JP3777340B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply control device for a direct injection internal combustion engine that injects high-pressure fuel directly into a combustion chamber.
[0002]
[Prior art]
In a fuel supply system that injects high-pressure fuel directly into a combustion chamber of an internal combustion engine, the fuel pumped up from a fuel tank by a low-pressure fuel pump is boosted by a high-pressure fuel pump driven by a cam or the like of the internal combustion engine, and the high-pressure fuel such as a common rail The pressure is accumulated in the pipe, and the accumulated fuel is directly injected into the combustion chamber by an injector. In order to control the fuel injection amount, it is necessary to accurately control the accumulated fuel pressure. This fuel pressure is controlled using a variable displacement pump that makes the discharge amount of the high-pressure fuel pump variable. This is achieved by discharging only the required amount of fuel into the high-pressure fuel piping system.
[0003]
This discharge amount is controlled by calculating and controlling the target discharge amount of the high-pressure fuel pump by feedforward control calculated from the rotational speed and load of the internal combustion engine and the target fuel pressure in the high-pressure fuel pipe. The fuel pressure in the pipe is adjusted to the target fuel pressure, according to the deviation between the target pressure in the high-pressure fuel pipe and the actual fuel pressure detected by the fuel pressure sensor for fuel pressure detection provided in the high-pressure fuel pipe. In general, the fuel pressure in the high-pressure fuel pipe is controlled to the target fuel pressure by finely adjusting the fuel discharge amount or the discharge start timing by feedback control.
[0004]
For example, Japanese Patent Application Laid-Open No. 11-30150 discloses a technique for accurately controlling the fuel pressure in such a high-pressure fuel pipe. In order to control the fuel pressure in the high pressure fuel pipe to the target pressure, the technique disclosed in this publication is based on the target fuel pressure in the high pressure fuel pipe and the valve opening time of the fuel injection valve. In addition to the configuration that calculates the feedforward amount of the fuel and performs feedback control according to the deviation between the target fuel pressure and the actual fuel pressure, the fuel leak according to the rotational speed of the high-pressure fuel pump and the fuel temperature with respect to the feedforward amount This corrects the amount, and with this correction, it calculates the exact target pump discharge amount regardless of the operating environment and operating conditions of the high-pressure fuel pump, and controls the fuel pressure in the high-pressure fuel pipe to the target fuel pressure more accurately. It is what you do.
[0005]
[Problems to be solved by the invention]
However, the correction described in this publication is a correction of the leak amount according to the rotational speed and temperature of the high-pressure fuel pump and the fuel pressure to the basic discharge amount obtained from the target fuel pressure and the fuel injection valve opening period. Since this is an implemented value, the control assumes that the fuel pressure in the high-pressure fuel pipe is constantly stable. In this case, the control can be performed with high accuracy, but the target fuel pressure in the high-pressure fuel pipe When is changed, the fuel pressure cannot be immediately controlled as the target value.
[0006]
Even in such a case, the actual fuel pressure is corrected so as to coincide with the target fuel pressure by feedback control after a certain amount of time has passed, but there is a problem that it cannot be followed with good responsiveness. Also, when the control gain of feedback control is set large to improve the responsiveness, the responsiveness improves when the deviation is large, but when the deviation is small, problems such as hunting and overshoot occur. There is a problem in that it is impossible to set a control gain that optimizes followability to the target fuel pressure in order to perform stable control.
[0007]
The present invention has been made to solve such a problem, and calculates the amount of required fuel with respect to a change in the target fuel pressure in the high-pressure fuel pipe, and corrects the feedforward amount based on the calculation result. An object of the present invention is to obtain a fuel supply control device for an internal combustion engine that can immediately follow a change in target fuel pressure.
[0008]
[Means for Solving the Problems]
A fuel supply control device for an internal combustion engine according to the present invention includes a high pressure pipe for accumulating fuel pressurized by a variable discharge type high pressure fuel pump, and a cylinder of the internal combustion engine at a predetermined timing for fuel accumulated in the high pressure pipe. An injector for injecting the fuel into the inside, and a control means for controlling the fuel injection timing and the injection amount by the injector and controlling the fuel pressure in the high-pressure pipe, the control means changing according to the operating state of the internal combustion engine The target fuel pressure in the high-pressure piping is obtained for each operation cycle, and the fuel deviation correction flow rate corresponding to the target fuel pressure change is calculated from the deviation between the previous value and the current value of the target fuel pressure, and the deviation correction flow rate of this calculation result is calculated. The discharge amount of the high-pressure fuel pump is corrected from the correctable amount per discharge, which is the difference between the maximum discharge flow rate of the high-pressure fuel pump and the fuel injection flow rate .
[0009]
In addition, when the control means has an excess or deficiency in the actual correction amount with respect to the previous deviation correction flow rate corresponding to the target fuel pressure change for each operation cycle , this excess and deficiency is integrated and reflected in the next correction amount. Is.
Further, the discharge amount of the high-pressure fuel pump is determined according to the discharge amount discharged from the high-pressure pipe to the injector, and the control means calculates this discharge amount from the valve opening time of the injector and the fuel pressure in the high-pressure pipe. It is what I did.
[0010]
Furthermore, when the discharge amount per discharge cycle corrected by the high pressure fuel pump is set as the target discharge amount, the control means sets the limit value of the target discharge amount to be equal to or less than the maximum value of the discharge capacity of the high pressure fuel pump. It is a thing .
[0011]
Further, the control means subtracts the discharge amount from the high-pressure pipe from the target discharge amount limit value every operation cycle of the high-pressure fuel pump, and calculates the correction amount per discharge from the subtraction value and the deviation of the target fuel pressure. It is to be calculated.
Furthermore, the control means determines whether the fuel pressure in the high-pressure pipe is increased or decreased based on the integrated value of the deviation correction flow rate corresponding to the target fuel pressure change for each operation cycle.
[0012]
The control means, when the fuel pressure in the high-pressure pipe is determined to be pressure increase, the correction per high-pressure fuel pump-discharge is this correction amount from the integrated value of the deviation correction flow rate corresponding to the target fuel pressure change The amount is subtracted and reflected in the next correction.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
1 is a schematic configuration diagram of a fuel supply control apparatus for an internal combustion engine according to Embodiment 1 of the present invention, and FIG. 2 is a flowchart for explaining a processing operation. In FIG. 1, the internal combustion engine 1 is an example of a spark ignition gasoline engine, and fuel is pumped from a fuel tank 2 by a low pressure fuel feed pump 3 and supplied to a high pressure fuel pump 4. The fuel pressurized by the high-pressure fuel pump 4 is accumulated in the high-pressure pipe 5 and supplied from the high-pressure pipe 5 to the injector 6. The high-pressure pipe 5 is provided with a fuel pressure sensor 7 for measuring the fuel pressure of the pressurized fuel, and the high-pressure fuel pump 4 is provided with a low-pressure spill valve 8 for returning unnecessary fuel to the fuel tank 2. A crank angle sensor 9 is provided on the crankshaft of the internal combustion engine 1. Signals from the fuel pressure sensor 7 and the crank angle sensor 9 are given to the control means 10, and the control means 10 inputs various signals to control the fuel injection amount, the injection timing, the ignition timing, and the like, and the high-pressure pipe 5 The fuel pressure accumulated in the engine is controlled.
[0014]
The injector 6 is configured to inject fuel directly into the cylinder of the internal combustion engine 1. However, when fuel is injected in the compression stroke of the internal combustion engine 1, the fuel pressure is relatively higher than the compression pressure in the cylinder. For this reason, the fuel pumped up from the fuel tank 2 by the low-pressure fuel feed pump 3 is pressurized by a high-pressure fuel pump 4 mechanically driven by a cam or the like of the internal combustion engine 1, and the high-pressure fuel pump 4 is pressurized. Supplied to the pipe 5. A check valve (not shown) is attached to a connection portion between the high-pressure fuel pump 4 and the high-pressure pipe 5, and the fuel discharged to the high-pressure pipe 5 by this check valve is accumulated in the high-pressure pipe 5 and is injected by the injector 6. It is injected into the cylinder of the internal combustion engine 1.
[0015]
The fuel pressure in the high-pressure pipe 5 is changed by increasing / decreasing the amount of accumulated fuel. For this reason, a variable discharge type high-pressure fuel pump is used as the high-pressure fuel pump 4. In this variable discharge type high pressure fuel pump, a low pressure spill pipe is provided in parallel with the fuel suction pipe of the plunger of the fixed discharge type high pressure fuel pump, and an electrical connection is made between the high pressure fuel pump 4 and the low pressure spill pipe. A low-pressure spill valve 8 that is an electromagnetic valve that can be opened and closed is attached to the high-pressure pipe 5 by controlling opening and closing at a predetermined timing during the pressurization and discharge stroke of the high-pressure fuel pump 4. The excess fuel is discharged into the spill pipe.
[0016]
The opening / closing control of the low pressure spill valve 8 is controlled by the control means 10 by detecting the fuel pressure in the high pressure pipe 5 detected by the fuel pressure sensor 7. In addition, the low pressure spill pipe is configured to return to the fuel tank 2 in FIG. 1, but is connected to the suction side of the plunger of the high pressure fuel pump 4 and re-sucked in the suction stroke of the high pressure fuel pump 4. Can be taken. The basic control method of the high-pressure fuel pump 4 will be described as follows.
[0017]
First, when the fuel pressure in the high-pressure pipe 5 is controlled to be constant, the same amount of fuel injected by the injector 6 may be discharged from the high-pressure fuel pump 4 and replenished to the high-pressure pipe 5. When the fuel pressure in the high-pressure pipe 5 is changed, this balance is lost, and the difference between the amount of fuel injected by the injector 6 and the amount of fuel discharged from the high-pressure fuel pump 4 and replenished to the high-pressure pipe 5 is lost. It will suffice if it is provided. Here, the injection amount of the injector 6 is determined by the operating state of the internal combustion engine 1. For this purpose, the valve opening time of the injector 6 and the fuel pressure in the high pressure pipe 5 are controlled. In order to control the fuel pressure, the discharge amount of the high-pressure fuel pump 4 is basically changed.
[0018]
Subsequently, the discharge amount correction processing method of the high-pressure fuel pump 4 according to the target fuel pressure change in the high-pressure pipe 5 accompanying the change in the operating state of the internal combustion engine will be described with reference to the flowchart of FIG. A case will be described as an example in which the injection of the injector 6 for one discharge of the high-pressure fuel pump 4 is one injection, and this discharge and injection are controlled as a set and the control cycle is performed for each discharge.
[0019]
In FIG. 2, when the operation is started, the control means 10 first compares the target fuel pressure (PFobjold) in the previous cycle with the current target fuel pressure (PFobj) in step 201, and calculates the deviation (PFobjdlt). calculate. Subsequently, the routine proceeds to step 202, where a deviation correction flow rate (QFobjjlt), which is a flow rate of the fuel corresponding to the target fuel pressure deviation (PFobjdlt), is calculated from the conversion data (TQFobjjlt) stored in the ROM in the control means 10.
[0020]
The deviation correction flow rate (QFobjjlt) calculated here corresponds to the fluctuation of the target fuel pressure in the high pressure pipe 5 in one control cycle, that is, in this embodiment, one discharge cycle of the high pressure pipe 5. Since the target fuel pressure varies depending on the operating state of the internal combustion engine 1, the direction of this fluctuation can take either a positive or negative value.
[0021]
Based on the deviation correction flow rate (QFobjjlt) corresponding to the target fuel pressure fluctuation in the high-pressure pipe 5 calculated in this way, the discharge amount correction of the high-pressure fuel pump 4 is performed as follows. First, in step 203, the deviation correction flow rate (QFobjjlt) is added to the correction remaining amount (QFobjjrst) in the previous control cycle to update the value of the correction remaining amount (QFobjjrst). Since the discharge amount of the high-pressure fuel pump 4 is finite as will be described later, this excess / deficiency is integrated when the actual correction amount with respect to the previous deviation correction flow rate is excessive / deficient.
[0022]
Subsequently, the routine proceeds to step 204 where the effective drive time (Tinj) relating to fuel injection and the inside of the high-pressure pipe 5 input to the control means 10 at a predetermined timing from the control information of the injector 6 that is separately operated and controlled by the control means 10. Read the fuel pressure (PFreal). In the next step 205, the effective drive time (Tinj) and the flow rate gain (Gi) per hour when the injector 6 is at the reference fuel pressure are integrated to calculate the fuel injection amount (QFinjref) at the reference fuel pressure. Then, the fuel injection amount (QFinjref) at the time of the reference fuel pressure is corrected by the value of the fuel pressure (PFreal) in the high-pressure pipe 5 to calculate the fuel injection flow rate (QFinj) of the injector 6 in the current control cycle. The fuel injection flow rate (QFinj) here corresponds to the fuel discharge amount in the high-pressure pipe 5.
[0023]
In the following step 207, per discharge based on the conversion data (TQFoutmax) stored in advance in the ROM in the control means 10, the fuel pressure (PFreal) in the high-pressure pipe 5 and the rotation speed (Npmp) of the high-pressure fuel pump 4. The maximum discharge flow rate (QFoutmax) of the high-pressure fuel pump 4 is calculated. This calculated value corresponds to the limit value of the target discharge amount per discharge.
[0024]
Subsequently, in step 208, the corrected remaining amount (QFobjjltrst) calculated by updating in step 203 is compared with a predetermined value. If the corrected remaining amount (QFobjjltrst) is larger than the predetermined value, It is determined that the target fuel pressure is a pressure increase change, and the process proceeds to step 209. If not, it is determined in step 214 whether the value of the remaining correction amount (QFobjjltrst) is smaller than a predetermined value. If it is smaller, it is determined that the target fuel pressure in the high-pressure pipe 5 is a change in pressure reduction. Proceed to step 215.
[0025]
If it is determined in step 208 that the target fuel pressure change in the high pressure pipe 5 is a pressure increase change, the process proceeds to step 209, where the maximum discharge flow rate (QFoutmax) and fuel injection flow rate (QFinj) of the high pressure fuel pump 4 are set. The difference is calculated as a correctable amount per discharge (QFobjjltcbuf). In the next step 210, it is determined whether or not this calculation result is larger than the previously calculated correction remaining amount (QFobjjltrst). If it is larger, the required flow rate for the target fuel pressure change in the high pressure pipe 5 is greater than that of the high pressure fuel pump 4. It is determined that the correction can be performed by one discharge, and the process proceeds to step 211, and the value of the remaining correction amount (QFobjjltrst) is substituted as the correction amount per discharge (QFobjjltc).
[0026]
If the determination result in step S210 is not large, it is determined that the required flow rate for the target fuel pressure change in the high-pressure pipe 5 cannot be corrected by one discharge of the high-pressure fuel pump 4, and the process proceeds to step 212. The value of the possible amount (QFobjjltcbuf) is substituted as the correction amount (QFobjjltc) per discharge. As a result, when the required flow rate for the target fuel pressure change in the high-pressure pipe 5 cannot be corrected by one discharge, it is possible to obtain the best responsiveness in the system by discharging at the maximum capacity of the high-pressure fuel pump 4. Become. In the next step 213, the correction amount (QFobjjltc), which is the current correction amount, is subtracted from the correction remaining amount (QFobjjltrst) in the high-pressure pipe 5 to update the value of the correction remaining amount (QFobjjltrst).
[0027]
If the value of the remaining correction amount (QFobjjrstrst) is smaller than the predetermined value in step 214, the process proceeds to step 215, and processing is performed when the target fuel pressure change in the high pressure pipe 5 is a reduced pressure change. In this process, first, in step 215, it is determined whether or not the absolute value of the correction remaining amount (QFobjjltrst) is smaller than the fuel injection flow rate (QFinj). If it is smaller, it is determined that the fuel pressure in the high-pressure pipe 5 can be made the target fuel pressure by correcting for one discharge, and the process proceeds to step 216, and the value of the remaining amount of correction (QFobjdlrst) is set to the correction amount per discharge ( QFobjjltc).
[0028]
If the absolute value of the remaining correction amount (QFobjjltrst) is not smaller than the fuel injection flow rate (QFinj) in step 215, it is determined that the required flow rate for the target fuel pressure change in the high-pressure pipe 5 is unnecessary, and the flow returns to step 217. The fuel injection flow rate (QFinj) is converted into a negative value and substituted as a correction amount per discharge (QFobjjltc). In Step 218, the correction amount (QFobjjltc) to be corrected this time is subtracted from the correction remaining amount (QFobjjltrst) to update the value of the correction remaining amount (QFobjjltrst). If the value of the remaining correction amount (QFobjjlrst) is not smaller than the predetermined value in step 214, it is equal to the predetermined value. In this case, the process proceeds to step 219 and the correction amount becomes zero.
[0029]
Finally, the routine proceeds to step 220, where the correction amount (QFobjjltc) calculated this time is added to the basic target discharge amount (QFbase) of the high-pressure fuel pump 4 separately calculated by the control means 10, and the target discharge amount (QFout) of the high-pressure fuel pump 4 is added. And the discharge amount of the high-pressure fuel pump 4 is controlled in a separate routine. The remaining correction amount (QFobjjltrst) added to the deviation correction flow rate (QFobjjlt) in step 203 of the next routine is updated in step 213 or step 218, and the corrected remaining amount (QFobjjltrst) is thus Will be accumulated.
[0030]
By controlling in this way, the required fuel amount in the high-pressure pipe 5 when the target fuel pressure in the high-pressure pipe 5 changes can be corrected by feedforward, so that the response is good and the required flow rate is physically equal. Even if the amount cannot be controlled by controlling the discharge amount of the high-pressure fuel pump 4 times, the calculation results are accumulated and stored, and only the amount that can be corrected by one-time control is calculated to calculate the The amount of correction is calculated by subtracting the calculated value from the integrated amount, which is reflected in the discharge amount control, and can be controlled with the best responsiveness on the high-pressure fuel system without overshoot or undershoot. It is.
[0031]
【The invention's effect】
As described above, in the fuel supply control apparatus for an internal combustion engine according to the present invention, according to the first aspect of the present invention, the high-pressure pipe for accumulating the fuel pressurized by the discharge-variable high-pressure fuel pump, And an injector for injecting the accumulated fuel into the cylinder of the internal combustion engine at a predetermined timing, and a control means for controlling the fuel injection timing and the injection amount by the injector and controlling the fuel pressure in the high-pressure pipe. The control means obtains the target fuel pressure in the high-pressure pipe that changes according to the operating state of the internal combustion engine every operation cycle, and responds to the target fuel pressure change from the deviation between the previous value and the current value of the target fuel pressure. calculating a deviation correction flow rate of the fuel, from the deviation correction flow rate of this calculation result, the correctable amount per discharge is the difference between the maximum discharge flow rate and the fuel injection flow rate of the high pressure fuel pump, the high pressure fuel Since so as to correct the discharge amount of pump, the fuel pressure in the high pressure pipe can be corrected at the target fuel pressure in the feed-forward, in which it is possible to preferably correct response. Further, when the control means has an excess or deficiency in the actual correction amount with respect to the deviation correction flow rate corresponding to the target fuel pressure change for each operation cycle, the excess and deficiency is integrated and reflected in the next correction amount. Therefore, even if the target fuel pressure cannot be corrected by a single correction due to the discharge capacity of the high-pressure fuel pump, etc., the integrated value can be stored and the fuel pressure in the high-pressure piping can be corrected to the target fuel pressure. Undershoot can be prevented.
[0033]
Further, according to the invention described in claim 2, in the invention of claim 1, the discharge amount of the high-pressure fuel pump is determined according to the discharge amount discharged from the high-pressure pipe to the injector, and the control means performs the discharge. Since the amount is calculated from the valve opening time of the injector and the fuel pressure in the high pressure pipe, the correction amount can be easily calculated by the control means.
[0034]
Furthermore , according to the invention of claim 3, in the invention of claims 1-2, when the discharge amount per discharge cycle corrected by the high-pressure fuel pump is set as the target discharge amount, the control means has the target discharge amount. Since the limit value of the amount is set to be equal to or less than the maximum value of the discharge capacity of the high-pressure fuel pump, the high-pressure fuel pump can accurately correct following the calculated value of the correction amount.
[0035]
According to the invention described in claim 4, the control means subtracts the discharge amount from the high-pressure pipe from the limit value of the target discharge amount every operation cycle of the high-pressure fuel pump, and the deviation between the subtracted value and the target fuel pressure. Thus, the correction amount per discharge is calculated, so that the correction amount that matches the discharge capacity of the high-pressure fuel pump can be determined.
[0036]
Furthermore, according to the invention described in claim 5, the control means is based on a correction remaining amount including an integrated value of excess and deficiency of the deviation correction flow rate corresponding to the target fuel pressure change for each operation cycle. Since the increase or decrease of the fuel pressure in the high-pressure pipe is determined, the correction for each operation cycle can be easily and accurately determined .
[0037]
According to the sixth aspect of the present invention, when the control means determines that the fuel pressure in the high pressure pipe is increased, the deviation correction flow rate corresponding to the target fuel pressure change is integrated. Since the correction amount per discharge of the high-pressure fuel pump, which is the correction amount this time, is subtracted from the correction remaining amount including the value, the fuel pressure correction amount in the high-pressure pipe can be accurately calculated. .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fuel supply control device for an internal combustion engine according to Embodiment 1 of the present invention;
FIG. 2 is a flowchart illustrating a processing operation of the internal combustion engine fuel supply control apparatus according to Embodiment 1 of the present invention;
[Explanation of symbols]
1 internal combustion engine, 2 fuel tank, 3 low pressure fuel feed pump,
4 High pressure fuel pump, 5 High pressure piping, 6 Injector,
7 Fuel pressure sensor, 8 Low pressure spill valve, 9 Crank angle sensor,
10 Control means.

Claims (6)

  High pressure piping for accumulating fuel pressurized by a variable discharge amount type high pressure fuel pump, an injector for injecting fuel accumulated in the high pressure piping into a cylinder of an internal combustion engine at a predetermined timing, and timing of fuel injection by the injector And a control means for controlling the fuel pressure in the high-pressure pipe, and the control means determines the target fuel pressure in the high-pressure pipe that changes according to the operating state of the internal combustion engine as an operating cycle. The deviation correction flow rate of the fuel corresponding to the change in the target fuel pressure is calculated from the deviation between the previous value and the current value of the target fuel pressure, and the deviation correction flow rate of the calculation result and the high pressure fuel pump The discharge amount of the high-pressure fuel pump is corrected from the correctable amount per discharge which is the difference between the maximum discharge flow rate and the fuel injection flow rate, and the target fuel pressure for each operation cycle is corrected. If there is excess or deficiency in the actual correction value for the previous deviation correction flow rate corresponding to the reduction, the fuel supply control system for an internal combustion engine, characterized in that after next correction amount by integrating the excess or deficiency.   The discharge amount of the high-pressure fuel pump is determined according to the discharge amount discharged from the high-pressure pipe to the injector, and the control means determines the discharge amount based on the valve opening time of the injector and the fuel pressure in the high-pressure pipe. The fuel supply control device for an internal combustion engine according to claim 1, wherein   When the corrected discharge amount per discharge cycle of the high-pressure fuel pump is set as a target discharge amount, the control means sets the limit value of the target discharge amount to be equal to or less than the maximum value of the discharge capacity of the high-pressure fuel pump. The fuel supply control apparatus for an internal combustion engine according to claim 1 or 2,   The control means subtracts the discharge amount from the high-pressure pipe from the limit value of the target discharge amount for each operation cycle of the high-pressure fuel pump, and determines the per-discharge amount from the subtraction value and the deviation of the target fuel pressure. 4. The fuel supply control apparatus for an internal combustion engine according to claim 3, wherein a correction amount is calculated.   The control means increases the fuel pressure in the high-pressure pipe based on the correction remaining amount including the integrated value of the excess and deficiency of the deviation correction flow rate corresponding to the target fuel pressure change for each operation cycle, or The fuel supply control device for an internal combustion engine according to any one of claims 1 to 4, wherein the pressure reduction is determined. When the control means determines that the fuel pressure in the high-pressure pipe is increased, it corrects this time from a correction remaining amount that includes an integrated value of excess and deficiency of the deviation correction flow rate corresponding to the target fuel pressure change. 6. The fuel supply control device for an internal combustion engine according to claim 1, wherein a correction amount per discharge of the high-pressure fuel pump, which is a minute, is subtracted and reflected in the next correction .

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