阅读说明：本技术 内燃机的控制装置 (Control device for internal combustion engine ) 是由 三谷信一 于 2021-06-07 设计创作，主要内容包括：本发明涉及内燃机的控制装置。内燃机包括燃料喷射阀以及火花塞,其中,该燃料喷射阀将燃料喷射到燃烧室中,该火花塞点燃燃烧室中的空燃混合物。内燃机的控制装置包括电子控制单元,该电子控制单元被构造成：当内燃机的冷起动开始时,在一个周期中向每个气缸中执行多次燃料喷射；在内燃机的冷起动开始之后,延迟每个气缸中的火花塞的点火正时；并且在火花塞的点火正时被延迟之后,根据火花塞的点火正时的延迟,减少在一个周期中向每个气缸中的燃料喷射次数。(The present invention relates to a control device for an internal combustion engine. An internal combustion engine includes a fuel injection valve that injects fuel into a combustion chamber, and a spark plug that ignites an air-fuel mixture in the combustion chamber. The control device of an internal combustion engine includes an electronic control unit configured to: performing a plurality of fuel injections into each cylinder in one cycle when a cold start of the internal combustion engine is started; retarding an ignition timing of an ignition plug in each cylinder after a cold start of the internal combustion engine is started; and after the ignition timing of the ignition plug is retarded, the number of fuel injections into each cylinder in one cycle is reduced in accordance with the retardation of the ignition timing of the ignition plug.)

1. A control device of an internal combustion engine including a fuel injection valve that injects fuel into a combustion chamber and an ignition plug that ignites an air-fuel mixture in the combustion chamber, characterized by comprising:

an electronic control unit configured to:

the electronic control unit performs a plurality of fuel injections into each cylinder in one cycle when a cold start of the internal combustion engine is started;

the electronic control unit retards an ignition timing of the ignition plug in each cylinder after the start of the cold start of the internal combustion engine; and is

The electronic control unit reduces the number of fuel injections into each cylinder in one cycle after the ignition timing of the ignition plug is retarded.

2. The control apparatus according to claim 1, characterized in that the electronic control unit is configured to retard the ignition timing in each cylinder stepwise.

3. The control apparatus according to claim 1 or 2, characterized in that the electronic control unit is configured to reduce the number of fuel injections into each cylinder in one cycle after the retardation of the ignition timing in each cylinder is all completed.

4. The control apparatus according to claim 2, wherein the electronic control unit is configured to gradually reduce the number of fuel injections into each cylinder in one cycle in response to a gradual delay in the ignition timing in each cylinder.

Technical Field

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

Background

Split injection in which a plurality of fuel injections are performed into a combustion chamber of each cylinder in each cycle is well known (see, for example, japanese unexamined patent application publication No. 2006-291971 (JP 2006-291971A)). In particular, in JP 2006-291971A, it has been proposed to increase the number of fuel injections in the split injection when a heavy fuel having poor atomization characteristics is used as compared to when a standard fuel is used.

Disclosure of Invention

It is also conceivable to perform split injection to promote atomization of the injected fuel when the internal combustion engine is cold started. Meanwhile, when the internal combustion engine is cold started, it is necessary to warm up the exhaust gas control catalyst of the internal combustion engine at an early stage to reduce exhaust emissions. As described above, in order to warm up the exhaust gas control catalyst of the internal combustion engine at an early stage, it is conceivable to set the ignition timing of the ignition plug to a retarded side timing.

However, when the ignition timing is set to the timing on the retard side in the state where the split injection is performed, the combustion stability of the air-fuel mixture may deteriorate, and the vibration in the internal combustion engine may increase.

The invention provides a control device of an internal combustion engine capable of suppressing deterioration of combustion stability of an air-fuel mixture even when a delay of a split injection and an ignition timing is performed at the time of cold start of the internal combustion engine.

The gist of the present invention will be described below.

A control device of an internal combustion engine according to an aspect of the present invention includes a fuel injection valve that injects fuel into a combustion chamber, and an ignition plug that ignites an air-fuel mixture in the combustion chamber. The control device includes an electronic control unit configured to: the electronic control unit performs a plurality of fuel injections into each cylinder in one cycle when a cold start of the internal combustion engine is started; the electronic control unit retards the ignition timing of the ignition plug in each cylinder after the start of cold start of the internal combustion engine; and the electronic control unit reduces the number of fuel injections into each cylinder in one cycle after the ignition timing of the ignition plug is retarded.

In the above aspect, the electronic control unit may retard the ignition timing in each cylinder step by step.

In the above aspect, the electronic control unit may reduce the number of fuel injections into each cylinder in one cycle after the retardation of the ignition timing in each cylinder is all completed.

In the above aspect, the electronic control unit may gradually decrease the number of fuel injections into each cylinder in one cycle in response to a gradual retardation of the ignition timing in each cylinder.

According to the above aspect of the invention, there is provided a control device of an internal combustion engine that can restrict deterioration of combustion stability of an air-fuel mixture even when split injection and retardation of ignition timing are performed at the time of cold start of the internal combustion engine.

Drawings

Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like reference numerals denote like elements, and in which:

fig. 1 is a view schematically showing an internal combustion engine using a control apparatus according to an embodiment;

fig. 2A is a view showing a transition of an injection rate from a fuel injection valve from an intake stroke to a compression stroke in one cylinder;

fig. 2B is another view showing a transition of the injection rate from the fuel injection valve from the intake stroke to the compression stroke in one cylinder;

fig. 2C is still another view showing a transition of the injection rate from the fuel injection valve from the intake stroke to the compression stroke in one cylinder;

FIG. 3 is a timing diagram of various parameters when the internal combustion engine is cold started;

fig. 4 is a flowchart showing a control routine for determining control to be executed in the start control;

FIG. 5 is a flowchart showing a control routine for controlling ignition timing by the spark plug;

fig. 6 is a flowchart showing a control routine for controlling the number of fuel injections from the fuel injection valve;

FIG. 7 is a timing diagram of various parameters similar to FIG. 3 when the internal combustion engine is cold started; and is

Fig. 8 is a time chart of various parameters at the time of cold start of the internal combustion engine, similar to fig. 3 and 7.

Detailed Description

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. In the following description, like parts are denoted by like reference numerals.

First embodiment

Structure of internal combustion engine

First, an internal combustion engine using a control apparatus according to one embodiment will be described with reference to fig. 1. The internal combustion engine of the embodiment is used for driving a vehicle. Fig. 1 is a view schematically showing an internal combustion engine using a control apparatus according to an embodiment. As shown in fig. 1, the internal combustion engine 1 includes an engine body 10, a fuel supply apparatus 30, an intake system 40, an exhaust system 50, and a control apparatus 60.

The engine body 10 includes: a cylinder block 12 in which a cylinder 11 is formed; and a cylinder head 13, the cylinder head 13 being fixed to the cylinder block 12. In each cylinder 11, a piston 14 is arranged for movement therein in a reciprocating manner. In the cylinder 11, between the piston 14 and the cylinder head 13, a combustion chamber 15 is formed in which an air-fuel mixture is burned.

In the cylinder head 13, an intake port 17 and an exhaust port 18 are formed. The intake port 17 and the exhaust port 18 communicate with the combustion chamber 15 of each cylinder 11. Between the combustion chamber 15 and the intake port 17, an intake valve 19 for opening and closing the intake port 17 is arranged. Similarly, between the combustion chamber 15 and the exhaust port 18, an exhaust valve 20 for opening and closing the exhaust port 18 is disposed.

Further, in the cylinder head 13, at the center of the inner wall surface defining each cylinder 11, an ignition plug 21 is arranged. The ignition plug 21 is configured to generate a spark and ignite the air-fuel mixture in the combustion chamber 15 in response to an ignition signal.

Further, the engine body 10 is provided with a starter motor 22, and the starter motor 22 drives the stopped internal combustion engine 1. The starter motor 22 rotates a crankshaft connected to the piston 14 via a connecting rod. When the internal combustion engine 1 is used in a hybrid vehicle, a motor generator or the like (also used to drive the vehicle) may be used to drive the stopped internal combustion engine 1, instead of the starter motor 22.

The fuel supply device 30 includes a fuel injection valve 31, a fuel supply pipe 32, a fuel pump 33, and a fuel tank 34. A fuel injection valve 31 is arranged in the cylinder head 13 so as to directly inject fuel into the combustion chamber 15 of each cylinder 11.

The fuel injection valve 31 is connected to a fuel tank 34 via a fuel supply pipe 32. A fuel pump 33 that pumps fuel in a fuel tank 34 is disposed in the fuel supply pipe 32. The fuel pumped by the fuel pump 33 is supplied to the fuel injection valve 31 via the fuel supply pipe 32, and is directly injected from the fuel injection valve 31 into the combustion chamber 15 as the fuel injection valve 31 is opened.

The intake system 40 includes an intake branch pipe 41, a surge tank 42, an intake pipe 43, an air cleaner 44, and a throttle valve 45. The intake port 17 of each cylinder 11 communicates with the surge tank 42 via a corresponding intake branch pipe 41, and the surge tank 42 communicates with the air cleaner 44 via an intake pipe 43. The throttle valve 45 is disposed in the intake pipe 43 and is rotated by a throttle valve drive actuator 47 to change the size of the open region of the intake passage. The intake port 17, the intake branch pipe 41, the surge tank 42, and the intake pipe 43 form an intake passage through which intake gas is supplied into the combustion chamber 15.

The exhaust system 50 includes an exhaust manifold 51, an exhaust gas control catalyst 53 accommodated in a housing 52, and an exhaust pipe 54. The exhaust port 18 of each cylinder 11 communicates with an exhaust manifold 51, and the exhaust manifold 51 communicates with a housing 52 that houses an exhaust gas control catalyst 53. The housing 52 communicates with an exhaust pipe 54.

The exhaust gas control catalyst 53 removes unburned HC, CO, and NO from the exhaust gas_xThe apparatus of (1). Examples of the exhaust gas control catalyst 53 include a three-way catalyst in which a noble metal catalyst (such as platinum) is supported on a carrier formed of cordierite. The exhaust gas control catalyst 53 may be formed as a particulate filter having a function of collecting particulate matter as long as it has a noble metal catalyst and can remove unburned HC, CO, and NO from exhaust gas_xAnd (4) finishing. Row boardThe air port 18, the exhaust manifold 51, the housing 52, and the exhaust pipe 54 form an exhaust passage through which exhaust gas is discharged from the combustion chamber 15.

The control device 60 includes an Electronic Control Unit (ECU)61 and various sensors. The ECU 61 includes a memory 62, a CPU (microprocessor) 63, an input port 64, and an output port 65 connected to each other via a bidirectional bus 66.

The control device 60 includes an air flow meter 71, a throttle opening sensor 72, a catalyst temperature sensor 73, a coolant temperature sensor 75, a load sensor 77, and a crank angle sensor 78. The air flow meter 71 is arranged in the intake pipe 43 and detects the air flow rate of the air flowing in the intake pipe 43. A throttle opening sensor 72 is provided in the throttle valve 45 and detects the opening of the throttle valve 45. In addition, a catalyst temperature sensor 73 is provided in the exhaust gas control catalyst 53 and detects the temperature of the exhaust gas control catalyst 53. In addition, a coolant temperature sensor 75 is provided in the engine body 10 and detects the temperature of the coolant for cooling the internal combustion engine 1. Outputs of the air flow meter 71, the throttle opening degree sensor 72, the catalyst temperature sensor 73, and the coolant temperature sensor 75 are input through the corresponding AD converters 67 to the input port 64.

Further, the load sensor 77 is connected to the accelerator pedal 76, and generates an output voltage proportional to the depression amount of the accelerator pedal 76. The output voltage of the load sensor 77 is input to the input port 64 as a signal indicating the engine load via the corresponding AD converter 67. The crank angle sensor 78 generates an output pulse each time the crankshaft rotates by, for example, 10 degrees, and the output pulse is input to the input port 64. The CPU 63 calculates the engine speed from the output pulse of the crank angle sensor 78.

Meanwhile, the output port 65 is connected to the ignition plug 21, the fuel injection valve 31, and the throttle valve drive actuator 47 via corresponding drive circuits 68. Therefore, the ECU 61 functions as a control device that controls the ignition timing of the ignition plug 21, the fuel injection timing or the amount of fuel injected from the fuel injection valve 31, the opening degree of the throttle valve 45, and the like.

Split stream injection

The control device 60 of the internal combustion engine 1 according to the embodiment can cause the fuel injection valve 31 to perform split injection in which a plurality of fuel injections are performed into each cylinder 11 in one cycle. Hereinafter, split injection will be briefly described with reference to fig. 2A to 2C.

Fig. 2A to 2C respectively show transition of the injection rate from the fuel injection valve 31 from the intake stroke to the compression stroke in one cylinder 11. Fig. 2A shows a transition to performing fuel injection into each cylinder 11 only once in one cycle without performing split injection. Fig. 2B shows a transition in the case where fuel injection is performed twice into each cylinder 11 in one cycle by performing split injection. Fig. 2C shows a transition in the case where three fuel injections into each cylinder 11 are performed in one cycle by performing split injection. In the example shown in fig. 2A to 2C, the total fuel injection amount per cycle is equal.

As shown in fig. 2A, when only one fuel injection is performed, the period during which the fuel injection rate is maximized is long. Since a large amount of fuel is injected at high pressure from the fuel injection valve 31 when the fuel injection rate is high, the fuel that cannot be vaporized is liable to adhere to the wall surface of the cylinder 11. In particular, since the wall surface temperature of the cylinder 11 is low when the internal combustion engine 1 is cold started, the fuel is easily liquefied in the vicinity of the wall surface of the cylinder 11, and it is difficult to vaporize the fuel adhering to the wall surface thereafter. As a result, when only one fuel injection is performed at the time of cold start of the internal combustion engine 1, a part of the fuel adheres to the wall surface of the cylinder 11, and thus the vaporization fuel amount with respect to the injection fuel amount decreases.

On the other hand, as shown in fig. 2B or fig. 2C, when the plurality of fuel injections are performed, the period in which the fuel injection rate is high is shortened, and therefore the amount of fuel adhering to the wall surface of the cylinder 11 is reduced. Therefore, the reduction in the amount of vaporized fuel due to the adhesion of the fuel to the wall surface is limited. This tendency substantially increases as the number of injections increases. Therefore, as shown in fig. 2C, when three fuel injections are performed, the amount of fuel adhering to the wall surface of the cylinder 11 can be further reduced, and therefore the reduction in the vaporization fuel amount can be further restricted. For this reason, when the internal combustion engine 1 is cold started, split injection in which injection is performed as many times as possible may be performed.

Ignition delay

When the internal combustion engine 1 is cold started, not only the temperature of the engine body 10 is low, but also the temperature of the exhaust gas control catalyst 53 is low. When the temperature of the exhaust gas control catalyst 53 becomes equal to or higher than the activation temperature of the precious metal catalyst of the exhaust gas control catalyst 53, harmful substances can be removed from the exhaust gas at a high removal rate. Therefore, from the viewpoint of removing harmful substances in the exhaust gas, when the internal combustion engine 1 is cold started, it is necessary to raise the temperature of the exhaust gas control catalyst 53 to the activation temperature as quickly as possible.

The ignition timing of the ignition plug 21 is basically set to the minimum advance for best torque (MBT). By igniting the air-fuel mixture at the MBT, combustion efficiency is maximized, and thus output torque and fuel efficiency may be improved. On the other hand, when the ignition timing is more retarded than MBT, the combustion timing of the air-fuel mixture is retarded, and the proportion of thermal energy remaining without being converted into kinetic energy among the thermal energy obtained by combustion increases. As a result, when the ignition timing is retarded, the temperature of the exhaust gas discharged from the engine body 10 increases. When the temperature of the exhaust gas is increased in this way, the temperature of the exhaust gas control catalyst 53 can be increased by the heat of the exhaust gas at an early stage. Therefore, when the internal combustion engine 1 is cold started, the ignition timing of the ignition plug 21 may be set to a timing on the more retarded side than MBT.

Start-up control

The start control performed by the control device 60 according to the present embodiment will be described with reference to fig. 3. Fig. 3 is a time chart of various parameters when the internal combustion engine 1 is cold started. Specifically, fig. 3 is a diagram showing the rotation speed (engine rotation speed) R of the internal combustion engine 1_eThe fuel injection quantity Q into each cylinder 11 in each cycle_fIgnition timing T of ignition plug 21_iNumber N of fuel injections into each cylinder 11 per cycle_iAnd a timing chart of the output torque TQ of the internal combustion engine 1. When the internal combustion engine 1 is driven by the starter motor 22, the value of the output torque TQ of the internal combustion engine 1 is negative.

In the example shown in fig. 3, the internal combustion engine 1 is stopped until time t₁To date, and thus the engine speed R_eFuel injection quantity Q_fAnd the output torque TQ are both zero. At time t₁The start control of the internal combustion engine 1 for start stop is started. The start control is executed for changing the internal combustion engine 1 from a state in which the crankshaft is stopped to a state in which rotation can be maintained by combustion of the air-fuel mixture.

At time t₁When the start control is started, first, the internal combustion engine 1 is driven by the starter motor 22. As a result, the engine speed R_eAnd the value of the output torque TQ becomes negative as torque is transmitted from the starter motor 22 to the internal combustion engine 1. In the present embodiment, immediately after the start control is started, neither fuel injection from the fuel injection valve 31 nor ignition by the ignition plug 21 is performed.

In the present embodiment, thereafter, at time t₂When the engine speed R_eReaches a predetermined reference rotation speed R_erefAt this time, fuel injection from the fuel injection valve 31 is started, and ignition of the air-fuel mixture formed by the fuel injection by the ignition plug 21 is started. In the present embodiment, when the engine speed R is_eReaches a reference rotation speed R_erefWhen fuel injection and ignition are started, fuel injection and ignition may be started at different timings. For example, the fuel injection and the ignition may be started at the same timing as when the driving by the starter motor 22 is started, or may be started at a timing after the crankshaft is rotated by only a predetermined rotation amount by the starter motor 22.

In the present embodiment, during the start control, the number of times N of fuel injection from the fuel injection valve 31 into each cylinder 11 per cycle_iIs set to the maximum number of injections. Therefore, in the present embodiment, when the cold start of the internal combustion engine 1 is started, the split injection control for performing the fuel injection into each cylinder 11 a plurality of times is performed in one cycle. In particular, in the present embodiment, in each fuel injection, a fuel injection obtained by dividing the total injection amount per cycle by the maximum injection number on average is injectedAn amount of fuel. Here, the maximum injection number is set so that when the fuel injection number becomes larger than the maximum injection number, the amount of one fuel injection is reduced too much to be accurately controlled. Therefore, during the start control, the fuel injected from the fuel injection valve 31 is restricted from adhering to the wall surface of each cylinder 11, thereby promoting atomization of the fuel.

Further, in the present embodiment, during the start control, the ignition timing T of the ignition plug 21_iA predetermined timing that is set to the relatively advance side (for example, a timing near MBT, hereinafter referred to as "advance side timing T")_iad"). Therefore, the air-fuel mixture in the combustion chamber 15 can be burned in a relatively stable state.

At time t₂After that, by performing fuel injection from the fuel injection valve 31 and ignition by the ignition plug 21, the air-fuel mixture is combusted in the combustion chamber 15, so that torque is generated by the internal combustion engine 1. For this purpose, at a time t₂Thereafter, the output torque TQ increases, and therefore the engine speed R_eAnd (4) increasing. Thereafter, when the output torque TQ becomes equal to or greater than a predetermined torque (which has a value equal to or greater than zero), the starter motor 22 is stopped, and when the engine speed R is_eFuel injection quantity Q at a predetermined rotational speed equal to or greater than the idling rotational speed_fAnd decreases. In this way, when the engine speed R is_eWhen a predetermined rotation speed equal to or greater than the idling rotation speed is reached, the internal combustion engine 1 is in a state in which rotation can be maintained by combustion of the air-fuel mixture.

In the present embodiment, at time t₃When an arbitrary number of cycles (for example, 2 or 3 cycles) have been completed since the start of fuel injection and ignition, the start control ends and the warm-up control starts. As shown in fig. 3, time t₃At engine speed R_eAt a time after reaching a predetermined rotation speed equal to or greater than the idling rotation speed, and at a time t₃Engine speed R_eThe decrease is started. In the present embodiment, the end timing of the start control is set based on the number of cycles after the start of fuel injection and ignition. Alternatively, it can be set in any mannerEnd timing of the dynamic control as long as the end timing is the engine speed R_eThe timing after reaching the predetermined rotation speed equal to or greater than the idling rotation speed may be sufficient. Thus, for example, when the engine speed R is detected by using the crank angle sensor 78_eWhen the predetermined rotation speed is reached, the start control may be ended.

The warm-up control is executed for raising the temperatures of the engine body 10 and the exhaust gas control catalyst 53 at an early stage. Thus, at time t₃When the warm-up control is started, the ignition timing T of the ignition plug 21_iFrom the advance side to timing T_iadTo a relatively retarded side (hereinafter referred to as "retarded side timing T_irt"). Therefore, in the present embodiment, the ignition timing Ti of the ignition plug 21 is retarded after the start of the internal combustion engine 1 is started. Here, the side timing T is retarded_irtIs set to be a timing on the retard side as much as possible in a range capable of maintaining combustion within, for example, 15 ° ATDC. As a result, at time t₃After that, the temperature of the exhaust gas rises, and therefore the temperature of the exhaust gas control catalyst 53 rises.

Further, in the present embodiment, at time t₄When it has been since the start of the warm-up control (i.e., since the ignition timing T of the ignition plug 21)_iDelayed) has completed any number of cycles (e.g., 2 or 3 cycles), the number of fuel injections N from fuel injection valve 31_iFrom the maximum number of injections to the minimum number of injections (e.g., one injection). In other words, in the present embodiment, at the ignition timing T_iNumber of fuel injections N after delay_iAnd (4) reducing. In particular, at the completion of the ignition timing T_iAfter the delay of (3), the number of fuel injections N_iAnd (4) reducing.

After that, when the temperature of the exhaust gas control catalyst 53 is increased to the activation temperature, for example, the warm-up control is ended. When the warm-up control ends, the start control of the internal combustion engine 1 ends, and the normal control starts. In the normal control, the ignition timing T_iAnd the number of times of fuel injection N from the fuel injection valve 31_iBased on engine speed R_eAnd engine load. In particular, the ignition timing T_iIs basically set to a timing on the relatively advance side in the vicinity of MBT.

Flow of startup control

Next, the flow of the start control executed by the control device 60 according to the present embodiment will be described with reference to fig. 4 to 6. Fig. 4 is a flowchart showing a control routine for determining control to be executed in the start control. The ECU 61 executes the illustrated control routine at regular time intervals.

Referring to fig. 4, first, in step S11, the ECU 61 determines the start flag F_sWhether or not it is set to OFF. When the start control is executed, a start flag F_sIs set to ON, and at other times, the start flag F_sIs set to OFF. In step S11, when the ECU 61 determines the start flag F_sWhen OFF is set, the control routine proceeds to step S12.

In step S12, the ECU 61 determines the warm-up flag F_wWhether or not it is set to OFF. During execution of the warm-up control, the warm-up flag F_wIs set to ON, and at other times, the warm-up flag is set to OFF. In step S12, when the ECU 61 determines the warm-up flag F_wWhen OFF is set, the control routine proceeds to step S13.

In step S13, the ECU 61 determines whether the start condition is satisfied. The start condition is satisfied in the case where, for example, an ignition switch of a vehicle in which the internal combustion engine 1 is mounted is turned on, or in the case where the ECU 61 determines to automatically start the internal combustion engine 1 because the battery needs to be charged. In step S13, when the ECU 61 determines that the start condition is not satisfied, the control routine ends. On the other hand, in step S13, when the ECU 61 determines that the start condition is satisfied, the control routine proceeds to step S14, where a start flag F is set_sIs set to ON, and the start control is started.

When starting flag F_sSet to ON and the start control is started, the control routine proceeds from step S11 to step S15. In step S15, the ECU 61 determines whether a condition for completing the start control is satisfied. The pre-ignition has been completed since the ignition of the ignition plug 21 in, for example, the start controlIn the case of a fixed number of cycles (e.g., 2 or 3 cycles), or at the engine speed R detected by the crank angle sensor 78_eThe condition for completing the start control is satisfied when the predetermined rotation speed is reached. In step S15, when the ECU 61 determines that the condition for completing the start control is not satisfied, the control routine ends. On the other hand, when the ECU 61 determines that the condition for completing the start control is satisfied, the control routine proceeds to step S16. In step S16, start flag F_sIs set to OFF, and the start control ends.

Next, in step S17, the ECU 61 determines whether the condition for executing warm-up is satisfied. The condition for executing the warm-up is satisfied in a case where, for example, the temperature of the coolant of the internal combustion engine 1 detected by the coolant temperature sensor 75 is lower than a predetermined warm-up completion temperature, or in a case where the temperature of the exhaust gas control catalyst 53 detected by the catalyst temperature sensor 73 is lower than an activation temperature. In other words, in the case where the internal combustion engine 1 is started (cold start) in a state where the temperature of the coolant or the exhaust gas control catalyst 53 is low, the condition for performing warm-up is satisfied. In step S17, when the ECU 61 determines that the condition for executing warm-up is not satisfied, the control routine ends. In this case, the normal control is started without executing the warm-up control. On the other hand, in step S17, when the ECU 61 determines that the condition for executing warm-up is satisfied, the control routine proceeds to step S18, where a warm-up flag F is set_wIs set to ON, and the warm-up control is started.

When preheating flag F_wSet to ON and warm-up control starts, the control routine proceeds from step S12 to step S19. In step S19, the ECU 61 determines whether a condition for ending the warm-up control is satisfied. The condition for ending the warm-up control is satisfied in a case where, for example, the temperature of the coolant of the internal combustion engine 1 detected by the coolant temperature sensor 75 is equal to or higher than a predetermined warm-up completion temperature, or in a case where the temperature of the exhaust gas control catalyst 53 detected by the catalyst temperature sensor 73 is equal to or higher than an activation temperature. In step S19, when the ECU 61 determines that the condition for ending the warm-up control is not presentWhen satisfied, the control routine ends. On the other hand, in step S19, when the ECU 61 determines that the condition for ending the warm-up control is satisfied, the control routine proceeds to step S20. In step S20, the warm-up flag F_wIs set to OFF, the warm-up control ends, and the normal control starts.

FIG. 5 is a diagram showing a control for the ignition timing T by the ignition plug 21_iIs performed by the control routine of (1). The ECU 61 executes the illustrated control routine at regular time intervals.

As shown in fig. 5, first, in step S31, the ECU 61 determines the start flag F_sWhether or not it is set to ON, i.e., whether or not the start-up control is being executed. When starting flag F_sWhen set to ON, the control routine proceeds to step S32. In step S32, the ignition timing T_iIs set to advance side timing T_iad. On the other hand, in step S31, when the ECU 61 determines that the start flag F is set_sWhen OFF is set, the control routine proceeds to step S33.

In step S33, the ECU 61 determines the warm-up flag F_wWhether or not it is set to ON, i.e., whether or not the warm-up control is being executed. When the ECU 61 determines the warm-up flag F_wWhen set to ON, the control routine proceeds to step S34. In step S34, the ignition timing T_iIs set to retard side timing T_irt. On the other hand, in step S33, when the ECU 61 determines the warm-up flag F_wWhen OFF is set, the control routine proceeds to step S35. In step S35, normal control is executed, and the ignition timing T_iBased on engine speed R_eThe engine speed is calculated based on the output of the crank angle sensor 78, and the engine load is set based on the engine load detected by the load sensor 77.

FIG. 6 is a view showing a method for controlling the number of times of fuel injection N from the fuel injection valve 31_iIs performed by the control routine of (1). The ECU 61 executes the illustrated control routine at regular time intervals.

As shown in fig. 6, first, in step S41, the ECU 61 determines the start flag F_sWhether or not it is set to ON. When starting flag F_sIs set upWhen ON, the control routine proceeds to step S42. In step S42, the number of times N of fuel injection into each cylinder 11 per cycle is set_iThe maximum number of injections is set. On the other hand, in step S41, when the ECU 61 determines that the start flag F is set_sWhen OFF is set, the control routine proceeds to step S43.

In step S43, the ECU 61 determines the warm-up flag F_wWhether or not it is set to ON. When the ECU 61 determines the warm-up flag F_wWhen set to ON, the control routine proceeds to step S44. In step S44, the ECU 61 determines the ignition timing T since the ignition timing T was changed by step S34 in FIG. 5_iSet to retard side timing T_irtWhether a predetermined number of cycles (e.g., 2 or 3 cycles) have been completed since then. Alternatively, in step S44, the ECU 61 may determine that the ignition timing T has been set since_iSet to retard side timing T_irtWhether a predetermined period of time has elapsed. In step S44, when the ECU 61 determines that the ignition has been timed T since it was turned off_iSet to retard side timing T_irtWhen the predetermined number of cycles has not been completed, the control routine proceeds to step S42, and the number of fuel injections N into each cylinder 11 in each cycle_iMaintained at the maximum number of injections. On the other hand, in step S44, when the ECU 61 determines that the ignition timing T has been changed since_iSet to retard side timing T_irtWhen the predetermined number of cycles has been completed since then, the control routine proceeds to step S45. In step S45, the number of fuel injections N into each cylinder 11 per cycle_iIs set to the minimum number of injections.

On the other hand, in step S43, when the ECU 61 determines the warm-up flag F_wWhen OFF is set, the control routine proceeds to step S46. In step S46, normal control is executed, and the number N of fuel injections into each cylinder 11 per cycle_iBased on engine speed R_eThe engine speed is calculated based on the output of the crank angle sensor 78, and the engine load is set based on the engine load detected by the load sensor 77.

Advantageous effects and modified examples

In the above-described embodiments of the present invention,when the internal combustion engine 1 is cold started, first, in the start control, the ignition timing T of the ignition plug 21_iIs set to the timing on the relatively advance side, and fuel injection is performed into each cylinder 11 a plurality of times in one cycle. Thereafter, according to the start of the warm-up control, the ignition timing T_iIs retarded and according to the ignition timing T_iThe number of fuel injections N into each cylinder 11 in each cycle_iAnd (4) reducing.

Here, as described above, when the cold start of the internal combustion engine 1 is started, the number of fuel injections into the cylinder 11 per cycle may be increased to restrict a decrease in the amount of vaporized fuel due to adhesion of the injected fuel to the wall surface of the cylinder 11. However, when the number of injections is increased in this way, as can be seen from fig. 2A to 2C, the timing at which the final fuel injection is completed is retarded. As a result, the fuel injected at the retard timing is at the ignition timing T_iThere is insufficient mixing in the combustion chamber 15. For this reason, at the ignition timing T of the ignition plug 21_iHere, the homogeneity of the air-fuel mixture is low.

In this way, the ignition timing T is retarded when the homogeneity of the air-fuel mixture is low_iWhen the combustion of the air-fuel mixture is deteriorated. In response, in the present embodiment, when the homogeneity of the air-fuel mixture is low immediately after the internal combustion engine 1 is started, the ignition timing T is set_iIs set to the timing on the advance side. Therefore, combustion deterioration of the air-fuel mixture can be restricted.

Further, in the present embodiment, when the start of the internal combustion engine 1 is completed and the warm-up control is started, the ignition timing T is set to_iDelay, and hence the number of fuel injections N into each cylinder 11 per cycle_iAnd (4) reducing. When the number of fuel injections N_iWhen the amount is reduced, the injected fuel easily adheres to the wall surface of the cylinder 11, but since the fuel injection is completed at an early stage, the uniformity of the vaporized fuel that does not adhere to the wall surface is high. In this way, since the homogeneity of the air-fuel mixture is high, even when the ignition timing T is high_iWhen retarded, combustion of the air-fuel mixture does not deteriorate, and therefore appropriate combustion can be maintained. Thus, by this factExample, when the internal combustion engine 1 is cold started, even when the split injection and the ignition timing T are performed_iCan also suppress deterioration of the combustion stability of the air-fuel mixture. As a result, with the present embodiment, it is possible to restrict an increase in vibration or noise in the internal combustion engine 1.

However, when the number of fuel injections N_iWhen decreasing, the amount of fuel adhering to the wall surface of the cylinder 11 increases, and therefore the total fuel concentration of the air-fuel mixture becomes lower and combustion becomes difficult. At the same time, when the ignition timing T_iAt the time of the delay, the combustion state of the air-fuel mixture changes significantly, and thus the combustion becomes unstable. Therefore, when the number of fuel injections N is simultaneously performed_iReduction and ignition timing T_iThe possibility of misfire increases. In the present embodiment, the ignition timing T with the ignition plug 21 is set in each cycle_iIs performed to the number of fuel injections N into each cylinder 11 at different timings_iIs reduced. For this reason, when the transition from the start control to the warm-up control is executed, the possibility of misfire decreases. In particular, in the present embodiment, at the ignition timing T of the ignition plug 21_iAfter the delay, the number of fuel injections N into each cylinder 11_iAnd (4) reducing. Therefore, at the slave ignition timing T_iUntil the number of fuel injections N_iDuring the reduced period of time, the combustion state of the air-fuel mixture temporarily becomes unstable, and torque fluctuation is liable to occur, but the possibility of misfire due to the low total fuel concentration of the air-fuel mixture may be reduced. Further, since the timing immediately after the start control is completed is the timing immediately after the occurrence of a large torque fluctuation due to the start of the internal combustion engine 1, even when a torque fluctuation due to temporary instability of the combustion state occurs at this time, it is difficult for the occupant to sense this torque fluctuation.

In addition, in the above embodiment, the number of times of fuel injection into each cylinder 11 in each cycle during the start control, N_iIs set to the maximum number of injections. However, the number of fuel injections N during the start control_iMay be less than the maximum number of injections. However, also in this case, theNumber of fuel injections N during active control_iIs set to be greater than the number of fuel injections N during the warm-up control_i。

In addition, in the above embodiment, the ignition timing T of the ignition plug 21 during the warm-up control_iIs set to a timing that is on the retard side as much as possible within a range in which combustion can be maintained, but is the ignition timing T during the warm-up control_iMay be set to a timing closer to the advance side than the above timing. However, even in this case, the ignition timing T during the warm-up control_iIs also set to be larger than the ignition timing T during the start control_iTiming closer to the retard side.

Second embodiment

Next, with reference to fig. 7, a control device according to a second embodiment will be described. Hereinafter, differences from the control of the control device in the first embodiment will be mainly described.

In the first embodiment, the ignition timing T is started simultaneously with the warm-up control_iImmediately from the advance side timing T_iadChange to retard side timing T_irt. However, in the present embodiment, when the warm-up control is started, the ignition timing T_iFrom the advance side to timing T_iadStepwise change to retard side timing T_irt。

Fig. 7 is a time chart of various parameters when the internal combustion engine 1 is cold started, similar to fig. 3. As shown in fig. 7, in the present embodiment, when at time t₃Ignition timing T of the ignition plug 21 when the start control is completed and the warm-up control is started_iAnd gradually delaying. In the present embodiment, the ignition timing T is even during one cycle_iIt is gradually retarded according to the order of the cylinders 11 in which combustion is performed. Alternatively, the ignition timing T_iThe delay may be gradual in each cycle. In this case, all the cylinders 11 are operated at the same ignition timing T during the same cycle_iAnd (5) igniting.

Thereafter, in the present embodiment, at the ignition timing T_iTo the retard side timing T that has been set during the warm-up control_irtThereafter, at time t₄Number of fuel injections N from fuel injection valve 31_iFrom the maximum number of injections to the minimum number of injections. Therefore, also in the present embodiment, at the ignition timing T for the warm-up control_iAfter all of the delays are completed, the number of fuel injections N_iAnd (4) reducing.

With the present embodiment, since the ignition timing T_iIs retarded stepwise, so even when the ignition timing T is_iThe combustion state is also restricted so as not to become excessively unstable when greatly delayed, and therefore the occurrence of excessive torque fluctuations can be restricted.

Third embodiment

Next, with reference to fig. 8, a control device according to a third embodiment will be described. Hereinafter, differences from the control of the control device in the first and second embodiments will be mainly described.

In the first and second embodiments, the number of fuel injections N into each cylinder 11 per cycle_iThe maximum injection number is immediately changed to the minimum injection number. However, in the present embodiment, the number of fuel injections N into each cylinder 11 per cycle_iThe number of injections is gradually changed from the maximum number of injections to the minimum number of injections.

Fig. 8 is a timing chart of various parameters when the internal combustion engine 1 is cold-started, similarly to fig. 3 and 7. As shown in fig. 8, in the present embodiment, similarly to the second embodiment, when at time t₃Ignition timing T of the ignition plug 21 at the time of completion of the start control and start of the warm-up control_iAnd gradually delaying. In particular, in the present embodiment, the ignition timing T_iA predetermined angle is retarded in each firing or cycle.

Thereafter, in the present embodiment, each time the ignition timing T_iRetarding the angle by the number N of fuel injections into each cylinder 11 per cycle_iOne fuel injection is reduced. In other words, in the present embodiment, at the ignition timing T_iAfter a delay of a certain angle, the number of fuel injections N_iIs reduced corresponding to the retardation angle. In particular, in the present embodiment, the certain angle is sufficiently larger than each elongationRetarded ignition timing T_iThe angle of (c). Therefore, the ignition timing T is retarded a plurality of times_iThe number of fuel injections N into each cylinder 11 per cycle_iOne fuel injection is reduced.

In the example shown in fig. 8, during the start control, the number of fuel injections N performed into each cylinder 11 per cycle_iFive times. At the time of ignition T_iAfter a delay of a certain angle, the number of fuel injections N_iAnd reduced to four times. At ignition timing T_iAfter a delay of a certain angle again, the number of fuel injections N_iReduced to three times. By repeating the above operations, according to the ignition timing T_iGradual delay of, number of fuel injections N_iStepwise and finally to once. As can be seen from FIG. 8, the number of fuel injections N_iAt ignition timing T_iAnd starts after the start of the retardation of (b), and at the ignition timing T_iIs terminated after the delay of (1) is terminated. Therefore, in the present embodiment, according to the ignition timing T_iA number N of fuel injections into each cylinder 11 per cycle_iAnd gradually decreased.

With the present embodiment, the ignition timing T_iGradual delay, and thus number of fuel injections N_iAnd also gradually decreases. Also in the present embodiment, since the ignition timing T_iGradually retarded so that even when the ignition timing T is_iThe occurrence of excessive torque ripple can also be limited at a time of great delay. In addition, in the present embodiment, the number of fuel injections N_iAnd gradually decreased. Therefore, due to the ignition timing T_iThe temporary deterioration of the combustion state caused by the delay of (a) can be limited to a minimum.

Although the embodiments of the present invention have been described above as appropriate, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims.