JP3979376B2 - 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 at start-up.

A variable valve mechanism that continuously and variably controls the valve lift amount and the operating angle of the intake valve 15 and a variable valve mechanism of the intake valve 15 by continuously variably controlling the rotational phase difference between the crankshaft 7 and the intake valve camshaft 25. Variable valve timing mechanism for advancing / retarding the timing, the intake valve lift amount is set to be low (small) by this variable valve mechanism from the start to the first idling, the valve timing is delayed by the variable valve timing mechanism, and the fuel Some have the injection timing during the intake stroke (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.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an apparatus for reducing HC by reducing the wall flow rate in the combustion chamber even in a condition where the intake valve is in a small lift state and the wall flow rate of the intake valve is high.

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, And a fuel injection device (21) for injecting fuel from the intake port (4) toward the intake valve (15). When the engine controller (31) starts the engine, the intake valve (15) Is operated with a predetermined small lift characteristic, and the variable valve mechanism (26, 27) is combusted so that the amount of overlap between the intake valve (15) and the exhaust valve (16) increases after the engine is warmed up. The ignition timing of the ignition device (14) is controlled to be more advanced than the ignition timing after completion of warming up of the engine so that ignition is performed at the stability limit.

  According to the present invention, when starting the engine, the intake valve is operated with a predetermined small lift characteristic as shown by a two-dot chain line in FIG. 2 and the overlap amount of the intake and exhaust valves is increased. High-temperature exhaust gas remaining in the combustion chamber is increased, fuel atomization is promoted, and unburned HC is reburned, whereby the amount of HC discharged from the engine can be reduced.

  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 intake air to form an air-fuel mixture. 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 timing t2 (the temperature at which the intake valve temperature reaches a temperature higher than the cooling water temperature Tw by a certain value from the timing t1 when the engine is started (hereinafter referred to as “equilibrium temperature”). A period until the first timing) (this period is hereinafter referred to as "first period after start"), and a timing t3 (second timing) at which the catalyst 9 is activated from a timing t2 when the intake valve temperature reaches the equilibrium temperature. Of the intake valve 15 in the period up to (this period is hereinafter referred to as “second period after start”) and the period after the timing t3 when the catalyst 9 is activated (this period is hereinafter referred to as “normal time”). The lifts (lift amount and valve timing) are made different, and the two mechanisms 26 and 27 are operated as follows in response to the lifts. In this embodiment, the normal time is also after completion of warming up of the engine.

  [1] In the first period after starting, command values are given to both the VEL mechanism 26 and the VTC mechanism 27 to operate them. As the VEL mechanism 26 is operated, the lift amount and the operating angle of the intake valve 15 are both smaller than normal, and the crank angle position where the lift amount of the intake valve 15 is maximum is moved to the advance side by the operation of the VTC mechanism 27. 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.

  [2] In the second period after starting, the command value is given to both the VEL mechanism 26 and the VTC mechanism 27 to operate, but the command value to the VTC mechanism 27 is reduced, so 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.

  [3] 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 increases by the ignition timing retardation amount ΔADV (see the second stage in FIG. 4), and HC at the engine outlet decreases ( first 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.

  FIG. 5 summarizes what has been described above with reference to FIGS. 2 to 4, that is, the valve lift (lift amount, closing timing IVC) and ignition timing ADV of the intake valve 15 when operating while maintaining an idle state from cold start. It is the timing chart which showed how to control like a model.

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

(1) 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)
(2) Period from timing t2 to timing t3 when the catalyst 9 is activated (that is, the second period after the start)
(3) Period after the second timing t3 (that is, normal time)
In the first period after the start of (1) above, the VEL mechanism 26 is operated, and the lift amount VL of the intake valve 15 is set to a target value VL2 common to the first and second periods after the start and is reduced (for example, 3 to 4 mm), and the VTC mechanism 27 is operated to advance the intake valve closing timing IVC to a target value IVC2 (about 10 ° advance side from a target value IVC1 to be described later) in the first period after starting the intake / exhaust valve 15 , 16 overlap amount is enlarged. 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 (2), 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.

  When the normal time (3) is reached, both the valve lift of the intake valve 15 and the ignition timing ADV are returned to the normal target values. 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.

  In FIG. 5, the period from the timing t0 when the starter switch 36 is switched from OFF to ON to start the engine (starting period) from the timing t1 to the starting timing t1 is the same as the first period after starting (1). The mechanism 26 and the VTC mechanism 27 are operated. This is because even if the VEL mechanism 26 and the VTC mechanism 27 are immediately operated at the start timing t1, a delay in the operation of the VEL mechanism 26 and the VTC mechanism 27 cannot be avoided. Therefore, the lift of the intake valve 15 is previously performed before the start timing t1. This is because the amount of overlap between the intake and exhaust valves 15 and 16 is increased by setting the amount VL small and advancing the intake valve closing timing IVC.

  The ignition timing in the starting period is an ignition timing CRADV adapted to the starting, and basically uses the cranking rotation speed of the engine as a parameter, and therefore changes according to the cranking rotation speed.

This control executed by the engine controller 31 will be described in detail according to the flowchart of FIG. FIG. 6 is for calculating the intake valve closing timing IVC [° ABDC], the valve lift VL, and the ignition timing ADV [° BTDC], and is executed at regular intervals (for example, every 10 ms).

  However, in the following description, it is assumed that the operating conditions are continuously in an idle state.

  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.

  In Step 3, the intake valve closing timing IVC is moved to the previous intake valve closing timing IVCold, and the valve lift amount VL is moved to the previous valve lift amount Vold.

  Here, the initial values of the intake valve closing timing IVC and the valve lift amount VL are the first period target value IVC2 after starting of the intake valve closing timing and the first period target value after starting which is a small lift amount as shown in FIG. VL2 (see the second and fourth stages in FIG. 5).

  On the other hand, when the signal from the starter switch 36 is OFF (after starting), step 2 is skipped from step 1 and the operation of step 3 is executed.

  In steps 4, 5, and 6, it is determined one by one whether or not the following conditions are satisfied, and when all the conditions are satisfied, step 7 is performed, and when any one of the conditions is not satisfied, steps 15 to 23 are performed. Proceed to

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

  When the above conditions <1> to <3> are all met, that is, when the catalyst 9 is before activation at the cold start and the operation condition is in the idle state, the routine proceeds to step 7.

  In step 7, 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. More specifically, as shown in FIG. 7, 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 step 8 where the target value ADV2 for the first period after start is set as the ignition timing ADV. The target value ADV2 is the ignition timing 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 to increase the valve overlap of the intake and exhaust valves 15 and 16, for example, the cooling water temperature Tw Or a map value with the engine speed as a parameter.

  Repeat steps 3-8 from the next time. Eventually, 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 7 to steps 9 to 14.

  Steps 9 to 11 are parts for retarding the intake valve closing timing IVC from the target value IVC2 in the first period after startup to the target value IVC3 (in the vicinity of the intake bottom dead center BDC) in the second period after startup. That is, in step 9, the intake valve closing timing IVC is retarded by a constant value DIVC according to the following equation.

IVC = IVCold + DIVC (1)
However, DIVC; constant value (correction amount per calculation cycle),
In step 10, 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 greater than the second period target value IVC3 after starting (it is on the retarding side). Proceeding to step 11, the intake valve closing timing IVC is limited to the second period target value IVC3 after starting, whereas the intake valve closing timing IVC is less than or equal to the second period target value IVC3 (starting side) after starting. Sometimes step 12 is skipped.

  Steps 12 to 14 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, in step 12, the ignition timing ADV is retarded by a constant value DADV by the following equation.

ADV = ADVold−DADV (2)
However, DADV; constant value (correction amount per calculation cycle),
In step 13, 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 smaller than the target value ADV3 (on the retard side), the routine proceeds to step 14 where the ignition timing ADV is limited to the target value ADV3, while the ignition timing ADV is greater than the target value ADV3 (advance angle). Step 14 is skipped.

  Since the operations of Steps 7 and 9 to 14 are repeated from the next time, the closing timing IVC of the intake valve is retarded by a certain value DIVC from the first period target value IVC2 after starting, and eventually the second period target value IVC3 after starting. After that, it is held at the target value IVC3 for the second period after starting. Note that the lift amount VL of the intake valve 15 remains at the initial value, that is, the small lift amount VL2 by the operation in step 3. Further, the ignition timing ADV is retarded from the first period target value ADV2 by a constant value DADV, and eventually coincides with the second period target value ADV3 after starting, and thereafter is held at the second period target value ADV3 after starting. The

  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 is activated, and the process proceeds from step 5 to steps 15 to 23. .

  Steps 15 to 17 are parts for switching the valve lift amount VL of the intake valve 15 from the target value VL2 (small lift) to the normal target value VL1 (large lift). That is, in step 15, the valve lift amount VL is increased by a constant value DVL by the following equation.

VL = Vold + DVL (3)
However, DVL; constant value (correction amount per calculation cycle),
In step 16, the valve lift amount VL is compared with the normal target value VL1, and when the valve lift amount VL is larger than the normal target value VL1, the process proceeds to step 17 to limit the valve lift amount VL to the normal target value VL1. On the other hand, when the valve lift amount VL is less than or equal to the normal target value VL1, step 17 is skipped.

  Steps 18 to 20 are parts for retarding the intake valve closing timing IVC from the second period target value IVC3 after starting to the normal target value IVC1 (50 to 60 ° after intake bottom dead center). That is, in step 18, the intake valve closing timing IVC is retarded by a constant value DIVC according to the following equation.

IVC = IVCold + DIVC (4)
However, DIVC; constant value (correction amount per calculation cycle),
In step 19, the intake valve closing timing IVC is compared with the normal target value IVC1, and when the intake valve closing timing IVC is larger than the normal target value IVC2 (on the retard side), the routine proceeds to step 20 and the intake valve closing timing IVC. Is limited to the normal target value IVC1, and when the intake valve closing timing IVC is less than or equal to the normal target value IVC1 (on the advance side), step 20 is skipped.

  Steps 21 to 23 are parts for advancing the ignition timing ADV to the normal target value ADV1. That is, in step 21, the ignition timing ADV is advanced by a constant value DADV by the following equation.

ADV = ADVold + DADV (5)
However, DADV; constant value (correction amount per calculation cycle),
In step 22, 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 larger than the normal target value ADV1 (at the advance side), the routine proceeds to step 23, where the ignition timing ADV is limited to the normal target value ADV1, and the ignition timing ADV is compared with the normal target value ADV3. Step 23 is skipped at the following time (on the retard side).

  From the next time, steps 5 and 15 to 23 are repeated. Among these, in steps 15 to 17, the valve lift amount VL of the intake valve 15 is increased by the constant value DVL, and eventually coincides with the normal target value VL1, and thereafter is maintained at the normal target value VL1 (FIG. 4 fourth). (See the steps). In steps 18 to 20, the intake valve closing timing IVC is retarded by a constant value DIVC from the second period target value IVC3 after starting, and eventually coincides with the normal target value IVC1, and thereafter is maintained at the normal target value IVC1. (See FIG. 5, second row). In steps 21 to 23, the ignition timing ADV is advanced by a constant value DADV, and eventually coincides with the normal target value ADV1, and thereafter is held at the normal target value ADV1 (see the third stage in FIG. 5).

  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 manner (the intake valve closing timing IVC is the first period after the start. When the target value IVC2 is reached, the VTC mechanism 27 is activated and the command value is increased. When the target value IVC3 is reached after the start, the command value to the VTC mechanism 27 is decreased. On the other hand, the intake valve closing timing IVC is The VTC mechanism 27 is deactivated when the target value IVC1 is at the normal time, and the command value to the VTC mechanism 27 is variably controlled at the time of switching to the target value IVC3 for the second period after startup and the target value IVC1 at the normal time. .)

  Further, the operation or non-operation of the VEL mechanism 26 is controlled according to the 15 lift amount VL calculated in this way (the lift amount VL of the intake valve 15 is a target value for the first period after the start and the second period after the start. The VEL mechanism 26 is actuated when it is at VL2, while the VEL mechanism 26 is deactivated when the lift amount VL of the intake valve 15 is at the normal target value VL1, and also to the normal target value VL1. At the time of switching, 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 intake valve 15 is operated with the characteristics of a small lift when the engine is started using the VEL mechanism 26 and the VTC mechanism 27, and the intake / exhaust valves 15, 16 are operated. Since the overlap amount is increased (see the valve lift in FIG. 2C), the high-temperature exhaust gas remaining in the combustion chamber 5 increases to promote fuel atomization and unburned HC in the combustion chamber 5 Is reburned, and the amount of HC discharged from the engine can be reduced.

  According to the present embodiment (the invention described in claim 2), in FIG. 5, at the first timing t2 after the start, the closing timing IVC of the intake valve 15 reaches the target value IVC3 that is in the vicinity of the intake bottom dead center BDC. (Steps 7 and 9 to 11 in FIG. 6, refer to 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 steps 12 to 14 in FIG. 6 and the third stage in FIG. 5). Each effect of HC reduction and exhaust temperature rise can be obtained.

  If the intake valve 15 is operated with a small lift characteristic even when the time has elapsed since the start, the fuel consumption deteriorates due to an increase in pumping loss. This embodiment (the invention according to claim 5) ), The intake valve 15 is operated with a large lift characteristic at a second timing t3 later than the first timing t2 in FIG. 5, and the closing timing of the intake valve 15 is set to a position past the intake bottom dead center (for example, 50 to 60 ° ABDC) (see steps 5 and 15 to 20 in FIG. 6 and the valve lift in FIG. 2A), the deterioration of fuel consumption can be suppressed.

  According to this embodiment (the invention described in claim 6), since the second timing t3 is a timing at which the catalyst 9 is activated, further exhaust performance can be ensured.

  According to the present embodiment, 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 (the invention according to claim 7), so not only the difference in operating conditions from the start. Further, the difference in the temperature rise characteristics (heat capacity, etc.) of the catalyst 9 can be reflected in the switching timing, so that the deterioration of fuel consumption can be further suppressed and the HC can be reduced.

  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 the engine controller 31 of 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 characteristic diagram of predetermined value DTW.

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;
Combustion stabilization of the variable valve mechanism so that when the engine is started, the intake valve operates with a predetermined small lift characteristic, and the amount of overlap between the intake valve and the exhaust valve increases after the engine is warmed up. A control device for an engine, comprising: control means for controlling the ignition timing of the ignition device to be more advanced than the ignition timing after completion of warm-up of the engine so that ignition is performed at a limit.   The variable valve mechanism is maintained in a combustion stable state so that the intake valve continues to operate with the characteristics of the small lift 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 so that ignition is performed at a limit.   The engine control device according to claim 2, wherein the first timing is a timing at which the intake valve reaches an equilibrium temperature higher than a coolant temperature by a predetermined value.   The engine control device according to claim 3, wherein the timing at which the intake valve reaches the equilibrium temperature is when a value obtained by subtracting a starting water temperature from a cooling water temperature is equal to or greater than a predetermined value.   The variable valve mechanism so that the intake valve operates at a predetermined large lift characteristic at a second timing later than the first timing, and the closing timing of the intake valve is at a position past the intake bottom dead center. The engine control device according to claim 2, wherein each of the ignition devices is controlled so that ignition is performed at a combustion stability limit.   6. The engine control device according to claim 5, further comprising a catalyst for purifying harmful components in the exhaust gas, wherein the second timing is a timing at which the catalyst is activated.   The engine control device according to claim 6, wherein the catalyst is activated when the temperature of the catalyst becomes equal to or higher than a predetermined value.   The engine control apparatus according to claim 6, wherein the second timing and after is after completion of warming up of the engine.

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