JP3888781B2 - Engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine control device that realizes lean combustion in a port injection engine or an in-cylinder injection engine, and in particular, when combustion states such as stratified combustion and homogeneous combustion are switched by performing combustion efficiency correction, respectively. The present invention relates to an engine control device that eliminates a torque step due to a difference in combustion efficiency at the time of switching by correcting a target cylinder air amount in the combustion state of the engine.
[0002]
[Prior art]
As a combustion method for an internal combustion engine, so-called lean combustion is known in which the air-fuel ratio of an air-fuel mixture supplied to the engine is controlled by making the fuel leaner than the stoichiometric air-fuel ratio (A / F = 14.7). The lean combustion is applied to both port injection engines and in-cylinder injection engines. Since the lean combustion engine has insufficient output in a specific operation state such as sudden start or acceleration of a vehicle or the like, in such a state, the lean air combustion engine is operated by controlling the air-fuel ratio in the vicinity of the theoretical air-fuel ratio. is doing. That is, the lean combustion engine is operated by changing the combustion state to stratified combustion, homogeneous combustion, stoichiometric combustion (from rich combustion to lean combustion) based on the change of the operating state.
[0003]
As a conventional lean combustion in-cylinder injection engine of this type, for example, there is a technique described in Japanese Patent Laid-Open No. 7-16916. This technology considers switching control between idle time and off-idle time corresponding to stratified combustion, and if it is determined that the engine is switched from off-idle operation to idle operation, the intake air amount can be increased and the pumping loss can be reduced. In this way, the fuel injection amount is corrected to decrease.
[0004]
Further, as this type of lean combustion port injection engine, for example, there is a technique described in JP-A-5-187295. This technique prevents a torque shock based on a change in combustion state (rich combustion-lean combustion), that is, a change in output torque that occurs when an air-fuel ratio is changed. A bypass passage that bypasses the throttle valve is provided in the intake passage. In addition, a valve is arranged in the bypass passage, and when the air-fuel ratio change control is switched, the bypass passage is opened and closed by the valve to increase or decrease the amount of intake air to the engine. The control is performed by switching the fuel ratio (combustion state).
[0005]
[Problems to be solved by the invention]
By the way, although the conventional control technology for the in-cylinder injection engine has been described for switching between two states of off-idle that performs homogeneous combustion and off-idle that performs stratified combustion that becomes leaner, it is homogeneous in off-idle. No consideration is given to combustion switching between combustion and stratified combustion, and no consideration is given to switching only the combustion state while maintaining a constant torque so that torque shock does not occur. In high-performance engines with the ability to perform stratified combustion at higher loads, combustion switching at off-idle exists, so when switching between two combustion states with different combustion efficiencies, a torque step occurs and torque There is a risk of shock, which is a problem.
[0006]
The control technology of the port injection engine calculates the deviation between the target intake air amount after switching and the detected intake air amount, and controls the valve opening of the bypass passage, thus elucidating the cause of torque shock However, control is not performed based on this. That is, since changes in combustion efficiency due to changes in the combustion state are not taken into consideration, it cannot be said that the torque shock can be sufficiently dealt with, and since it is a port injection engine, combustion that is a problem peculiar to the in-cylinder injection engine There is no consideration given to torque shock based on the difference in fuel injection timing due to the change of state.
[0007]
The present invention has been made in view of such a problem, and the object of the present invention is to prevent a torque step between before and after switching of the combustion state without causing an unpleasant shock to the driver. Another object of the present invention is to provide a lean combustion engine control device that smoothly switches the combustion state.
[0008]
[Means for Solving the Problems]
  In order to achieve the above object, the engine control device of the present invention basically includes a target torque calculating means for calculating a target torque, and a target basic cylinder intake amount for calculating a target basic cylinder intake air amount from the target torque and the engine speed. A cylinder intake air amount calculating means; and a fresh air excess ratio multiplying means for calculating a target cylinder intake air amount by multiplying the target basic cylinder intake air amount by a fresh air excess ratio (air-fuel ratio / 14.7).,And a combustion efficiency correction means for calculating a combustion efficiency correction rate based on the combustion state of the engine, the combustion efficiency correction means,EGR Air / fuel ratio indicating the ratio of gas + fresh air volume and fuel volume G / F The combustion efficiency correction factor is calculated from a table that is referenced usingA corrected target cylinder intake air amount is calculated by multiplying the target cylinder intake air amount by the combustion efficiency correction factor.ing.
[0009]
  Moreover, the engine control device of the present invention comprises:Target torque calculating means for calculating a target torque; target basic cylinder intake air amount calculating means for calculating a target basic cylinder intake air amount from the target torque and the engine speed; Fuel ratio / 14.7 ) To calculate the target cylinder intake air amount, and the engine control device includes combustion efficiency correction means for calculating a combustion efficiency correction rate based on the combustion state of the engine, Combustion efficiency correction means EGR Air / fuel ratio indicating the ratio of gas + fresh air volume and fuel volume G / F Is one axis, EGR The combustion efficiency correction factor is calculated from a map with the rate as another axis, and the target cylinder intake air amount is multiplied by the combustion efficiency correction factor to obtain the corrected target cylinder air intake amount.It is characterized by calculating.
  In order to determine the fuel injection amount, the engine control device of the present invention divides the intake air amount sucked into the cylinder by the engine speed and the air-fuel ratio becomes stoichiometric ( A / F = 14.7 And a means for calculating the basic fuel injection pulse width per cylinder by multiplying by a coefficient such as
[0010]
  The engine control device of the present invention is characterized in that the engine to be controlled is a port injection engine or a cylinder injection engine. Further, the combustion efficiency correction means of the present invention includes a plurality of maps or tables different for each difference in combustion state such as stratified combustion, weakly stratified combustion, homogeneous combustion, etc., and means for detecting the difference in the combustion state And selecting one of the plurality of maps or tables based on the difference in the combustion stateIt is characterized by calculating a combustion efficiency correction factor.
[0011]
  Also,The engine control apparatus of the present invention includes throttle opening conversion means for converting the corrected target cylinder intake amount into a target throttle opening, and the target throttle opening conversion means uses the corrected target cylinder intake amount as one axis, Calculate the throttle opening from a map with the engine speed as another axis, or as an intermediate parameter from a map with the corrected target cylinder intake air as one axis and the engine speed as another axis Calculate the throttle opening area, and then target throttle opening from the table with the throttle opening area as the axisIt is characterized by calculating.
  The engine control apparatus of the present invention further includes operating point correction value calculating means for calculating the correction value based on the operating point of the operating state such as whether the combustion efficiency correcting means is engine speed, engine load, and idle state. The combustion efficiency correction rate is corrected by multiplying the calculated correction value. Further, in the engine control device of the present invention, the combustion efficiency correction means includes engine deterioration with time, engine variation, etc. The correction factor calculated by the external factor correction value calculating unit is corrected by multiplying the calculated correction value by the external factor correction value calculating unit. Is ECM Stored in the non-volatile memory of the ignition switch off Even when the power supply battery is replaced, the nonvolatile memory is stored and held.
[0012]
In the engine control device according to the present invention configured as described above, in the control of the intake air amount, the target torque calculation means calculates the target torque from the accelerator opening and the engine speed that the driver intends, and then The target basic cylinder intake air amount calculating means calculates the target basic cylinder intake air amount from the target torque and the engine speed, and the fresh air excess rate multiplying means calculates the target basic cylinder intake air amount so that the intake air amount increases lean relative to the stoichiometry. The target cylinder intake air amount is calculated by multiplying the amount by the fresh air excess rate, and the target cylinder intake air amount is corrected by the combustion efficiency correction means by multiplying the target cylinder intake air amount by the combustion efficiency correction rate, and the throttle opening conversion means Then, the corrected target cylinder intake air amount is converted into the throttle opening, and the actual throttle opening is manipulated by the intake air amount control means.
[0013]
On the other hand, in the control of the fuel injection amount, the basic cylinder intake air amount calculation means calculates the basic cylinder intake air amount from the intake air amount and the engine speed, and the air-fuel ratio correction means updates the basic cylinder intake air amount. The fuel injection pulse width for realizing the target air-fuel ratio is calculated by dividing by the excess air ratio, and the fuel is injected by the fuel injection means during the designated fuel injection pulse width.
[0014]
By performing combustion control as described above, even if the combustion state (homogeneous combustion, stratified combustion, etc.) changes suddenly due to switching, the intake air amount can be controlled to eliminate the difference in engine output torque caused by the difference in combustion efficiency. As a result, the combustion state can be smoothly switched without causing a shock to the vehicle.
[0015]
Further, since the combustion efficiency correction means calculates the combustion efficiency correction factor from a table or map that is referenced with the air / fuel ratio A / F or the air / fuel ratio G / F as an axis, the target cylinder intake air amount can be accurately corrected downward. And the step difference in engine output torque can be eliminated.
Further, the combustion efficiency correction rate calculating means includes operating point correction value calculating means for calculating a correction value based on the operating point of the operating state such as engine speed, engine load, and idling state, engine deterioration over time, engine By additionally providing external factor correction value calculation means for calculating the correction value based on individual variations, etc., the combustion efficiency correction rate changes depending on the operating point of the operating state even with the same air-fuel ratio G / F and the same EGR rate. By calculating the correction value, it is possible to calculate the optimal combustion efficiency correction factor for each operating state, to enable engine operation without a torque step, and to easily adjust the combustion variation for each vehicle.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an engine control apparatus according to the present invention will be described below in detail with reference to the drawings.
FIG. 1 shows the overall configuration of the control system of the engine 507 according to the first embodiment of the present invention. In FIG. 1, the air sucked into the engine 507 is taken in from the inlet portion 502a of the air cleaner 502, passes through the air flow sensor 503, passes through the throttle body 505 containing the throttle valve 505a for controlling the intake flow rate, and enters the collector 506. enter. The air sucked into the collector 506 is distributed to the intake pipes 501 connected to the cylinders 507b of the engine 507, and is guided to the combustion chamber 507c in the cylinder 507b. The throttle valve 505a can be opened and closed by a motor 522.
[0017]
On the other hand, a fuel such as gasoline is primarily pressurized from a fuel tank 514 by a fuel pump 510 and further pressurized by a fuel pump 511 and supplied to a fuel system in which an injector 509 is piped. The primary pressurized fuel is regulated to a constant pressure (for example, 3 kg / cm "2) by the fuel pressure regulator 512, and the fuel secondarily pressurized to a higher pressure is regulated to a constant pressure by the fuel pressure regulator 513. The pressure is adjusted to (for example, 70 kg / m "2) and injected from the injector 509 provided in each cylinder 507b into the cylinder 507b. The injected fuel is ignited by the ignition coil 508 by the ignition signal that has been increased in voltage by the ignition coil 522.
[0018]
Further, the air flow sensor 503 outputs a signal indicating the intake flow rate and is input to the control unit 515.
Further, a throttle sensor 504 for detecting the opening degree of the throttle valve 505a is attached to the throttle body 505, and its output is also input to the control unit 515.
[0019]
Next, the crank angle sensor 516 attached to the camshaft shaft (not shown) outputs a reference angle signal REF indicating the rotation position of the crankshaft 507d and an angle signal POS for detecting the rotation signal (rotation number). These signals are also input to the control unit 515.
[0020]
The A / F sensor 518 installed in front of the catalyst 520 in the exhaust pipe 519 detects exhaust gas, outputs the detection signal and inputs it to the control unit 515, and the accelerator opening sensor 521 The opening degree of the pedal is detected, and the detection signal is input to the control unit 515.
[0021]
FIG. 2 shows the main part of the control unit 515. The control unit 515 is composed of an MPU, ROM, RAM, an I / O LSI including an A / D converter, and the like, and detects the operating state of the engine 507. Captures signals from various sensors as input, executes predetermined calculation processing, outputs various control signals calculated as the calculation results, and supplies predetermined control signals to the injector 509 and ignition coil 522 described above Then, fuel supply amount control and ignition timing control are executed.
[0022]
FIG. 3 shows an overall block diagram of control executed by the control unit 515 in the in-cylinder injection engine 507.
In FIG. 3, the upper part is an intake air amount control system, and the lower part is a fuel amount control system. In the upper intake air amount control system, the target torque calculating means 101 calculates the target torque based on the accelerator opening and the engine speed which are the will of the driver, and the target basic cylinder intake air amount calculating means 102 calculates the target torque and The target basic cylinder intake air amount is calculated from the engine speed, and the fresh air excess rate multiplying means 103a multiplies the target basic cylinder intake air amount by the fresh air excess rate so that the intake air amount increases lean relative to the stoichiometric air. Then, the combustion efficiency correction means 103b calculates the corrected target cylinder air amount tTP by correcting the target cylinder intake air amount to a combustion state with good fuel consumption by multiplying the combustion efficiency correction rate by the combustion efficiency correction means 103b. The throttle opening degree conversion means 104 converts the throttle opening degree based on the corrected target cylinder intake amount and the engine speed, and the intake amount control means 105 operates the actual throttle opening degree.
[0023]
On the other hand, in the fuel amount control system in the lower part of FIG. 3, the basic cylinder intake air amount calculation means 106 calculates the basic cylinder intake air amount from the intake air amount and the engine speed, and the air-fuel ratio adjustment means 107 calculates the basic air intake amount. The fuel injection pulse width for realizing the target air-fuel ratio is calculated by dividing the cylinder intake air amount by the fresh air excess ratio, and the fuel is injected by the fuel injection means 108 at the designated fuel injection pulse width.
[0024]
The overall configuration of the control device for the intake air amount control system and the fuel amount control system has been described above, but the combustion efficiency correction means 103b, which is a feature of this embodiment, will be described in more detail based on FIG.
The combustion efficiency correction means 103b inputs signals of a fresh air excess rate, a target EGR rate, and a combustion state (stratification, homogeneous, etc.), and the fresh air excess rate (target air-fuel ratio / 14.7) and the target EGR A combustion efficiency correction rate is calculated from a map prepared in advance based on the signal with the rate. A plurality of maps are prepared for each combustion state (stratification, homogeneous, etc.), and the combustion efficiency correction factor is calculated by selecting the map for each combustion state. The corrected target cylinder intake air amount is calculated by multiplying the target cylinder intake air amount by the calculated combustion efficiency correction rate.
[0025]
Here, the operation principle of the combustion efficiency correction means 103b will be described. Lean combustion aims to reduce pumping loss by reducing the amount of fuel (thinning the air-fuel ratio) and increasing the amount of intake air compared to stoichiometric combustion. First, as shown in equation (2), if the air-fuel ratio is reduced while the lean fuel amount QF # lean is equal to the stoichiometric fuel amount QF # st, the intake air amount QA # lean is less than the stoichiometric QA # st. The ratio increases to (target air-fuel ratio) /14.7 as shown in equation (1). However, since the fuel consumption can be improved by about 10% to 40% by reducing the pumping loss, the amount of air and the amount of fuel can be reduced to output the same torque as the stoichiometric amount. In the equation (3), the intake air amount QA # lean at the time of lean is ITAF (value of about 0.6 to 0.9) times, and the fuel amount is also ITAF times as shown in the equation (4).
[0026]
QA # lean = QA # st × (Target air-fuel ratio) /14.7 Formula (1)
QF # lean = QF # st formula (2)
QA # lean = QA # st × (Target air-fuel ratio) /14.7 * ITAF formula (3)
QF # lean = QF # st × ITAF formula (4)
[0027]
Here, ITAF is a combustion efficiency correction factor and does not become a constant value because the value changes depending on the thinness of the air-fuel ratio and the EGR rate.
Among the lean burn engines, in particular, in the cylinder injection engine, the lean air-fuel ratio is large because the air-fuel mixture can be collected in one part and stratified combustion can be performed. An example of setting is shown in FIG. In general, the ITAF decreases as the air-fuel ratio decreases, and the ITAF decreases as the EGR rate increases.
[0028]
FIG. 5 shows the sensitivity of the combustion efficiency correction factor ITAF to the air-fuel ratio. On the horizontal axis, the air-fuel ratio A / F and the fresh air excess ratio tλa0 are plotted. The fresh air excess ratio is (target air-fuel ratio) /14.7, is calculated as in equation (5), and becomes 1 at the time of stoichiometry. When the fresh air excess rate is used, equation (3) can be rewritten as equation (6).
tλa0 = (Target air / fuel ratio) /14.7 Formula (5)
QA # lean = QA # st × tλa0 * ITAF formula (6)
[0029]
Next, looking at the case where EGR (combustion gas recirculation) is applied, the fresh air excess rate is calculated from the ratio of the intake air amount and the fuel amount, but when EGR is applied, the air-fuel ratio is calculated. A / F is replaced with an air-fuel ratio G / F that takes into account the recirculated combustion gas, and is expressed by equation (7).
G / F = A / F × (100 + EGR rate) / 100 formula (7)
[0030]
FIG. 7 shows the characteristic of the combustion efficiency correction rate with respect to the air-fuel ratio G / F, which is almost the same tendency as FIG. In FIG. 7, the abscissa along with the air-fuel ratio G / F is the excess gas ratio tλg0. The excess gas ratio is defined as in equation (8) with the same idea as the excess fresh air ratio.
tλg0 = (Target air-fuel ratio G / F) /14.7 Equation (8)
[0031]
  When the EGR rate is increased at the same air-fuel ratio G / F, the combustion efficiency correction rate with respect to the EGR rate has a characteristic as shown in FIG. 9, and changes by several percent even at the same air-fuel ratio G / F. Therefore, in order to obtain the combustion efficiency correction factor more accurately, the characteristic is as shown in FIG. 8, and a number of correction factor curves can be drawn depending on the difference in the EGR rate. In order to use this relationship in actual control, the air / fuel ratio G / F and EGR rate as shown in FIG. 10 are used as axes.mapIs required.
[0032]
Here, paying attention to FIG. 5, FIG. 7, and FIG. 8, there are inflection points and discontinuities in the vicinity of the air-fuel ratio 20, but this is due to the combustion difference peculiar to the in-cylinder injection engine. The lean side is stratified combustion in which fuel is injected during the compression stroke, and the rich side is homogeneous combustion in which fuel is injected during the intake stroke.
[0033]
Therefore, even if there is such a difference in combustion, in order to accurately correct the combustion efficiency before and after the difference, a homogeneity map 1101 and a stratification map 1102 are provided as shown in the block diagram of FIG. It is preferable to use it by switching.
[0034]
FIG. 12 shows an example of a flowchart at the time of switching. The series of processing here is performed by interruption processing (step 1201) executed at regular intervals. First, the combustion state is read in step 1202, and it is determined in step 1203 whether it is homogeneous combustion or stratified combustion. If it is determined that the combustion is homogeneous, the process proceeds to step 1204. In step 1204, the air-fuel ratio G / F and the EGR rate in consideration of the recirculated combustion gas are read. In step 1205, the combustion efficiency is corrected from the homogeneity map. Search rate ITAF.
[0035]
On the other hand, if it is determined in step 1203 that the combustion is stratified combustion, the process proceeds to step 1206. In step 1206, the air-fuel ratio G / F and the EGR rate are read. Search for. Thereafter, in both cases of homogeneous combustion and stratified combustion, the routine proceeds to step 1208, where the corrected target cylinder intake air amount tTP is calculated based on the equation (9).
tTP = tTPst × tλg0 × ITAF equation (9)
[0036]
Next, a case will be described in which the combustion state is stratified and homogeneous, and weak stratified combustion which is intermediate combustion between both combustion states can be taken. Weak stratified combustion is a combustion method in an air-fuel ratio range between the air-fuel ratio of homogeneous combustion and the air-fuel ratio of stratified combustion, and fuel injection in one stroke is performed in two steps, an intake stroke and a compression stroke It is. Weakly stratified combustion is effective as combustion when the combustion stability is poor in both homogeneous combustion and stratified combustion.
[0037]
FIG. 13 shows a block diagram of the combustion efficiency correction in consideration of weak stratified combustion. The map for correcting the combustion efficiency is composed of a homogeneity map 1301, a stratification map 1303, and a weak stratification map 1302, and each map is selected according to each combustion state, and a combustion efficiency correction rate ITAF is calculated. The
[0038]
FIG. 14 shows an example of a flowchart for switching the maps based on the three combustion states. This series of processing is performed by interrupt processing (step 1401) executed at regular intervals. First, in step 1402, the combustion state is read, and in step 1403, it is determined whether the read combustion state is homogeneous combustion. If it is determined that the combustion is homogeneous, the routine proceeds to step 1404, where the air-fuel ratio G / F and the EGR rate are read in step 1404, and the combustion efficiency correction rate ITAF is retrieved from the homogeneity map in step 1505.
[0039]
If it is determined in step 1403 that the combustion is not homogeneous, the process proceeds to step 1411. In step 1411, it is determined whether or not the combustion is weakly stratified. If it is determined that the combustion is weakly stratified, the air-fuel ratio G / F and the EGR rate are read in step 1406, and the process proceeds to step 1407. In step 1407, the combustion efficiency correction rate ITAF is retrieved from the weak stratification map.
[0040]
If it is determined in step 1411 that the combustion is neither homogeneous combustion nor weakly stratified combustion, since it is stratified combustion, the process proceeds to step 1408. In step 1408, the air-fuel ratio G / F and the EGR rate are read. Search the combustion efficiency correction factor ITAF from the stratification map.
In any of the three combustion states, after searching for the combustion efficiency correction factor ITAF, the routine proceeds to step 1410, where the corrected target cylinder intake air amount tTP is calculated based on the equation (9).
[0041]
An example of the calculation of the combustion efficiency correction unit 103b has been described above. Returning to FIG. 3, after the combustion efficiency correction unit 103b obtains the corrected target cylinder intake amount by multiplying the combustion efficiency correction rate, the throttle opening rate is increased. The target throttle opening is obtained by the degree conversion means 104.
FIG. 15 shows an example of the throttle opening degree conversion means 104, which obtains the target throttle opening degree tTVO by map search from the corrected target cylinder intake air amount tTP and the engine speed NE.
[0042]
  FIG. 16 is another example of the throttle opening conversion means 104, and a target throttle opening area map 1601 is searched by using the axes of the corrected target cylinder intake amount tTP and the engine speed NE to obtain the target throttle opening area tATVO. Ask. Then, target throttle openingtableThe target throttle opening tTVO is obtained by searching 1602 on the axis of the target throttle opening area.
[0043]
Next, FIG. 17 shows an example of the target torque calculation means 101 in the configuration of the control block of FIG. Here, the target torque tTc is calculated by searching a map based on two signals of the accelerator opening APS and the engine speed NE.
[0044]
In the processing after the target torque is generated, the target basic cylinder intake amount tTPst is calculated by the target basic cylinder intake amount calculating means 102. FIG. 18 shows an example of the calculation of the target basic cylinder intake amount tTPst, and the target basic cylinder intake amount tTPst is calculated from the target torque tTc and the engine speed NE by map search.
[0045]
Next, the lower fuel amount control system in the overall configuration of the control block of FIG. 3 will be described.
The fuel amount control system includes a basic cylinder intake air amount calculation means 106, an air-fuel ratio correction means 107, and a fuel injection means 108.
FIG. 19 shows an example of the basic cylinder intake air amount calculating means 106. The basic cylinder intake air amount calculating means 106 first calculates the intake air amount Qa measured by the air flow sensor 503 as the engine speed NE. The basic cylinder intake air amount TP is calculated by dividing the intake air amount per cylinder and then multiplying by a coefficient Kconst for converting the fuel injection time such that the air-fuel ratio becomes stoichiometric.
[0046]
FIG. 20 shows an example of the processing of the air-fuel ratio correction means 107 which is the subsequent stroke of the basic cylinder intake air amount calculation means 106. First, the calculated basic cinder intake air amount TP is divided by the fresh air excess ratio tλa0 to correct the injection pulse width so as to achieve the target air-fuel ratio, and further, in order to compensate for the delay time of the injector valve opening. The fuel injection pulse width Ti is corrected and calculated by adding the valve delay time TS.
[0047]
FIG. 21 is a diagram showing in detail an example of the movement of each control parameter when the engine control of the present embodiment described above is applied to the control of the lean burn engine. In this example, the air-fuel ratio is switched when the accelerator opening is constant and equal torque is required. A solid line in FIG. 21 is an example when the present embodiment is applied, and a dotted line is an example when the application is not applied. First, when the target air-fuel ratio A / F changes from 14.7 to 30, the combustion efficiency correction means 103 changes the combustion efficiency correction rate from 1.0 to 0.9. When the present embodiment is applied, the amount of intake air is corrected downward by 0.9, compared to the dotted line when not applied. As a result, the fuel injection pulse width is also reduced as the fuel efficiency is improved by leaning when the present embodiment is applied. When the present embodiment is not applied, the engine output torque increases after switching. However, when the present embodiment is applied, the engine output torque is not changed before and after switching. As a final behavior of the vehicle equipped with the engine, when this embodiment is not applied, a shock occurs as shown in FIG. 21 after the combustion switching, but when this embodiment is applied, no shock occurs. .
[0048]
Next, a second embodiment of the present invention will be described.
In the second embodiment, the calculation of the combustion efficiency correction factor calculated by the combustion efficiency correction means 103b of the first embodiment is performed in consideration of other control factors of the engine. There is a difference from the first embodiment in this point. Therefore, this point will be described below, and description of common matters will be omitted.
In the second embodiment, the combustion efficiency correction rate calculated by the combustion efficiency correction means 103b of the first embodiment is corrected by calculating a correction value for each operating situation, and depending on factors from the outside of the engine, The combustion efficiency correction rate can be corrected.
[0049]
FIG. 22 shows a control block diagram of the combustion efficiency correction means 203 of the present embodiment (second). The combustion efficiency correction means 203 includes a basic combustion efficiency correction rate calculation means 203a and an operating point correction value calculation means 203b. And external factor correction value calculation means 203c.
The basic combustion efficiency correction rate calculation means 203a has the same function as the combustion efficiency correction means 103b (see FIG. 4) of the first embodiment, and includes a fresh air excess rate, a target EGR rate, and Each signal of combustion state (stratification, homogeneous, etc.) is input, and the basic combustion efficiency correction factor is calculated from a map prepared in advance based on the signal of the excess air ratio (target air / fuel ratio / 14.7) and the target EGR rate. Is to be calculated. A plurality of maps are prepared for each combustion state (stratification, homogeneous, etc.), and the basic combustion efficiency correction factor ITAFO is calculated by selecting the map for each combustion state.
[0050]
The operating point correction value calculation means 203b inputs signals indicating whether the combustion state (stratification, homogeneity, etc.), engine speed, engine load (target torque), and idling, and the engine speed and the engine. Based on the signal with the load, the operating point correction value KITAFO is calculated from a map prepared in advance. A plurality of maps are prepared for each combustion state (stratification, homogeneous, etc.), and the operating point correction value is calculated by selecting the map for each combustion state. Different maps are prepared depending on whether the map is idle or not, and the map is selected to calculate an operating point correction value.
The external factor correction value calculation means 203c deals with factors such as engine combustion variations for each vehicle, and calculates an external factor correction value ITAFV based on the factors. Further, the correction value calculated by the external factor correction value calculation means 203c is stored in the non-volatile memory of the ECM, and is stored and held in the non-volatile memory even when the ignition switch is turned off or when the power supply battery is replaced. It can be output again.
[0051]
By multiplying the basic combustion efficiency correction rate ITAFO by the operating point correction value KITAFO and the external factor correction value ITAFV, a combustion efficiency correction rate is calculated, and the calculated combustion efficiency correction rate is multiplied by the target cylinder intake air amount. The corrected target cylinder intake air amount tTP is calculated.
FIG. 23 shows an example of a flowchart for switching the combustion state of the engine. The series of processing here is performed by interrupt processing (step 2201) executed at regular intervals. First, in step 2202, the combustion state is read, and in step 2203, it is determined whether the combustion is homogeneous or stratified combustion. If it is determined that the combustion is homogeneous, the process proceeds to step 2204. In step 2204, the air-fuel ratio G / F and the EGR rate considering the recirculation combustion gas are read. In step 2205, the basic map is read from the homogeneous map. Search for the combustion efficiency correction factor ITAFO.
[0052]
Next, in step 2208, it is determined whether the idle switch SW is ON or OFF. If it is determined that the idle switch SW is ON, the process proceeds to step 2212, the engine speed and the target torque are read, and the process proceeds to step 2213, where the combustion efficiency operating point correction value KITAFO is retrieved from the idle homogeneity map (calculation). Then, the process proceeds to Step 2218. If it is determined in step 2208 that the idle switch SW is OFF, the process proceeds to step 2210, in which the engine speed and the target torque are read. In step 2211, the operating point correction value KITAFO for the combustion efficiency is set from the off-idle homogeneity map. Search (calculate) and go to Step 2218.
[0053]
On the other hand, if it is determined in step 2203 that the combustion is stratified combustion, the process proceeds to step 2206. In step 2206, the air-fuel ratio G / F and the EGR rate considering the recirculated combustion gas are read. The basic combustion efficiency correction rate ITAFO is retrieved from the map for processing, and the routine proceeds to step 2218.
Next, in step 2209, it is determined whether the idle switch SW is ON or OFF. If it is determined that the idle switch SW is ON, the process proceeds to step 2214, the engine speed and the target torque are read, and the process proceeds to step 2215, where the combustion efficiency operating point correction value KITAFO is retrieved (calculated) from the idle stratification map. Then, the process proceeds to Step 2218. If it is determined in step 2209 that the idle switch SW is OFF, the process proceeds to step 2216, in which the engine speed and the target torque are read. In step 2217, the operating point correction value KITAFO for the combustion efficiency is determined from the off-idle stratification map. Search (calculate) and go to Step 2218.
[0054]
In step 2218, a signal of an external factor such as an engine combustion variation for each vehicle is read to calculate an external factor correction value ITAFV, and the process proceeds to step 2219. In step 2219, the following equation ( 10), the corrected target cylinder intake air amount tTP is calculated, and the interruption process is terminated.
tTP = tTPst x tλg0 x ITAFO x KITAFO x ITAFV Formula (10)
However,
tTP: Corrected target cylinder intake air amount
tTPst: Target basic cylinder intake volume
tλg0: Fresh air excess rate
ITAFO: Basic combustion efficiency correction factor
KITAFO: Combustion efficiency operating point correction value
ITAFV: External factor correction value
[0055]
FIG. 24 shows another example of a flowchart for switching the combustion state of the engine according to the second embodiment of the present invention. The difference between this flowchart and the flowchart of FIG. 23 is that there is a weakness other than the distinction between the homogeneous combustion zone and the stratified combustion zone when the basic combustion efficiency correction rate calculating means 203a of FIG. 22 calculates the basic combustion efficiency correction rate value ITAFO. There is no difference except that the stratified combustion zone is set. By setting the weakly stratified combustion region, a more accurate basic combustion efficiency correction factor value ITAFO is to be calculated.
[0056]
The series of processing here is performed by interrupt processing (step 3300) executed at regular intervals. First, in step 3301, the combustion state is read, and in step 3302, it is determined whether or not the combustion is homogeneous. If it is determined that the combustion is homogeneous, the process proceeds to step 3304. In step 3304, the air-fuel ratio G / F and the EGR rate in consideration of the recirculation combustion gas are read. Search for the combustion efficiency correction factor ITAFO.
Next, in step 3310, it is determined whether the idle switch SW is ON or OFF. If it is determined that the idle switch SW is ON, the process proceeds to step 3315, the engine speed and the target torque are read, and the process proceeds to step 3316, where the combustion efficiency operating point correction value KITAFO is retrieved from the idle homogeneity map (calculation). Then, the process proceeds to Step 3325. If it is determined in step 3310 that the idle switch SW is OFF, the process proceeds to step 3313, where the engine speed and the target torque are read. In step 3314, the operating point correction value KITAFO for the combustion efficiency is determined from the off-idle homogeneity map. Search (calculate) and go to Step 3325.
[0057]
On the other hand, if it is not determined in step 3302 that the combustion is homogeneous, the process proceeds to step 3303, where it is determined whether the combustion is weakly stratified combustion or stratified combustion. If it is determined in step 3303 that the combustion is weakly stratified, the process proceeds to step 3306. In step 3306, the air-fuel ratio G / F and the EGR rate considering the recirculated combustion gas are read. In step 3307, weakly stratified combustion is performed. The basic combustion efficiency correction rate ITAFO is searched from the operational map, and the process proceeds to step 3311.
[0058]
Next, in step 3311, it is determined whether the idle switch SW is ON or OFF. If it is determined that the idle switch SW is ON, the process proceeds to step 3317, the engine speed and the target torque are read, and the process proceeds to step 3318, where the combustion efficiency operating point correction value KITAFO is retrieved from the idle stratification map (calculation). Then, the process proceeds to Step 3325. If it is determined in step 3311 that the idle switch SW is OFF, the process proceeds to step 3319, where the engine speed and the target torque are read. In step 3320, the operating point correction value KITAFO for the combustion efficiency is determined from the off-idle stratification map. Search (calculate) and go to Step 3325.
[0059]
If it is determined in step 3303 that the combustion is stratified combustion, the process proceeds to step 3308. In step 3308, the air-fuel ratio G / F and the EGR rate in consideration of the recirculated combustion gas are read. The basic combustion efficiency correction rate ITAFO is searched, and the process proceeds to Step 3312.
Next, in step 3312, it is determined whether the idle switch SW is ON or OFF. If it is determined that the idle switch SW is ON, the flow proceeds to step 3321, the engine speed and the target torque are read, and the flow proceeds to step 3322, where the combustion efficiency operating point correction value KITAFO is retrieved from the idle stratification map (calculation). Then, the process proceeds to Step 3325. If it is determined in step 3312 that the idle switch SW is OFF, the process proceeds to step 3323, where the engine speed and the target torque are read. In step 3324, the operating point correction value KITAFO for the combustion efficiency is calculated from the off-idle stratification map. Search (calculate) and go to Step 3325.
[0060]
In step 3325, a signal of an external factor such as an engine combustion variation for each vehicle is read, an external factor correction value ITAFV is calculated, and the process proceeds to step 3326. In step 3326, the equation (10) is calculated based on each calculated value. ) To calculate the target cylinder intake air amount tTP, and the interruption process is completed.
The two embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the invention described in the claims. Can be changed.
For example, in the above-described embodiment, the lean combustion in-cylinder injection engine has been described. However, the present invention can be applied to other lean combustion engines such as a port injection engine.
[0061]
【The invention's effect】
As can be understood from the above description, the engine control device for the lean combustion engine according to the present invention performs the switching because the combustion efficiency correction means calculates the combustion efficiency correction rate according to the combustion state and corrects the intake air amount. Even if the combustion state (homogeneous combustion, stratified combustion, etc.) changes suddenly, the intake air amount can be controlled to eliminate the difference in engine output torque caused by the difference in combustion efficiency, and as a result, no shock is generated in the vehicle. Smooth combustion state switching can be realized.
Further, since the combustion efficiency correction rate is corrected based on the change in the operating point of the operating state, the individual variation of the engine, and the like, a combustion state without an output torque step can be realized in engine operation.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an in-cylinder injection engine system according to an embodiment of the present invention.
2 is an internal configuration diagram of a control device of the in-cylinder injection engine system of FIG. 1;
3 is a control block diagram of the in-cylinder injection engine control device of FIG. 1. FIG.
4 is a detailed view of a combustion efficiency correction unit of the control block of FIG. 3;
FIG. 5 is a characteristic diagram of a table for calculating a combustion efficiency correction factor of the combustion efficiency correcting means of FIG. 4;
6 is a diagram showing an example of setting an air-fuel ratio of the direct injection engine control device of FIG. 1. FIG.
7 is another characteristic diagram of a table for calculating the combustion efficiency correction rate of the combustion efficiency correcting means of FIG. 4;
FIG. 8 is still another characteristic diagram of the table in consideration of the EGR rate for calculating the combustion efficiency correction rate of the combustion efficiency correction means of FIG. 4;
FIG. 9 is a characteristic diagram showing EGR sensitivity of the combustion efficiency correction rate.
10 is a block diagram of a map of the combustion efficiency correction means of FIG.
11 is a block diagram of map selection of the combustion efficiency correction means of FIG. 4;
12 is a control flowchart of the control device of FIG. 3;
13 is another block diagram of map selection of the combustion efficiency correction means of FIG.
14 is another control flowchart of the control device of FIG. 3;
15 is a block diagram of throttle opening conversion means of the control device of FIG. 3;
FIG. 16 is another block diagram of throttle opening conversion means of the control device of FIG. 3;
FIG. 17 is a block diagram of target torque calculation means of the control device of FIG. 3;
18 is a block diagram of target basic cylinder intake air amount calculation means of the control device of FIG. 3;
19 is a block diagram of basic cylinder intake air amount calculation means of the control device of FIG. 3;
20 is a block diagram of air-fuel ratio correction means of the control device of FIG. 3;
FIG. 21 is a control state diagram showing changes in parameters during control of the control device of FIG. 3;
FIG. 22 is a detailed view of the combustion efficiency correction means of the control block of the direct injection engine control apparatus according to another embodiment of the present invention.
FIG. 23 is a control flowchart of the engine control device of FIG. 22;
FIG. 24 is another control flowchart of the engine control device of FIG. 22;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Target torque calculating means, 102 ... Target basic cylinder intake air amount calculating means, 103a ... Fresh air excess ratio multiplying means, 103b ... Combustion efficiency correcting means, 104 ... Throttle opening degree converting means, 105 ... Intake air amount controlling means, 106 ... Basic cylinder intake air amount calculation means 107 ... Air-fuel ratio correction means 108 ... Fuel injection means 203 ... Combustion efficiency correction means 203a ... Basic combustion efficiency correction rate calculation means 203b ... Operating point correction value calculation means 203c ... External factor correction value calculation means, 508 ... spark plug, 509 ... injector, 515 ... control unit, 521 ... accelerator opening sensor, 522 ... throttle drive motor, 505a ... throttle valve, 1001 ... combustion efficiency correction factor map

Claims (13)

Target torque calculating means for calculating a target torque; target basic cylinder intake air amount calculating means for calculating a target basic cylinder intake air amount from the target torque and the engine speed; in the engine control apparatus having a fresh air excess ratio multiplier means for calculating a target cylinder intake air quantity by multiplying the ratio /14.7), and
The engine control device includes combustion efficiency correction means for calculating a combustion efficiency correction rate based on a combustion state of the engine, and the combustion efficiency correction means includes an air-fuel ratio G indicating a ratio of EGR gas + fresh air amount and fuel amount. An engine control apparatus that calculates a combustion efficiency correction rate from a table that is referenced with / F as an axis, and calculates a corrected target cylinder intake air amount by multiplying the target cylinder intake air amount by the combustion efficiency correction rate. Target torque calculating means for calculating a target torque; target basic cylinder intake air amount calculating means for calculating a target basic cylinder intake air amount from the target torque and the engine speed; in the engine control apparatus having a fresh air excess ratio multiplier means for calculating a target cylinder intake air quantity by multiplying the ratio /14.7), and
The engine control device includes combustion efficiency correction means for calculating a combustion efficiency correction rate based on a combustion state of the engine, and the combustion efficiency correction means includes an air-fuel ratio G indicating a ratio of EGR gas + fresh air amount and fuel amount. A combustion efficiency correction rate is calculated from a map having / F as one axis and an EGR rate as another axis, and a corrected target cylinder intake amount is calculated by multiplying the target cylinder intake amount by the combustion efficiency correction rate. An engine control device characterized by that. In order to determine the fuel injection amount, the engine control device divides the intake air amount sucked into the cylinder by the engine rotational speed and multiplies the coefficient so that the air-fuel ratio becomes stoichiometric (A / F = 14.7). The engine control apparatus according to claim 1 or 2 , further comprising means for calculating a basic fuel injection pulse width per cylinder. The engine control device according to any one of claims 1 to 3 , wherein the engine is a lean combustion port injection engine. The engine control device according to any one of claims 1 to 3 , wherein the engine is a lean combustion in-cylinder injection engine. The combustion efficiency correction means includes different maps for each difference in combustion state such as stratified combustion, weak stratified combustion, and homogeneous combustion , and includes means for detecting the difference in the combustion state. 6. The engine control apparatus according to claim 5 , wherein a combustion efficiency correction factor is calculated by selecting one of the maps based on the map . The combustion efficiency correction means includes a different table for each difference in combustion state such as stratified combustion, weakly stratified combustion, and homogeneous combustion , and also includes means for detecting the difference in the combustion state. 6. The engine control device according to claim 5 , wherein a combustion efficiency correction factor is calculated by selecting one of the tables based on the table . The engine control apparatus according to any one of claims 1 to 3 , further comprising target throttle opening conversion means for converting the corrected target cylinder intake air amount into a target throttle opening. The target throttle opening degree conversion means corrects the target cylinder intake air amount is one axis, according to claim 8, characterized in that to calculate the throttle opening degree map in which the engine speed and another one axis Engine control device. The target throttle opening conversion means calculates the throttle opening area as an intermediate parameter from a map with the corrected target cylinder intake amount as one axis and the engine speed as another axis, and the throttle opening area as an axis. 9. The engine control device according to claim 8, wherein the target throttle opening is calculated from the table. The combustion efficiency complement Seite stage, the engine speed, engine load, and includes an operating point correction value calculating means for calculating a correction value by the operating point of the operating state of the idle whether such, the combustion efficiency correction rate , the engine control apparatus according to any one of claims 1 to 3, characterized in that it is corrected by multiplying a correction value the calculation. The combustion efficiency complement Seite stage aging of the engine, an external factor correction value calculating means for calculating a correction value based on the engine individual variations or the like, the combustion efficiency correction rate by multiplying the correction value the calculating The engine control device according to any one of claims 1 to 3 , wherein the engine control device is corrected by the following. The correction value calculated by the external factor correction value calculation means is stored in the non-volatile memory of the ECM, and is stored and held in the non-volatile memory even when the ignition switch is turned off or the power supply battery is replaced. The engine control apparatus according to claim 12 .

Images