JP3562137B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device that controls a fuel injection amount and an EGR (exhaust gas recirculation) amount in an internal combustion engine (particularly, a diesel engine).
[0002]
[Prior art]
As a control device for a conventional internal combustion engine, as disclosed in Japanese Patent Publication No. 60-55696, the maximum fuel injection amount (when the normally calculated fuel injection amount exceeds (A value that limits the amount of injection). Further, as disclosed in Japanese Patent Application Laid-Open No. 63-143343, during acceleration operation, the maximum fuel injection amount is reduced and corrected, and EGR is stopped. These are in view of the fact that smoke (PM) is generated when the fuel injection amount is rapidly increased in a state where the EGR amount is large. The basic value of the maximum fuel injection amount is set according to the engine speed and the like.
[0003]
[Problems to be solved by the invention]
However, even if the maximum fuel injection amount is reduced and corrected in this way, if the correction is uniformly performed depending on the presence or absence of EGR, the maximum fuel injection amount is the same even if the EGR rate changes, and the injection amount is reduced too much. Sufficient output was not obtained, or smoke was generated due to too small a throttle, making it difficult to achieve both exhaust performance and operation performance.
[0004]
Further, it was found that even when the correction amount for the maximum fuel injection amount was changed depending on the target EGR rate, the same thing as described above occurred due to the dynamics of air during transition.
The present invention has been made in view of the above circumstances, and has as its object to optimize control of a fuel injection amount and an EGR amount.
[0005]
[Means for Solving the Problems]
Therefore, according to the first aspect of the present invention, as shown in FIG. 1, an operating state detecting means for detecting an operating state of the engine including at least the engine speed, the accelerator opening, the intake air amount, and the EGR amount; Basic fuel injection amount calculating means for calculating a basic fuel injection amount based on the number and the accelerator opening degree; maximum fuel injection amount calculating means for calculating a maximum allowed fuel injection amount based on the intake air amount and the EGR amount; A fuel injection amount setting means for comparing the basic fuel injection amount with the maximum fuel injection amount and setting a smaller one as a final fuel injection amount, and a fuel injection for controlling a fuel injection amount to the engine according to the final fuel injection amount. and amount control means, a target EGR rate calculating means for calculating a target EGR rate based on the engine speed and the basic fuel injection amount, the final fuel injection amount to at least the basic fuel injection amount Depending on, and the target EGR rate correction means for correcting the target EGR rate, the EGR quantity control means for controlling the EGR amount according to the target EGR rate provided, constituting a control apparatus for an internal combustion engine.
[0006]
That is, while setting the maximum fuel injection amount based on the intake air amount and the EGR amount, the setting of the maximum fuel injection amount is optimized, while the final fuel injection amount with respect to the basic fuel injection amount is determined according to the ratio. Then, the target EGR rate is corrected, and the EGR amount is corrected to be reduced based on the correction degree of the fuel injection amount on the decreasing side.
According to a second aspect of the present invention, in the first aspect of the invention, the target EGR rate correction means is configured to set a target EGR rate according to a ratio of a final fuel injection amount to a basic fuel injection amount and an accelerator opening. Is corrected.
[0007]
That is, in consideration of the accelerator opening, the target EGR rate is corrected to decrease as the opening increases.
In the invention according to claim 3 , in the invention according to claim 1 , the target EGR rate correction means sets the target EGR rate in accordance with a ratio of a final fuel injection amount to a basic fuel injection amount and a degree of acceleration. It is characterized in that it is to be corrected.
[0008]
That is, in consideration of the degree of acceleration, the target EGR rate is corrected to be reduced as the acceleration increases.
In this case, the degree of acceleration may be detected by the amount of change in the accelerator opening as in the invention according to claim 4 , or may be detected by the amount of change in vehicle speed as in the invention according to claim 5. Good.
[0009]
In the invention according to claim 6 , in the invention according to claims 1 to 5 , the maximum fuel injection amount calculating means is configured such that the amount of air taken into the cylinder is Qac, the amount of EGR is Qec, the limit excess air ratio (rich When the limit is Klamb, the maximum fuel injection amount Qful is calculated by the following equation.
Qful = (Qac + Qec × KOR) / (Klamb × 14.7)
However, KOR is a constant.
[0010]
The reason why the EGR amount is also taken into account in the calculation of the maximum fuel injection amount is that especially in the case of a diesel engine, combustion is performed in a lean atmosphere, and the exhaust gas also contains a large amount of oxygen.
[0011]
【The invention's effect】
According to the first aspect of the present invention, the maximum fuel injection amount is set based on the intake air amount and the EGR amount to optimize the setting of the maximum fuel injection amount, while the final fuel injection amount is determined based on the basic fuel injection amount. In the control of the fuel injection amount and the EGR amount , the target EGR rate is corrected according to the ratio of the fuel injection amount, and the EGR amount is corrected to be reduced based on the correction degree of the fuel injection amount to the decreasing side . Thus, it is possible to obtain an effect that both exhaust performance and driving performance can be achieved.
[0012]
Also, there is an advantage that the generation of smoke can be prevented even when the intake air amount is reduced at high altitude and the maximum fuel injection amount is reduced.
According to the second aspect of the present invention, the target EGR rate can be reduced and corrected for a higher opening in consideration of the accelerator opening.
According to the third aspect of the present invention, the target EGR rate can be corrected to decrease as the acceleration increases, in consideration of the degree of acceleration.
[0013]
According to the invention according to claim 4 , the degree of acceleration can be accurately grasped from the amount of change in the accelerator opening.
According to the fifth aspect of the present invention, the degree of acceleration can be accurately grasped from the amount of change in vehicle speed.
According to the invention of claim 6 , the reliability of setting the maximum fuel injection amount can be greatly improved.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
FIG. 2 is a system diagram.
The fuel injection pump 1 includes a control sleeve (not shown) as a fuel injection amount control means therein, and the control sleeve is driven by a signal from the control unit 3 via a motor or the like. The fuel injection amount is controlled.
[0015]
The EGR valve 2 is provided in an EGR passage that communicates the exhaust system and the intake system of the engine, and receives a signal from the control unit 3 to use a solenoid valve for negative pressure control in the case of a negative pressure operation type, a direct acting type. In the case of (1), it is driven via a step motor or the like, and controls the EGR amount as an EGR amount control means so as to reach the target EGR rate.
Signals are input to the control unit 3 from various sensors as operating state detecting means. Specifically, signals are input from a crank angle sensor 4, an accelerator opening sensor 5, an air flow meter 6, an EGR flow meter 7, a water temperature sensor 8, an intake pressure sensor 9, a vehicle speed sensor 10, and the like.
[0016]
Here, the control unit 3 controls the fuel injection pump 1 and the EGR valve 2 by performing arithmetic processing by a built-in microcomputer according to a flowchart described later.
FIG. 3 shows a calculation flow of the basic fuel injection amount, which is executed at a timing synchronized with the engine rotation, for example, using a signal from a crank angle sensor as a trigger. This flow corresponds to basic fuel injection amount calculation means.
[0017]
In step 1 (shown as S1 in the figure, the same applies hereinafter), the engine speed Ne calculated based on the cycle of the signal from the crank angle sensor and the like is read.
In step 2, the accelerator opening Cl detected based on the signal from the accelerator opening sensor is read.
In step 3, the basic fuel injection amount Mqdrv is set from the engine speed Ne and the accelerator opening Cl with reference to a basic fuel injection amount map as shown in FIG.
[0018]
In step 4, various corrections including a water temperature correction are performed on the basic fuel injection amount Mqdrv, thereby obtaining a corrected basic fuel injection amount Qsol1 and terminating the process.
FIG. 5 shows a flow of detecting the amount of intake air, which is executed at predetermined time intervals.
In step 11, the intake air flow rate Qas0-d detected based on the signal from the air flow meter is read. Specifically, the output voltage of the air flow meter is converted into an intake air amount Qas0-d using a predetermined voltage-flow rate conversion table.
[0019]
In step 12, a weighted average process is performed on the intake air amount Qas0-d according to the following equation to obtain the intake air amount Qas0, and the process ends.
Qas0 = Qas0n _-1 × (1-KF) + Qas0-d × KF
However, KF is a constant.
FIG. 6 is a calculation flow of the cylinder intake air amount (the amount of air taken into the cylinder), which is executed at a timing synchronized with the engine rotation.
[0020]
In step 21, the intake air flow rate Qas0 according to the flow of FIG. 5 is read.
In step 22, the engine speed Ne is read.
In step 23, the unit converts the intake air amount Qas0 into an intake air amount Qac0 per intake by the following equation.
Qac0 = (Qas0 / Ne) × KC
However, KC is a constant.
[0021]
In step 24, delay processing for the transport delay from the air flow meter to the collector is performed by the following equation. That is, Qac0 _nL , which is the L-th previous Qac0, is read out, and is defined as Qacn.
Qacn = Qac0 _nL
Here, L is a constant.
[0022]
In step 25, a delay process corresponding to the dynamics in the collector is performed by the following equation, whereby the cylinder intake air amount Qac is obtained, and the process ends.
Qac = Qac _n-1 × (1-KV) + Qacn × KV
However, KV is a constant.
FIG. 7 is a calculation flow of the cylinder intake EGR amount (the EGR amount sucked into the cylinder), which is executed at a timing synchronized with the engine rotation.
[0023]
In step 31, the EGR amount Qe detected based on the signal from the EGR flow meter is read. Note that the EGR amount Qe may be obtained by appropriate prediction means.
In step 32, the engine speed Ne is read.
In step 33, the EGR amount Qe is converted into the EGR amount per intake Qecn by the following equation.
[0024]
Qecn = (Qe / Ne) × KC
However, KC is a constant.
In step 34, a delay process corresponding to the dynamics in the collector is performed by the following equation, whereby the cylinder intake EGR amount Qec is obtained, and the process ends.
Qec = Qec _n-1 × (1-KV) + Qecn × KV
However, KV is a constant.
[0025]
FIG. 8 shows a calculation flow of the maximum fuel injection amount, which is executed at a timing synchronized with the engine rotation. This flow corresponds to the maximum fuel injection amount calculating means.
In step 41, the engine speed Ne is read.
In step 42, a limit excess air ratio (rich limit) Klambn is set from the engine speed Ne with reference to a limit excess air ratio table at the time of no supercharging as shown in FIG.
[0026]
In step 43, the intake pressure Pm detected based on the signal from the intake pressure sensor is read.
In step 44, a limit excess air ratio pressure correction value Klambp is set from the intake pressure Pm with reference to a limit excess air ratio pressure correction value table as shown in FIG.
In step 45, the limiting excess air ratio Klambn is corrected by the pressure correction value Klambp to calculate the final limiting excess air ratio Klamb as in the following equation.
[0027]
Klamb = Klambn × Klambp
The table of FIG. 10 shows that when the air density increases as the intake pressure Pm increases, the penetration force of the fuel spray relatively weakens and the air utilization rate decreases, so that the limit excess air rate (rich limit) deteriorates. It is based on characteristics.
In step 46, the cylinder intake air amount Qac according to the flow of FIG. 6 is read.
[0028]
In step 47, the cylinder intake EGR amount Qec according to the flow of FIG. 7 is read.
In step 48, the maximum fuel injection amount Qful is calculated based on the cylinder intake air amount Qac, the cylinder intake EGR amount Qec, and the limit excess air ratio Klamb according to the following equation, and the process ends.
Qful = (Qac + Qec × KOR) / (Klamb × 14.7)
However, KOR is a constant.
[0029]
FIG. 11 is a flowchart for setting the fuel injection amount, which is executed at a timing synchronized with the engine rotation. This flow corresponds to the fuel injection amount setting means.
In step 51, the basic fuel injection amount Qsol1 according to the flow of FIG. 3 and the maximum fuel injection amount Qful according to the flow of FIG. 8 are read and compared.
As a result of the comparison, if Qsol1 <Qful, the routine proceeds to step 52, where Qsol1 is selected, the fuel injection amount Qsol is set to Qsol1, and the process is terminated.
[0030]
Conversely, if Qsol1 ≧ Qful, the routine proceeds to step 53, where Qful is selected, the fuel injection amount Qsol = Qful is set, and the process is terminated.
As described above, the smaller of the basic fuel injection amount Qsol1 and the maximum fuel injection amount Qful is determined as the final fuel injection amount Qsol. According to the final fuel injection amount Qsol, the fuel is injected into the engine by the fuel injection pump. Is controlled.
[0031]
FIG. 12 is a calculation flow of the basic target EGR rate, which is executed at a timing synchronized with the engine rotation. This flow corresponds to target EGR rate calculation means.
In step 61, the engine speed Ne is read.
In step 62, the basic fuel injection amount Mqdrv in the flow of FIG. 3 is read.
In step 63, the basic target EGR rate Megr is set based on the engine speed Ne and the basic fuel injection amount Mqdrv with reference to the basic target EGR rate map as shown in FIG.
[0032]
FIG. 14 is a calculation (correction) flow of the target EGR rate, which is executed at a timing synchronized with the engine rotation. This flow corresponds to target EGR rate correction means.
[0033]
In step 101, the basic fuel injection amount Mqdrv obtained from the engine speed Ne and the accelerator opening Cl in the flow of FIG. 3 is read.
In step 102, the final fuel injection amount Qsol according to the flow of FIG. 11 is read.
[0034]
In step 103, the correction rate Qfh of the fuel injection amount is calculated as the ratio of the final fuel injection amount Qsol to the basic fuel injection amount Mqdrv as in the following equation.
Qfh = Qsol / Mqdrv
In step 104, referring to the correction coefficient table shown in FIG. 15, the correction factor Qfh fuel injection amount, and sets the correction coefficient K. However, here, the correction coefficient K = the correction rate Qfh of the fuel injection amount.
[0035]
In step 105, the target EGR rate Tegr is calculated by multiplying the basic target EGR rate Megr by the flow of FIG. 12 by the correction coefficient K (= fuel injection amount correction rate Qfh) as in the following equation.
Tegr = Megr × K
In this way, the target EGR rate Tegr is corrected to decrease in accordance with the correction rate Qfh of the fuel injection amount, in other words, in accordance with the degree of restriction of the fuel injection amount.
[0036]
When the target EGR rate Tegr is set, the EGR amount is controlled by the EGR valve so as to obtain the target EGR rate Tegr.
Next, another embodiment of the present invention will be described.
FIG. 16 shows a second embodiment of the calculation (correction) flow of the target EGR rate, which is executed instead of the flow of FIG.
Steps 201 to 203 are the same as steps 101 to 103, and calculate the fuel injection amount correction rate Qfh = Qsol / Mqdrv as the ratio of the final fuel injection amount Qsol to the basic fuel injection amount Mqdrv.
[0037]
In step 204, the accelerator opening Cl is read.
In step 205, referring to the correction coefficient map shown in FIG. 17, a correction factor Qfh fuel injection amount, the accelerator opening Cl, sets the correction coefficient K.
Here, the correction coefficient K is set smaller so that the target EGR rate is corrected to decrease as the accelerator opening Cl increases.
[0038]
In step 206, the target EGR rate Tegr = Megr × K is calculated by multiplying the basic target EGR rate Megr by the correction coefficient K.
FIG. 18 shows a third embodiment of the calculation (correction) flow of the target EGR rate, which is executed instead of the flow of FIG.
Steps 301 to 303 are the same as steps 101 to 103, and calculate the fuel injection amount correction rate Qfh = Qsol / Mqdrv as the ratio of the final fuel injection amount Qsol to the basic fuel injection amount Mqdrv.
[0039]
In step 304, the accelerator opening Cl is read.
In step 305, the acceleration Acc is calculated as the amount of change in the accelerator opening by taking the difference from the accelerator opening L before as shown in the following equation.
Acc = Cl-Cl _nL
Here, L is a constant.
[0040]
In step 306, referring to the correction coefficient map shown in FIG. 19, a correction factor Qfh fuel injection quantity, from an acceleration Acc, it sets the correction coefficient K.
Here, the correction coefficient K is set small so that the target EGR rate is corrected to decrease as the acceleration Acc increases.
In step 307, the target EGR rate Tegr = Megr × K is calculated by multiplying the basic target EGR rate Megr by the correction coefficient K.
[0041]
FIG. 20 shows a fourth embodiment of the calculation (correction) flow of the target EGR rate, which is executed instead of the flow of FIG.
Basically, it corresponds to the flow of FIG. 18 , and only the steps 404 and 405 for detecting the acceleration Acc are different.
In step 404, the vehicle speed Vsp detected based on the signal from the vehicle speed sensor is read.
[0042]
In step 405, the acceleration Acc is calculated as the amount of change in the vehicle speed by calculating the difference from the vehicle speed L before as shown in the following equation.
Acc = Vsp−Vsp _nL
Here, L is a constant.
As described above, even when the acceleration is detected based on the change amount of the vehicle speed, the same operation and effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing the configuration of the present invention. FIG. 2 is a system diagram showing an embodiment of the present invention. FIG. 3 is a flowchart for calculating a basic fuel injection amount. FIG. 4 is a diagram showing a basic fuel injection amount map. FIG. 5 is a flowchart for detecting the intake air amount. FIG. 6 is a flowchart for calculating the cylinder intake air amount. FIG. 7 is a flowchart for calculating the cylinder intake EGR amount. FIG. 8 is a flowchart for calculating the maximum fuel injection amount. FIG. 10 is a diagram showing a rate table. FIG. 10 is a diagram showing a limit air excess ratio pressure correction value table. FIG. 11 is a flowchart for setting a fuel injection amount. FIG. 12 is a flowchart for calculating a basic target EGR ratio. FIG. 14 is a flowchart for calculating (correcting) a target EGR rate.
15 is a diagram showing a correction coefficient table
[16] calculation of the target EGR rate in the second embodiment (compensation) Flowchart
FIG. 17 is a diagram showing a correction coefficient map
[Figure 18] calculation of the target EGR rate in the third embodiment (compensation) Flowchart
FIG. 19 is a diagram showing a correction coefficient map
[Figure 20] calculation of the target EGR ratio of the fourth embodiment (correction) Flowchart [Description of symbols]
Reference Signs List 1 fuel injection pump 2 EGR valve 3 control unit 4 crank angle sensor 5 accelerator opening sensor 6 air flow meter 7 EGR flow meter 8 water temperature sensor 9 intake pressure sensor
10 Vehicle speed sensor

Claims (6)

Operating state detecting means for detecting an operating state of the engine including at least an engine speed, an accelerator opening, an intake air amount, and an EGR amount;
Basic fuel injection amount calculating means for calculating a basic fuel injection amount based on the engine speed and the accelerator opening,
Maximum fuel injection amount calculating means for calculating a maximum fuel injection amount allowed based on the intake air amount and the EGR amount;
A fuel injection amount setting means for comparing the basic fuel injection amount and the maximum fuel injection amount and setting a smaller one as a final fuel injection amount;
Fuel injection amount control means for controlling the fuel injection amount to the engine according to the final fuel injection amount;
Target EGR rate calculating means for calculating a target EGR rate based on the engine speed and the basic fuel injection amount;
Target EGR rate correction means for correcting the target EGR rate at least according to a ratio of the final fuel injection amount to the basic fuel injection amount;
EGR amount control means for controlling the EGR amount according to the target EGR rate;
A control device for an internal combustion engine, comprising: 2. The target EGR rate correction means according to claim 1, wherein the target EGR rate correction means corrects the target EGR rate in accordance with a ratio of a final fuel injection amount to a basic fuel injection amount and an accelerator opening. Control device for internal combustion engine. 2. The internal combustion engine according to claim 1, wherein said target EGR rate correction means corrects the target EGR rate in accordance with a ratio of a final fuel injection amount to a basic fuel injection amount and a degree of acceleration. Engine control device. 4. The control device for an internal combustion engine according to claim 3, wherein the degree of acceleration is detected based on a change amount of an accelerator opening. 4. The control device for an internal combustion engine according to claim 3, wherein the degree of acceleration is detected based on an amount of change in vehicle speed. The maximum fuel injection amount calculating means calculates the maximum fuel injection amount Qful assuming that the amount of air taken into the cylinder is Qac, the amount of EGR is Qec, and the excess excess air ratio is Klamb.
Qful = (Qac + Qec × KOR) / (Klamb × 14.7)
6. The control apparatus for an internal combustion engine according to claim 1 , wherein KOR is calculated by using a constant.

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