WO2016203651A1

WO2016203651A1 - Fuel injection control device and fuel injection control method

Info

Publication number: WO2016203651A1
Application number: PCT/JP2015/067777
Authority: WO
Inventors: 将天内; 孝嗣片山
Original assignee: 日産自動車株式会社
Priority date: 2015-06-19
Filing date: 2015-06-19
Publication date: 2016-12-22

Abstract

The present invention is a direct-injection gasoline internal combustion engine wherein fuel is injected into a combustion chamber using a fuel injector which opens a valve by supplying an electrical current corresponding to an injection pulse width signal. A controller determines, from the operating condition of the engine, whether or not the injection timing of the fuel injector is going to enter a knock-detection area. If the controller determines that the injection timing is going to enter the knock-detection area, the injection timing is prevented from entering the knock-detection area by increasing the peak current which is supplied to the fuel injector to open the valve.

Description

Fuel injection control device and fuel injection control method

This invention relates to fuel injection control of a direct injection gasoline internal combustion engine.

In a direct-injection gasoline internal combustion engine in which fuel is injected by a fuel injector using a solenoid and a spring, an excitation current is supplied to the solenoid with a time width equal to the injection pulse width signal output from the controller, and the solenoid is valved against the spring. Fuel injection is performed by lifting the body. The fuel injection amount is basically proportional to the injection pulse width.

The excitation current supplied by the injection pulse width signal is not constant. In order to lift the valve body of the fuel injector, a large current is supplied to the solenoid at the beginning of the injection pulse width signal, and then the valve is switched to the valve opening position maintaining current for holding the valve body in the lift position. The valve opening position maintaining current is maintained until the end of the signal.

Since the valve element lifted by the initial large current of the injection pulse width signal collides with the stopper and bounces, it is impossible to finely control the lift of the valve element at the initial stage of the injection pulse width signal. Therefore, for example, in an injection pulse width region of 1 millisecond or less where the lift position of the valve body is not stable, in other words, in a small amount of fuel injection region, the injection pulse width and the fuel injection amount do not correspond linearly, and the fuel injection amount It was difficult to control.

In this regard, JP2012-052419A issued by the Japan Patent Office in 2012 outputs a current corresponding to the injection pulse width signal so that a fuel injection amount corresponding to the injection pulse width can be obtained even in a small amount of fuel injection region. Propose to change the waveform. Specifically, the peak of the large current supplied to the solenoid in the initial stage is suppressed to a low level, and the current after output of the large current is once reduced to a value lower than the valve opening position maintaining current, and then the valve opening position maintaining current is To.

According to this prior art, the bounce of the valve body lifted from the supply of a large current can be suppressed small, and a linear relationship between the injection pulse width and the actual fuel injection amount can be obtained even in a small amount of fuel injection region. As a result, the controllable region of the fuel injection amount can be expanded to the small amount side.

According to this conventional technique, the control accuracy in a small amount of fuel injection region is improved, but the opening area of the fuel injector at the initial stage of the injection pulse width signal becomes relatively small. As a result, the actual fuel injection amount with respect to the injection pulse width becomes relatively small.

This means that the injection pulse width becomes longer than the required fuel injection amount. When the injection pulse width becomes longer, it is inevitable that the injection start timing is advanced or the injection end timing is delayed.

A direct injection gasoline internal combustion engine is generally provided with a knock sensor for detecting knock. The knock sensor detects a knock in a certain angular region centered on the compression top dead center of the combustion cycle. If the fuel injector is opened or closed in this knock detection region, the knock sensor may erroneously detect knock.

Therefore, when the conventional technology is applied to a direct injection gasoline internal combustion engine, although the control accuracy for a small amount of fuel injection is improved, there is a possibility that it may adversely affect the knock detection accuracy.

Therefore, an object of the present invention is to increase the control accuracy for a small amount of fuel injection while maintaining the knock detection accuracy.

In order to achieve the above object, a fuel injection control device according to the present invention performs fuel injection into a combustion chamber using a fuel injector that opens by supplying current in accordance with an injection pulse width signal, and has a predetermined crank angle region. The present invention is applied to a direct-injection gasoline internal combustion engine having a knock sensor for detecting knocking of the engine. The fuel injection control device includes a sensor that detects an operating condition of the engine and a programmable controller. The controller determines whether the injection timing of the fuel injector interferes with a predetermined crank angle region from the engine operating conditions. If the injection timing interferes with the predetermined crank angle region, the injection timing is It is programmed to increase the peak current supplied to the fuel injector rather than not interfering with the corner region.

DETAILED DESCRIPTION Details and other features and advantages of the present invention are described in the following description of the specification and shown in the accompanying drawings.

FIG. 1 is a schematic configuration diagram of a fuel injection control device for a direct injection gasoline internal combustion engine according to the present invention. FIG. 2 is a diagram illustrating a full lift mode and a partial lift mode applied by the fuel injection control device. FIG. 3 is a diagram for explaining the change in the lift amount of the valve body in the full lift mode and the partial lift mode. FIG. 4 is a flowchart illustrating a fuel injection control routine executed by a controller provided in the fuel injection control device. FIG. 5 is FIG. 4 shows a second embodiment related to the fuel injection control routine, but similar to FIG. FIG. 6 is FIG. 4 shows a third embodiment related to a fuel injection control routine. FIG. 7 is a flowchart for explaining a fuel increase subroutine executed by the controller in the fuel injection control routine of the third embodiment. FIG. 8 is a diagram showing the relationship between the air-fuel ratio of the internal combustion engine and the generated torque. FIG. 9A-9E is shown in FIG. 6 is a timing chart showing an execution result of a fuel injection control routine of No. 4; FIG. 10A-10E is shown in FIG. 6 is a timing chart showing an execution result of a fuel injection control routine of No. 5; FIG. 11A-11F is shown in FIG. 6 is a timing chart showing execution results of a fuel injection control routine of FIG.

Fig. Of drawing. Referring to FIG. 1, a fuel injection control device according to an embodiment of the present invention is applied to fuel injection control of an internal combustion engine 1 for a vehicle.

The internal combustion engine 1 is composed of a 4-cylinder direct injection gasoline internal combustion engine. Air is taken into each cylinder of the internal combustion engine 1 from the intake passage 2 through the throttle 3, the collector 4, and the intake manifold 5. The internal combustion engine 1 includes a fuel injector 6 that directly injects fuel into the combustion chamber of each cylinder, and a spark plug 7 that performs spark ignition on a mixture of air and fuel generated in the combustion chamber.

The spark-ignition mixture burns and rotates the internal combustion engine 1 with combustion energy. The combustion gas is discharged from the combustion chamber through the exhaust manifold 8, the catalytic converter 9, and the exhaust pipe 10 into the atmosphere.

The internal combustion engine 1 is composed of a 4-stroke cycle engine in which each cylinder burns once every two revolutions. Intake into the combustion chamber is performed through an intake valve 13, and exhaust of combustion gas from the combustion chamber is performed through an exhaust valve 14.

The internal combustion engine 1 is based on single-stage injection, and performs multi-stage injection for each cylinder according to operating conditions.

The fuel injection of the fuel injector 6 is controlled by the controller 20. It is also possible to control the throttle 3, the intake valve 13, the exhaust valve 14, and the spark plug 7 by the same controller 20.

The controller 20 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the controller with a plurality of microcomputers.

The controller 20 controls the fuel injection amount and injection timing of the fuel injector 6. Therefore, as a sensor for detecting the operating condition of the internal combustion engine 1, a crank angle sensor 21 for detecting the crank angle and the rotation speed of the internal combustion engine 1 and an air flow meter 22 for detecting the load of the internal combustion engine 1 are provided in the controller 20. Connected by signal circuit. Further, a knock sensor 23 for detecting knock of the internal combustion engine 1 is also connected to the controller 20 by a signal circuit.

The controller 20 sets the injection pulse width and injection timing of the fuel injector 6 based on the engine load of the internal combustion engine 1. Then, the set injection pulse width and injection timing are output to the fuel injector 6 as an injection pulse width signal.

The fuel injector 6 is composed of, for example, a known fuel injector disclosed in the prior art, a valve body held in a closed position by a spring, a solenoid that lifts the valve body against the spring, and a certain level of the valve body And a stopper for preventing the lift.

The fuel injection control performed by the controller 20 will be described in more detail below.

The injection pulse width signal is generally represented as a rectangular signal, but the current supplied to the solenoid of the fuel injector 6 by the injection pulse width signal is actually different between the initial stage of the injection pulse width signal and the others. This is because the solenoid excitation current required to start the valve body to lift against the initial load and inertial force of the spring, and the solenoid excitation current required to hold the lifted valve body in the lifted state. Is different. In the following description, the former is referred to as a peak current, and the latter is referred to as a valve opening position maintaining current. Since the peak current is a large current, the valve body that has started to lift once suddenly lifts up and collides with the stopper.

FIG. Referring to FIG. 2, when the peak current is high in the injection pulse width signal having the same width, the solenoid drive current changes as indicated by a one-dot chain line in the figure. In the following description, this drive waveform of the injection pulse width signal is referred to as a full lift mode drive waveform. The peak current in the full lift mode is referred to as the first peak current.

On the other hand, the solid line in the figure shows that the peak current is suppressed to the second peak current lower than the first peak current in the full lift mode, and the current immediately exceeds the valve opening position maintaining current immediately after the second peak current is output. It shows a case of lowering and then returning to the valve opening position maintaining current. In the following description, this drive waveform of the injection pulse width signal is referred to as a partial lift mode drive waveform. The partial lift mode corresponds to the current control of the injection pulse width signal proposed by the prior art.

The internal combustion engine 1 is an engine that operates in the partial lift mode under at least certain conditions. Regarding the proper use of the full lift mode and the partial lift mode, for example, the full lift mode may be applied when the acceleration response is more important than the fuel efficiency of the internal combustion engine 1, and the partial lift mode may be applied otherwise. It is done. However, this fuel injection control device is also applicable to the internal combustion engine 1 designed to always operate in the partial lift mode in principle.

FIG. Referring to FIG. 3, in the full lift mode, the lift amount of the valve body varies as the valve body of the fuel injector 6 collides with the stopper. Therefore, it is difficult to control the fuel injection amount at the initial stage of the injection pulse width signal where the lift position is not stable. On the other hand, in the partial lift mode, the valve body lifts smoothly, so the fuel injection amount changes stably from the initial stage of the injection pulse width signal.

FIG. 3, the area of the drive waveform in each mode corresponds to the fuel injection amount. As can be seen from the figure, the injection amount in the partial lift mode is lower than the injection amount in the full lift mode with respect to the injection pulse width signal having the same width.

In the partial lift mode, the fuel injection amount can be accurately controlled from the initial stage of the output of the injection pulse width signal. Therefore, there is an advantage that highly accurate fuel injection control can be performed. On the other hand, the injection amount can be kept low with respect to the pulse width. Therefore, even if the required injection amount is the same, the pulse width must be set longer than the full lift mode. When the pulse width of the injection pulse width signal becomes longer, the fuel injection timing enters a knock detection region that is a crank angle region where the knock sensor 23 detects knock. That is, while fuel injection is performed in the intake stroke of a certain cylinder, knock detection is performed in a specific crank angle region (for example, a specific crank angle region after compression top dead center) in another cylinder, If the pulse width of the injection pulse width signal becomes longer, the fuel injection timing may enter this crank angle region. In particular, when performing multi-stage injection, the pulse width of the injection pulse width signal of each injection stage becomes longer, so the possibility becomes higher. Here, the fuel injection timing means the timing of lift of the valve body of the fuel injector 6 or seating on the seat. If these operations of the valve body are performed in the knock detection region, the knock sensor 23 may erroneously recognize that knocking has occurred. Therefore, it is desirable to start fuel injection of the internal combustion engine 1 after the end of the knock detection region, or end it before the start of the knock detection region.

However, for the same injection pulse width signal, the actual injection amount is smaller in the partial lift mode than in the full lift mode as described above. Therefore, the pulse width of the injection pulse width signal set for the same required injection amount is longer than that in the full lift mode. As a result, in the partial lift mode, the fuel injection timing tends to enter the knock detection region. In other words, the fuel injection timing tends to interfere with the knock detection region.

The fuel injection control device calculates an injection timing and an injection amount of fuel injection based on a rotational speed and a load representing an operation condition of the internal combustion engine 1, and outputs an injection pulse width signal corresponding to the calculated injection timing and injection amount to the fuel injector. Output to. Prior to the output of the injection pulse width signal, the controller 20 determines whether or not the determined fuel injection timing interferes with a predetermined crank angle region that is a knock detection region of the knock sensor. When the fuel injection timing interferes with a predetermined crank angle region, the controller 20 switches the fuel injection mode from the partial lift mode to the full lift mode, and the injection pulse width signal reset under the full lift mode is supplied to the fuel injector 6. Output.

In order to realize this control, the ROM of the controller 20 has a FIG. A fuel injection control routine shown in FIG. The controller 20 implements this control by executing a fuel injection control routine.

FIG. The fuel injection control routine will be described with reference to FIG. The controller 20 repeatedly executes the fuel injection control routine in synchronization with, for example, the rotation of the internal combustion engine. This routine corresponds to the first embodiment of the present invention relating to the fuel injection control routine.

In step S1, the controller 20 reads the engine rotational speed input from the crank angle sensor 21 and the intake air amount input from the air flow meter 22. The intake air amount is read as a value representative of the engine load.

In step S2, the controller 20 calculates the fuel injection amount based on the engine load.

In the next step S3, the controller 20 calculates a crank angle region in which the knock sensor 23 detects knocking of the internal combustion engine 1 based on the engine speed. In the following description, the crank angle region where the knock sensor 23 detects knocking of the internal combustion engine 1 is referred to as a knock detection region. Generally, as the engine speed increases, the knock detection area expands toward the advance side.

In the next step S4, the controller 20 calculates the fuel injection pulse width and injection timing in the partial lift mode from the fuel injection amount determined in step S2. Here, the injection timing means an injection start timing and an injection end timing. The injection end timing is a value obtained by adding the injection pulse width to the injection start timing. Note that the injection end timing may be calculated first, and the injection start timing may be calculated by subtracting the injection pulse width from the injection end timing. When performing multistage injection, the controller 20 calculates the injection start timing and the injection end timing for each injection stage of the multistage injection executed within one combustion cycle.

In the next step S5, the controller 20 determines whether any of the injection start timing and the injection end timing calculated in step S4 interferes with the knock detection region set in step S3. Here, the interference means that the injection start timing or the injection end timing enters the knock detection region. In the case of multi-stage injection, the injection start timing of the first injection stage is the most advanced position among the injection start timing and injection end timing of each injection stage, and the final injection stage is the most retarded position. Is the end timing of injection. Therefore, in step S5, it may be determined whether the injection start timing of the first injection stage and the injection end timing of the final injection stage are within the knock detection region. In general, the determination in step S5 is negative, that is, one of the injection start timing and the injection end timing interferes with the knock detection region is a region where the engine speed of the internal combustion engine 1 is high or the engine load is high. It is.

If both the injection start timing and the injection end timing are outside the knock detection region in step S5, the controller 20 determines in FIG. S7 according to the fuel injection pulse width and injection timing calculated in step S4. The fuel injection in the partial lift mode is executed by outputting the injection pulse width signal having the driving waveform indicated by the solid line 2.

On the other hand, if either the injection start timing or the injection end timing falls within the knock detection region in step S5, the controller 20 performs fuel injection in the full lift mode. For this purpose, the controller 20 calculates the pulse width and injection timing of the full lift mode from the fuel injection amount calculated in step S2 in step S6.

Controller 20 determines in FIG. S7 according to the fuel injection pulse width and injection timing calculated in step S6. The fuel injection in the full lift mode is executed by outputting an injection pulse width signal having a drive waveform indicated by a two-dot chain line.

After the process of step S7, the controller 20 ends the routine.

Next, FIG. The execution result of this fuel injection control routine will be described with reference to 9A-9E.

In the situation where fuel injection in the partial lift mode is being executed, for example, when the accelerator pedal of the vehicle is depressed and the engine load increases, FIG. The fuel injection amount calculated in step S2 of 4 increases.

Based on the fuel injection amount calculated in step S2, the controller 20 calculates the fuel injection pulse width and fuel injection timing in the partial lift mode in step S4. In step S5, the fuel injection start timing or the fuel injection end timing is detected by the knock sensor 23. It is determined whether or not it interferes with the knock detection area. Specifically, it is determined whether the fuel injection start timing and the fuel injection end timing are outside the knock detection region.

As long as the fuel injection amount is small, the determination in step S5 is affirmative. In addition, about the case where determination of step S5 is affirmative, FIG. In 9D, it is marked as knock detection area non-interference. In this case, FIG. As shown in 9E, fuel injection in the partial lift mode is continued.

The fuel injection amount increases with the increase in engine load. As shown in 9C, the fuel injection pulse width also increases. FIG. As indicated by 9B, the engine speed also increases.

Increase in fuel injection amount means increase in fuel injection pulse width. As a result, the fuel injection timing interferes with the knock detection region at a certain timing.

Then, the determination in step S5 is FIG. Turn negative as shown in 9D. When the determination in step S5 turns negative, the controller 20 switches the fuel injection mode from the partial lift mode to the full lift mode. And based on the fuel injection quantity calculated | required by step S2, the fuel injection pulse width and fuel injection timing of a full lift mode are calculated by step S6. Then, fuel injection in the full lift mode is executed in step S7 using the fuel injection pulse width and fuel injection timing in the full lift mode calculated in step S6.

Thus, after the controller 20 switches from the partial lift mode to the full lift mode, the fuel injection pulse width and fuel injection timing for the full lift mode are calculated in step S6 in each routine execution. The calculated fuel injection pulse width is the same as that of FIG. As shown in 9C, it becomes smaller than the partial lift mode. As a result, the fuel injection in the full lift mode performed in step S7 can be completed outside the knock detection region.

If fuel injection in the partial lift mode is continued without switching from the partial lift mode to the full lift mode, the fuel injection pulse width increases as the engine load increases. The fuel injection stop timing enters the knock detection region as shown by the dotted line in the figure. As a result, the knock sensor 23 may erroneously detect knock of the internal combustion engine 1.

It is possible to prevent the fuel injection timing from interfering with the knock detection region by executing this fuel injection control routine. Therefore, it is possible to cope with an increase in the fuel injection amount while avoiding erroneous detection of knocking of the internal combustion engine 1 by the knock sensor 23. Even if the mode is switched to the full lift mode, the fuel injection amount is large, so that there is no problem of control accuracy regarding a small amount of fuel injection.

Next, FIG. A fuel injection control routine according to the second embodiment of the present invention will be described with reference to FIG.

This fuel injection control routine and the FIG. The fuel injection control routine of No. 4 differs from the determination process of whether or not the fuel injection timing interferes with the knock detection region. FIG. In the fuel injection control routine of No. 4, the knock detection region is calculated from the engine speed, the fuel injection pulse width and fuel injection timing in the partial lift mode are calculated from the engine load, and the fuel injection timing in the partial lift mode is calculated from the knock detection region. Judging whether to interfere. However, regarding the internal combustion engine 1 of the same specification, the operating state in which the fuel injection timing interferes with the knock detection region can be directly determined using the engine speed and the engine load as parameters. In this embodiment, the engine speed and the engine load threshold value are stored in advance in the ROM of the controller 20, respectively. Then, the controller 20 determines whether or not the fuel injection timing interferes with the knock detection region by comparing the engine rotation speed and the engine load with these threshold values.

For this decision process, the fuel injection control routine uses FIG. While step S4 of the fuel injection control routine of No. 4 is deleted, step S5A is provided instead of step S5.

In step S5A, the controller 20 compares the engine speed and engine load read in step S1 with respective threshold values. When the engine rotation speed exceeds the engine rotation speed threshold value and the engine load exceeds the engine load threshold value, it is determined that the operation range is to apply the full lift mode. In that case, the fuel injection pulse width and fuel injection timing in the full lift mode are calculated in step S6, and the fuel injection corresponding to the calculation result is executed in step S7. On the other hand, it determines with the area | region other than that being the driving | operation area | region which should apply partial lift mode. In that case, fuel injection is executed in step S7 according to the fuel injection pulse width and fuel injection timing in the partial lift mode calculated in step S4.

Fig. The execution result of this fuel injection control routine will be described with reference to 10A-10E.

As in the first embodiment, FIG. As shown in FIG. 10A, when the fuel accelerator in the partial lift mode is being executed, for example, when the accelerator pedal of the vehicle is depressed, FIG. As indicated by 10C, the engine load increases and the fuel injection amount correspondingly increases.

Along with this, FIG. As shown in 10D, the fuel injection pulse width also increases. In addition, FIG. As indicated by 10B, the engine speed also increases.

On the other hand, every time the fuel injection control routine is executed, the controller 20 compares the engine speed with the engine speed threshold value and compares the engine load with the engine load threshold value in step S5A.

At a certain point in time, the engine speed exceeds the threshold value, but at this stage the engine load is still below the threshold value, so the determination in step S5A remains negative and fuel injection is performed in the partial lift mode. When the engine load exceeds the threshold value, the determination in step S5A turns positive, and switching to the full lift mode is performed. Specifically, the controller 20 calculates the fuel injection pulse width and fuel injection timing in the full lift mode in step S6, and executes fuel injection in step S7 using the calculation result in step S6.

The knock detection area is FIG. As shown in 9C, it expands to the advance side as the engine speed increases. On the other hand, the fuel injection timing of the fuel injector 6 moves to the retard side as the engine load increases. By performing the determination in step S5A, FIG. As shown in 10B and 10C, it can be directly predicted whether the fuel injection timing interferes with the knock detection region. By this determination, immediately before the fuel injection timing enters the knock detection region, the FIG. As shown at 10F, the controller 20 switches the fuel injection mode from the partial lift mode to the full lift mode.

Also in this embodiment, as in the first embodiment, by preventing the fuel injection timing from entering the knock detection region, it is possible to avoid erroneous detection of knocking of the internal combustion engine 1 by the knock sensor 23 and to perform fuel injection. It becomes possible to cope with the increase in quantity.

Next, FIG. A fuel injection control routine according to the third embodiment of the present invention will be described with reference to FIG.

This fuel injection control routine and the FIG. The difference from the fuel injection control routine of No. 4 is that step S51 is provided. Other steps are shown in FIG. 4 is the same as the fuel injection control routine.

FIG. Referring to FIG. 6, if it is determined in step S5 that the injection timing interferes with the knock detection region, the controller 20 executes a fuel injection amount increase subroutine in step S51.

FIG. The fuel injection amount increase subroutine executed in step S51 will be described with reference to FIG.

The controller 20 determines whether or not the fuel increase has been completed in step S11. If the increase has not been completed, the controller 20 executes the increase in step S12 and then performs the determination in step S11 again. Thus, a certain amount of fuel increase is executed. As a result, a certain amount is added to the fuel injection amount calculated in step S2. This enriches the air-fuel ratio of the air-fuel mixture in the combustion chamber.

In step S6, the controller 20 calculates the fuel injection pulse width and fuel injection timing in the full lift mode based on the fuel injection amount increased in step S51. The controller 20 performs fuel injection at step S7 using the calculation result at step S6.

The fuel injection amount increase subroutine will be described below.

FIG. Referring to FIG. 8, the control accuracy of the fuel injection amount by the controller 20 differs between the full lift mode and the partial lift mode. F in the figure shows the variation in the fuel injection amount in the full lift mode, and P in the figure shows the variation in the fuel injection amount in the partial lift mode. As shown in the figure, the range of variation in the fuel injection amount in the partial lift mode is smaller than the range of variation in the fuel injection amount in the full lift mode. This is because the control accuracy of the fuel injection amount is higher in the partial lift mode than in the full lift mode.

Generally, fuel injection control is performed so that the internal combustion engine 6 has an air-fuel ratio in the vicinity of 14.7 of the theoretical air-fuel ratio. However, in the vicinity of the theoretical air-fuel ratio, as shown in the figure, the influence of fuel variation has a great influence on the change in generated torque. Therefore, if the partial lift mode is switched to the full lift mode in the vicinity of the theoretical air-fuel ratio, a step may be generated in the generated torque.

When the air-fuel ratio at which the generated torque reaches the maximum value is about 10 in the rich air-fuel ratio, the variation range of the fuel injection amount in the full lift mode is still larger than the variation range of the fuel injection amount in the partial lift mode. However, the effect of the variation on the generated torque is significantly reduced at the rich air-fuel ratio as compared to the variation near the theoretical air-fuel ratio. Therefore, by switching from the partial lift mode to the full lift mode after controlling the air-fuel ratio to the rich air-fuel ratio, the mode can be switched smoothly without generating a torque step. In step S51, FIG. The reason why the fuel injection amount increase subroutine 7 is executed is as described above.

Fig. An execution result of this fuel injection control routine will be described with reference to 11A-11F.

If it is determined in step S5 that the injection timing is within the knock detection region while the internal combustion engine 1 is operating in the partial lift state, FIG. As shown in 11B, switching to the full lift mode is required. The controller 20 executes the fuel injection amount increase subroutine of step S51 in response to this increase request, thereby FIG. The fuel injection amount is increased as indicated by 11C. The controller 20 calculates the fuel injection pulse width and fuel injection timing in the full lift mode corresponding to the fuel injection amount increased in step S51 in step S6.

Controller 20 outputs a pulse width signal in step S7 according to the calculation result in step S6. Thereafter, FIG. As shown in 11C and 11F, the pulse width signal of the drive waveform in the full lift mode corresponding to the increased fuel injection amount is output to the fuel injector 6.

According to this embodiment, similarly to the first embodiment and the second embodiment, the knock detection of the internal combustion engine 1 by the knock sensor 23 is prevented by preventing the fuel injection timing from entering the knock detection region. This makes it possible to cope with an increase in the fuel injection amount. Furthermore, according to this embodiment, it is possible to suppress the occurrence of a torque step due to mode switching.

In addition, when step S51 for executing the fuel increase subroutine is provided between step S5A and step S6 of the second embodiment, a favorable effect can be obtained in suppressing the occurrence of a torque step due to mode switching.

As described above, the fuel injection control device according to the present invention determines whether or not the injection timing of the fuel injector 6 interferes with the knock detection region of the knock sensor 23 from the operating conditions of the internal combustion engine 1, and the injection timing is the knock detection region. In the case of interference, the peak current supplied to the fuel injector 6 is made larger than when the injection timing does not interfere with the knock detection region. Therefore, since the fuel injection pulse width can be reduced, the fuel injector 6 can complete the opening and closing of the fuel injector 6 for fuel injection without interfering with the knock detection region regardless of the operating state of the internal combustion engine 1.

Also, by making the injection timing the fuel injection start timing or the fuel injection end timing, there is no interference with the knock detection region at any of the lift timing of the valve body of the fuel injector 6 or the seating timing on the seat.

For the above control, the controller 20 increases the current supplied to the fuel injector 6 in response to the injection pulse width signal to the first peak current and then decreases it to the valve opening position maintaining current, and the first A partial lift mode in which the voltage is first lowered to a voltage lower than the valve opening position maintaining current after being increased to a second peak current lower than the peak current of 1 and then increased to the valve opening position maintaining current; Apply. When it is determined that the fuel injection timing interferes with the knock detection region during the fuel injection control in the partial lift mode, the peak current supplied to the fuel injector 6 is increased by switching from the partial lift mode to the full lift mode. . In this way, the fuel injection timing can be easily reset by switching between the two preset modes.

Furthermore, the cotton roller 20 increases the fuel injection amount when switching from the partial lift mode to the full lift mode. As a result, the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine 1 changes from the stoichiometric air-fuel ratio to the rich side. Under the rich air-fuel mixture, the fluctuation range of the output torque with respect to the variation in the fuel injection amount is small as compared with the theoretical air-fuel ratio. Therefore, it is possible to smoothly switch the modes by suppressing the step caused in the output torque by the variation in the fuel injection amount accompanying the switching of the modes.

Furthermore, this fuel injection control device uses a crank angle sensor 21 that detects the rotational speed of the internal combustion engine 1 and an air flow meter 22 that detects the load of the engine as sensors that detect the operating conditions of the internal combustion engine 1. The controller 20 calculates a knock detection region based on the rotational speed of the internal combustion engine 1 and sets the injection pulse width and the injection timing based on the rotational speed and load of the internal combustion engine 1. These sensors are sensors generally used for controlling the internal combustion engine 1. Therefore, according to this fuel injection control device, multistage fuel injection that does not interfere with the knock detection region can be realized without using a special sensor.

Furthermore, it is determined whether the injection timing interferes with a predetermined crank angle region by comparing the engine speed with a speed threshold value and comparing the engine load with a load threshold value. Therefore, it is possible to determine whether the injection timing interferes with a predetermined crank angle region without calculating the knock detection region each time. Therefore, the calculation process can be simplified.

As described above, the present invention has been described through some specific embodiments, but the present invention is not limited to the above embodiments. Those skilled in the art can make various modifications or changes to these embodiments within the scope of the claims. For example, in the above-described embodiment, the engine is composed of a 4-cylinder direct injection gasoline internal combustion engine, but the present invention can also be applied to other multi-cylinder internal combustion engines such as 3 cylinders and 6 cylinders.

The exclusive property or feature included in the embodiment of the present invention is claimed as follows.

Claims

Applicable to a direct injection gasoline internal combustion engine that injects fuel into the combustion chamber using a fuel injector that opens by supplying current in accordance with an injection pulse width signal, and has a knock sensor that detects engine knock in a predetermined crank angle region. And
A sensor for detecting engine operating conditions;
Programmable controller programmed as follows:
Determining from the engine operating conditions whether the injection timing of the fuel injector interferes with a predetermined crank angle region;
A fuel injection control device comprising: increasing the peak current supplied to the fuel injector when the injection timing interferes with a predetermined crank angle region than when the injection timing does not interfere with the predetermined crank angle region.
The fuel injection control device according to claim 1, wherein the injection timing is an injection start timing or an injection end timing.
The controller raises the current supplied to the fuel injector in response to the injection pulse width signal to the first peak current and then reduces it to the valve opening position maintaining current, and the second lower than the first peak current. The fuel injection control is executed by selectively applying the partial lift mode in which the current is lowered to a current lower than the valve opening position maintaining current after being increased to the peak current and then increased to the valve opening position maintaining current. And further programmed to switch the fuel injection mode from the partial lift mode to the full lift mode when it is determined that the injection timing interferes with the knock detection region during execution of the fuel injection control in the partial lift mode. The fuel injection control device of 2.
4. The fuel injection control device according to claim 3, wherein the controller is further programmed to enrich the air-fuel ratio of the air-fuel mixture in the combustion chamber when switching from the partial lift mode to the full lift mode.
Sensors that detect engine operating conditions include sensors that detect engine speed and sensors that detect engine load, and the controller:
Calculate a predetermined crank angle region based on the engine speed;
Set injection pulse width and injection timing based on engine speed and load;
The fuel injection control device according to any one of claims 1 to 4, further programmed to determine whether or not the injection timing is within a predetermined crank angle region.
Sensors that detect engine operating conditions include sensors that detect engine speed and sensors that detect engine load, and the controller:
Further programmed to determine whether the injection timing interferes with a predetermined crank angle region by comparing engine speed to a speed threshold and comparing engine load to a load threshold; The fuel injection control device according to any one of claims 1 to 4.
Applicable to a direct injection gasoline internal combustion engine that injects fuel into the combustion chamber using a fuel injector that opens by supplying current in accordance with an injection pulse width signal, and has a knock sensor that detects engine knock in a predetermined crank angle region. And
Means for detecting engine operating conditions;
Means for determining whether the injection timing of the fuel injector interferes with a predetermined crank angle region from engine operating conditions;
Means for increasing the peak current supplied to the fuel injector when the injection timing interferes with a predetermined crank angle region, compared to when the injection timing does not interfere with the predetermined crank angle region;
A fuel injection control device comprising:
A direct-injection gasoline internal combustion engine having a knock sensor for injecting fuel into a combustion chamber using a fuel injector that opens by supplying current in accordance with an injection pulse width signal and detecting knocking of the internal combustion engine in a predetermined crank angle region Applies to
Detect engine operating conditions;
Determining whether the fuel injector injection timing interferes with a predetermined crank angle region from engine operating conditions;
A fuel injection control method in which, when the injection timing interferes with a predetermined crank angle region, the peak current supplied to the fuel injector is made larger than when the injection timing does not interfere with the predetermined crank angle region.