JP2019105240A - Control device for internal combustion engine - Google Patents

Abstract

To provide a control device for an internal combustion engine capable of suppressing lowering of speed after start.SOLUTION: A control device for an internal combustion engine includes: a negative pressure acquisition section for acquiring negative pressure in a cylinder of the internal combustion engine; and an injection control section for controlling a first fuel injection valve for injecting fuel into the cylinder of the internal combustion engine and a second fuel injection valve for injecting fuel to an intake passage of the internal combustion engine on the basis of the negative pressure. At start of the internal combustion engine, the injection control section injects fuel twice by using the first fuel injection valve in an intake stroke of the internal combustion engine when the negative pressure of the internal combustion engine is less than a threshold value, and injects fuel by using the second fuel injection valve when the negative pressure is equal to or higher than the threshold value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a control device for an internal combustion engine.

  An internal combustion engine is known that includes a fuel injection valve that injects a fuel into an intake path and a fuel injection valve that injects a fuel into a cylinder (Patent Document 1). For example, direct injection (DI) is performed when the internal combustion engine is started, and then port injection (PFI) to the intake path is performed.

Unexamined-Japanese-Patent No. 2010-43602

  In the idling stop, so-called start and stop (S & S) function, the amount of air entering the cylinder of the internal combustion engine may be large, and the negative pressure in the cylinder may be insufficient. In this case, the port-injected fuel is less likely to enter the combustion chamber, and the rotational speed of the internal combustion engine is reduced. The amount of injection may be increased to increase the number of revolutions, but the emissions will deteriorate. Then, it aims at providing the control device of the internal combustion engine which can control the fall of the number of rotations after starting.

  The above object is to provide a negative pressure acquisition unit for acquiring a negative pressure in a cylinder of an internal combustion engine, a first fuel injection valve for injecting fuel into the cylinder of the internal combustion engine based on the negative pressure, and the internal combustion engine An injection control unit that controls a second fuel injection valve that injects fuel into an intake path, wherein the injection control unit is configured to set the negative pressure of the internal combustion engine to less than a threshold when starting the internal combustion engine In the internal combustion engine, the fuel injection is performed twice by the first fuel injection valve in the intake stroke of the internal combustion engine, and the fuel injection by the second fuel injection valve is performed when the negative pressure is equal to or more than the threshold value. It can be achieved by the controller.

  It is possible to provide a control device of an internal combustion engine capable of suppressing a decrease in rotational speed after start.

FIG. 1 is a schematic view illustrating an internal combustion engine. Fig.2 (a) is a figure which shows injection timing. FIG. 2 (b) is a time chart. FIG. 3 is a flowchart illustrating control executed by the ECU. FIG. 4A and FIG. 4B illustrate the fuel injection amount.

(Embodiment)
Hereinafter, a control device of an internal combustion engine of the present embodiment will be described with reference to the drawings. FIG. 1 is a schematic view illustrating an internal combustion engine 100. As shown in FIG. The internal combustion engine 100 is, for example, a gasoline engine mounted on an automobile or the like. As shown in FIG. 1, the internal combustion engine 100 includes an engine body 10 and an ECU (Electronic Control Unit) 40.

  The engine body 10 has a cylinder head 11 and a cylinder block 12. Inside the cylinder block 12, a piston 14, a connecting rod 15 and a crankshaft 16 are accommodated. A combustion chamber 13 is formed inside the engine body 10 by the cylinder head 11, the cylinder block 12 and the piston 14. The piston 14 is connected to the crankshaft 16 by a connecting rod 15. A rotation speed sensor 17 provided in the cylinder block 12 detects the rotation speed of the engine. The cylinder head 11 is provided with a fuel injection valve 30 (first fuel injection valve) for supplying fuel (in-cylinder injection) to the combustion chamber 13.

  The cylinder head 11 is provided with a spark plug 18, an intake valve 26, and an exhaust valve 27, and an intake path 20 and an exhaust path 21 are connected. The intake passage 20 includes an intake port 20a and an intake pipe 20b. The upstream intake pipe 20b and the downstream intake port 20a are connected. The exhaust path 21 includes an exhaust port 21a and an exhaust pipe 21b. The downstream exhaust pipe 21b and the upstream exhaust port 21a are connected. By rotation of a cam shaft (not shown), the intake valve 26 and the exhaust valve 27 move, and the intake port 20a and the exhaust port 21a open and close.

  An air cleaner 22, an air flow meter 23, a throttle valve 24, and a fuel injection valve 32 (second fuel injection valve) are provided in the intake passage 20 from the upstream side to the downstream side. The air cleaner 22 removes dust and the like from the air flowing from the outside. The air flow meter 23 acquires an intake air amount. The throttle valve 24 is driven by, for example, an actuator (not shown) to adjust the amount of intake air. As the opening degree increases, the amount of intake air increases and the negative pressure in the cylinder decreases. As the degree of opening decreases, the amount of intake air decreases and the negative pressure in the cylinder increases.

  By the intake valve 26 opening, air is introduced from the intake passage 20 into the combustion chamber 13. The fuel and air injected from the fuel injection valve 30 or 32 form an air-fuel mixture, which is compressed by the piston 14 and the spark plug 18 ignites the air-fuel mixture. The ignition causes the piston 14 to reciprocate up and down in the combustion chamber 13, and the crankshaft 16 rotates. Exhaust gas after combustion is discharged from the exhaust passage 21.

  The exhaust path 21 is provided with a catalyst 25 and an air-fuel ratio sensor 28. The catalyst 25 is, for example, a three-way catalyst, contains a catalyst metal such as platinum (Pt), palladium (Pd), rhodium (Rh), etc., has oxygen storage capacity, and purifies NOx, HC and CO. The air-fuel ratio sensor 28 detects an air-fuel ratio.

  The ECU 40 (Electronic Control Unit) includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and a storage device, and executes a program stored in the ROM or the storage device. Perform various controls. The ECU 40 stops the fuel injection when the stop condition is satisfied, stops the operation of the internal combustion engine 100, and starts the internal combustion engine 100 when the start condition is satisfied (S & S function). For example, the stop condition is that the speed of the vehicle is less than the threshold value, and the start condition is that the brake pedal is released. The eco-run ECU may control the S & S function of the internal combustion engine 100 in addition to the ECU 40.

  The ECU 40 is electrically connected to the rotation speed sensor 17, the spark plug 18, the air flow meter 23, the throttle valve 24, the air-fuel ratio sensor 28, and the fuel injection valves 30 and 32 described above. The ECU 40 acquires the rotational speed from the rotational speed sensor 17, the intake air amount from the air flow meter 23, the opening degree from the throttle valve 24, and the air-fuel ratio from the air-fuel ratio sensor 28, respectively. Further, the ECU 40 controls the ignition timing of the spark plug 18, the opening degree of the throttle valve 24, the injection amount of the fuel injection valves 30 and 32, and the number of injections. The ECU 40 functions as a negative pressure acquisition unit that acquires the negative pressure in the cylinder from the intake air amount, the opening degree of the throttle valve 24, and the like, and an injection control unit that controls the fuel injection valves 30 and 32.

  Fig.2 (a) is a figure which shows injection timing. Of the two in-cylinder injections, DI1 represents the first injection, and DI2 represents the second injection. While the piston 14 moves from TDC (Top Dead Center) to BDC (Bottom Dead Center), DI1 and DI2 are performed, and while the piston 14 moves from BDC to TDC, IVC (Intake) Valve Close, the closing timing of the intake valve 26) is located. That is, two in-cylinder injections are performed in the intake stroke.

  Of the two in-cylinder injections, the fuel injected by DI1 is discharged together with the air blown back from the combustion chamber 13 and adheres to the intake port 20a and the like. Since the fuel injected by DI2 contributes to the combustion, the reduction of the rotational speed is suppressed.

  FIG. 2 (b) is a time chart. From top to bottom, the engine speed, increase after start, injection ratio between PFI and DI, adhesion correction amount, air-fuel ratio, and ignition timing are shown. The amount of increase after start and the adhesion correction amount are amounts for correcting the fuel adhering to the intake port 20 a and the like. The solid line represents this embodiment, and the broken line represents a comparative example. At time t0, the internal combustion engine 100 starts (S & S start).

  As shown in the third stage of FIG. 2 (b), the fuel injection ratio is switched between PFI and DI, with DI on the lower side being 100% and PFI on the upper side being 100%. DI is performed immediately after startup in the comparative example and the embodiment.

  In the comparative example, DI is switched to PFI at time t1. However, after S & S start, the amount of air entering the cylinder is large, and the negative pressure in the cylinder is low. For this reason, the port-injected fuel does not easily flow into the cylinder, and the amount of fuel attached to the intake port 20a increases. As a result, the fuel contributing to the combustion is reduced and the engine speed is reduced. In particular, when the fuel atomization is poor, the rotational speed is greatly reduced. For example, as shown in the first stage of FIG. 2 (b), the rotational speed of the engine decreases from R1 to about R2. In order to correct the amount attached to the intake port 20a and to increase the rotational speed, for example, the increase amount after start and the amount of adhesion correction may be increased as compared with the example of FIG. However, the fuel injection amount increases and the emissions deteriorate.

  On the other hand, in the embodiment, the period of DI is longer than that of the comparative example, and switching from DI to PFI is performed at time t2 after time t1. In the period from t1 to t2, two in-cylinder injections of DI1 and DI2 shown in FIG. 2A are performed. Therefore, the amount of fuel entering the cylinder increases, and the fuel injected mainly by DI2 contributes to the combustion. A homogeneous mixture of fuel and air is formed, and combustion suppresses a decrease in rotational speed, and the rotational speed is maintained at about R1. Since it is not necessary to increase the amount after start-up and the adhesion correction amount, the deterioration of the emission is also suppressed.

  The period of DI is, for example, a period of time in which the negative pressure in the cylinder is higher than the threshold. The negative pressure in the cylinder increases during the period of DI, and shifts to PFI. That is, DI is performed if the negative pressure is less than the threshold, and PFI is performed if the negative pressure is equal to or greater than the threshold. As a result, the decrease in rotational speed is suppressed, and port-injected fuel can easily enter the cylinder. Further, since the fuel injected in DI1 adheres to the intake port 20a, the adhesion of the fuel injected in PFI to the intake port 20a is suppressed. Therefore, according to the present embodiment, the adhesion correction amount can be reduced, and the deterioration of the emission can be suppressed.

  FIG. 3 is a flowchart illustrating the control that the ECU 40 executes. First, the ECU 40 acquires, for example, the opening degree of the throttle valve 24 and acquires the negative pressure of the cylinder of the engine body 10 based on the opening degree. The ECU 40 sets the number of in-cylinder injections (DI) based on the negative pressure or the like (step S10). For example, the number of times is determined such that the period of negative pressure is less than the threshold is the period of DI, and the negative pressure becomes equal to or greater than the threshold and the PFI period thereafter. The ECU 40 executes in-cylinder injection (DI) using the fuel injection valve 30 (step S12). At this time, two in-cylinder injections as shown in FIG. 2A are performed. After completion of DI a predetermined number of times, the ECU 40 switches from DI to port injection (PFI) (step S14). Thereafter, control ends.

  As described above, according to the present embodiment, the ECU 40 performs two in-cylinder injections by the fuel injection valve 30 when the negative pressure is less than the threshold value. As a result, fuel is supplied into the cylinder, and a decrease in the rotational speed of the internal combustion engine 100 is suppressed. Since it is not necessary to increase the increase after start-up to increase the rotational speed, the fuel injection amount is suppressed, and the deterioration of the emission is suppressed.

  Of the two in-cylinder injections, the fuel injected by DI1 adheres to the intake port 20a. Therefore, at the time of switching to the PFI, the fuel is already attached to the intake port 20a. Therefore, of the fuel injected by PFI, the amount of adhesion to the intake port 20a is reduced, and the amount of adhesion correction can be reduced. As a result, the fuel injection amount is suppressed, and the deterioration of the emission is suppressed. The negative pressure in the cylinder reaches a threshold or more while the set number of DIs is performed. Thereafter, in order to carry out PFI, the fuel injected from the fuel injection valve 32 tends to enter the cylinder. Therefore, good combustion is possible after PFI transition.

  In the example shown in FIG. 2 (a), DI1 and DI2 are both intake strokes. DI1 is carried out in the intake stroke in order to blow fuel back to and adhere to the intake port 20a. On the other hand, DI2 may be performed at a time other than the intake stroke, and may be performed, for example, while the piston 14 rises from BDC to TDC (compression step). The injection timing of DI1 and DI2 can be determined according to the temperature of the cooling water, the number of injections from the start of the injection, and the like. The fuel injection amount in DI1 and the fuel injection amount in DI2 may be the same, or one may be larger than the other.

  The ECU 40 can control the fuel injection amount by the lift amount of the needle of the fuel injection valve 30 or the like. Since it is difficult to control the fuel injection amount when it is difficult to control the lift amount accurately, it is preferable not to perform the fuel injection. FIG. 4A and FIG. 4B illustrate the fuel injection amount. The vertical axis is the fuel injection amount. In the figure, X1 is a region where the needle fully lifts, and X2 is a region where lift control is difficult because needle bounce occurs. X3 is a partial lift region where the needle does not reach full lift, and X4 is a region where the needle lift amount is small and injection is difficult. X1 and X3 are regions where fuel injection is possible, and X2 and X4 are regions where fuel injection is not performed.

  Black circles shown in FIG. 4 (a) indicate the injection amount of each of the two in-cylinder injections (injection amounts at each of DI1 and DI2), and white circles indicate the injection amounts after changing to one in-cylinder injection. . As shown in FIG. 4A, when the injection amount reaches, for example, X2, the ECU 40 stops two in-cylinder injections and switches to one in-cylinder injection. As a result, the amount of injection increases and fuel injection becomes possible. Moreover, it is preferable not to shift to injection twice again after shifting to one-time injection. The reason is that combustion becomes unstable and the deterioration of drivability and emission is suppressed.

  The black circles shown in FIG. 4B indicate the injection amount of the first (DI1) of the two in-cylinder injections, and the white circles indicate the injection amount of the second (DI2). The injection amount of DI1 is located at X1, and the injection amount of DI2 is located at X3. That is, in-cylinder injection is performed also in the partial lift region. Thus, two in-cylinder injections can be continued and single injection can be avoided.

  Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to the specific embodiments, and various modifications may be made within the scope of the subject matter of the present invention described in the claims. Changes are possible.

DESCRIPTION OF SYMBOLS 10 engine main body 11 cylinder head 12 cylinder block 14 piston 15 connecting rod 16 crankshaft 17 rotation speed sensor 18 spark plug 20 intake path 20a intake port 20b intake pipe 21 exhaust path 21a exhaust port 21b exhaust pipe 22 air cleaner 23 air flow meter 24 throttle valve 25 Catalyst 26 intake valve 27 exhaust valve 28 air-fuel ratio sensor 30, 32 fuel injection valve 40 ECU
100 Internal combustion engine

Claims (1)

A negative pressure acquisition unit for acquiring negative pressure in a cylinder of an internal combustion engine;
A first fuel injection valve that injects fuel into a cylinder of the internal combustion engine based on the negative pressure, and an injection control unit that controls a second fuel injection valve that injects fuel into the intake passage of the internal combustion engine Equipped
The injection control unit performs two fuel injections by the first fuel injection valve in an intake stroke of the internal combustion engine when the negative pressure of the internal combustion engine is less than a threshold when starting the internal combustion engine. The control device of an internal combustion engine which carries out fuel injection by the second fuel injection valve when the negative pressure is equal to or higher than the threshold.

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