JP4124101B2 - Engine control device - Google Patents

Description

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

The valve timing of the intake valve is advanced or retarded by continuously varying the rotational phase difference between the crankshaft and the intake valve camshaft, and the variable valve mechanism that continuously and variably controls the valve lift amount and operating angle of the intake valve. The variable valve timing mechanism is set to be low (small) by the variable valve mechanism at the time of first idling from the start, the valve timing is delayed by the variable valve timing mechanism, and the fuel injection timing is taken in. There is what is in the process (see Patent Document 1).
JP 2003-3872 A

  By the way, the reason why the intake valve lift amount is set to a small value and the fuel injection timing is set to the intake stroke in the above-mentioned Patent Document 1 is to accelerate the atomization of the injected fuel by increasing the intake air flow rate. As a result, it was found that the wall flow rate in the combustion chamber increased on the condition that the wall flow rate of the intake valve was large, and this increased the HC discharged from the engine.

  To explain this, when the wall flow rate at the umbrella back of the intake valve is large, when the large lift state is changed to the small lift state, the wall flow rate in the combustion chamber 5, particularly the wall flow rate adhering to the upper surface of the combustion chamber increases. This is because if the valve lift is small, the flow velocity of the intake air passing through the gap between the intake valve 15 and the intake port 4 wall increases, so that when the wall flow fuel adhering to the back of the intake valve umbrella is sucked into the combustion chamber, This is because it flies and adheres to the upper surface of the combustion chamber.

  On the other hand, if fuel is injected during the intake stroke, the spray from the fuel injection valve rides on the flow of intake air and is sucked into the combustion chamber, so the wall flow rate adhering to the back of the intake valve umbrella is injected during the exhaust stroke. However, the wall flow rate adhering to the cylinder surface in the combustion chamber is increased, although it is smaller than when it is done.

  Thus, according to the technique of the above-mentioned Patent Document 1, although the atomization of the fuel itself is promoted, both the flow rate on the upper surface of the combustion chamber and the cylinder surface in the combustion chamber are increased, resulting in an increase in HC. is there.

The present invention, in the wall flow rate is high condition of the intake valve over after startup starting and the boost pressure before it develops boost pressure develops, providing a device for reducing HC reduces wall flow in the combustion chamber The purpose is to do.

  Here, the “boost pressure” refers to the intake pipe pressure downstream of the intake throttle valve. Moreover, the above-mentioned “boost pressure develops” means that the boost pressure becomes smaller than the atmospheric pressure due to the pumping action by the piston.

As shown in FIG. 1, the present invention includes an intake valve (15), variable valve mechanisms (26, 27) capable of variably controlling the valve lift and valve timing of the intake valve (15), ignition, A fuel injection device (21) for injecting fuel from the intake port (4) toward the intake valve (15), and the engine controller (31) reaches a predetermined negative pressure. The fuel injection device (21) is controlled so that fuel injection is performed in the intake stroke at the start before starting, and the intake valve (15) and the exhaust valve (16) after the start in which the intake pipe pressure reaches a predetermined negative pressure The variable valve mechanism (26, 27) is ignited at the combustion stability limit, which is the ignition timing at the retarded angle side, at which the engine can be combusted in a stable state so that the overlap amount of the engine increases after the engine warm-up is completed. Is done Controlling sea urchin ignition device (14), respectively. In addition, the code | symbol was attached | subjected corresponding to description of embodiment, and this invention is not necessarily limited to this.

According to the present invention, after the start of the intake pipe pressure reaching a predetermined negative pressure, the overlap amount of the intake and exhaust valves is increased as shown by the two-dot chain lines in FIGS. High-temperature exhaust gas remaining in the room increases, fuel atomization is promoted, and unburned HC is reburned, whereby the amount of HC discharged from the engine after the start-up at which boost pressure develops can be reduced.

On the other hand, even if the overlap amount of the intake / exhaust valve is increased at the start- up before the intake pipe pressure reaches a predetermined negative pressure, the effect of promoting vaporization by blowing back cannot be obtained. For this reason, according to the present invention, the intake stroke injection is performed at the start, thereby promoting secondary atomization by intake. This can reduce the wall flow in the combustion chamber (see FIG. 33 third stage, two points of the fourth-stage chain line).

  In this way, since the intake air injection is performed at the start and the overlap amount of the intake and exhaust valves is increased after the start, the overlap amount of the intake and exhaust valves is increased at the start as shown in FIG. The HC emission amount at the engine outlet can be further reduced by an amount corresponding to the area shown by hatching (see the dashed line in the upper part of FIG. 3).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view for explaining a system according to a first embodiment of the present invention applied to an L-Jetronic gasoline injection engine.

  The air metered by the intake throttle valve 23 is stored in the intake collector 2 and then introduced into the combustion chamber 5 of each cylinder via the intake manifold 3. Fuel enters the intake port 4 at a predetermined timing (always an exhaust stroke from the start) from the fuel injection valve 21 (fuel injection device) disposed in the intake port 4 of each cylinder, more specifically, to the intake port 4. Injection is intermittently supplied toward the intake valve 15 (back of the umbrella) that exists so as to be blocked. Here, the fuel injection amount given to the fuel injection valve 21 is the engine rotational speed calculated by the engine controller 31 based on the intake air flow rate detected by the air flow meter 32 and the signals from the crank angle sensors (33, 34). It is calculated according to.

  The fuel injected toward the intake valve 15 is mixed with the intake air to form an air-fuel mixture, and the air-fuel mixture is confined in the combustion chamber 5 by closing the intake valve 15 and compressed by the rise of the piston 6, and the spark plug 14 (ignition device) ignites and burns. The gas pressure due to the combustion works to push down the piston 6, and the reciprocating motion of the piston 6 is converted into the rotational motion of the crankshaft 7. The combusted gas (exhaust gas) is discharged into the exhaust passage 8 when the exhaust valve 16 is opened.

The exhaust passage 8 includes three-way catalysts 9 and 10. The three-way catalysts 9, 10 can efficiently remove HC, CO and NOx contained in the exhaust gas simultaneously when the air-fuel ratio of the exhaust gas is in a narrow range centered on the stoichiometric air-fuel ratio. For this reason, the engine controller 31 determines the basic fuel injection amount from the fuel injection valve 21 according to the operating conditions, and feedback controls the air-fuel ratio based on the signal from the O ₂ sensor 35 provided upstream of the three-way catalyst 9. To do.

  The intake throttle valve 23 is driven by a throttle motor 24. Since the torque required by the driver appears in the amount of depression of the accelerator pedal 41 (accelerator opening), the engine controller 31 determines a target torque based on a signal from the accelerator sensor 42, and a target air for realizing this target torque. The amount is determined, and the opening degree of the intake throttle valve 23 is controlled via the throttle motor 24 so that this target air amount is obtained.

  A variable valve mechanism (hereinafter referred to as “VEL mechanism”) 26 configured by a multi-node link mechanism that continuously and variably controls the valve lift amount and the operating angle of the intake valve 15, the crankshaft 7, and the intake valve And a variable valve timing mechanism (hereinafter referred to as a “VTC mechanism”) 27 that advances and retards the valve timing of the intake valve 15 by continuously variably controlling the rotational phase difference with the camshaft 25 for use. Since these specific configurations are known from Japanese Patent Laid-Open No. 2003-3872, detailed description thereof is omitted. For example, when the command value is not given to both the VEL mechanism 27 and the VTC mechanism 26, the valve lift of the intake valve 15 has the characteristic shown in FIG. 2A (see the solid line), that is, the characteristic corresponding to the output request. Have a large valve lift and a large operating angle. On the other hand, when a command value is given only to the VEL mechanism 27, both the valve lift amount and the operating angle are reduced without changing the crank angle position at which the valve lift becomes maximum. Further, when the command value is not given to the VTC mechanism 26, the rotation phase is at the most retarded angle position, and when the command value is given only to the VTC mechanism 26, the rotation phase is changed without changing the valve lift amount and the operating angle. Specifically, only the intake valve opening timing IVO (or the intake valve closing timing IVC) moves to the advance side.

  In this embodiment, as will be described later with reference to FIG. 5, the engine is started during a period from timing t0 when the starter switch is turned on to timing t1 when the engine is started (this period is hereinafter referred to as “starting time”). A period from timing t1 to timing t2 (first timing) when the intake valve temperature reaches a temperature higher than the coolant temperature Tw by a certain value (this temperature is hereinafter referred to as "equilibrium temperature") And a period from timing t2 when the intake valve temperature reaches the equilibrium temperature to timing t3 (second timing) when the catalyst 9 is activated (this period is hereinafter referred to as "second period after starting"). ) And a period after the timing t3 when the catalyst 9 is activated (this period is hereinafter referred to as “normal time”). (Lift amount and valve timing) is varied, to which corresponds to operate the two mechanisms 26, 27 as follows. In this embodiment, the normal time is also after completion of warming up of the engine.

  [1] At the time of start-up, command values are given to both the VEL mechanism 26 and the VTC mechanism 27 to operate them, and the command value to the VTC mechanism 27 is decreased. At this time, the valve lift of the intake valve 15 has the characteristics shown in FIG. 2B (see the broken line). That is, the valve timing of the intake valve 15 moves to the retard side with the small lift amount, and the opening timing IVO of the intake valve 15 is substantially the same as the intake top dead center TDC as in the normal time. The closing timing IVC advances substantially to the intake bottom dead center BDC as compared with the normal time.

  [2] In the first period after start-up, command values are given to both the VEL mechanism 26 and the VTC mechanism 27 to operate them, and the command value to the VTC mechanism 27 is increased. At this time, the lift angle and the operating angle of the intake valve 15 are both smaller than normal due to the operation of the VEL mechanism 26, and the crank angle position where the lift amount of the intake valve 15 is maximized by the operation of the VTC mechanism 27 is described above. In the case of 1] or in the case of [3] described later, the valve lift of the intake valve 15 at this time has the characteristics shown in FIG. 2C (see the two-dot chain line). That is, the lift amount is small (for example, 3 to 4 mm), and the overlap amount of the intake / exhaust valves 15 and 16 is increased.

  [3] In the second period after start-up, command values are given to both the VEL mechanism 26 and the VTC mechanism 27 and operated, and the command value to the VTC mechanism 27 is reduced, so that the valve lift of the intake valve 15 at this time is The characteristics shown in FIG. 2B (see the broken line) are obtained. That is, the valve timing of the intake valve 15 moves to the retard side with the small lift amount, and the opening timing IVO of the intake valve 15 is substantially the same as the intake top dead center TDC as in the normal time. The closing timing IVC advances substantially to the intake bottom dead center BDC as compared with the normal time.

  [4] During normal operation, command values are not given to both the VEL mechanism 26 and the VTC mechanism 27, and they are deactivated. At this time, the valve lift of the intake valve 15 has the characteristics shown in FIG. 2A.

  Here, the valve lift of the intake valve 15 in the first period after the start has the characteristics shown in FIG. 2C because the overlap between the intake and exhaust valves 15 and 16 is enlarged immediately after the start as shown by the broken line in FIG. This makes it possible to reduce HC by reducing the wall flow rate in the combustion chamber 5 (the wall flow rate on the upper surface of the combustion chamber 5 and the wall flow rate on the cylinder surface in the combustion chamber 5) from the normal time (large lift) indicated by the solid line. It is. More specifically, immediately after start-up, the amount of residual gas in the combustion chamber 5 is increased by increasing the overlap amount to promote atomization of the fuel with the high-temperature gas, and the unburned HC in the combustion chamber 5 is recycled. This is because the amount of HC discharged from the engine is reduced. On the other hand, since the wall flow rate in the combustion chamber 5 increases after the timing of t2 when the intake valve temperature reaches the equilibrium temperature, the characteristic in FIG. 2C is until the timing of t2.

  Next, the reason why the valve lift of the intake valve 15 is set to the characteristics shown in FIG. 2B in the second period after starting will be described. FIG. 4 shows how the characteristics of FIG. 2A and the characteristics of FIG. 2B differ in HC, exhaust temperature, and combustion stability with respect to the ignition timing. When the valve lift shown in FIG. 4 is changed to the valve lift shown in FIG. 2B and the intake valve closing timing IVC is brought closer to the intake bottom dead center BDC, the effective compression ratio is improved as compared with the valve lift shown in FIG. To do. If the engine is operated at the combustion stability limit in this case, the ignition timing at the combustion stability limit is ADVa when the valve lift of FIG. 2A is used as shown in the third stage of FIG. In the valve lift of 2B, the ignition timing at the combustion stability limit moves to ADVb that is retarded from ADVa. This means that if the operation at the combustion stability limit is continued, the ignition timing can be retarded from ADVa to ADVb by a predetermined value ΔADV when the valve lift in FIG. 2A is changed to the valve lift in FIG. 2B. If the ignition timing can be retarded in this way, the exhaust temperature rises by the ignition timing retardation amount ΔADV (see the first stage in FIG. 4), and the HC at the engine outlet decreases (the second stage in FIG. 4). See eye).

  Thus, the ignition timing can be retarded while ensuring drivability by bringing the intake valve closing timing IVC closer to the intake bottom dead center BDC in the second period after the start, resulting in a reduction in HC and exhaust temperature. Can be raised.

  Furthermore, the characteristic that the valve lift of the intake valve 15 is shown in FIG. 2B at the time of start-up is that the fuel vaporization promoting effect is achieved because the exhaust temperature is low even if the overlap amount is increased at the time of start-up when the boost pressure does not develop. Instead, the lift amount is made smaller than usual to increase the intake flow velocity, and this increased intake flow velocity promotes secondary atomization (fuel atomization by intake air), that is, fuel vaporization. Because. For this reason, the fuel injection is performed in the intake stroke unlike the first period after the start, the second period after the start, and the normal time. For example, fuel injection is performed across the intake valve opening timing. Here, “cross” means that fuel injection is started before the intake valve opening timing and the fuel injection is ended when the intake valve opening timing is over.

  FIG. 5 summarizes the points described above with reference to FIGS. 2 to 4, that is, when the engine is operated while maintaining an idle state from the cold start, the valve lift of the intake valve 15 (lift amount VL, closing timing IVC), fuel injection end timing It is the timing chart which showed how to control TITM and ignition timing ADV as a model.

  Here, control of the valve lift of the intake valve 15, the fuel injection end timing, and the ignition timing is performed in four stages over time as follows.

(1) Period until engine start timing t1 (that is, at the start)
(2) A period from the start timing t1 to the timing t2 when the intake valve temperature reaches the equilibrium temperature (that is, the first period after the start)
(3) A period from timing t2 to timing t3 when the catalyst 9 is activated (that is, a second period after the start)
(4) Period after the second timing t3 (that is, normal time)
In the first period after starting (2) above, the VEL mechanism 26 is operated, and the lift amount VL of the intake valve 15 is set to a target value VL2 that is common to the first and second periods after starting and is reduced (for example, 3 to 4 mm) and the VTC mechanism 27 is operated and the command value given to the VTC mechanism 27 is increased so that the intake valve closing timing IVC is started at a target value IVC2 for the first period after starting (by about 10 ° from a target value IVC1 described later). The amount of overlap between the intake and exhaust valves 15 and 16 is increased by advancing to the angle side. Due to the larger overlap than usual, the high-temperature exhaust gas remaining in the combustion chamber 5 increases, and this high-temperature exhaust gas raises the temperature of the combustion chamber 5, so that the wall flow rate in the combustion chamber 5 decreases (FIG. 3). As a result, HC discharged from the engine can be reduced.

  However, if the overlap amount is increased, the residual gas that does not contribute to combustion increases, so the combustion stability deteriorates. In order to avoid this, the ignition timing ADV is advanced to the target value ADV2 in the first period after starting. This target value ADV2 is the ignition timing at the combustion stability limit in a state where the intake valve 15 is a small lift and the overlap amount is enlarged (a value obtained by advancing the normal ignition timing by the amount of increase in residual gas).

  Even during the second period after the start of the above (3), the VEL mechanism 26 is operated to set the intake valve 15 to a small lift, and the command value given to the VTC mechanism 27 is reduced, and the closing timing IVC of the intake valve 15 is set to the intake bottom dead. The angle is retarded to the target value IVC3 in the second period after the start in the vicinity of the point BDC. This improves the effective compression ratio and improves the combustion stability. If the engine is operated at the combustion stability limit, the ignition timing ADV can be retarded from the normal time by the amount of improvement in the combustion stability. Therefore, the second period after starting the timing when the ignition timing ADV is delayed from the normal target value ADV1. Target value ADV3. As a result, the exhaust temperature rises and the catalyst 9 is activated earlier.

  On the other hand, even if the overlap amount is increased at the start of the above (1), fuel vaporization cannot be promoted. Therefore, the overlap amount is not increased, and fuel injection is performed in the intake stroke, and the secondary by the intake air is performed. Atomize. Further, as in the second period after start-up, the VEL mechanism 26 is operated to set the intake valve 15 to a small lift, and the command value given to the VTC mechanism 27 is reduced, and the closing timing IVC of the intake valve 15 is set to the intake bottom dead. The angle is retarded to the target value IVC3 in the second period after the start in the vicinity of the point BDC.

  When the normal time (4) is reached, both the valve lift of the intake valve 15 and the ignition timing ADV are returned to the target values at the normal time. That is, the VEL mechanism 26 is deactivated and the lift amount VL of the intake valve 15 is returned to the normal target value VL1 (large lift), and the VTC mechanism 27 is deactivated and the intake valve closing timing IVC is set to the normal target value IVC1. The angle is retarded (for example, 50 to 60 ° ABDC). In order to continue the operation at the stability limit, the ignition timing ADV is advanced to the normal ignition timing ADV1.

  This control executed by the engine controller 31 will be described in detail with reference to the flowcharts of FIGS. 6, 7, and 8 are for calculating the intake valve closing timing IVC, the intake valve lift amount VL, the fuel injection end timing TITM, and the ignition timing ADV, and are executed at regular intervals (for example, every 10 ms). .

  In step 1, the signal from the starter switch 36 is observed. If the signal from the starter switch 36 is ON, it is determined that the engine is starting, and the process proceeds to step 2 where the cooling water temperature Tw detected by the water temperature sensor 37 is sampled as the starting water temperature TWINT.

  Steps 3, 4, and 5 are parts for setting initial values for the intake valve closing timing IVC [° BBDC], the intake valve lift amount VL [mm], and the fuel injection end timing TITM [° BTDC]. That is, the starting target value IVC3 as an initial value at the intake valve closing timing IVC (see the second stage in FIG. 5), and the intake valve lift amount VL as an initial value in the first period after starting and in the second period after starting. After the common target value VL2 is entered as the initial target value TITM2 (see the third stage in FIG. 5) as the initial value for the fuel injection end timing TITM, the routine proceeds to step 6.

  On the other hand, when the signal from the starter switch 36 is OFF (after starting), step 2 to step 5 are skipped from step 1, and the process proceeds to step 6.

  In step 6, the engine speed NRPM detected by the crank angle sensor (33, 34) is compared with a predetermined value N1. Here, the predetermined value N1 is a value that determines the engine speed at a time slightly before the boost pressure is fully developed. Specifically, as shown in FIG. 9, a value (variable value) using the starting water temperature TWINT as a parameter is given. That is, the higher the starting water temperature TWINT, the faster the engine speed increases, so the time until the boost pressure develops becomes shorter. Therefore, the predetermined value N1 is set to be smaller as the temperature of the higher water temperature increases. However, in the extremely low water temperature range below the predetermined value a, the amount of air necessary for increasing the engine speed increases as the engine friction increases, so that the predetermined value N1 is set to be smaller at the lower water temperature side.

  If the engine speed NRPM is less than the predetermined value N1, it is determined that the boost pressure is not developed, and the routine proceeds to step 7 where the target value ADV3 for the second period after start is entered at the ignition timing ADV [° BTDC].

  When the engine speed NRPM exceeds the predetermined value N1, it is determined that the boost pressure has developed, and the routine proceeds to steps 8-11, where the intake valve closing timing IVC is set to the previous intake valve closing timing IVCold, and the intake valve lift amount VL is set to the previous time. The injection end timing TITM is moved to the previous injection end timing TITMold, and the ignition timing ADV is moved to the previous ignition timing ADVold to the lift amount Vold.

  In steps 12, 13, and 14, it is determined one by one whether or not the following conditions are satisfied, and when all the conditions are satisfied, any one of steps 15 to 17 in FIG. 7 is not satisfied. Sometimes the process proceeds to steps 31 to 33 in FIG.

  <1> The starting water temperature TWINT is lower than a predetermined value TEMP1.

  <2> The inlet temperature Te1 of the catalyst 9 is lower than a predetermined value Te1H.

  <3> Be in an idle state.

  Here, the predetermined value Te1H of <2> is a lower limit value of the temperature at which the catalyst 9 provided near the exhaust manifold assembly is activated. The predetermined value TEMP1 (for example, about 40 ° C.) of <1> is a value for distinguishing between cold start and hot restart.

  The inlet temperature Te1 of the catalyst 9 is detected by a temperature sensor 37 provided at the inlet of the catalyst. Whether or not it is in an idle state is determined by a signal from the idle switch 38.

  When all of the above conditions <1> to <3> are satisfied, that is, when the catalyst 9 is before being activated at the cold start and the operation condition is in the idle state, the process proceeds to steps 15 to 17 in FIG.

  In the following description, it is assumed that the operating conditions are continuously idle. Actually, the operating condition may return to the idle state again after the operating condition deviates from the idle state before the catalyst 9 is activated. However, if this case is included, the flow becomes complicated, so that FIG. 6, FIG. 7, FIG. Not shown in FIG.

  Steps 15 to 17 are parts for advancing the fuel injection end timing TITM from the starting target value TITM2 to the normal target value TITM1. That is, in step 15, the fuel injection end timing TITM is advanced by a constant value DTITM according to the following equation.

TITM = TITMold + DTITM (1)
However, DTITM; constant value (correction amount per calculation cycle),
In step 31, the fuel injection end timing TITM after this advance is compared with the normal target value TITM1, and if the fuel injection end timing TITM after this advance is less than or equal to the normal target value TITM1 (is on the retard side), step 31 is performed. Skip 17 and go to step 18. If the step 15 is repeated from the next time, the fuel injection end timing TITM eventually becomes larger than the normal target value TITM1 (beyond the target value and becomes an advance side), that is, the advance angle is excessively advanced. Then, the routine proceeds to step 17 where the fuel injection end timing TITM is limited to the normal target value TITM1, and then the routine proceeds to step 18. Here, the fuel injection is the intake stroke injection at the start, whereas the exhaust stroke injection is performed in the first period after the start.

  In step 18, the difference (Tw−TWINT) between the current cooling water temperature Tw and the starting water temperature TWINT is compared with a predetermined value DTW. Here, the predetermined value DTW is a value that determines the difference between the cooling water temperature and the starting water temperature when the temperature of the intake valve 15 reaches the equilibrium temperature. Specifically, as shown in FIG. 10, the starting water temperature TWINT is used as a parameter, and a value (variable value) that increases as the starting water temperature TWINT decreases is given. This is because the lower the starting water temperature TWINT, the later the intake valve 15 temperature reaches the equilibrium temperature.

  When the difference (Tw−TWINT) is less than the predetermined value DTW (before the intake valve temperature rises), the routine proceeds to steps 19 to 24.

  First, Steps 19 to 21 are parts for advancing the intake valve closing timing IVC to the first period target value IVC2 after starting. That is, in step 19, the intake valve closing timing IVC is advanced by a constant value DIVC by the following equation.

IVC = IVCold + DIVC (2)
However, DIVC; constant value (correction amount per calculation cycle),
In step 23, the intake valve closing timing IVC after advance is compared with the first period target value IVC2 after starting, and when the intake valve closing timing IVC is less than or equal to the first period target value IVC2 (on the retard side) after starting. Skip step 21 and go to step 22. If step 19 is repeated from the next time, the intake valve closing timing IVC eventually becomes greater than the target value IVC2 for the first period after starting (becomes the advance side beyond the target value), that is, the advance angle is excessive. The process proceeds from step 20 to step 21 to limit the intake valve closing timing IVC to the target value IVC2 for the first period after starting, and then proceeds to step 22.

  Steps 22 to 24 are parts for advancing the ignition timing from the starting target value ADV3 to the first period target value ADV2 after starting. That is, at step 22, the ignition timing ADV is advanced by a constant value DADV by the following equation.

ADV = ADVold + DADV (3)
However, DADV; constant value (correction amount per calculation cycle),
In step 23, the ignition timing ADV is compared with the first period target value ADV2 after starting. Here, as the first period target value ADV2 after starting, the ignition of the combustion stability limit in a state where the intake valve 15 is made a small lift and the intake valve timing is advanced and the valve overlap of the intake and exhaust valves 15 and 16 is expanded. What is necessary is just to set by the map value which uses cooling water temperature Tw and engine rotational speed as a parameter at time, for example. When the ignition timing ADV is less than or equal to the first period target value ADV2 (on the retard side) after starting, step 24 is skipped and the current process is terminated. If the step 22 is repeated from the next time, the ignition timing ADV eventually becomes larger than the first period target value ADV2 after starting (becomes the target value beyond the target value), that is, the advance angle is excessive. Then, the routine proceeds to step 24, where the ignition timing ADV is limited to the first period target value ADV2 after starting, and then the current process is terminated.

  Thus, when a predetermined time has elapsed after the boost pressure has developed, the fuel injection end timing TITM is set to the normal target value TITM1 that defines the exhaust stroke injection as shown in the first period after the start in FIG. The valve closing timing IVC is held at the target value IVC2 for the first period after starting, and the ignition timing ADV is held at the target value ADV2 for the first period after starting.

  On the other hand, before the boost pressure develops, as shown in the start period in FIG. 5, the fuel injection end timing TITM is set to the start target value TITM2 that determines the intake stroke injection, and the intake valve close timing IVC is set to the start time target. The ignition timing ADV is held at the starting target value ADV3 at the value IVC3.

  On the other hand, when the difference (Tw−TWINT) becomes equal to or greater than the predetermined value DTW, it is determined that the intake valve temperature has risen to the equilibrium temperature, and the process proceeds from step 18 to steps 25-30.

  First, steps 25 to 27 are parts for retarding the intake valve closing timing IVC from the target value IVC2 in the first period after starting to the target value IVC3 (near the intake bottom dead center BDC) in the second period after starting. That is, at step 25, the intake valve closing timing IVC is retarded by a constant value DIVC by the following equation.

IVC = IVCold−DIVC (4)
However, DIVC; constant value (correction amount per calculation cycle),
In step 26, the intake valve closing timing IVC after the retard is compared with the second period target value IVC3 after starting, and when the intake valve closing timing IVC is equal to or greater than the second period target value IVC3 after starting (is on the advance side). Skip step 27 and go to step 28. If step 25 is repeated from the next time, the intake valve closing timing IVC will eventually become smaller than the second period target value IVC3 after starting (beyond the target value and will be retarded), that is, it will be too retarded. The process proceeds from step 26 to step 27 to limit the intake valve closing timing IVC to the second period target value IVC3 after starting, and then proceeds to step 28.

  Next, steps 28 to 30 are parts for retarding the ignition timing ADV from the first period target value ADV2 after starting to the second period target value ADV3 after starting. That is, at step 28, the ignition timing ADV is retarded by a constant value DADV by the following equation.

ADV = ADVold−DADV (5)
However, DADV; constant value (correction amount per calculation cycle),
In step 29, the ignition timing ADV is compared with the second period target value ADV3 after starting. Here, the target value ADV3 is an ignition timing at the combustion stability limit in a state where the intake valve 15 is a small lift and the intake valve closing timing IVC is in the vicinity of the intake bottom dead center BDC. What is necessary is just to set with the map value which uses the cooling water temperature Tw and engine rotational speed as a parameter. When the ignition timing ADV is greater than or equal to the second period target value ADV3 (on the advance side) after starting, step 30 is skipped and the current process is terminated. If the step 28 is repeated from the next time, the ignition timing ADV eventually becomes smaller than the second period target value ADV3 after starting (becomes the retarded side exceeding the target value), that is, the retarded angle is excessively retarded. Then, the routine proceeds to step 30 where the ignition timing ADV is limited to the second period target value ADV3 after starting, and then the current process is terminated.

  Thus, when the predetermined time has elapsed after the intake valve temperature has risen to the equilibrium temperature, the fuel injection end timing TITM is the normal target value that determines the exhaust stroke injection as shown in the first period after the start in FIG. In TITM1, the intake valve closing timing IVC is held at the second period target value IVC3 after starting, and the ignition timing ADV is held at the second period target value ADV3 after starting.

  This holding state continues until the catalyst inlet temperature Te1 reaches a predetermined value Te1H. When the catalyst inlet temperature Te1 becomes equal to or higher than the predetermined value Te1H, it is determined that the catalyst 9 has been activated, and from step 13 in FIG. Proceed to steps 31-39.

  First, steps 31 to 33 in FIG. 8 are parts for retarding the intake valve closing timing IVC from the second period target value IVC3 after the start to the normal target value IVC1 (50 to 60 ° after the intake bottom dead center). That is, in step 31, the intake valve closing timing IVC is retarded by a constant value DIVC according to the following equation.

IVC = IVCold−DIVC (6)
However, DIVC; constant value (correction amount per calculation cycle),
In step 32, the intake valve closing timing IVC is compared with the normal target value IVC1, and when the intake valve closing timing IVC is greater than or equal to the normal target value IVC1 (on the advance side), step 33 is skipped and the routine proceeds to step 34. If the step 31 is repeated from the next time, the intake valve closing timing IVC eventually becomes smaller than the normal target value IVC1 (becomes the retarded side exceeding the target value), that is, the retard is excessively retarded. After proceeding to step 34 and restricting the intake valve closing timing IVC to the normal target value IVC1, the routine proceeds to step 34.

  Next, steps 34 to 36 are parts for switching the lift amount VL of the intake valve 15 from the target value VL2 (small lift) to the target value VL1 (large lift) at the normal time. That is, in step 34, the lift amount VL is increased by a constant value DVL by the following equation.

VL = Vold + DVL (7)
However, DVL; constant value (correction amount per calculation cycle),
In step 35, the lift amount VL is compared with the normal target value VL1, and when the lift amount VL is less than or equal to the normal target value VL1, step 36 is skipped and the routine proceeds to step 37. If the step 34 is repeated from the next time, the lift amount VL eventually becomes larger than the normal target value VL1. At this time, the routine proceeds from step 35 to step 36, restricts the lift amount VL to the normal target value VL1, and then proceeds to step 37. .

  Steps 37 to 39 are parts for advancing the ignition timing ADV from the second period target value ADV3 to the normal target value ADV1 after starting. That is, in step 37, the ignition timing ADV is advanced by a constant value DADV by the following equation.

ADV = ADVold + DADV (7)
However, DADV; constant value (correction amount per calculation cycle),
In step 38, the ignition timing ADV is compared with the normal target value ADV1. Here, the target value ADV1 is an ignition timing at a combustion stability limit in a state where the intake valve 15 is in a normal state, that is, a large lift and an intake valve closing timing IVC is 50 to 60 °. Similarly to the target values ADV2 and ADV3, for example, a map value with the cooling water temperature Tw and the engine rotation speed as parameters may be set. When the ignition timing ADV is less than or equal to the normal target value ADV1 (on the retard side), step 39 is skipped and the current process is terminated. If the step 37 is repeated from the next time, the ignition timing ADV eventually becomes larger than the target value ADV1 at the normal time (becomes the target value ADV1), that is, the advance angle is excessive. After proceeding to and limiting the ignition timing ADV to the normal target value AD13, the current process is terminated.

  In this way, when a predetermined time has elapsed after the activation of the catalyst 9, the fuel injection end timing TITM is set to the normal target value TITM1 that defines the exhaust stroke injection as shown in the normal period in FIG. The valve closing timing IVC is held at the normal target value IVC1, and the ignition timing ADV is held at the normal target value ADV1.

  In a flow (not shown), the operation and non-operation of the VTC mechanism 27 and the command value to the VTC mechanism 27 are controlled according to the intake valve closing timing IVC calculated in this way (the intake valve closing timing IVC is the target value IVC3 at the start time). The VTC mechanism 27 is activated and the command value to the VTC mechanism 27 is decreased when the engine is in the range, and the VTC mechanism 27 is activated and the command value is increased when the target value IVC2 is in the first period after the start. When the two-period target value IVC3 is reached, the command value to the VTC mechanism 27 is decreased again, whereas when the intake valve closing timing IVC is at the normal target value IVC1, the VTC mechanism 27 is deactivated. After the first period target value IVC2, after the start the second period target value IVC3, when switching to the normal target value IVC1, the VTC mechanism 27 Decree value is variably controlled.).

  Further, the operation and non-operation of the VEL mechanism 26 are controlled according to the 15 lift amount VL calculated in this way (when the lift amount VL of the intake valve 15 is started, the first period after start, the second period after start) The VEL mechanism 26 is activated when the target value VL2 is equal to the target value VL2, while the VEL mechanism 26 is deactivated when the lift amount VL of the intake valve 15 is equal to the normal target value VL1. When switching to VL1, the command value to the VEL mechanism 26 is variably controlled.)

  Further, spark ignition is performed by the spark plug 14 using the ignition timing ADV calculated in this way.

  Here, the operation of the present embodiment will be described.

  According to the present embodiment (the invention described in claim 1), the overlap amount of the intake and exhaust valves 15 and 16 is increased in the first period after the engine is started by using the VEL mechanism 26 and the VTC mechanism 27. As a result, the high temperature exhaust gas remaining in the combustion chamber 5 increases and the atomization of the fuel is promoted, and the unburned HC in the combustion chamber 5 is reburned. The amount of HC discharged from the engine in the first period after starting can be reduced.

  Further, even if the overlap amount of the intake / exhaust valves 15 and 16 is increased at the start before the boost pressure is developed, the effect of promoting vaporization by blowing back cannot be obtained, so this embodiment (the invention according to claim 1) According to the above, intake stroke injection is performed at the start (for example, injection is performed across the intake valve opening timing), thereby promoting secondary atomization by intake air.

  As a result, as shown in the upper part of FIG. 3, the overlap amount of the intake and exhaust valves 15 and 16 is increased even at the start before the boost pressure develops (see the broken line in the upper part of FIG. 3). The HC emission amount at the engine outlet can be reduced by the area indicated by hatching (see the one-dot chain line in the upper part of FIG. 3).

  According to the present embodiment (the invention described in claim 7), the closing timing IVC of the intake valve 15 is brought to the target value IVC3 in the vicinity of the intake bottom dead center BDC at the first timing t2 after the start in FIG. (See the valve lift in FIG. 2B), the effective compression ratio is improved and the combustion stability is increased. At this time, since the operation is performed at the combustion stability limit, the ignition timing can be retarded from the normal time by the increase in the combustion stability (see the lowermost stage in FIG. 5). Can be obtained.

  FIG. 11 is a characteristic diagram of the valve lift of the intake / exhaust valve according to the second embodiment. In the first embodiment, as shown in FIG. 2, the valve lift characteristics of the intake valve are as follows: B characteristics at start-up, C characteristics during the first period after start, B characteristics during the second period after start-up, In the second embodiment, the valve lift characteristics of the intake valve in FIG. 11 are the characteristics of A indicated by a solid line at the start, the characteristics of D indicated by a two-dot chain line in the first period after the start in FIG. In the second period, the characteristic B is indicated by a broken line, and the characteristic A is indicated by a solid line at normal times. That is, the second embodiment is different from the first embodiment in the following points.

  Difference 1; The first embodiment is a small lift at start-up when the boost pressure does not develop, whereas the second embodiment is a large lift that is the same as a normal lift.

  Difference 2: The first embodiment is a small lift in the first period after the start to increase the overlap amount, whereas the second embodiment is the same large lift as that in the normal state. It has been experimentally confirmed that the effect of increasing the valve overlap amount can be obtained as a large lift.

  If the intake valve 15 is set to a small lift at the start before the boost pressure develops, the wall flow rate in the combustion chamber 5 increases on the condition that the wall flow rate of the intake valve 15 is large. According to the invention described in (2), at the start before the boost pressure develops, the lift is not a small lift, that is, the lift is the same as the normal lift, so that the wall flow rate in the combustion chamber 5 can be increased at the start. Absent.

  Further, according to the second embodiment, the valve lift of the intake valve changes from A to D in FIG. 11 from the start to the first period after the start, that is, remains as a large lift. During this time, the VEL mechanism It is not necessary to operate 26.

  In the embodiment, the case where it is determined based on the engine speed NRPM whether or not the engine is started before the boost pressure is developed has been described. However, the basic injection pulse width Tp as the engine load equivalent amount and a predetermined value Tp1 ( Based on the comparison with the fifth stage of FIG. 5), it may be determined whether or not the engine is at the start-up before the boost pressure develops.

  In the embodiment, the L-Jetronic gasoline injection engine has been described, but the present invention can also be applied to a D-Jetronic gasoline injection engine.

  The function of the control means described in claim 1 is performed by steps 1 and 5 in FIG. 6 and steps 19 to 24 in FIG.

1 is a schematic configuration diagram of a first embodiment of the present invention. The characteristic figure of the valve lift of an intake / exhaust valve. FIG. 6 is a waveform diagram showing changes in the HC amount and the combustion chamber wall flow rate when the intake valve is made a small lift and the overlap amount of the intake and exhaust valves is enlarged immediately after the start. Explanatory drawing of the exhaust_gas | exhaustion reduction effect by setting the intake valve closing timing IVC to the intake bottom dead center vicinity. Timing chart from start. The flowchart for demonstrating the calculation of the lift amount of an intake valve, intake valve closing timing, and ignition timing. The flowchart for demonstrating the calculation of the lift amount of an intake valve, intake valve closing timing, and ignition timing. The flowchart for demonstrating the calculation of the lift amount of an intake valve, intake valve closing timing, and ignition timing. The characteristic diagram of the predetermined value N1. The characteristic diagram of predetermined value DTW. The characteristic figure of the valve lift of the intake and exhaust valve of a 2nd embodiment.

Explanation of symbols

14 Spark plug (ignition device)
15 Intake valve 26 VEL mechanism (variable valve mechanism)
27 VTC mechanism (Variable valve mechanism)
31 Engine controller (control means)
36 Starter switch

Claims (8)

An intake valve that opens and closes the intake port;
A variable valve mechanism capable of variably controlling the valve lift amount and valve timing of the intake valve;
An ignition device that performs spark ignition in the combustion chamber;
A fuel injection device that injects fuel from the intake port toward the intake valve;
The fuel injection device is controlled so that fuel injection is performed in the intake stroke at the start before the intake pipe pressure reaches a predetermined negative pressure, and the intake valve after the start at which the intake pipe pressure reaches a predetermined negative pressure The variable valve mechanism is ignited at the combustion stability limit, which is the retarded ignition timing at which the engine can be combusted in a stable state so that the overlap amount of the exhaust valve increases after the engine warm-up is completed. An engine control device comprising: control means for controlling each of the ignition devices to be performed.   The variable valve mechanism is controlled so that the intake valve is operated with the same large lift characteristic as that in a normal state at the start before the intake pipe pressure reaches a predetermined negative pressure. The engine control device according to claim 1.   The variable valve mechanism is controlled so that the intake valve operates at a lift amount characteristic smaller than a normal lift amount at the start-up before the intake pipe pressure reaches a predetermined negative pressure. The engine control device according to claim 1.   2. The variable valve mechanism according to claim 1, further comprising: controlling the variable valve mechanism so that the intake valve operates with a predetermined small lift characteristic after the start of the intake pipe pressure reaching a predetermined negative pressure. 3. Engine control device.   2. The engine control device according to claim 1, wherein whether or not the intake pipe pressure is a start time before reaching a predetermined negative pressure is determined based on an engine speed. 3.   2. The engine control device according to claim 1, wherein it is determined based on a fuel injection amount whether or not the intake pipe pressure is a start time before reaching a predetermined negative pressure. 3.   The variable valve mechanism is ignited at the combustion stability limit so that the intake valve operates with a predetermined small lift characteristic at the first timing after starting and the closing timing of the intake valve is close to the intake bottom dead center. The engine control device according to claim 1, wherein each of the ignition devices is controlled such that the ignition is performed.   8. The engine control apparatus according to claim 7, wherein the first timing is a timing at which the intake valve reaches an equilibrium temperature that is higher by a predetermined value than a coolant temperature.

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