JP2006132543A - Controller for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To converge the number of revolutions into target number of revolutions in a short time when starting an engine. <P>SOLUTION: An electronic control unit (ECU) 10 of the engine 1 performs control of the number of revolutions of either of control of the number of revolutions of intake amount for controlling the number of revolutions of the engine to target number of revolutions by adjusting opening of an electronic throttle valve 16 of the engine in accordance with the number of revolutions when starting the engine and control of the number of revolutions at ignition time for controlling the number of revolutions of the engine to target number of revolutions by adjusting ignition time of the engine. After starting the engine, the ECU performs the operation for causing lag of ignition time by predetermined amount to heat catalyst and reducing this lag amount gradually and sets high reduction speed of lag amount at ignition time for heating catalyst when it controls the number of revolutions at ignition time so that lag amount becomes zero in a short time. Consequently, interference of the control of the number of revolutions at ignition time with the operation for heating catalyst is prevented to converge the number of revolutions of the engine into target number of revolutions in a short time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 the engine speed to a target speed when the engine is started.

When the engine is started, particularly when the engine is cold, combustion is likely to deteriorate, and the engine speed may become unstable. When combustion deteriorates, problems such as deterioration of engine startability, deterioration of engine exhaust properties, vibration due to unstable rotation speed after start-up, and noise increase occur.
For this reason, various control devices have been proposed for stabilizing the engine speed by preventing the deterioration of combustion when the engine is started.

  For example, an example of this type of control device is described in Patent Document 1. The device of Patent Document 1 controls the engine intake air amount and the ignition timing in a feedback manner so that the engine speed matches the predetermined target speed during idling after the engine is started. Try to keep on.

Japanese Patent Application Laid-Open No. 5-222997 JP 2000-291467 A

  However, when the engine speed is controlled by the intake air amount during the warm-up operation immediately after the engine start as in the device of Patent Document 1, the engine combustion may be deteriorated particularly in the idling operation after the cold start. is there. For example, in an engine equipped with a fuel injection valve that injects fuel into the engine intake port, the injected fuel does not vaporize and adheres to the intake port wall surface in a liquid state when the engine is cold start, and the concentration of vaporized fuel is insufficient It may become. In particular, when the engine is cold-started or when low-volatile fuel (hereinafter referred to as “heavy fuel”) is used, the amount of vaporized fuel actually sucked into the cylinder is reduced because the fuel is not sufficiently vaporized. As a result, the air-fuel ratio of the air-fuel mixture may become lean and combustion may worsen. In such a case, if the throttle valve opening is increased in order to increase the intake air amount, the intake pipe negative pressure on the downstream side of the throttle valve decreases (absolute pressure increases). However, it may become difficult to vaporize and the deterioration of combustion may increase.

  In order to solve the above problem, the applicant of the present application has already controlled the engine speed by adjusting the throttle valve opening (engine intake air amount) in Patent Document 2 described above, and the engine combustion deteriorated. In such a case, a control device has been proposed in which the engine speed control by adjusting the throttle valve opening is stopped and the engine speed is controlled by adjusting the engine ignition timing.

  In the device of Patent Document 2 described above, deterioration of the engine combustion state is determined based on the peak rotational speed at the time of starting the engine, rotational fluctuation, and the like. The combustion deterioration is prevented by switching from the rotational speed control by adjusting the ignition timing or the rotational speed control by adjusting the throttle valve opening to the rotational speed control by increasing the fuel injection amount.

  However, in the device of Patent Document 2, the engine speed control itself is performed at the time of engine start (in this specification, the period from the start of the engine start operation (cranking) to the steady idle operation is referred to as “engine start”). The timing for starting the process is not sufficiently considered. For example, after the start operation (cranking) is started, the engine speed rapidly increases when combustion is started in all cylinders of the engine, reaches a peak speed at start, and then decreases again to a constant speed. . The engine speed control at the time of engine start requires that the engine speed be converged to a predetermined target engine speed in a short time, but in a state where the engine speed has changed as described above after the engine start operation is started. Depending on the timing at which the rotational speed control is started, the time until the rotational speed converges after the rotational speed control is started differs.

Further, in the device of the above application, although switching from the rotational speed control by adjusting the intake air amount to the rotational speed control by adjusting the ignition timing is performed depending on the deterioration of the combustion state, the rotational speed control by adjusting the ignition timing after switching is performed. Depending on the control method, there is a problem that it takes a long time to converge the engine speed to the target speed.
In view of the above problems, an object of the present invention is to provide a control device for an internal combustion engine that can converge an engine speed to a target speed in a short time when the engine is started.

  According to the first aspect of the present invention, at the time of starting the engine, the engine speed is controlled to a predetermined target speed by intake amount speed control for feedback control of the engine intake air amount according to the engine speed, Ignition that determines whether or not engine combustion has deteriorated at the start of the engine, and controls the engine speed to the target speed by feedback control of the engine ignition timing according to the engine speed from the intake air speed control when the combustion deteriorates In a control device for an internal combustion engine that switches to a timing rotational speed control to control a rotational speed at engine startup to a target rotational speed, a catalyst for further promoting the temperature rise of an exhaust purification catalyst disposed in the engine exhaust passage when the engine is started The ignition timing is retarded by a predetermined catalyst warm-up delay amount compared to after the temperature rise, and the catalyst warm-up retard amount is adjusted to zero after a predetermined time has elapsed from the start of the engine start operation. A catalyst warm-up means for changing the warm-up retarding amount is provided, and the catalyst warm-up means is shorter when the ignition timing rotational speed control is performed than when the ignition timing rotational speed control is not performed. Provided is a control device for an internal combustion engine that changes a catalyst warm-up retard amount so that the retard amount becomes zero.

  That is, the invention of claim 1 is provided with a catalyst warm-up means for retarding the ignition timing for raising the catalyst temperature when the engine is started. On the other hand, when the deterioration of the combustion occurs and the ignition timing rotation speed control is performed, the engine ignition timing is advanced in order to prevent a decrease in the engine rotation speed due to the deterioration of the combustion. For this reason, when combustion deterioration occurs, the ignition timing retarding operation by the catalyst warm-up means and the ignition timing advance operation by the ignition timing rotational speed control may occur simultaneously, and the catalyst warm-up operation and the rotational speed are performed. In some cases, the control interferes with each other, and it takes a long time to converge the engine speed to the target speed. In the present embodiment, when ignition timing rotation speed control is performed, the catalyst warm-up retardation amount decreases earlier than when the engine starts normally (when ignition timing rotation speed control is not performed) so that it becomes zero. Change the catalyst warm-up retardation amount. Thus, the catalyst warm-up operation is prevented from interfering with the ignition timing rotational speed control, and the engine rotational speed converges to the target rotational speed in a short time.

  According to the invention described in claim 2, when the engine is started, the engine rotational speed is controlled to a predetermined target rotational speed by the intake air rotational speed control that feedback-controls the engine intake air amount in accordance with the engine rotational speed. Ignition that determines whether or not engine combustion has deteriorated at the start of the engine, and controls the engine speed to the target speed by feedback control of the engine ignition timing according to the engine speed from the intake air speed control when the combustion deteriorates In a control device for an internal combustion engine that switches to a timing rotational speed control to control a rotational speed at engine startup to a target rotational speed, a catalyst for further promoting the temperature rise of an exhaust purification catalyst disposed in the engine exhaust passage when the engine is started Catalyst warm-up means for retarding the ignition timing by a predetermined catalyst warm-up delay amount compared to after the temperature rise, and means for detecting the peak rotational speed at the start after the start of the engine start operation, When the ignition timing rotation speed control is performed, the warming-up unit is configured to set the catalyst warm-up delay amount to a predetermined reference peak rotation speed and the start time peak as compared to a case where the ignition timing rotation speed control is not performed. There is provided a control device for an internal combustion engine which is set to be small by an amount corresponding to a difference from the rotational speed.

  That is, in the second aspect of the invention, as in the case of the twelfth aspect, the catalyst warm-up retardation amount is set to a small value in order to prevent interference between the catalyst warm-up operation and the ignition timing rotation speed control. At this time, the catalyst warm-up retardation amount is set to be small by an amount corresponding to the difference between the reference peak rotational speed and the starting peak rotational speed. As described above, the difference between the reference peak rotational speed and the starting peak rotational speed varies depending on the degree of deterioration of combustion. Further, when the degree of deterioration of combustion is large (that is, when the above-mentioned peak rotational speed difference is large), the advance amount of the ignition timing is large in the ignition timing rotational speed control. Therefore, in the present invention, the catalyst warm-up delay amount is greatly reduced as the peak rotational speed difference increases, and the ignition timing advance angle in the ignition timing rotational speed control is affected by the catalyst warm-up delay amount. I am trying not to. Thus, the catalyst warm-up operation is prevented from interfering with the ignition timing rotational speed control, and the engine rotational speed converges to the target rotational speed in a short time.

  According to the invention described in claim 3, at the time of starting the engine, the engine rotational speed is controlled to a predetermined target rotational speed by intake amount rotational speed control that feedback-controls the engine intake air amount in accordance with the engine rotational speed. Ignition that determines whether or not engine combustion has deteriorated at the start of the engine, and controls the engine speed to the target speed by feedback control of the engine ignition timing according to the engine speed from the intake air speed control when the combustion deteriorates In a control device for an internal combustion engine that switches to a timing rotational speed control to control a rotational speed at engine startup to a target rotational speed, a catalyst for further promoting the temperature rise of an exhaust purification catalyst disposed in the engine exhaust passage when the engine is started A catalyst warm-up means for retarding the ignition timing by a predetermined catalyst warm-up delay amount as compared with after the temperature rise is provided, and the catalyst warm-up means is configured to perform an ignition timing at the time of performing the ignition timing rotation speed control. Provided is a control device for an internal combustion engine that sets the catalyst warm-up retardation amount to be smaller according to the feedback correction amount of the ignition timing in the ignition timing rotation speed control than when the rotation speed control is not performed. .

  That is, in the invention of claim 3, the reduction of the catalyst warm-up delay amount when the ignition timing rotation speed control is performed is set according to the feedback correction amount of the ignition timing rotation speed control. When the decrease in the rotational speed due to the deterioration in combustion is large, the feedback correction amount of the ignition timing in the ignition timing rotational speed control is set to be large and the ignition timing is greatly advanced. In this case, if the catalyst warm-up retardation amount is large, the ignition timing cannot be sufficiently advanced, and the required number of revolutions cannot be increased. In the present invention, the catalyst warm-up delay amount is set according to the feedback correction amount of the ignition timing, for example, by setting the catalyst warm-up delay amount so that the catalyst warm-up delay amount is significantly reduced when the feedback correction amount is large. The warm-up operation is prevented from interfering with the ignition timing rotation speed control. For this reason, the engine speed is converged to the target speed in a short time without being influenced by the catalyst warm-up operation.

  According to the invention described in each claim, in the rotational speed control at the time of starting the engine, there is a common effect that the engine rotational speed can be smoothly converged to the target rotational speed in a short time.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic view showing the overall configuration when the present invention is applied to an automobile internal combustion engine. In FIG. 1, 1 is an internal combustion engine body, 2 is a surge tank provided in the intake passage of the engine 1, 2a is an intake manifold that connects the surge tank 2 and the intake port of each cylinder, and 16 is an upstream side of the surge tank 2. A throttle valve 7 disposed in the intake passage is a fuel injection valve that injects pressurized fuel into the intake port of each cylinder of the engine 1.

  In this embodiment, the throttle valve 16 is provided with an actuator 16a such as a stepper motor, and takes a degree of opening corresponding to a control signal input from the ECU 10 described later. That is, as the throttle valve 16 of the present embodiment, a so-called electronically controlled throttle valve that can take an opening degree that is independent of the driver's accelerator pedal operation amount is used. The throttle valve 16 is provided with a throttle opening sensor 17 for generating a voltage signal corresponding to the operation amount (opening) of the throttle valve.

In FIG. 1, 11 is an exhaust manifold for connecting the exhaust ports of the cylinders to a common collective exhaust pipe 14, 20 is a three-way catalyst disposed in the exhaust pipe 14, and 13 is an exhaust merging portion (three-way catalyst 20) of the exhaust manifold 11. An upstream air-fuel ratio sensor 15 disposed upstream) is a downstream air-fuel ratio sensor disposed in the exhaust pipe 14 downstream of the three-way catalyst 20. The three-way catalyst 20 can exhaust air-fuel ratio flowing to purify HC in the exhaust gas when in the vicinity of the stoichiometric air-fuel ratio, CO, three components of the NO _X at the same time. The air-fuel ratio sensors 13 and 15 are used for exhaust air-fuel ratio detection when feedback-controlling the fuel injection amount to the engine so that the engine air-fuel ratio becomes a predetermined target air-fuel ratio during normal engine operation.

In the present embodiment, an intake pressure sensor 3 for generating a voltage signal corresponding to the intake pressure (absolute pressure) in the surge tank is provided in the surge tank 2 in the intake passage, and the water jacket 8 of the cylinder block of the engine body 1 is also provided. Is provided with a water temperature sensor 9 that generates an electrical signal of an analog voltage corresponding to the temperature of the cooling water.
The output signals of the throttle valve opening sensor 17, the intake pressure sensor 3, the water temperature sensor 9, and the air-fuel ratio sensors 13 and 15 are input to the A / D converter 101 with a built-in multiplexer of the ECU 10 described later.

  Reference numerals 5 and 6 in FIG. 1 denote crank angle sensors disposed in the vicinity of a cam shaft and a crank shaft (not shown) of the engine 1. The crank angle sensor 5 generates a reference position detection pulse signal every 720 °, for example, in terms of the crank angle, and the crank angle sensor 6 generates a crank angle detection pulse signal every 30 ° of the crank angle. The pulse signals of the crank angle sensors 5 and 6 are supplied to the input / output interface 102 of the ECU 10, and the output of the crank angle sensor 6 is supplied to the interrupt terminal of the CPU 103 of the ECU 10. The ECU 10 calculates the rotational speed (rotational speed) of the engine 1 based on the crank angle pulse signal interval from the crank angle sensor 6 and uses it for various controls.

  The electronic control unit (ECU) 10 of the engine 1 is configured as, for example, a microcomputer, and when the ROM 104, RAM 105, and main switch are turned off in addition to the A / D converter 101 with built-in multiplexer, the input / output interface 102, and the CPU 103. However, a backup RAM 106, a clock generation circuit 107, and the like that can be stored are provided.

The ECU 10 performs basic control of the engine 1 such as fuel injection amount control and ignition timing control of the engine 1 based on the intake pressure, the throttle valve opening, and the engine speed. In this embodiment, the engine is started as described later. At the time of the engine (from the start of cranking to the steady idle operation after the complete explosion), the engine speed is controlled so that the engine speed is maintained at the target speed.
In order to perform the above control, the ECU 10 performs an A / D conversion routine executed at regular intervals, an intake pressure (PM) signal from the intake pressure sensor 3, a throttle opening (TA) signal from the throttle opening sensor 17, a water temperature The coolant temperature (THW) signal from the sensor 9 is A / D converted and input.

The input / output interface 102 of the ECU 10 is connected to the fuel injection valve 7 via a drive circuit 108 to control the fuel injection amount and the injection timing from the fuel injection valve 7.
Further, the input / output interface 102 of the ECU 10 is connected to each ignition plug 111 of the engine 1 via the ignition circuit 110 to control the ignition timing of the engine and to the actuator 16a of the throttle valve 16 via the drive circuit 113. The actuator 16a is driven to control the throttle valve 16 opening.

Next, the engine speed control of the present embodiment will be described.
In this embodiment, the ECU 10 sets a predetermined engine speed at the time of engine start, that is, from the start of the engine start operation (start of cranking) until the stable idle operation after completion of engine warm-up is performed. The engine speed is controlled at the time of starting to maintain the engine speed (generally, a fast idle engine speed for promoting engine warm-up). Normally, at the start of engine cranking, the fuel injection amount of the engine is set to an amount obtained by adding a correction corresponding to the intake air temperature (atmospheric temperature) and atmospheric pressure to the basic start injection amount determined from the coolant temperature and the engine speed. The Then, after the cranking is started, it is determined that the engine speed has exceeded a predetermined speed (for example, about 400 rpm) higher than the cranking speed (that is, combustion has started in each cylinder and the engine has reached a complete explosion state). After that, the fuel injection amount is set to an amount obtained by multiplying the basic fuel injection amount according to the engine intake air amount and the engine speed by a predetermined coefficient. The basic fuel injection amount is a fuel injection amount required for maintaining the engine combustion air-fuel ratio at the stoichiometric air-fuel ratio. The predetermined coefficient is for compensating for the fuel adhering to the intake port wall surface at the start of the engine and the deterioration of the fuel vaporization state due to the low temperature. The predetermined coefficient is a value greater than 1 at the time of engine start. The engine combustion air-fuel ratio is set to be richer than the stoichiometric air-fuel ratio.

  Further, when the engine is started, the temperature of the exhaust purification catalyst (shown by 20 in FIG. 1) disposed in the exhaust passage is low, and the catalyst cannot exhibit the exhaust purification function. Therefore, after the engine is started, it is necessary to raise the catalyst temperature to the activation temperature as soon as possible and to start exhaust purification by the catalyst. For this reason, in order to raise the exhaust gas temperature during normal engine start and raise the catalyst temperature in a short time, the engine ignition timing is retarded compared to during normal operation.

  As described above, the fuel injection amount at the time of starting the engine is appropriately set according to various factors. Therefore, if the engine is originally in a normal state, fluctuations in the rotational speed due to deterioration of combustion are less likely to occur when the engine is started. . However, even if the engine is normal, there may be a case where the rotational speed fluctuates due to deterioration of combustion at the start. For example, if the properties of fuel (gasoline) used in the engine are different, combustion deterioration at the time of starting tends to occur. The fuel injection amount at the time of starting the engine is set based on the use of fuel having standard properties. For this reason, for example, when a fuel having lower volatility than the standard fuel (hereinafter, referred to as “heavy fuel”) is used in the engine, deterioration of combustion may occur particularly at the time of engine cold start. That is, since the heavy fuel has low volatility, even when the same amount of fuel as the standard fuel is injected, the ratio of the fuel adhering to the wall surface of the intake port without being vaporized increases and is actually supplied into the cylinder. The amount of fuel that can be reduced. For this reason, the combustion air-fuel ratio of the engine shifts to a leaner side than usual, and the engine rotational speed becomes unstable due to deterioration of combustion.

  In general, as a method of preventing instability of the engine speed at the start and maintaining the engine speed at a predetermined target speed, feedback control of the engine intake air amount based on the engine speed (intake amount speed control) ) Is performed. In the intake air amount speed control, when the engine speed is lower than the target speed, the throttle valve 16 opening is increased (the engine intake air amount is increased) to increase the speed, and the speed is higher than the target speed. In this case, the rotational speed is maintained at the target rotational speed by performing feedback control based on the rotational speed, which reduces the rotational speed by reducing the throttle valve opening (reducing the intake air amount). However, when heavy fuel is used, the deterioration of engine combustion cannot be suppressed by the intake air amount rotational speed control, and the starting rotational speed cannot be maintained at the target rotational speed.

  For example, if heavy combustion fuel is used and the combustion air-fuel ratio of the engine becomes a lean air-fuel ratio and the combustion deteriorates when the engine is started, the intake air speed control increases the engine speed when the engine speed decreases due to combustion deterioration. Therefore, the throttle valve opening is increased. However, when the throttle valve opening is increased, the negative pressure in the intake passage on the downstream side of the throttle valve is reduced (the absolute pressure is increased), so that the injected fuel becomes more difficult to vaporize. For this reason, the engine combustion air-fuel ratio further shifts in the lean direction, resulting in an increase in combustion deterioration.

In this embodiment, when it is determined that the reduction in the engine speed at the start due to the deterioration of combustion cannot be compensated for by the intake air amount rotational speed control, the combustion deterioration is performed by performing the ignition timing rotational speed control instead of the intake air amount rotational speed control. Sometimes the engine speed is accurately maintained at the target speed.
In the ignition timing rotational speed control, an operation for maintaining the engine rotational speed at the target rotational speed is performed by feedback control of the ignition timing based on the engine rotational speed. When the engine is started, as described above, the engine ignition timing is retarded due to catalyst warm-up. On the other hand, when heavy fuel is used, the combustion speed of the air-fuel mixture in the cylinder decreases due to the lean air-fuel ratio. For this reason, by advancing the engine ignition timing to compensate for the decrease in the combustion speed, the output torque in the cylinder increases, and the engine speed increases. As a result, even when heavy fuel is used and engine combustion deteriorates, the engine speed can be accurately matched with the target speed.

  When the ignition timing rotation speed control is performed, the ignition timing is generally advanced as compared with the case where the ignition timing rotation speed control is not performed, so that the engine exhaust temperature is lowered and the catalyst warm-up is delayed. For this reason, in the present embodiment, when the engine is started, first, the intake air amount rotational speed control is performed, and only when the deterioration of combustion is determined, the switching from the intake air amount rotational speed control to the mechanical point control during ignition is performed. Suppressing deterioration of engine exhaust properties due to warm-up delay.

  Further, the method for determining combustion deterioration used in the present invention is not particularly limited, and any method may be used as long as it can accurately determine combustion deterioration. For example, after the engine start operation (cranking) is started, when the combustion is started in all the cylinders (that is, when the engine is in a complete explosion state), the engine speed rapidly increases and reaches the peak speed at start-up. Then decline. The peak rotational speed at start-up decreases as the degree of deterioration of engine combustion increases (the lower the volatility of the fuel used). For this reason, the starting peak rotational speed (when using normal fuel with good volatility) when combustion deterioration has not occurred is set in advance as the reference peak rotational speed, and the actual starting peak rotational speed is set. It is also possible to determine that the deterioration of combustion has occurred when is lower than the reference peak rotational speed by a predetermined value or more. In addition, when it is determined that the deterioration of combustion occurs due to the above, the ignition timing rotation speed control may be started immediately without performing the intake air amount rotation speed control at the time of starting the engine, When starting, the intake air amount rotational speed control is performed first, and then it is determined that the intake air amount rotational speed control cannot maintain the rotational speed at the target rotational speed (for example, the intake air amount feedback correction amount in the intake air amount rotational speed control is predetermined). It is also possible to switch to ignition timing rotational speed control (when it increases beyond the value).

  By the way, when starting speed control is performed by intake air amount speed control and ignition timing speed control as described above, the start timing of start speed control, setting of control parameters at the start, and the like become problems. That is, in starting speed control, it is desirable that the engine speed is converged to a target speed corresponding to the fast idle speed in as short a time as possible after the start of the engine starting operation. However, depending on the control start timing and the control parameter setting at the start of the control, there is a problem that the rotation speed fluctuation increases or the tracking speed to the target rotation speed decreases, and the convergence to the target rotation speed is delayed. . For example, as will be described later, it is generally impossible to control the engine speed until the engine speed reaches the peak speed after the start of the engine starting operation. For this reason, if the engine speed control is started simultaneously with the start of the engine start operation, the engine speed cannot be accurately controlled, and the intake air amount and the feedback correction amount of the ignition timing are set to an excessively large value by the engine speed control. If the rotational speed control becomes possible, the fluctuation of the rotational speed may increase. Also, when the actual engine speed is in the region near the target speed at the start of the speed control, for example, if a control parameter such as the feedback control gain is set to a large value, the engine speed overshoot or undershoot There is a case where a chute occurs and the convergence to the target rotational speed is delayed.

In the engine speed control according to the present invention, which will be described below, the engine speed can be made smooth and short by appropriately setting the control timing in the engine speed control at the start of the engine speed control or the engine speed control. It is possible to converge to the target speed over time.
Hereinafter, specific embodiments of the engine speed control at the start of the present invention will be described.
(1) First Embodiment In this embodiment, after the engine start operation (cranking) is started, the rotational speed control is started when the amount of air taken into the engine becomes equal to the intake passage volume on the downstream side of the throttle valve. By doing so, the timing for starting the rotational speed control is set appropriately, and the engine rotational speed is smoothly converged to the target rotational speed in a short time after the control starts.

  FIG. 2 is a diagram showing a general change over time in the engine speed when the engine is started with the throttle valve 16 opening being constant. As shown in FIG. 2, the engine speed increases after cranking starts, and when an explosion occurs in all the cylinders, it suddenly increases and reaches the peak speed (point a in FIG. 2). Then, after reaching the peak rotational speed, the engine rotational speed decreases again and becomes idling (point b).

In FIG. 2, although the throttle valve 16 is held constant, the rotational speed suddenly rises at the time of start and the peak rotational speed is generated for the following reason.
That is, when the engine is stopped, the intake passage pressure downstream of the throttle valve 16 is equal to the atmospheric pressure, and a relatively large amount of air is stored in the intake passage between the throttle valve 16 and each cylinder. When the engine starts to rotate, the air stored on the downstream side of the throttle valve is drawn into the cylinder all at once. For this reason, at the start of the engine starting operation, a large amount of air is sucked into the cylinder in the same manner as when the throttle valve is fully opened, and the engine speed rapidly increases with the complete explosion of the engine. However, after the entire amount of air stored on the downstream side of the throttle valve is sucked into the cylinder, only the amount of air corresponding to the throttle valve opening is supplied into the cylinder, so that the rotational speed decreases. For this reason, after starting the engine starting operation, the engine speed temporarily rises temporarily, and a starting peak speed is generated.

  As described above, in order to make the engine speed coincide with the target speed at an early stage, it is desirable to start the speed control as early as possible. However, while the air stored in the intake passage on the downstream side of the throttle valve is being sucked into the cylinder when the engine is started, it is the same as the throttle valve being held fully open, It is difficult to control the rotational speed by any of the ignition timing rotational speed controls. In addition, when the engine speed control is started at this time, the intake air speed control and the ignition timing engine speed control control the engine so that the intake air amount is significantly reduced or the ignition timing is greatly retarded in order to reduce the engine speed. Proceed. For this reason, after reaching the peak rotational speed at start-up, when the rotational speed is reduced, the rotational speed is significantly reduced from the target rotational speed, and there is a problem that convergence to the target rotational speed is delayed.

  In the present embodiment, the amount of air sucked into the engine after the start of the engine start operation is integrated, and the rotational speed control is started when this integrated value reaches the intake passage volume on the downstream side of the throttle valve. It has been solved. That is, after the amount of air stored in the intake passage on the downstream side of the throttle valve is drawn into the engine at the start of the engine starting operation, the engine speed can be controlled by the speed control. Therefore, in this embodiment, it is determined from the integrated value of the intake air amount of the engine that the amount of intake air equal to the amount stored downstream of the throttle valve has been sucked into the engine, and the rotational speed control is started from that point. . Thus, since the engine speed can be controlled immediately after the engine start operation is started, the engine speed can be converged to the target engine speed in a short time.

FIG. 3 is a flowchart for explaining the start operation of the rotational speed control at the start of the present embodiment. This operation is performed as a routine executed by the ECU 10 at regular intervals.
When the operation of FIG. 3 starts, in step 301, the engine speed NE and the throttle valve opening THA detected by the corresponding sensors 6 and 17 are read. In step 303, the current intake volume efficiency η _V is calculated based on the NE and THA. The volumetric efficiency η _V is a ratio of the amount of air actually taken into the engine and the total exhaust amount of the engine, and is a function of the throttle valve opening THA and the engine speed NE. In this embodiment, the relationship between the value of η _V and THA, NE is obtained by operating the actual engine by changing the throttle valve opening and the engine speed in advance and measuring the engine intake air amount. The value of η _V is stored in the ROM 104 of the ECU 10 as a numerical table using THA and NE. In step 303, the value of the volumetric efficiency η _V is read from this numerical table based on the throttle valve opening THA and the rotational speed NE.

Next, in step 305, the integrated value of the amount of air (volume) actually taken into the engine is increased by (η _V × V _d / 2) × NE × K _T.
Here, η _V is the intake volume efficiency calculated in step 303, V _d is the engine displacement, NE is the engine speed (RPM), and K _T is a constant represented by K _T = ΔT / 60. ΔT is the execution interval (seconds) of this operation. That is, in the present embodiment, since the engine 1 is a four-cycle engine, the amount of air sucked per one rotation of the engine is represented by (η _V × V _d / 2). Further, NE × K _T represents how many revolutions the engine has performed between the previous execution of this operation and the current execution of this operation. Therefore, the value of (η _V × V _d / 2) × NE × K _T represents the amount of air (volume) taken into the engine after the previous execution of this operation. Since the initial value of ΣQ is set to 0, the value of ΣQ accurately represents the integrated value of the engine intake air amount up to the present by executing step 305 at regular time intervals (ΔT). .

As described above, after calculating the integrated value ΣQ, it is determined in step 307 whether or not the current intake air amount integrated value ΣQ has reached the predetermined value V _vol . Here, V _vol is the total intake passage downstream of the throttle valve 16. If ΣQ <V _vol in step 307, that is, the entire amount of air stored downstream of the throttle valve 16 is not sucked into the engine, and accurate rotation speed control cannot be performed. This operation is finished as it is. Further, when ΣQ ≧ V _vol , the entire amount of air stored on the downstream side of the throttle valve is sucked into the engine, so that it is possible to carry out accurate rotation speed control. Therefore, in this case, the process proceeds to step 309, the value of the rotation speed control execution flag FB is set to 1, and the operation is ended.

When the flag FB is set to 1, execution of the intake air amount rotational speed control and ignition timing rotational speed control described above is permitted by a routine separately executed by the ECU 10, and the intake air amount rotational speed control or combustion deteriorates. If so, ignition timing rotational speed control is executed.
(2) Second Embodiment Next, another embodiment of the starting operation of the engine start speed control of the present invention will be described. Also in the present embodiment, as in the first embodiment, the rotational speed can be controlled, and at the same time, the control is started to converge the rotational speed to the target rotational speed in a short time. In the first embodiment, however, the engine Whereas the control start time is determined based on the intake air amount, the present embodiment is different in that the control start time is determined based on the engine speed.

  As described above, while the air stored on the downstream side of the throttle valve is being sucked into the engine after the engine start operation is started, the engine speed increases regardless of the throttle valve opening, and the total amount of the stored air is After being drawn into the engine, the engine speed decreases to a speed corresponding to the throttle valve opening. Therefore, when the engine speed starts to decrease, that is, when the engine speed reaches the starting peak speed described with reference to FIG. 2, the entire amount of air stored on the downstream side of the throttle valve is sucked into the engine. Can be thought of as

Therefore, in this embodiment, the engine speed is monitored after the start of the engine starting operation, and the rotational speed control is started from the time when it is determined that the rotational speed has reached the starting peak rotational speed.
4 and 5 are flowcharts for explaining the rotation speed control start operation of the present embodiment. FIG. 4 is a flowchart showing a detection operation for detecting that the engine speed has reached the start peak speed after the start operation of the engine is started, and FIG. 5 is a start speed control based on whether or not the start peak speed has been reached. It is a flowchart which shows start operation. The operations shown in FIGS. 4 and 5 are performed by routines executed by the ECU 10 at regular intervals.

In the operation of FIG. 4, first, in step 401, it is determined whether or not the value of the peak detection flag FP is set to 1. The peak detection flag FP is a flag that is set to 1 in step 415, which will be described later, when the engine speed reaches the starting peak speed, and the initial value is set to 0.
When the value of the peak detection flag FP is set to 1 in step 401, it is not necessary to perform peak detection again, and thus this operation ends without executing step 403 and the subsequent steps.

If FP ≠ 1 in step 401, that is, if peak detection has not been completed, then in step 403, the current engine speed NE is read, and whether or not the current peak detection condition is satisfied in steps 405 and 407. Is judged. In the present embodiment, the peak detection operation is performed only when the engine speed NE is equal to or greater than the predetermined value NE _S (step 405) and a predetermined time has elapsed after the start of the engine start operation (step 407). The These conditions are for preventing erroneous detection of the starting peak rotational speed. That is, before the engine reaches a complete explosion state, the combustion of the engine is not stable, and the engine speed fluctuates without increasing uniformly, so that a small peak may occur in the engine speed. In this embodiment, in order to prevent erroneous detection of this small rotation speed peak as the starting peak rotation speed, the engine rotation speed is greater than or equal to a predetermined value NE _S (NE _S is determined that the engine is in a complete explosion state). And the detection of the peak rotational speed is started after a predetermined time (for example, 1000 ms) has elapsed since the start of the start operation. If one or both of the steps 405 and 407 are not satisfied, this operation is immediately terminated without executing step 409 and the subsequent steps.

If the conditions of steps 405 and 407 are satisfied, the process proceeds to step 409, where the engine speed NE _i-1 at the time of the previous operation execution is compared with the current engine speed NE read in step 403. . When NE ≧ NE _i−1, that is, when the current engine speed is increasing, an operation of replacing the value of the starting peak speed NEP with the engine speed NE measured this time (step 411) is performed. At the same time, the value of NE _i-1 is updated in preparation for the next execution of this operation, and this operation is terminated.

On the other hand, if NE <NE _i-1 in step 409, that is, if the engine speed has started decreasing after reaching the starting peak speed, the routine proceeds to step 415, where the value of the peak detection flag FP is set. Set to 1 to finish the operation. As a result, while the engine speed continues to increase, the peak engine speed NEP is updated using the current engine speed, but when the engine speed starts decreasing, the value of NEP is not updated. Is set to the peak rotational speed at the start. Also, once the starting peak rotational speed is detected, the peak detection flag FP is set to 1, so that the peak detection operation is not executed from the next time (step 401).

  In the operation of FIG. 5, it is first determined in step 501 whether or not the engine is currently idling. Whether or not the engine is currently in idling is determined based on whether or not the throttle valve opening THA is set to a predetermined opening during idling. If the engine is currently idling, it is next determined in step 503 whether the value of the peak detection flag FP set by the operation of FIG. 4 is 1 (detected). If FP = 1, it means that the engine speed has reached the starting peak speed, so the routine proceeds to step 505, the speed control execution flag FB is set to 1, and the operation is terminated. Thus, the intake air amount rotational speed control (or ignition timing rotational speed control) is executed as in the first embodiment. On the other hand, if FP ≠ 1, since the engine speed has not yet reached the starting peak rotational speed and it is not time to start the rotational speed control, the value of the rotational speed control flag FB is not changed. The operation is finished as it is.

If it is determined in step 501 that the engine is not currently idling, that is, if the vehicle is currently running, this operation is immediately terminated because it is not necessary to start the rotational speed control.
According to the present embodiment, it is possible to easily determine the start time of the rotational speed control without calculating the integrated value of the intake air amount.
(3) Third Embodiment Next, a third embodiment of the present invention will be described.

In the present embodiment, as in the second embodiment, the engine speed control is started when the engine speed reaches the starting peak engine speed. At the start of the engine speed control, the control target engine speed is set to the actual peak engine speed. After that, the target rotational speed is gradually changed to the final target rotational speed (fast idle rotational speed) with the passage of time.
When the rotational speed control is started when the peak rotational speed at the start is reached, the rotational speed at the start of the control is considerably higher than the fast idle rotational speed. For this reason, when the fast idle rotation speed is set as the target rotation speed from the start of the control, the rotation speed control is performed in a direction to decrease the actual rotation speed. On the other hand, the engine speed naturally decreases after reaching the peak speed, so if control is performed in a direction that significantly reduces the engine speed at this time, the engine speed will greatly decrease beyond the fast idle speed. Therefore, it may take time to converge to the fast idle speed that is the final target speed. Therefore, in this embodiment, when starting the rotational speed control when the starting peak rotational speed is reached, the control target rotational speed is set to the actual starting peak rotational speed, and then the control target rotational speed is gradually set to the final rotational speed. An operation to reduce the target engine speed to the fast idle speed is performed. As a result, there is no large deviation between the actual engine speed and the target control speed even after the peak speed is reached, so control that greatly reduces the speed is not performed, and the engine speed is reduced in a short time after the start of control. The number will converge to the target speed.

  Further, in the present embodiment, when the engine speed is decreasing from the starting peak rotational speed and within a predetermined value from the fast idle rotational speed, that is, when the engine speed approaches the final target rotational speed while the rotational speed is decreasing, Further, an operation is performed so as to reduce the rate of decrease in the control target rotational speed. As described above, by reducing the decrease speed of the control target rotation speed in the vicinity of the final target rotation speed, occurrence of undershoot when the rotation speed decreases is further suppressed.

FIG. 6 is a flowchart for specifically explaining the target rotational speed setting operation of the present embodiment. This operation is performed by a routine executed by the ECU 10 at regular intervals.
When the operation starts in FIG. 6, in step 601, it is determined whether or not the current rotational speed control execution flag FB is set to 1. If FB ≠ 1, this operation is immediately performed without executing step 603 and subsequent steps. Exit.

On the other hand, if FB = 1 in step 601, it is determined in step 603 whether or not the current operation is executed first after the value of the flag FB changes from 0 to 1, and the FB value changes. Only when it is the first execution after that, step 605 is executed to perform an operation of setting an initial value of a variable KNE described later.
Also in this embodiment, the operations of FIGS. 4 and 5 are performed separately, and the value of FB is set to 1 at the same time as the engine reaches the starting peak rotational speed. A flag X in steps 603 and 607 is a flag used to execute step 605 only once immediately after the value of FB changes from 0 to 1.

In step 605, the initial value of KNE is set as KNE = NEP-NE _0. Here, NEP is the actual starting peak rotational speed at the time of starting the engine this time, and is set by the operation of FIG. NE ₀ is the final target rotational speed (fast idle rotational speed) of the rotational speed control. As will be described later, in this embodiment, the target rotational speed of the rotational speed control is set such that TNE is NE ₀ + KNE, and the value of KNE is reduced with time from the initial value.

Steps 613 and 615 are KNE reduction operations. In this embodiment, the decrease speed of KNE is changed depending on whether the actual engine speed NE is close to the final target value NE ₀ , that is, whether NE is equal to or less than NE + ΔNE ₁ . That is, in step 611, it is determined whether or not the rotational speed NE has become equal to or less than NE ₀ + ΔNE _{1. If} NE> NE ₀ + ΔNE ₁ (when the actual rotational speed is not close to the final target value), the operation is performed. relatively reducing large by a predetermined value K ₁ values of KNE every execution (step 613) Thus, the value of KNE is reduced with time at a relatively high speed. In step 611, if NE ≦ NE ₀ + ΔNE ₁ (when the actual rotational speed is close to the final target value), the value of KNE is set to a relatively small constant value K ₂ (K ₂ <K ₁ ) for each operation. Reduce (step 615). As a result, the value of KNE decreases with time at a relatively large speed from the start of control until it approaches the final target value, and changes so that the decreasing speed decreases when it approaches the final target value. In the present embodiment, the value of ΔNE ₁ is set to a constant value of about 100 RPM, for example.

In step 617, the target rotational speed TNE in the rotational speed control is set as TNE = NE ₀ + KNE. When the value of KNE becomes negative due to the decrease, the value of TNE is set to the final target rotational speed NE ₀ (steps 609 and 619).
According to the operation of FIG. 6, in this embodiment, when the rotational speed control is started when the starting peak rotational speed is reached, the control target rotational speed TNE is set to the actual peak rotational speed NEP (steps 605 and 617), and then the final Until the actual rotational speed approaches the target rotational speed, the speed decreases with time (steps 611 and 613). In the region where the actual rotational speed approaches the final target rotational speed NE ₀ , the rotational speed decreases at a relatively small speed. As a result (step 615), it reaches the final target rotational speed NE ₀ (steps 609 and 619).

6 is executed at regular time intervals by the ECU 10. However, if the operation of FIG. 6 is executed at every constant rotation angle of the engine crankshaft, in addition to the above, the control target rotational speed decrease speed is reduced. As the engine speed changes according to the engine speed, the control response can be further improved.
In the present embodiment, as described above, the control target rotational speed is gradually changed from the actual peak rotational speed to the final target rotational speed, so that the control target rotational speed also varies even when the actual starting peak rotational speed varies. A large deviation does not occur between the rotational speed and the actual rotational speed, and the engine rotational speed can be converged to the final target rotational speed in a short time. Further, in this embodiment, when the actual engine speed approaches the final target speed, the change speed of the control target speed is set to be small, so that an undershoot of the speed is prevented and the final target speed is prevented. The convergence time to the number is further shortened.
(4) Fourth Embodiment Next, a fourth embodiment of the present invention will be described.

  In the first to third embodiments described above, after the engine start operation is started, the rotation speed control is started when the rotation speed is in the vicinity of the starting peak rotation speed. For this reason, when the rotational speed control is started, the actual rotational speed is higher than the target rotational speed (for example, the fast idle rotational speed), and when the rotational speed control is started, the intake air amount or the ignition timing decreases the rotational speed. Will be corrected. However, in actuality, at the start of the engine, the rotational speed rapidly decreases after reaching the peak rotational speed. For this reason, if the rotational speed control is started when the rapid rotational speed reduction has occurred after reaching the peak rotational speed, the rotational speed may be excessively decreased, and convergence to the target rotational speed may be delayed.

Therefore, in this embodiment, the engine speed change speed after the start of the engine start operation is detected, and the engine speed is set to the target speed by starting the speed control from the time when the change speed becomes a predetermined value or less. It tries to converge in a short time.
FIG. 7 is a flowchart for explaining the start-up rotation speed control start operation according to this embodiment. This operation is performed by a routine executed by the ECU 10 at regular intervals.

  In FIG. 7, steps 701 to 705 indicate whether or not the rotation speed control start condition is satisfied. That is, in step 701, it is determined whether or not the engine is currently idling based on the opening of the throttle valve 16, and in step 703, it is determined based on the rotational speed control execution flag FB whether or not rotational speed control has already been started. The In step 705, it is determined whether or not a predetermined time (for example, about 2000 ms) has elapsed since the start of the engine start operation (cranking). When it is not the idling operation at step 701 and when the rotation speed control has already been started at step 703 (FB = 1), it is not necessary to start the rotation speed control further, so the operations after step 707 are executed. This operation is finished immediately. If it is determined in step 705 that the predetermined time has not elapsed since the start of the engine starting operation, the engine speed may not yet reach the starting peak speed. In this case, in order to avoid detecting a decrease in the rotational speed change speed in the vicinity of the starting peak rotational speed, the operation is similarly terminated without executing step 707 and subsequent steps.

If all of the conditions in steps 701 to 703 are satisfied, the current engine speed NE is read in step 707, and the speed change speed RNE from the speed NE _i-1 at the time of the previous operation execution to the present is calculated as RNE = | NE-NE _i-1 | In step 711, the value of NE _i-1 is updated in preparation for the next RNE calculation operation, and then the process proceeds to step 713.

In step 713, it is determined whether or not the rotational speed change speed calculated in step 711 has become equal to or smaller than a predetermined value RNE _0. If RNE ≦ RNE ₀ , the value of the rotational speed control execution flag FB is set to 1. Set.
As a result, in the present embodiment, the rotational speed control is started from the point of time when the rotational speed change speed becomes small, and the rotational speed converges to the target rotational speed in a short time.
(5) Fifth Embodiment Next, a fifth embodiment of the present invention will be described.

In the present embodiment, after the engine start operation is started, when the engine speed decreases after passing the starting peak speed, the speed control is started from the time when the target speed is crossed.
As described above, the engine speed decreases sharply after the starting peak speed is exceeded. For this reason, if the engine speed is started from a state in which the engine speed is still higher than the target engine speed after passing the peak engine speed, the engine speed control will further decrease the engine speed even though the engine engine speed is decreasing. In some cases, the rotational speed is excessively reduced.

  In this embodiment, the engine speed is controlled when the engine speed crosses the target engine speed (fast idle engine speed) while the engine engine speed decreases after reaching the peak engine speed, that is, when the actual engine speed becomes equal to the target engine speed. By starting the operation, an excessive decrease in the rotational speed is prevented. In other words, in the present embodiment, when the rotational speed control is started, the difference between the actual rotational speed and the target rotational speed is extremely small, and thus the actual rotational speed is not controlled in a significantly decreasing direction. For this reason, excessive reduction of the rotational speed at the start of control is prevented, and the rotational speed converges to the target rotational speed in a short time.

FIG. 8 is a flowchart for explaining the rotation speed control start operation of the present embodiment. This operation is performed by a routine executed by the ECU 10 at regular intervals.
Steps 801 and 803 in FIG. 8 show the determination of whether or not the rotation speed control start condition is satisfied, similar to steps 701 and 703 in FIG. Step 805 indicates whether or not the current rotational speed has passed the starting peak rotational speed. FP is a peak detection flag set by the same operation as that of FIG. If FP ≠ 1 in step 805, that is, if the engine speed has not reached the starting peak engine speed, the engine speed control is started when the engine engine speed matches the target engine speed while the engine speed is increasing. In order to prevent this, the operations after step 807 are not executed.

If at step 805 it is after the current peak rotational speed pass reads the rotational speed NE in step 807, determines whether the decreased rotational speed NE read in step 809 is less than the target rotational speed NE _0. If NE ≦ NE ₀ , the value of the rotation speed control execution flag FB is set to 1 in step 811 and the operation is terminated. As a result, the rotational speed control is started when the engine rotational speed decreases to the target rotational speed after passing the starting peak rotational speed.

If it is determined in step 809 that the engine speed NE has not yet decreased to the target speed NE ₀ , the process proceeds to step 813, and whether or not a predetermined time (eg, about 3000 ms) has elapsed since the start of the engine start operation. If the predetermined time has elapsed, even if the engine speed has not decreased to the target speed, the process proceeds to step 811 to start the speed control. This is because, when the decrease in the engine speed after reaching the peak at the time of starting is relatively gradual, it takes a relatively long time for the engine speed to decrease to the target speed. This is because the rotational speed control is started without waiting for this to quickly converge the rotational speed to the target rotational speed. In this case, since the speed of decrease of the engine speed is relatively moderate, even if the speed control is started before the speed decreases to the target speed, no significant speed reduction occurs.
(6) Sixth Embodiment Next, a sixth embodiment of the present invention will be described.

  In the present embodiment, when switching from the intake air amount rotational speed control to the ignition timing rotational speed control when the combustion of the engine deteriorates, the ignition timing rotational speed control is started with the ignition timing advanced by a predetermined amount stepwise. I have to. Normally, when the combustion deteriorates, the decrease in the rotation speed after reaching the peak rotation speed is large, so at the time when switching from the intake air amount rotation speed control to the ignition timing rotation speed control is performed when the engine combustion deterioration is worse, the engine rotation speed is higher than the target rotation speed. It is low. For this reason, it is necessary to increase the rotational speed early after switching to the ignition timing rotational speed control.

Therefore, in the present invention, at the time of switching to the ignition timing rotational speed control, the ignition timing rotational speed control is started in a state where the ignition timing is advanced by a predetermined amount compared to before the switching. As a result, the engine speed increases simultaneously with the start of the ignition timing speed control, and reaches the target speed in a short time.
The engine speed control switching operation, the intake air quantity engine speed control operation, and the ignition timing engine speed operation when the engine combustion deteriorates will be specifically described below with reference to FIGS. 9 to 12.

In the present embodiment, it is determined whether engine combustion has deteriorated by comparing the starting peak rotational speed NEP detected by the operation of FIG. 4 with a predetermined reference peak rotational speed NEP ₀ . When the combustion of the engine deteriorates, the starting peak rotational speed NEP decreases according to the degree of deterioration of combustion. Therefore, for example, an appropriate reference peak rotational speed NEP ₀ (constant value) is set in advance, and the difference DNP (= NEP ₀ −NEP) between the reference peak rotational speed NEP ₀ and the actual starting peak rotational speed NEP Is calculated, the DNP value increases as the degree of combustion deterioration increases. For this reason, the degree of combustion deterioration can be expressed using the value of DNP.

In this embodiment, at the start of the rotational speed control, the intake air quantity rotational speed control is first performed, the presence / absence of combustion deterioration is determined based on the value of the peak rotational speed difference DNP, and the intake air is determined according to the degree of combustion deterioration. The timing for switching from quantity rotation speed control to ignition timing control is set.
FIG. 9 is a flowchart for explaining the engine speed control operation at the start of the present embodiment. This operation is performed as a routine executed by the ECU 10 at regular intervals.

When the operation starts in FIG. 9, it is determined in step 901 whether or not the engine is currently idling, and in step 903 whether or not the value of the rotation speed control execution flag FB is 1.
If the engine is currently idling and the value of the rotation speed control execution flag FB is set to 1 (execution), the process proceeds to step 905, where the predetermined reference peak rotation speed NEP ₀ and the operation of FIG. A difference DNP from the starting peak rotational speed NEP detected in step S3 is calculated. In step 907, the upper limit value EQ _MAX of the feedback correction amount EQ of the intake air amount rotational speed control is set according to the value of DNP, and the operation is terminated.

On the other hand, if either of the conditions in steps 901 and 903 is not satisfied, the process proceeds to step 909, and both the values of the intake air amount rotational speed control execution flag CN and the ignition timing rotational speed control execution flag IN are set to 0. To finish the operation.
In the present embodiment, when the intake air amount rotational speed control execution flag CN is set to 1, the later-described intake air amount rotational speed control is executed, and when the ignition timing rotational speed control execution flag IN is set to 1, the ignition timing rotational speed. Control is executed. Note that the initial value of the intake air amount rotational speed control execution flag CN is set to 1 (execution). For this reason, when the value of the flag FB is set to 1 during the idling operation (steps 901 and 903), the intake air amount rotational speed control is started first.

FIG. 10 is a flowchart for explaining the intake air amount rotational speed control operation. In this operation, the value of the intake air amount feedback correction amount EQ is set based on the difference DNE between the target engine speed NE ₀ and the actual engine speed NE. Further, when the value of the feedback correction amount EQ reaches the upper limit value EQ _MAX , switching from the intake amount rotational speed control to the ignition timing rotational speed control is performed.

That is, in step 1001, it is determined whether or not the value of the intake air speed control execution flag CN is 1 (execution). If CN = 1, the value of DNE is calculated in steps 1003 and 1005, and in step 1007 An integral value IDNE of the deviation DNE is calculated. In step 1009, the differential value DDNE of the deviation DNE is calculated as DDNE = DNE−DNE _i−1 . DNE _i-1 is the value of DNE at the previous execution of this operation. The value of DNE _i-1 is updated at step 1011 every time the operation is executed.

In step 1013, the value of the feedback correction amount EQ for the intake air amount is calculated as EQ = α ₁ × DNE + α ₂ × IDNE + α ₃ × DDNE. That is, the value of the feedback correction amount EQ is set by proportional differential control based on the difference DNE between the target rotational speed and the actual rotational speed.
After setting the value of the correction amount EQ as described above, it is determined in step 1015 whether or not the value of the correction amount EQ has reached the upper limit value EQ _MAX set by the operation of FIG. 9, and the upper limit value has not been reached. In step 1017, the target value QT of the engine intake air amount is calculated as QT = Q _CAL + EQ. Q _CAL is a target intake air amount determined by the engine speed and the accelerator pedal depression amount of the driver. In step 1019, the opening degree of the throttle valve 16 is controlled in accordance with the calculated engine intake air amount QT.

If the feedback correction amount EQ has reached the upper limit value EQ _MAX in step 1015, the routine proceeds to step 1021, where the value of the intake air amount rotational speed control execution flag CN is set to 0 (stop), and the ignition timing rotational speed is reached. The value of the control flag IN is set to 1 (execution). As a result, the intake air amount rotational speed control is stopped from the next time (step 1001), and ignition timing rotational speed control described later is started. That is, switching from intake air amount rotational speed control to ignition timing rotational speed control is performed.

In the present embodiment, the switching to the ignition timing rotational speed control is performed when the feedback correction amount EQ reaches the upper limit EQ _MAX for the following reason.
That is, when the ignition timing rotation speed control is performed, the ignition timing is generally advanced, so that the exhaust temperature decreases and it takes time to increase the temperature of the exhaust purification catalyst. For this reason, when switching to the ignition timing rotation speed control is performed, the engine operation time in a state where the exhaust purification catalyst does not reach the activation temperature becomes long, and the exhaust property at the time of engine start tends to deteriorate as a whole. In the present embodiment, the engine speed is controlled as much as possible by controlling the intake air amount to prevent the deterioration of the exhaust properties, and the ignition timing only when it is determined that the engine speed cannot be controlled by the intake air amount due to combustion deterioration or the like. Switching to rotation speed control is performed. For example, when engine combustion deteriorates and the rotational speed falls below the target rotational speed, the feedback correction amount EQ is set to increase in order to increase the engine rotational speed in the intake air amount rotational speed control. Further, the value of EQ continues to increase as long as the actual engine speed NE is lower than the target speed by the action of the integral term IDNE. Therefore, when the value of EQ reaches a certain large value, it can be determined that it is difficult to control the engine speed to the target speed by the intake air speed control. Therefore, in this embodiment, when the EQ value reaches a certain upper limit EQ _MAX , it is determined that the reduction in the rotational speed due to the deterioration of the combustion cannot be recovered by the intake air rotational speed control, and the ignition timing rotational speed control is performed. Is switched.

Further, as described above, in the present embodiment, the value of the upper limit EQ _MAX is set according to the value of the peak rotational speed difference DNP (FIG. 9, step 907).
FIG. 11 is a diagram showing the value of EQ _MAX set in step 907 of FIG. As shown in FIG. 11, the value of EQ _MAX is set to a relatively large positive constant value EQMAX0 in the region where DNP is a negative value (when the engine starting peak speed NEP is higher than the reference speed NEP ₀ ). . Further, the value of EQ _MAX decreases as DNP increases in a region where DNP is positive, and is set to 0 when DNP is equal to or greater than a predetermined value DNP ₁ .

As described above, the value of DNP represents the degree of deterioration of combustion, and the combustion becomes worse as the value of DNP increases. For this reason, in this embodiment, as the degree of deterioration of combustion increases, the upper limit value EQ _MAX is set to be smaller so that the switching timing from the intake amount rotation speed control to the ignition timing rotation speed control becomes earlier. When the DNP value is larger than the predetermined value DNP ₁ , that is, when it is determined that the deterioration of combustion is considerably large, the upper limit value EQ _MAX is set to 0, so that the intake air amount immediately after the start of the rotational speed control Switching from the rotational speed control to the ignition timing rotational speed control is performed.

Next, the ignition timing rotation speed control operation of this embodiment will be described. In the present embodiment, as described above, when switching from the intake air amount rotational speed to the ignition timing rotational speed control is performed, the deviation DNE between the target rotational speed NE ₀ and the actual rotational speed NE is performed as in the intake air amount rotational speed control. Based on this, the feedback correction amount of the ignition timing is set by proportional integral derivative control. However, in the present embodiment, when the ignition timing rotation speed control is started in addition to the feedback correction amount, the ignition timing is advanced by a predetermined amount K ₃ . When the engine speed control is switched from the intake air quantity engine speed control to the ignition timing engine speed control, the deterioration of the combustion occurs, and therefore the engine speed decreases according to the deterioration of the combustion. For this reason, when the ignition timing rotational speed control is started, it is necessary to significantly advance the ignition timing to increase the engine rotational speed to the target rotational speed. In this case, if waiting for the ignition timing feedback correction amount to increase by feedback control based on the rotational speed difference, the increase in the rotational speed may be delayed. Therefore, in this embodiment, when the ignition timing rotational speed control is started, the ignition timing is uniformly advanced by a predetermined value K ₃ compared to before the start regardless of the engine rotational speed. As a result, the engine speed increases simultaneously with the start of the ignition timing speed control, and converges to the target speed in a short time.

FIG. 12 is a flowchart for explaining the ignition timing rotation speed control operation of the present embodiment. This operation is performed as a routine executed by the ECU 10 at regular intervals.
In FIG. 12, when the operation starts, it is determined in step 1201 whether or not the value of the ignition timing rotation speed control execution flag IN is set to 1. This operation is executed only when the value of the flag IN is set to 1. Thus, as soon as the value of the flag IN is set to 1 by the intake air amount rotational speed control operation of FIG. 10, switching from the intake air amount rotational speed control to the ignition timing rotational speed control is performed.

In steps 1203 1207, Fig. 10, similarly to steps 1003 1009, the difference between the actual rotational speed NE and the target revolving speed NE ₀ DNE, and the integral value of the DNE IDNE, differential value DDNE is calculated.
In the present embodiment, the engine ignition timing AOP is calculated using the above DNE, IDNE, and DDNE.
AOP = EA _CAL + K ₃ + β ₁ × DNE + β ₂ × IDNE + β ₃ × DDNE
-EACAT
Set as In step 1215, the ignition timing AOP set as described above is set in the ignition circuit 110, and this operation ends.

In the above equation, the ignition timing AOP is represented by the crank angle up to the top dead center of each cylinder, and the ignition timing advances when the value of AOP increases. EA _CAL is a basic ignition timing determined from the engine coolant temperature, and β ₁ , β ₂ , and β ₃ are coefficients of a proportional term, an integral term, and a differential term (feedback control constant), respectively. K ₃ is a predetermined positive value, and EACAT is a catalyst warm-up delay amount. The catalyst warm-up retarding amount EACAT will be described later.

As described above, also in the ignition timing rotational speed control, the feedback correction amount (β ₁ × DNE + β ₂ × IDNE + β ₃ × DDNE) is set by proportional integral differential control based on the difference DNE between the target rotational speed and the actual rotational speed. However, the ignition timing control is different in that the advance amount K ₃ is uniformly added to the basic ignition timing EA _CAL .

That is, when the ignition timing rotation angle control is started, the ignition timing is advanced by K _{3 in a} stepped manner compared to before the start. As a result, the speed of increase of the rotational speed is increased and the engine rotational speed converges to the target rotational speed NE ₀ in a short time.
Next, the step advance amount K ₃ at the start of the ignition timing will be described.
The step advance amount K ₃ may be set as a constant value, but in the present embodiment, the value of K ₃ is set according to the degree of deterioration of combustion. That is, if the degree of deterioration of combustion is large, the decrease in engine speed at the start of ignition timing rotational speed control is also large, and it is necessary to set the speed of increase in rotational speed to be large. In the present embodiment, as the degree of combustion deterioration, that is, the value of the peak rotational speed difference DNP is larger, the value of the step advance amount K ₃ is set to be larger, thereby increasing the rotational speed.

FIG. 13 is a diagram showing the relationship between the step advance amount K ₃ and the peak rotational speed difference DNP in the present embodiment.
As shown in FIG. 13, the step advance amount K ₃ is set to 0 when the DNP value is negative, increases linearly when the DNP value is between 0 and a predetermined value DNP ₂ , and the DNP value Is set to a constant value in the region of DNP ₂ or more. As a result, the step advance amount K ₃ is set to a larger value as the deterioration of combustion increases.

Next, the reference peak rotational speed NEP ₀ used for calculating DNP will be described. As for the value of NEP ₀ , the starting peak rotational speed when combustion deterioration does not occur is previously measured by experiment, and this starting peak rotational speed is stored in the ROM of the ECU 10 as the reference peak rotational speed NEP _0. May be. However, the starting peak rotational speed may vary from engine to engine due to individual differences in the engine or changes in internal friction due to aging. Therefore, in this embodiment, the reference peak rotational speed NEP ₀ is set based on the starting peak rotational speed NEP detected every time the engine is actually started.

That is, the ECU 10 stores the peak rotational speed NEP detected at the time of engine start in the RAM, and whether or not the value of the ignition timing rotational speed control execution flag IN is set to 1 when the engine warm-up is completed and normal operation is started. That is, it is determined whether or not the ignition timing rotation speed control is executed at the time of the current engine start. If ignition timing rotation speed control is not executed at the time of the current engine start, it can be determined that the deterioration of combustion did not occur at the time of the current start. Therefore, in this case, the starting peak rotational speed stored at the time of starting this time is adopted as the value of the reference peak rotational speed NEP ₀ and is stored in the backup RAM and used for the next engine starting operation. If ignition timing rotation speed control is executed at the time of the current engine start, the reference peak rotation speed NEP ₀ up to the previous time is not updated and is used for the next engine start operation. This makes it possible to accurately determine the deterioration of engine combustion even when there is a change in internal friction or the like due to each engine or due to aging.
(7) Seventh Embodiment Next, a seventh embodiment of the present invention will be described.

In the sixth embodiment, the intake air amount rotational speed control and the ignition timing rotational speed control are proportional integral differential control based on the difference DNE between the target rotational speed NE ₀ and the actual rotational speed NE. ₁ × DNE, β ₁ × DNE, integral terms α ₂ × IDNE, β ₂ × IDNE and differential terms α ₃ × DDNE, β ₃ × DDNE coefficients (feedback control constants) α ₁ , α ₂ , α ₃ , and The values of β ₁ , β ₂ , and β ₃ were fixed at constant values. On the other hand, in this embodiment, the value of the feedback control constant is set according to the rotational speed difference DNE and the change rate DDNE.

For example, when the engine speed is significantly lower than the target speed and the difference DNE from the target speed is increasing, the feedback correction amount (α ₁ × DNE + α ₂ × IDNE + α ₃ × DDNE) and (β ₁ × DNE + β ₂ × IDNE + β ₃ × DDNE) need to be greatly increased.

On the other hand, when the engine speed is approaching the target speed, the value of the rotational speed difference DNE is relatively small, and the rotational speed difference DNE is decreasing, the speed of increase of the rotational speed must be set small. Since an overshoot may occur with respect to the target rotational speed, the feedback correction amount needs to be set small.
In this case, if the feedback control constant is fixed to a constant value, the feedback correction amount is not necessarily set optimally, and convergence to the target rotational speed may be delayed.

In the present embodiment, by setting the value of the feedback control constant according to the rotational speed difference DNE and the increasing / decreasing tendency thereof (that is, the differential value DDNE of DNE), the feedback correction amount is optimized according to the changing tendency of the rotational speed. By setting the value, the time for the rotation speed to converge to the target rotation speed is further shortened.
In the present embodiment, the integral term coefficients α ₂ and β ₂ of the feedback control constant are changed according to the actual rotational speed change tendency. Since the integral term is an integrated value of the rotational speed difference, even if the rotational speed difference changes, the change of the integral term itself is relatively small. For this reason, compared with the proportional term and the differential term, the integral term is less likely to reflect the changing tendency of the rotational speed. Therefore, when changing the feedback control constant according to the rotational speed change trend, the integral term coefficient may be changed according to the rotational speed change tendency to increase the degree of reflection of the rotational speed change tendency to the integral term. This is because it is most effective in reducing the convergence time of the rotational speed. Of course, if the proportional term and the differential term are also changed in accordance with the change tendency of the rotational speed, a greater effect can be obtained.

First, the integral term in the present embodiment will be described.
In the sixth embodiment, the integral term IDNE is calculated as the integrated value ΣDNE of the rotational speed difference DNE, and IDNE is multiplied by constant coefficients α ₂ and β ₂ when calculating the feedback correction amount. That is, in the case of the intake air amount rotational speed control of FIG. 10, the feedback correction amount EQ is calculated as (1) EQ = α ₁ × DNE + α ₂ × IDNE (= ΣDNE) + α ₃ × DDNE. On the other hand, in this embodiment, the integral term IDNE is calculated in advance by multiplying DNE by α ₂ at the time of integration and calculating as Σ (α ₂ × DNE). Instead, the feedback correction amount EQ is (2 ) EQ = α ₁ × DNE + IDNE (= Σ (α ₂ × DNE)) + α ₃ × DDNE Equations (1) and (2) are the same when α ₂ is a constant value.

However, in the present embodiment, the value of the integral term coefficient α ₂ is changed in accordance with the rotation speed difference DNE and the change rate DDNE. Thereby, the change tendency of the rotation speed is more appropriately reflected in the integral term.
That is, the value of α ₂ is set according to the values of DNE and DDNE. However, in the present embodiment, the optimum α ₂ (in the case of ignition timing rotation speed control) is actually set according to each combination of DNE and DDNE. The value of β ₂ ) is set by experiment or the like, and a value QIDNE (= α ₂ × DNE) obtained by multiplying DNE by α ₂ is stored in the ROM 104 of the ECU 10 in the form of a numerical map using DNE and DDNE. It is. Then, the value of QIDNE (= α ₂ × DNE) is read from this numerical map as the amount of increase / decrease of the integral term, using the values of DNE and DDNE calculated every time the operation is executed in FIG. The value of the feedback correction amount EQ is calculated as EQ = α ₁ × DNE + IDNE (= ΣQIDNE) + α ₃ × DDNE.

FIG. 18 is a diagram illustrating setting of the value of the change amount QIDNE (= α ₂ × DNE) of the integral term.
In FIG. 18, the horizontal axis represents the rotational speed difference DNE (= NE ₀ −NE), and the vertical axis represents the side or the rate DDNE. In FIG. 18, a straight line N ₁ indicates a rotational speed difference DNE = 0 (a state where the target rotational speed and the actual rotational speed match), and a straight line N ₂ indicates a DDNE = 0 (a state where the engine rotational speed is stable). ), Respectively. Further, as will be described later, the straight line I is in a state where QIDNE = 0, and in this embodiment, the straight line I is given as a straight line having a slope of 45 degrees passing through points DNE = 0 and DDNE = 0.

Consider the case where DNE <0 and DDNE <0 in FIG. 18 (point A in FIG. 18). In this case, since DNE (= NE ₀ −NE) <0, the engine speed NE is higher than the target speed NE ₀ , and since DDNE <0, the speed difference is larger than the previous negative value. It is a value. That is, in this case, the rotational speed is already higher than the target rotational speed, but the rotational speed is further increasing. Therefore, in this case, it is necessary to reduce the value of the feedback correction amount EQ by reducing the value of the integral term IDNE. Therefore, in this embodiment, in such a case, the value of the integral term change amount QIDNE (= α ₂ × DNE) becomes negative and the rotational speed difference DNE becomes a negative value (the higher the rotational speed). ) And the value of α ₂ is set so that QIDNE becomes a large negative value as the change rate DDNE becomes a large negative value (as the rotational speed increases more rapidly).

On the other hand, when DNE> 0 and DDNE> 0 (FIG. 18, point B), the rotational speed is lower than the target rotational speed, and the rotational speed difference is increasing (that is, the rotational speed is decreasing). For this reason, in this case, it is necessary to increase the value of the feedback term EQ by quickly increasing the value of the integral term IDNE. Therefore, in this case, the value of the integral term change amount QIDNE (= α ₂ × DNE) becomes positive and the rotational speed difference DNE is a large positive value (lower rotational speed), and the change rate DDNE. The value of α ₂ is set so that QIDNE becomes a large positive value as the value of QIDNE becomes a large positive value (as the rotational speed decreases more rapidly).

Next, consider the case of point C and point D in FIG. In this case, both DNE <0 and DDNE> 0, and the rotational speed is higher than the target rotational speed, but the rotational speed difference is being reduced (the rotational speed is decreasing). In this case, it is necessary to change the sign of QIDNE according to the size of DNE and DDNE.
For example, at point C in FIG. 18, the DNE value is a relatively large negative value, so the rotational speed is much higher than the target rotational speed. For this reason, although the rotational speed tends to decrease, it is preferable that the rotational speed decrease rate is slightly increased so that the rotational speed reaches the target rotational speed quickly. Therefore, in this case, the value of QIDNE is set to a relatively small negative value. On the other hand, since the DNE value is a relatively small negative value at point D, the rotational speed is higher than the target rotational speed, but is relatively close to the target rotational speed. Moreover, since DDNE> 0, the rotational speed difference is being reduced (rotation is reduced). For this reason, if the value of IDNE remains large, overshooting occurs, and the rotational speed may drop beyond the target rotational speed. Therefore, at point D, the value of QIDNE is set to a relatively small positive value, and the value of IDNE is gradually increased.

Similarly to the above, when looking at points E and F (DNE> 0, DDNE <0) in FIG. 18, the value of QIDNE is a relatively small negative value at point E and a relatively small positive value at point F. , Respectively.
Further, at the point on the straight line I in FIG. 18, the influence of the rotational speed difference DNE and the change tendency DDNE cancel each other, so that the value of the integral term IDNE is not increased or decreased and the previous value is maintained as it is. To do. For this reason, QIDNE = 0 is set at the points on this line. For this reason, the straight line I is a boundary line between a region where QIDNE is positive and a region where QIDNE is negative. Further, in this embodiment, in order to stabilize the control, an area within a certain distance from the straight line I (area shown by hatching in FIG. 18) is provided, and in this area, the value of QIDNE is set to 0, and DNE and Even if the value of IDNE changes, the value of IDNE is not increased or decreased.

As described above, in the present embodiment, the value of QIDNE (= α ₂ × DNE) takes a positive value in the upper part of the hatched area in FIG. 18, takes a negative value in the lower part, and its absolute value is The larger the distance from the straight line I, the larger the value.
In this way, by setting the value of the feedback control constant (α ₂ , β ₂ ) for each operation execution according to the rotational speed difference DNE and the change rate DDNE, the feedback correction amount corresponds to the changing tendency of the rotational speed. Therefore, the convergence time of the rotation speed to the target rotation speed is shortened.
(8) Eighth Embodiment Next, an eighth embodiment of the present invention will be described.

In the present embodiment, by adjusting the ignition timing retard amount for catalyst warm-up during execution of the ignition timing rotation speed control, interference between the ignition timing speed control and the ignition timing retard angle for catalyst warm-up is reduced. Prevents the engine speed to converge to the target speed in a short time.
As described with reference to FIG. 12, during the ignition timing rotation speed control, the engine ignition timing AOP is determined based on the basic ignition timing EA _CAL (EA _CAL + K _{3 in} the example of FIG. 12) and the feedback correction amount (FIG. 12). In this example, it is set as a sum of β ₁ × DNE + β ₂ × IDNE + β ₃ × IDNE) plus a catalyst warm-up retardation amount (−EACAT). The catalyst warm-up retarding amount EACAT is provided to increase the exhaust temperature at the time of starting the engine and allow the exhaust purification catalyst to reach the activation temperature in a short time, and gradually increases after the start of the engine start operation and then gradually increases. It decreases and changes to 0 after a predetermined time has elapsed after the start operation is started.

In practice, the catalyst warm-up retarding amount EACAT is given in the form of EACAT = RF × EACATBASE. Here, EACATBASE is the basic catalyst warm-up delay amount, and is given in advance as a function of the engine coolant temperature. RF is a reflection coefficient, which is given as a function of time from the start of the engine start operation.
FIG. 14 is a diagram showing a time change after the start of the RF engine starting operation.

As shown in FIG. 14, the reflection coefficient RF is set to 0 from the start of the engine start operation to a predetermined time t ₁ to facilitate the engine start, and starts increasing after a few seconds have elapsed after the start operation has started. And when it increases to RF = 1, it is set so that it may start decreasing gradually after that and may decrease to 0. Therefore, the catalyst warm-up retarding amount EACAT also changes in the same manner as shown in FIG. 14 after the engine start operation is started. However, since the ignition timing rotation speed control is to change the engine ignition timing so that the rotation speed matches the target rotation speed, the rotation is performed when the catalyst warm-up delay amount EACAT increases or decreases during execution of the ignition timing rotation speed control. The ignition timing adjustment by the number control and the increase / decrease of EACAT interfere with each other, and the engine speed cannot be converged to the target speed in a short time.

Therefore, in the present embodiment, when the ignition timing rotational speed control is started, the catalyst warm-up delay amount EACAT (reflection coefficient RF) is quickly attenuated to zero, and the ignition timing retard for catalyst warm-up is ignited. This prevents interference with the rotational speed control.
FIG. 15 is a flowchart for explaining the catalyst warm-up retardation amount control operation of the present embodiment. This operation is performed as a routine executed by the ECU 10 at regular intervals.

  In this operation, when the ignition timing retard control is not executed, the value of EACAT is set as EACAT = RF × EACATBASE as usual, but when the ignition timing retard control is started, the catalyst warm-up retard The setting of the amount EACAT is stopped by the above formula, and the retardation amount EACAT is decreased from the current value by 0 by a certain amount. That is, in this embodiment, when the ignition timing rotational speed control is not executed, the catalyst warm-up retarding amount EACAT changes as shown by the solid line in FIG. 14, but for example, at the S point in FIG. When the control is started, the catalyst warm-up retarding amount EACAT decreases linearly as shown by the dotted line thereafter, and becomes zero in a shorter time than when the ignition timing rotational speed control is not executed. Be controlled.

  That is, when the operation starts in FIG. 15, in step 1501, it is determined from the value of the ignition timing rotation speed control execution flag IN whether or not the ignition timing rotation speed control is currently being executed. If IN ≠ 1, that is, if the ignition timing rotation speed control is not currently being executed, the routine proceeds to step 1503, where the catalyst warm-up retarding amount EACAT is set as EACAT = RF × EACATBASE. As a result, the catalyst warm-up delay amount EACAT changes as indicated by the solid line (normal time) in FIG. 14 after the engine start operation is started.

  On the other hand, if the ignition timing rotation speed control is currently being executed at step 1501 (IN = 1), the routine proceeds to step 1505, where the current catalyst warm-up delay amount is decreased by a constant value ΔEA, and In steps 1507 and 1509, the minimum value of EACAT is limited to zero. As a result, the value of EACAT decreases by a constant value ΔEA every time this operation is performed from the time when ignition timing rotation speed control is started (FIG. 14, dotted line), decays faster than normal time (FIG. 14, solid line), and decreases for a short time. 0.

For this reason, the ignition timing adjustment by the ignition timing rotation speed control and the catalyst warm-up delay angle are prevented from interfering with each other, and the engine rotation speed can be converged to the target rotation speed in a short time.
In the present embodiment, the catalyst warm-up delay amount starts decreasing with the start of the ignition timing rotational speed control. However, for example, the ignition timing rotational speed control is started even if the ignition timing rotational speed control is started because the deterioration of combustion is relatively small. May not be advanced too much. In such a case, if the catalyst warm-up retardation amount is attenuated early, the catalyst warm-up is delayed, so that the exhaust properties as a whole may deteriorate. For this reason, for example, instead of starting to decrease the catalyst warm-up delay amount simultaneously with the start of the ignition timing rotation speed control, when the ignition timing is advanced more than a certain degree by the ignition timing rotation speed control, that is, the deterioration of the combustion The decrease in the catalyst warm-up retardation amount may be started when it is determined that the degree is somewhat large.

In this case, instead of performing a decrease operation after step 1505 when the value of the ignition timing rotation speed control execution flag IN becomes 1 in step 1501 in FIG. 15, feedback correction in the ignition timing rotation speed control is performed in step 1501. Whether or not the value of the quantity (β ₁ × DNE + β ₂ × IDNE + β ₃ × DDNE in the example of FIG. 12) has become larger than a predetermined value, that is, the ignition timing tends to be advanced by a predetermined value or more by the ignition timing rotation speed control. If the feedback correction amount becomes equal to or greater than a predetermined value, the decrease operation in step 1507 and subsequent steps may be performed.
(9) Ninth Embodiment In the present embodiment, an operation for reducing the catalyst warm-up retarding amount is performed when the ignition timing rotation speed control is performed as in the eighth embodiment, but in the eighth embodiment, it is uniformly performed. While the catalyst warm-up retarding amount EACAT is decreased, the present embodiment is different in that EACAT is decreased according to the degree of deterioration of combustion.

As described above, when the degree of combustion deterioration is large, the ignition timing advance amount in the ignition timing rotation speed control becomes large. For this reason, if the catalyst warm-up retardation amount becomes a large value when the degree of deterioration of combustion is large, there is a possibility that accurate rotation speed control by ignition timing rotation speed control cannot be performed.
Therefore, in the present embodiment, the deviation (DNP = NE ₀ −NEP) of the peak rotational speed NEP at the time of starting the engine described above from the reference peak rotational speed NEP ₀ is used as a parameter for the degree of combustion deterioration, and the combustion deterioration is large (DNP). The catalyst warm-up delay amount is large so that the decrease in the catalyst warm-up delay amount is large, and when the combustion deterioration is small (when DNP is small), the catalyst warm-up delay amount is small. It is adjusting.

FIG. 16 is a flowchart for explaining the catalyst warm-up retardation amount control operation of the present embodiment. This operation is performed as a routine executed by the ECU 10 at regular intervals.
When the operation starts in FIG. 16, first, in step 1601, the catalyst warm-up delay amount EACAT is calculated as EACAT = RF × EACATBASE. In step 1603, it is determined based on the value of the ignition timing rotation speed control execution flag IN whether or not the ignition timing rotation speed control is currently being executed. If ignition timing rotation speed control is not currently being executed (when IN ≠ 1), this operation ends immediately. In this case, the catalyst warm-up retardation amount becomes the normal value set in step 1601. On the other hand, if the ignition timing rotation speed control is currently being executed (IN = 1), then in step 1605, a predetermined reference peak rotation speed of the starting peak rotation speed NEP detected at the time of engine start is determined. Based on the deviation DNP from NEP ₀ , the catalyst warm-up retardation amount reduction coefficient K ₄ (K ₄ ≦ 1) is determined. In step 1607, the value obtained by multiplying the coefficient K ₄ to the value of EACAT when calculated normally in step 1601 to end the operation is set as a catalyst warm-up delay amount EACAT.

Figure 17 is a graph showing the setting of a coefficient K _4. As shown in FIG. 17, the value of K ₄ is set to K ₄ = 1 is the value of the peak rotational speed difference DNP is negative region, the degree of DNP is larger value of DNP is a positive region (i.e. combustion deterioration It is set to a smaller value (the larger is). Accordingly, in step 1607 of FIG. 16, the larger the degree of combustion deterioration, the smaller the catalyst warm-up delay amount is set to a smaller value. Therefore, the ignition timing rotation speed control and the ignition timing retard for catalyst warm-up interfere with each other. It is prevented.

In the present embodiment, as shown in FIG. 17, the value of the coefficient K ₄ is continuously changed according to the value of the peak rotational speed difference DNP. However, for example, whether the value of DNP is a predetermined value or more. It is possible to simplify the control by setting the value of K ₄ in two stages according to the above.
In this embodiment, the coefficient K ₄ is set according to the peak rotational speed difference DNP. However, the feedback correction amount after the ignition timing rotational speed operation is started (in the example of FIG. 12, β ₁ × DNE + β ₂ × IDNE + β ₃ XDDNE) represents the amount of advance by ignition timing rotation speed operation. Therefore, it is possible to set the value of K ₄ using the same relationship as in FIG. 17 according to the value of the feedback correction amount.

It is a figure explaining the schematic structure of embodiment at the time of applying this invention to the internal combustion engine for motor vehicles. It is a figure explaining the time change of the rotation speed at the time of engine starting. It is a flowchart explaining an example of rotation speed control start operation at the time of engine starting. It is a flowchart explaining peak speed detection operation at the time of engine starting. It is a flowchart explaining rotation speed control start operation at the time of engine starting. It is a flowchart which shows an example of target rotational speed setting operation in rotational speed control. 7 is a flowchart for explaining another example of a rotation speed control start operation at the time of engine start. 7 is a flowchart for explaining another example of a rotation speed control start operation at the time of engine start. It is a flowchart explaining switching operation of intake air amount rotation speed control and ignition timing rotation speed control. 6 is a flowchart illustrating an example of an intake air amount rotation speed control operation. It is a figure which shows the setting of the parameter in operation of FIG. It is a flowchart explaining an example of ignition timing rotation speed control operation. It is a figure which shows the setting of the parameter in operation of FIG. It is a figure which shows the time change of the catalyst warm-up retardation amount. It is a flowchart explaining an example of catalyst warm-up retard amount control operation. It is a flowchart explaining other embodiment of catalyst warm-up retard amount control operation. It is a figure which shows the setting of the parameter in operation of FIG. It is a figure which shows the example of the setting of the parameter in operation of FIG.

Explanation of symbols

1 Internal combustion engine body 5, 6 Crank angle sensor 10 Electronic control unit (ECU)
16 Electronically controlled throttle valve 110 Ignition circuit

Claims (3)

When starting the engine, the engine speed is controlled to a predetermined target speed through intake air speed control that feedback-controls the engine intake air amount according to the engine speed, and whether or not engine combustion has deteriorated when the engine is started is determined. When the combustion deteriorates, the engine speed is switched from the intake air speed control to the target engine speed by feedback control of the engine ignition timing according to the engine speed. In a control device for an internal combustion engine that controls a rotational speed to a target rotational speed,
Further, in order to accelerate the temperature rise of the exhaust purification catalyst disposed in the engine exhaust passage at the time of engine start, the ignition timing is retarded by a predetermined catalyst warm-up delay amount as compared to after the catalyst temperature rise, and the catalyst warm-up delay time is increased. A catalyst warm-up unit is provided that changes the catalyst warm-up retarding amount so that the angular amount becomes zero after a predetermined time has elapsed from the start of the engine start operation. A control apparatus for an internal combustion engine, which changes a catalyst warm-up delay amount so that the catalyst warm-up delay amount becomes zero in a shorter time than when rotation speed control is not performed. When starting the engine, the engine speed is controlled to a predetermined target speed through intake air speed control that feedback-controls the engine intake air amount according to the engine speed, and whether or not engine combustion has deteriorated when the engine is started is determined. When the combustion deteriorates, the engine speed is switched from the intake air speed control to the target engine speed by feedback control of the engine ignition timing according to the engine speed. In a control device for an internal combustion engine that controls a rotational speed to a target rotational speed,
Further, a catalyst warm-up means for retarding the ignition timing by a predetermined catalyst warm-up delay amount compared to after the catalyst temperature rise in order to promote the temperature rise of the exhaust purification catalyst disposed in the engine exhaust passage when the engine is started, and the engine Means for detecting a starting peak rotational speed after the start operation is started, and the catalyst warm-up means is more effective when the ignition timing rotational speed control is not performed when the ignition timing rotational speed control is performed. A control device for an internal combustion engine, wherein a warm-up retardation amount is set to be smaller by an amount corresponding to a difference between a predetermined reference peak rotational speed and the starting peak rotational speed. When starting the engine, the engine speed is controlled to a predetermined target speed through intake air speed control that feedback-controls the engine intake air amount according to the engine speed, and whether or not engine combustion has deteriorated when the engine is started is determined. When the combustion deteriorates, the engine speed is switched from the intake air speed control to the target engine speed by feedback control of the engine ignition timing according to the engine speed. In a control device for an internal combustion engine that controls a rotational speed to a target rotational speed,
Furthermore, a catalyst warm-up means for retarding the ignition timing by a predetermined catalyst warm-up delay amount compared to after the catalyst temperature rise to promote the temperature rise of the exhaust purification catalyst disposed in the engine exhaust passage at the time of engine start, The catalyst warm-up means uses the catalyst warm-up delay amount when the ignition timing rotational speed control is performed as compared with the case where the ignition timing rotational speed control is not performed, and the ignition timing feedback in the ignition timing rotational speed control. A control device for an internal combustion engine, which is set to be small according to the correction amount.

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