JP2007278073A - Engine control method and engine controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine control method capable of quickly converging the rotational speed of an engine to a target one during idling while promoting the warmup of a catalyst and preventing an actual air-fuel ratio from being leaned beyond a combustion stability limit even after the rotational speed arrives at the target one during idling. <P>SOLUTION: This engine controller 31 performs the step of stepwise retarding an ignition timing from a timing for starting to a timing for promoting the warmup of the catalyst when the engine rotational speed reaches the target one during idling, the step of so starting to open a throttle valve 23 at a predetermined time period before the rotational speed reaches the target one during idling that an intake air amount required to hold the rotational speed at the target one during idling when the rotational speed reaches the target one during idling, and the step of temporarily increasing the injection amount of fuel from a fuel injection valve 21 from a time when the throttle valve 23 is started to open and a time when a variation in intake pressure or intake flow velocity is settled after the rotational speed reaches the target one during idling. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine (internal combustion engine) control method and control device, and more particularly to control at a cold start.

After the complete explosion due to the cranking in the cold state, the ignition timing is set as the starting ignition timing until the engine speed increases, and after the engine speed increases, the activation of the catalyst is promoted. There is one that retards the ignition timing stepwise to a predetermined crank angle position after compression top dead center (see Patent Document 1).
Japanese Patent Laid-Open No. 8-232645

  By the way, in the technique of Patent Document 1, before the ignition timing is retarded stepwise to a predetermined crank angle position after compression top dead center, the intake air amount is increased by increasing the ISC opening, etc. It is proposed that it is preferable to further increase the intake air amount after the timing of retarding the timing stepwise, and this makes smoothing or speeding up of the engine.

  However, although it is intended to smooth or speed up the engine blow-up, it is wasteful to increase the engine rotation speed beyond the target rotation speed during idling in terms of fuel consumption. It will be consumed. Therefore, from the viewpoint of improving fuel efficiency, it is preferable that the engine speed is converged to the target speed at idling without overshooting after the complete explosion, even during cold start.

  Therefore, at the timing when the engine speed from cranking reaches the target speed at idling, the ignition timing is retarded in steps from the ignition timing for starting to the ignition timing for promoting catalyst warm-up, and fuel efficiency is improved. In view of the above, the throttle valve is set so that the intake air amount required to maintain the engine speed at the target speed at idling is supplied to the combustion chamber at the timing when the engine speed reaches the target speed at idling. Considering the response delay of the intake air amount from the position to the combustion chamber, a configuration is considered in which the throttle valve starts to open at a timing before a predetermined period before the timing at which the engine rotation speed reaches the target rotation speed during idling.

  And when I experimented with this configuration, after the engine rotation speed reached the target rotation speed during idling as expected, the engine rotation speed did not blow up beyond the target rotation speed during idling. However, it has been newly found that the actual air-fuel ratio leans beyond the combustion stability limit, resulting in a drop in rotation from the target rotation speed during idling or an increase in HC.

  Therefore, the present invention quickly converges the engine speed after the complete explosion toward the target rotational speed during idling while promoting warm-up of the catalyst during cold start, and the engine rotational speed is the target rotational speed during idling. It is an object of the present invention to provide an engine control method and control device in which the actual air-fuel ratio does not become leaner than the combustion stability limit even after reaching the value.

  The present invention relates to an engine having an exhaust passage with a catalyst that functions only after being activated, and a fuel injection valve for injecting fuel into an intake passage (for example, an intake port). When the target rotational speed is reached, the ignition timing is retarded stepwise from the ignition timing for starting to the ignition timing for promoting catalyst warm-up, and the engine rotational speed reaches the target rotational speed during idling. The throttle valve is set a predetermined time before the timing at which the engine speed reaches the target rotational speed during idling so that the intake air amount required to maintain the rotational speed at the target rotational speed during idling is supplied to the combustion chamber. Starting from the timing at which the throttle valve begins to open, and the target engine speed when the engine speed is idle During up change of the intake air flow rate of the intake air pressure or intake port after reaching settles, configured to temporarily increase the fuel injection amount from the fuel injection valve.

  According to the present invention, the ignition timing is retarded stepwise from the ignition timing for starting to the ignition timing for promoting catalyst warm-up at the timing when the engine rotational speed from the start reaches the target rotational speed at the time of idling, When the engine speed is at idle, the intake air amount necessary to maintain the engine speed at the target speed at idling is supplied to the combustion chamber when the engine speed reaches the target speed at idling. Since the throttle valve starts to open a predetermined time before the timing of reaching the target rotational speed of the engine, the exhaust temperature is raised early while suppressing the blow-up after the engine rotational speed reaches the target rotational speed during idling. Thus, the catalyst activation time can be shortened while suppressing wasteful fuel consumption.

  In this case, the intake pressure and / or the intake port intake flow velocity may continue to change for a while after the engine rotation speed reaches the target rotation speed during idling. As the air pressure and the intake air flow velocity of the intake port change, the fuel wall flow rate at the intake port wall decreases, and the amount of fuel supplied to the combustion chamber is reduced accordingly, and the air-fuel ratio of the air-fuel mixture in the combustion chamber reaches the combustion stability limit. However, according to the present invention, the engine rotational speed reaches the target rotational speed at the time of idling, starting from the timing at which the throttle valve starts to open. After that, the fuel injection amount from the fuel injection valve is temporarily increased until the change in the intake pressure or intake flow velocity of the intake port settles, so the engine speed is the target when idling Even if the intake pressure or the intake air flow velocity at the intake port continues to change after reaching the rotation speed, the air-fuel ratio of the air-fuel mixture in the combustion chamber exceeds the combustion stability limit and becomes lean. Can be prevented. As a result, it is possible to suppress an increase in HC after the engine rotation speed reaches the target rotation speed during idling and a drop in rotation from the target rotation speed during idling.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an engine control apparatus used directly for carrying out an engine control method.

  The air metered by the throttle valve 23 is stored in the intake collector 2 and then introduced into the combustion chamber 5 of each cylinder via the intake manifold 3. Fuel is intermittently injected and supplied into the intake port at a predetermined timing from a fuel injection valve 21 disposed in the intake port 4 of each cylinder. The fuel injected into the intake port 4 is mixed with air to form an air-fuel mixture. The air-fuel mixture is confined in the combustion chamber 5 by closing the intake valve 15, compressed by the ascending piston 6, and the spark plug 14 It is ignited and burns. The gas pressure due to the combustion works to push down the piston 6, and the reciprocating motion of the piston 6 is converted into the rotational motion of the crankshaft 7. The combusted gas (exhaust gas) is discharged into the exhaust passage 8 when the exhaust valve 16 is opened.

A first catalyst 9 (start-up catalyst) is provided in the manifold passage portion of the exhaust passage 8, and a second catalyst 10 is provided at a position below the floor of the vehicle. These two catalysts 9, 10 are, for example, all three-way catalysts, and when the air-fuel ratio of the exhaust is in a narrow range centered on the stoichiometric air-fuel ratio, the three-way catalyst simultaneously converts HC, CO, and NOx contained in the exhaust. Can be removed efficiently. For this reason, the engine controller 31 to which the intake air amount signal from the air flow meter 32 and the signal from the crank angle sensor (the position sensor 33 and the phase sensor 34) are input is based on these signals and the basic from the fuel injection valve 21. The fuel injection amount is determined, and the air-fuel ratio is feedback-controlled based on a signal from an O ₂ sensor 35 provided upstream of the first catalyst 9.

On the other hand, at the time of cold start, the catalyst is activated early, and the O ₂ sensor 35 is also activated early to execute air-fuel ratio feedback control. Therefore, the O ₂ sensor 35 is immediately started by a heater (not shown). heating, looking at signals from the O ₂ sensor 35, O ₂ sensor 35 is started feedback control of the air-fuel ratio at the timing of activation.

  In addition, the structure of the catalysts 9 and 10 is not restricted to this. For example, in order to improve fuel efficiency after completion of engine warm-up, when operating at a leaner air / fuel ratio than the stoichiometric air / fuel ratio in the low-load side operation region, NOx generated frequently during lean operation is absorbed. For this reason, the second catalyst 10 is constituted by a NOx trap catalyst, and this NOx trap catalyst is provided with a three-way catalyst function, but such a constitution may also be used.

  The throttle valve 23 is driven by a throttle motor 24. Since the torque required by the driver appears in the amount of depression of the accelerator pedal 41 (accelerator opening), the engine controller 31 determines a target torque based on a signal from the accelerator sensor 42, and a target air for realizing this target torque. The throttle valve drive device (not shown) controls the opening degree of the throttle valve 23 via the throttle motor 24 so that the target air amount is obtained.

  Further, the rotational phase difference between the variable valve lift mechanism 26 constituted by a multi-joint link mechanism that continuously and variably controls the valve lift amount of the intake valve 15, the crankshaft 7, and the intake valve camshaft 25. A variable valve timing mechanism 27 is provided for continuously varying and controlling the opening / closing timing of the intake valve 15 to advance or retard.

  Now, the engine speed from the cranking in the cold state is blown up well, and the ignition timing is retarded in order to warm up the first catalyst 9 provided in the exhaust passage 8 at an early stage. Yes. This situation will be specifically described in the case of a four-cylinder engine with reference to FIG.

  First, the current control will be described. At present, as indicated by the one-dot chain line at the top of FIG. 2, the engine speed corresponds to the first explosion in three cylinders from the timing t0 when the starter switch is switched from OFF to ON for starting. It fluctuates, and the engine speed rapidly increases due to the explosion of the fourth cylinder, and blows up across the target speed NSET during idling at the timing of t2 (see the one-dot chain line). From the timing of t2 when the engine speed reaches the target engine speed NSET during idling, the intake air that can maintain the target engine speed NSET during idling is shown in FIG. The throttle valve opening is stepwise opened to a predetermined opening TVO1 so as to be introduced into the combustion chamber 5.

  In addition, the fuel injection amount is that not all of the injected fuel is sucked into the combustion chamber 5 at the beginning of the cold start, but a part of the injected fuel amount adheres to the intake port 4 wall or the back of the intake valve 15 umbrella, Since it is used to form a so-called fuel wall flow that flows in a liquid state on the intake port wall, a fuel supply delay to the combustion chamber 5 occurs. For this reason, as shown by the alternate long and short dash line in the fourth stage of FIG. 2, while much of the fuel wall flow on the intake port wall is deprived at the beginning of the start, extra fuel is injected and supplied, and the fuel wall flow is formed. The fuel injection amount is gradually decreased from the timing when many are not lost.

  On the other hand, the ignition timing is currently set to the first ignition timing ADV1, which is the ignition timing for starting from the timing of t0, as shown by the one-dot chain line in the second stage of FIG. 2, and from the timing of t2, The 1st catalyst 9 is gradually switched to the second ignition timing ADV2 that is greatly retarded in order to promote warm-up.

  Here, if the engine rotation speed from cranking is divided into the front and the rear at the timing t2 when the engine rotation speed reaches the target rotation speed during idling, the engine rotation speed Ne is blown after t2 from the viewpoint of improving fuel efficiency. It is desirable to quickly settle down to the target rotational speed NSET during idling without increasing. This is because fuel consumption increases as the engine speed increases beyond the target rotational speed NSET during idling.

  It is desirable that the actual air-fuel ratio settles to the stoichiometric air-fuel ratio after t2. This is because the first catalyst 9 after completion of warm-up can simultaneously purify the harmful three components (HC, CO, NOx) only when it is in a narrow range centered on the stoichiometric air-fuel ratio.

  Therefore, at the timing t2 when the engine rotational speed Ne from the cranking reaches the target rotational speed NSET during idling, the ignition timing is changed from the first ignition timing ADV1 to the first ignition timing ADV1 as shown by the solid line in the second stage of FIG. 2 From the viewpoint of improving the fuel efficiency, the ignition timing ADV2 is retarded stepwise, and the engine rotational speed Ne is set to the idling target rotational speed at the timing t2 when the engine rotational speed Ne reaches the idling target rotational speed NSET. In consideration of the response delay of the intake air amount from the throttle valve position to the combustion chamber 5 so that the intake air amount required to be held in NSET is supplied to the combustion chamber 5, a solid line in the fifth stage of FIG. As shown in Fig. 5, the throttle speed is slower than the timing t1 a predetermined period before the timing t2 when the engine speed Ne reaches the target rotational speed NSET during idling. Considering the configuration to start to open the torque valve 23.

  As a result of experiments with this configuration, after the engine rotational speed Ne has reached the target rotational speed NSET during idling, the engine rotational speed increases beyond the target rotational speed NSET during idling. As shown by the one-dot chain line in the sixth stage of FIG. 2, the actual air-fuel ratio is the theoretical air-fuel ratio at the timing t2 when the engine rotational speed Ne reaches the target rotational speed NSET during idling. Although it is (Stoichiki), after that, it becomes leaner beyond the combustion stability limit line, and this excessive leaning newly increases HC as shown by the one-dot chain line in the seventh stage of FIG. Turned out to.

  The experiment was conducted by assuming that this is mainly due to the fuel wall flow in the intake port 4 wall. As shown in the third stage of FIG. 2, the engine speed Ne is the target rotation when idling. The intake pressure continued to decrease after the timing t2 when the speed NSET was reached. That is, the fuel wall flow rate of the intake port wall depends on the pressure of the portion where the fuel wall flow flows (that is, the intake pressure) and the intake flow velocity of the portion where the fuel wall flow flows (the intake flow velocity of the intake port 4). The characteristic becomes smaller (this is because the vaporization characteristic of the fuel becomes better as the intake pressure becomes smaller), and becomes smaller as the intake flow velocity of the intake port 4 becomes larger (this means that the vaporization of the fuel becomes larger as the intake flow velocity of the intake port 4 becomes larger). Characteristics (because the characteristics are improved), the intake pressure and the intake port flow velocity at the intake port and the intake port flow velocity at the timing t2 in the middle of the change in the intake pressure and intake port flow velocity are the predetermined values. The fuel wall flow rate at the timing of t3 when it settles down becomes smaller. Since the amount of fuel flowing into the combustion chamber 5 includes this fuel wall flow rate, the reduction in the fuel wall flow rate during the period from t2 to t3 means that the amount of fuel flowing into the combustion chamber 5 also decreases this fuel wall flow rate. Therefore, even if the air-fuel ratio of the air-fuel mixture becomes the stoichiometric air-fuel ratio at the timing of t2, the actual air-fuel ratio goes to the lean side as the fuel wall flow rate decreases, It seems to have become leaner than the combustion stability limit.

  Therefore, the present invention performs the following three operations.

  [1] From the timing t2 when the engine rotational speed Ne reaches the target rotational speed NSET at the time of idling, the engine rotational speed Ne exceeds the target rotational speed NSET at the time of idling while promoting warm-up of the first catalyst 9 in particular. 2, as indicated by a solid line in the second stage of FIG. 2, the ignition timing is t2, and the first ignition timing (ignition timing for starting) ADV1 to the second ignition timing (catalyst warm-up). The ignition timing for acceleration) is retarded stepwise to ADV2. Such ignition timing control is executed for each cylinder. Here, idling means a state in which the driver does not depress the accelerator pedal 41. The target rotational speed NSET at the time of idling is a conforming value.

  [2] In order to maintain the engine rotational speed Ne at the idling target rotational speed NSET from the timing t2, the intake air amount necessary to maintain the idling target rotational speed NSET is supplied to the combustion chamber 5. Yes, the air supply to the combustion chamber 5 needs to be completed at the timing of t2. In this case, it is the throttle valve 23 provided in the intake passage upstream of the intake collector 2 that controls the intake air amount in the current engine, and therefore, the response of the intake air amount from the throttle valve position to the combustion chamber 5. In consideration of the delay, as indicated by the solid line in the fifth stage of FIG. 2, the throttle valve 23 starts to open toward the predetermined value TVO1 at the timing t1 before the predetermined period before t2, and is predetermined at the timing t2. Try to settle to the value TVO1.

  [3] Although the engine rotational speed Ne settles to the target rotational speed NSET during idling due to the step delay of the ignition timing at t2, the fuel wall flow rate decreases due to a change in the intake pressure immediately after that and the intake port intake air flow velocity. Since the air-fuel ratio becomes excessively lean and HC increases (or the engine speed Ne decreases from the target rotational speed NSET during idling), in order to prevent this increase in HC, As shown by the solid line in the fourth stage, the fuel wall flow rate to the combustion chamber 5 starts from the timing t1 when the throttle valve 23 starts to open until t3 when the change in the intake air pressure and the intake air flow velocity of the intake port is settled. The fuel injection amount is temporarily increased to compensate for the decrease.

  Here, on the premise of the current fuel injection control, the post-startup increase correction coefficient KAS is used to execute the operation [3]. This will be described in detail with reference to FIG. 3. The uppermost stage in FIG. 3 is the same as the uppermost stage in FIG. The second stage of FIG. 3 shows the movement of the ignition timing by the operation [1], and the fourth stage shows the movement of the throttle valve opening by the operation [2].

  First, at present, as indicated by a one-dot chain line in the third stage of FIG. 3, the initial value KAS0 (0.3 in the figure) is set as the post-startup increase correction coefficient KAS from the timing t0 when the starter switch 36 is switched from OFF to ON. After that, the engine speed Ne is decreased toward zero at a predetermined speed from the timing t5 when the engine speed Ne reaches the complete explosion speed N0. On the other hand, in the present embodiment, as indicated by a solid line in the third stage of FIG. 3, the initial value KAS0 is held until the timing t2, and is decreased toward zero at a predetermined speed from the timing t2. That is, the timing for decreasing the post-startup increase correction coefficient KAS from the initial value KAS0 is delayed from t5 to t2. As a result, the area indicated by hatching in the third stage of FIG. 3 is the amount of fuel increase, and excessive leaning exceeding the combustion stability limit of the air-fuel ratio can be prevented.

  As described above, the actual air-fuel ratio obtained when the timing for decreasing the post-startup increase correction coefficient KAS from the initial value KAS0 is delayed from t5 to t2 (the fuel injection amount from the fuel injection valve is temporarily increased). The theoretical air-fuel ratio has been confirmed. That is, the post-startup increase correction coefficient KAS (fuel injection from the fuel injection valve 21) so that the actual air-fuel ratio obtained when the fuel injection amount from the fuel injection valve 21 is temporarily increased becomes the stoichiometric air-fuel ratio. The amount of increase) is set.

  Here, the post-startup amount increase correction coefficient KAS is constant (initial value KAS0) between t5 and t2, and thereafter linearly decreases. However, the present invention is not limited to this. In short, starting from the timing t5 when the throttle valve 23 starts to open, the timing until the timing t3 when the change in the intake pressure and the intake flow velocity at the intake port settles after the timing when the engine rotation speed Ne reaches the target rotation speed NSET during idling. In this case, the post-startup increase correction coefficient KAS may be changed so that the fuel injection amount from the fuel injection valve 21 is temporarily increased.

  In addition, the fuel injection amount from the fuel injection valve is temporarily increased by delaying the timing at which the post-startup increase correction coefficient KAS is decreased from the initial value KAS0 from t5 to t2. However, the present invention is not limited to this. For example, a new increase correction coefficient is introduced separately from the post-startup increase correction coefficient KAS, and the timing of t5 at which the throttle valve 23 starts to be opened by this increase correction coefficient is the starting point. The fuel injection amount from the fuel injection valve 21 may be temporarily increased until t3 when the change in the intake pressure and the intake air flow velocity at the intake port settles after the timing when NSET is reached.

  In FIG. 3, the timing at t5 when the engine rotational speed Ne reaches the complete explosion rotational speed N0 is set as the timing at which the throttle valve 23 starts to be opened, but is not limited to this.

Also, as described above, the air-fuel ratio feedback control is started at the timing when the O ₂ sensor 35 is activated. The timing at which the air-fuel ratio feedback control is started is the target rotation when the engine speed Ne is idle. If the change in the intake pressure or the intake flow velocity at the intake port comes before the timing t3 after the timing when the speed NSET is reached, the operation of [3] above may be canceled and returned to the current operation. preferable. This is because the actual air-fuel ratio is kept within a predetermined window width centered on the stoichiometric air-fuel ratio by the air-fuel ratio feedback control, thereby preventing excessive leaning.

  The ignition timing is not limited to the above [1]. For example, as shown in FIG. 8, after switching from the first ignition timing ADV1 to the third ignition timing ADV3 at the timing of t1, from the third ignition timing ADV3 to the second ignition timing ADV2 at the timing of t2, stepwise. It may be delayed. Here, the third ignition timing ADV3 is a value slightly retarded from the first ignition timing ADV1.

  This control executed by the engine controller 31 will be described in detail with reference to the following flowchart.

  FIG. 4 is for setting a complete explosion flag and a target rotation arrival flag, and is executed at regular time intervals (for example, every 100 ms).

  In FIG. 4, in step 1, the engine speed Ne is read. The engine speed Ne is calculated based on signals from the crank angle sensors (33, 34).

  Step 2 looks at the complete explosion flag. This complete explosion flag is a flag that is initially set to zero when an ignition switch (not shown) is switched from OFF to ON. For this reason, since the complete explosion flag = 0 at the beginning, the process proceeds from step 2 to step 3 to compare the engine rotation speed Ne with the complete explosion rotation speed N0 (for example, 1000 rpm). The complete explosion speed N0 is a conforming value. If the engine rotational speed Ne has not reached the complete explosion rotational speed N0, the current process is terminated.

  When the engine speed Ne reaches the complete explosion speed N0 in Step 3 (Ne ≧ N0), the process proceeds to Step 4 to set the complete explosion flag = 1 to indicate that the engine speed Ne has reached the complete explosion speed N0.

  In step 5, a timer is started (timer value TIME = 0). This timer is for measuring the elapsed time from when the engine speed Ne reaches the complete explosion speed N0.

  Since the complete explosion flag = 1, the process proceeds from step 2 to step 6 from the next time. In step 6, the timer value TIME is compared with the predetermined value DT. The predetermined value DT is preliminarily adapted at a time interval from the timing when the engine rotational speed Ne reaches the complete explosion rotational speed N0 to the timing when the engine rotational speed Ne reaches the target rotational speed NSET during idling (see FIG. 3). Since the timer value TIME is initially less than the predetermined value DT when the timer is started, the process proceeds to step 7 and the timer value TIME is incremented by the control period (100 ms).

  If the increment of the timer value TIME in step 7 is repeated several times, the timer value TIME eventually becomes equal to or greater than the predetermined value DT. At this time, the process proceeds from step 6 to step 8 to set the target rotation arrival flag (initially set to zero when the ignition switch is switched from OFF to ON) = 1 to indicate that the target rotation speed NSET during idling has been reached.

  FIG. 5 is for calculating the ignition timing command value and the throttle valve target opening, and is executed at regular intervals (for example, every 100 ms) following the flow of FIG.

  In FIG. 5, in step 21, it is determined whether or not the ignition switch is switched from OFF to ON. When the ignition switch is switched from OFF to ON, the routine proceeds to step 22 where the cooling water temperature TW detected by the water temperature sensor 37 is taken in as the starting water temperature TWINT, and the first ignition timing ADV1 is set according to the starting water temperature TWINT. In step 23, the calculated first ignition timing ADV1 is transferred to the ignition timing command value ADV. The first ignition timing ADV1 is the optimal ignition timing for starting and is largely on the advance side.

  In step 24, an initial value (for example, zero) is input to the throttle valve target opening tTVO.

  After the ignition switch is switched from OFF to ON, that is, when the ignition switch is turned ON, the process proceeds from step 21 to steps 25 and 26. In steps 25 and 26, the complete explosion flag and the target rotation arrival flag (both flags are set according to FIG. 4) are observed. When the complete explosion flag = 0, the routine proceeds to step 27, where the first ignition timing ADV1 calculated when the ignition switch is switched from OFF to ON is maintained. Also at this time, the operation of step 24 is executed.

  When the complete explosion flag = 1 and the target rotation arrival flag = 0, the routine proceeds from step 26 to step 28, where the first ignition timing ADV1 calculated when the ignition switch is switched from OFF to ON is maintained.

  In step 29, the throttle valve target opening tTVO is calculated by the following equation.

tTVO = tTVO (previous) + ΔTVO (1)
Where ΔTVO: constant value,
tTVO (previous): previous value of tTVO,
Here, the predetermined value ΔTVO in the equation (1) is a value that determines an increment of the throttle valve target opening per predetermined time, and this value is a timing at which the engine rotational speed Ne reaches the target rotational speed NSET during idling. Thus, the throttle valve target opening tTVO is determined in advance so as to reach a predetermined value TVO1 described later. The initial value of “tTVO (previous)”, which is the previous value of the throttle valve target opening, is set to zero.

  In step 30, the throttle valve target opening tTVO is compared with a predetermined value TVO1. The predetermined value TVO1 is the throttle valve opening when the minimum intake air amount necessary to generate the torque for maintaining the target rotational speed NSET flows. The predetermined value TVO1 is obtained in advance by adaptation.

  After experiencing step 29 for the first time during the engine operation this time, the throttle valve target opening tTVO is less than the predetermined value TVO1, and thus the current process is terminated. Until the target rotation arrival flag = 1, the operation in step 29 is repeated, and the throttle valve target opening tTVO gradually increases. Immediately before the target rotation arrival flag = 1, the throttle valve target opening tTVO becomes equal to or greater than the predetermined value TVO1. At this time, the routine proceeds from step 30 to step 31 to maintain the throttle valve target opening tTVO at the same value as the previous time.

  When the target rotation arrival flag = 1, the routine proceeds from step 26 to step 32, where the second ignition timing ADV2 is calculated according to the cooling water temperature TW detected by the water temperature sensor 37, and this is calculated at step 33. Move to command value ADV.

  The second ignition timing ADV2 is an ignition timing for promoting warm-up of the first catalyst 9 at the time of cold start, and is set on the retard side with respect to the ignition timing after completion of warm-up of the first catalyst 9. Therefore, the ignition timing is stepwise from the first ignition timing ADV1 to the second ignition timing ADV2 at the timing t2 when the engine rotational speed Ne reaches the target rotational speed NSET as shown in the second stage of FIG. It will be switched.

  The ignition timing command value ADV calculated in this way is transferred to the output register, and the primary current of the ignition coil is cut off at a timing when the actual crank angle coincides with the ignition timing command value ADV.

  Further, in the slot valve drive device that receives the throttle valve target opening tTVO, the throttle motor 24 is driven so that the actual throttle valve opening coincides with the throttle valve target opening tTVO.

  FIG. 6 is for calculating the target equivalent ratio TFBYA, and is executed at regular intervals (for example, every 100 ms).

  In FIG. 6, in step 41, it is determined whether or not the ignition switch is switched from OFF to ON. When the ignition switch is switched from OFF to ON, the routine proceeds to step 42, where the initial value KAS0 of the post-startup increase correction coefficient is calculated according to the starting water temperature TWINT detected by the water temperature sensor 37, and this is calculated at step 43. To shift to the increase correction coefficient KAS after starting. The initial value KAS0 of the post-startup increase correction coefficient is a value that increases as the starting water temperature TWINT decreases.

  After the ignition switch is switched from OFF to ON, that is, when the ignition switch is turned on, the routine proceeds from step 41 to step 44. In step 44, the target rotation arrival flag is checked (set according to FIG. 4). When the target rotation arrival flag = 0, the routine proceeds to step 45, where the post-startup increase correction coefficient KAS is maintained at the same value as before (that is, the initial value KAS0).

  When the target rotation arrival flag = 1, the routine proceeds from step 44 to step 46, where the post-startup increase correction coefficient KAS is compared with zero. Since the post-startup increase correction coefficient KAS is greater than zero at the timing when the target rotation arrival flag = 1 (because the initial value KAS0 is entered), the routine proceeds to step 47, where the post-startup increase correction coefficient KAS is calculated by the following equation. .

KAS = KAS (previous) −Δt × KAS (previous) (2)
Where Δt is a constant value,
KAS (previous): previous value of KAS,
Here, the predetermined value Δt in the equation (2) is a value that determines the decrease per predetermined time of the post-startup increase correction coefficient KAS, and this value becomes zero at the timing of t3 when the intake pressure settles to a constant value. , Determined in advance by conformity. The initial value of “KAS (previous)”, which is the previous value of the increase correction coefficient after starting, is KAS0.

  When the target rotation arrival flag = 1, when the operation in step 47 is repeated, the post-startup increase correction coefficient KAS gradually decreases. Accordingly, the post-startup increase correction coefficient KAS is compared with zero at step 48, and when the post-startup increase correction coefficient KAS becomes a negative value, the routine proceeds to step 49 where the post-startup increase correction coefficient KAS = 0.

  In this way, the post-startup increase correction coefficient KAS is a value that gradually decreases to zero from the timing when the engine rotational speed Ne coincides with the target rotational speed NSET during idling.

  At present, the post-start-up increase correction coefficient KAS is gradually smaller than the timing when the engine rotational speed Ne reaches the complete explosion rotational speed N0. However, in the present invention, the engine rotational speed Ne is equal to the target rotational speed NSET during idling. The initial value is maintained until the coincidence timing, and the engine rotation speed Ne becomes gradually smaller than the coincidence with the target rotation speed NSET during idling.

  Steps 50 and 51 are the same as the current situation. That is, in step 50, the water temperature increase correction coefficient KTW is calculated according to the cooling water temperature Tw detected by the water temperature sensor 37 at that time. The water temperature increase correction coefficient KTW is a value that increases as the cooling water temperature Tw decreases.

  In step 51, the target equivalent ratio TFBYA is calculated by the following equation using the water temperature increase correction coefficient KTW and the post-startup increase correction coefficient KAS.

TFBYA = 1 + KTW + KAS (3)
The target equivalent ratio TFBYA is a value centering on 1.0, and after the engine warm-up is completed, TFBYA = 1 (KTW = 0, KAS = 0), thereby obtaining a stoichiometric air-fuel mixture. . At the cold start, the post-startup increase correction coefficient KAS is added, so the target equivalent ratio TFBYA exceeds 1.0, because the fuel wall flow rate is taken into consideration. That is, at the time of cold start, the target equivalence ratio TFBYA exceeds 1.0, but the stoichiometric air-fuel mixture is obtained at the timing when the engine speed reaches the target speed NSET during idling. .

  FIG. 7 is for calculating the fuel injection pulse width Ti. The float of FIG. 6 is executed independently at regular time intervals (for example, every 100 ms). This flow is the same as the current situation.

  In FIG. 7, in step 61, the starting fuel injection pulse width Ti1 is calculated by the following equation.

Ti1 = TST × KNST × KTST (4)
Where TST: basic injection pulse width at start,
KNST: rotational speed correction coefficient,
KTST: Time correction coefficient,
Since the method of obtaining the basic injection pulse width TST, the rotational speed correction coefficient KNST, and the time correction coefficient KTST at the start is well known, detailed description thereof is omitted.

  In step 62, it is determined whether or not the output of the air flow meter 32 has been input. If the output of the air flow meter 32 is not input, the steps 63 and 64 are skipped and the routine proceeds to a step 65, where the starting fuel injection pulse width Ti1 is moved to the final fuel injection pulse width Ti.

  On the other hand, when the output of the air flow meter 32 is input, the process proceeds from step 62 to step 63, and the normal fuel injection pulse width Ti2 is calculated by the following equation using the target equivalent ratio TFBYA obtained from FIG.

Ti2 = (Tp × TFBYA + Kathos) × (α + αm−1) × 2 + Ts
... (5)
Where Tp: basic injection pulse width,
TFBYA: target equivalent ratio,
Kathos: Transient correction amount,
α: Air-fuel ratio feedback correction coefficient,
αm: air-fuel ratio learning value,
Ts: Invalid injection pulse width,
The basic injection pulse width Tp, transient correction amount Kathos, air-fuel ratio feedback correction coefficient α, air-fuel ratio learning value αm, and invalid injection pulse width Ts in equation (5) are well known. For example, the basic injection pulse width Tp is calculated by the following equation.

Tp = K × Qa / Ne (6)
Where Qa: the intake air amount calculated from the air flow meter 32,
The air / fuel ratio of the air-fuel mixture is set to the stoichiometric air / fuel ratio by the constant K in the equation (6). Therefore, while the post-startup increase correction coefficient KAS is a positive value exceeding zero, the fuel injection amount (fuel injection pulse width Ti) from the fuel injection valve 21 is corrected to be increased.

  The transient correction amount Kathos in the equation (5) is a value that is basically calculated based on the engine load, the rotational speed, and the temperature of the fuel adhering portion in consideration of the fuel wall flow rate of the intake port wall. It is considered that sometimes this transient correction amount Kathos works to increase the fuel injection amount by the amount deprived as the fuel wall flow of the intake port wall from the fuel injection amount. As a result, the air-fuel ratio is excessively leaned. This is because the calculation of the transient correction amount Kathos does not take into account changes in the intake pressure or the intake port flow velocity.

  In steps 64 to 66, the starting fuel injection pulse width Ti1 and the normal fuel injection pulse width Ti2 are compared, and the larger one is selected as the final fuel injection pulse width Ti.

  The post-startup increase correction coefficient KAS is used for fuel injection when the normal fuel injection pulse width Ti2 is adopted as the final fuel injection pulse width Ti. That is, in the present embodiment, it is assumed that the normal fuel injection pulse width Ti2 is larger than the starting fuel injection pulse width Ti1 immediately before the timing t5 in FIG.

  The fuel injection pulse width Ti calculated in this way is transferred to the output register, and when the predetermined fuel injection timing is reached, the fuel injection valves 21 of the respective cylinders are opened sequentially only during the pulse width Ti.

  Here, the effect of this embodiment is demonstrated.

  According to the present embodiment (the invention according to claims 1 and 5), the ignition timing is set to the first ignition timing ADV1 (starting timing) at the timing when the engine rotation speed Ne from the cranking reaches the target rotation speed NSET during idling. Ignition timing) to the second ignition timing ADV2 (ignition timing for promoting catalyst warm-up) (see steps 26 and 32 in FIG. 5), and the engine rotational speed Ne is the target rotational speed when idling. The intake air amount from the throttle valve position to the combustion chamber 5 is supplied to the combustion chamber 5 so that the intake air amount necessary to maintain the engine rotation speed Ne at the target rotation speed NSET during idling is reached at the timing when it reaches NSET. In consideration of the response delay, the timing t1 before the predetermined period DT from the timing when the engine rotational speed Ne reaches the target rotational speed NSET during idling. The throttle valve 23 starts to open (see Steps 25, 26, 29, 30, and 31 in FIG. 5), so that the engine speed Ne reaches the target rotational speed NSET at the time of idling and suppresses the blow-up early. The exhaust temperature can be raised (see the solid line at the bottom of FIG. 2), and the catalyst activation time can be shortened while suppressing wasteful fuel consumption.

  In this case, the intake pressure and the intake air flow velocity of the intake port 4 may continue to change for a while after the engine rotation speed Ne reaches the target rotation speed NSET during idling. The fuel wall flow rate at the intake port wall decreases with changes in the intake pressure and the intake air flow velocity of the intake port 4, and the amount of fuel supplied to the combustion chamber 5 is insufficient accordingly, and the air-fuel ratio of the air-fuel mixture in the combustion chamber However, according to the present embodiment (the inventions described in claims 1 and 5), the engine becomes lean beyond the combustion stability limit, leading to an increase in HC and a drop in rotation from the target rotation speed NSET during idling. For example, starting from the timing at which the throttle valve 23 starts to open, after the engine speed Ne reaches the target speed NSET during idling, the change in the intake pressure or the intake air flow rate at the intake port 4 is settled. During this period, the fuel injection amount from the fuel injection valve 21 is temporarily increased by using the post-startup increase correction coefficient KAS (see steps 44, 45 and 51 in FIG. 6), so that the engine speed Ne is at the idling time. Even after the target rotational speed NSET has been reached, the intake air pressure or the intake air flow velocity of the intake port 4 may continue to change to a smaller value, the air-fuel ratio of the air-fuel mixture in the combustion chamber will exceed the combustion stability limit and become leaner. Can be prevented. As a result, it is possible to suppress an increase in HC after the engine rotational speed Ne reaches the target rotational speed NSET during idling and a decrease in rotation from the target rotational speed NSET during idling (see the solid line in the seventh stage in FIG. 2).

  In the embodiment, the post-startup increase correction coefficient KAS is used to increase the fuel injection amount so that the actual air-fuel ratio obtained when the fuel injection amount from the fuel injection valve 21 is temporarily increased becomes the stoichiometric air-fuel ratio. As described in the case of setting the increase amount, the actual air-fuel ratio obtained when the fuel injection amount from the fuel injection valve 21 is temporarily increased becomes a lean-side air-fuel ratio that does not exceed the combustion stability limit. Further, the increase amount of the fuel injection amount can be set using the post-startup increase correction coefficient KAS (invention according to claims 3 and 7). When the actual air-fuel ratio obtained when the fuel injection amount from the fuel injection valve 21 is temporarily increased becomes the lean air-fuel ratio that does not exceed the combustion stability limit, the fuel injection from the fuel injection valve 21 is performed. The CO and HC at the engine outlet can be reduced rather than the actual air-fuel ratio obtained when the amount is temporarily increased to be the stoichiometric air-fuel ratio.

  In addition to the embodiment, after the engine rotational speed Ne reaches the target rotational speed NSET during idling, the throttle valve opening, the fuel, and the fuel are adjusted so that the actual engine rotational speed Ne matches the target rotational speed NSET during idling. The feedback control may be performed using any one of the injection amount and the ignition timing (the inventions according to claims 4 and 8). According to such a configuration, even if the actual rotational speed Ne may hunt after the engine rotational speed Ne reaches the idle target rotational speed NSET, the engine rotational speed Ne can settle to the idle target rotational speed NSET. Can do.

  The ignition timing retardation processing procedure according to claim 1 is performed by steps 26, 32, and 33 in FIG. 5, and the intake air amount supply processing procedure is performed by steps 25, 26, 29, 30, and 31 in FIG. The increase processing procedure is performed by steps 44, 45 and 51 in FIG.

  The function of the ignition timing retarding means according to claim 5 is performed by steps 26, 32, 33 in FIG. 5, and the function of the intake air amount supplying means is performed by steps 25, 26, 29, 30, 31 of FIG. The function of the injection amount increasing means is performed by steps 44, 45 and 51 in FIG.

The schematic block diagram of the control apparatus of the engine of 1st Embodiment of this invention. The wave form diagram for demonstrating the effect | action of 1st Embodiment compared with the present control. The wave form diagram for demonstrating the control method of 1st Embodiment. The flowchart for demonstrating the setting of two flags. The flowchart for demonstrating calculation of an ignition timing command value and a throttle valve target opening. The flowchart for demonstrating calculation of target equivalence ratio. The flowchart for demonstrating calculation of a fuel injection pulse width. The wave form diagram for demonstrating the effect | action of 2nd Embodiment compared with the present control.

Explanation of symbols

5 Combustion chamber 9 First catalyst 14 Spark plug 21 Fuel injection valve 23 Throttle valve 31 Engine controller 33, 34 Crank angle sensor 36 Starter switch 37 Water temperature sensor

Claims (8)

In an engine provided with a catalyst that functions only after being activated in the exhaust passage and a fuel injection valve for injecting fuel in the intake passage,
Ignition timing retarding procedure that retards the ignition timing step by step from the ignition timing for starting to the ignition timing for promoting catalyst warm-up when the engine speed from cranking reaches the target rotational speed at idle When,
When the engine speed is at idle, the intake air amount necessary to maintain the engine speed at the target speed at idling is supplied to the combustion chamber when the engine speed reaches the target speed at idling. Intake air amount supply processing procedure for starting to open the throttle valve a predetermined period before the timing of reaching the target rotational speed of
The fuel injection amount from the fuel injection valve from the timing when the throttle valve starts to open until the change in the intake pressure or the intake air flow velocity at the intake port settles after the engine rotation speed reaches the target rotation speed during idling An engine control method comprising: a fuel injection amount increase processing procedure for temporarily increasing the fuel injection amount.   2. The timing according to claim 1, wherein the timing before the predetermined period before the timing at which the engine rotation speed reaches the target rotation speed during idling is the timing at which the engine rotation speed from cranking reaches the complete explosion rotation speed. The engine control method described.   From the fuel injection valve, the actual air-fuel ratio obtained when the fuel injection amount from the fuel injection valve is temporarily increased becomes the lean air-fuel ratio that does not exceed the theoretical air-fuel ratio or the combustion stability limit. 2. The engine control method according to claim 1, wherein an increase amount of the fuel injection amount is set.   After the engine speed reaches the target speed during idling, any one of the throttle valve opening, fuel injection amount, and ignition timing is set so that the actual engine speed matches the target speed during idling. 2. The engine control method according to claim 1, wherein feedback control is performed using the engine control method. In an engine provided with a catalyst that functions only after being activated in the exhaust passage and a fuel injection valve for injecting fuel in the intake passage,
Ignition timing retarding means for retarding the ignition timing step by step from the ignition timing for starting to the ignition timing for promoting catalyst warm-up when the engine speed from cranking reaches the target rotational speed at idle ,
When the engine speed is at idle, the intake air amount necessary to maintain the engine speed at the target speed at idling is supplied to the combustion chamber when the engine speed reaches the target speed at idling. Intake air amount supply means for starting to open the throttle valve a predetermined period before the timing to reach the target rotational speed of
The fuel injection amount from the fuel injection valve from the timing when the throttle valve starts to open until the change in the intake pressure or the intake air flow velocity at the intake port settles after the engine rotation speed reaches the target rotation speed during idling A fuel injection amount increasing means for temporarily increasing the engine control device.   6. The timing according to claim 5, wherein the timing before the predetermined period before the timing at which the engine rotation speed reaches the target rotation speed during idling is the timing at which the engine rotation speed from cranking reaches the complete explosion rotation speed. The engine control device described.   From the fuel injection valve, the actual air-fuel ratio obtained when the fuel injection amount from the fuel injection valve is temporarily increased becomes the lean air-fuel ratio that does not exceed the theoretical air-fuel ratio or the combustion stability limit. The engine control device according to claim 5, wherein an increase amount of the fuel injection amount is set.   After the engine speed reaches the target speed during idling, any one of the throttle valve opening, fuel injection amount, and ignition timing is set so that the actual engine speed matches the target speed during idling. 6. The engine control device according to claim 5, wherein feedback control is performed using the engine control device.