JPH06249021A - Fuel injection device during startup - Google Patents

Abstract

PURPOSE:To make excellent security of both startability and exhaust emission of an internal combustion engine compatible to each other by estimating the startability of the internal combustion engine, and varying asynchronous injecting in compliance with o fuel injection type at the time of startup only when the estimated result is worse than a specified level. CONSTITUTION:A synchronized injection setting means 2 of o fuel injection means 1, injects fuel always at the same crank angle for response cylinders in synchronism with rotation of an internal combustion engine. On the other hand, an asynchronized injection setting means 3, injects fuel simultaneously to all the cylinders with no relation to the crank angle without being synchronous with the rotation of the internal combustion engine. The asynchronized injection setting means 3 of the fuel injection means 1 is selected by a fuel injection type selection means 5 as the fuel injection type at the time of startup is not synchronized only when the estimated startability is worse than specified level. Consequently, security of both startability and exhaust emission can be mode compatible with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a start-up fuel injection device, and more particularly to a start-up fuel injection device for controlling the fuel injection amount and injection timing at the start of an internal combustion engine equipped with an electronically controlled fuel injection device.

[0002]

2. Description of the Related Art In recent years, electronic control of internal combustion engines has advanced, and electronically controlled fuel injection devices have become widespread. In such an electronically controlled fuel injection device, the amount of fuel to be supplied to the internal combustion engine is calculated by a microcomputer based on the operating state, and the optimum amount of fuel is obtained by comprehensively considering fuel consumption, drivability, etc. Are supplied to the internal combustion engine.

By the way, when the electronically controlled fuel injection device is used, not only can the amount of fuel supplied to the internal combustion engine be optimized, but also the injection timing can be set arbitrarily. For this reason, various proposals have been made for fuel injection timing, and asynchronous injection in which fuel is injected regardless of the crank angle at the time of starting has been widely adopted.

In this case, asynchronous fuel injection means
This is a control for simultaneously injecting fuel into all cylinders of an internal combustion engine regardless of the crank angle, and is a control for synchronous injection in which fuel is injected into each cylinder at a constant crank angle. In the case of synchronously injecting fuel, the injected fuel is supplied to each cylinder as it is, and the injection amount and the amount actually flowing into the internal combustion engine substantially match, and a good air-fuel ratio can be maintained.

On the other hand, when the fuel is asynchronously injected, the air-fuel ratio cannot be controlled accurately because the injected fuel adheres to the inner wall of the intake pipe, but unlike the case of the synchronous injection, the fuel is not accurately controlled. It is not necessary to detect the state of each cylinder, that is, the accurate crank angle, as a premise of injection.

That is, when the fuel is supplied by the asynchronous injection, the fuel injection can be started at the same time when the start of the internal combustion engine is detected, and the initial explosion can be obtained earlier than by the synchronous injection. Become. For this reason, the asynchronous injection is widely adopted as described above when the internal combustion engine is started.

By the way, according to Japanese Patent Laid-Open No. 3-225046, a good exhaust emission and a good exhaust emission are achieved by starting the internal combustion engine by asynchronous injection and changing the fuel injection amount at the time of start according to the fluctuation of the battery voltage. A device capable of achieving both startability is disclosed.

In this device, when starting the internal combustion engine using the starter motor, the battery voltage may fall below the operating voltage of the microcomputer due to the large amount of power consumed by the starter motor. Is. That is, in such a case, it is considered that the microcomputer goes down as the battery voltage drops, and the initial process is performed each time.

In this case, the battery voltage fluctuates according to the load of the starter motor, and greatly drops when any of the cylinders forming the internal combustion engine enters the compression process. Therefore,
For example, in the case of a 4-cycle 4-cylinder internal combustion engine, the battery voltage repeatedly drops and rises four times while the crankshaft makes two revolutions (while each intake, compression, explosion, and exhaust is performed once in each cylinder). become.

Therefore, when the battery voltage repeatedly drops and rises in the vicinity of the operating voltage of the microcomputer, the microcomputer is initialized four times while the crankshaft makes two revolutions. Further, the microcomputer constituting the electronically controlled fuel injection device is
Since the fuel injection is set to be started at the same time when the internal combustion engine is started, the fuel is injected assuming that the internal combustion engine is started each time such initialization is performed.

For this reason, if no action is taken in an internal combustion engine that supplies fuel by asynchronous injection at the time of startup, the fuel is supplied to each cylinder four times during two revolutions of the crankshaft as the battery voltage fluctuates. Injection will be performed. Therefore, in such a situation, in order to make the total amount of fuel supplied to the internal combustion engine an appropriate amount, it is necessary to make the fuel injection amount at start-up 1/4 of that during normal operation.

However, reducing the fuel injection amount even when the fluctuation of the battery voltage does not affect the operation of the microcomputer undesirably deteriorates the startability of the internal combustion engine, which is not a preferable state.

In view of these circumstances, the device described in the above publication detects that the battery voltage is sufficiently secured by injecting the appropriately reduced fuel amount when the microcomputer is initialized. If so, the set amount is increased. Therefore, when the microcomputer repeatedly goes down at the time of starting the internal combustion engine, an appropriate amount of fuel is dividedly supplied, and when the microcomputer does not go down, an appropriate amount of fuel is asynchronously injected at a predetermined timing. become.

[0014]

However, as described above, the asynchronous injection of fuel is inferior to the synchronous injection in the accuracy of air-fuel ratio control. Further, if asynchronous injection is performed at the time of startup, it is necessary to shift to normal operation by synchronous injection after that, and in a cylinder in which individual fuel injection by synchronous injection is performed immediately after fuel supply to all cylinders by asynchronous injection Excess fuel, cylinders that do not have too little fuel.

That is, when the internal combustion engine is started by the asynchronous injection, the air-fuel ratio control at the time of starting becomes ambiguous, and when the fuel injection system is switched, the air-fuel ratio of the air-fuel mixture supplied to each cylinder is changed. This greatly deviates from the stoichiometric air-fuel ratio, and exhaust emission deteriorates significantly.

However, the above-mentioned conventional device is constructed so that the asynchronous injection is always performed when the internal combustion engine is started. Therefore, for example, in the case where the internal combustion engine is started in a sufficiently warm state, the asynchronous injection is performed even though a sufficiently good startability can be ensured by the synchronous injection, and the exhaust emission is unduly deteriorated. Had a problem.

The present invention has been made in view of the above points, and monitors the state of an internal combustion engine to estimate its startability,
The fuel injection at the time of starting can solve the above problems by performing the fuel injection at the time of starting the internal combustion engine by the asynchronous injection when the startability is required to be improved, and by the synchronous injection when the startability is not required. The purpose is to provide a device.

[0018]

FIG. 1 is a diagram showing the principle configuration of a fuel injection means for starting, which can achieve the above object. In the figure, the fuel injection means 1 appropriately switches the fuel injection pattern set by the synchronous injection setting means 2 and the fuel injection pattern set by the asynchronous injection setting means 3 to perform fuel injection to the internal combustion engine.

The synchronous injection setting means 2 sets the fuel synchronous injection pattern so that the fuel is always injected into each cylinder at the same crank angle in synchronization with the rotation of the internal combustion engine. Also,
The asynchronous injection setting means 3 does not synchronize with the rotation of the internal combustion engine,
An asynchronous fuel injection pattern is set so that fuel is simultaneously injected into all cylinders regardless of the crank angle.

The startability estimating means 4 estimates the startability of the internal combustion engine and supplies the estimation result to the injection method selecting means 5. The injection method selection means 5 performs the fuel injection at the time of starting with the injection pattern set by the asynchronous injection setting means 3 only when the startability of the internal combustion engine estimated by the startability estimation means 4 is worse than a predetermined level. The injection method of the injection means 1 is switched.

[0021]

In the starting-time fuel injection device according to the present invention, when the internal combustion engine is in a state where it is difficult to start, the injection method selection means 5 is based on the estimation result of the startability estimation means 4.
Selects the asynchronous injection method. Therefore, in such a case, when the internal combustion engine is started, fuel is injected from all the cylinders from the fuel injection means 1 regardless of the crank angle.
As a result, immediately after the start of the internal combustion engine, one of the cylinders becomes in a state where the initial explosion is possible, and an early start is possible.

On the other hand, when the internal combustion engine is in a state where it is easy to start, the injection method selection means 5 selects the synchronous injection method based on the estimation result of the startability estimation means 4. Therefore, the fuel is not injected from the fuel injection means 1 toward the internal combustion engine until the position of the crank angle, that is, the state of each cylinder can be detected after the internal combustion engine is started. In, the first explosion cannot be obtained in any cylinder.

On the other hand, in such a case, the fuel injected from the fuel injection means 1 at the time of starting the internal combustion engine is faithfully drawn into each cylinder of the internal combustion engine, and it is not necessary to switch the fuel injection method thereafter. As a result, it becomes possible to consistently and highly accurately control the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine.

[0024]

FIG. 2 is an overall view showing the construction of an internal combustion engine 10 equipped with a fuel injection device for start-up according to an embodiment of the present invention and peripheral devices thereof. In this embodiment, a 4-cycle 4-cylinder internal combustion engine will be described as an example.

In the figure, an intake air temperature sensor 11 is arranged downstream of an air cleaner (not shown) and detects the temperature of intake air and outputs an intake air temperature signal. Downstream of the intake air temperature sensor 11, a throttle sensor 13 that detects the opening degree of a throttle valve 12 that opens and closes in conjunction with a driver's accelerator operation is attached.

A surge tank 14 is provided on the downstream side of the throttle valve 12, and the surge tank 14 has a pressure sensor 15 for detecting the internal pressure of the surge tank 14 and outputting the pressure oscillation between the intake air.
Is attached. The surge tank 14 is a tank provided to absorb the pulsation of the intake air pressure flowing through the intake manifold 16, and the internal pressure thereof shows a value corresponding to the amount of air flowing through the intake manifold 16.

The intake manifold 16 communicates with the combustion chamber 17 of each cylinder of the internal combustion engine 10. And
An injector 9 is installed in each intake manifold 16 corresponding to each cylinder.

Further, the combustion chamber 17 of the internal combustion engine 10 is communicated with an unillustrated catalytic converter via an exhaust manifold 19. This catalytic converter is an exhaust gas purification device that is filled with a three-way catalyst, and can purify unburned components and oxides in the exhaust gas discharged from the internal combustion engine 10 to ensure good exhaust emission. It is set up to fit in.

By the way, this three-way catalyst has a characteristic that the exhaust gas can be purified most effectively when the exhaust gas discharged from the internal combustion engine is controlled to be near the stoichiometric air-fuel ratio. Therefore, when purifying the exhaust gas using the catalytic converter, it is necessary to control the air-fuel ratio of the exhaust gas with high accuracy. Therefore, in order to execute the air-fuel ratio feedback control, which is known to be capable of controlling the air-fuel ratio with high accuracy, the exhaust manifold 19 detects the residual oxygen concentration in the exhaust gas and outputs an air-fuel ratio signal. An oxygen sensor 20 is attached.

Further, a water temperature sensor 21 which detects a cooling water temperature of the internal combustion engine 10 and outputs a water temperature signal is attached to an engine block of the internal combustion engine 10. Further, the tip of an ignition plug 22 is projected into the combustion chamber 17 of the internal combustion engine 10, and a distributor 23 is connected to the ignition plug 22.

The distributor 23 outputs the ignition signal from an igniter 24 that generates a high voltage at the timing at which the ignition plug 22 installed in each cylinder of the internal combustion engine 10 should be energized, that is, at the ignition timing of the internal combustion engine 10. It is supplied. The supplied ignition signal is distributed to each cylinder in accordance with the operation of the central shaft 23a that rotates in conjunction with the crankshaft (not shown) of the internal combustion engine 10.

By the way, in the distributor 23,
The pickup fixed to the housing 23a,
In conjunction with the crankshaft (not shown) of the fuel engine 10
With the signal rotor fixed to the rotating central shaft 23b
The cylinder discrimination signals 25 and 26, which are respectively configured, are provided.
ing. These cylinder discrimination sensors 25 and 26 are 720 °.
Cylinder discrimination signal (G₁, G₂Signal)
And G₁Signal and G ₂Only 360 ° CA phase with signal
It is configured so that the output is shifted.

Further, in FIG. 2, reference numeral 27 is a battery mounted on the vehicle, which supplies necessary electric power to an on-vehicle electrical system such as a starter motor 28 for ensuring a starting torque of the internal combustion engine 10. . Starter motor 2 here
8 starts the internal combustion engine 10 by starting the crankshaft from the state in which the internal combustion engine 10 is stopped. Therefore, when the starter motor 28 operates (during cranking), the alternator (not shown), which is a generator, cannot yet exhibit sufficient power generation capacity.

Therefore, while the internal combustion engine 10 is cranked, the starter motor 28 becomes a heavy load on the battery 27, and the battery voltage temporarily drops during cranking. The ignition switch (IG switch) 29 is a switch that brings the internal combustion engine 10 into a startable state. Therefore, by monitoring the output signal of the IG switch 29, it is possible to determine whether the internal combustion engine 10 is being started or stopped.

An electronic control unit (ECU) 30 is an essential part of this embodiment, and realizes the above-mentioned fuel injection means 1, startability estimation means 4 and injection method selection means 5 by executing a program described later. It is a member that does. The configuration will be described below.

The ECU 17 is a central processing unit (CPU) 3
1, read only memory (ROM) 32, random access memory (RAM) 33 and input / output port (I / O)
34, and these are connected through a common bus 35. Here, the I / O 34 has a built-in analog / digital converter (A / D converter), a waveform shaping circuit, etc., converts an input signal into a desired digital signal, and supplies it to the CPU 35 and the like. .

The I / O 34 of this embodiment includes the intake air temperature sensor 11, the throttle sensor 13, and the pressure sensor 1 described above.
5, the oxygen sensor 20, the water temperature sensor 21, the detection signals of the cylinder discrimination sensors 25, 26, the battery voltage signal of the battery 27, the state signal of the IG switch 29, etc. are supplied. Then, from the I / O 34, a fuel injection signal for controlling the opening / closing valve of the injector 9 via an unillustrated drive circuit, an ignition timing signal for controlling the high voltage generation timing in the igniter 24, and the start / stop of the starter motor 28 are operated. A start signal for controlling is output.

In this case, a plurality of injectors 18 are installed corresponding to each cylinder constituting the internal combustion engine 10.
Is supplied with a fuel injection signal from the I / O 34. Therefore, each injector 18 can inject fuel independently from each other.
Whether to inject fuel into all cylinders simultaneously or sequentially in each cylinder can be arbitrarily set by an instruction from the ECU 30.

In the ROM 32, the program of the starting-time injection method discrimination routine, which is a feature of the present invention, is stored.
A program of a synchronous injection (emission priority) routine that realizes the above-mentioned synchronous injection setting means 2 and a program of an asynchronous injection (startability priority) routine that realizes the above-mentioned asynchronous injection setting means 3 and maps necessary for these routines are stored in advance. It is stored.

The operation of the apparatus of this embodiment will be described in detail below in accordance with the contents of these routine processes.

FIG. 3 shows a flow chart of an example of a starting injection timing system discrimination routine which is a main part of the apparatus of this embodiment. This process is a process that is executed only once when the IG switch is switched from off to on. That is,
When this process is started, it is first checked in step 100 whether the internal combustion engine 10 is being started.

If the state signal of the IG switch 29, which was off at the time of the previous processing, is on at the time of the current processing, it is determined that the internal combustion engine 10 is starting, and the routine proceeds to step 110, In cases other than the above, the processing of this time is ended as it is. This routine is a process for selecting the injection method based on the startability of the internal combustion engine 10 at the time of starting, and it is meaningless to execute unless the internal combustion engine 10 is at the time of starting.

If it is determined in step 100 that the engine is starting, the process proceeds to step 110 and the water temperature sensor 21
The cooling water temperature is detected based on the detected value of. Whether or not the internal combustion engine 10 is in a state in which it is easy to start is determined by the vaporization property of the supplied fuel, the viscosity of the lubricating oil, and the like, and these are both captured as a function of temperature. Therefore, the internal combustion engine is determined based on the cooling water temperature. The purpose is to judge the degree of influence that the state of 1 has on startability.

After the cooling water temperature is detected in this manner, the battery voltage is then detected in step 120. This is because the torque exerted when the starter motor 28 operates has a value corresponding to the electric power that the battery 27 can supply to the starter motor 27, and the magnitude of the value greatly affects the startability of the internal combustion engine 10. .

In the present embodiment, the startability of the internal combustion engine 10 is determined by the cooling water temperature and the battery voltage. When these detections are completed, the routine proceeds to step 130, where the cooling water temperature and the battery voltage are used. The startability of the internal combustion engine 10 is estimated with reference to a predetermined map of the fuel injection method to be adopted. In this way, the above step 11
0 to 130 realize the startability estimating means 4 described above.

In this case, the above map can be set as shown in FIG. 4, for example. The map shown in FIG. 4 shows that the internal combustion engine 10 has good startability when the cooling water temperature is high and the battery voltage is relatively low, and when the cooling water temperature is low, the startability is high even when the battery voltage is relatively high. It means that there is a bad case.

After the startability of the internal combustion engine 10 is estimated from the map in this way, the routine proceeds to step 140, where a fuel injection method suitable for the estimated startability is selected. If it is estimated that the startability of the internal combustion engine 10 is good, it is not necessary to pay attention to the startability, so the routine proceeds to step 150, where the exhaust emission priority pattern is selected (emission priority flag). End) and end the process.

On the other hand, when it is estimated that the internal combustion engine 10 is difficult to start, the fuel injection pattern that can improve the startability should be selected.
The process proceeds to 60 and the flag of the startability superiority pattern is set, and the process is ended. In this way, the above steps 140-1
Reference numeral 60 realizes the above-mentioned injection method selection means 5.

In the present embodiment, when the startability priority flag is set, the asynchronous injection method in which fuel is simultaneously injected from the injectors 18 installed in all cylinders regardless of the crank angle, and the emission priority is given. When the flag is set, the synchronous injection method is adopted in which fuel is sequentially injected into each cylinder at a fixed crank angle, and the respective effects are achieved. The respective effects of these injection methods will be described below.

FIG. 5 shows a flowchart of an example of the asynchronous injection routine executed by the ECU 30 when it is estimated that the internal combustion engine 10 is difficult to start. When this routine is started as shown in FIG.
At 00, it is checked whether or not the startability priority flag is set.

This routine is to be executed only when the startability priority flag is set in the injection method discrimination routine shown in FIG. Therefore, if the predetermined flag is not set, the current processing is ended. Then, only when the flag is set, the process proceeds to step 210.

In step 210, it is determined whether or not a predetermined time has elapsed after starting cranking, that is, after starting the energization of the starter motor 28. The purpose is to confirm that cranking has been started without fail before actually injecting fuel, and in this embodiment, 20 ms.
It is supposed to wait for ~ 30ms.

If it is determined in step 210 that the predetermined time has elapsed, the asynchronous injection is started (steps 220 and 230). Here, the asynchronous injection refers to # 1 to # 4 of the internal combustion engine as shown in FIG.
This is a system in which fuel is simultaneously injected into cylinders (FIG. 7B), and has an advantage that fuel injection can be started at the same time as cranking is started without determining the state of each cylinder.

By the way, FIG. 6 shows a starting pattern when the internal combustion engine 10 is stopped in the compression process of the # 1 cylinder. As shown in the figure, when the internal combustion engine stops, due to its operation resistance, one of the cylinders stops at the position where the compression process is started. Therefore, assuming that the cylinder discrimination signals G ₁ and G ₂ are issued at the position shown in FIG. 6C, for example, the crankshaft will move about 90 ° C. after cranking is started.
The crank angle can be recognized at the time of A rotation.

Further, the cylinder discrimination signals G ₁ and G ₂ are shown in FIG.
If it is issued at the time shown in (D), the ECU 30 detects that the crankshaft is about 270 ° C after the start of cranking.
At the time of A rotation, the crank angle can be recognized based on the G ₁ signal. That is, when the two cylinder discrimination signals G ₁ and G ₂ are used as in the present embodiment, no matter which cylinder the internal combustion engine 10 stops in the compression process, if the crankshaft rotates 270 ° CA at the maximum, The process (FIG. 6A) of each cylinder can be recognized.

Further, as shown in FIG. 6B, in the case of asynchronous injection, fuel injection is started at the same time as cranking is started without recognizing the crank angle. Therefore, when the crankshaft rotates 270 ° CA after the start of cranking, one of the cylinders (# 4 cylinder in FIG. 6) is always in the state where the intake stroke is completed. Therefore, when the crankshaft rotates 450 ° CA, there is always a cylinder for which the compression process has ended, and at this point the first explosion can be obtained.

However, in a cylinder in which cranking is started in the middle of the intake stroke, such as cylinder # 3 in FIG. 6, air is already supplied into the combustion chamber 17 at the time when cranking is started. Therefore, sufficient fuel cannot be sucked in the process. Therefore, there is a strong possibility that misfire will occur at 270 ° CA after the start of cranking, and the fuel drawn into this cylinder is highly likely to be exhausted in an unburned state.

The amount of fuel injected by the asynchronous injection is calculated by another subroutine stored in the ROM 32. In the present embodiment, as shown in FIG. 6, in order to ensure good startability, in particular, the first injection amount after the cranking is started is increased, and thereafter, a preset map is used to show the cooling water temperature, the engine speed, etc. The amount calculated with reference to this is the injection amount TAU.

Further, in this embodiment, in order to suppress the influence of the fuel injection timing on each cylinder while simultaneously injecting fuel to all cylinders, the fuel to be supplied during cranking is divided into two. It is configured to eject. Therefore, in FIG. 6, fuel is supplied to the # 1 and # 4 cylinders by TAU / 2 for the intake stroke and the explosion stroke, and TAU / 2 for the # 2 and # 3 cylinders for the compression stroke and the exhaust stroke.

On the other hand, when it is estimated that the internal combustion engine 10 is in a state where it can be easily started in the routine shown in FIG. 3, the ECU 30 injects fuel by the synchronous injection method. FIG. 7 shows a flowchart of an example of the synchronous injection routine executed by the ECU 30. When this routine is started as shown in the figure, first, at step 300, it is checked whether or not the emission priority flag is set.

This routine is to be executed only when the emission priority flag is set in the injection method discrimination routine shown in FIG. Therefore, if the predetermined flag is not set, the current processing is ended. Then, only when the flag is set, the process proceeds to step 310.

In step 310, it is determined whether or not any cylinder discrimination signal is input. This is because the crank angle must be recognized in the synchronous injection method in which fuel is sequentially injected into each cylinder in synchronization with the rotation of the internal combustion engine. When the cylinder discrimination signal of G ₁ or G ₂ is input, the process proceeds to step 320 to inject fuel into the cylinder corresponding to the cylinder discrimination signal G ₁ , G ₂ .

At step 320, it is judged if the fuel injection is the first time for the cylinder. This is because at the time of the first fuel injection, it is necessary to increase the amount of the fuel in consideration of insufficient fuel vaporization and the like.

When the fuel injection is performed for the cylinder for the first time, the routine proceeds to step 330, where the predetermined initial increase is added to the TAU calculated by referring to the map in another subroutine, and the predetermined cylinder is added. Supply to. If it is determined in step 320 that it is not the first time, the process proceeds to step 340, and the calculated TAU is sequentially supplied to each cylinder, and the current process is ended.

By the way, when the two types of cylinder discrimination signals G ₁ and G ₂ are used as described above, the crank angle is recognized by rotating the crankshaft by about 90 ° CA or about 270 ° CA. be able to. In this case, assuming that the fuel can be recognized at the time of 90 ° CA rotation as shown in FIG. 8C, the cylinder corresponding to the fuel at that time (see FIG.
It is injected toward the middle and # 4 cylinders). Therefore, in this case, as in the case of the asynchronous injection described above, a state in which the initial explosion is obtained at 450 ° CA rotation after the start of cranking is ensured.

On the other hand, assuming that the crank angle can be recognized at 270 ° CA as shown in FIG. 8 (E),
At that time, the crankshaft must rotate by 630 ° CA before the cylinder (# 2 cylinder in FIG. 8) supplied with fuel finishes the compression process and obtains the first explosion.

As described above, when the fuel injection is performed by the synchronous injection, unlike the case where the asynchronous injection is performed, the initial explosion may not be obtained in the clan seat after the start of cranking, and the startability is obviously poor. It will be. In particular, the internal combustion engine 1
In a situation where the environmental temperature of 0 is low and cranking can be expected only for a few revolutions, the delay of the initial explosion has a serious influence on the startability of the internal combustion engine.

Furthermore, when the ambient temperature is low,
It is conceivable that the battery voltage will drop below the operating voltage of the ECU 30 due to the power consumption of the starter motor 28 during cranking. Becomes worse.

On the other hand, if the internal combustion engine 10 can be easily started, the delay of the initial explosion does not pose a problem, and the internal combustion engine 10 can be started well after proper cranking. Then, in this case, unlike the case of the asynchronous injection method, the unburned fuel is not exhausted immediately after the start, and it is possible to secure good exhaust emission.

Further, when the synchronous injection is performed from the start, it is not necessary to switch the fuel injection method after the internal combustion engine reaches the idling state, and the air-fuel ratio disturbance due to the injection method switching does not occur. That is, when the internal combustion engine is started by the asynchronous injection, TAU / 2 is supplied to all the cylinders immediately after the start of the internal combustion engine.
In some cases, the fuel may become excessive or insufficient in the amount of AU / 2, whereas in the case where the synchronous injection is performed from the beginning, there is no variation in the fuel injection amount, and a good empty space is always maintained. The fuel ratio can be maintained.

Further, when the internal combustion engine is started by the synchronous injection, the fuel can be supplied when the intake stroke is executed in each cylinder, so that the amount of the fuel adhering to the intake manifold is larger than that in the case of the asynchronous injection. Can be suppressed. As a result, it is possible to reduce the amount of fuel that is increased in the sense of compensating for the fuel that adheres to the inner wall of the intake manifold at the time of cold start, and it is possible to reduce the amount of HC, CO, etc. that are discharged in large amounts with such increase correction. .

For the same reason, when the internal combustion engine 10 is started with the accelerator pedal depressed and the accelerator pedal is returned after the start, a large amount of the adhered fuel is vaporized at once in the case of asynchronous injection. In contrast, the air-fuel ratio is disturbed, whereas when the synchronous injection is performed, the disturbance of the air-fuel ratio is suppressed.

As described above, when the fuel injection is performed by the synchronous injection method, the exhaust emission can be remarkably improved, although the startability is inferior to the case of the asynchronous injection. In view of this, in the present embodiment, the synchronous injection method is used only when the internal combustion engine 10 is in a state where it can be started satisfactorily.

As a result, in the internal combustion engine 10 provided with the device of the present embodiment, the exhaust emission is remarkably improved while ensuring the same startability as the internal combustion engine provided with the conventional starting fuel injection device. Becomes

[0075]

As described above, according to the present invention, if the internal combustion engine is in a difficult state to start, the asynchronous injection method is selected as the fuel injection method at the start, which is equivalent to the conventional start-time fuel injection device. The startability of is secured. If the internal combustion engine is in a state where it can be easily started, a synchronous injection method suitable for ensuring good exhaust emission is adopted as the fuel injection method at the time of starting without unnecessarily improving the startability.

Therefore, the starting-time fuel injection device according to the present invention can always start the internal combustion engine favorably and, in comparison with the conventional starting-time fuel injection device, the emission of exhaust gas discharged at the starting time is remarkably improved. It has the feature that it can be improved.

[Brief description of drawings]

FIG. 1 is a principle diagram of a fuel injection device at startup according to the present invention.

FIG. 2 is an overall view showing a configuration of an embodiment of a fuel injection device at startup according to the present invention.

FIG. 3 is a flowchart of an example of a routine process executed by the device of this embodiment.

FIG. 4 is an example of a map used for estimating the startability of the internal combustion engine in the device of the present embodiment.

FIG. 5 is a flowchart of an example of an asynchronous injection routine executed by the device of this embodiment.

FIG. 6 is a time chart for explaining a fuel injection pattern by asynchronous injection.

FIG. 7 is a flowchart of an example of a synchronous injection routine executed by the device of this embodiment.

FIG. 8 is a time chart for explaining a fuel injection pattern by synchronous injection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection means 2 Synchronous injection setting means 3 Asynchronous injection setting means 4 Startability estimation means 5 Injection method selection means 10 Internal combustion engine 21 Water temperature sensor 25, 26 Cylinder discrimination signal 27 Battery 28 Starter motor 30 Electronic control unit (ECU)

Claims (1)

[Claims] 1. Synchronous injection in which fuel is always injected into each cylinder at the same crank angle in synchronism with the rotation of the internal combustion engine, and for all cylinders regardless of the crank angle, not synchronized with the rotation of the internal combustion engine. A starting-time fuel injection device comprising a fuel injection means for injecting fuel by appropriately switching between asynchronous injection for injecting fuel at the same time, a startability estimation means for estimating startability of the internal combustion engine, and the startability estimation means for A starting-time fuel injection device, comprising: an injection method selecting means for making the fuel injection at the time of starting an asynchronous injection only when it is estimated that the startability of the internal combustion engine is worse than a predetermined level.