JP3740878B2 - Engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine control device.
[0002]
[Prior art]
When accelerating in the lean air-fuel ratio (air-fuel ratio leaner than the stoichiometric air-fuel ratio), if the air-fuel ratio is shifted to the rich side to increase the engine output, the amount of NOx generated increases significantly. There is a system in which the engine output is increased without increasing the amount of NOx generated at the time of acceleration in the lean air-fuel ratio operation region by performing supercharging without changing the fuel ratio (see JP-A-7-158462). ).
[0003]
[Problems to be solved by the invention]
By the way, at the same level of acceleration in the stoichiometric air-fuel ratio operating range, there is no need for the boost pressure change to increase as in the acceleration in the lean air-fuel ratio operating range, and the intake air amount rises quickly, thereby increasing the torque. Although the responsiveness is improved, the rise of the intake air amount is delayed due to the response delay of the boost pressure when accelerating in the lean air fuel ratio operation range where the boost pressure change becomes large. The torque rises differently from the acceleration at the same level.
[0004]
As described above, even when acceleration is performed at the same level, if the rising of the torque differs depending on the setting of the air-fuel ratio, a sense of incongruity occurs in the drivability.
[0005]
Therefore, when accelerating in the lean air-fuel ratio operating range, the value obtained by increasing the target intake air amount according to the deviation of the actual boost pressure from the target boost pressure is calculated as the second target intake air amount. By controlling the throttle valve opening so that the second target intake air amount is introduced into the engine, even when accelerating in the lean air-fuel ratio operating range, It is conceivable to obtain the same torque rise (see Japanese Patent Application No. 10-305870).
[0006]
  In this case, if the actual supercharging pressure is detected by the sensor, even when there is a change in the atmospheric pressure due to an altitude change or a difference in the actual supercharging pressure due to individual engine differences, the state of the reference atmospheric pressure (for example, standard atmospheric pressure)The engine when there is no individual engine difference (the engine when there is no individual engine difference,Standard engine" )The air amount increase correction at the time of acceleration in the same lean air-fuel ratio operation region as in the state of is performed.
[0007]
However, even if the air amount is corrected to increase, the air amount cannot be increased beyond the fully open position of the throttle valve. Therefore, in the lean air-fuel ratio operating region and high altitude (land with atmospheric pressure lower than the reference atmospheric pressure) When accelerating in a high load region or in a deteriorated engine (an engine whose supercharging pressure is lower than the standard engine) in a lean air-fuel ratio operating range and low altitude (land where the reference atmospheric pressure is obtained) Even if the accelerator pedal is stepped on, the torque cannot be increased, and the driving performance is uncomfortable.
[0008]
This will be further explained. If the engine speed and the accelerator operation amount are constant and the low altitude is low, the actual supercharging pressure is increased to 200 mmHg. If the altitude is high, the actual supercharging pressure is only increased to 150 mmHg. (However, these values are relative pressures where the reference atmospheric pressure is 0 mmHg). At this time, the control unit also sets the second target intake air amount to the value obtained by correcting the target intake air amount to be increased according to the deviation of the actual boost pressure from the target boost pressure during acceleration in the lean air-fuel ratio operation range. And the throttle valve opening is controlled so that the second target intake air amount is introduced into the engine. Similarly, if the engine speed and the amount of accelerator operation are constant and the standard engine is used, the actual boost pressure will increase to 200 mmHg in the lowland. If the engine becomes a deteriorated engine, the actual boost pressure will only increase to 150 mmHg. Suppose that it did not rise. At this time, the control unit also sets the second target intake air amount to the value obtained by correcting the target intake air amount to be increased according to the deviation of the actual boost pressure from the target boost pressure during acceleration in the lean air-fuel ratio operation range. And the throttle valve opening is controlled so that the second target intake air amount is introduced into the engine. In other words, if the actual supercharging pressure is reduced by 50 mmHg due to the atmospheric pressure change due to the altitude change or the actual supercharging pressure due to the individual engine difference, the increase correction value of the air amount correspondingly increases. When the 2 target intake air amount exceeds the air amount when the throttle valve is fully opened, the entire second target intake air amount cannot be introduced into the engine, resulting in a shortage of the intake air amount. Even if the driver feels that the torque is insufficient due to this air amount shortage and depresses the accelerator pedal, the torque cannot be increased.
[0009]
Therefore, the present invention provides the actual supercharging pressure when the standard engine is used under the reference atmospheric pressure as an estimated value (calculated value) that does not depend on the atmospheric pressure change due to the altitude change or the individual engine difference, and the reference atmospheric pressure. A value obtained by correcting the target intake air amount according to the deviation of the estimated value of the actual boost pressure from the engine is calculated as the second target intake air amount, and the throttle valve is introduced so that the second target intake air amount is introduced into the engine. A sensor that detects the air flow meter upstream pressure (atmospheric pressure) is added by controlling the opening or when the actual supercharging pressure is detected by a sensor. Accordingly, the target supercharging pressure is corrected to decrease, and the operation of lean air-fuel ratio is calculated by calculating the supercharging pressure correction value according to the deviation of the actual supercharging pressure detection value from the target boost pressure corrected by this decrease. Acceleration in high load areas at high altitudes During the acceleration at or lean air-fuel ratio operating region and degradation engine, and to prevent the uncomfortable feeling of the driver due to not expected increase torque even further depresses the accelerator pedal.
[0010]
[Means for Solving the Problems]
As shown in FIG. 23, the first invention is a device 31 that can control the opening of a throttle valve regardless of the accelerator pedal, and a means 32 for calculating a target equivalent ratio tDML that provides a lean air-fuel ratio in a predetermined operating range. A means 33 for calculating the target fuel amount by correcting the fuel amount at which the theoretical air-fuel ratio is obtained by the target equivalent ratio tDML, a means 34 for supplying the target fuel amount to the engine, and a target intake at the stoichiometric air-fuel ratio Means 35 for calculating the air amount as a reference target intake air amount; means 36 for calculating a value obtained by dividing the reference target intake air amount by the target equivalent ratio tDML as the target intake air amount tTP; and the operation of the lean air-fuel ratio. And a means for calculating an actual supercharging pressure estimated value Pcr when the standard engine is used under a reference atmospheric pressure (for example, standard atmospheric pressure). 8 and means 39 for calculating a supercharging pressure correction value ηp according to the difference between the reference atmospheric pressure and the actual supercharging pressure estimated value Pcr during acceleration in the lean air-fuel ratio operation range, and the supercharging pressure A means 40 for calculating a value obtained by increasing the target intake air amount tTP with the correction value ηp as a second target intake air amount tTP ′, and the throttle so that the second target intake air amount tTP ′ is introduced into the engine. A means 41 for driving the valve control device 31 is provided.
[0011]
In the second invention, in the first invention, the change in the actual boost pressure estimated value Pcr at the time of acceleration is approximated by a dead time and a primary delay.
[0012]
In the third invention, in the first invention, the change in the actual boost pressure estimated value Pcr at the time of acceleration is approximated by a dead time and a first-order lag, and the decrease is corrected during the dead time.
[0013]
According to a fourth aspect, in the third aspect, the amount of reduction correction is a value corresponding to the amount of change per predetermined time in the accelerator operation amount during acceleration.
[0014]
In a fifth aspect of the invention, in the third aspect of the invention, the amount of reduction correction is a value corresponding to the engine load and the engine speed.
[0015]
According to a sixth aspect, in the first aspect, the change in the actual boost pressure estimated value Pcr at the time of acceleration is approximated by a dead time and a ramp response.
[0016]
According to a seventh aspect, in the sixth aspect, the amount of change in the ramp response per predetermined time is set according to the engine load and the engine speed.
[0017]
As shown in FIG. 24, the eighth invention includes a device 31 that can control the opening degree of the throttle valve regardless of the accelerator pedal, and means 32 for calculating a target equivalent ratio tDML that provides a lean air-fuel ratio in a predetermined operating range. A means 33 for calculating the target fuel amount by correcting the fuel amount at which the theoretical air-fuel ratio is obtained by the target equivalent ratio tDML, a means 34 for supplying the target fuel amount to the engine, and a target intake at the stoichiometric air-fuel ratio Means 35 for calculating the air amount as a reference target intake air amount; means 36 for calculating a value obtained by dividing the reference target intake air amount by the target equivalent ratio tDML as the target intake air amount tTP; and the operation of the lean air-fuel ratio. For calculating the target supercharging pressure Pcm when the standard engine is used under the reference atmospheric pressure (for example, standard atmospheric pressure). 51, means 52 for detecting the atmospheric pressure, means 53 for reducing the target supercharging pressure Pcm in accordance with the difference between the reference atmospheric pressure and the detected value of the atmospheric pressure, and means 54 for detecting the actual supercharging pressure. And a means 55 for calculating a boost pressure correction value ηp according to the difference between the target boost pressure Pcm corrected for decrease and the actual boost pressure detection value PCR during acceleration in the lean air-fuel ratio operating range; The means 40 for calculating a value obtained by correcting the target intake air amount tTP by the boost pressure correction value ηp as the second target intake air amount tTP ′, and the second target intake air amount tTP ′ are introduced into the engine. A means 41 for driving the throttle valve control device 31 is provided.
[0018]
【The invention's effect】
When the area where the turbocharger is operated overlaps with the lean air-fuel ratio operating range, when accelerating in the lean air-fuel ratio operating range, the actual boost pressure exceeds the target boost pressure due to a delay in the boost pressure response. At this time, according to the first aspect of the invention, the second target intake air amount that is larger than the target intake air amount due to the boost pressure correction value is introduced into the engine. Torque drop due to insufficient air volume due to pressure response delay can be avoided. In other words, even when accelerating in the lean air-fuel ratio operating range, it is possible to achieve the same pattern of torque changes as in accelerating in the stoichiometric air-fuel ratio operating range, so the difference in drivability due to different set air-fuel ratios can be eliminated. .
[0019]
In this case, the actual boost pressure is detected by the sensor, and the boost pressure correction value is calculated according to the deviation of the actual boost pressure detection value from the target boost pressure. The boost pressure correction value becomes larger than that in the lowland area, or even in the lowland area when the engine is deteriorated, the boost pressure correction value becomes larger than that in the standard engine, thereby correcting the throttle valve opening to the larger side. (That is, the throttle valve opening depends on atmospheric pressure changes due to altitude changes and individual engine differences.) However, even if the air amount is corrected to increase, the air amount cannot be increased beyond the fully open position of the throttle valve. The torque can be increased even if the accelerator pedal is stepped on when accelerating in an air-fuel ratio operating range and high load range in high altitude, or in a lean air-fuel ratio operating range and accelerating with a deteriorated engine. However, in the first aspect of the invention, the actual boost pressure estimated value is a calculated value that does not depend on atmospheric pressure changes due to altitude changes or individual engine differences. The boost pressure correction value of the same value as that of the lowland is calculated even when the altitude is high, or the boost pressure correction value of the same value as that of the standard engine is calculated even when the engine is deteriorated. There is nothing. According to the first aspect of the present invention, if the accelerator pedal is stepped on at the time of acceleration in a lean air-fuel ratio operating range and at a high load region in a high altitude, or at a lean air-fuel ratio operating range and acceleration in a deteriorated engine, the amount of increase Accordingly, the torque can be increased.
[0020]
According to the second invention, it is possible to accurately approximate the change of the actual supercharging pressure during acceleration.
[0021]
According to the third aspect of the invention, it is possible to accurately approximate the change in the actual boost pressure at the initial stage of acceleration.
[0022]
According to the fourth aspect of the invention, it is possible to accurately approximate the initial change in the actual boost pressure in accordance with the movement of the accelerator operation amount.
[0023]
According to the fifth aspect of the invention, it is possible to accurately approximate the initial change in the actual boost pressure regardless of the engine load and the rotational speed.
[0024]
According to the sixth aspect, the calculation load and the ROM capacity when calculating the actual supercharging pressure estimated value can be reduced.
[0025]
According to the seventh aspect, it is possible to easily approximate a change in acceleration of the actual supercharging pressure regardless of the engine load and the rotational speed.
[0026]
In the eighth invention, when the actual supercharging pressure detection value decreases due to atmospheric pressure change due to altitude change or individual engine differences, the target supercharging pressure is reduced by the atmospheric pressure correction value corresponding to this decrease, and thereby Even if there is a difference in the actual supercharging pressure detection value due to changes in atmospheric pressure or individual engine differences, the supercharging pressure correction value will be the same, so when accelerating or leaning in a lean air-fuel ratio operating region and high load region If the accelerator pedal is stepped on at the time of acceleration in the air-fuel ratio operating range and the deteriorated engine, the torque can be increased in accordance with the stepped-up amount.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, 1 is an engine body, 2 is an intake passage, 3 is an exhaust passage, 4 is a fuel injection valve provided directly facing the combustion chamber 5, 6 is a spark plug, 7 is a throttle valve, and 8 is this throttle valve. 7 is a throttle valve control device that electronically controls the opening degree of 7.
[0028]
The engine includes a turbocharger 11. The turbocharger 11 is formed by connecting a compressor 12 that compresses intake air and a turbine 13 that absorbs a driving force of the compressor 12 from exhaust energy through a coaxial 14. In order to prevent the supercharging pressure from exceeding the set pressure, a waste gate valve 15 is provided to allow exhaust at the inlet of the turbine 13 to flow bypassing the turbine 13.
[0029]
The accelerator operation amount (accelerator pedal depression amount) from the accelerator sensor 22, the position signal for each unit crank angle from the crank angle sensor 23, and the signal from the reference position signal are the intake air flow rate from the air flow meter 24, Each signal of the cooling water temperature from the water temperature sensor 25 is input to the control unit 21. The control unit 21 controls the fuel injection (air-fuel ratio) via the fuel injection valve 4 and the throttle via the throttle valve control device 8. The opening degree of the valve 7 is controlled.
[0030]
Here, the outline of the control contents of the fuel injection will be described. The fuel injection valve 4 injects fuel in the latter half of the compression stroke at a low load or the like. A combustible air-fuel mixture is formed in a nearby cavity, and the fuel is stratified by combustion with ignition by the spark plug 6, and as a whole, ultra lean combustion with an air-fuel ratio exceeding 40 is performed. Further, in the high load region, fuel is injected in the intake stroke, mixing of fuel and air is accelerated, the entire combustion chamber 5 is filled with a homogeneous mixture, and homogeneous combustion is performed with the mixture near the stoichiometric air-fuel ratio. Further, in the intermediate load region between the stratified combustion region and the homogeneous combustion region, lean combustion is performed which is richer in air-fuel ratio than stratified combustion but thinner than the stoichiometric air-fuel ratio.
[0031]
As described above, there are three regions with greatly different air-fuel ratios as control regions, and the combustion state in each region is referred to as stratified combustion, homogeneous lean combustion, and homogeneous stoichiometric combustion from the side with the larger air-fuel ratio (lean side). .
[0032]
Now, when the supercharging region is overlapped with a part of the homogeneous lean combustion zone (see Fig. 9), the acceleration of the supercharging pressure is delayed during acceleration in the homogeneous lean combustion zone where the supercharging pressure changes greatly. Since the rise of the intake air amount is delayed, the rise of the torque is different from that at the same level of acceleration in the homogeneous stoichiometric combustion region.
[0033]
In order to cope with this, a value obtained by correcting the target intake air amount to be increased according to the deviation of the actual boost pressure from the target boost pressure during acceleration in the lean air-fuel ratio operation range is used as the second target intake air amount. By calculating and controlling the throttle valve opening so that the second target intake air amount is introduced into the engine, even when accelerating in the lean air-fuel ratio operating range, the same level in the stoichiometric air-fuel ratio operating range It is conceivable to obtain the same torque rise as that during acceleration.
[0034]
In this case, if the actual supercharging pressure is detected by the sensor, the standard atmospheric pressure state (reference atmospheric pressure state) and the standard An air amount increase correction at the time of acceleration in the same lean air-fuel ratio operation region as in the engine state is performed.
[0035]
However, even if the air amount is corrected to be increased, the air amount cannot be increased beyond the fully open position of the throttle valve. Therefore, when accelerating in a lean air-fuel ratio operation region and in a high load region at high altitude, or operating at a lean air-fuel ratio. When accelerating with a high-frequency and deteriorated engine, even if the accelerator pedal is stepped on, the torque cannot be increased and the driving performance may be uncomfortable. A value obtained by correcting the target intake air amount according to the deviation of the actual boost pressure estimated value from the standard atmospheric pressure, giving the estimated boost pressure as a calculated value that does not depend on changes in atmospheric pressure due to altitude changes or individual engine differences. Is calculated as the second target intake air amount, and the throttle valve opening is controlled so that the second target intake air amount is introduced into the engine.
[0036]
The contents of this control executed by the control unit 21 will be described according to the following flowchart.
[0037]
First, FIG. 2 is for calculating the target opening tTPS of the throttle valve, and is executed at regular intervals (for example, every 4 ms).
[0038]
The basic part of calculating the target opening of the throttle valve based on the accelerator operation amount and the engine speed has already been disclosed in the prior application device (Japanese Patent Application No. 9-38773).
[0039]
In step 1, the intake air amount requested by the driver (driver) is calculated based on the accelerator operation amount APS and the engine speed Ne. Specifically, driver-requested intake air amount data (see FIG. 3) obtained experimentally in advance is stored as a map using the accelerator operation amount APS and the engine speed Ne as parameters, and the map is used. It may be a method of searching.
[0040]
In step 2, the intake air amount necessary for stabilizing the idling rotation is calculated, and the intake air amount necessary for stabilizing the idle is added to the driver required intake air amount in step 3, and the added value is obtained. Is the reference target intake air amount.
[0041]
The reference target intake air amount obtained in this way is the intake air amount at which a target torque corresponding to the accelerator operation amount and the engine speed is obtained in the homogeneous stoichiometric combustion region.
[0042]
As the reference target intake air amount, in this embodiment, the basic injection pulse width at the time of homogeneous stoichiometric combustion corresponding to the intake air amount for each intake stroke is used, but the intake air amount itself for each intake stroke itself, unit time Either the intake air amount for each, or the fuel amount at the time of homogeneous stoichiometric combustion corresponding to these intake air amounts may be used.
[0043]
In step 4, the reference target intake air amount is corrected with a target equivalent ratio tDML (a method of obtaining the reference target air amount will be described later with reference to FIG. 15) and a fuel consumption rate correction coefficient FCrate to calculate a target intake air amount tTP. In particular
[0044]
[Expression 1]
tTP = (reference target intake air amount / tDML) × FCrate
The target intake air amount tTP is calculated by the following formula.
[0045]
As a result, the target intake air amount tTP is the target equivalent ratio tDML (that is, the target air-fuel ratio), and the intake air amount at which a target torque corresponding to the accelerator operation amount and the engine speed is obtained.
[0046]
As shown in FIG. 4, the fuel efficiency correction coefficient FCrate of Equation 1 is a value that becomes smaller than 1.0 as the target equivalent ratio tDML becomes smaller than 1.0 (that is, the leaner the theoretical air-fuel ratio). It is. The reason why the target intake air amount tTP is corrected to decrease as the value becomes leaner according to the equation (1) is because the fuel efficiency improves as the value becomes leaner, and thus the target intake air amount may be smaller.
[0047]
In step 5, a value obtained by correcting the target intake air amount tTP by increasing in accordance with the deviation of the actual supercharging pressure from the standard atmospheric pressure is calculated as the second target intake air amount tTP ′. The calculation of the second target intake air amount tTP ′ will be described with reference to FIG.
[0048]
The flowchart in FIG. 7 is a subroutine of step 5 in FIG. 2, which is also executed at regular intervals.
[0049]
In step 11, an actual boost pressure estimated value is calculated. This calculation will be described with reference to FIG. The flowchart in FIG. 8 is a subroutine of step 11 in FIG. 7 and is executed at regular intervals.
[0050]
In step 21, a reference supercharging pressure is obtained by searching a map for each preset combustion state from the reference target intake air amount as the engine load and the engine speed.
[0051]
Here, the reference supercharging pressure is a supercharging pressure in an equilibrium state obtained when a standard engine is used under a standard atmospheric pressure (760 mmHg). Moreover, there are three combustion states, stratified combustion, homogeneous lean combustion, and homogeneous stoichiometric combustion, and as shown in FIG. 9, which combustion state is determined in advance according to the operating conditions. Since the actual supercharging pressure differs depending on the combustion state, a map of the reference supercharging pressure is provided corresponding to each combustion state, and therefore, the reference supercharging pressure corresponding to each combustion state is obtained. Note that the general characteristics of the reference boost pressure common to all combustion states are as shown in FIG. 10 (the larger the reference target intake air amount and the higher the engine speed, the greater the value).
[0052]
Now, when the change in acceleration of the actual supercharging pressure is modeled in the upper part of FIG. 12, the reference supercharging pressure Pch changes stepwise, whereas the actual supercharging pressure is delayed by a primary delay after the dead time due to the turbo lag. To increase. In addition, during acceleration, the actual supercharging pressure is lower than before the step change during the dead time. Therefore, in order to approximate such a change in acceleration of the actual supercharging pressure, a reduction correction according to the amount of change in the accelerator operation amount APS per predetermined time is performed during the dead time, and after the dead time, the reference supercharging pressure is corrected. Find the weighted average of.
[0053]
Specifically, it is determined in step 22 in FIG. 8 which combustion state is the current combustion state shown in FIG. 9. If the current combustion state is stratified combustion, the process proceeds to steps 23 and 24, and stratification is performed. The reference supercharging pressure Pch1 for combustion is set to Pch, and the weighted average coefficient Kr1 for stratified combustion is set to Kr. Similarly, when the current combustion state is homogeneous lean combustion, the routine proceeds to steps 25 and 26, where the reference boost pressure Pch2 for homogeneous lean combustion is set to Pch, the weighted average coefficient Kr2 for homogeneous lean combustion is set to Kr, and When the current combustion state is homogeneous stoichiometric combustion, the routine proceeds to steps 27 and 28, where the reference supercharging pressure Pch3 for homogeneous stoichiometric combustion is set to Pch, and the weighted average coefficient Kr3 for homogeneous stoichiometric combustion is entered to Kr.
[0054]
The weighted average coefficients Kr1, Kr2, and Kr3 define the degree of rise of the actual supercharging pressure after the dead time in the upper part of FIG. 12, and the approximate characteristics of the weighted average coefficients common to all combustion states are as follows: It becomes what was shown in FIG.
[0055]
In step 29 of FIG. 8, using the reference supercharging pressure Pch and the weighted average coefficient Kr thus obtained,
[0056]
[Expression 2]
Pcr0 = Kr × Pch + (1−Kr) × Pcr0_-1
However, Pcr0_-1: Previous value of Pcr0
The weighted average value Pcr0 of the reference supercharging pressure is obtained by the following equation, and dead time compensation is performed in step 40. For example, compensation for dead time during acceleration is as follows:
[0057]
[Equation 3]
Pcr = Pcr0−ΔAPS × K
Where K is a positive constant
The dead time compensation is performed using the following equation, and the value after the dead time compensation is set as the actual boost pressure estimated value Pcr (see the broken line in the upper part of FIG. 12).
[0058]
Here, ΔAPS in the second term on the right side of Equation 3 is the amount of change in the accelerator operation amount APS per predetermined time, and ΔAPS is positive at the time of acceleration. The supercharging pressure becomes smaller than the value just before acceleration. The reason why the pressure drop immediately after acceleration (the second term on the right side of Equation 3) is made to depend on ΔAPS is that, as ΔAPS (that is, the change rate of the throttle opening) increases, the pressure drop within the dead time increases. Because it becomes. Needless to say, the weight reduction correction based on the second item of Equation 3 is performed only within a predetermined dead time.
[0059]
On the other hand, during deceleration, normal dead time compensation is performed as shown in the lower part of FIG. 12 (see the broken line in the lower part of FIG. 12).
[0060]
The constant K in the second term of Equation 3 may be a constant value, but may be set as a variable value according to the engine load and the number of revolutions as shown in FIG. According to FIG. 13, even when ΔAPS is the same, the pressure drop is larger in the low load low rotation range than in the high load high rotation range.
[0061]
Now that the actual boost pressure estimated value Pcr has been obtained, the process returns to FIG. In step 12
[0062]
[Expression 4]
ηp = Pcr / standard atmospheric pressure
The boost pressure correction value ηp is calculated by the following equation, and a value obtained by multiplying the correction value ηp by the target intake air amount tTP in step 13 is obtained as a second target intake air amount tTP ′ (= ηp × tTP). Since the actual supercharging pressure estimated value Pcr is generated based on the reference supercharging pressure Pch, it always becomes a value equal to or higher than the standard atmospheric pressure at high altitudes, and the supercharging pressure correction value ηp is 1 according to Equation 4 when accelerating in the homogeneous lean combustion region. A value greater than or equal to 0. Accordingly, the value obtained by correcting the target intake air amount tTP by the correction value ηp is the second target intake air amount tTP ′ (see FIG. 14).
[0063]
When the second target intake air amount tTP ′ is obtained in this way, the process returns to FIG. In step 6, the target opening area of the throttle valve is calculated based on the second target intake air amount tTP ′, and the target opening degree tTPS of the throttle valve is calculated in step 7 according to the target opening area. Specifically, a map having the contents shown in FIG. 5 is searched from the second target intake air amount tTP ′ and the engine speed to obtain the target opening area of the throttle valve, and the table having the contents shown in FIG. 6 is obtained from the target opening area. To obtain the target opening tTPS of the throttle valve.
[0064]
The signal of the target opening tTPS is input to the above-described throttle valve control device 8, which causes the throttle valve control device 8 to turn the throttle valve 7 so that the actual opening TPS of the throttle valve 7 matches the target opening tTPS. To drive.
[0065]
Next, FIG. 15 is for calculating the target equivalent ratio tDML, and is executed at regular intervals independently of the above FIG.
[0066]
In step 41, based on the reference target intake air amount as the engine load and the engine speed, the reference target equivalent ratio tDML0 is calculated in consideration of the coolant temperature. Specifically, a map having the contents shown in FIG. 16 may be obtained from the reference target intake air amount and the engine speed. In FIG. 16, different numerical values are entered for each of the three combustion states shown in FIG. For example, the homogeneous stoichiometric combustion region has a value of 1.0, the homogeneous lean combustion region has a value of about 0.7 to 0.8, and the stratified combustion region has a small positive value less than this.
[0067]
In step 42, correction is made so that the phase of the equivalence ratio matches the phase of the actually inhaled air. If this phase correction is treated as a first order lag,
[0068]
[Equation 5]
tDML = Kt × tDML0 + (1-Kt) × tDML_-1
Where Kt: weighted average coefficient
tDML_-1: Previous value of tDML
The target equivalent ratio tDML may be calculated by the following formula.
[0069]
The weighted average coefficient Kt in Expression 5 is obtained, for example, by searching a map having the contents shown in FIG. 17 from the reference target intake air amount and the engine speed.
[0070]
In the flowchart (not shown) using the target equivalent ratio tDML thus obtained,
[0071]
[Formula 6]
TI = TP × tDML × 2 + TS
Where TP: basic injection pulse width,
TS: Invalid injection pulse width
From this equation, the fuel injection pulse width TI at the time of sequential injection is calculated as in the conventional case.
[0072]
The TP in Equation 6 is a value obtained by multiplying the intake air flow rate Qa detected by the air flow meter 24 by the engine speed Ne and a constant, and this TP provides a substantially stoichiometric air-fuel mixture. TS is a value for compensating for a decrease in the fuel injection pulse width due to a decrease in battery voltage.
[0073]
When an injection signal having this TI is output to the fuel injection valve 4, fuel is injected from the injection valve 4 once in two engine revolutions in accordance with the ignition sequence.
[0074]
As described above, in the present embodiment, at the time of acceleration in the homogeneous lean combustion region, the boost pressure correction value ηp becomes a value of 1.0 or more, and the second target intake air amount tTP ′ is larger than the target intake air amount tTP. As a result (see FIG. 14), the throttle valve target opening tTPS calculated based on the second target intake air amount tTP ′ is larger than the throttle valve opening tTPS calculated based on the target intake air amount tTP. Thus, even when the supercharging pressure is not developed, the second target intake air amount tTP ′ that is the target intake air amount can be introduced, and the torque drop due to the shortage of the air amount due to the response delay of the supercharging pressure. Can be avoided.
[0075]
In this case, the actual boost pressure is detected by the sensor, and the boost pressure correction value is calculated according to the deviation of the actual boost pressure detection value from the target boost pressure. The supercharging pressure correction value ηp is larger than that in the lowland, or even in the lowland, the supercharging pressure correction value ηp is larger than that in the standard engine, and the throttle valve opening is corrected accordingly. (In other words, the throttle opening depends on atmospheric pressure and individual engine differences) However, even if the air amount is corrected to be increased, the air amount cannot be increased beyond the fully open position of the throttle valve. Even when the accelerator pedal is depressed, the torque cannot be increased during acceleration in a high load range in a high range or in a high altitude region, or in a driving range with a lean air-fuel ratio and acceleration with a deteriorated engine. May give an uncomfortable feeling.
[0076]
On the other hand, in this embodiment, since the actual supercharging pressure estimated value Pcr is a calculated value that does not depend on atmospheric pressure changes due to altitude changes or individual engine differences, the supercharging pressure that is the same value as the lowland even when the altitude is high. Even if the correction value is calculated or the engine is deteriorated, the boost pressure correction value of the same value as that of the standard engine is calculated. According to the present embodiment, if the accelerator pedal is stepped on at the time of acceleration in the lean air-fuel ratio driving range and high load region in the high altitude, or at the lean air-fuel ratio driving range and acceleration with the deteriorated engine, the stepping-on amount is increased. Accordingly, the torque can be increased.
[0077]
The waveform diagram of FIG. 18 is the second embodiment and corresponds to FIG. 12 of the first embodiment. In the first embodiment, the change in acceleration of the actual boost pressure is approximated by a dead time and a first-order lag, but in the second embodiment, the change in acceleration of the actual boost pressure is approximated by a dead time and a ramp response. It is what I did.
[0078]
According to the second embodiment, although the calculation accuracy at the time of acceleration of the actual boost pressure estimated value is slightly lower than that of the first embodiment, the calculation load and ROM capacity can be made smaller than those of the first embodiment.
[0079]
Note that the amount of change per predetermined time in ramp response (increase during acceleration and decrease during deceleration) may be a constant value, but it is set as a variable according to the engine load and speed as shown in FIG. It doesn't matter. According to FIG. 19, the amount of change per predetermined time is larger in the high load high rotation range than in the low load low rotation range.
[0080]
The flowcharts of FIGS. 20 and 21 are the third embodiment, which replaces FIGS. 7 and 8 of the first embodiment. In FIG. 20, the same steps as those in FIG. 7 are denoted by the same step numbers.
[0081]
In the third embodiment, when the actual supercharging pressure is detected by a sensor, a sensor for detecting the upstream pressure (atmospheric pressure) of the air flow meter is added, and the target is set according to the deviation of the detected atmospheric pressure from the standard atmospheric pressure. The actual boost pressure is detected by the sensor by correcting the decrease in the boost pressure and calculating the boost pressure correction value according to the deviation of the actual boost pressure detection value from the target boost pressure corrected by this decrease. Even if the accelerator pedal is stepped on when accelerating in a lean air-fuel ratio operating range and high load range in high altitude, or in a lean air-fuel ratio operating range and accelerating with a deteriorated engine, The torque can be increased.
[0082]
Specifically, in step 51 of FIG. 20, the target boost pressure Pcm is calculated for each combustion state based on the accelerator operation amount APS and the engine speed Ne.
[0083]
The calculation of the target supercharging pressure Pcm will be described with reference to FIG. FIG. 21 is a subroutine of step 51 in FIG. 20, which is executed at regular intervals.
[0084]
In FIG. 21, in step 61, as in step 31 of FIG. 8, a map for each preset combustion state is retrieved from the reference target intake air amount as the engine load and the engine speed, and the reference boost pressure is obtained. Ask for.
[0085]
In steps 62, 63, and 64, phase correction is performed by obtaining a weighted average value of each reference supercharging pressure. Specifically, if the reference supercharging pressures for stratified combustion, homogeneous lean combustion, and homogeneous stoichiometric combustion are Pch1, Pch2, and Pch3,
[0086]
[Expression 7]
Pcm1 = Kp1 × Pch1 + (1−Kp1) × Pcm1_-1
Pcm2 = Kp2 * Pch2 + (1-Kp2) * Pcm2_-1
Pcm3 = Kp3 × Pch3 + (1-Kp3) × Pcm3_-1
However, Kp1: Weighted average coefficient in stratified combustion
Kp2: Weighted average coefficient in homogeneous lean combustion
Kp3: Weighted average coefficient in homogeneous stoichiometric combustion
Pcm1_-1: Previous value of Pcm1
Pcm2_-1: Previous value of Pcm2
Pcm3_-1: Previous value of Pcm3
The weighted average values Pcm1, Pcm2, and Pcm3 of the three reference supercharging pressures can be obtained by the following equation.
[0087]
The weighted average coefficients Kp1, Kp2, and Kp3 in Equation 7 define the degree of rise of the target boost pressure in the second stage of FIG. 22, and the approximate characteristics of the weighted average coefficients common to all combustion states are as follows. This is the same as that shown in FIG.
[0088]
In step 65, it is determined in which combustion region shown in FIG. 9 the operating point determined from the reference target intake air amount and the engine speed is. If the current operating point is in the stratified combustion region, the process proceeds to step 66. , Pcm1 is set to the target supercharging pressure Pcm0. Similarly, when the current operating point is in the homogeneous lean combustion region, the routine proceeds to step 67 and Pcm2 is set to the target supercharging pressure Pcm0, and when the current operating point is in the homogeneous stoichiometric combustion region, the routine proceeds to step 68. To set Pcm3 to the target supercharging pressure Pcm0.
[0089]
In step 69, from the atmospheric pressure (absolute pressure) detected by the sensor.
[0090]
[Equation 8]
Atmospheric pressure correction value = Atmospheric pressure sensor value / Standard atmospheric pressure
The atmospheric pressure correction value is calculated by the following equation, and a value obtained by multiplying the correction value by the target supercharging pressure Pcm0 in step 70 is calculated as the target supercharging pressure Pcm.
[0091]
Here, since the atmospheric pressure sensor value is lower than the standard atmospheric pressure at high altitude, the atmospheric pressure correction value is always a positive value of 1 or lower at high altitude.
[0092]
When the target boost pressure Pcm is calculated in this way, the process returns to FIG. 20, and the actual boost pressure detection value PCR detected by the sensor is read in step 52.
[0093]
[Equation 9]
ηp = Pcm / PCR
The boost pressure correction value ηp is calculated by the following formula.
[0094]
As described above, when the actual boost pressure is detected by the sensor and the boost pressure correction value is calculated according to the deviation of the actual boost pressure detection value from the target boost pressure, the throttle valve opening is at atmospheric pressure. Depending on changes and individual engine differences, the throttle valve opening is corrected to become larger during acceleration at lean air-fuel ratio operation. In the third embodiment, the actual boost pressure detection value is large. When the pressure drops due to atmospheric pressure changes or individual engine differences, the target supercharging pressure is corrected by reducing the atmospheric pressure correction value corresponding to this decrease. The boost pressure correction value will be the same even if there is an engine. If you do It is possible to increase the torque in response to minute.
[0095]
In the embodiment, the acceleration in the homogeneous lean combustion region when the supercharging region is part of the homogeneous lean combustion region has been described. However, the acceleration in the homogeneous lean combustion region when the supercharging region is present in the entire homogeneous lean combustion region. In addition, the present invention can also be applied to acceleration in a stratified combustion region when a supercharging region is present in part or all of the stratified combustion region.
[0096]
In the embodiment, the case where the standard atmospheric pressure is used as the reference atmospheric pressure has been described, but the present invention is not limited to this.
[Brief description of the drawings]
FIG. 1 is a control system diagram of one embodiment.
FIG. 2 is a flowchart for explaining calculation of a throttle valve target opening.
FIG. 3 is a characteristic diagram of a driver required intake air amount.
FIG. 4 is a characteristic diagram of a fuel efficiency correction coefficient.
FIG. 5 is a characteristic diagram of a target opening area of a throttle valve.
FIG. 6 is a characteristic diagram of a throttle valve target opening.
FIG. 7 is a flowchart for explaining calculation of a second target intake air amount.
FIG. 8 is a flowchart for explaining calculation of actual supercharging pressure.
FIG. 9 is a region diagram in a combustion state.
FIG. 10 is a characteristic diagram of a reference supercharging pressure.
FIG. 11 is a characteristic diagram of a weighted average coefficient.
FIG. 12 is a waveform diagram showing changes in the actual supercharging pressure during transition.
13 is a characteristic diagram of a constant K. FIG.
FIG. 14 is a waveform diagram for explaining the operation of the first embodiment.
FIG. 15 is a flowchart for explaining calculation of a target equivalent ratio.
FIG. 16 is a characteristic diagram of a standard target equivalent ratio.
FIG. 17 is a characteristic diagram of a weighted average coefficient.
FIG. 18 is a waveform diagram showing a change in the actual supercharging pressure during the transition according to the second embodiment.
FIG. 19 is a characteristic diagram of the amount of change in lamp response per predetermined time.
FIG. 20 is a flowchart for explaining calculation of a second target intake air amount according to the third embodiment.
FIG. 21 is a flowchart for explaining calculation of a target boost pressure.
FIG. 22 is a waveform diagram for explaining the operation of the third embodiment.
FIG. 23 is a diagram corresponding to a claim of the first invention.
FIG. 24 is a diagram corresponding to claims of the eighth invention.
[Explanation of symbols]
4 Fuel injection valve
7 Throttle valve
8 Throttle valve control device
11 Turbocharger (supercharger)
21 Control unit

Claims (8)

A device capable of controlling the opening of the throttle valve regardless of the accelerator pedal;
Means for calculating a target equivalent ratio that becomes a lean air-fuel ratio in a predetermined operating range;
Means for correcting the fuel amount obtained for the theoretical air-fuel ratio by the target equivalent ratio and calculating the target fuel amount;
Means for supplying the target fuel amount to the engine;
Means for calculating a target intake air amount at a theoretical air-fuel ratio as a reference target intake air amount;
Means for calculating a value obtained by dividing the reference target intake air amount by the target equivalent ratio as a target intake air amount;
A supercharger that operates to obtain a target supercharging pressure in the lean air-fuel ratio operating range;
Means for calculating an estimated value of the actual boost pressure when the standard engine is used under the reference atmospheric pressure;
Means for calculating a supercharging pressure correction value according to a deviation between the reference atmospheric pressure and the actual supercharging pressure estimated value at the time of acceleration in the lean air-fuel ratio operation region;
Means for calculating, as the second target intake air amount, a value obtained by correcting the target intake air amount by the boost pressure correction value;
An engine control device comprising: means for driving the throttle valve control device so that the second target intake air amount is introduced into the engine. The engine control device according to claim 1, wherein a change in the actual boost pressure estimated value at the time of acceleration is approximated by a dead time and a first-order delay. 2. The engine control device according to claim 1, wherein the change in the actual boost pressure estimated value at the time of acceleration is approximated with a dead time and a first-order lag, and the amount of reduction is corrected during the dead time. 4. The engine control device according to claim 3, wherein the reduction correction amount is a value corresponding to a change amount per predetermined time of an accelerator operation amount at the time of acceleration. 4. The engine control apparatus according to claim 3, wherein the amount of reduction correction is a value corresponding to an engine load and a rotational speed. 2. The engine control device according to claim 1, wherein a change in the actual supercharging pressure estimated value at the time of acceleration is approximated by a dead time and a ramp response. The engine control device according to claim 6, wherein a change amount of the ramp response per predetermined time is set according to an engine load and a rotational speed. A device capable of controlling the opening of the throttle valve regardless of the accelerator pedal;
Means for calculating a target equivalent ratio that becomes a lean air-fuel ratio in a predetermined operating range;
Means for correcting the fuel amount obtained for the theoretical air-fuel ratio by the target equivalent ratio and calculating the target fuel amount;
Means for supplying the target fuel amount to the engine;
Means for calculating a target intake air amount at a theoretical air-fuel ratio as a reference target intake air amount;
Means for calculating a value obtained by dividing the reference target intake air amount by the target equivalent ratio as a target intake air amount;
A supercharger that operates to obtain a target supercharging pressure in the lean air-fuel ratio operating range;
Means for calculating a target boost pressure when using a standard engine at a reference atmospheric pressure;
Means for detecting atmospheric pressure;
Means for reducing the target boost pressure in accordance with the difference between the reference atmospheric pressure and the detected atmospheric pressure value;
Means for detecting the actual supercharging pressure;
Means for calculating a boost pressure correction value according to a difference between the target boost pressure corrected for decrease and the actual boost pressure detection value at the time of acceleration in the operating range of the lean air-fuel ratio;
Means for calculating, as the second target intake air amount, a value obtained by correcting the target intake air amount by the boost pressure correction value;
An engine control device comprising: means for driving the throttle valve control device so that the second target intake air amount is introduced into the engine.

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