JP2006328963A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly make a quantity increase correction of a fuel injection quantity performed in a low load, even when performing purge processing. <P>SOLUTION: This internal combustion engine 10 has an air flowmeter 52 for detecting the intake air volume on the upstream side more than a purge passage 33 in an intake passage 14. The internal combustion engine 10 performs the purge processing for introducing evaporated fuel generated from a fuel tank 21 to a surge tank 16 via the purge passage 33. An electronic control device 40 controls the fuel injection quantity of the internal combustion engine 10. This electronic control device 40 increasingly corrects the fuel injection quantity in the low load of the engine on the basis of its load rate by calculating the load rate of the engine on the basis of the intake air volume detected by the air flowmeter 52. When performing the purge processing, its intake air volume is increasingly corrected by adding the purge air volume introduced to the surge tank 16 via the purge passage 33 to the intake air volume detected by the air flowmeter 52. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine.

  In a vehicle equipped with an internal combustion engine, the evaporated fuel generated in the fuel tank is once collected in the canister. The collected evaporated fuel is introduced into the intake passage of the internal combustion engine through the purge passage and is combusted in the combustion chamber.

  When such a so-called purge process is executed, air from the purge passage (hereinafter referred to as purge air) and evaporated fuel are introduced into the combustion chamber. The amount of air and the amount of fuel introduced into the chamber increases, and this makes it easy to disturb the air-fuel ratio and the like. Therefore, in order to suppress the disturbance such as the air-fuel ratio, the fuel injection amount is corrected to decrease in accordance with the amount of evaporated fuel when the purge process is executed. Further, the amount of intake air that flows in from the upstream side of the purge passage in the intake passage is corrected to decrease in accordance with the amount of purge air. By correcting the fuel injection amount and the intake air amount, even when the purge process is performed, the same fuel and air as when the purge process is not performed are introduced into the combustion chamber.

In addition, the following patent documents 1 and 2 are mentioned as a prior art document concerning this invention.
Japanese Unexamined Patent Publication No. 6-93901 JP-A-8-121267

  On the other hand, when the amount of intake air is small, such as when the engine is under a low load, the combustion state is likely to be unstable, and misfires are likely to occur. In particular, if the misfire occurs when the engine rotational speed is reduced, such as during deceleration, the engine rotational speed may be excessively reduced in some cases, causing engine stall.

  Therefore, at such a small amount of air, the amount of combustion injection is increased according to the engine load factor calculated from the amount of air introduced into the combustion chamber, and the air-fuel ratio is changed to a slightly richer side than the stoichiometric air-fuel ratio. It is desirable to stabilize the combustion state. In other words, it is desirable to prioritize securing engine output torque over air-fuel ratio control.

  Here, in general, the amount of air introduced into the combustion chamber is determined based on the output value of an intake air amount sensor provided upstream of the throttle valve and the driving amount of a metering mechanism that regulates the intake air amount (for example, a throttle valve or an idle valve). It is detected based on the opening degree of the speed control valve). That is, the intake air amount in the intake passage and upstream of the purge passage is detected, and the detected intake air amount is regarded as the amount of air introduced into the combustion chamber.

  When the purge process is not being performed, the amount of air introduced into the combustion chamber and the detected intake air amount are substantially the same, so the engine load factor is calculated based on the intake air amount. The fuel injection amount increase correction can be appropriately performed.

  On the other hand, when the purge process is executed, the purge air is also introduced into the combustion chamber. Since the amount of purge air is not reflected in the detected intake air amount, the intake air amount is detected to be less than the amount of air actually introduced into the combustion chamber when the purge process is executed. Will be. Therefore, during the execution of the purge process, the load factor obtained from the intake air amount becomes smaller than the actual load factor obtained from the air amount introduced into the combustion chamber, so that a small amount of air at low load or the like is obtained. There is a possibility that the increase correction of the fuel injection amount performed at the time of the amount cannot be appropriately performed.

  The present invention has been made in view of such circumstances, and an object thereof is an internal combustion engine capable of appropriately performing an increase correction of a fuel injection amount executed at a low load even during execution of a purge process. An object of the present invention is to provide a fuel injection control device.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, a purge process for introducing the evaporated fuel generated from the fuel tank into the intake passage through the purge passage is performed, and the intake passage in the intake passage is upstream of the purge passage. An apparatus for controlling a fuel injection amount of an internal combustion engine having a detection means for detecting an air amount, calculating a load factor of the engine based on an intake air amount detected by the detection means, and based on the load factor The gist of the present invention is to include fuel correction means for increasing the fuel injection amount at low engine load, and air amount correction means for increasing the detected intake air amount during execution of the purge process. To do.

  According to this configuration, since the fuel injection amount is corrected to increase when the engine is under a low load, the combustion state can be stabilized even at a low load where the intake air amount decreases, that is, even when the amount of air is small. become.

  By the way, the increase correction of the fuel injection amount is executed in accordance with the engine load factor calculated based on the intake air amount detected by the detecting means. The load factor obtained from the detected intake air amount becomes smaller than the actual load factor obtained from the air amount introduced into the combustion chamber. Therefore, there is a possibility that the increase correction of the fuel injection amount cannot be appropriately performed. In this regard, in the same configuration, the detected intake air amount is corrected to increase while the purge process is being executed. Therefore, the load factor calculated during the purge process is increased by the amount corresponding to the increase correction of the intake air amount, and the load factor obtained from the corrected intake air amount is obtained from the air amount introduced into the combustion chamber. It approaches the actual load factor. Therefore, the fuel injection amount increase correction that is executed at the time of low load can be appropriately performed even during the purge process.

  According to a second aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first aspect, the air amount correction means adds the amount of air introduced into the combustion chamber from the purge passage to the intake air amount. The gist is to do.

  According to this configuration, the amount of the purge air that cannot be detected by the detection unit is added to the intake air amount detected by the detection unit, so that the intake air corrected by the air amount correction unit The amount will be approximately equal to the actual amount of air introduced into the combustion chamber. Therefore, the fuel injection amount increase correction can be performed equally regardless of whether the purge process is executed or not. If the amount of air introduced into the combustion chamber from the purge passage can be accurately grasped, the corrected intake air amount can be matched with the actual amount of air introduced into the combustion chamber.

  According to a third aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the second aspect, the amount of air introduced into the combustion chamber from the purge passage is provided in the purge passage, and the amount of the evaporated fuel is reduced. The gist is that it is estimated from the purge flow rate in the control valve for adjusting the introduction amount.

  The amount of evaporated fuel introduced into the intake passage through the purge passage is normally adjusted by adjusting the opening of a control valve provided in the purge passage, and the more the purge flow rate in the control valve is increased, the more the fuel is burned from the purge passage. The amount of air introduced into the chamber (purge air amount) also increases. Therefore, in the same configuration, the air amount is estimated from such a purge flow rate. Therefore, the amount of purge air added to the intake air amount can be properly grasped.

  According to a fourth aspect of the present invention, there is provided a fuel injection control device for an internal combustion engine according to the third aspect, wherein the purge flow rate is calculated based on an engine load and an engine speed.

  When the engine load and the engine speed are low, the opening of the throttle valve is small, and the negative pressure in the intake passage is large. The purge flow rate increases as the negative pressure in the intake passage increases. Therefore, in the same configuration, the purge flow rate is calculated based on the engine load and the engine rotation speed, and the purge flow rate can be estimated appropriately.

  In the invention according to claim 3, the amount of purge air to be added to the intake air amount is estimated from the purge flow rate. In the configuration according to claim 4, the purge flow rate is determined by the engine load and the engine load. Calculated based on the engine speed. Accordingly, the amount of purge air to be added to the intake air amount can be indirectly determined based on the engine load and the engine speed.

  According to a fifth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to fourth aspects, the fuel correction means determines that the engine is decelerating at the time of the low load. Then, the gist is to execute the increase correction.

  As described above, in a situation where the intake air amount is small, such as when the engine is under a low load, the combustion state tends to become unstable, and misfires are likely to occur. In particular, if a misfire occurs while the engine rotational speed is decreasing, such as during engine deceleration, the engine rotational speed may be excessively decreased in some cases, causing engine stall. In this respect, in the same configuration, since the increase correction of the fuel injection amount is executed when the engine is decelerated, the occurrence of misfire during the deceleration can be suppressed. Further, it is possible to suitably suppress the occurrence of such misfire even during the execution of the purge process.

  Whether or not the engine is in a decelerating state is determined according to the invention described in claim 6, in which at least one of the reduction amount of the intake air amount and the reduction amount of the engine rotational speed is a predetermined value. By adopting a configuration in which it is determined that the vehicle is decelerating when exceeding the value, it can be appropriately determined.

  As the detection means for detecting the intake air amount upstream of the purge passage in the intake passage, an intake air amount sensor provided on the upstream side of the throttle valve is employed as in the invention according to claim 7. be able to.

  Further, as the detection means, a configuration in which the intake air amount is estimated based on a driving amount of a metering mechanism that measures the intake air amount can be adopted as in the invention described in claim 8. . The drive amount of the metering mechanism includes, for example, the opening degree of the throttle valve. In addition, if the intake passage has a bypass pipe that connects the upstream side and the downstream side of the throttle valve and includes an idle speed control valve that regulates the amount of air passing through the bypass pipe, The opening degree of the speed control valve can also be cited as the driving amount of the metering mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying a fuel injection control device for an internal combustion engine according to the present invention will be described below with reference to FIGS.
FIG. 1 shows a schematic configuration of an internal combustion engine 10 to which a fuel injection control device according to the present embodiment is applied.

  As shown in FIG. 1, an internal combustion engine 10 includes a fuel injection valve 12 that injects fuel into a combustion chamber 11 and an ignition plug that ignites an air-fuel mixture that is a mixture of the injected fuel and intake air. 13 etc. are provided.

  An intake passage 14 and an exhaust passage 15 are connected to the combustion chamber 11. A surge tank 16 is provided in the middle of the intake passage 14, and a throttle valve 17 for adjusting the intake air amount is further provided on the upstream side thereof.

  On the other hand, the internal combustion engine 10 is provided with an evaporated fuel processing device 30. The evaporative fuel processing device 30 includes a canister 31 connected to the fuel tank 21 via a vapor passage 32, a purge passage 33 connecting the canister 31 and the surge tank 16, and air introduction for introducing air into the canister 31. The passage 34 and the purge control valve 35 that opens and closes the purge passage 33 are configured.

  The evaporated fuel generated in the fuel tank 21 is introduced into the canister 31 from the fuel tank 21 through the vapor passage 32, and is once adsorbed by the adsorbent provided therein. When the purge control valve 35 is opened, air is introduced into the canister 31 through the atmosphere introduction passage 34. When air is introduced into the canister 31 in this way, the evaporated fuel adsorbed in the canister 31 is introduced into the surge tank 16 through the purge passage 33 together with purge air containing the evaporated fuel. The evaporated fuel introduced into the surge tank 16 is combusted in the combustion chamber 11 together with the fuel injected from the fuel injection valve 12.

  The amount of evaporated fuel to be purged in this way is adjusted through the opening control of the purge control valve 35. The purge control valve 35 is an electromagnetic valve whose opening degree is controlled by an electric signal, more specifically, a duty signal. Basically, the purge air amount increases as the opening of the purge control valve 35 increases and as the negative pressure in the intake passage 14 increases. Based on this, during the purge process, the opening degree of the purge control valve 35 is adjusted in accordance with the engine operating state, whereby the evaporated fuel adsorbed on the canister 31 is processed efficiently.

  The electronic control unit 40 performs purge control for executing such purge processing, fuel injection control of the fuel injection valve 12, air-fuel ratio control of the air-fuel mixture, and the like. The electronic control unit 40 includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a backup RAM, an external input circuit, an external output circuit, and the like. Then, in order to execute the various controls as described above according to the operating state of the internal combustion engine 10, signals of various sensors that detect the operating state and the like are input.

  For example, the electronic control device 40 detects the exhaust air sensor 51 provided in the exhaust passage 15 for detecting the oxygen concentration in the exhaust gas (air-fuel ratio of the air-fuel mixture) and the intake air amount Qa introduced into the combustion chamber 11. The detection signal of the air flow meter 52 is input. In addition, a crank angle sensor 53 that detects the rotation angle of the crankshaft and detects the engine rotational speed NE based on the detection signal, a throttle sensor 54 that detects the opening of the throttle valve 17 (throttle opening TA), an internal combustion engine Detection signals from the water temperature sensor 55 and the like that detect the 10 cooling water temperature THW are also input to the electronic control unit 40, respectively. Based on the operating state of the internal combustion engine 10 and the running state of the vehicle detected by these sensors 51 to 55, etc., the electronic control unit 40 becomes the purge control, the fuel injection control, and the desired air-fuel ratio for executing the purge process. Thus, various controls such as air-fuel ratio feedback control for increasing or decreasing the fuel injection amount with the feedback correction amount are executed.

  By the way, as shown in FIG. 2, the air amount Qc (total intake air amount Qc) introduced into the combustion chamber 11 during execution of the purge process is the amount of air metered by the throttle valve 17, that is, the intake passage 14. The sum of the intake air amount Qa flowing in from the upstream side of the purge passage 33 and the amount of air introduced from the purge passage 33 into the intake system, that is, the purge air amount Qb. Further, the amount of fuel introduced into the combustion chamber during execution of the purge process is the sum of the amount of fuel injected from the fuel injection valve 12 and the amount of evaporated fuel introduced into the intake system from the purge passage 33.

  Thus, during execution of the purge process, since purge air and evaporated fuel are introduced into the combustion chamber 11, the amount of fuel introduced into the combustion chamber 11 compared to when the process is not performed. In addition, the air amount increases, and the air-fuel ratio and the like are easily disturbed.

  Therefore, in order to suppress the disturbance of the air-fuel ratio or the like, the actual intake air amount Qa and the fuel injection amount are corrected to be reduced during the purge process. Air and fuel equivalent to those at the time of execution are introduced into the combustion chamber 11.

  When correcting the intake air amount Qa, the opening of the throttle valve 17 is corrected to the decreasing side based on the duty ratio of the control signal for controlling the opening of the purge control valve 35. Thereby, the intake air amount Qa during the purge process is corrected to decrease in accordance with the purge air amount Qb.

  When correcting the fuel injection amount, the purge air flow rate estimated from the opening degree of the purge control valve 35 and the like, and the fuel concentration in the purge air estimated based on the change in the air-fuel ratio after the start of the purge process, The amount of fuel in the purge air is calculated based on this, and the amount of fuel injected from the fuel injection valve 12 is corrected to decrease by the calculated amount of fuel in the purge air.

  When evaporated fuel is introduced into the intake system, the air-fuel ratio detected by the exhaust sensor 51 changes to the rich side, and this change is reflected in the feedback correction amount in the air-fuel ratio feedback control. Therefore, the fuel concentration in the purge air can be estimated based on the air-fuel ratio when the purge control valve 35 is opened, in other words, the change in the feedback correction amount after the purge process is started (change in the air-fuel ratio). .

  On the other hand, when the amount of intake air introduced into the combustion chamber 11 is small, such as when the engine is under a low load, the combustion state tends to be unstable and misfires are likely to occur. In particular, if the misfire occurs when the engine rotational speed is reduced, such as during deceleration, the engine rotational speed may be excessively reduced in some cases, causing engine stall.

  Therefore, when the amount of air is small, the fuel increasing process described below is performed to change the air / fuel ratio to a slightly richer side than the stoichiometric air / fuel ratio so as to stabilize the combustion state. Yes. In other words, when the amount of air is small, priority is given to securing the output torque of the engine over the control of the air-fuel ratio.

  FIG. 3 shows the processing procedure for the fuel increase processing when the amount of air is small. This process is repeatedly executed by the electronic control device 40 every predetermined period. Further, this process constitutes the fuel correction means.

  When this process is started, first, the corrected intake air amount Qah is read (S100). The corrected intake air amount Qah is a value obtained by correcting the intake air amount Qa detected by the air flow meter 52, and the correction mode will be described in an intake air amount correction process described later.

  Next, it is determined whether or not the engine is decelerating (S110). Here, when the reduction amount of the corrected intake air amount Qah exceeds a predetermined determination value, or when the decrease amount of the engine speed NE exceeds a predetermined determination value, it is determined that the vehicle is decelerating. When the amount of decrease in the corrected intake air amount Qah exceeds a predetermined determination value and when the decrease amount of the engine speed NE exceeds a predetermined determination value, it is determined that the vehicle is decelerating. Also good.

And when it determines with it not being at the time of deceleration (S110: NO), this process is once complete | finished.
On the other hand, when it is determined that the vehicle is decelerating (S110: YES), the engine load factor L is calculated from the corrected intake air amount Qah (S120), and based on the load factor L and the engine speed NE. An increase correction coefficient K (0 ≦ K ≦ 1) for the fuel injection amount T is calculated (S130).

  As shown in FIG. 4, the increase correction coefficient K is set such that the value decreases as the load factor L increases. In other words, the corrected intake air amount Qah is set so as to decrease as the corrected intake air amount Qah decreases. As a result, the fuel injection amount increases as the intake air amount introduced into the combustion chamber 11 decreases. Further, as shown in FIG. 5, the increase correction coefficient K is set such that its value increases as the engine rotational speed NE increases, and the same value starts to decrease when it exceeds a predetermined rotational speed. As a result, the fuel injection amount is increased in accordance with the state of decrease in the engine speed during deceleration. It should be noted that the manner of setting the increase correction coefficient K shown in FIG. 4 and FIG. 5 is an example, and in short, an appropriate increase correction coefficient K that makes the combustion state of the air-fuel mixture good is set.

  When the increase correction coefficient K is calculated in this way, the fuel injection amount T set in accordance with the engine operating state is corrected with the increase correction coefficient K based on the following equation (1) (S140), and this process is temporarily terminated. The

Corrected fuel injection amount T ← Uncorrected fuel injection amount T
+ (Fuel injection amount T before correction T × increase correction coefficient K) (1)

The fuel injection amount T that has been corrected to increase in this way becomes the amount of fuel injected from the fuel injection valve 12 during deceleration.

Next, the reason why the corrected intake air amount Qah is used in the deceleration determination in step S110 and the calculation of the load factor L in step S120 will be described below.
In general, the amount of air introduced into the combustion chamber 11 is detected based on the output value of an air flow meter 52 provided upstream of the throttle valve 17. That is, the intake air amount Qa in the intake passage 14 upstream of the purge passage 33 is detected, and the detected intake air amount Qa is regarded as the amount of air introduced into the combustion chamber 11.

  When the purge process is not executed, the total intake air amount Qc, which is the amount of air introduced into the combustion chamber 11, substantially coincides with the detected intake air amount Qa.

  On the other hand, during the purge process, the purge air is also introduced into the combustion chamber 11. The purge air amount Qb, which is the amount of purge air, is not reflected in the intake air amount Qa detected by the air flow meter 52. That is, the purge air amount Qb cannot be detected by the air flow meter 52, and the intake air amount Qa detected during the purge process is smaller than the total intake air amount Qc. For this reason, if the above-described fuel increase processing at the time of a small air amount is executed based on the intake air amount Qa, for example, the following inconvenience may occur.

First, when the purge process is not executed, the increase correction of the fuel injection amount can be appropriately performed by calculating the load factor of the engine based on the intake air amount Qa.
On the other hand, during the execution of the purge process, the intake air amount Qa is detected to be smaller by the amount of purge air amount Qb than the amount of air actually introduced into the combustion chamber 11 (total intake air amount Qc). Accordingly, during the execution of the purge process, the load factor obtained from the intake air amount Qa becomes smaller than the actual load factor obtained from the total intake air amount Qc introduced into the combustion chamber 11, as described above. Therefore, there is a problem that it becomes impossible to appropriately perform the increase correction of the fuel injection amount T that is performed at the time of slow deceleration.

  Further, as described above, in the reduction correction of the intake air amount Qa performed during the execution of the purge process, the reduction correction amount of the intake air quantity Qa changes according to the purge air amount Qb introduced in the purge process. . Therefore, the change in the total intake air amount Qc and the change in the intake air amount Qa do not necessarily match. For example, even if the total intake air amount Qc is the same, if the purge air amount Qb changes, the change is detected by the air flow meter 52. The value of the intake air amount Qa to be changed changes. Here, the fuel increase correction at the time of the small air amount is determined to be executable based on the decrease amount of the intake air amount Qa at the time of deceleration. Therefore, in some cases, even though the total intake air amount Qc does not change so much, the inconvenience that the execution of the fuel increase correction is permitted due to the change in the intake air amount Qa during execution of the purge process. It will occur. That is, there is a problem in that it is not possible to appropriately determine whether or not the fuel increase correction at the time of the small air amount can be executed, and an unnecessary fuel increase may be performed.

  In addition, in the air-fuel ratio feedback control, when the fuel injection amount is excessively increased or decreased and the amount is out of the possible range of the feedback control, the execution of the feedback control is once stopped. Here, as described above, the change in the total intake air amount Qc and the change in the intake air amount Qa do not necessarily coincide with each other during the execution of the purge process. For this reason, the increase correction of the fuel injection amount T, which should be originally performed in accordance with the change in the total intake air amount Qc at the time of deceleration, is not normally performed, and there is a concern that in some cases the following hunting phenomenon occurs. Is done.

  First, when the purge control valve 35 is opened and purge air is introduced, the intake air amount Qa is corrected to decrease, and the fuel injection amount T is corrected to increase through the fuel increase process. Here, if the change rate of the intake air amount Qa is large with respect to the change of the total intake air amount Qc, and thus the corrected fuel injection amount T is excessively increased, the air-fuel ratio feedback control is stopped. When the air-fuel ratio feedback control is stopped, the concentration of the evaporated fuel cannot be estimated based on the feedback correction amount, so the purge control valve 35 is closed and the purge process is temporarily stopped. On the other hand, when the purge process is stopped in this way, the introduction amount of the purge air amount Qb becomes “0”, so that the reduction correction amount of the intake air amount Qa is decreased, and thus the intake air amount Qa is increased. become. When the intake air amount Qa increases in this way, the corrected fuel injection amount T is decreased. When the reduced fuel injection amount T returns to the possible range of the feedback control, the air-fuel ratio feedback control is resumed, the purge control valve 35 is opened, and the purge process is started again. Thus, when the change rate of the intake air amount Qa is large with respect to the change of the total intake air amount Qc, various factors such as increase / decrease of the fuel injection amount T, stop / restart of the air-fuel ratio feedback control, stop / restart of the purge process, etc. The hunting phenomenon will occur.

  Therefore, in the present embodiment, the intake air amount Qa detected by the air flow meter 52 is corrected to increase during execution of the purge process so that the value corresponds to the total intake air amount Qc. Further, the above-described inconveniences and the like are suppressed through such correction processing, so that the increase correction of the fuel injection amount T, which is executed at a low load, particularly at the time of deceleration, is appropriately performed even during the purge processing. To be able to.

  FIG. 6 shows a processing procedure for the intake air amount correction processing for increasing the intake air amount Qa. This process is also repeatedly executed by the electronic control device 40 at predetermined intervals. Further, this process constitutes the air amount correcting means.

When this process is started, first, the intake air amount Qa detected by the air flow meter 52, the throttle opening degree TA, and the engine speed NE are read (S200).
Next, the estimated intake air amount Qas is calculated based on the intake air amount Qa and the throttle opening degree TA (S210). This estimated intake air amount Qas is an estimated air amount that compensates for a response delay when the intake air amount Qa changes, and in this embodiment, the intake air that should have been introduced into the combustion chamber 11 at the fuel injection timing. The air amount Qa is predicted. By calculating the estimated value in which the response delay of the intake air amount is compensated in this way, the response delay of the intake air amount can be taken into account when increasing the fuel injection amount T.

  Next, the basic load factor Lb of the engine is calculated based on the estimated intake air amount Qas (S220), and the amount of purge air passing through the purge control valve 35 based on the basic load factor Lb and the engine rotational speed NE, in other words, Then, the purge flow rate PV is calculated (S230). The purge flow rate PV is estimated in the following manner.

  That is, when the engine load and the engine speed are low, the opening degree of the throttle valve 17 is small, and the negative pressure in the intake passage 14 is large. The purge flow rate PV increases as the negative pressure in the intake passage 14 increases. Therefore, the purge flow rate PV is calculated based on the engine load and the engine speed. In this calculation, as shown in FIG. 7, the purge flow rate PV is estimated so that the calculated purge flow rate PV increases as the basic load factor Lb decreases. Further, as shown in FIG. 8, the purge flow rate PV is estimated such that the purge flow rate PV calculated becomes larger as the engine speed NE becomes lower, so that the purge flow rate PV is appropriately estimated. Note that the estimation mode of the purge flow rate PV shown in FIGS. 7 and 8 is an example, and the estimation mode is determined through experiments or the like so that the purge flow rate PV is appropriately set based on the basic load factor Lb and the engine rotation speed NE. Should be set.

  Next, the purge air amount Qb is calculated based on the purge flow rate PV (S240). That is, the amount of evaporated fuel introduced into the intake system via the purge passage 33 is normally adjusted by adjusting the opening of the purge control valve 35, and the purge flow PV at the purge control valve 35 increases as the purge flow rate PV increases. The amount of air introduced into the combustion chamber 11 from the passage 33, that is, the purge air amount Qb also increases. Therefore, in step S240, the purge air amount Qb is estimated based on the purge flow rate PV. While the purge process is being executed, the purge air amount Qb is estimated based on the purge flow rate PV, while when the purge process is not being executed, the purge air quantity Qb is set to “0”. .

When the purge air amount Qb is calculated in this way, the corrected intake air amount Qah is calculated from the following equation (2) (S250), and this process is temporarily terminated.

Corrected intake air amount Qah ← estimated intake air amount Qas + purge air amount Qb (2)

Thus, in this process, the intake air amount Qa detected by the air flow meter 52, more specifically, the estimated intake air amount Qas estimated from the intake air amount Qa is introduced into the combustion chamber 11 from the purge passage 33. A corrected intake air amount Qah obtained by adding the purge air amount Qb is calculated. That is, the purge air amount Qb that cannot be detected by the air flow meter 52 is added to the estimated intake air amount Qas. Therefore, the corrected intake air amount Qah substantially coincides with the actual air amount introduced into the combustion chamber 11 (the total intake air amount Qc). Incidentally, if the purge air amount Qb can be accurately grasped, the corrected intake air amount Qah can be matched with the actual air amount introduced into the combustion chamber 11.

  Since the fuel increase correction at the time of the small air amount is executed based on the intake air amount Qa corrected in this way, the increase correction of the fuel injection amount T is equal regardless of whether the purge process is executed or not. The above-described inconvenience can be suppressed.

  That is, the load factor L obtained from the corrected intake air amount Qah during execution of the purge process is equal to the actual load factor L obtained from the total intake air amount Qc introduced into the combustion chamber 11, and is therefore implemented during deceleration. The increase correction of the fuel injection amount T to be performed can be performed appropriately.

  Even if the intake air amount Qa changes with the change in the purge air amount Qb, the corrected intake air amount Qah does not change so much if the total intake air amount Qc itself does not change so much. Therefore, in this case, it is determined in step S110 that “not at deceleration”. As described above, by determining whether or not the vehicle is decelerating using the corrected intake air amount Qah, it is possible to appropriately determine whether or not the fuel increase correction at the time of a small air amount can be executed. become.

  Even if the change rate of the intake air amount Qa is large with respect to the change of the total intake air amount Qc, if the change amount of the total intake air amount Qc itself is small, the change amount of the corrected intake air amount Qah is also increased. Less. Therefore, even when the change rate of the intake air amount Qa is large, the corrected fuel injection amount T is not excessively increased, and thus the increase / decrease in the fuel injection amount T, air-fuel ratio feedback control as described above. Occurrence of various hunting phenomena such as stop and restart of the purge process, and stop and restart of the purge process are also suppressed.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The engine load factor L is calculated based on the estimated intake air amount Qas calculated based on the intake air amount Qa and the throttle opening TA, and the engine load factor L is calculated based on the load factor L. Specifically, the fuel injection amount T during deceleration is corrected to increase. For this reason, the combustion state can be stabilized even at a low load when the intake air amount is reduced, that is, at a small air amount. Further, during the purge process, the estimated intake air amount Qas is increased and corrected. Therefore, the increase correction of the fuel injection amount T executed at the time of deceleration can be appropriately performed even while the purge process is being executed.

  (2) In the increase correction of the estimated intake air amount Qas, the purge air amount Qb introduced from the purge passage 33 into the combustion chamber 11 is added to the estimated intake air amount Qas. Therefore, the corrected estimated intake air amount Qas substantially coincides with the actual air amount introduced into the combustion chamber 11 (total intake air amount Qc). Therefore, the increase correction of the fuel injection amount T can be performed equally regardless of whether or not the purge process is executed.

  (3) The purge air amount Qb introduced into the combustion chamber 11 from the purge passage 33 is estimated from the purge flow rate PV in the purge control valve 35. Therefore, the purge air amount Qb added to the estimated intake air amount Qas can be properly grasped.

(4) The purge flow rate PV is calculated based on the basic load factor Lb and the engine speed NE. Therefore, the purge flow rate PV can be estimated appropriately.
Further, as described above, the purge air amount Qb to be added to the estimated intake air amount Qas is estimated from the purge flow rate PV, and this purge flow rate PV is calculated based on the basic load factor Lb and the engine speed NE. Therefore, the purge air amount Qb to be added to the estimated intake air amount Qas can also be obtained indirectly based on the basic load factor Lb and the engine speed NE.

  (5) As described above, in a situation where the intake air amount is small, such as when the engine is under a low load, the combustion state is likely to be unstable, and misfire is likely to occur. In particular, if a misfire occurs while the engine rotational speed is decreasing, such as during engine deceleration, the engine rotational speed may be excessively decreased in some cases, causing engine stall. In this regard, in this embodiment, it is determined that the engine is decelerating when the load is low, and an increase correction of the fuel injection amount T is executed. Therefore, the occurrence of misfire during deceleration can be suppressed. Further, it is possible to suitably suppress the occurrence of such misfire even during the execution of the purge process.

  (6) When at least one of the decrease amount of the estimated intake air amount Qas and the decrease amount of the engine speed NE exceeds a predetermined value, it is determined that the vehicle is decelerating. Accordingly, it is possible to appropriately determine whether or not the engine is in a deceleration state.

In addition, the said embodiment can also be changed and implemented as follows.
In the intake air amount correction process, the purge air amount Qb is added to the estimated intake air amount Qas when increasing the estimated intake air amount Qas. In addition, during the purge process, the estimated intake air amount Qas may be corrected to increase by adding or multiplying the estimated intake air amount Qas by an appropriate coefficient. Even in this case, the load factor L calculated during the execution of the purge process is increased by the increase correction of the intake air amount, and the load factor L obtained from the corrected intake air amount is introduced into the combustion chamber 11. It approaches the actual load factor L obtained from the air amount. Therefore, the increase correction of the fuel injection amount T executed at the time of low load can be appropriately performed even while the purge process is being executed.

  In calculating the corrected intake air amount Qah, the estimated intake air amount Qas is calculated based on the intake air amount Qa and the throttle opening degree TA, but it is not always necessary to calculate the estimated intake air amount Qas. For example, the corrected intake air amount Qah may be obtained by adding the purge air amount Qb to the intake air amount Qa detected by the air flow meter 52.

  In the fuel increase process performed when the amount of air is small, an increase correction of the fuel injection amount T is performed when the engine is decelerated. However, an increase correction of the fuel injection amount T is performed when the amount of air is small during other low loads. May be performed.

  Although the purge air amount Qb is obtained from the purge flow rate PV, the purge air amount Qb may be estimated from the opening degree of the purge control valve 35, the purge rate (ratio of the purge amount to the intake air amount), and the like. . Further, the purge air amount may be directly detected using a sensor or the like.

  The intake air amount Qa in the intake passage 14 and upstream of the purge passage 33 is detected by the air flow meter 52, but the intake air amount Qa may be obtained using other detection means. . For example, the intake air amount Qa may be estimated based on the pressure in the intake passage 14. Further, the intake air amount Qa may be estimated based on a drive amount of a metering mechanism that regulates the intake air amount. In this case, the drive amount of the metering mechanism includes, for example, the opening degree of the throttle valve 17. In addition, if the intake passage has a bypass pipe that connects the upstream side and the downstream side of the throttle valve and includes an idle speed control valve that regulates the amount of air passing through the bypass pipe, The opening degree of the speed control valve can also be cited as the driving amount of the metering mechanism.

  While the purge process is being executed, the actual intake air amount Qa is corrected to decrease in accordance with the purge air amount Qb, but the present invention applies in the same manner even when the decrease correction is not performed. be able to.

  When this reduction correction is not performed, the total intake air amount Qc during the purge process is increased by the purge air amount Qb. Here, when the present invention is not carried out, the load factor L corresponding to the increased total intake air amount Qc cannot be calculated, and thus the increase correction of the fuel injection amount T performed when the amount of air is small. May not be performed properly. On the other hand, if the present invention is implemented, the load factor L corresponding to the increased total intake air amount Qc can be calculated, so that the increase correction of the fuel injection amount T can be appropriately performed.

  ・ In the air-fuel ratio feedback control, when the fuel injection amount is excessively increased or decreased and the amount falls outside the possible range of the feedback control, the execution of the feedback control is once stopped. Even if this processing is not performed, the present invention can be similarly applied.

  The present invention can be similarly applied not only to a gasoline engine equipped with a spark plug but also to a diesel engine.

1 is a configuration diagram of an internal combustion engine to which an embodiment of a fuel injection control device for an internal combustion engine according to the present invention is applied. FIG. The schematic diagram which shows the air flow in an intake passage during purge processing execution. The flowchart which shows the process sequence about the fuel increase process at the time of the small air quantity in the embodiment. The graph which shows the correspondence of the engine load factor and the increase correction coefficient. The graph which shows the correspondence of an engine speed and an increase correction coefficient. The flowchart which shows the process sequence about the intake air amount correction | amendment process in the embodiment. The graph which shows the correspondence of a basic load factor and a purge flow rate. The graph which shows the correspondence of an engine speed and a purge flow rate.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Combustion chamber, 12 ... Fuel injection valve, 13 ... Spark plug, 14 ... Intake passage, 15 ... Exhaust passage, 16 ... Surge tank, 17 ... Throttle valve, 21 ... Fuel tank, 30 ... Evaporated fuel Processing unit 31 ... Canister 32 ... Vapor passage 33 ... Purge passage 34 ... Air introduction passage 35 ... Purge control valve 40 ... Electronic control device 51 ... Exhaust sensor 52 ... Air flow meter 53 ... Crank angle sensor 54 ... throttle sensor, 55 ... water temperature sensor.

Claims (8)

A purge process for introducing the evaporated fuel generated from the fuel tank into the intake passage through the purge passage is performed, and a detection means for detecting the intake air amount in the intake passage and upstream of the purge passage is provided. An apparatus for controlling the fuel injection amount of an internal combustion engine,
Fuel correction means for calculating the load factor of the engine based on the intake air amount detected by the detection means, and for increasing the fuel injection amount at low load of the engine based on the load factor;
The fuel injection control device for an internal combustion engine, comprising: an air amount correction unit that increases and corrects the detected intake air amount during execution of the purge process. The fuel injection control device for an internal combustion engine according to claim 1, wherein the air amount correction means adds the amount of air introduced into the combustion chamber from the purge passage to the intake air amount. 3. The internal combustion engine according to claim 2, wherein the amount of air introduced into the combustion chamber from the purge passage is estimated from a purge flow rate at a control valve that is provided in the purge passage and adjusts the introduction amount of the evaporated fuel. Fuel injection control device. The fuel injection control device for an internal combustion engine according to claim 3, wherein the purge flow rate is calculated based on an engine load and an engine speed. 5. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel correction unit performs the increase correction by determining that the engine is decelerating when the engine is decelerating. 6. The fuel injection control for an internal combustion engine according to claim 5, wherein the fuel correction means determines that the vehicle is decelerating when at least one of a reduction amount of the intake air amount and a reduction amount of the engine speed exceeds a predetermined value. apparatus. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 6, wherein the detection means is an intake air amount sensor provided upstream of the throttle valve. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 7, wherein the detection means estimates an intake air amount based on a drive amount of a metering mechanism that regulates the intake air amount.

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