JP5195353B2 - Fuel injection control device at engine start - Google Patents

Description

The present invention relates to a start-up fuel injection control device for an engine (internal combustion engine), and more particularly to an in-cylinder direct injection engine.
About.

A fuel injection valve that directly injects a fuel amount corresponding to the valve opening pulse width and the fuel pressure into the combustion chamber, and when the engine starts with a large fluctuation range of the engine rotation speed, In addition, there is a technique in which a deviation in fuel injection timing caused by a difference from an engine speed when fuel injection is actually performed is corrected, and a fuel injection timing is also corrected by actual fuel pressure (see Patent Document 1). .
JP 2002-38993 A

  By the way, in order to reduce the HC at the start of the engine, it is necessary to perform fuel injection so that the target air-fuel ratio at the start can be obtained.

  However, due to variations in the cylinder air amount due to manufacturing errors, the differential pressure between the actual fuel pressure and the cylinder pressure at the fuel injection timing varies, and the fuel injection amount from the fuel injection valve varies. As a result, since the actual air-fuel ratio at the time of starting deviates from the target air-fuel ratio, there is a limit in reducing HC at the time of engine starting. Even if the fuel injection timing is corrected by the actual fuel pressure as in the technique of Patent Document 1, it is not possible to avoid the variation in the fuel injection amount due to the variation in the in-cylinder pressure at the fuel injection timing due to the manufacturing error.

  Accordingly, an object of the present invention is to provide an apparatus that can obtain a target air-fuel ratio at the start even when there is a variation in in-cylinder pressure at the fuel injection timing due to manufacturing errors.

The present invention relates to a fuel injection valve that directly injects a fuel amount corresponding to a valve opening pulse width and a fuel pressure into a combustion chamber, and a start time fuel injection pulse width that is calculated so that a target air-fuel ratio is obtained at the time of start. The fuel injection pulse width calculation means for starting, the fuel injection timing setting means for starting to set the fuel injection timing for starting, the signal for the fuel injection timing for starting and the fuel injection pulse width to be calculated to be set An engine start time fuel injection control device comprising a signal output means for outputting to a fuel injection valve, comprising: an intake pressure detection means for detecting an intake pressure; and a fuel pressure detection means for detecting the fuel pressure; predicts the cylinder pressure at the intake valve closing timing from the intake pressure detected by the detecting means, the calculation based on the differential pressure between the actual fuel pressure and the predicted in-cylinder pressure detected by the fuel pressure detecting means during startup Is corrected at least one of the fuel injection timing starts to be the a start timing fuel injection pulse width setting that is provided with a crank angle sensor, the cylinder pressure prediction means, centered on the intake valve closing timing A predetermined crank angle range is equally divided into a plurality of parts, and the actual crank angle detected by the crank angle sensor at the time of starting is detected by the intake pressure detecting means at a timing coincident with each of the crank angles equally divided into the plurality of parts. The intake air pressure is sampled, and the minimum data among the sampled sampling data is predicted as the in-cylinder pressure at the intake valve closing timing .

In a direct injection engine, even if the fuel injection pulse at the start is the same, the fuel injection amount at the start varies due to the difference in the differential pressure between the actual fuel pressure and the in-cylinder pressure at the fuel injection timing due to manufacturing errors. However, according to the present invention, the fuel injection valve that directly injects the fuel amount corresponding to the valve opening pulse width and the fuel pressure into the combustion chamber, and the fuel injection at start-up so that the target air-fuel ratio is obtained at start-up. Start-time fuel injection pulse width calculating means for calculating the pulse width, start-time fuel injection timing setting means for setting the start-time fuel injection timing, the set start-time fuel injection timing, and the calculated start-time fuel injection In an engine start time fuel injection control device comprising a signal output means for outputting a pulse width signal to the fuel injection valve, an intake pressure detecting means for detecting an intake pressure, and a fuel pressure detecting means for detecting the fuel pressure Wherein the predicted in-cylinder pressure at the intake valve closing timing from the intake pressure detected by the intake pressure detecting means at the time of starting, the difference between the actual fuel pressure and the predicted in-cylinder pressure detected by the fuel pressure detecting means during startup And correcting at least one of the calculated start-time fuel injection pulse width and the set start-time fuel injection timing based on pressure, further comprising a crank angle sensor, and the in-cylinder pressure predicting means includes the intake valve A predetermined crank angle range centering on the closing timing is divided into a plurality of parts, and the suction is performed at a timing at which the actual crank angle detected by the crank angle sensor at the start coincides with each of the crank angles divided into the plurality of parts. The intake pressure detected by the atmospheric pressure detection means is sampled, and the minimum data among the sampled sampling data is determined at the intake valve closing timing. Since predicting the in-cylinder pressure, even when manufacturing errors can be suppressed variations in the fuel injection amount during start-up, the target air-fuel ratio at the time of start-up is obtained. Thereby, the discharge of unburned HC at the time of starting can be further suppressed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an engine start fuel injection control device.

  In FIG. 1, a throttle valve 7 for adjusting the amount of intake air is installed upstream of the intake collector 8 of the engine 1. The opening degree of the throttle valve 7 is controlled by a step motor 15 that operates according to a signal from the engine controller 21.

  An intake valve 5 is provided at the opening of the intake port 2 to the combustion chamber 4, and an exhaust valve 6 is provided at the opening of the exhaust port 3 to the combustion chamber 4. A fuel injection valve 13 is installed in the combustion chamber 4 of the engine 1 together with a spark plug 14. The fuel injection valve 13 is opened in response to a fuel injection pulse signal output from the engine controller 21, and the fuel from the fuel tank 11 discharged from the fuel pump 12 and regulated to a predetermined pressure is synchronized with the engine rotation. The fuel is directly injected into the combustion chamber 4 at a predetermined timing.

  An exhaust purification catalyst 16 is provided in the exhaust passage 8 (more precisely, downstream of the exhaust manifold assembly) of the engine 1.

  The engine controller 21 includes an accelerator opening (depressed amount of the accelerator pedal) detected by an accelerator pedal sensor (not shown), an engine speed detected by a crank angle sensor 24, and an intake air flow rate detected by an air flow meter 22. The throttle opening detected by the throttle sensor 23, the engine coolant temperature detected by the water temperature sensor 25, and the temperature of the catalyst 16 detected by the temperature sensor 26 are input.

  Based on the engine operating conditions detected from these input signals, the engine controller 21 performs homogeneous combustion (combustion with the air-fuel mixture spread over the entire combustion chamber 4) or stratified combustion (ignition plug). Combustion method for performing combustion in a state where the air-fuel mixture is concentrated is set, and the opening of the throttle valve 7, the fuel injection timing of the fuel injection valve 13, and the fuel injection valve are set in accordance with the set combustion method The fuel injection amount from 13 and the ignition timing of the spark plug 14 are controlled.

  On the other hand, early catalyst warm-up is performed in an idle state immediately after the cold start. This will be described with reference to FIG. 2. FIG. 2 shows that the engine speed, the combustion switching flag, the throttle opening, and the pressure of the intake collector 8 are maintained when the idling state is maintained without depressing the accelerator pedal from the cold start of the engine. (Hereinafter referred to as “collector pressure”), how the ignition timing and the temperature of the catalyst 16 change are shown by a model.

  As shown in the uppermost part of FIG. 2, the engine speed Ne suddenly increases with the start of cranking by the starter motor, slightly overshoots across the predetermined value N1, and then to the first idle speed (for example, about 1000 rpm to 1200 rpm). And calm down. In this case, the engine rotation speed Ne is compared with a predetermined value N1 (for example, about 1400 rpm), and it is determined that the engine has been started at the timing t1 when the engine rotation speed Ne becomes equal to or higher than the predetermined value N1. Let the machine do.

  The present retard stratified combustion realizing means is used as the catalyst early warm-up means here. The retarded stratified combustion itself is publicly known (see JP 2008-25535 A). When this retarded stratified combustion is outlined, when the catalyst 16 is not activated, ignition is performed with the ignition timing set to, for example, 15 to 30 deg CA after compression top dead center. Further, fuel injection is performed by setting the fuel injection timing (the fuel injection start timing; the same applies hereinafter) after the compression top dead center and before the ignition timing, that is, the expansion stroke. The fuel injection is further divided into two times. The second fuel injection is used as the fuel injection in the expansion stroke, and the fuel injection is performed in the compression stroke as the first fuel injection preceding this. Also, the air-fuel ratio in the combustion chamber by fuel injection (the fuel injection is divided into two times, so the air-fuel ratio in the combustion chamber by two fuel injection totals) is slightly leaner than the stoichiometric air-fuel ratio (for example, 16 To 17). Such combustion with the ignition timing delayed after compression top dead center is also stratified combustion, but the ignition timing is delayed after compression top dead center to distinguish it from normal stratified combustion with ignition timing before compression top dead center This type of combustion is termed “retarded stratified combustion”. The retarded stratified combustion described in Japanese Patent Application Laid-Open No. 2008-25535 is called a spray guide method, but the retarded stratified combustion employed in the present embodiment is not limited to this, and may be a wall-guided retarded stratified combustion. . This wall guide type is also known (see, for example, JP-A-2006-307691). In the wall guide type retarded stratified combustion, the injection timing is slightly different from the spray guide type retarded stratified combustion, the first fuel injection is fuel injection in the first half of the compression stroke, and the second fuel injection is fuel injection in the second half of the compression stroke. It has become. FIG. 1 does not accurately represent the arrangement of the fuel injection valve 13 and the cavity provided on the piston crown surface.

  Returning to FIG. 2, the ignition timing is set to a predetermined value ADV0 (ignition timing slightly retarded from the ignition timing at which MBT is obtained), and the engine is started. In the present invention, stratified combustion is performed when the engine is started. Here, “at the time of start” is a period from the start of cranking to the timing of t1 when the engine start is completed. Hereinafter, “at the time of starting” means a period from the start of cranking to the completion of starting of the engine. In the stratified combustion at the start-up, the fuel injection is not divided into two times like the retarded stratified combustion from t1, and the stratified combustion is performed by one fuel injection. The fuel injection timing IT0 at start-up is the latter half of the expansion stroke in the case of the spray guide method and the latter half of the compression stroke in the case of the wall guide method. In addition, the target air-fuel ratio at the time of start-up is an air-fuel ratio slightly leaner than the stoichiometric air-fuel ratio (the same as during retarded stratified combustion).

  The engine is switched to retarded stratified combustion at the timing t1 when it is determined that the engine has been started. That is, the ignition timing is retarded stepwise from the predetermined value ADV0 to the predetermined value ADV1 (ignition timing retarded combustion stability limit in stratified combustion), and the throttle opening is stepped from the idle equivalent value TVOidl by the predetermined value ΔTVO. It is assumed that the predetermined value TVO1 (= TVOidl + ΔTVO) is increased. The combustion mode continues stratified combustion. By performing retarded stratified combustion in the idle state after the start is completed, the temperature of the catalyst 16 rises as shown in the lowermost stage of FIG. 2, and a predetermined value T2 that is the temperature at which the catalyst 16 is activated at the timing t2. To reach. In order to perform post-processing after the activation of the catalyst 16, the throttle opening is returned to the idle equivalent value TVOidl at t2, and the ignition timing is shifted from the predetermined value ADV1 to the basic ignition timing ADV2 at which MBT is obtained. The combustion mode is switched from stratified combustion to homogeneous combustion. The above is the content of the retarded stratified combustion.

  FIG. 3 shows the change in engine speed from the start of cranking. In this case, the air flow meter 22 is operating from the start of cranking to the point where the rotational speed suddenly increases, but the intake air already existing in the collector 8 is sucked into the combustion chamber 4 during cranking. Since the fuel is injected and burned, the intake detected by the air flow meter 22 is calculated even if the fuel injection pulse width is calculated using the intake air amount Qa detected by the air flow meter 22 located upstream of the collector 8. The air amount Qa does not represent the amount of intake air actually flowing into the combustion chamber 4 (the amount of intake air flowing into the combustion chamber 4 is hereinafter referred to as “cylinder air flow rate”). The unit of the cylinder air amount is, for example, [g / s], which is actually a flow rate.

On the other hand, after the start of the engine is completed, from the cylinder air amount Qcyl (a known value calculated based on the intake air amount Qa detected by the air flow meter 22) and the engine speed Ne,
Tp = K × Qcyl / Ne (1)
Where K is a constant,
The basic injection pulse width Tp [ms] is calculated by the following formula, and using this basic injection pulse width Tp,
Ti = Tp × TFBYA × (α + αm−1) × KINJ × 2 + Ts
... (2)
= Te + Ts (3)
However, TFBYA; target equivalent ratio [anonymous number],
α: Air-fuel ratio feedback correction coefficient [anonymous number],
αm: air-fuel ratio learning value [anonymous number],
KINJ; fuel pressure correction coefficient [unknown number],
Ts; invalid pulse width [ms],
Te: Effective pulse width [ms],
The sequential fuel injection pulse width Ti [ms] (this fuel injection pulse width is hereinafter referred to as “normal fuel injection pulse width”) is calculated by the following formula.
T1 = Te × 1.3 + Ts (4)
T2 = Tst × Knst × Ktst (5)
Where Te: effective pulse width [ms],
Ts; invalid pulse width [ms],
Tst: Basic injection pulse width at start [ms]
Knst; rotational speed correction coefficient [anonymous number],
Ktst; time correction coefficient [anonymous number],
The first fuel injection pulse width T1 [ms] and the second fuel injection pulse width T2 [ms] are calculated by the following two formulas, and the larger of these two values is set as the starting fuel injection pulse width T3 [ms]. It is set. In short, the first fuel injection pulse width T1 in the equation (4) is a value determined by the intake air amount Qa, whereas the second fuel injection pulse width T2 in the equation (5) is equal to the engine coolant temperature Tw. A value determined by the cranking rotation speed and the cranking time, that is, a value not related to the cylinder air amount Qcyl. When starting, the second fuel injection pulse width T2 is usually larger than the first fuel injection pulse width T1, and therefore the second fuel injection pulse width T2 is set as the start time fuel injection pulse width T3 during startup.

  In association with FIG. 2, before the start is completed, the second fuel injection pulse width T2 of the equation (5) is given to the fuel injection valve 13 of each cylinder as the start time fuel injection pulse width T3, and the start is completed t1. The normal fuel injection pulse width Ti of the equation (2) is given to the fuel injection valve 13 of each cylinder. Since the oxygen sensor 27 provided upstream of the catalyst 16 in the exhaust passage 8 is activated at a timing slightly before t2 when the catalyst 16 is activated, air-fuel ratio feedback control is started at the timing when the oxygen sensor 27 is activated. , The air-fuel ratio feedback correction coefficient α in the equation (2) is calculated. Before the oxygen sensor 27 is activated, the air-fuel ratio feedback correction coefficient α = 1.0.

  There are manufacturing errors in the opening area of the throttle valve 7, the opening area when the intake valve 5 is lifted, the cylinder bore diameter, the piston diameter, and the like. Due to this manufacturing error, the opening area of the throttle valve 7 varies, the intake valve 5 lifts. Variations in the opening area at the time, variations in the friction between the piston and cylinder, repeated variations, etc. cannot be avoided. That is, it has been found that the cylinder air amount varies due to manufacturing errors, which causes a variation in the actual air-fuel ratio from the target air-fuel ratio, which deteriorates the HC concentration at the engine outlet. Here, after the start of the engine is completed, the HC concentration at the engine outlet is reduced while the temperature of the catalyst 16 is raised quickly by retarded stratified combustion. The period from the start of ranking to the completion of engine start, that is, at the start. Therefore, the following is considered at the time of starting.

  FIG. 4 shows the in-cylinder pressure waveform during motoring. “Motoring” refers to operating the engine with fuel supply and ignition stopped. The reason for handling the motoring is that the in-cylinder pressure itself generated by the cylinder air amount is focused.

  Here, if the ideal engine with no manufacturing error is the “reference engine” and the in-cylinder pressure changes as shown by the solid line in this reference engine, the engine with the manufacturing error is caused by variations in the cylinder air amount. The change in in-cylinder pressure becomes a one-dot chain line or a broken line. If the engine whose cylinder air amount is larger than the reference engine due to manufacturing errors is referred to as "first engine", and conversely, the engine whose cylinder air amount is smaller than the reference engine due to manufacturing errors is referred to as "second engine". The internal pressure is higher than that of the reference engine, and conversely, in the second engine, the in-cylinder pressure is lower than that of the reference engine. Since the second fuel injection pulse width T2 that is the fuel injection pulse width T3 at the start time is a value that is not related to the cylinder air amount Qcyl as described above, it does not change even if the cylinder air amount varies in this way. When starting, the air-fuel ratio varies from the target air-fuel ratio. This is due to the variation in the cylinder air amount and the variation in the in-cylinder pressure due to the variation in the cylinder air amount resulting in a variation in the differential pressure between the in-cylinder pressure and the fuel pressure. Then, the HC concentration at the engine outlet may deteriorate at the start-up due to variations in the air-fuel ratio from the target air-fuel ratio. For example, FIG. 5 is a characteristic diagram showing the relationship between the air-fuel ratio and the HC concentration at the engine outlet, and is produced when the target air-fuel ratio is a predetermined value A (16 to 17 as described above) at the start of stratified combustion. If the actual air-fuel ratio reaches the predetermined value B due to the error, the HC concentration at the engine outlet will increase by the amount deviated from the target air-fuel ratio to the lean side.

  Therefore, the present invention predicts the in-cylinder pressure at the fuel injection timing by sampling the collector pressure (intake pressure) history centering on the intake valve closing timing at the start of the previous operation, and the predicted fuel injection timing. The in-cylinder pressure is stored in the memory, and at the start of the current operation, the differential pressure between the in-cylinder pressure at the stored fuel injection timing and the actual fuel pressure is calculated, and based on the calculated differential pressure By correcting the fuel injection pulse width T3 at the start and the fuel injection timing IT0 at the start, the target air-fuel ratio can be obtained at the start even if there is a manufacturing error. Here, the collector pressure is detected by the pressure sensor 28 (intake pressure detecting means), and the actual fuel pressure is detected by the fuel pressure sensor 29 (fuel pressure detecting means).

  This will be described with reference to FIG. 6 and FIG. 7. FIG. 6 shows how the collector pressure at the start of the reference engine, the first engine, and the second engine in a predetermined crank angle section centered on the intake valve closing timing IVC. This shows how it changes. In any of the three engines, when the intake valve 5 is opened at the time of starting, the collector pressure decreases as the piston decreases, and when the intake valve 5 is closed, the intake valve 5 is closed, that is, the intake valve closing timing θivc. The collector pressure becomes higher again.

  The in-cylinder pressure Pivc at the intake valve closing timing θivc is equal to the collector pressure at the intake valve closing timing θivc. Accordingly, a predetermined crank angle range centered on the intake valve closing timing θivc, for example, the first crank angle θ1 and the second crank angle θ2 is set, and n−1 (between the two crank angles θ1 and θ2 ( The collector pressure detected by the pressure sensor 28 is sampled at a timing at which the actual crank angle θ detected by the crank angle sensor 24 coincides with each of the n−1 equally divided crank angles. When (detected), a total of n pieces of sampling data are obtained. The minimum data among the plurality of sampling data is obtained as the collector pressure at the intake valve closing timing θivc, that is, the in-cylinder pressure Pivc at the intake valve closing timing θivc. As shown in FIG. 6, the in-cylinder pressure Pivc1 at the intake valve closing timing of the first engine is smaller than the in-cylinder pressure Pivc0 at the intake valve closing timing of the reference engine. The in-cylinder pressure Pivc2 is larger than the in-cylinder pressure Pivc0 when the intake valve of the reference engine is closed.

  FIG. 7 again shows the changes in the in-cylinder pressure during motoring for the reference engine, the first engine, and the second engine. Assuming that the fuel injection timing (fuel injection start timing) IT0 at the start is at a predetermined crank angle (expansion stroke in the spray guide method, and in the latter half of the compression stroke in the wall guide method), as described above, Assuming that the differential pressure ΔP0 between the actual fuel pressure Pf and the in-cylinder pressure P0 at the fuel injection timing IT0 is a “reference differential pressure”, in the first engine, the differential pressure ΔP1 between the actual fuel pressure Pf and the in-cylinder pressure P1 at the fuel injection timing IT0. In contrast, in the second engine, the differential pressure ΔP2 between the actual fuel pressure Pf and the in-cylinder pressure P2 at the fuel injection timing IT0 is larger than the reference differential pressure ΔP0.

Here, the fuel injection amount Gf [g / cyl] at the start is
Gf = T3 × (differential pressure between actual fuel pressure Pf and in-cylinder pressure at fuel injection timing IT0) × (constant)
(6)

Where T3: fuel injection pulse width at start-up,
Therefore, even if the starting fuel injection pulse width T3 is the same, the starting fuel injection amount Gf differs depending on the differential pressure between the actual fuel pressure Pf and the in-cylinder pressure at the fuel injection timing IT0. The fuel injection amount Gf at the time of start is insufficient and the actual air / fuel ratio becomes the target air / fuel ratio at the start when the difference ΔP1 between the actual fuel pressure Pf and the in-cylinder pressure at the fuel injection timing IT0 becomes smaller than the reference differential pressure ΔP0. In contrast, in the second engine, the fuel injection amount Gf at the start is increased by the amount by which the differential pressure ΔP2 between the actual fuel pressure Pf and the in-cylinder pressure P2 at the fuel injection timing IT0 is larger than the reference differential pressure ΔP0. Becomes excessive, and the actual air-fuel ratio tends to be richer than the target air-fuel ratio at the start.

  In order to eliminate the variation of the air-fuel ratio from the target air-fuel ratio at the time of starting in the first engine and the second engine, in the case of the first engine, the difference between the actual fuel pressure Pf and the in-cylinder pressure P1 at the fuel injection timing IT0. The fuel injection pulse width T3 at the time of start is increased and corrected according to the deviation ΔP01 of the pressure ΔP1 from the reference differential pressure ΔP0. In contrast, in the case of the second engine, the cylinder at the actual fuel pressure Pf and the fuel injection timing IT0 is corrected. The starting fuel injection pulse width T3 may be corrected by decreasing the amount according to the deviation ΔP02 of the differential pressure ΔP2 from the internal pressure P2 from the reference differential pressure ΔP0.

Therefore, in the present invention, the injection pulse width correction coefficient Khos1 [unknown number] having the characteristics shown in FIG. 8A is newly introduced, and the starting fuel injection pulse width T3 [ms] with this injection pulse width correction coefficient Khos1. ], That is, T3hos = T3 × Khos1 (7)
The post-correction starting fuel injection pulse width T3hos [ms] is calculated by the following equation.

  In FIG. 8A, the predetermined value C corresponds to the differential pressure ΔP0 obtained by subtracting the in-cylinder pressure P0 at the fuel injection timing IT0 from the actual fuel pressure Pf in the case of the reference engine. That is, in the reference engine, the differential pressure ΔP0 obtained by subtracting the in-cylinder pressure P0 at the fuel injection timing IT0 from the actual fuel pressure Pf coincides with the predetermined value C. At this time, the injection pulse width correction coefficient Khos1 becomes 1.0, From the equation (7), the corrected fuel injection pulse width T3hos at the start matches the fuel injection pulse width T3 at the start.

  On the other hand, in the first engine, the differential pressure ΔP1 obtained by subtracting the in-cylinder pressure P1 at the fuel injection timing IT0 from the actual fuel pressure Pf becomes smaller than a predetermined value C, and the injection pulse width correction coefficient Khos1 is 1.0 from FIG. The value exceeds. On the contrary, in the second engine, the differential pressure ΔP2 obtained by subtracting the in-cylinder pressure P2 at the fuel injection timing IT0 from the actual fuel pressure Pf becomes larger than a predetermined value C, and the injection pulse width correction coefficient Khos1 is a positive value smaller than 1.0. It becomes. As a result, as shown in FIG. 9, the corrected starting fuel injection pulse width T3hos in the first engine becomes larger than the corrected starting fuel injection pulse width T3hos in the reference engine (the dashed-dotted arrow in the upper part of FIG. 9). Further, the corrected start fuel injection pulse width T3hos in the second engine is smaller than the corrected start fuel injection pulse width T3hos in the reference engine (see the broken line arrow at the top of FIG. 9). Note that the pulse width shown in the upper part of FIG. 9 is merely a model and does not represent an actual pulse width.

  In FIG. 8A, the horizontal axis represents the differential pressure obtained by subtracting the in-cylinder pressure at the fuel injection timing IT0 from the actual fuel pressure Pf, but the in-cylinder pressure at the fuel injection timing IT0 is obtained at the intake valve closing timing θivc. As shown in FIG. 8 (B), the horizontal axis may be approximated to be approximately equal to the in-cylinder pressure Pivc, and the differential pressure obtained by subtracting the in-cylinder pressure Pivc at the intake valve closing timing θivc from the actual fuel pressure Pf may be used.

  The target fuel pressure is determined in advance by the engine operating conditions (engine load and rotational speed Ne), and the fuel pressure control is performed so that the actual fuel pressure Pf matches the target fuel pressure. In the case of driving, since the actual fuel pressure Pf rises from the zero state to the target fuel pressure as cranking starts, the actual fuel pressure Pf changes greatly at the start. Even during such a large change in the actual fuel pressure Pf, the above equation (6) can be used. That is, even when the actual fuel pressure Pf is changing greatly at the start, according to the present invention, the variation in the fuel injection amount can be suppressed, and the target air-fuel ratio at the start can be obtained.

  As described above, the case where the start time fuel injection pulse width T3 is corrected based on the differential pressure obtained by subtracting the in-cylinder pressure at the fuel injection timing IT0 from the actual fuel pressure Pf has been described. However, the present invention is not limited to this case. The fuel injection timing IT0 at the start may be corrected based on the differential pressure obtained by subtracting the in-cylinder pressure at the fuel injection timing IT0 from the actual fuel pressure Pf. Alternatively, both the starting fuel injection pulse width T3 and the starting fuel injection timing IT0 may be corrected.

  Next, the case of correcting the fuel injection timing IT0 at the start will be described with reference to FIG. 13. FIG. 13 is basically the same as FIG. In the first engine, since the in-cylinder pressure P1 at the fuel injection timing IT0 is larger than the in-cylinder pressure P0 at the fuel injection timing IT0 of the reference engine by a deviation ΔP01, the fuel injection amount Gf at the start is insufficient. If fuel injection is performed at a crank angle (IT1 in the figure) at which the in-cylinder pressure of one engine matches the in-cylinder pressure P0 at the fuel injection timing IT0 of the reference engine, the difference between the actual fuel pressure Pf and the in-cylinder pressure at the fuel injection timing IT1. The pressure becomes the same ΔP0 as that of the reference engine, and the shortage of the fuel injection amount Gf at the start can be solved. On the contrary, in the second engine, the in-cylinder pressure P2 at the fuel injection timing IT0 is smaller than the in-cylinder pressure P0 at the fuel injection timing IT0 of the reference engine by a deviation ΔP02, so the fuel injection amount Gf at the start is excessive. Therefore, if fuel injection is performed at the crank angle (IT2 in the drawing) at which the in-cylinder pressure in the second engine matches the in-cylinder pressure P0 at the fuel injection timing IT0 of the reference engine, the actual fuel pressure Pf and the fuel injection timing IT2 The difference in pressure with the in-cylinder pressure becomes ΔP0, which is the same as that of the reference engine, and an excessive fuel injection amount Gf at the start can be solved.

Therefore, in the present invention, the injection timing correction amount Khos2 [degCA] having the characteristics shown in FIG. 14A is newly introduced, and the start-time fuel injection timing IT0 [degCA BTDC] is corrected with this injection timing correction amount Khos2. That is, IThos = IT0 + Khos2 (8)
The post-correction starting fuel injection timing IThos [degCA BTDC] is calculated by the following equation. Here, as a unit of the starting fuel injection timing IT0, for example, as shown in FIG. 15, a crank angle measured from the exhaust stroke end timing to the advance side is adopted. At this time, if the injection timing correction amount Khos2 on the right side of the equation (8) is a positive value, the starting fuel injection timing IT0 is advanced, and conversely, the injection timing correction amount on the right side of the equation (8). If Khos2 is a negative value, the starting fuel injection timing IT0 is retarded.

  In FIG. 14A, the predetermined value C corresponds to a differential pressure ΔP0 obtained by subtracting the in-cylinder pressure P0 at the fuel injection timing IT0 from the actual fuel pressure Pf in the case of the reference engine. That is, in the reference engine, the differential pressure ΔP0 obtained by subtracting the in-cylinder pressure P0 at the fuel injection timing IT0 from the actual fuel pressure Pf coincides with the predetermined value C. At this time, the injection timing correction amount Khos2 becomes zero, and the above equation (8) Further, the corrected fuel injection timing IThos at the start coincides with the fuel injection timing IT0 at the start.

  On the other hand, in the first engine, the differential pressure ΔP1 obtained by subtracting the in-cylinder pressure P1 at the fuel injection timing IT0 from the actual fuel pressure Pf becomes smaller than a predetermined value C, and the injection timing correction amount Khos2 becomes a positive value from FIG. Become. On the other hand, in the second engine, the differential pressure ΔP2 obtained by subtracting the in-cylinder pressure P2 at the fuel injection timing IT0 from the actual fuel pressure Pf becomes larger than a predetermined value C, and the injection timing correction amount Khos2 is a negative value from FIG. It becomes. As a result, as shown in FIG. 13, the corrected starting fuel injection timing IThos in the first engine becomes a crank angle IT1 that is more advanced than the corrected starting fuel injection timing IT0 in the reference engine, and the second engine. The post-correction start fuel injection timing IThos in FIG. 4 becomes the crank angle IT2 that is retarded from the post-correction start fuel injection timing IT0 in the reference engine.

  In FIG. 14A, the horizontal axis is the differential pressure obtained by subtracting the in-cylinder pressure at the fuel injection timing IT0 from the actual fuel pressure Pf, but the in-cylinder pressure at the fuel injection timing IT0 is at the intake valve closing timing θivc. It is approximated as being substantially equal to the in-cylinder pressure Pivc, and as shown in FIG. 14B, the horizontal axis may be a differential pressure obtained by subtracting the in-cylinder pressure Pivc at the intake valve closing timing θivc from the actual fuel pressure Pf.

  This control executed by the engine controller 21 will be described in detail based on the flowcharts of FIGS. However, here, a description will be given of a case where the starting fuel injection pulse width T3 is corrected based on the differential pressure obtained by subtracting the in-cylinder pressure at the fuel injection timing IT0 from the actual fuel pressure Pf. 10 to 12, the control other than the idle state is omitted.

  First, FIG. 10 is for setting the start completion flag, and is executed at regular intervals (for example, every 10 ms).

  Step 1 looks at the ignition switch. When the ignition switch is ON, the process proceeds to step 2 to see the starter switch. When the starter switch is ON, it is determined that cranking is in progress and the routine proceeds to step 3 where the start completion flag = 0 is set.

  When the starter switch is OFF in step 2, it is determined that cranking has been completed, and the routine proceeds to step 4, where the engine speed Ne detected by the crank angle sensor 24 is compared with a predetermined value N1. The predetermined value N1 is a value for determining whether or not the engine has been started, and is determined in advance by adaptation. The predetermined value N1 is about 1400 rpm, for example. When the engine speed Ne is less than the predetermined value N1, it is determined that the engine has not yet been started, and a start completion flag = 0 is set in step 5. On the other hand, when the engine rotational speed Ne becomes equal to or higher than the predetermined value N1 in step 4, it is determined that the engine has been started, and the routine proceeds to step 6 where the start completion flag = 1 is set.

  FIG. 11 is for setting the combustion switching flag, and is executed at regular intervals (for example, every 10 ms) following FIG.

  In step 11, the start completion flag (set according to FIG. 10) is observed. When the start completion flag = 0, that is, when the engine has not yet been started, the routine proceeds to step 12 where the combustion switching flag = 1 is set. The combustion switching flag is a flag for instructing the combustion mode. The combustion switching flag = 1 indicates stratified combustion, and the combustion switching flag = 0 indicates homogeneous combustion.

  On the other hand, if the start completion flag = 1 in step 11, that is, if the engine has started, the process proceeds to step 13 where the coolant temperature Tst at the start start timing is compared with a predetermined value T1. The predetermined value T1 is a value for determining whether or not the engine is cold start. In order to obtain the coolant temperature at the start start timing, the coolant temperature Tw at that time may be stored in the memory as the coolant temperature Tst at the start start timing when the ignition switch is switched from OFF to ON. Here, “starting start timing” is used in a different meaning from the “starting time”. If the cooling water temperature Tst at the start timing exceeds the predetermined value T1, it is determined that the hot start is in progress, and therefore early catalyst warm-up is not necessary, and the routine proceeds to step 16 where the combustion switching flag = 0.

  If the coolant temperature Tst at the start timing is equal to or lower than the predetermined value T1, it is determined that the engine is cold start, and the routine proceeds to step 14 where the catalyst temperature Tcat detected by the temperature sensor 26 is compared with the predetermined value T2. The predetermined value T2 is a value for determining whether or not the catalyst 16 is activated. When the catalyst temperature Tcat is less than the predetermined value T2, it is determined that the catalyst 16 has not yet been activated, and the routine proceeds to step 15 where the combustion switching flag = 1 is set.

  While the catalyst 16 is in an inactive state, the operations of steps 14 and 15 are executed. As a result, retarded stratified combustion continues as will be described later. When the catalyst temperature Tcat eventually becomes equal to or higher than the predetermined value T2 due to the continuation of this process, it is determined that the catalyst 16 has been activated, and the retarded stratified combustion is stopped to switch to the homogeneous combustion. And

  FIG. 12 is for calculating the ignition timing and the fuel injection pulse width and setting the fuel injection timing according to the combustion mode, and is executed at regular intervals (for example, every 10 ms) following the flow of FIG.

  Here, the ignition timing in the homogeneous combustion is before the compression top dead center, and the ignition timing in the retarded stratified combustion is after the compression top dead center. For this reason, when the crank angle [degCA BTDC] measured from the compression top dead center to the advance side is employed, the ignition timing in the retarded stratified combustion becomes a negative value and is difficult to handle. Therefore, in the present embodiment, for example, a crank angle [degCA ATDC] that is measured on the retard side from the intake top dead center (TDC) is employed. Thus, by taking the starting point of the ignition timing again, it is possible to handle the ignition timing with a positive value both before the start is completed and from the start completion to the catalyst activation after the catalyst activation.

  In step 31, it is checked whether or not the engine is in an idle state. When it is in the idling state, the process proceeds to step 32, and the start completion flag (set by FIG. 10) is observed. When the start completion flag = 0, it is determined that the engine has not yet been started and the routine proceeds to steps 33-41. Steps 33 to 41 are a control part at the start. First, in step 33, a predetermined value ADV0 [degCA ATDC] is input to the ignition timing ADV [degCA ATDC]. The predetermined value ADV0 is an optimum ignition timing when starting with stratified combustion at the start, that is, an ignition timing slightly retarded from MBT, and is, for example, 0 to 10 [degCA BTDC].

  Steps 34 to 36 are parts for calculating the starting fuel injection pulse width T3. That is, in steps 34 and 35, the first fuel injection pulse width T1 and the second fuel injection pulse width T2 are calculated by the above equations (4) and (5), and in step 36, the larger one of these two pulse widths. Is set as the starting fuel injection pulse width T3.

In step 37, the pressure difference ΔP between the in-cylinder pressure Pivc at the intake valve closing timing θivc stored in the memory and the actual fuel pressure Pf detected by the pressure sensor 29 is calculated as follows:
ΔP = Pf−Pivc (9)
In step 38, an injection pulse width correction coefficient Khos1 is calculated from this differential pressure ΔP by searching a table containing the content of FIG. 8B. In step 39, the starting fuel injection pulse width T3 is calculated. The value corrected by the injection pulse width correction coefficient Khos1 is used as the corrected fuel injection pulse width T3hos at the start, that is, T3hos = T3 × Khos1 (10)
The post-correction starting fuel injection pulse width T3hos is calculated by the following equation.

  As shown in FIG. 8B, the injection pulse width correction coefficient Khos1 is 1.0 when the differential pressure ΔP between the actual fuel pressure Pf and the in-cylinder pressure Pivc at the intake valve closing timing θivc is a predetermined value C. Further, when the differential pressure ΔP between the actual fuel pressure Pf and the in-cylinder pressure Pivc at the intake valve closing timing θivc exceeds a predetermined value C, it becomes a positive value smaller than 1.0, and at the actual fuel pressure Pf and the intake valve closing timing θivc When the differential pressure ΔP from the in-cylinder pressure Pivc is smaller than the predetermined value C, the value is larger than 1.0. Due to this injection pulse width correction coefficient Khos1, the starting fuel injection pulse width T3 is reduced when the differential pressure ΔP between the actual fuel pressure Pf and the in-cylinder pressure Pivc at the intake valve closing timing θivc exceeds a predetermined value C, and the actual fuel pressure When the differential pressure ΔP between Pf and the in-cylinder pressure Pivc at the intake valve closing timing θivc is smaller than a predetermined value C, the increase is corrected.

  The in-cylinder pressure Pivc at the intake valve closing timing θivc is calculated (predicted) as follows. That is, as shown in FIG. 6, the crank is from the first crank angle θ1 determined on the advance side relative to the intake valve closing timing θivc to the second crank angle θ2 determined on the retard side relative to the intake valve close timing θivc. The angular range is divided into n-1 (n is an integer equal to or greater than 3), and the actual crank angle θ detected by the crank angle sensor 24 at the time of starting coincides with each crank angle divided into n-1 equal parts. Then, the current collect pressure detected by the pressure sensor 28 is sampled and stored in the memory. Then, at the timing when the actual crank angle θ exceeds the second crank angle θ2, n sampling data are accumulated in the memory. If the minimum data among the n sampling data is selected, the selected minimum data is obtained as the in-cylinder pressure Pivc at the intake valve closing timing θivc. The in-cylinder pressure Pivc at the intake valve closing timing θivc obtained in this manner is not in time for the calculation of the corrected fuel injection pulse width T3hos at the start of the current operation at which this value is obtained, and is stored in the nonvolatile memory. It is used for the calculation of the corrected fuel injection pulse width T3hos at the start of the next operation. That is, the in-cylinder pressure Pivc at the intake valve closing timing θivc used in step 37 is a value (predicted value) obtained at the start of the previous operation.

  The calculation (prediction) of the in-cylinder pressure Pivc at the intake valve closing timing θivc at the time of starting is performed for each cylinder in a multi-cylinder engine. The engine start completion timing may be reached before the calculation (prediction) of the in-cylinder pressure Pivc at the intake valve closing timing θivc for all the cylinders. For example, as shown in the uppermost stage of FIG. 2 for a four-cylinder engine, if combustion is completed after three cylinders have been started, the in-cylinder pressure Pivc at the intake valve closing timing θivc is calculated for the fourth cylinder. I can't. In this case, the average value of the in-cylinder pressure Pivc at the intake valve closing timing θivc for the three cylinders is obtained and stored in the nonvolatile memory, and this average value is corrected after starting fuel injection pulse at the start of the next operation. Used to calculate the width T3hos. Of course, if the engine start completion timing comes after the calculation of the in-cylinder pressure Pivc at the intake valve closing timing θivc for all the cylinders, the average value of the in-cylinder pressure Pivc at the intake valve closing timing θivc for all the cylinders Is stored in a non-volatile memory, and this average value is used to calculate the corrected fuel injection pulse width T3hos at the start of the next operation.

  In step 40, the corrected starting fuel injection pulse width T3hos thus obtained is transferred to the output register.

  In step 41, the fuel injection timing IT0 in stratified combustion is set. The fuel injection timing IT0 in the stratified combustion is in the expansion stroke in the case of the spray guide method and in the latter half of the compression stroke in the case of the wall guide method.

  When the start completion flag is 1 at step 32, it is determined that the engine has been started, and the routine proceeds to step 42, where the normal fuel injection pulse width Ti is calculated by the above equation (2). The fuel injection pulse width Ti is moved to the output register.

  In step 44, the combustion switching flag (set according to FIG. 11) is checked. When the combustion switching flag = 1, the routine proceeds to step 45, where the predetermined value ADV1 [degCA ATDC] is entered in the ignition timing ADV. The predetermined value ADV1 is a retard side combustion stability limit of the ignition timing in the stratified combustion when the throttle opening is the predetermined value TVO1.

  In step 46, the fuel injection timing in the retarded stratified combustion is set. In the case of the wall guide method, the fuel injection timing in the stratified combustion is the first half of the compression stroke and the second is the second half of the compression stroke.

  On the other hand, when the combustion switching flag = 0 in step 44, that is, when the catalyst 16 is activated, the routine proceeds to step 47, where the basic ignition timing ADV2 [degCA ATDC] from which MBT is obtained is entered as the ignition timing ADV.

  In step 48, the fuel injection timing in homogeneous combustion is set. The fuel injection timing in homogeneous combustion is in the first half of the intake stroke.

  The engine controller 21 generates a fuel injection signal from the post-correction starting fuel injection pulse width T3hos thus transferred to the output register and the set fuel injection timing, and outputs the fuel injection signal to the fuel injection valve 13. At the time of starting, the fuel injection valve 13 is opened for each cylinder during the corrected starting fuel injection pulse width T3hos from the fuel injection timing IT0, and the fuel amount corresponding to the valve opening pulse width and the actual fuel pressure is combusted. It is injected into the chamber 4.

  Here, the effect of this embodiment is demonstrated.

  In the direct injection type engine, even when the fuel injection pulse T3 at the start is the same, the fuel injection amount Gf at the start varies due to the difference in the differential pressure between the actual fuel pressure Pf and the in-cylinder pressure at the fuel injection timing IT0 due to manufacturing errors. However, according to the present embodiment (the invention described in claim 1), the fuel injection valve 13 and the start time fuel injection pulse width T3 are calculated so that the target air-fuel ratio is obtained at the start time. Fuel injection pulse width calculating means (see steps 32 and 34 to 36 in FIG. 12), start fuel injection timing setting means for setting start fuel injection timing IT0 (see steps 32 and 41 in FIG. 12), And a signal output means (see step 40 in FIG. 12) for outputting a signal of the set start time fuel injection timing IT0 and the calculated start time fuel injection pulse width T3 to the fuel injection valve 13. In the engine start-up fuel injection control apparatus, a cylinder for predicting the in-cylinder pressure from the pressure sensor 28 (intake pressure detecting means), the fuel pressure sensor 29 (fuel pressure detecting means), and the intake pressure detected by the pressure sensor 28 at the start. Injection pulse width / injection for correcting the fuel injection pulse width T3 at the start based on the internal pressure prediction means and the differential pressure ΔP between the actual fuel pressure Pf detected by the fuel pressure sensor 29 at the start and the predicted in-cylinder pressure (Pivc) Since the timing correction means (see steps 38 and 39 in FIG. 12) is provided, variation in the fuel injection amount Gf at the start can be suppressed even if there is a manufacturing error, and the target air-fuel ratio at the start can be obtained. Thereby, the discharge of unburned HC at the time of starting can be further suppressed.

  In the period from the start of cranking to the completion of engine start, the sensitivity of the air-fuel ratio to the HC concentration at the engine outlet is large, and the HC concentration at the engine outlet deteriorates due to the variation in the air-fuel ratio from the target air-fuel ratio. According to the present embodiment (the invention described in claim 2), the start time is a period from the start of cranking to the completion of engine start (see step 32 in FIG. 12, FIG. 10). The sensitivity of the air-fuel ratio with respect to the HC concentration at the outlet is large, and it becomes possible to suppress the variation in the air-fuel ratio from the target air-fuel ratio in the period from the start of cranking to the completion of engine start, and the discharge of unburned HC Can be suppressed.

According to the present embodiment (the invention described in claim 4 ), the differential pressure between the actual fuel pressure Pf and the in-cylinder pressure Pivc (predicted in-cylinder pressure) at the intake valve closing timing is the actual fuel pressure in the reference engine and the intake valve. In the case of an engine that is smaller than the pressure difference from the in-cylinder pressure Pivc (predicted in-cylinder pressure) at the closing timing, the starting fuel injection pulse width T3 is corrected to the increase side (see FIG. 8B), so the actual fuel pressure The differential pressure between Pf and the in-cylinder pressure Pivc (predicted in-cylinder pressure) at the intake valve closing timing is the differential pressure between the actual fuel pressure in the reference engine and the in-cylinder pressure Pivc (predicted in-cylinder pressure) at the intake valve closing timing. In the case of a smaller engine, variation in the fuel injection amount Gf at the time of start-up can be suppressed, and the target air-fuel ratio at the time of start can be obtained.

According to this embodiment (the invention described in claim 5 ), the differential pressure between the actual fuel pressure Pf and the in-cylinder pressure Pivc (predicted in-cylinder pressure) at the intake valve closing timing is the actual fuel pressure in the reference engine and the intake valve. In the case of an engine having a pressure difference greater than the in-cylinder pressure Pivc (predicted in-cylinder pressure) at the closing timing, the start-time fuel injection pulse width T3 is corrected to the decrease side (see FIG. 8B), so the actual fuel pressure The differential pressure between Pf and the in-cylinder pressure Pivc (predicted in-cylinder pressure) at the intake valve closing timing is the differential pressure between the actual fuel pressure in the reference engine and the in-cylinder pressure Pivc (predicted in-cylinder pressure) at the intake valve closing timing. In the case of a larger engine, it is possible to suppress a variation in the fuel injection amount at the time of start-up, and to obtain a target air-fuel ratio at the time of start-up.

  Finally, when the engine is cold started and the idling state is maintained without depressing the accelerator pedal, the throttle opening may vibrate slightly. In this case, the current control is shown by the one-dot chain line in FIG. As described above, it has been found that the actual air-fuel ratio fluctuates greatly periodically on the basis of the target air-fuel ratio at the start, due to the minute vibration of the throttle opening. Even in such a case, the present invention is effective. That is, as shown by the solid line in FIG. 16, it can be seen that according to the present invention, the amplitude of the periodic fluctuation of the actual air-fuel ratio can be made smaller than in the current control.

  In the embodiment, the case where the present invention is applied to the start-time fuel injection pulse width T3 has been described. However, the present invention is not limited thereto, and the normal-time fuel injection pulse width used during retarded stratified combustion or the fuel injection during retarded stratified combustion The present invention can be applied to the time.

  12. The function of the fuel injection pulse width calculation means at start is in steps 32 and 34 to 36 of FIG. 12, the function of the signal output means is in step 40 of FIG. 12, and the function of the injection pulse width / injection timing correction means is This is accomplished by steps 38 and 39 in FIG.

1 is a schematic configuration diagram of a start-up fuel injection control device for an engine according to a first embodiment of the present invention. FIG. 6 is a timing chart showing changes in engine speed, combustion switching flag, throttle opening, collector pressure, ignition timing, and catalyst temperature when an idling state is maintained from a cold start of the engine. The characteristic view which shows the change of the engine speed from cranking start. The characteristic view which shows the in-cylinder pressure waveform at the time of motoring. The characteristic view showing the relationship between an air fuel ratio and HC density | concentration of an engine exit. The characteristic view which shows the change of the collector pressure before and after the intake valve closing timing. The characteristic view for demonstrating correction | amendment of the fuel injection pulse width at the time of starting. The characteristic view of an injection pulse width correction coefficient. The characteristic view for demonstrating correction | amendment of the fuel injection pulse width at the time of starting. The flowchart for demonstrating the setting of a start completion flag. The flowchart for demonstrating the setting of a combustion switching flag. The flowchart for demonstrating calculation of ignition timing, a fuel-injection pulse width, and the setting of fuel-injection time. The characteristic view for demonstrating correction | amendment of the fuel injection timing at the time of starting. The characteristic diagram of the injection timing correction amount. FIG. 3 is a stroke diagram for explaining a unit of fuel injection timing at start-up. The timing chart which shows the change of an actual air fuel ratio when the throttle opening vibrates slightly in the case where the idling state is maintained without depressing the accelerator pedal from the engine cold start.

Explanation of symbols

13 Fuel Injection Valve 21 Engine Controller 28 Pressure Sensor (Intake Pressure Detection Means)
29 Fuel pressure sensor (Fuel pressure detection means)

Claims (6)

A fuel injection valve for directly injecting a fuel amount corresponding to the valve opening pulse width and the fuel pressure into the combustion chamber;
Starting fuel injection pulse width calculating means for calculating a starting fuel injection pulse width so as to obtain a target air-fuel ratio at starting;
Start fuel injection timing setting means for setting the start fuel injection timing;
In an engine start time fuel injection control device comprising: the set start time fuel injection timing and the signal output means for outputting the calculated start time fuel injection pulse width signal to the fuel injection valve;
Intake pressure detection means for detecting intake pressure;
Fuel pressure detecting means for detecting the fuel pressure;
In-cylinder pressure predicting means for predicting the in-cylinder pressure at the intake valve closing timing from the intake pressure detected by the intake pressure detecting means at the start,
At least one of the calculated start time fuel injection pulse width and the set start time fuel injection timing based on the differential pressure between the actual fuel pressure detected by the fuel pressure detecting means at the start time and the predicted in-cylinder pressure. One with and a injection pulse width · injection timing correction means for correcting,
With crank angle sensor
The in-cylinder pressure predicting means equally divides a predetermined crank angle range centered on the intake valve closing timing into a plurality of parts, and an actual crank angle detected by the crank angle sensor at the time of starting is divided into the plurality of parts. Sampling the intake pressure detected by the intake pressure detection means at a timing that coincides with each crank angle, and predicting the minimum data among the plurality of sampled sampling data as the in-cylinder pressure at the intake valve closing timing A fuel injection control device for starting an engine characterized by the above.   2. The engine start-time fuel injection control device according to claim 1, wherein the start time is a period from start of cranking to completion of engine start. Start time fuel injection control device for an engine according to claim 1 which comprises using as the cylinder pressure the predicted at the start of the next during operation the cylinder pressure at the current operating intake valve closing timing predicted at the start of the time .   In the case of an engine in which the differential pressure is smaller than the differential pressure between the detected actual fuel pressure and the predicted in-cylinder pressure in a reference engine, the calculated start-time fuel injection pulse width is corrected to the increase side or 2. The engine start time fuel injection control device according to claim 1, wherein the set fuel injection timing is corrected to an advance side.   In the case of an engine in which the differential pressure is greater than the differential pressure between the detected actual fuel pressure and the predicted in-cylinder pressure in a reference engine, The engine fuel injection control device at the start of the engine according to claim 1, wherein the set fuel injection timing is corrected to the retard side.   2. The engine start fuel injection control device according to claim 1, wherein the start fuel injection pulse width is calculated based on an engine coolant temperature, a cranking rotation speed, and a cranking time.

Images