltage is applied to the # 1 fuel injection valve and the # 3 fuel injection valve from the first high-voltage power supply unit 47a. Then, a high voltage is applied to the # 2 fuel injection valve and the # 4 fuel injection valve from the second high voltage power supply unit 47b.

As shown in the timing chart of FIG. 13, when fuel injection is executed in the order of # 1 → # 2 → # 3 → # 4, the # 1 fuel injection valve of the # 1 cylinder is energized before the next combustion. The # 3 fuel injection valve of the # 3 cylinder is energized until the # 1 fuel injection valve is energized in the cycle.

In the learning process in the present embodiment, for example, when learning fuel injection in the # 3 fuel injection valve, the fuel injection end in the # 1 fuel injection valve (specifically, the application end of the high voltage V2) to the # 3 fuel injection valve is performed. The interval time T6 until the start of fuel injection is calculated, and the fuel injection in the # 3 fuel injection valve is performed based on whether or not this interval time T6 is equal to or longer than the reference time set based on the storage required time of the power storage unit. Decide whether or not to study. Specifically, when the interval time T6 is equal to or longer than the reference time, learning is permitted, and when the interval time T6 is shorter than the reference time, learning is prohibited.

The supply source of the high voltage V2 is common to the # 1 fuel injection valve and the # 3 fuel injection valve (first high voltage power supply unit 47a). When the high-voltage power supply unit is shared by a plurality of fuel injection valves in this way, the supply path can be simplified, but the following events may occur. That is, as the power supply pitch increases due to an increase in the engine rotation speed or the like, there is a possibility that the electric power storage unit may not be able to store the electric power in time. If the storage level of the high voltage portion drops, the voltage applied to the fuel injection valve drops, and the above-mentioned current waveform may deviate. Therefore, by prohibiting learning when there is a possibility that the storage capacity will not be in time, it is possible to suppress a decrease in the certainty of the correction value obtained by learning.

<Third Embodiment>
There is a relationship between the number of injections in multi-stage injection and the interval time. One of the features of the present embodiment is to pay attention to such a relationship and determine whether or not to calculate the correction value based on the number of injections in one combustion cycle. The number of injections in the multi-stage injection corresponds to the information that correlates with the injection interval. Hereinafter, the learning process in the present embodiment will be described with reference to the flowchart of FIG. 14, focusing on the differences from the first embodiment.

In the learning process in the present embodiment, first, in step S401, it is determined whether or not the injection pattern is at the determined timing. If a negative determination is made in step S401, this process ends as it is. If an affirmative determination is made in step S401, the process proceeds to step S402. In step S402, it is determined whether or not the number of injections in one combustion cycle is a predetermined number or less (2 or less in this embodiment) with reference to the current injection pattern. For the multi-stage injection in the present embodiment, the number of injections is set to 2 to 3 based on the rotation speed and the load of the engine 11.

When one is set as the number of injections, the interval time between cycles exceeds the first reference time Ta. Further, when the number of injections is set to two, the interval time between cycles and the interval time within the cycle exceed the first reference time Ta. That is, in the injection pattern in which the number of injections is once or twice, the influence of the magnetic flux generated in the previous fuel injection does not affect the next fuel injection. Therefore, in these cases, learning about fuel injection in this combustion cycle is permitted (step S403).

On the other hand, when the number of injections is set to 3, the interval time between cycles and the interval time within the cycle may be shorter than the first reference time Ta. Therefore, when the number of injections exceeds a predetermined number, learning in the current combustion cycle is prohibited (step S404).

If there is a relationship between the number of injections and the interval time, the number of injections that is not affected by the residual magnetic flux is specified in advance from that relationship, and learning is determined based on the number of injections. It is possible to suitably improve the certainty of the correction value while securing an opportunity.

<Fourth Embodiment>
In the multi-stage injection, the injection interval (interval time) between the immediately preceding fuel injection differs between the initial injection and the subsequent injection. One of the features of the actual embodiment is to determine whether or not the correction value can be calculated based on whether or not it is the first injection of the multi-stage injection. Hereinafter, the learning process in the present embodiment will be described with reference to the flowchart of FIG.

In the learning process, first, in step S501, it is determined whether or not the injection pattern is determined. If a negative determination is made in step S501, this process is terminated as it is. If an affirmative determination is made in step S501, the process proceeds to step S502. In step S502, it is determined whether or not the current fuel injection corresponds to the multi-stage injection by referring to the current injection pattern.

The multi-stage injection in the present embodiment is configured so that the interval time between cycles is equal to or longer than the first reference time Ta. On the other hand, the interval time in the cycle may not exceed the first reference time Ta depending on the engine speed.

Therefore, when the injection pattern determined this time is multi-stage injection, learning is permitted only for the first fuel injection (first injection) in step S503, and when the injection pattern this time is single injection, step S504 is permitted. Allows learning about the single injection at.

With such a configuration, even when multi-stage injection is executed, it is possible to secure an opportunity for learning while avoiding the influence of the residual magnetic flux.

<Other embodiments>
-In each of the above embodiments, when the fuel injection pattern is determined, the learning availability is determined for each fuel injection, but the timing for determining the learning availability is arbitrary. For example, it may be configured to determine whether or not learning is possible at the timing when fuel injection is actually started.

-In each of the above embodiments, the length of the injection pulse is changed by using the correction value, but it is sufficient if the deviation between the required injection amount and the actual injection amount can be suppressed. For example, it may be configured to change the boost amount in the high voltage power supply unit, or it may be configured to change the set value of the peak current.

-In the above embodiment, the fuel injection amount is corrected by using the learning value, but instead of this, the time width of the injection pulse is corrected by using the learning value, and the high voltage V2 when a high voltage is applied. It is also possible to adopt either a configuration for correcting the above voltage or a configuration for correcting the target peak current when a high voltage is applied.

-In the above embodiment, the interval time from the end of the previous fuel injection to the start of the next fuel injection is set as the interval time, but it may be other than this. For example, the interval time from the start of the previous fuel injection to the start of the next fuel injection may be set. Alternatively, the interval time may be from the time when the peak current of the previous fuel injection is reached to the start of the next fuel injection.

-The fuel injection control device of the present invention can be applied not only to a gasoline engine but also to a diesel engine. That is, it can be applied to a fuel injection control device that controls a fuel injection valve of a direct injection diesel engine.

As a countermeasure at the time of unlearning after clearing the battery, the fuel injection valve 30 may be driven by applying a low voltage V1 from the low voltage power supply unit 46 in order to avoid misfire.

-In the case of digital control, there is a minimum resolution in the drive voltage for the fuel injection valve. In such a configuration, it is preferable to use the voltage closest to the smaller side in order to prevent misfire due to insufficient energy. In addition, it is preferable to use a rounded value in order to prevent the injection amount from shifting due to excessive energy.

11 ... Engine (internal combustion engine), 30 ... Fuel injection valve, 41 ... Microcomputer (fuel injection control device).

Claims (1)

It is applied to a fuel injection system provided with a fuel injection valve (30) for injecting fuel in the internal combustion engine (11) and capable of performing multi-stage injection in which fuel is injected a plurality of times in one combustion cycle, and is driven by the fuel injection valve. A fuel injection control device that detects a change in the energization current with respect to a command as an energization characteristic and calculates a correction value for energization control of the fuel injection valve based on the detected energization characteristic.
Upon fuel injection by the fuel injection valve, a determination unit for determining whether or not the injection interval is larger than a predetermined time based on the injection interval from the previous fuel injection to the next fuel injection or information correlating with the injection interval.
When it is determined by the determination unit that the injection interval is larger than the predetermined time, the calculation of the correction value in the next fuel injection is permitted, and it is determined that the injection interval is smaller than the predetermined time. In addition, a correction value calculation unit that prohibits the calculation of the correction value in the next fuel injection,
Equipped with
As the predetermined time, the first reference time for determining whether or not the residual magnetic flux remaining after the previous fuel injection affects the subsequent fuel injection when the multi-stage injection is performed is set, and the first reference time is set. The second reference time, which is shorter than one reference time and is the time required to calculate the correction value for each individual injection in the multi-stage injection, is set.
The correction value calculation unit permits the calculation of the correction value in each fuel injection before and after the injection interval on condition that the injection interval is larger than the first reference time, and the injection interval is the first. On condition that it is smaller than one reference time and larger than the second reference time, the calculation of the correction value in the previous fuel injection among the fuel injections before and after the injection interval is permitted, and the injection interval is the said. A fuel injection control device that does not allow the calculation of the correction value in each fuel injection before and after the injection interval on condition that it is smaller than the second reference time .

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