JP2004285892A - Fuel system control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure operation performance during fail safe control under abnormal conditions in a fuel system performing feed back control on fuel discharge pressure while performing variable control on the fuel discharge quantity of a fuel pump according to the required fuel injection quantity of a fuel injection valve. <P>SOLUTION: When an abnormality is determined in a fuel pressure system, lean combustion is prohibited to perform low fuel pressure injection (S1-S3). On the other hand, when an operation range detected with engine rotational speed N and throttle opening TVO comes into the insufficient range of a fuel injection quantity, fail cut control is performed until N becomes N≤NO if the last operation range has been in a low-rotation/ high-load range (S4-S11). If it has been in a high-rotation/low-load range, control for maintaining TVO=TVO0 constant until an intake air quantity Q is reduced to a threshold value Q0 is performed (S12-S14), thereby enlarging the operation range usable at fail safe. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel injection system for a fuel system of an internal combustion engine that performs feedback control of a fuel discharge pressure while variably controlling a fuel discharge amount of a fuel pump according to a required fuel injection amount from a fuel injection valve. The present invention relates to fail-safe control technology.
[0002]
[Prior art]
As described above, there is a fuel system having a variable displacement high-pressure fuel pump that feedback-controls a fuel discharge pressure (hereinafter, simply referred to as a fuel pressure) while variably controlling a fuel discharge amount of a fuel pump. (See Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2000-130232
[Problems to be solved by the invention]
In the above-mentioned conventional fuel system having a variable displacement high-pressure pump, when an abnormality such as a component failure or poor control of the fuel pressure feedback system occurs, the driving of the high-pressure pump is stopped in order to avoid combustion failure due to fuel pressure fluctuation. Then, fail-safe control for stopping the fuel pressure feedback control is performed.
[0005]
In this case, during the fail-safe control, the fuel pressure of the high-pressure fuel system is maintained at a constant low pressure (feed pressure), so that stable injection control is possible. However, the injection period of the fuel injection valve becomes longer than during high-pressure operation. For this reason, in the operation region where the fuel injection amount is large, the injection possible period in the engine cycle may be exceeded, and the required fuel injection amount may be insufficient and the lean injection may occur.
[0006]
Therefore, it was necessary to add a fail-safe control for limiting the intake air amount and the fuel injection amount so as not to enter a region where the fuel injection amount is large during traveling. There was a problem.
[0007]
When the upper limit of the throttle valve opening is restricted as the intake air amount, setting the upper limit of the throttle valve opening in accordance with the fuel injection amount shortage region on the middle to high rotation side sets the low rotation high load region (FIG. 4A) was sometimes restricted. In this case, the required engine torque is insufficient at the time of vehicle start acceleration or uphill, and the driving performance is degraded.
[0008]
On the other hand, when the fuel cut is performed when the engine rotation speed exceeds a predetermined rotation speed as a limitation of the fuel injection amount, the low rotation high load region due to the throttle valve opening restriction can be used, but the middle rotation middle load Is limited in the practical torque region (B in FIG. 4). In this case, the torque required during normal vehicle acceleration or the like is insufficient, and the driving performance deteriorates.
[0009]
The present invention has been made in view of such a conventional problem, and at the time of the abnormality of the fuel system, a fail-safe control capable of satisfying the drivability by expanding a use operation area as much as possible is performed. An object of the present invention is to provide a fuel system control device for an internal combustion engine.
[0010]
[Means for Solving the Problems]
For this reason, the fuel system control device for an internal combustion engine according to the present invention provides an operating condition for limiting the intake air amount when entering a fuel injection amount shortage region after a diagnosis is made that the fuel system is abnormal, The operating conditions for limiting the amount are individually set, and the limiting control is performed according to each operating condition.
[0011]
In this way, by combining the intake air amount limitation and the fuel injection amount limitation, it is possible to widen the operable area during the fail-safe control as compared with the individual limitation, and when starting the vehicle, accelerating, The required torque can be secured when climbing a hill or the like, and the driving performance can be satisfied.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a configuration of a fuel system of an in-cylinder direct injection internal combustion engine equipped with a high-pressure fuel pump according to the present invention.
[0013]
Fuel discharged from an electric low-pressure fuel pump (feed pump) 2 disposed in a fuel tank 1 passes through a fuel filter 3 and a low-pressure pressure regulator 4 to a predetermined low pressure (about 0.3 to 0.5 MPa). After the pressure is adjusted, the pressure is sent to the high-pressure fuel pump 6 through the low-pressure fuel passage 5, pressurized to a high pressure by the high-pressure fuel pump 6 driven by the engine, and supplied to the fuel injection valve 8 through the high-pressure fuel passage 7. A fuel pressure sensor 9 is interposed in the high-pressure fuel passage 7, and a fuel pressure signal detected by the fuel pressure sensor 9 is output to a control unit 10. The control unit 10 also includes a signal from a crank angle sensor 11 for detecting an engine rotation speed N, a cylinder discrimination signal from a cylinder discrimination signal sensor 12, and opening of a throttle valve interposed in an engine intake system (not shown). A signal from a throttle sensor 13 for detecting a degree (hereinafter referred to as a throttle opening) TVO is input.
[0014]
In the high-pressure fuel pump 6, the discharge amount from the pump body 6b is variably controlled by an electromagnetic control valve 6a by a signal from the control unit 10, and is adjusted to an arbitrary high pressure (about 3 to 15 MPa).
[0015]
In the present fuel system, since the fuel pressure is feedback-controlled by the flow balance between the fuel discharge amount of the high-pressure fuel pump 6 and the fuel injection amount of the fuel injection valve 8, the control factor of the fuel pressure feedback control is It becomes the discharge amount. When the actual fuel pressure detected by the fuel pressure sensor 9 is lower than the target fuel pressure, the fuel discharge amount of the high-pressure fuel pump 6 is controlled to increase the fuel pressure until the target fuel pressure is reached, and the actual fuel pressure is higher than the target fuel pressure. In such a case, on the contrary, the fuel discharge amount of the high-pressure fuel pump 6 is reduced, and the fuel pressure is controlled so as to decrease until the fuel pressure reaches the target fuel pressure.
[0016]
Actually, in addition to the fuel discharge amount of the high-pressure fuel pump 6 and the fuel injection amount of the fuel injection valve 8, the fuel pressure of the high-pressure system is determined by the bulk modulus of the fuel, the rigidity of the high-pressure fuel passage (pipe) 7, and the volume of the high-pressure section. Is determined.
[0017]
As shown in FIG. 2, the suction / discharge of the high-pressure fuel pump 6 is caused by a pump drive cam 6c connected to a camshaft of the engine lifts a plunger 6e via a lifter 6d against the urging force of a return spring 6f. The cam 21 is driven by the number of engine cylinders or half the number of cylinders per rotation of the cam 21.
[0018]
In the suction stroke in which the plunger 6e of the high-pressure fuel pump 6 descends, the low-pressure fuel pumped from the fuel tank 1 through the low-pressure fuel passage 6g is sucked into the pressurizing chamber 6h by the pump stroke volume, and then is optionally discharged. At this timing, the solenoid valve 6a is closed to shut off the pressurizing chamber 6h from the low pressure upstream side, thereby starting pressurizing the fuel and sending it to the high pressure fuel passage 7 through the discharge check valve 6i.
[0019]
The required discharge amount of the high-pressure fuel pump 6 is calculated from the target fuel pressure and the fuel injection amount, the engine speed N detected by the crank angle sensor 11, and the pump drive cam phase detected by the cylinder discrimination signal from the cylinder discrimination sensor 12. Thus, the closing operation timing of the electromagnetic control valve 6a is controlled.
[0020]
Further, the control unit 10 diagnoses an abnormality (failure) of the fuel system, and when diagnosing the abnormality, executes the fail-safe fuel injection control according to the present invention.
[0021]
Hereinafter, an embodiment of the fail-safe fuel control will be described with reference to a flowchart shown in FIG.
In step 1, it is diagnosed whether there is an abnormality such as a failure of a fuel system component or a fuel pressure feedback control failure.
[0022]
If it is determined in step 1 that there is an abnormality, lean combustion is prohibited in step 2 to stabilize combustion in order to avoid engine stall and poor driving performance due to poor combustion at the time of abnormality. Stop fuel pressure feedback control. As a result, the fuel pressure of the high-pressure fuel system is kept constant at a low pressure (feed pressure), so that stable injection control can be performed.
[0023]
Due to the low-pressure injection control when the abnormality is detected, the fuel injection amount becomes insufficient in an operation region where the required fuel injection amount is large, and combustion failure occurs. Therefore, in step 4, the engine speed N and the throttle opening TVO are read in order to determine whether or not the operating region is in the fuel injection amount insufficient region. As shown in FIG. 4, the fuel injection deficiency region substantially coincides with a region divided by an arbitrary engine speed N0 and an arbitrary throttle opening TVO0. Here, at the time of the second or subsequent reading, the previously read detection value is stored together with the currently read value.
[0024]
In step 5, it is determined whether or not the engine speed N is larger than the predetermined value N0 and the throttle opening TVO has entered a fuel injection amount shortage region larger than the predetermined value TVO0 based on the current detection value read in step 4. I do.
[0025]
If the fuel injection amount is not within the fuel injection amount shortage region, the flow is terminated without limiting the fuel injection amount.
On the other hand, when it is determined that the operating region has entered the fuel injection amount insufficient region, the routine proceeds to step 7, where it is determined whether or not the previous values of the engine speed N and the throttle opening TVO are stored.
[0026]
If it is determined in step 7 that there is a previous value, the process proceeds to step 8, and it is determined whether or not the previous operation region based on the previous value is N ≦ N0 and TVO> TVO0, that is, the low-speed high-load region. judge.
[0027]
When it is determined in step 8 that the previous operation range is the low rotation and high load range, the process proceeds to step 9 to limit the fuel injection amount so as not to remain in the fuel injection amount shortage region, that is, the fuel cut control. I do.
[0028]
If it is determined in step 7 that there is no previous value, it means that the vehicle has already entered the fuel injection amount insufficiency region when the abnormality is diagnosed. Proceeding to step 12, the throttle opening TVO is controlled to a predetermined value TVO0 constant for dividing the fuel injection amount deficient region. The throttle opening TVO is gradually changed toward a predetermined value TVO0.
[0029]
In step 10, it is determined whether or not the engine speed N has decreased to N0 or less, and the fuel cut control is continued until the engine speed N decreases, and after the decrease, the fuel cut control is released in step 11. Here, in order to prevent hunting in the fuel cut control, the determination value may be set to N0−Nhys (Nhys: rotational speed hysteresis).
[0030]
After canceling the fuel cut control, the process returns to step 6 to record the engine speed N and the throttle opening TVO in the memory as the previous values, and then returns to step 4 to repeat the monitoring of the operating region again.
[0031]
On the other hand, when it is determined in step 8 that the previous operation region is not N ≦ N0 and is not the low rotation high load region of TVO> TVO0, the previous operation region is N> N0 and the high rotation low load of TVO ≦ TVO0 is not satisfied. At this time, it is determined that the vehicle does not suddenly shift from the low-speed low-load region to the high-speed high-load region. In this case, the routine proceeds to step 12, where the throttle opening TVO is determined and the fuel injection amount shortage region is classified. The predetermined value TVO0 is controlled to be constant.
[0032]
In step 13, it is determined whether or not the intake air amount Q has become equal to or less than a limit value Q0 (searched by a map or the like) determined by the throttle opening TVO0 and the current engine rotation speed N. The TVO is maintained at TVO0, and when it becomes equal to or less than Q0, the TVO0 maintenance control is canceled in step S14. Here, in order to prevent hunting of the TVO0 maintenance control, the determination value may be Q0-Qhys (Qhys: throttle opening hysteresis). After the release of the TVO0 maintenance control, the process returns to step 6, and the engine speed N and the throttle opening TVO are recorded in the memory as the previous values.
[0033]
In this way, by combining the intake air amount limitation and the fuel injection amount limitation, it is possible to widen the operable range during the fail-safe control, and to reduce the torque required when starting the vehicle, accelerating, or climbing a slope. And the driving performance can be satisfied.
[0034]
Further, since the configuration is such that the intake air amount limitation and the fuel injection amount limitation are selected according to the operation state immediately before entering the fuel injection amount shortage region, desired operating performance can be ensured as much as possible.
[0035]
In addition, by using fuel cut control for stopping fuel injection as control for limiting the fuel injection amount, the operating range can be reliably and easily limited.
In the first embodiment, the engine rotation speed and the throttle opening immediately before entering the fuel injection amount shortage region are stored, and the previous operation region is determined based on the previously stored value. Each time the rotation speed and the throttle opening are detected, the operation area is determined, and a flag is set for each operation area. Based on the value of the flag, the intake air amount restriction and the fuel injection amount restriction are performed according to the previous operation area. May be selected.
[0036]
FIG. 5 shows a flowchart of the second embodiment having such a configuration.
3 will be described. In step 6 ', the value of the flag F is set to determine the operating region before entering the fuel injection amount insufficient region based on the engine speed N and the throttle opening TVO. Specifically, when N ≦ N0 and TVO> TVO0, the flag F = 1 is set. When N> N0 and TVO ≦ TVO0, the flag F = 2 is set. In other cases, the flag F is set. Is set to clear (0).
[0037]
Then, when the flag F is cleared in step 7 ', that is, when the fail-safe control is started and the fuel injection amount is insufficient, or when the flag F is 1, that is, when the previous operation region is N If ≦ N0 and TVO> TVO0 in the low-speed high-load region, the routine proceeds to step 9, where the control shifts to fuel cut control.
[0038]
On the other hand, if the determination in step 7 'is NO and the flag F is 2, that is, if the previous operation region is a high-speed low-load region where N> N0 and TVO≤TVO0, the routine proceeds to step 12, and the throttle opening TVO Is shifted to the control for maintaining the TVO at TVO0.
[0039]
Since the second embodiment has substantially the same contents as the first embodiment, the same effects can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing a fuel system according to an embodiment of the present invention.
FIG. 2 is a sectional view showing details of a high-pressure fuel pump of the fuel system.
FIG. 3 is a flowchart of fail-safe control according to the first embodiment.
FIG. 4 is a diagram showing a region in which intake air amount restriction control and fuel injection amount restriction control of the embodiment are performed.
FIG. 5 is a flowchart of fail-safe control according to a second embodiment.
[Explanation of symbols]
6 high-pressure fuel pump 7 high-pressure fuel passage 8 fuel injection valve 9 fuel sensor 10 control unit 11 crank angle sensor 12 cylinder discrimination sensor 13 throttle sensor

Claims (6)

After the fuel system of the internal combustion engine, which feedback-controls the fuel discharge pressure while variably controlling the fuel discharge amount of the fuel pump according to the required fuel injection amount from the fuel injection valve, is diagnosed as having an abnormality in the fuel system. When the vehicle enters the fuel injection amount shortage region, the operating condition for limiting the intake air amount and the operating condition for limiting the fuel injection amount are individually set, and the limiting control is performed according to each operating condition. A fuel system control device for an internal combustion engine. The fuel injection amount shortage region is a high rotation and high load region in which the engine rotation speed N is larger than a predetermined value N0 and the opening TVO of a throttle valve interposed in the engine intake system is larger than a predetermined value TVO0. When the vehicle enters the fuel injection amount shortage region from the low-rotation high-load region where ≤N0 and TVO> TVO0, the fuel injection amount is limited, and the fuel injection amount becomes insufficient from the high rotation low-load region where N> N0 and TVO≤TV0. 2. The fuel system control device for an internal combustion engine according to claim 1, wherein when the vehicle enters the region, the amount of intake air is limited. After being diagnosed as having an abnormality in the fuel system, the previous value is stored while detecting the engine rotational speed and the throttle opening, and when it is detected that the fuel injection amount is insufficient, the previous value is used according to the previous value. 3. The fuel system control device for an internal combustion engine according to claim 2, wherein it is determined whether to limit the intake air amount or the fuel injection amount with reference to the detected area. After being diagnosed as having an abnormality in the fuel system, a flag was set according to an area determined by these detected values while detecting the engine rotational speed and the throttle opening, and it was detected that the fuel injection amount was in the shortage area. 3. The fuel system control device for an internal combustion engine according to claim 2, wherein the control unit determines whether to limit the intake air amount or the fuel injection amount by referring to a value of the flag. The fuel system control device for an internal combustion engine according to any one of claims 1 to 3, wherein the control for limiting the fuel injection amount is a fuel cut control for stopping fuel injection. The internal combustion engine according to any one of claims 1 to 5, wherein the restriction of the intake air amount or the restriction of the fuel injection amount is performed after performing control to reduce a fuel injection pressure. Fuel system controller.

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