JP7459834B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

The disclosure in this specification relates to a fuel injection control device for an internal combustion engine.

In this type of fuel injection control device, when the fuel injection device is energized, the valve element is lifted to open the injection hole, thereby injecting fuel. Another type of fuel injection device known is a so-called flying needle type, which injects fuel with the valve element in a medium lift state. This type of fuel injection device has the advantage that by not abutting the valve element against the upper limit stopper, it is possible to reduce the variation in the injection amount caused by the valve element bouncing, and the variation in the upper limit stopper position caused by individual differences and changes over time.

Furthermore, in Patent Document 1, in one injection opportunity, energization and de-energization are performed multiple times with the valve body in an intermediate lift state, thereby suppressing the enlargement of the fuel injection device and injecting a large amount of fuel. The technology that makes fuel injection possible is described. In this case, after the first energization is cut off, the second energization is started before the valve body reaches the valve closing position, so that fuel injection is continued through the first energization and the second energization. ing.

US Patent Application Publication No. 2020/0063694

However, in the technology of Patent Document 1, when current is applied and cut off multiple times while the valve body is in a mid-lift state during one injection opportunity, if, for example, a sliding abnormality occurs in the valve body, the operating speed (lift speed) of the valve body when it is lifted up and down decreases. Then, due to the change in lift speed, a temporary decrease in the injection rate occurs after the end of the first stage of current application. When such a temporary decrease in injection rate occurs, there is a concern that inconveniences such as an unintended reduction in the fuel injection amount may occur.

The present invention was made in consideration of the above circumstances, and aims to provide a fuel injection control device for an internal combustion engine that can properly perform fuel injection control when multiple stages of current are applied during a single injection opportunity.

The fuel injection control device for an internal combustion engine according to the present invention includes a drive section that is driven by energization, and a valve body that opens an injection hole according to the drive of the drive section, Applied to a fuel injection system including a fuel injection device that realizes a maximum injection rate by changing the injection amount and achieving an intermediate lift state in which the lift amount of the valve body becomes a predetermined intermediate lift amount,
The drive unit is energized multiple times intermittently during one injection occasion, and the fuel injection device is configured to inject fuel at the maximum injection rate in the intermediate lift state through each energization before and after the energization. A fuel injection control device that performs injection,
an abnormality determination unit that determines that an injection rate decrease has occurred after the first stage of energization is completed when multi-stage energization is performed in at least two stages for one injection opportunity;
When the abnormality determination unit determines that a decrease in the injection rate has occurred, the energization time of the first stage is extended and corrected while maintaining the energization time of the second and subsequent stages and the interval time between the energization times of each stage. , a first energization control unit that performs the multi-stage energization according to the corrected energization time;
an excessive amount calculation unit that calculates an excessive injection amount in the multi-stage energization in a state where the first energization control unit performs the multi-stage energization;
a second energization control unit that corrects the energization time in the second and subsequent stages based on the excessive injection amount and performs the multi-stage energization according to the corrected energization time;
Equipped with.

In the present invention, when a drop in the injection rate occurs due to a drop in the lift speed of the valve body, the current conduction time of the first stage is extended and corrected while maintaining the current conduction time of the second stage and subsequent stages and the interval time between the current conduction times of each stage, and multi-stage current is performed using the corrected current conduction time. This suppresses a drop in the injection rate after the end of the first stage current even in a situation where the lift speed of the valve body has decreased. In addition, when the current conduction time of the first stage is extended and corrected, the injection amount in the fuel injection by multi-stage current is excessive, but the current conduction time of the second stage and subsequent stages is corrected based on the excessive injection amount, and multi-stage current is performed using the corrected current conduction time. This makes it possible to inject an appropriate amount of fuel. As a result, fuel injection control can be performed appropriately when multi-stage current is performed during one injection opportunity.

1 is a diagram showing an outline of a fuel injection system; FIG. 2 is a cross-sectional view showing the internal structure of the fuel injection device. A time chart showing a series of fuel injection processes. 4 is a time chart showing the state of fuel injection when an abnormality occurs; 5 is a time chart showing the state of fuel injection during abnormality. 5 is a time chart showing the state of fuel injection during abnormality. 5 is a time chart showing a first energization correction mode; 5 is a time chart showing a second energization correction mode; 5 is a flowchart showing a process for determining each abnormality. 5 is a flowchart showing a processing procedure for fuel injection control. The time chart which shows the mode of re-extension of the energization time in another example. FIG. 11 is a diagram showing a relationship between a slope of a fuel pressure decrease and a correction time in a modified example. 9 is a time chart showing a state of fuel injection in an abnormal state in another example.

The following describes an embodiment with reference to the drawings. In this embodiment, a fuel injection control device is embodied that controls fuel injection by a fuel injection device in a common rail fuel injection system (accumulator type fuel injection system) that controls, for example, an on-board diesel engine.

In FIG. 1, a four-cylinder diesel engine (hereinafter referred to as engine 10) serving as an internal combustion engine is provided with a fuel injection device 11 for each cylinder, and these fuel injection devices 11 are connected to a common rail 12 (pressure accumulation pipe) common to each cylinder. It is connected. A high-pressure pump 13 as a fuel pump is connected to the common rail 12, and as the high-pressure pump 13 is driven, the pressure of the fuel is increased, and high-pressure fuel equivalent to the injection pressure is continuously accumulated in the common rail 12. The high-pressure pump 13 is driven as the engine 10 rotates, and repeatedly sucks and discharges fuel in synchronization with the engine rotation. The high-pressure pump 13 is provided with an electromagnetically driven suction metering valve (SCV) 13a in the fuel suction section, and the low-pressure fuel pumped up from the fuel tank 15 by the feed pump 14 is passed through the suction metering valve 13a. The fuel is sucked into the fuel chamber of the high-pressure pump 13. In addition, in the high-pressure pump 13, a discharge regulating valve (PCV) may be provided in place of the suction regulating valve 13a, and when a discharge regulating valve is provided, the fuel in the fuel chamber of the high-pressure pump 13 is discharged. It is discharged to the common rail via a valve.

The structure of the fuel injection device 11 will now be described with reference to Figure 2. Note that in Figure 2, the up-down direction indicates the axial direction of the fuel injection device 11, and the bottom side of the figure is the tip side of the fuel injection device 11.

In the fuel injection device 11, a fixed plate 40 is integrally provided inside the body 31, and a nozzle needle 32 as a valve body is housed in a reciprocating state on the distal side of the fixed plate 40. ing. The nozzle needle 32 slides within the body 31. The nozzle needle 32 has a front end sliding portion 32a on the axial front end side and a rear end sliding portion 32b on the axial rear end side. Note that the tip-side sliding portion 32a is provided in a plurality of sections in the circumferential direction of the nozzle needle 32, and a fuel passage through which fuel flows is formed between each tip-side sliding portion 32a.

A plurality of nozzle holes 33 are formed at the tip of the body 31. The nozzle hole 33 communicates with a sac chamber 46 formed between the distal end surface of the nozzle needle 32 and the body 31, and fuel flows from the nozzle hole 33 through the sac chamber 46 in accordance with the lift operation of the nozzle needle 32. Injection takes place. In this case, the tip of the nozzle needle 32 contacts the seat portion 31a of the body 31, thereby closing the nozzle hole 33 and stopping fuel injection. Moreover, when the tip of the nozzle needle 32 separates from the seat portion 31a, the nozzle hole 33 is opened and fuel injection is performed.

A high-pressure passage 34 is formed in the body 31 and the fixed plate 40 so as to penetrate the fixed plate 40. The high-pressure passage 34 is provided in a range that passes through the periphery of the nozzle needle 32 and reaches the tip of the fuel injection device 11, i.e., the nozzle hole 33, and high-pressure fuel supplied from the common rail 12 is guided to the nozzle hole 33 via this high-pressure passage 34.

A pressure sensor 45 is attached to the fuel injection device 11 to detect the fuel pressure within the high pressure passage 34 . By installing a pressure sensor 45 in the high pressure passage 34, the fuel pressure in the high pressure passage 34 can be detected at any time. Specifically, from the output of the pressure sensor 45, it is possible to detect fluctuations in fuel pressure associated with the injection operation of the fuel injection device 11.

A cylindrical cylinder 35 is attached to the tip end surface (lower end surface in the figure) of the fixed plate 40, and the upper end portion (rear end sliding portion 32b) of the nozzle needle 32 is slidably inserted into the cylinder 35. The nozzle needle 32 is biased in the valve closing direction by a spring 36 provided on the tip side of the cylinder 35. A pressure control chamber 37 is provided above the nozzle needle 32 within the cylinder 35. The pressure control chamber 37 can be filled with high-pressure fuel, and when the pressure control chamber 37 is filled with high-pressure fuel, the high-pressure fuel maintains the nozzle needle 32 in a closed state.

The fixed plate 40 is formed with an inflow passage 41 that allows high-pressure fuel to flow into the pressure control chamber 37, and an outflow passage 42 that allows fuel to flow out from the pressure control chamber 37. The inflow passage 41 branches off from the high-pressure passage 34, and an orifice that limits the fuel flow rate is formed in its downstream portion (i.e., the portion that leads to the pressure control chamber 37). In addition, an orifice that limits the fuel flow rate is formed in the downstream portion of the outflow passage 42 (i.e. the portion that leads to the low-pressure chamber 64, which will be described later).

A disk-shaped movable plate 50 is disposed within the pressure control chamber 37. The movable plate 50 is disposed so as to face the lower end surface of the fixed plate 40, and is movable within the pressure control chamber 37 in the vertical direction in the figure. A communication passage 51 that connects the outflow passage 42 and the pressure control chamber 37 is formed in the movable plate 50. An orifice that limits the fuel flow rate is formed in the downstream portion of the communication passage 51. When the movable plate 50 abuts against the fixed plate 40, it closes the outlet portion of the inflow passage 41, but maintains communication between the pressure control chamber 37 and the outflow passage 42 via the orifice of the communication passage 51. A spring 38 that presses the movable plate 50 against the fixed plate 40 is provided within the pressure control chamber 37.

Since the outer diameter of the movable plate 50 is smaller than the inner diameter of the cylinder 35, a gap is formed between the outer circumferential surface of the movable plate 50 and the inner circumferential surface of the cylinder 35. Therefore, when the movable plate 50 is separated from the fixed plate 40, the high-pressure fuel in the inflow passage 41 flows into the pressure control chamber 37 (specifically, the upper surface side of the nozzle needle 32) through the gap on the outer periphery of the movable plate 50. do.

In addition, inside the body 31, an electric actuator 60 serving as a drive unit is housed on the opposite tip side of the fixed plate 40. The electric actuator 60 has a solenoid coil 61, a control valve 62 serving as a valve member, and a spring 63 serving as a biasing member. The control valve 62 is inserted into a through hole 31b provided in the body 31, and is able to slide up and down in the low pressure chamber 64 while in contact with the inner circumferential surface of the through hole 31b. When the solenoid coil 61 is not energized, the biasing force of the spring 63 holds the control valve 62 against the fixed plate 40, and the fuel injection device 11 is held in a closed state.

When the solenoid coil 61 is energized, the control valve 62 moves away from the fixed plate 40 against the biasing force of the spring 63. Then, the movement of the control valve 62 causes the high-pressure fuel in the pressure control chamber 37 to flow out to the low-pressure chamber 64 through the outflow passage 42 of the fixed plate 40 and the communication passage 51 of the movable plate 50, and the nozzle needle 32 moves to the open side. This causes the injection hole 33 to open and fuel injection to begin. At this time, the nozzle needle 32 lifts from the closed position, gradually increasing the injection rate (i.e., the injection amount per unit time). When the needle lift amount reaches a predetermined lift amount at which the opening area of the seat portion 31a (i.e., the gap area between the seat portion 31a and the nozzle needle 32) is equal to the total cross-sectional area of the injection hole 33, the injection rate becomes the maximum injection rate, and after the needle lift amount reaches the predetermined lift amount, the maximum injection rate state is maintained.

In the fuel injection device 11 of this embodiment, when the needle lift amount reaches a predetermined lift amount at which the maximum injection rate is realized, the nozzle needle 32 does not hit the upper limit stopper (e.g., the movable plate 50) on the valve opening side, and fuel is injected in an intermediate lift state (floating state). The fuel injection device 11 has a so-called flying needle structure in which the maximum injection rate is achieved when the needle lift amount reaches a predetermined intermediate lift amount, and fuel injection is realized in that state.

When the solenoid coil 61 is de-energized and the control valve 62 abuts against the fixed plate 40 due to the biasing force of the spring 63, the outflow passage 42 is closed and in this state the movable plate 50 is pushed down by the high-pressure fuel from the inflow passage 41. This causes high-pressure fuel to flow into the pressure control chamber 37, pushing the nozzle needle 32 down to the valve closing side and returning the nozzle hole 33 to the closed state.

Note that in the electric actuator 60, it is also possible to use a driving section including a piezo element. That is, it is also possible to use a piezo-driven fuel injection device as the fuel injection device 11.

Returning to FIG. 1, the ECU 20 is an electronic control unit equipped with a well-known microcomputer 21 (microcomputer) consisting of a CPU and various memories (RAM, ROM, etc.), and performs various controls using control programs stored in the ROM. implement. In addition to the detection signals from the pressure sensor 45 described above, the microcomputer 21 receives detection signals from various sensors such as a rotation speed sensor that detects the engine rotation speed, an accelerator opening sensor that detects the accelerator opening, and a vehicle speed sensor that detects the vehicle speed. Signals are input sequentially. Then, the microcomputer 21 determines the fuel injection amount and injection timing as the fuel injection mode based on engine operation information such as the engine rotation speed and the accelerator opening, and controls the fuel injection by the fuel injection device 11 accordingly. Through such fuel injection control, fuel injection from the fuel injection device 11 to the combustion chamber in each cylinder is controlled.

In the ECU 20, the microcomputer 21 generates an energization pulse as an energization command signal, and outputs the energization pulse to the drive circuit 22. As is well known, the drive circuit 22 has a high-voltage power source and a low-voltage power source, and at the beginning of energization with the rise of the energization pulse, the drive circuit 22 is configured to open the fuel injection device 11 at high speed. The fuel injection device 11 is maintained in an open state by applying a high voltage to the drive unit (an electric actuator 60 described later) and then switching the applied voltage from the high voltage to the low voltage.

In a configuration in which fuel is injected using a fuel injection device 11 with a flying needle structure, the nozzle needle 32 is not brought into contact with the upper limit stopper, which has the advantage of reducing the variation in the injection amount caused by the bouncing of the nozzle needle 32 and the variation in the upper limit stopper position due to individual differences and changes over time. However, on the other hand, there is a concern that the amount of fuel that can be injected in one injection opportunity will be limited. In this case, while the injection period is limited due to the constraint that the nozzle needle 32 does not reach the upper limit stopper, if the injection period is to be extended, it is necessary to expand the lift region from the closed position to the upper limit stopper, which is a concern that will lead to an increase in the size of the fuel injection device 11.

In this embodiment, the number of times the fuel injection device 11 is energized in one injection opportunity is determined, and each injection is performed so that fuel injection at the maximum injection rate in the intermediate lift state is performed during the injection period during which the energization is performed. The energization time Tq of the stage and the interval time TINT between each energization are set. Then, the electric actuator 60 is energized based on the set energization time Tq of each stage and the interval time TINT.

Figure 3 is a time chart to explain the behavior when the nozzle needle 32 of the fuel injection device 11 is lifted at an intermediate lift amount below the lift upper limit Lmax and fuel is injected in that state. The lift upper limit Lmax is the maximum lift amount before the nozzle needle 32 hits the upper limit stopper on the valve opening side. Figure 3 shows the behavior when the fuel injection device 11 is energized with two current periods, one before and one after, and one after, one after two current periods are used to perform one fuel injection. Here, the current period by the first current pulse is Tq1, the current period by the second current pulse is Tq2, and the interval between the first and second current pulses is TINT. Note that in Figure 3, the pressure detected by the pressure sensor 45 is shown as the fuel pressure.

In FIG. 3, at timing t1, the first-stage energization pulse is raised, and fuel injection is started with the start of energization. At this time, at the beginning of the energization, a high current is applied by applying a high voltage to the solenoid coil 61 in order to open the nozzle needle 32 of the fuel injection device 11 at high speed, and then the applied voltage is changed to a high voltage. By switching from to a low voltage, a holding current is applied to maintain the nozzle needle 32 in an open state. Note that there is a delay time Td1 from when the first-stage energization is performed until the lift-up of the nozzle needle 32 is started.

After the current starts flowing at timing t1, the lift amount of the nozzle needle 32 (needle lift amount) gradually increases. At this time, the needle lift amount increases in proportion to the duration of current flow. In addition, the injection rate increases with the lift of the nozzle needle 32, and the fuel pressure decreases with the increase in the injection rate.

At timing t2, the needle lift amount reaches a predetermined lift amount at which the opening area of the seat portion 31a and the total cross-sectional area of the injection holes 33 become equal, and the injection rate becomes the maximum injection rate. In FIG. 3, the needle lift amount at which the injection rate becomes the maximum injection rate (that is, the needle lift amount at which the opening area of the seat portion 31a and the total cross-sectional area of the nozzle holes 33 become equal) is set as the lift lower limit Lmin. After timing t2, the injection rate remains at the maximum injection rate, and the fuel pressure is maintained substantially constant.

At timing t3 when a predetermined energization time Tq1 has elapsed from the start of energization, energization is temporarily stopped as the energization pulse falls. As a result, the needle lift amount changes from increasing to decreasing at the timing when the delay time Td2 has elapsed from timing t3. At this time, the needle lift amount changes from rising to falling without exceeding the lift upper limit Lmax of the fuel injection device 11.

After timing t3, the needle lift amount decreases in proportion to the duration of the de-energization. In this case, however, because the needle lift amount is greater than the lower lift limit Lmin, the maximum injection rate is maintained even after the first stage de-energization. In other words, the range from the lower lift limit Lmin to the upper lift limit Lmax is the intermediate lift region Rf, and because the needle lift amount is within the intermediate lift region Rf, the maximum injection rate is maintained.

Thereafter, at timing t4 when a predetermined interval time TINT has elapsed since the energization was stopped, the second stage energization pulse is raised, and the needle lift amount changes to increase again at a timing when a delay time Td3 has elapsed from timing t4. At this time, at timing t4, the energization of the solenoid coil 61 is restarted before the needle lift amount reaches the lift lower limit Lmin. During the second stage of energization, similarly to the first stage of energization, application of high voltage at the beginning of energization and subsequent switching to application of low voltage are performed. After the energization is resumed at timing t4, the needle lift amount increases again in proportion to the duration of energization, and the maximum injection rate is maintained as it is.

At timing t5, when a predetermined energization time Tq2 has elapsed from the start of energization in the second stage, energization is stopped as the energization pulse falls, and at a timing when a delay time Td4 has elapsed from timing t5, the needle lift amount changes from rising to falling. Turn. Thereafter, when the needle lift amount falls below the lift lower limit Lmin at timing t6, the injection rate decreases, and as the injection rate decreases, the fuel pressure increases. Furthermore, at timing t7, the needle lift amount becomes zero, and the injection rate becomes zero. This completes one fuel injection. As the injection rate becomes zero, the fuel pressure becomes approximately constant.

During the above-mentioned one-time fuel injection, after fuel injection starts with the start of energization of the first stage and the injection rate reaches the maximum injection rate, until the injection rate starts to decrease with the end of energization of the second stage. During the period (period t2 to t6), the needle lift amount is maintained within the intermediate lift region Rf of Lmin to Lmax, and as a result, the injection rate is maintained at the maximum injection rate during the same period. Thereby, in the fuel injection device 11, it is possible to extend the injection period while maintaining the intermediate lift state of the nozzle needle 32, and it is possible to increase the amount of fuel injection to a desired amount.

As described above, when fuel injection is performed using multi-stage current, the fuel pressure changes in accordance with the needle lift, which corresponds to a change in the injection rate. In this case, the fuel injection state can be understood from the behavior of the drop in fuel pressure. For example, by acquiring the pressure change point P1 where the fuel pressure starts to drop, the slope Pa of the approximation line when the pressure drops, the pressure drop width ΔP, the pressure change point P2 where the fuel pressure starts to rise, and the slope Pb of the approximation line when the pressure rises as pressure parameters, it is possible to estimate the change in the injection rate, and thus to understand whether the fuel injection amount is excessive or insufficient. The ECU 20 performs an increase or decrease correction of the fuel injection amount based on the above pressure parameters.

Although not shown in the drawings, it is also possible to perform one fuel injection by energizing in three stages, front and rear, or in more stages. In this case, as described above, it is sufficient that the needle lift amount is maintained within the intermediate lift region Rf during energization at each stage, and as a result, fuel injection is continuously performed at the maximum injection rate.

By the way, when carrying out multi-stage energization in one injection opportunity as described above, if the lift operation of the nozzle needle 32 becomes abnormal due to a defect in each part of the fuel injection device 11, the fuel may be unintentionally released due to the occurrence of the abnormality. It may occur that the injection quantity is increased or decreased. For example, the following three abnormalities may occur in the fuel injection device 11.
(1) Abnormal sliding of the nozzle needle 32 (2) Abnormal expansion of the nozzle hole (3) Abnormal response of the control valve 62 In this embodiment, when any of the above abnormalities occurs, a multi-stage Appropriate measures will be taken regarding energization, and the types of abnormalities and their countermeasures will be explained in detail below. FIG. 4 is a time chart showing the fuel injection mode when a sliding abnormality of the nozzle needle 32 occurs, and FIG. 5 is a time chart showing the fuel injection mode when the nozzle hole enlargement abnormality occurs. , FIG. 6 is a time chart showing the manner of fuel injection when an abnormal response of the control valve 62 occurs. Each of these figures shows the difference from the behavior shown in Fig. 3, which is the behavior under normal conditions. The changes in injection rate and fuel pressure are shown by broken lines.

First, the abnormal sliding of the nozzle needle 32 (1) will be explained. When fuel deposits accumulate on the sliding parts 32a and 32b of the nozzle needle 32, this causes abnormal sliding of the nozzle needle 32, and the operating speed during lift-up and lift-down of the nozzle needle 32 becomes lower than normal. It is conceivable that this will also decrease.

In this case, as shown in FIG. 4, the operating speed of the nozzle needle 32 during lift-up is reduced, so that the slope when the injection rate rises from zero after the start of the first stage energization is slower than in the normal case. , and the slope of the decrease in fuel pressure becomes more gradual. In addition, due to the decrease in operating speed during lift-up, the needle lift amount at the end of the first stage energization (timing t3) becomes smaller than normal, and after the end of the energization, the injection rate becomes lower than the maximum injection rate. . That is, after the first stage energization ends, the needle lift amount falls below the lift lower limit Lmin, and the injection rate temporarily decreases. This decrease in injection rate causes a temporary increase in fuel pressure.

After the second stage energization starts, the needle lift amount at the end of energization becomes smaller than normal, as in the first stage energization, so that the needle lift amount falls below the lift lower limit Lmin at an earlier timing than normal after the end of energization. In addition, after the end of the second stage energization, the operating speed of the nozzle needle 32 during lift down is reduced, so the slope of the decrease in injection rate becomes gentler than normal, and the slope of the increase in fuel pressure also becomes gentler.

As described above, when a sliding abnormality occurs in the nozzle needle 32, the injection rate changes in a manner different from normal, and the fuel injection amount is unintentionally reduced.

The ECU 20 determines that a sliding abnormality has occurred in the nozzle needle 32 based on the presence or absence of a decrease in the injection rate after the end of the first stage energization. Specifically, the ECU 20 determines whether or not the injection rate has decreased after the first stage energization ends, based on the increase in fuel pressure during the energization suspension period after the first stage energization ends, If the injection rate has decreased, it is determined that a sliding abnormality of the nozzle needle 32 has occurred. The presence or absence of a decrease in the injection rate may be determined based on whether or not a pressure increase change greater than a predetermined value occurs when the fuel pressure is maintained at a substantially constant value after the start of the first stage energization. Further, the determination as to whether or not the injection rate has decreased may be determined using the differential value of the fuel pressure, based on the fact that the differential value of the fuel pressure has exceeded a predetermined value.

Furthermore, in the case of abnormal sliding of the nozzle needle 32, although the slope of the pressure change during the first-stage energization is smaller than in the normal case, the decrease width ΔP of the fuel pressure is approximately the same as in the normal case. Therefore, the injection rate decreases after the end of the first stage energization, that is, the fuel pressure increases during the energization period, and the pressure drop width ΔP (the decrease from the pressure before the start of energization) due to the first stage energization increases. It is preferable to determine that a sliding abnormality of the nozzle needle 32 has occurred based on the fact that it is substantially the same as the normal state.

Note that as a condition for determining that a sliding abnormality of the nozzle needle 32 has occurred, it may be added that the slope Pa of the approximate straight line when the pressure decreases in the fuel pressure waveform is smaller than when it is normal.

Next, the nozzle hole enlargement abnormality (2) will be explained. When the nozzle hole 33 expands due to fluid abrasive action caused by foreign matter in the fuel, the operating speed of the nozzle needle 32 decreases when lifting up and increases when lifting down compared to normal conditions. , an increase in the amount of fuel at the maximum injection rate may occur. The principle behind the decrease in the operating speed of the nozzle needle 32 when it is lifted up and the increase in its operating speed when it is lifted down will be explained. When the nozzle hole expands, the pressure inside the sac chamber 46 decreases after the nozzle needle 32 starts lifting up compared to before the nozzle hole expands (that is, under normal conditions). Therefore, the force on the nozzle needle 32 toward the lift-up side (valve-opening side) becomes small, and the operating speed of the nozzle needle 32 during lift-up is reduced. Furthermore, when the nozzle needle 32 is lifted down, the force applied to the nozzle needle 32 toward the lift-down side (valve closing side) increases due to the pressure drop in the sack chamber 46, so that the operating speed during the lift-down period increases.

In this case, as shown in FIG. 5, the operating speed of the nozzle needle 32 during lift-up is reduced, so that the slope of the injection rate as it rises from zero is gentler than normal, and the slope of the fuel pressure drop is also gentler. As in the case where there is a sliding abnormality in the nozzle needle 32, the needle lift amount at the end of the first stage of current application is smaller than normal due to the reduced operating speed during lift-up, and the injection rate drops below the maximum injection rate after the current application ends. This drop in injection rate causes a temporary rise in fuel pressure. However, when the nozzle hole is enlarged, the operating speed of the nozzle needle 32 during lift-down is higher than normal, so the degree of drop in the injection rate is greater than when there is a sliding abnormality in the nozzle needle 32.

In addition, by expanding the nozzle hole, the fuel flow rate (hole flow rate) passing through the nozzle hole 33 per unit time increases, and the maximum injection rate increases compared to normal. As a result, the fuel pressure at the maximum injection rate is lower than normal.

In Fig. 5, because the degree of decrease in the injection rate after the end of the first stage energization is large, the injection rate does not reach the maximum injection rate after the start of the second stage energization, and after the end of the second stage energization, the injection rate is normal. The injection rate drops to zero at an earlier timing.

As mentioned above, when an abnormality in the nozzle hole expansion occurs, the injection rate changes in a manner different from normal, and the amount of fuel injected is unintentionally reduced.

The ECU 20 is in a state where an abnormality in nozzle hole expansion has occurred based on the fact that the injection rate has decreased after the first stage energization and the maximum injection rate at the first stage energization is higher than normal. to judge. In this case, it may be determined that the injection rate has decreased based on an increase in the fuel pressure after the first stage energization ends. In addition, based on the fact that the pressure drop width ΔP during the first stage energization is larger than a predetermined threshold value, that is, the pressure drop width ΔP is larger than normal, the maximum injection rate during the first stage energization is normal. It is preferable to determine that it is larger than the time.

In addition, in both the (1) sliding abnormality of the nozzle needle 32 and the (2) nozzle hole expansion abnormality, the injection rate decreases after the first stage current application. Therefore, when the injection rate decreases, it is necessary to determine which of the above abnormalities (1) and (2) is the cause. In this regard, in this embodiment, based on the fact that the maximum injection rate at the time of the first stage current application is different in each of the above abnormalities (1) and (2), it is determined whether the injection rate decrease is caused by the above abnormality (1) or (2). Specifically, when the injection rate decreases after the first stage current application is completed, if the pressure drop width ΔP due to the first stage current application is approximately the same as that in the normal state, it is determined that the maximum injection rate does not increase due to the increase in the nozzle hole flow rate, and that a sliding abnormality of the nozzle needle 32 has occurred. In addition, if the pressure drop width ΔP due to the first stage current application is larger than that in the normal state, it is determined that the maximum injection rate increases due to the increase in the nozzle hole flow rate, and that a nozzle hole expansion abnormality has occurred.

Next, (3) abnormal response of the control valve 62 will be explained. When the responsiveness of the opening and closing operations of the control valve 62 to the energization pulse decreases, the lift operation of the nozzle needle 32 is delayed compared to normal times. Specifically, for example, if a sliding abnormality occurs in the control valve 62 due to accumulation of fuel deposits, the responsiveness of the opening and closing operations of the control valve 62 to the energization pulse decreases, and the pressure inside the pressure control chamber 37 decreases. There is a delay in the outflow and inflow of high pressure fuel. Therefore, the start timings of lift-up and lift-down of the nozzle needle 32 are delayed. Note that an electrical factor such as a decrease in the electromagnetic force of the solenoid coil 61 is also considered as a cause of the abnormal response of the control valve 62.

In this case, as shown in FIG. 6, the delay times Td1 to Td4 become longer than in normal times. As the delay time Td1 becomes longer and the start timing of lift-up is delayed, the timing at which the injection rate starts to rise is delayed after the start of energization of the first stage compared to the normal state, and the fuel pressure decreases due to the delay. The timing of the start of decline is delayed. In addition, as the delay time Td4 becomes longer and the lift-down start timing is delayed, the timing at which the injection rate starts to decrease after the second stage energization ends is delayed compared to the normal state, and due to this delay, the fuel The timing of the start of pressure rise is delayed. In other words, the lift operation of the nozzle needle 32 is delayed. However, the operating speed of the nozzle needle 32 during lift-up and lift-down is approximately the same as during normal operation. Furthermore, due to the delay in the lift operation of the nozzle needle 32, there is a shift in the injection period with respect to the energization period. In addition, when an abnormality in the response of the control valve 62 occurs, unlike other abnormalities (abnormalities (1) and (2)), the injection rate does not decrease after the first stage energization ends. ing.

The ECU 20 determines whether the response of the control valve 62 is abnormal based on the fact that the injection rate has not decreased after the end of the first stage energization and the lift operation of the nozzle needle 32 has been delayed. determine something. The fact that the lift operation of the nozzle needle 32 is delayed may be determined, for example, by the fact that the pressure change point P1 at which the fuel pressure starts to decrease in the fuel pressure waveform is delayed from the normal time. In addition, it can be seen that the delay in the lift operation of the nozzle needle 32 is caused by the pressure change point P1 where the fuel pressure begins to decrease in the fuel pressure waveform and the pressure change point P3 where the fuel pressure returns to the pressure before the pressure decrease. It is also possible to make a determination based on the fact that it is delayed compared to normal times. Note that as a condition for determining that the lift operation of the nozzle needle 32 is delayed, it may be added that the slope Pa of the approximate straight line when the pressure decreases is approximately the same as when it is normal.

The response by the ECU 20 when each of the above abnormalities (1) to (3) occurs will be explained. First, we will explain (1) what to do when a sliding abnormality occurs in the nozzle needle 32.

When the ECU 20 determines that the injection rate has decreased due to a sliding abnormality of the nozzle needle 32, it corrects the deviation in the fuel injection amount caused by the sliding abnormality. In this embodiment, when the injection rate has decreased due to a sliding abnormality of the nozzle needle 32, it is difficult to determine the injection amount equivalent to the decrease in the injection rate, so the current correction is performed twice, before and after.

In this case, in order to eliminate the drop in the injection rate after the end of the first stage current supply, the ECU 20 corrects and extends the current supply time of the first stage by shifting the start timing of the first stage current supply to the advance side, and performs multi-stage current supply using the corrected current supply time (first current supply correction). In addition, the ECU 20 corrects the current supply times of the second and subsequent stages in order to reduce the excessive increase in the fuel injection amount due to the extension of the first stage current supply time, and performs multi-stage current supply using the corrected current supply time (second current supply correction).

The two energization corrections before and after will be described in more detail with reference to FIGS. 7 and 8. FIG. 7 is a time chart showing the mode of the first energization correction. FIG. 8 is a time chart showing the mode of the second energization correction performed after the first energization correction. In each of these figures, the behavior after energization correction is shown by a broken line, and the normal behavior is shown by a solid line for comparison.

As shown in FIG. 7, in the first current correction, the current start timing of the first stage is shifted to the advance side to be timing t0, thereby advancing the needle lift start timing. Specifically, the ECU 20 extends the current time Tq1 of the first stage by advancing the current start timing of the first stage by a predetermined time. The current time of the first stage after the extension correction is "Tq11", and the first stage current is performed with the current time Tq11 and the second stage current is performed with the current time Tq2 unchanged. The interval time TINT is also unchanged. In this case, by shifting the current start timing of the first stage to the advance side, the needle lift amount is raised to the lift upper limit Lmax side even in a situation where the lift-up speed of the nozzle needle 32 is reduced, and the needle lift amount is prevented from falling below the lift lower limit Lmin after the end of the first stage current. This prevents the injection rate from decreasing after the end of the first stage current.

The predetermined time for advancing the first-stage energization start timing may be any time that can avoid a decrease in the injection rate after the first-stage energization ends, and may be, for example, the interval time TINT. Alternatively, it may be a predetermined time based on suitability or the like.

When the first-stage energization time Tq1 is extended and corrected, the decrease in the injection rate after the end of the first-stage energization is resolved, but the injection amount in the fuel injection by the second-stage energization becomes excessive. In the injection rate waveform of FIG. 7, the hatched portion corresponds to the excess amount of injection. Therefore, the excess injection amount is calculated based on the fuel pressure waveform, and based on the excess injection amount, the energization time for the second and subsequent stages is corrected, and multi-stage energization is performed using the corrected energization time.

In this case, the ECU 20 calculates the excess injection amount at the beginning of the fuel injection based on the pressure change point P1 where the fuel pressure starts to decrease in the fuel pressure waveform and the slope Pa of the approximate straight line when the pressure decreases, and also calculates the excess injection amount at the beginning of the fuel injection. The excess injection amount immediately before the end of fuel injection is calculated based on the pressure change point P2 at which the pressure starts to rise and the slope Pb of the approximate straight line when the pressure rises. More specifically, the ECU 20 determines the difference between the pressure change point P1 and the reference change point PX1, when the pressure change point due to the start of the first stage energization in normal conditions is the reference change point PX1, and the slope of the pressure drop is the reference slope PY1. , the excess injection amount at the beginning of fuel injection is calculated based on the difference between the slope Pa and the reference slope PY1. In addition, when the pressure change point at the end of the second stage energization during normal operation is the reference change point PX2, and the slope of the pressure increase is the reference slope PY2, the difference between the pressure change point P2 and the reference change point PX2, the slope Pb and the reference Based on the difference in slope PY2, the excess injection amount immediately before the end of fuel injection is calculated. However, the method of correcting the reduction of the excessive injection amount is arbitrary, and it is also possible to use parameters other than the change points P1 and P2 and the slopes Pa and Pb of the approximate straight line as pressure parameters.

Then, as the second energization correction, the ECU 20 performs a correction to shorten the second stage energization time Tq2 based on the excess injection amount at the beginning of the fuel injection and immediately before the end of the fuel injection.

As shown in FIG. 8, in the second energization correction, the second stage energization time Tq2 is shortened based on the excess injection amount. The second stage energization time after the shortening correction is "Tq21". In this case, multi-stage energization is performed using the first-stage energization time Tq11 that has been corrected to be extended, and the second-stage energization time Tq21 that has been shortened and corrected. Thereby, the fuel injection amount is adjusted to an appropriate amount.

Next, we will explain what to do when the nozzle hole enlargement abnormality (2) occurs.

When the nozzle hole enlargement abnormality occurs, the operating speed of the nozzle needle 32 during lift-down is higher than normal, and it is one step faster than when the nozzle needle 32 has a sliding abnormality. The degree of decrease in the injection rate after the end of energization of the eye becomes large. Therefore, even if the first stage energization time Tq1 is extended and corrected, as in the case of abnormal sliding of the nozzle needle 32, the decrease in the injection rate may not be resolved. Therefore, in this embodiment, when it is determined that the nozzle hole enlargement abnormality has occurred, multi-stage energization is prohibited.

Next, we will explain how to respond when an abnormality in the response of the control valve 62 occurs (3).

When the ECU 20 determines that the control valve 62 is in a state of responsiveness abnormality, it corrects the deviation in the injection period caused by the responsiveness abnormality. Specifically, when the pressure change point due to the start of first-stage current application under normal conditions is set as the reference change point PX1, the ECU 20 calculates the deviation in the injection period from the difference between the pressure change point P1 at which the fuel pressure begins to decrease in the fuel pressure waveform and the reference change point PX1. Then, the ECU 20 advances and corrects the periods of current application in the first and second stages based on the deviation in the injection period.

Figure 9 is a flowchart showing the procedure for determining an abnormality in the fuel injection device 11. This process is repeatedly performed at a predetermined interval by the microcomputer 21 of the ECU 20.

In step S11, it is determined whether or not multi-stage energization is being performed, and if multi-stage energization is being performed, the process proceeds to step S12. In step S12, it is determined whether or not a decrease in injection rate has occurred after the end of the first stage of energization based on the presence or absence of a change in fuel pressure after the end of the first stage of energization. Then, if a decrease in injection rate has occurred, the process proceeds to step S13, and if no decrease in injection rate has occurred, the process proceeds to step S16.

In step S13, it is determined whether or not a maximum injection rate change has occurred, in which the maximum injection rate at the time of the first stage current application changes to the increasing side, based on the pressure drop width ΔP at the time of the first stage current application. If a maximum injection rate change has not occurred, the process proceeds to step S14. In step S14, it is determined that a sliding abnormality has occurred in the nozzle needle 32, and the first abnormality flag F1 is set to 1. If a maximum injection rate change has occurred, the process proceeds to step S15. In step S15, it is determined that an injection hole expansion abnormality has occurred, and the second abnormality flag F2 is set to 1.

In step S16, it is determined whether or not there is a delay in the lift operation of the nozzle needle 32, based on the point of change in fuel pressure (pressure change point P1) after the start of energization in the first stage. If there is a delay in the lift operation of the nozzle needle 32, the process advances to step S17. In step S17, it is assumed that an abnormal response of the control valve 62 has occurred, and the third abnormality flag F3 is set to 1. If it is determined in steps S14, S15, and S17 that an abnormality has occurred, the user may be notified of the occurrence of the abnormality by, for example, turning on an abnormality warning light.

Note that if both steps S12 and S16 are negative, it is assumed that no abnormality has occurred in the fuel injection device 11, and this process is ended.

FIG. 10 is a flowchart showing a procedure for fuel injection control performed by energizing the fuel injection device 11, and this process is repeatedly performed by the microcomputer 21 of the ECU 20 at predetermined intervals.

In FIG. 10, in step S21, the required injection amount Qr and the required pressure (required rail pressure) are calculated based on engine operating conditions such as engine speed and load. In the subsequent step S22, the energization time Tr is calculated using a map that predetermines the relationship between the energization time Tr, the required injection amount Qr, and the required pressure.

Then, in step S23, it is determined whether the second abnormality flag F2 is 1, i.e., whether an injection hole expansion abnormality has occurred. In addition, in step S24, it is determined whether single-stage current conduction or multi-stage current conduction is performed depending on whether the required injection amount Qr is less than a predetermined threshold value Th1. Threshold value Th1 is a threshold value that switches whether the current fuel injection is performed in single-stage current conduction mode or in multi-stage current conduction mode with two or more stages.

If step S23 is negative and step S24 is positive, the process proceeds to step S25. If step S23 is positive, step S24 is skipped and the process proceeds to step S25. In step S25, it is determined that fuel injection will be performed in single-stage current mode this time. On the other hand, if both steps S23 and S24 are negative, the process proceeds to step S31. In step S31, it is determined that fuel injection will be performed in multi-stage current mode this time.

Here, when the second abnormality flag F2 is 0, it is determined whether to perform single-stage energization or multi-stage energization based on the required injection amount Qr. In contrast, when the second abnormality flag F2 is 1, it is determined that single-stage energization will be performed regardless of the required injection amount Qr. In other words, when the second abnormality flag F2 is 1, the implementation of multi-stage injection is prohibited.

When fuel injection is performed in the single-stage current mode, in step S26, a single-stage current pulse is generated based on the current time Tr calculated in step S22, and in the following step S27, the current pulse is output. In this case, a single-stage current pulse is output from the microcomputer 21 to the drive circuit 22, and the drive circuit 22 turns on and off the fuel injection device 11 according to the rising and falling timing of the current pulse.

When fuel injection is performed in the multi-stage energization mode, in step S32, the number of stages of the multi-stage energization is determined according to the required injection amount Qr. At this time, one or more thresholds greater than the above-mentioned threshold Th1 are set, and the number of stages of the multi-stage energization is determined according to the results of comparing the required injection amount Qr with each threshold. For example, in addition to threshold Th1, thresholds Th2 and Th3 are set (Th1<Th2<Th3), and if the required injection amount Qr is within the range of Th1 to Th2, the two-stage energization mode is selected; if the required injection amount Qr is within the range of Th2 to Th3, the three-stage energization mode is selected; and if the required injection amount Qr is equal to or greater than Th3, the four-stage energization mode is selected. Note that the number of stages of the multi-stage energization may be four or more.

Each of the threshold values Th1 to Th3 is the respective maximum injection amount when fuel injection is performed in the energization mode of each stage. That is, when the required injection amount Qr is equal to or greater than the threshold value Th1, it is assumed that the required injection amount Qr exceeds the maximum injection amount in the one-stage energization mode, and the two-stage or more stage energization mode is set. Further, when the required injection amount Qr is equal to or greater than the threshold value Th2, it is assumed that the required injection amount Qr exceeds the maximum injection amount in the two-stage energization mode, and the energization mode is set to three or more stages.

Then, in step S33, the current conduction time Tq and interval time TINT for each stage in the multi-stage current conduction are set based on the current conduction time Tr calculated in step S22. In the two-stage current conduction mode, two current conduction times Tq1, Tq2 and one interval time TINT are set. In the three-stage current conduction mode, three current conduction times Tq1, Tq2, Tq3 and two interval times TINT1, TINT2 are set. The same applies to the four or more stage current conduction mode.

Thereafter, in step S34, it is determined whether the first abnormality flag F1 is 1, that is, whether or not a sliding abnormality of the nozzle needle 32 has occurred. If the first abnormality flag F1 is 1, the first energization correction is performed to extend the first stage energization time Tq1, and the first energization correction is performed to reduce the excessive increase in the fuel injection amount due to the extension of the first stage energization time. A second energization correction is performed to shorten the energization time in the second and subsequent stages.

Specifically, if the first abnormality flag F1 is 1, the process proceeds to step S35, and it is determined whether or not the first energization correction has not yet been performed. If the first energization correction has not yet been performed, the process advances to step S36, and a first-stage energization time extension correction is performed. Furthermore, if the first energization correction has been performed, the process proceeds to step S37, and correction for shortening the energization time in the second and subsequent stages is performed. Note that when three-stage energization is performed as multi-stage energization, the energization time of the third stage (the energization time of the final stage) may be shortened and corrected.

If the first abnormality flag F1 is 0, the process proceeds to step S38, where it is determined whether the third abnormality flag F3 is 1, i.e., whether an abnormality in the response of the control valve 62 has occurred. If the second abnormality flag F2 is 1, the process proceeds to step S39. In step S39, a correction is made to the deviation in the injection period caused by the abnormality in the response of the control valve 62.

If the first abnormality flag F1 and the second abnormality flag F2 are both 0, steps S34 and S38 are negative and the process proceeds directly to step S40.

In step S40, a plurality of energization pulses are generated depending on the current energization mode. At this time, energization pulses for the number of stages are generated based on the energization time and interval time of each stage. Thereafter, in step S41, the energizing pulse is output. In this case, the microcomputer 21 outputs energization pulses for each stage to the drive circuit 22, and in the drive circuit 22, the fuel injection device 11 is energized and energized according to the rise timing and fall timing of the energization pulse to each stage. A cutoff is performed.

The present embodiment described above provides the following excellent effects:

When performing multi-stage energization, if an abnormality occurs in the sliding of the nozzle needle 32, the operating speed (lift speed) of the nozzle needle 32 when it is lifted up and down decreases, and this decrease in lift speed causes a decrease in the injection rate after the end of the first stage of energization. When this decrease in injection rate occurs, it is necessary to increase the injection amount by an amount equivalent to the decrease in injection rate, but it is difficult to determine the decrease in injection amount at the intermediate stages.

In this respect, in the present embodiment, when a drop in the injection rate occurs due to a drop in the lift speed of the nozzle needle 32, the current conduction time of the first stage is extended and corrected by shifting the start timing of the current conduction of the first stage to the advance side while maintaining the current conduction time of the second stage and the interval time between the current conduction times of each stage, and multi-stage current is performed using the corrected current conduction time. As a result, even in a situation where the lift speed of the nozzle needle 32 has decreased, a drop in the injection rate after the end of the current conduction of the first stage is suppressed. In addition, when the current conduction time of the first stage is extended and corrected, the injection amount in the fuel injection by the multi-stage current is excessive, but the current conduction time of the second stage and subsequent stages is corrected based on the excessive injection amount, and multi-stage current is performed using the corrected current conduction time. This makes it possible to inject an appropriate amount of fuel. As a result, fuel injection control can be performed appropriately when multi-stage current is performed during one injection opportunity.

The injection rate is highly correlated with the fuel pressure, and if an abnormality in the fuel injection device 11 causes a decrease in the injection rate, the fuel pressure increases accordingly. Therefore, it is possible to determine whether or not the injection rate has decreased based on the fuel pressure.

The drop in injection rate after the end of the first stage of current application occurs when there is a sliding abnormality in the nozzle needle 32 and when there is an abnormality in the nozzle hole expansion. However, when there is a sliding abnormality in the nozzle needle 32, the degree of injection rate drop at the intermediate point is relatively small, so it is possible to address this with the first current application correction, whereas when there is an abnormality in the nozzle hole expansion, the degree of injection rate drop at the intermediate point is relatively large, so it is considered difficult to address this with the first current application correction.

In this regard, if a decrease in the injection rate occurs after the end of the first stage current application, and it is determined that no change in the maximum injection rate occurs, in which the maximum injection rate at the time of the first stage current application changes to an increasing side, the current application time Tq1 of the first stage is extended and multi-stage current application is performed. This makes it possible to properly determine that the decrease in the injection rate after the end of the first stage current application is not due to an abnormality in the expansion of the injection hole, but due to an abnormality in the sliding of the nozzle needle 32, and makes it possible to properly perform fuel injection corrections, including the first current application correction.

In the fuel injection device 11, when the nozzle hole flow rate increases compared to the normal state due to the nozzle hole enlargement abnormality, the injection rate decreases after the first stage energization ends. In this situation, the operating speed of the nozzle needle 32 during lift-down is higher than normal, and the degree of decrease in the injection rate at the intermediate point is lower than when the nozzle needle 32 has a sliding abnormality. growing. Therefore, as in the case of abnormal sliding of the nozzle needle 32, it is conceivable that the decrease in the injection rate will not be resolved even if the first energization correction is performed to extend the first stage energization time. In this regard, since multi-stage energization is prohibited, it is possible to avoid a decrease in the injection rate after the first stage energization.

In the fuel injection device 11, when an abnormality in the response of the control valve 62 occurs, the lift operation of the nozzle needle 32 in response to the current pulse is delayed compared to normal, and this delay causes a shift in the injection period. In this regard, if it is determined that there is no decrease in the injection rate after the end of the first stage of current flow and a delay in the lift operation of the nozzle needle 32 has occurred, the shift in the injection period caused by the delay in the lift operation is corrected. This makes it possible to suppress the shift in the injection period caused by the abnormality in the response of the control valve 62, and to perform fuel injection at the appropriate timing.

When fuel injection is performed by the fuel injection device 11, the number of energizations per injection opportunity is determined, and the energization time Tq and interval time TINT for each stage are set so that fuel injection at the maximum injection rate in the intermediate lift state is performed during the injection period in which the energization is performed, and the energization of each stage is performed based on the energization time Tq and interval time TINT for each stage. In this case, by repeatedly increasing and decreasing the needle lift amount by multiple divided energizations for one fuel injection, the nozzle needle 32 can be maintained in the desired intermediate lift state without expanding the intermediate lift region Rf of the fuel injection device 11. In addition, injection at the maximum injection rate can be continuously performed during the energization period of each stage, and the fuel injection amount can be made linear, allowing for highly accurate fuel injection.

When energizing each stage, the drive circuit 22 applies a high voltage and a low voltage, respectively. This makes it possible to suppress the response delay of the nozzle needle 32 when the nozzle needle 32 changes from lift-down to lift-up at the start of energizing the second stage or later. Therefore, it is possible to realize a configuration that is suitable for improving the linearity of the injection volume response to the energizing time.

Other Embodiments
The above embodiment may be modified, for example, as follows.

- In the case where the nozzle needle 32 has a sliding abnormality, after performing multi-stage energization with the energization time corrected by the first energization correction, it is determined whether the injection rate decrease has been eliminated, and if the injection rate decrease has not been eliminated, that is, if it is determined again that the injection rate decrease has occurred, the first-stage energization time may be extended again. Figure 11 is a time chart specifically showing the manner in which the energization time is extended again. In this case, if the injection rate decrease occurs after the end of the first-stage energization, the first-stage energization time Tq1 shown in Figure 11(a) is corrected to the energization time shown in Figure 11(b). In addition, if it is determined again that the injection rate decrease has occurred after performing multi-stage energization with the corrected energization time, the energization time shown in Figure 11(b) is extended again to the energization time shown in Figure 11(c). This re-extension may be repeated until the injection rate decrease no longer occurs. This allows the first-stage energization time to be appropriately extended in the first energization correction.

- In the first current correction when a sliding abnormality occurs in the nozzle needle 32, the correction time for extending the current time of the first stage may be set based on the degree of decrease in the operating speed of the nozzle needle 32. In this case, the degree of decrease in the operating speed of the nozzle needle 32 is estimated from the slope of the decrease in fuel pressure when the nozzle needle 32 is lifted up (slope Pa in FIG. 4), and it is estimated that the smaller the slope of the decrease in fuel pressure, the greater the decrease in the operating speed of the nozzle needle 32. Then, using the relationship shown in FIG. 12, the smaller the slope of the decrease in fuel pressure, i.e., the greater the degree of decrease in the operating speed of the nozzle needle 32, the longer the correction time may be set.

The degree of decrease in the operating speed of the nozzle needle 32 varies depending on the degree of the sliding abnormality of the nozzle needle 32 that is the cause of the decrease in operating speed, and it is considered that the greater the degree of the sliding abnormality of the nozzle needle 32, the greater the degree of decrease in operating speed. Since a correction time that extends the first stage current application time is set according to the degree of decrease in the operating speed of the nozzle needle 32, the first stage correction time can be set appropriately according to the degree of the sliding abnormality of the nozzle needle 32.

- In the above embodiment, in order to suppress a drop in the injection rate after the end of the first stage injection when a sliding abnormality occurs in the nozzle needle 32, the first current flow correction is configured to extend the current flow time of the first stage by shifting the current flow start timing of the first stage to the advance side, but this may be changed. For example, the first current flow correction is configured to extend the current flow time of the first stage by shifting the current flow end timing of the first stage to the retard side while maintaining the current flow time of the second stage and subsequent stages and the interval time between the current flow times of each stage. In short, the first current flow correction may be configured to extend the current flow time of the first stage while maintaining the current flow time of the second stage and subsequent stages and the interval time between the current flow times of each stage.

- In the embodiment described above, it is determined which of the three abnormalities corresponds to the sliding abnormality of the nozzle needle 32, the nozzle hole enlargement abnormality, and the responsiveness abnormality of the control valve 62, and appropriate actions are taken according to the determined abnormality. We are currently working on this, but you may change this. For example, only any two of the above-mentioned three abnormalities may be determined, and appropriate measures may be taken depending on the determined abnormalities. Alternatively, only the sliding abnormality of the nozzle needle 32 may be determined, and countermeasures may be taken against the abnormality.

- In addition to the sliding abnormality of the nozzle needle 32, the nozzle hole enlargement abnormality, and the response abnormality of the control valve 62, a nozzle hole contraction abnormality may be determined. The nozzle hole shrinkage abnormality occurs due to accumulation of fuel deposits in the nozzle hole 33 and the like. In this case, as a response to the nozzle hole contraction abnormality, it is preferable to prohibit implementation of multi-stage energization, as in the case of the nozzle hole enlargement abnormality. The case of nozzle hole contraction abnormality will be explained using FIG. 13.

As shown in FIG. 13, when an abnormality in the nozzle hole reduction occurs, the operating speed of the nozzle needle 32 increases when lifting up and decreases when lifting down, and the maximum injection rate decreases, compared to normal times. The principle behind the increase in operating speed of the nozzle needle 32 when lifting up and the decrease in operating speed when lifting down is as follows. That is, when the nozzle hole reduction occurs, the pressure in the sack chamber 46 becomes greater than before the nozzle hole reduction (i.e., normal times). Therefore, the force on the lift-up side (valve opening side) of the nozzle needle 32 increases, and the operating speed of the nozzle needle 32 when lifting up increases. Also, when the nozzle needle 32 is lifted down, the force on the lift-down side (valve closing side) of the nozzle needle 32 decreases due to the increase in pressure in the sack chamber 46, and therefore the operating speed when lifting down decreases.

As the operating speed of the nozzle needle 32 increases during lift-up, the slope of the decrease in fuel pressure becomes steeper than in normal times. In addition, in the case of the nozzle hole contraction abnormality, the nozzle needle 32 reaches the lift upper limit Lmax when the first stage energization is performed, so that the injection rate does not decrease after the first stage energization is completed. Further, due to the reduction of the nozzle hole, the fuel flow rate per unit time passing through the nozzle hole 33 (nozzle hole flow rate) decreases, and the maximum injection rate decreases. Therefore, the fuel pressure at the maximum injection rate increases compared to normal. In addition, after the second stage energization is completed, the operation speed during lift-down of the nozzle needle 32 decreases, so the needle lift amount falls below the lift lower limit Lmin at a timing later than normal, and injection is performed at a timing later than normal. rate drops to zero. As described above, when the nozzle hole contraction abnormality occurs, the injection rate changes in a manner different from normal, and the fuel injection amount is increased unintentionally.

The ECU 20 determines whether the nozzle hole contraction abnormality has occurred based on the fact that the injection rate has not decreased after the first stage energization and the maximum injection rate at the first stage energization is smaller than normal. determine something. In this case, based on the fact that the pressure drop width ΔP during the first stage energization is smaller than a predetermined threshold value, that is, the pressure drop width ΔP is smaller than normal, the maximum injection rate during the first stage energization is determined. It is preferable to determine that the value is smaller than normal. If it is determined that a nozzle hole contraction abnormality has occurred, multi-stage energization may be prohibited.

- In the above embodiment, the configuration is such that the energization pulse corresponding to the required injection amount Qr is divided into a plurality of parts as a configuration for performing multi-stage energization in one injection opportunity, but this may be changed. The energization pulse itself may be one pulse without being divided into a plurality of pulses, and a energization suspension period corresponding to the interval time TINT may be provided within the one pulse.

- The control unit and the method described in the present disclosure are implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. May be realized. Alternatively, the controller and techniques described in this disclosure may be implemented by a dedicated computer provided by a processor configured with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be implemented using a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. It may be implemented by one or more dedicated computers configured. The computer program may also be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

DESCRIPTION OF SYMBOLS 11... Fuel injection device, 32... Nozzle needle, 33... Nozzle hole, 60... Electric actuator, 20... ECU

Claims (8)

It has a drive part (60) that is driven by energization, and a valve body (32) that opens the nozzle hole (33) according to the drive of the drive part, and controls the injection amount according to the energization time of the drive part. applied to a fuel injection system comprising a fuel injection device (11) that realizes a maximum injection rate by changing the valve body and achieving an intermediate lift state in which the lift amount of the valve body becomes a predetermined intermediate lift amount;
The drive unit is energized multiple times intermittently during one injection occasion, and the fuel injection device is configured to inject fuel at the maximum injection rate in the intermediate lift state through each energization before and after the energization. A fuel injection control device that performs injection,
an abnormality determination unit that determines that an injection rate decrease has occurred after the first stage of energization is completed when multi-stage energization is performed in at least two stages for one injection opportunity;
When the abnormality determination unit determines that a decrease in the injection rate has occurred, the energization time of the first stage is extended and corrected while maintaining the energization time of the second and subsequent stages and the interval time between the energization times of each stage. , a first energization control unit that performs the multi-stage energization according to the corrected energization time;
an excessive amount calculation unit that calculates an excessive injection amount in the multi-stage energization in a state where the first energization control unit performs the multi-stage energization;
a second energization control unit that corrects the energization time in the second and subsequent stages based on the excessive injection amount and performs the multi-stage energization according to the corrected energization time;
A fuel injection control device (20) for an internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 1, wherein the first current control unit, when it is determined by the abnormality determination unit that a drop in the injection rate has occurred, corrects the current duration of the first stage by shifting the start timing of the current to the advance side. The fuel injection device has a pressure detection unit (45) that detects the pressure of the fuel injected from the injection hole,
3. The fuel injection control device for an internal combustion engine according to claim 1, wherein the abnormality determination unit acquires the fuel pressure detected by the pressure detection unit as an abnormality determination parameter, and determines whether or not the injection rate has decreased based on the fuel pressure. In the case of performing the multi-stage energization, the abnormality determination unit determines whether a maximum injection rate change in which the maximum injection rate at the time of the first stage energization changes toward an increasing side has occurred;
The first energization control section corrects the multi-stage energization by extending the first stage energization time when the abnormality determination section determines that the injection rate has decreased and the maximum injection rate has not changed. A fuel injection control device for an internal combustion engine according to any one of claims 1 to 3, which is implemented. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4, wherein, when the abnormality determination unit determines that a drop in the injection rate has occurred, the first current control unit extends and corrects the first-stage current time by a predetermined time and performs the multi-stage current, and if the abnormality determination unit again determines that a drop in the injection rate has occurred, the first current control unit again extends the first-stage current time. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4, wherein the first current control unit sets a correction time for extending the current time of the first stage based on the degree of decrease in the operating speed of the valve body when the abnormality determination unit determines that a decrease in the injection rate has occurred. In the case of performing the multi-stage energization, the abnormality determination unit determines whether a maximum injection rate change occurs in which the maximum injection rate at the time of the first stage energization changes to an increasing side or a decreasing side,
The internal combustion engine according to any one of claims 1 to 6, further comprising a multistage energization prohibition unit that prohibits implementation of the multistage energization when the abnormality determination unit determines that the maximum injection rate change has occurred. fuel injection control device. In the case of performing the multi-stage energization, the abnormality determination unit determines that a delay in the lift operation of the valve body has occurred with respect to each timing of starting and ending energization to the drive unit,
Injection for correcting the deviation in the injection period due to the delay in the lift operation of the valve body when the abnormality determination unit determines that a decrease in the injection rate has not occurred and a delay in the lift operation of the valve body has occurred. The fuel injection control device for an internal combustion engine according to claim 1, further comprising a period deviation correction section.

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