JP2009138620A - Control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an internal combustion engine capable of preventing fluctuation of an air-fuel ratio due to change in evaporation amount of fuel adhering to intake-side equipments and suppressing an exhaust amount of unburned gas. <P>SOLUTION: The control device 30 of the internal combustion engine 10 includes a fuel injection amount calculation means 101 for calculating a fuel injection amount TP of the internal combustion engine, a rotation fluctuation amount calculating means 102 for calculating a rotation fluctuation amount DN of the internal combustion engine, a fuel injection amount increase/decrease setting means 103 for setting an increase rate of the fuel injection amount TP when the rotation fluctuation amount DN exceeds a predetermined threshold value and for setting a decrease rate of the fuel injection amount TP when the rotation fluctuation amount DN is equal to or less than the predetermined threshold value, and a fuel injection amount correction means 104 for correcting the fuel injection amount based on the increase rate or the decrease rate. The fuel injection amount increase/decrease setting means 103 changes the increase rate or the decrease rate based on the time elapsed after the start, the number of times of ignition or an integrated value of load of the internal combustion engine 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine that controls a fuel injection amount when starting the internal combustion engine.

  The fuel injected into the internal combustion engine does not easily evaporate at the time of cold start, and the evaporation characteristics tend to vary. In particular, when the internal combustion engine is started using heavy gasoline as the fuel, a large amount of fuel injected to the intake port wall surface and intake valve adheres. Due to the adhesion, the amount of fuel that should be introduced into the cylinder is reduced, and the air-fuel mixture in the cylinder becomes lean. As a result, when the air-fuel mixture is ignited in the lean state, the combustion state deteriorates, the amount of unburned gas discharged increases, and the internal combustion engine tends to fluctuate. In addition, due to variations in the characteristics of components such as the fuel injection valve, the air flow meter for measuring the intake air amount, or the intake pipe pressure sensor, the air-fuel mixture in the cylinder may become lean and cause the same problems as described above.

  In view of these points, when using heavy gasoline, in order to prevent problems caused by leaning of the air-fuel mixture, the fuel injection amount that is actually injected is set to be greater than the target fuel injection amount. It is possible to increase the amount. However, when an internal combustion engine is started using light gasoline or standard gasoline, these gasolines are more likely to evaporate than heavy gasoline. For this reason, if the fuel injection amount is simply increased, the air-fuel mixture introduced into the cylinder becomes over-rich with respect to the stoichiometric air-fuel ratio (stoichio), and the unburned gas (HC) that combusted the air-fuel mixture. Emissions will increase.

  In order to solve the above-mentioned problem, for example, Patent Document 1 discloses the following control device for an internal combustion engine in order to prevent fluctuations in the air-fuel ratio due to variations in fuel properties and component characteristics. The control device pays attention to the fact that the fluctuation of the air-fuel ratio depends on the fluctuation amount (rotational fluctuation amount) of the rotational speed of the internal combustion engine, estimates the air-fuel ratio based on the rotational fluctuation amount after starting the internal combustion engine, and By controlling the fuel injection amount based on the amount, the air-fuel ratio is prevented from being overlean or overrich immediately after starting.

  More specifically, the control device of the internal combustion engine suppresses over leaning of the air-fuel ratio by performing correction to increase the fuel injection amount at a predetermined ratio when the rotational fluctuation amount is larger than a predetermined threshold value, When the rotational fluctuation amount is smaller than a predetermined threshold value, over-riching is suppressed by performing correction for reducing the fuel injection amount at a predetermined rate.

Japanese Patent Laid-Open No. 10-18422

  The control device for an internal combustion engine described in Patent Document 1 uses the rotation fluctuation amount of the internal combustion engine as an index for controlling the air-fuel ratio. However, generally, even when the air-fuel ratio is constant, there may be variations in the rotational fluctuation amount. Therefore, the control device for the internal combustion engine corrects the fuel injection amount based on an index that averages the rotational fluctuation amount. Or the correction amount of the fuel injection amount with respect to the rotational fluctuation amount is reduced to reduce the influence of the variation of the rotational fluctuation amount.

  For this reason, when the air-fuel ratio fluctuates with time, there may be a time delay between the change of the air-fuel ratio and the correction of the fuel injection amount based on the rotation fluctuation amount. As a result, when the fuel correction control based on the rotational fluctuation is performed, the air-fuel ratio fluctuation is reduced as compared with the case where the fuel correction based on the rotational fluctuation is not performed, but the fuel correction control is affected by a delay of the fuel correction.

  Here, as shown in FIG. 7, immediately after the engine is cold-started (section 1), as described above, the temperature of the intake valve and intake port corresponding to the intake side of the internal combustion engine is low and adheres to the intake valve and intake port. A large proportion of fuel. For this reason, the fuel contained in the air-fuel mixture supplied to the cylinder tends to be insufficient, and the air-fuel ratio of the cylinder tends to lean as shown by the dotted line. Here, the broken line indicates the air-fuel ratio (cylinder air-fuel ratio) of the air-fuel mixture in the cylinder when the fuel injection is performed with a predetermined fuel injection amount without correcting the fuel injection amount based on the rotational fluctuation amount.

  And if time passes after cold start, the temperature of an intake valve or an intake port will rise gradually (section 2). At this time, the fuel adhering to the intake valve or intake port corresponding to the intake side of the internal combustion engine evaporates immediately after starting. Due to the increase in the evaporation amount of fuel accompanying the temperature rise, the evaporated fuel flowing into the cylinder increases until the fuel adhesion amount reaches an equilibrium state, and the air-fuel ratio in the cylinder in the section 2 becomes rich as indicated by the dotted line. Change.

  In this way, when correcting the fuel injection amount based on the rotation fluctuation amount, as shown in FIG. 8, the correction is performed so that the fuel is increased when the rotation fluctuation amount exceeds the threshold value SLDN. Is corrected to reduce the fuel when is below the threshold. In section 1, since the rotation fluctuation amount often exceeds a predetermined threshold value, correction for increasing the fuel injection amount is performed, and leaning of the cylinder air-fuel ratio is suppressed.

  On the other hand, in the section 2, the amount of fuel on the intake side attached in the section 1 increases, so that the cylinder inflow fuel amount (broken line) increases compared to the case where the fuel evaporation amount is small (solid line). The cylinder air-fuel ratio changes to the rich side. As a result, when the fuel evaporation amount increases and the air-fuel ratio becomes rich, the rotational fluctuation amount also decreases.

  However, even when such correction is performed, empirically, the amount of fuel flowing into the cylinder due to the increase in fuel evaporation when the wall temperature rises, while the fuel increase correction frequency due to the decrease in rotational fluctuation is reduced. The rate of increase of the engine is larger. On average, the amount of fuel flowing into the cylinder increases, and the air-fuel ratio changes in a rich direction beyond the stoichiometric state. In FIG. 8, for the sake of convenience, the rotational fluctuation amount is illustrated as the same condition so that the fuel evaporation amount is large and the fuel evaporation amount is easy to compare.

  Even when the correction is performed as described above, the amount of fuel adhering to the intake valve increases as the intake side temperature of the intake valve, intake port, etc. In section 2 shown in FIG. 7, the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio (stoichio), and there is a problem that the amount of unburned gas (HC) discharged increases.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to prevent fluctuations in the air-fuel ratio due to an increase in the amount of fuel evaporation accompanying a rise in temperature on the intake side such as an intake valve and an intake port. And it aims at providing the control apparatus of the internal combustion engine which can suppress the discharge | emission amount of unburned gas.

  In order to solve the above problems, an internal combustion engine control apparatus according to the present invention includes a fuel injection amount calculation means for calculating a fuel injection amount of the internal combustion engine, a rotation fluctuation amount calculation means for calculating a rotation fluctuation amount of the internal combustion engine, A fuel injection amount increase / decrease amount that sets an increase rate of the fuel injection amount when the rotational fluctuation amount exceeds a predetermined threshold value, and sets a decrease rate of the fuel injection amount when the rotation fluctuation amount is equal to or less than the predetermined threshold value. A control device for an internal combustion engine, comprising: setting means; and a fuel injection amount correction means for correcting the fuel injection amount based on the increase ratio or the decrease ratio, wherein the fuel injection amount increase / decrease setting means includes: The increase ratio or the decrease ratio is changed based on the elapsed time from the start of the internal combustion engine, the number of ignitions, or the engine load integrated value.

  The control apparatus for an internal combustion engine according to the present invention includes a fuel injection amount calculation unit that calculates a fuel injection amount of the internal combustion engine, a rotation variation amount calculation unit that calculates a rotation variation amount of the internal combustion engine, and the rotation variation amount is a predetermined amount. A fuel injection amount increase / decrease setting means for setting an increase rate of the fuel injection amount when a threshold value is exceeded, and a decrease rate of the fuel injection amount when it is equal to or less than the predetermined threshold; and the increase rate Or a fuel injection amount correction unit that corrects the fuel injection amount based on a reduction rate, wherein the fuel injection amount increase / decrease setting unit sets the threshold value to the internal combustion engine. The change is made based on the elapsed time from the start of the engine, the number of ignitions, or the engine load integrated value.

  The control apparatus for an internal combustion engine according to the present invention provides the fuel injection amount increase / decrease setting means when the elapsed time, the number of ignition times, or the engine load integrated value exceeds a predetermined value, The increase ratio of the quantity is reduced.

  The control apparatus for an internal combustion engine according to the present invention provides the fuel injection amount increase / decrease setting means when the elapsed time, the number of ignition times, or the engine load integrated value exceeds a predetermined value, It is characterized in that the amount of weight reduction is increased.

  When the elapsed time, the number of ignitions, or the integrated value of the engine load exceeds a predetermined value, the control device for an internal combustion engine according to the present invention is configured so that the fuel injection amount increase / decrease setting means It is characterized by increasing the value.

  The control apparatus for an internal combustion engine according to the present invention includes a fuel injection amount calculation unit that calculates a fuel injection amount of the internal combustion engine, a rotation variation amount calculation unit that calculates a rotation variation amount of the internal combustion engine, and the rotation variation amount is a predetermined amount. A fuel injection amount increase / decrease setting means for setting an increase rate of the fuel injection amount when a threshold value is exceeded, and a decrease rate of the fuel injection amount when it is equal to or less than the predetermined threshold; and the increase rate Or a fuel injection amount correction means for correcting the fuel injection amount based on a reduction ratio, at least a control device for an internal combustion engine, wherein the fuel injection amount increase / decrease setting means is an increase ratio of the fuel injection amount. Alternatively, the reduction ratio is changed based on the evaporation amount of the fuel adhering to the intake side of the internal combustion engine after the internal combustion engine is started.

  According to the present invention, after the internal combustion engine is cold-started, the air-fuel ratio is prevented from fluctuating due to a change in the evaporation amount of the fuel adhering to the intake-side equipment as the intake-side temperature rises such as the intake valve and the intake port. Further, the amount of unburned gas (HC) emitted can be suppressed.

  Hereinafter, several embodiments of a control device for an internal combustion engine of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram illustrating a control device for an internal combustion engine according to a first embodiment.
The internal combustion engine 10 is a multi-cylinder engine, for example, an in-line four-cylinder engine having four cylinders # 1 to # 4, and includes a cylinder 11 and a piston 12 slidably inserted into the cylinder 11. A combustion chamber 13 is defined above the piston 12. A spark plug 44 to which a high voltage is applied from the ignition coil 45 is disposed in the combustion chamber 13. A crank angle detection plate 42 is attached to the crankshaft 41 connected to the piston 12, and a crank angle sensor 43 is provided. Further, the cylinder 11 is provided with a cooling water temperature sensor 46.

  On the other hand, an intake pipe 21 corresponding to the intake side of the internal combustion engine 10 is provided with a throttle valve 22 for controlling the intake air amount of the internal combustion engine 10 and an intake pipe pressure sensor 28 for detecting the intake air amount. It has been. Further, a fuel injection valve 24 is provided upstream of the intake port 25 of the cylinder 11 and is arranged so as to inject fuel toward the intake valve 26. Further, an oxygen amount concentration sensor 52 is provided in the exhaust pipe 51 corresponding to the exhaust side of the internal combustion engine 10.

  In the internal combustion engine 10, the air introduced into each cylinder and used for fuel combustion passes through the electric throttle valve 22 to control the intake air amount, and the intake air amount introduced into the combustion chamber 13 is The intake manifold pressure sensor 28 detects the intake manifold 23. Further, an air-fuel mixture of air with controlled intake air amount and fuel injected from the fuel injection valve 24 is introduced into the combustion chamber 13 via an intake valve 26 that is driven to open and close by an intake camshaft 27. . The introduced air-fuel mixture is ignited by the spark plug 44 and explosively burned. The burned gas (exhaust gas) is discharged from an exhaust valve 56 that is opened and closed by an exhaust camshaft 57, and further passes through an exhaust pipe 51 and is discharged to the outside.

  A control unit (control device for an internal combustion engine) 30 includes a CPU 31 that performs arithmetic processing to control a fuel injection amount, which will be described later, a read only memory (ROM) 32 that stores a control program and control data, a control variable, and the like. Is provided, and a writable memory (RAM) 33 and an input / output circuit 34 are provided.

  Signals from the intake pipe pressure sensor 28, the cooling water temperature sensor 46, the crank angle sensor 43, the oxygen amount concentration sensor 52, etc. are input to the control unit 30, and the control unit 30 receives the fuel injection amount and ignition from these input signals. The timing, throttle opening, and the like are calculated, and control signals that are the calculation results are output to the throttle valve 22, the fuel injection valve 24, the ignition coil 45, and the like.

  FIG. 2 is a control block diagram of the control device for the internal combustion engine according to the first embodiment. As shown in FIG. 2, the control device 30 of the internal combustion engine 10 according to the present embodiment includes a fuel injection amount calculation unit 101, a rotation fluctuation amount calculation unit 102, a fuel injection amount increase / decrease amount setting unit 103, and a fuel injection amount. And at least correction means 104.

  The fuel injection amount calculation means 101 is a means for calculating the fuel injection amount TP of the internal combustion engine 10, and the fuel injection amount TP is determined by the rotational speed Ne of the internal combustion engine measured by the crank angle sensor 43 and the intake pipe pressure sensor 28. Is calculated by the intake air amount (intake pipe pressure) Q measured by the above.

  The rotational fluctuation amount calculation means 102 is a means for calculating the rotational speed fluctuation amount (rotational fluctuation amount) DN of the internal combustion engine 10, and the rotational fluctuation amount DN is determined by a predetermined crank after the explosion from the signal of the crank angle sensor 43. A time Tn (corresponding to the reciprocal of the crank angular velocity) for displacement between the angles is measured for each cylinder, and the difference between the displacement time Tn in the current explosion and the displacement time Tn-1 in the previous explosion is defined as the rotational fluctuation amount. And so on. The calculation of the rotational fluctuation amount DN is performed in synchronization with the explosion cycle of each cylinder.

  The fuel injection amount increase / decrease amount setting means 103 sets an increase ratio of the fuel injection amount TP when the rotational fluctuation amount DN exceeds a predetermined threshold SLDN, which will be described later, and when it is equal to or less than the predetermined threshold SLDN. This is a means for setting a reduction ratio of the fuel injection amount TP. The detailed description of the fuel injection amount increase / decrease setting means 103 will be described later with reference to FIGS.

  The fuel injection amount correction unit 104 is a unit that corrects the fuel injection amount TP based on the increase rate or decrease rate of the fuel injection amount TP set by the fuel injection amount increase / decrease amount setting unit 103. The fuel injection amount correction unit 104 Based on the fuel injection amount TI corrected by the above, the control device 30 of the internal combustion engine outputs a control signal to the fuel injection valve 24, and the fuel injection valve 24 injects fuel based on the control signal.

  FIG. 3 is a diagram for explaining the amount of fuel injected based on the fuel injection amount increase / decrease setting unit 103 and the fuel injection amount correction unit 104 shown in FIG.

  The fuel injection amount increase / decrease amount setting means 103 sets an increase ratio or a decrease ratio of the fuel injection amount, and the set increase ratio depends on the elapsed time from the start of the internal combustion engine (the elapsed time has passed). Changed). As shown in FIG. 3, a section 1 is a period from the start of the internal combustion engine to a predetermined elapsed time Tr, and a section 2 is a period from the predetermined elapsed time Tr to a time Te when the oxygen amount concentration sensor 20 is activated.

  In addition, the elapsed time Tr that becomes the boundary between the section 1 and the section 2 increases the evaporation amount of the fuel adhering to the intake side immediately after the start due to the temperature increase on the intake side such as the wall surface of the intake port 25 and the intake valve 26 after the start. This is the timing when the air-fuel ratio starts to change richly. Here, the elapsed time Tr is set by measuring in advance the timing at which the air-fuel ratio becomes rich due to the rise in the wall surface temperature (elapsed time since the start of the internal combustion engine 10).

  As shown in FIG. 3, the fuel injection amount increase / decrease amount setting means 103 is operated by the rotational fluctuation amount calculated by the rotational fluctuation amount calculation means 102 in the section 1 (from the start of the internal combustion engine to a predetermined elapsed time Tr) after the cold start. When the amount DN exceeds a predetermined threshold value SLDN1, an increase ratio (predetermined increase ratio) FSTPA1 of the fuel injection amount TP is set, and the fuel injection amount correction means 104 is the fuel injection calculated by the fuel injection amount calculation means 101. The amount TP is increased and corrected using the set increase rate FSTPA1. On the other hand, when the rotational fluctuation amount DN is equal to or less than SLDN1, the fuel injection amount increase / decrease setting unit 103 sets a reduction rate (predetermined reduction rate) FSTPD1 of the fuel injection amount TP, and the fuel injection amount correction unit 104 The injection amount TP is corrected to decrease by a predetermined ratio FSTPD1 at predetermined time intervals (ignition intervals, etc.).

  Then, the fuel injection amount increase / decrease amount setting means 103 changes the increase ratio or the decrease ratio based on the evaporation amount of the fuel adhering to the intake side of the internal combustion engine 10 after the internal combustion engine 10 is started. Specifically, in the section 1, the fuel injection amount increase / decrease amount setting means 103 is less likely to evaporate the fuel adhering to the intake side because the temperatures of the intake port 25 and the intake valve 26 are lower than those during normal operation. Therefore, the fuel increase rate FSTPA1 at the time of detecting the rotational fluctuation amount DN is set to an increase rate at which the cylinder inflow fuel amount is not insufficient due to fuel adhesion.

  On the other hand, when the section 2 is entered, that is, after the elapsed time Tr from the start of the internal combustion engine, the wall surface temperature of the intake port 25 and the intake valve 26 rises compared to the temperature of the section 1, and the attached fuel The amount of evaporation increases. Therefore, the fuel injection amount increase / decrease amount setting means 103 determines that the rotational fluctuation amount DN exceeds the predetermined threshold SLDN2 based on the elapsed time Tr from the start of the internal combustion engine so that the amount of fuel flowing into the cylinder 11 does not become excessive. In some cases, the increase ratio is changed from FSTPA1 to FSTPA2 so that the fuel increase ratio (increase ratio) FSTPA2 becomes smaller than the fuel increase ratio FSTPA1 in section 1.

  As a result, as shown in section 2 of FIG. 3, the fuel correction amount (solid line) is controlled in the decreasing direction with respect to the conventional control (dotted line) that does not change the fuel increase rate. That is, in the conventional control, the cylinder inflow fuel amount (dotted line) gradually increases and the cylinder air-fuel ratio (dotted line) fluctuates in the rich direction due to the increase in the fuel evaporation amount. On the other hand, the control of the control device according to the present embodiment is performed. According to this, the increase rate of the fuel is reduced in consideration of the increase in the fuel evaporation amount due to the rise in the wall temperature on the intake side, so the increase in the cylinder inflow fuel amount (solid line) is suppressed, and the cylinder air-fuel ratio (solid line) becomes rich. Without increasing the emission of unburned gas.

  In the present embodiment, the threshold value SLDN1 in the section 1 and the threshold value SLDN2 in the section 2 are the same value, and the fuel reduction rate FSTPD1 in the section 1 and the fuel reduction rate FSTPD2 in the section 2 are the same value.

  Here, in the present embodiment, the increase ratio is changed so that the fuel increase ratio FSTPA2 in the section 2 is smaller than the fuel increase ratio FSTPA1 in the section 1 based on the elapsed time from the start of the internal combustion engine. However, based on the elapsed time from the start of the internal combustion engine, even if the reduction ratio is changed so that the fuel reduction amount FSTPD2 in the section 2 is larger than the fuel reduction ratio FSTPD1 in the section 1 Good. Even in this case, it is possible to suppress an increase in the amount of fuel flowing into the cylinder 11 by increasing the fuel reduction rate per hour with respect to the increase in the evaporated fuel due to the wall surface temperature increase.

  Further, in the present embodiment, the fuel injection amount increase / decrease setting means 103 determines the section 1 and the section 2 based on the elapsed time from the start of the internal combustion engine, and sets the set increase ratio or decrease ratio. However, according to the same experiment as described above, the number of ignitions of the spark plug 44 from the start of the internal combustion engine, or the load integrated value (fuel amount integrated value (sum of injected fuel amount) from the start of the internal combustion engine, intake air An amount integrated value (including the total amount of inhaled air) may be set, and the increase rate or the decrease rate may be changed according to these values.

  FIG. 4 is a flowchart for explaining the operation of the control unit 30 shown in FIG. FIG. 5 is a diagram for explaining a method of calculating the fuel increase rate FSTPA (FSTPA1, FSTPA2) in each section. Hereinafter, the operation of the control unit 30 will be described in detail.

  First, in step 100, it is determined whether or not the engine temperature (cooling water temperature) detected by the cooling water temperature sensor 46 is in a cold state equal to or lower than a predetermined temperature TWSL. If it is determined that the engine is in the cooling state, the routine proceeds to step 110, where the oxygen amount concentration sensor 52 is activated and the air-fuel ratio is not detectable, that is, the oxygen amount concentration sensor 52 is activated after the internal combustion engine is started. It is determined whether it is not in a state. As a result, when either of steps 100 and 110 is not established, that is, when the air conditioner is not in the cold state at step 100, or when the oxygen amount concentration sensor 52 is not inactive (is active) at step 110, the rotation is performed. Since the air-fuel ratio control based on the fluctuation amount becomes unnecessary, fuel correction based on the rotation fluctuation amount is prohibited and the fuel correction amount FTRM is set to zero.

  On the other hand, if both steps 100 and 110 are established, in step 120, the rotation fluctuation amount calculation means 102 calculates the fluctuation amount (rotation fluctuation amount) DN of the internal combustion engine by the method described above, and proceeds to step 130. .

  In step 130, the fuel injection amount increase / decrease amount setting means 103 performs section determination after the internal combustion engine 10 is started. Specifically, as described above, the temperature of the intake side such as the intake port 25 and the wall surface of the intake valve 26 rises after the start, and the amount of fuel evaporated on the intake side increases and the air-fuel ratio changes richly. First, the elapsed time Tr from the start of the internal combustion engine is measured in advance by experiment (here, the elapsed time Tr is measured by measuring, for example, the elapsed time or the number of ignitions after reaching a predetermined rotation at the start) The period from the start to the time before Tr has elapsed is referred to as section 1, and the period from the start to the time after the Tr has elapsed until the oxygen concentration sensor 52 is activated is referred to as section 2. judge.

  Here, instead of using the elapsed time or the number of ignition after the start as an index of the temperature rise of the intake port 25 and the intake valve 26, the load integrated value (fuel amount integrated value or air amount integrated value) after the start as described above is used. May be used).

  In this case, set the threshold value of the load integrated value when the fuel vapor increases due to the wall temperature rise and the air-fuel ratio becomes rich, compare the load integrated value with the set threshold value, and the load integrated value is less than the threshold value. When the load integrated value is equal to or greater than the threshold value, it is determined that it is the section 2.

  If it is determined in step 130 that the section is 1, the process proceeds to step 140, and a threshold value (predetermined value) SLDN1 is set to the threshold value SLDN of the rotational fluctuation amount at which fuel increase is performed. In step 150, when the rotational fluctuation amount DN exceeds the threshold value, a predetermined increase rate FSTPA1 is set to the fuel increase rate FSTPA. When the rotational fluctuation amount DN is equal to or less than the threshold value, a predetermined reduction rate FSTPD1 is set in the fuel reduction rate FSTPD.

  On the other hand, if it is determined in section 130 that it is the section 2, the threshold value (predetermined value) SLDN2 is set to the threshold value SLDN of the rotational fluctuation amount DN in which fuel increase is performed in step 160. In step 170, a predetermined value FSTPA2 smaller than the predetermined value FSTPA1 is set as the fuel increase rate FSTPA when the rotational fluctuation amount DN exceeds the threshold value. Further, a predetermined value FSTPD2 is set to the fuel decrease rate FSTPD when the rotation fluctuation amount DN does not exceed the threshold value.

  Here, as shown in FIG. 5, the fuel increase rate FSTPA is set according to the difference DN−SLDN between the rotational fluctuation amount DN and the threshold value SLDN. This is because there is a correlation between the rotational fluctuation amount DN and the air-fuel ratio. Generally, as the air-fuel ratio becomes leaner, the combustion state tends to become unstable and the rotational fluctuation amount tends to increase. Therefore, when the rotational fluctuation amount DN is large, the amount of fuel increase The ratio is increased so that the lean air-fuel ratio is quickly suppressed.

  As described above, in the section 2, the fuel evaporation amount increases due to the rise in the wall temperature of the intake port 25 and the intake valve 26 and the air-fuel ratio fluctuates in the rich direction. Therefore, in this embodiment, the enrichment of the air-fuel ratio due to the rise in the wall temperature is suppressed. Thus, the fuel increase rate FSTPA2 in the section 2 is changed to be smaller than the fuel increase ratio FSTPA1 in the section 1.

  In the present embodiment, the threshold values SLDN1 and SLDN2 of the rotational fluctuation amount in each section shown in Step 140 and Step 160 of FIG. 4 are the same value, and the fuel reduction ratios FSTPD1 and FSTPD2 shown in Step 150 and Step 170 are the same. However, the fuel reduction rate FSTPD2 may be changed to be larger than FSTPD1 so that the air-fuel ratio enrichment due to the wall surface temperature increase is suppressed.

  In this embodiment, the fuel increase ratio is switched for the two sections after the start. However, the fuel increase ratio is continuously set according to the elapsed time, the number of ignitions, and the load integrated value after the start. You may make it change little by little.

  Next, at step 180, the rotation fluctuation amount DN is compared with the threshold value SLDN for each explosion cycle. If the rotation fluctuation amount DN exceeds the threshold value SLDN, FSTPA is added to the fuel correction amount FTRM at step 190. When the rotational fluctuation amount DN does not exceed the threshold value SLDN, in step 200, FSTPD is subtracted from FTRM.

  Next, at step 220, the injection pulse width (corrected fuel injection amount) TI of the fuel injection valve 24 is calculated. The TI is calculated by correcting the basic injection pulse width (fuel injection amount) TP obtained from the intake air amount calculated from the intake pipe pressure sensor signal, etc., in addition to the correction by the fuel correction amount FTRM by the rotational fluctuation amount, and the conventional start-up. The jet pulse width TI to be output is the one that has been corrected by the correction amount FAS by the later time, the correction amount FTW by the cooling water temperature, or the like.

  The above fuel control method prevents leaning due to fuel adhering to the wall surface immediately after starting, and appropriately controls the fuel increase rate in consideration of the increase in evaporated fuel after the wall surface temperature rises after starting. As a result, fluctuation of the air-fuel ratio to the rich side can be suppressed, and an increase in the amount of unburned gas (HC) discharged can be prevented.

  FIG. 6 is a view for explaining a second embodiment according to the present invention. The present embodiment is different from the first embodiment in that the threshold for the rotational fluctuation amount is changed according to the section after the internal combustion engine is started.

  In the second embodiment, as in the first embodiment, when the rotational fluctuation amount DN exceeds a predetermined threshold value SLDN after the start of cooling, the fuel is increased and corrected according to the difference DN−SLDN between the rotational fluctuation amount DN and the threshold value SLDN. .

  As shown in FIG. 6, in the same section 1 as in the first embodiment, when the rotational fluctuation amount DN exceeds a predetermined threshold value SLDN1, the fuel is corrected to increase at a predetermined increase rate FSTPAl. On the other hand, in the section 2 in which the temperature of the intake port 25 and the intake valve 26 rises and the fuel evaporation amount increases, the rotational fluctuation amount threshold value SLDN2 for increasing the fuel is set to the side where the rotational fluctuation amount becomes larger than the SLDN1. That is, the threshold value is changed to be larger.

  As a result, when the rotational fluctuation amount is the same in the section 2, the difference DN-SLDN2 between the rotational fluctuation amount and the threshold value is smaller than the difference DN-SLDN1 between the rotational fluctuation amount and the threshold value in the section 1, and FIG. Since the difference between the rotational fluctuation amount and the threshold value shown in FIG. 3 is smaller, the fuel increase rate FSTPA is reduced. As a result, in the same way as in the first embodiment, the rate of increase in fuel when the fuel vapor increases due to the rise in wall surface temperature in section 2 decreases, and the cylinder inflow fuel amount (solid line) in FIG. Therefore, the fluctuation of the cylinder air-fuel ratio to the rich side can be suppressed.

  In the flowchart of the control method according to the present embodiment, the threshold value SLDN1 is set to the threshold value SLDN in step 140 in the case of section 1 according to the section determination result in step 130 in FIG. The predetermined threshold value SLDN2 shifted in the direction of increasing the rotational fluctuation amount (threshold value obtained by increasing the value with respect to the threshold value SLDN1) may be changed to SLDN.

  Then, in step 150 and step 170, the same value is set as FSTPA1 and FSTPA2 as the rate of increase, and the same value is set as FSTPD1 and FSTPD2 as the rate of decrease. Other steps are the same as those in the first embodiment.

  In this embodiment, the threshold value of the rotation fluctuation amount is switched for two sections after the start of the internal combustion engine. However, the rotation fluctuation is continuously changed according to the elapsed time after the start, the number of ignitions, and the load integrated value. The amount threshold may be changed.

  The two embodiments of the control device for an internal combustion engine of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and the spirit of the present invention described in the claims is included. Various design changes can be made without departing from the scope.

  For example, in the first embodiment, the increase rate or decrease rate of the fuel injection amount is changed according to the section. However, if the fuel can be injected in accordance with the evaporation amount of the attached fuel on the intake side, these two The ratio may be changed. Further, as the ratio of 2 is changed, the threshold value may be changed as shown in the second embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram which showed the control apparatus of the internal combustion engine which concerns on 1st embodiment of this invention. The control block diagram of the control apparatus of the internal combustion engine which concerns on 1st embodiment. The figure for demonstrating the fuel amount injected based on the fuel injection amount increase / decrease amount setting means and fuel injection amount correction | amendment means shown in FIG. The flowchart for demonstrating operation | movement of the control unit shown in FIG. The figure for demonstrating the calculation method of the increase ratio of the fuel of each area. The figure for demonstrating the fuel quantity injected by the control apparatus of the internal combustion engine which concerns on 2nd embodiment of this invention. The figure which shows the relationship between the intake valve temperature and the air-fuel ratio after starting in the control apparatus of the conventional internal combustion engine The figure which shows the relationship between the fuel evaporation amount and the air fuel ratio in the control apparatus of the conventional internal combustion engine

Explanation of symbols

10: internal combustion engine, 11: cylinder, 12: piston, 13: combustion chamber, 20: oxygen concentration sensor, 21: intake pipe, 22: throttle valve, 23: intake manifold, 24: fuel injection valve, 25: intake port , 26: intake valve, 27: camshaft, 28: intake pipe pressure sensor, 30: control unit (control device for internal combustion engine), 34: input / output circuit, 41: shaft, 42: plate, 43: crank angle sensor, 44: ignition plug, 45: ignition coil, 46: cooling water temperature sensor, 51: exhaust pipe, 52: oxygen concentration sensor, 56: exhaust valve, 101: fuel injection amount calculating means, 102: rotation fluctuation amount calculating means, 103 : Fuel injection amount increase / decrease amount setting means, 104: fuel injection amount correction means, DN: rotational fluctuation amount, Ne: rotational speed, TI: corrected fuel injection amount (injection volume) Scan width), TP: fuel injection amount, Tn: displacement time, Tr: elapsed time, FSTPA, FSTPA1, FSTPA2: increase ratio, FSTPD, FSTPD1, FSTPD2: weight loss ratio

Claims (6)

Fuel injection amount calculating means for calculating the fuel injection amount of the internal combustion engine, rotation fluctuation amount calculating means for calculating the rotational fluctuation amount of the internal combustion engine, and the fuel injection amount when the rotational fluctuation amount exceeds a predetermined threshold A fuel injection amount increase / decrease setting means for setting a fuel injection amount decrease ratio when the fuel injection amount is equal to or less than the predetermined threshold, and the fuel injection amount based on the increase ratio or the decrease ratio. A control device for an internal combustion engine, comprising: a fuel injection amount correcting means for correcting,
The fuel injection amount increase / decrease setting means changes the increase ratio or the decrease ratio based on an elapsed time from the start of the internal combustion engine, the number of ignitions, or an engine load integrated value. Control device. Fuel injection amount calculating means for calculating the fuel injection amount of the internal combustion engine, rotation fluctuation amount calculating means for calculating the rotational fluctuation amount of the internal combustion engine, and the fuel injection amount when the rotational fluctuation amount exceeds a predetermined threshold A fuel injection amount increase / decrease setting means for setting a fuel injection amount decrease ratio when the fuel injection amount is equal to or less than the predetermined threshold, and the fuel injection amount based on the increase ratio or the decrease ratio. A control device for an internal combustion engine, comprising: a fuel injection amount correcting means for correcting,
The fuel injection amount increase / decrease setting means changes the threshold value based on an elapsed time from the start of the internal combustion engine, the number of times of ignition, or an engine load integrated value. Control device for internal combustion engine.   When the elapsed time, the number of times of ignition, or the value of the engine load integrated value exceeds a predetermined value, the fuel injection amount increase / decrease setting means decreases the increase rate of the fuel injection amount. The control apparatus for an internal combustion engine according to claim 1 or 2.   When the elapsed time, the number of times of ignition, or the value of the engine load integrated value exceeds a predetermined value, the fuel injection amount increase / decrease setting means increases the reduction ratio of the fuel injection amount. The control apparatus for an internal combustion engine according to any one of claims 1 to 3.   The fuel injection amount increase / decrease setting means increases the threshold value when the elapsed time, the number of times of ignition, or the value of the engine load integrated value exceeds a predetermined value. The control apparatus of the internal combustion engine in any one of 1-4. Fuel injection amount calculating means for calculating the fuel injection amount of the internal combustion engine, rotation fluctuation amount calculating means for calculating the rotational fluctuation amount of the internal combustion engine, and the fuel injection amount when the rotational fluctuation amount exceeds a predetermined threshold A fuel injection amount increase / decrease setting means for setting a fuel injection amount decrease ratio when the fuel injection amount is equal to or less than the predetermined threshold, and the fuel injection amount increase ratio or the decrease ratio based on the fuel injection amount increase ratio A fuel injection amount correcting means for correcting the fuel injection amount;
The fuel injection amount increase / decrease setting means changes the increase ratio or the decrease ratio based on an evaporation amount of fuel adhering to the intake side of the internal combustion engine after the internal combustion engine is started. A control device for an internal combustion engine characterized by the above.

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