JP2017115661A - Injection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection control device for a port injection valve, capable of suppressing the adhesion of fuel onto an intake port and a cylinder wall surface.SOLUTION: An injection control device (10) is applied for an internal combustion engine (17) which includes a combustion chamber (42) for combusting air-fuel mixed air, a port injection valve (33) for injecting fuel toward the intake port communicated with the combustion chamber, and an intake valve (18) provided in the intake port for, when opened, allowing air to flow into the combustion chamber. The injection control device sets a start timing and a finish timing for fuel injection by the port injection valve so that, during a time from when the intake valve starts its opening to when the velocity of air flowing with the intake vale opened becomes higher than a predetermined velocity, low-velocity air flow injection can be performed to inject more fuel than a predetermined rate to all fuel injected by the port injection valve in one cycle.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an injection control device that controls fuel injection of a port injection valve.

  In general, by injecting fuel into an intake port with an injector (hereinafter referred to as “port injection”), it is possible to achieve a highly homogeneous combustion by sufficiently mixing air and fuel. As such a port injection type internal combustion engine, for example, there is a technique disclosed in Patent Document 1.

  The internal combustion engine disclosed in Patent Document 1 is provided with two in-cylinder injection valves that directly inject into a cylinder and the above-described port injection valve, of which fuel injection by the in-cylinder injection valve is an intake stroke, Fuel injection by the port injection valve is performed in the exhaust stroke. Thereby, the spray injected from the in-cylinder injection valve can collide with the spray injected from the port injection valve, and the port uses the airflow energy generated when fuel is injected by the in-cylinder injection valve. Atomization of the spray sprayed by spraying can be promoted.

Japanese Patent Laying-Open No. 2015-140761

  However, in the technique disclosed in Patent Document 1, the fuel injected by the port injection valve may come into contact with the intake valve that is closed, and the fuel may adhere to the intake valve. In this case, the fuel flowing into the combustion chamber is reduced, and the output of the internal combustion engine may be reduced.

  On the other hand, if fuel injection is performed by the port injection valve while the intake valve is open (when fuel injection is performed by the port injection valve during the intake stroke), the fuel is injected into the high-speed airflow flowing into the intake pipe. There is a risk that the fuel spray may collide with the wall surface in the cylinder. In this case, fuel droplets may adhere to the cylinder wall surface, which may cause a reduction in the output of the internal combustion engine and a deterioration in emissions.

  The present invention has been made to solve the above-mentioned problems, and a main object thereof is to provide an injection control device for a port injection valve capable of suppressing the adhesion of fuel to an intake port and a cylinder wall surface. It is in.

  The present invention provides a combustion chamber for combusting a mixture of air and fuel, a port injection valve for injecting fuel toward an intake port communicating with the combustion chamber, and the combustion provided by being opened at the intake port. An injection control device applied to an internal combustion engine including an intake valve that allows air to flow into a room, wherein the injection control device has an airflow velocity due to opening of the intake valve after the intake valve starts to open. By the port injection valve, a low-speed air flow injection is performed in which more fuel is injected than a predetermined ratio of the total fuel injected by the port injection valve in one combustion cycle until the speed becomes higher than the predetermined speed. A fuel injection start time and an end time are set.

  More fuel than the predetermined ratio of the total fuel injected by the port injection valve in one combustion cycle from when the intake valve starts to open until the speed of the airflow by opening the intake valve becomes higher than the predetermined speed Is set so that the start timing and end timing of fuel injection by the port injection valve are set. As a result, the ratio of the fuel injected before the start of opening of the intake valve becomes smaller than the ratio obtained by subtracting a predetermined ratio from the whole, and the fuel is prevented from adhering to the intake valve being closed. I can do things. In addition, since more than a predetermined ratio of the fuel injected by the port injection valve flows into the combustion chamber without getting on the airflow at a speed higher than the predetermined speed, it is possible to suppress the fuel from adhering to the wall surface of the combustion chamber. I can do it.

1 is a schematic diagram illustrating a system configuration of a vehicle according to an embodiment. It is the timing chart which showed the several parameter which fluctuates by implementing exhaust stroke injection or low-speed airflow injection. It is a figure which shows the state of the spray of the fuel at the time of the exhaust stroke injection in the time t1-3 shown in FIG. It is the figure which showed typically the conventional fuel-injection control which implements fuel injection during intake valve opening. It is a figure which shows the period when the fuel injected from the injector reaches | attains an intake valve. It is a figure which shows the difference between exhaust stroke injection and low-speed airflow injection. It is a control flowchart implemented by ECU which concerns on this embodiment. It is a subroutine process of step S110 described in FIG. It is a figure which shows the setting method of the injection start time and the injection end time when the opening / closing timing of the intake valve is advanced. It is a figure which shows the state of the spray of the fuel at the time of the low speed air current injection in the time t5-t7 described in FIG.

  FIG. 1 is an explanatory diagram showing a system configuration of an internal combustion engine 17 to which the ECU 10 according to the present embodiment is applied. The internal combustion engine 17 is a four-cycle engine that sequentially repeats an exhaust stroke, an intake stroke, a compression stroke, and an expansion stroke. The internal combustion engine 17 is a multi-cylinder engine having a plurality of cylinders. FIG. 1 illustrates only one cylinder among the plurality of cylinders included in the internal combustion engine 17.

  A cylinder 43 is formed in the cylinder block 41, and a piston 44 that reciprocates in the vertical direction with respect to the cylinder 43 is disposed in the cylinder 43. The piston 44 is connected to a crankshaft (not shown) via a connecting rod 45. A combustion chamber 42 defined by a cylinder 43 and a cylinder head 38 is provided above the piston 44, and an intake port 33a and an exhaust port 34a are connected to the combustion chamber 42, respectively. A spark plug 35 is disposed on the cylinder head 38. The spark plug 35 is ignited by an ignition high voltage supplied from an igniter (not shown).

  An intake pipe 31 that sucks intake air into the combustion chamber 42 is connected to the intake port 33a, and an exhaust pipe 34 that discharges exhaust gas from the cylinder is connected to the exhaust port 34a. The intake pipe 31 is supplied with an air flow meter 49 that detects the intake air amount, a throttle valve 32 that is electronically controlled based on an operation amount of an accelerator pedal (not shown), and a high-pressure fuel from a fuel supply system. And an electromagnetically driven injector 33 (corresponding to a port injection valve).

  The injector 33 is a port injection type fuel injection valve that injects fuel toward the intake port 33a when energized. The fuel in the fuel tank 50 is pressurized by the fuel pump 51 to the injector 33 and supplied through the fuel pipe 52. A fuel pressure sensor 53 for detecting the pressure of fuel supplied under pressure to the injector 33 (hereinafter referred to as “fuel pressure”) is provided in the middle of the fuel pipe 52. Note that the amount of fuel discharged by the fuel pump 51 is variable, so that the fuel pressure setting can be changed.

  The intake port 33a is provided with an intake valve (corresponding to an intake valve) 18 that opens and closes the port. Two intake ports 33a are provided in one cylinder, and an intake valve 18 is provided in each intake port 33a. On the other hand, the exhaust pipe 34 is provided with an exhaust purification device 39, and the exhaust port 34a is provided with an exhaust valve (corresponding to an exhaust valve) 19 for opening and closing the port with respect to the cylinder. Two exhaust ports 34a are provided for each cylinder, and an exhaust valve 19 is provided for each exhaust port 34a.

  The opening degree of the throttle valve 32 is detected by a throttle opening degree sensor 23, and the throttle opening degree sensor 23 also detects the fully closed state of the throttle. The throttle opening is represented by an angle with respect to the direction perpendicular to the intake pipe 31. That is, 0 degrees indicates fully closed and 90 degrees indicates fully open.

  The exhaust purification device 39 includes an exhaust purification catalyst inside, and purifies the exhaust by oxidizing and / or reducing the exhaust discharged through the exhaust pipe 34 after the combustion of the fuel. In addition, when the catalyst temperature is lower than an appropriate temperature, the exhaust purification catalyst has a reduced exhaust oxidation efficiency and / or reduction efficiency. That is, when the catalyst temperature is lower than the appropriate temperature, exhaust gas purification is not sufficiently performed.

  An intake side camshaft 36 for opening and closing the intake valve 18 at a predetermined timing and an exhaust side camshaft 37 for opening and closing the exhaust valve 19 at a predetermined timing are connected to a crankshaft via a timing belt (not shown). Has been. The crankshaft is provided with a crank angle sensor 22 that detects a rotational position and a rotational speed of the crankshaft. The cylinder block 41 is provided with a water temperature sensor 48 for detecting the cooling water temperature.

  The intake camshaft 36 is provided with an intake cam angle sensor 20 that detects the cam angle of the intake camshaft 36, and the exhaust camshaft 37 detects the cam angle of the exhaust camshaft 37. An exhaust side cam angle sensor 21 is provided.

  The intake side camshaft 36 is provided with an intake side variable valve mechanism (intake side VCT) 46, and the exhaust side camshaft 37 is provided with an exhaust side variable valve mechanism (exhaust side VCT) 47. The intake-side VCT 46 (corresponding to the intake valve timing variable mechanism) and the exhaust-side VCT 47 respectively change the relative rotational phase between the intake-side cam shaft 36, the exhaust-side cam shaft 37, and the crankshaft. It is changed by adjusting the center phase of the exhaust side camshaft 37. The intake side camshaft 36 and the exhaust side camshaft 37 are rotated to the retard side or the advance side with respect to the crankshaft according to the control amounts of the intake side VCT 46 and the exhaust side VCT 47, and the intake side is adjusted in accordance with the operation. The opening / closing timing of the valve 18 and the exhaust valve 19 is changed to the retard side or the advance side.

  In the control system of the internal combustion engine 17 having the above-described configuration, the ECU 10 inputs detection signals of the various sensors described above, and based on the detection signals, the intake air amount, the throttle opening, the rotation speed of the crankshaft, the engine water temperature, the fuel pressure. The operating state parameters of the internal combustion engine 17 such as are acquired. Further, the ECU 10 controls the fuel injection by the injector 33, the opening degree control of the throttle valve 32, the ignition timing control by the spark plug 35, the intake side based on the operating state parameters of the various internal combustion engines 17 acquired as described above. Control of the opening / closing timing of the intake valve 18 by the VCT 46, control of the opening / closing timing of the exhaust valve 19 by the exhaust side VCT 47, and the like are performed. Therefore, in the present embodiment, the ECU 10 corresponds to an injection control device.

  In the conventional ECU 10, as shown in FIG. 2, most of the fuel injected by the injector 33 in one combustion cycle is injected in the exhaust stroke of the internal combustion engine 17 (see time t1-t4). It was carried out. When exhaust stroke injection is performed, as shown in FIG. 3, at the timing when the intake valve 18 opens (see time t3), the spray of fuel that has already been injected contacts the intake valve 18 that is closed. Yes. For this reason, fuel may adhere to the intake valve 18. In this case, the fuel flowing into the combustion chamber 42 is reduced, and the output of the internal combustion engine 17 may be reduced.

  In consideration of the above problems, as shown in FIG. 4, the injection control is performed so that the fuel is injected by the injector 33 while the intake valve 18 is opened (the fuel is injected by the injector 33 during the intake stroke). There are conventional techniques to implement. When this control is performed, the fuel injection period by the injector 33 is set so as to include the case where the intake valve 18 reaches the maximum lift amount. As shown in FIG. 2, as the intake valve 18 approaches the maximum lift amount, the velocity of the airflow in the intake port 33a increases. Therefore, the fuel spray injected by the injector 33 is put on an air flow having a high flow velocity, and the fuel spray may collide with the wall surface of the combustion chamber 42. In this case, the fuel droplets adhere to the wall surface of the combustion chamber 42, which may cause a decrease in output of the internal combustion engine 17 and a deterioration in emissions.

  Each of the above-described problems may become more serious particularly in a high load region where the fuel injection amount increases. Therefore, in the present embodiment, when the load of the internal combustion engine 17 is in a high load region, fuel injection control by the injector 33 (hereinafter referred to as the present invention) so as to suppress the adhesion of fuel to the intake port 33a and the combustion chamber 42 wall surface. The control is referred to as low-speed airflow injection control).

  Specifically, as shown in FIG. 5, after the intake valve 18 starts to open (see time t <b> 7: corresponding to time t <b> 3 shown in FIG. 2) By the time the internal air velocity is called a predetermined speed (see time t9), more fuel is injected than a predetermined ratio of the total fuel injected by the injector 33 (set to 50% in this embodiment). Thus, the injection start timing of fuel injection by the injector 33 is set (see time t5). The predetermined speed is a fixed value at which the in-port airflow speed is set lower than the maximum speed value. In addition, fuel injection by the injector 33 is started such that more than 70% of the total fuel injected by the injector 33 flows into the combustion chamber 42 from the intake port 33a after the intake valve 18 starts to open. Set the time.

  On the other hand, the injection end timing is set so that the fuel injection ends when the in-port airflow velocity that rises by opening the intake valve 18 reaches a predetermined speed (see time t8).

  When the load of the internal combustion engine 17 is low, it is assumed that the fuel injection amount injected from the injector 33 is small, and the amount of fuel adhering to the intake valve 18 and the combustion chamber 42 wall surface is small even in the exhaust stroke injection. Therefore, exhaust stroke injection is performed in such a low load state. Specifically, as shown in FIG. 6, the fuel injection period by the injector 33 is longer than the injection period set when the low-speed air flow injection is performed and before the intake valve 18 is opened. The injection end time is set so that the injection ends. Further, as the injection period is set longer, the injection rate is controlled to be lower than the injection rate set when the low-speed air flow injection is performed so that the total injection amount of the fuel injected by the injector 33 in one combustion cycle does not increase.

  Below, the control content of the fuel injection illustrated in FIG. 7 performed by the ECU 10 according to the present embodiment will be described.

  First, in step S100, it is determined whether or not the current engine load (for example, accelerator opening) is included in a high load region that is higher than a predetermined load. When it is determined that the current engine load is lower than the predetermined load and is not included in the high load region (S100: NO), the process proceeds to step S120, exhaust stroke injection control is performed, and this control is terminated. To do. When it is determined that the current engine load is included in the high load region higher than the predetermined load (S100: YES), the process proceeds to step S110, the low speed air flow injection control is performed, and this control is terminated.

  Next, low speed air flow injection control performed by the ECU 10 will be described with reference to FIG. This control is a subroutine process corresponding to step S110 described in FIG.

  In step S200, the crankshaft rotational speed detected by the crank angle sensor 22, the intake air amount detected by the air flow meter 49, the engine water temperature detected by the water temperature sensor 48, the fuel pressure detected by the fuel pressure sensor 53, etc. Get state parameters. In step S210, the required injection amount to be injected by the injector 33 is calculated based on the acquired operation state parameter.

  In step S220, the opening / closing timing of the intake valve 18 is detected based on the control amount of the intake side VCT 46. In step S230, the injection end timing of the fuel injection performed by the injector 33 is set based on the closing timing of the intake valve 18. For example, in the case where the closing timing of the intake valve 18 is advanced, if the intake valve 18 is closed early, the fuel spray being injected by the injector 33 may collide with the closed intake valve 18. . For this reason, if the closing timing of the intake valve 18 detected in step S220 is advanced than the expected closing timing, the intake valve 18 detected as shown in FIG. 9 is closed. The injection end timing is advanced based on the difference between the timing and the expected closing timing. If the detected closing timing of the intake valve 18 is controlled to be retarded from the assumed closing timing, the difference between the detected closing timing of the intake valve 18 and the assumed closing timing is calculated. Based on this, the injection end timing is retarded.

  Similarly, in step S240, the injection start timing of the fuel injection performed by the injector 33 is set based on the opening timing of the intake valve 18. For example, when the opening timing of the intake valve 18 is controlled to advance, when the intake valve 18 is opened early, the spray of fuel injected by the injector 33 rides on the airflow that flows in by opening the intake valve 18. As a result, the fuel may collide with the wall surface in the combustion chamber 42. Therefore, when the opening timing of the intake valve 18 detected in step S220 is advanced than the expected opening timing, the opening timing of the intake valve 18 detected as shown in FIG. The injection start timing is advanced based on the difference from the opening timing that is assumed. If the detected opening timing of the intake valve 18 is controlled to be retarded from the assumed opening timing, the difference between the detected opening timing of the intake valve 18 and the assumed opening timing is calculated. Based on this, the injection start timing is retarded.

  In step S250, an injection rate at which the required injection amount calculated in step S210 can be injected during the injection period set in steps S220 and S230 is calculated. And this control is complete | finished. The injection rate is controlled by adjusting the pressure of the fuel supplied to the injector 33, for example.

  With this configuration, the present embodiment has the following effects.

  In the low-speed air flow injection control, the injector 33 causes more than 70% of the total fuel injected by the injector 33 to flow into the combustion chamber 42 from the intake port 33a after the intake valve 18 starts to open. The fuel injection start time is set. Therefore, as shown in FIG. 10, at time t7 when the intake valve 18 opens (see FIG. 5), more than 70% of the total fuel injected by the injector 33 reaches the intake valve 18. Not done. Therefore, the amount of fuel that has contacted the intake valve 18 before the intake valve 18 is opened is less than 30% of the total fuel, and it is possible to effectively suppress the fuel from adhering to the intake valve 18. As a result, by suppressing the amount of fuel adhering to the intake valve 18 and the wall surface of the combustion chamber 42, the amount of fuel consumed for combustion in the combustion chamber 42 can be increased, and the output of the internal combustion engine 17 can be improved. Can do.

  -The injection end time is set so that the fuel injection by the injector 33 is ended when the speed of the airflow by opening the intake valve 18 reaches a predetermined speed. For this reason, it is possible to suppress the amount of fuel that rides on the airflow faster than the predetermined speed, and thus it is possible to suppress the amount of fuel that rides on the airflow and collides with the wall surface of the combustion chamber 42.

  The injection start timing and the injection end timing of the fuel injection by the injector 33 are set so that the low-speed airflow injection is performed in a state where the internal combustion engine 17 is at a high load. Thereby, the effect of reducing the amount of fuel adhering to the intake valve 18 and the wall surface in the combustion chamber 42 can be remarkably exhibited.

  When the opening timing of the intake valve 18 is advanced, the injection start timing is advanced based on the advance amount of the opening timing of the intake valve 18 so that the fuel is injected by the injector 33. It is possible to avoid that the airflow in the intake pipe 31 is already in a fast state.

  When the closing timing of the intake valve 18 is advanced, the injection end timing is advanced based on the advance amount of the closing timing of the intake valve 18 until the fuel injection by the injector 33 is completed. It is possible to keep the intake valve 18 open.

  When the load on the internal combustion engine 17 is low, exhaust stroke injection is performed in which all the fuel injected by the injector 33 in one combustion cycle is injected in the exhaust stroke of the internal combustion engine 17. Thereby, the period during which the fuel and air are mixed can be lengthened, and the homogeneity of the air-fuel mixture can be improved.

  The above embodiment can also be implemented with the following modifications.

  In the above embodiment, two intake ports 33 a are attached to one cylinder 43. With respect to this, this control may be performed by the internal combustion engine 17 in which one cylinder 43 is provided with one intake port 33a.

  In the above embodiment, the injector 33 is attached to the intake pipe 31. In this regard, in addition to the injector 33 being attached to the intake pipe 31, a direct injection injector for directly injecting fuel into the combustion chamber 42 may be separately provided. Even when this control is performed in such a dual-injection internal combustion engine, the same effects as those of the above embodiment can be obtained.

  In the above embodiment, when the load of the internal combustion engine 17 is included in the high load region higher than the predetermined load, the low speed air flow injection is performed. In this regard, low-speed airflow injection may be performed at any time regardless of the load level of the internal combustion engine 17.

  In the above embodiment, low-speed airflow injection is performed so that more than 70% of the total fuel injected by the injector 33 flows into the combustion chamber 42 from the intake port 33a after the intake valve 18 starts to open. The injection start time was set. In this regard, it is not always necessary to set so that more than 70% of the total fuel flows into the combustion chamber 42 from the intake port 33a after the intake valve 18 starts to open. For example, the injection start timing of the low-speed air flow injection may be set so that more than 60% of the total fuel flows into the combustion chamber 42 from the intake port 33a after the intake valve 18 starts to open.

  Alternatively, the injection start timing of the fuel injection by the injector 33 may be set so that the head of the fuel spray injected by the injector 33 flows into the combustion chamber 42 from the intake port 33a. In this case, since the head of the fuel spray flows into the combustion chamber 42, all (100%) of the fuel spray injected by the injector 33 flows into the combustion chamber 42. Therefore, it is possible to inject the fuel as early as possible while avoiding the fuel spray from colliding with the intake valve 18. As a result, more fuel can be supplied into the combustion chamber 42 while suppressing fuel from adhering to the intake valve 18.

  In the above embodiment, the predetermined speed is a fixed value at which the airflow speed in the port is set lower than the maximum speed value. In this regard, the predetermined speed may be a variable value that varies depending on the operating state parameter within a range where the airflow speed in the port does not reach the maximum speed.

  In the above embodiment, the injection end time is set when the airflow speed in the port reaches a predetermined speed. In this regard, the injection end timing is not limited to being set based on the airflow velocity in the port, but may be set based on the lift amount of the intake valve 18, for example. Specifically, the fuel injection by the injector 33 is set to end when the lift amount of the intake valve 18 reaches a predetermined lift amount before the maximum lift amount. Even with this configuration, the same effects as those of the above embodiment can be obtained.

  In the above embodiment, in order to inject the required injection amount set within the period from time t5 to time t8 shown in FIG. 5, the injection rate is controlled to be high by adjusting the pressure of the fuel supplied to the injector 33. It was. In order to achieve this high injection rate, in addition to adjusting the pressure of the fuel supplied to the injector 33, by providing an injector that can inject at a high injection rate without depending on the pressure of the fuel supplied to the injector 33. It may be realized.

  DESCRIPTION OF SYMBOLS 10 ... ECU, 17 ... Internal combustion engine, 18 ... Intake valve, 33 ... Injector, 42 ... Combustion chamber.

Claims (10)

A combustion chamber (42) for combusting a mixture of air and fuel, a port injection valve (33) for injecting fuel toward an intake port that communicates with the combustion chamber, and an intake port provided and opened. An injection control device (10) applied to an internal combustion engine (17) comprising an intake valve (18) for allowing air to flow into the combustion chamber,
The injection control device is configured to reduce the amount of fuel injected by the port injection valve in one combustion cycle from when the intake valve starts to open until the speed of the airflow generated by opening the intake valve becomes higher than a predetermined speed. An injection control apparatus, wherein a start timing and an end timing of fuel injection by the port injection valve are set so that low-speed airflow injection in which more fuel than a predetermined ratio is injected is performed.   The injection control device is configured so that more than 70% of the total fuel injected by the port injection valve flows from the intake port into the combustion chamber after the intake valve starts to open. The injection control device according to claim 1, wherein the start timing of fuel injection by the injection valve is set.   The injection control device is configured such that when the intake valve starts to open, fuel injection by the port injection valve is performed so that a head of fuel spray injected by the port injection valve flows into the combustion chamber from the intake port. The injection control device according to claim 1, wherein the start time is set.   The fuel injection control device sets the fuel injection end time so that the fuel injection by the port injection valve ends when the speed of the airflow by opening the intake valve reaches the predetermined speed. Item 4. The injection control device according to any one of Items 1 to 3.   The injection control device sets the end timing of fuel injection so that fuel injection by the port injection valve ends when the lift amount of the intake valve reaches a predetermined lift amount before reaching the maximum lift amount. The injection control device according to any one of claims 1 to 4, wherein The internal combustion engine includes an intake valve timing variable mechanism (46) for adjusting the opening / closing timing of the intake valve,
The injection control device is configured to advance the start timing based on an advance amount of the opening timing of the intake valve when the opening timing of the intake valve is advanced by the intake valve timing variable mechanism. The injection control apparatus according to any one of claims 1 to 5, wherein The internal combustion engine includes an intake valve timing variable mechanism (46) for adjusting the opening / closing timing of the intake valve,
The injection control device is configured to advance the end timing based on an advance amount of the closing timing of the intake valve when the closing timing of the intake valve is advanced by the intake valve timing variable mechanism. The injection control apparatus according to any one of claims 1 to 6, wherein the injection control apparatus is characterized in that:   The injection control device sets the start timing and the end timing of fuel injection by the port injection valve so that the low-speed air flow injection is performed when the load of the internal combustion engine is larger than a predetermined load. The injection control device according to any one of claims 1 to 7, wherein   The injection control device performs exhaust stroke injection in which all fuel injected by the port injection valve in one combustion cycle is injected in an exhaust stroke of the internal combustion engine when the load is smaller than the predetermined load. The injection control device according to claim 8, wherein the start timing and the end timing of fuel injection by the port injection valve are set as described above.   The injection control device sets the start timing and the end timing of fuel injection by the port injection valve so that the low-speed air flow injection is performed when the load is larger than the predetermined load, and the load 10. The start timing and the end timing of fuel injection by the port injection valve are set so that the exhaust stroke injection is performed when the engine is smaller than the predetermined load. Injection control device.