JPH11280531A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To effectively improve drivability in idling operation at start-up irrespective of the properties of fuel used. SOLUTION: At the time of starting the engine, the ignition timing is controlled so that the engine speed becomes a target speed. The control value of the fuel injection means is determined from the ignition timing at this time, and the fuel injection means is driven based on the determined control value. by this,
It is possible to improve the drivability during idling at the start regardless of the fuel property.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control technique for an internal combustion engine, and more particularly to a fuel injection control technique for increasing the amount of fuel during a predetermined period after starting the internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, the combustion is not stabilized during a predetermined period after the engine is started, so that the amount of fuel is increased, thereby improving the idling operation after the engine is started. However, since the combustion state of the internal combustion engine changes depending on the properties of the fuel used, it is necessary to control the fuel injection in consideration of the properties of the fuel at the time of starting. In other words, heavy fuel is unlikely to evaporate compared to normal fuel properties, and if the increase in fuel at start-up is always constant, when heavy fuel is used, combustion will not be performed well and idle operation after start-up will not be possible. There is a problem that it is not stable. Therefore, Japanese Patent Application Laid-Open No. 3-281959 discloses that when the engine speed drops below a predetermined value, the fuel increase value is increased, thereby reducing the engine speed even when heavy fuel is used. Prevention techniques are disclosed. According to this technique, it is possible to prevent the engine speed from dropping after starting, regardless of the properties of the fuel used.

[0003]

However, in the above-mentioned prior art, the fuel increase value is increased only when the engine speed drops significantly below a predetermined value. Until the temperature becomes lower, there is a problem that combustion is unstable and drivability is poor. In order to solve this problem, the fuel increase value may be set to be large from the beginning after the start. However, if the fuel increase value is increased from the beginning after the start, the fuel efficiency deteriorates, and this is an excessive fuel increase value, especially when normal fuel is used and combustion is good, resulting in an increase in fuel efficiency and fuel consumption. Disadvantageous in terms of emissions. The present invention has been made in view of such a point, and it is an object of the present invention to effectively improve drivability in idling operation at start-up regardless of the properties of fuel used.

[0004]

A fuel injection control device for an internal combustion engine according to the present invention solves the above-mentioned problems by the following constitution.

That is, the first invention is an ignition timing control means for controlling an ignition timing so that the engine speed becomes a predetermined speed during a predetermined period at the time of starting the engine, and an ignition timing by the ignition timing control means. A control value determining unit that determines a control value for the fuel injection unit based on the control value; and a driving unit that drives the fuel injection unit based on the control value determined by the control value determination unit. According to a second aspect, in the first aspect, the control value determined by the control value determining means is a fuel injection amount. In a third aspect based on the second aspect, the control value determining means is characterized in that when the ignition timing by the ignition timing control means is advanced, the fuel injection amount is increased as compared with when the ignition timing is retarded. Is determined. 4
According to a second aspect, in the first aspect, the control value determined by the control value determining means is a fuel injection timing. In a fifth aspect based on the fourth aspect, the control value determining means is configured to execute the fuel injection timing at which the fuel injection is performed at a timing other than the intake stroke when the ignition timing by the ignition timing control means is on the advanced side of the predetermined ignition timing. And when the ignition timing by the ignition timing control means is retarded from the predetermined ignition timing, the fuel injection timing at which the fuel injection is executed during the intake stroke is determined. 6
The second invention is characterized in that, in the first invention, there is provided fuel property determining means for determining the property of the fuel based on the ignition timing by the ignition timing control means.

[0006]

1 to 5 show a first embodiment in which the present invention is applied to a four-stroke gasoline internal combustion engine. FIG. 1 shows an overall view, 1 is an engine body,
2 is a piston, 3 is a combustion chamber, 4 is a spark plug disposed in the combustion chamber, 5 is an intake valve, 6 is an intake port, 7 is an exhaust valve, 8
Indicates exhaust ports, respectively. The intake port 6 is connected to a surge tank 10 via an intake branch 9, and a fuel injection valve 11 is attached to each intake branch 9. The surge tank 10 is connected to an air cleaner 14 via an intake duct 12 and an air flow meter 13, and a throttle valve 15 is arranged in the intake duct 12.

The electronic control unit 20 is composed of a digital computer, and a ROM (read only memory) 22, a RAM (random access memory) 23, a CPU (microprocessor) 24, and an input port 25 interconnected by a bidirectional bus 21. And an output port 26. The air flow meter 13 generates a voltage proportional to the mass flow rate of the intake air. This output voltage is input to the input port via the corresponding AD converter 27. An idle switch 16 for generating an output signal when the throttle valve 15 is at the fully closed position is connected to the throttle valve 15, and the output signal of the idle switch 16 is input to an input port 25. A temperature sensor 17 for generating an output voltage proportional to the temperature of the engine cooling water is attached to the engine body 1, and the output voltage of the temperature sensor 17 is input to an input port 25 via a corresponding AD converter 27. In addition, input port 2
An output signal of a rotation speed sensor 29 representing an engine rotation speed is input to 5. The atmospheric pressure sensor 30 generates an output voltage proportional to the atmospheric pressure, and the output voltage is input to the input port 25 via the corresponding AD converter 27. On the other hand, the output port 26 is connected to the ignition plug 4 and the fuel injection valve 11 via a corresponding drive circuit 28, respectively. An exhaust pipe 18 is connected to the exhaust port 8, and the exhaust gas discharged from the combustion chamber is introduced into a catalytic converter (not shown) through the exhaust port 8 and the exhaust pipe 18 and purified. An oxygen concentration sensor 19 detects the oxygen concentration in the exhaust gas, and generates an output voltage proportional to the oxygen concentration in the exhaust gas. The output voltage of the oxygen concentration sensor 19 is input to the input port 25 via the AD converter 27.

[0008] The electronic control unit 20 includes a rotational speed sensor 2.
9, the operation state of the engine is detected in accordance with the outputs from the atmosphere sensor 30, the idle switch 16, the air flow meter 13, and the oxygen concentration sensor 19, and the driving of the spark plug 4 and the fuel injection valve 11 is performed by referring to a map obtained in advance. The circuit 28 is driven. Therefore, the electronic control unit 20 functions as control means for controlling the ignition timing of the ignition plug 4 and also functions as control means for controlling the fuel injection amount and the fuel injection timing by the fuel injection valve 11.

Next, a control routine for calculating an increase correction value of the fuel injection amount at the time of starting will be described with reference to FIG. Referring to FIG. 2, first, at step 100, it is determined whether or not the engine is at the start. When the engine is being started, the process proceeds to step 101. On the other hand, when the engine is not being started, the control routine is ended. If an affirmative determination is made in step 100, a counter T, which will be described later, is reset to 0 in step 101, and then the routine proceeds to step 102, where it is determined whether or not the engine is cold. If the engine is cold, an affirmative determination is made and the routine proceeds to step 103, and if a negative determination is made the present control routine is terminated. Here, whether or not the engine is cold is determined based on the engine cooling water temperature detected by the output of the temperature sensor 17, and when the engine cooling water temperature is equal to or lower than a predetermined value, it is determined that the engine is cold. . In step 103, it is further determined whether or not the air-fuel ratio feedback is being performed. Here, the air-fuel ratio feedback is being performed.
Means an operation state in which the fuel injection amount supplied from the fuel injection valve 11 in accordance with the output of the electronic control unit 20 is feedback-controlled by the electronic control unit 20. Then, during a predetermined period after the start, the execution condition of the air-fuel ratio feedback is not satisfied, and the process proceeds to step 104.
Even after the start, if the air-fuel ratio feedback condition is satisfied after a predetermined period and other conditions are satisfied, the air-fuel ratio feedback control is executed, and step 103 is executed.
And the control routine ends. In step 104, it is determined whether or not the idle switch 16 is ON, that is, whether or not a signal is output from the idle switch 16. As described above, the idle switch 16 outputs a signal when the throttle valve 15 is fully closed.
An affirmative determination in step 104 means that the engine is in an idle operation state. If an affirmative determination is made in step 104, that is, if the vehicle is idling, the process proceeds to step 105. Conversely, if a negative determination is made, it is determined that the vehicle is not idle, and the control routine ends.

In step 105, ignition timing feedback control is executed. The ignition timing feedback control is executed by a subroutine shown in FIG.
Generally, the ignition timing is advanced or retarded so that the engine speed falls within a predetermined range. Referring to FIG. 3, first, at step 201, a deviation DNE between the engine speed NE and the target engine speed NE0 at the time of cold idling is calculated. Next, the routine proceeds to step 202, where it is determined whether or not the deviation DNE is a positive value. When the deviation DNE is a positive value, since the engine speed NE is larger than the target speed NE0, the process proceeds to step 203 to retard the ignition timing θ so that the engine speed NE approaches the target speed NE0. . In step 203, the current ignition timing θ is determined by the deviation DN.
The value retarded by the function value corresponding to E is used for the subsequent ignition timing θ.
Set as Then, when the ignition timing is retarded by the ignition timing θ set in step 203, the output torque of the engine decreases, and therefore, the engine speed NE decreases and approaches the target engine speed NE0. Step 20
If a negative determination is made in step 2, the engine speed NE is smaller than the target engine speed NE0, and the ignition timing θ advanced in step 204 is set to increase the engine torque. As a result, the engine speed NE approaches the target speed NE0.

Returning to FIG. 2, when the ignition timing is controlled at step 105, the routine proceeds to step 106, where it is determined whether or not the engine speed NE is within a predetermined range centered on the target engine speed NE0 during cold idling. Is determined. Engine speed N
When E is within the predetermined range centered on the target engine speed NE0 during cold idling, the routine proceeds to step 107, and when the engine rotational speed is out of the predetermined range, the routine proceeds to step 113. Therefore, if the engine speed NE is not within the predetermined range even if the ignition timing is controlled in step 105, a counter T described later is reset to 0, and step 10
Returning to step 5, the ignition timing feedback control is repeatedly executed, and the routine proceeds to step 107 only when the engine speed NE falls within a predetermined range. That is, by executing steps 105 and 106, the engine speed is controlled to be within the predetermined range. If the engine speed NE falls within the predetermined range, step 107 is executed.
Then, the counter T is incremented by one. Then, the routine proceeds to step 108, where the ignition timing θ at that time is stored in the RAM 23 as a storage value A (T). Here, when step 108 is executed for the first time after an affirmative determination is made in step 105, the counter T is 1, and the ignition timing θ at that time is stored in the RAM 23 as a storage value A (1). Each time step 107 is executed without resetting the counter T to 0 in step 113, the counter T is incremented by one, and the ignition timing θ at that time is stored in the RAM 23 as a stored value A (T) corresponding to the counter value. It is memorized. Next, the routine proceeds to step 109, where it is determined whether or not the counter T is larger than a predetermined value T0. When the counter T is equal to or smaller than the predetermined value T0, the process returns to Step 105, and when the counter T is larger than the predetermined value T0, the process proceeds to Step 110. In other words, if the ignition timing feedback control in step 105 is executed and the engine speed NE does not continue for a predetermined period even when the engine speed NE falls within a predetermined range, step 1 is executed.
Returning to step 05, the routine proceeds to step 110 when the engine speed NE is within the predetermined range for a predetermined period.

In step 110, an average value AVθ of the stored values A (T) is calculated. That is, when the engine speed NE continuously falls within the predetermined range for the predetermined period by the ignition timing feedback control executed in step 105,
An average value of the ignition timing controlled at that time is calculated. Then, the routine proceeds to step 111, where the increase correction value α is calculated using the map shown in FIG. Since the ignition timing θ has a positive value on the advance side and a negative value on the retard side with respect to the reference ignition timing as a reference, the stored value AVθ also has a positive or negative value with respect to the reference ignition timing. Therefore, as shown in FIG. 4, the stored value AVθ has a positive / negative area, and in step 111, the fuel increase correction value α corresponding to the stored value AVθ is calculated. Here, the increase correction value α is set so as to be able to take both a positive value and a negative value corresponding to the case of increasing the fuel increase value and the case of decreasing the fuel increase value. Then, when the increase correction value α is calculated, the increase correction flag F is set to 1 in step 112, and the control routine ends.

FIG. 5 shows a calculation routine for calculating the fuel injection amount at the time of starting. First, at step 301, it is determined whether or not 1 is set to the increase correction flag F.
If the increase correction flag F is not set to 1, the increase correction value α has not yet been calculated, and the process proceeds to step 306, where the reference injection amount τ0 is increased by a predetermined ratio β (for example, 1.1). Is set as the fuel injection amount τ, and the control routine ends. In this case, the fuel injection amount τ at the time of starting is set to a value obtained by increasing a predetermined amount of fuel according to the predetermined ratio β. Next, when 1 is set to the increase correction flag F, the routine proceeds to step 302, where the time constant TIM is set to a predetermined amount K.
(K <0.1) is incremented. Then, the routine proceeds to step 303, where it is determined whether or not the time constant TIM is 1.0 or more. If the time constant TIM is equal to or greater than 1.0, the process proceeds to step 304, where the time constant TIM is set to 1.0 and step 30
If the time constant TIM is smaller than 1.0, the process proceeds to step 305 without going through step 304. In step 305, the fuel injection amount τ is calculated based on the reference injection τ0 by correcting the predetermined ratio β with the increase correction amount α in consideration of the time constant TIM. Therefore, when 1 is not set in the flag F, the fuel injection amount τ is set to a value in which the fuel is increased by an amount corresponding to the predetermined ratio β, and when 1 is set in the flag F, the increase correction value α is reflected. Is corrected to the increased value. At this time, even if the flag F is set to 1, the fuel injection amount is not immediately corrected to the increase value reflecting the increase correction value α, but the increase correction value α is gradually reflected by the influence of the time constant TIM. Will be.

The operation of the embodiment constructed as described above will be described with reference to FIGS. FIG. 6 shows a case where a normal good fuel is used, and FIG. 7 shows a case where a bad fuel such as a heavy fuel is used. First, a case where a high quality fuel is used will be described with reference to FIG. First at time t1
When the cranking is started and the engine is started, an initial explosion occurs at time t2. Thereafter, the fuel injection amount increase value initially set (the increase value corresponding to the predetermined ratio β)
In some cases, the engine speed NE may be larger than the target engine speed NE0. However, by executing the ignition timing feedback control shown in FIG. 3, the ignition timing is retarded to reduce the torque of the engine. As a result, the engine speed NE becomes the target engine speed NE due to the retardation of the ignition timing.
Close to zero. On the other hand, when the engine speed NE is continuously controlled within a predetermined range around the target engine speed NE0 (period from time t3 to time t4), the average ignition timing A
Vθ is calculated. When the average value AVθ is calculated, an increase correction value α of the fuel increase value is calculated based on the map shown in FIG. 4. At this time, the average value AVθ is a negative value on the retard side, and The value α is calculated as a negative value. After the increase correction value α is calculated, the increase correction value α is reflected in the fuel increase value by the fuel injection amount calculation routine at the start shown in FIG. 5, and in this case, the fuel increase value is decreased. Will be. At this time, the increase correction value α is gradually reflected by the influence of the time constant TIM, so that the fuel increase value gradually decreases (period from time t4 to time t5). On the other hand, since the engine torque gradually decreases because the fuel increase value is gradually reduced, the ignition timing is gradually advanced in order to maintain the engine speed NE at the target speed NE0. As a result, at time t5, the fuel increase value is changed to a value smaller than the initial value. Therefore, the fuel increase value can be changed to a small value while maintaining the target rotation speed, and the fuel efficiency and emission are improved. In this case, before the time t5 is reached, the ignition timing is retarded, and the effect of increasing the exhaust gas temperature and promoting the warm-up of the catalyst is obtained.

Next, a case in which poor fuel is used will be described with reference to FIG. First, at the time t6, the cranking is started to start the engine, and then, at the time t7, the first explosion occurs. Thereafter, at the initially set fuel injection amount increase value (the increase value corresponding to the predetermined ratio β), the engine speed may be lower than the target speed NE0, and in this case, the ignition timing increases the engine torque. It is advanced to make it. When the engine speed is continuously controlled within a predetermined range around the target engine speed NE0 by the advance of the ignition timing (period from time t8 to time t9), the average value of the ignition timing at this time AVθ Is calculated. Then, the increase correction value α of the fuel increase value is calculated based on the map shown in FIG. At this time, the average value AVθ is a positive value on the advance side, and the increase correction value α is calculated as a positive value. When the increase correction value α is calculated, the increase correction value α is reflected on the fuel increase value by the fuel injection amount calculation routine at the start of FIG. 5, and in this case, the fuel increase value increases. At this time, the increase correction value α is gradually reflected by the influence of the time constant TIM, so that the fuel increase value gradually increases (period from time t9 to time t10). On the other hand, since the fuel increase value is gradually increased and the engine torque is gradually increased, the ignition timing is gradually retarded to maintain the engine speed at the target engine speed NE0. As a result, at time t10, the fuel increase value is changed to a value larger than the initial value, and the engine speed becomes the target engine speed N
It is maintained at E0. As a result, even when poor fuel is used, the engine speed can be controlled to the target speed NE0 and drivability can be sufficiently ensured. Further, even before the fuel increase value is changed at time t10, the engine speed is maintained at the target speed NE0 by controlling the ignition timing, the intake pipe negative pressure is sufficiently ensured, and the fuel is injected from the fuel injection valve 11. Drivability is sufficiently ensured even before the fuel increase value is changed, for example, the atomization of the fuel to be performed is improved.

When the average value AVθ is a positive value, it indicates that poor fuel is being used, and when the average value AVθ is a negative value, it indicates that good quality fuel is being used. Therefore, in other words, AVθ represents the fuel property, and it can be said that the calculation step of AVθ functions as fuel property detecting means. The calculation process of AVθ can be said to be a detection period for detecting the property of the fuel.

As described above, in the present embodiment, when good quality fuel is used, the initially set fuel increase value can be reduced while the engine speed is set to the target speed.
As a result, fuel efficiency and emissions can be improved, and when poor fuel is used, the initially set fuel increase value can be increased and the engine speed can be adjusted to the target speed so that drivability can be improved and bad fuel is used. The engine speed is maintained at the target engine speed NE0 by the ignition timing feedback control even in the period before the detection of the presence of the vehicle, and the drivability in this period can be improved.

In this embodiment, the provision of the counter T allows the ignition timing .theta.
23, and the average value AVθ is calculated to calculate the fuel increase correction value α. However, without providing the counter T (without calculating the average value AVθ), the ignition timing feedback control shown in FIG. Ignition timing θ set by
May be used to calculate the fuel increase correction value α immediately.

Next, a second embodiment of the present invention will be described with reference to FIG. In the first embodiment, the increase value of the fuel injection amount is changed, whereas the present embodiment is different in that the fuel injection timing is changed. The basic configuration is the same as that of the first embodiment and is shown in FIG. Referring to FIG. 8, first, at step 400, it is determined whether or not it is at the time of starting. If it is during startup, the process proceeds to step 401, and if it is not during startup, this control routine is ended. If an affirmative determination is made in step 400, a counter T described later is reset to 0 in step 401. Next, the routine proceeds to step 402, where it is determined whether or not the engine is cold. If the engine is cold, an affirmative determination is made and the process proceeds to step 403. If a negative determination is made, the present control routine ends. Here, whether or not the engine is cold is determined based on the engine cooling water temperature detected by the output of the temperature sensor 17, and when the engine cooling water temperature is equal to or lower than a predetermined value, it is determined that the engine is cold. . In step 403, it is further determined whether or not the air-fuel ratio feedback is being performed. Here, “during the air-fuel ratio feedback” refers to an operation state in which the fuel injection amount supplied from the fuel injection valve 11 in response to the output of the oxygen concentration sensor 19 is feedback-controlled by the electronic control unit 20. Then, during a predetermined period after the start, the execution condition of the air-fuel ratio feedback is not satisfied, and the process proceeds to step 404. Conversely, even after the start, the air-fuel ratio feedback is performed after the predetermined period is satisfied and other conditions are satisfied. If the condition is satisfied, the air-fuel ratio feedback control is being executed, and the result of the determination in step 403 is affirmative, and the control routine ends. Step 404
Then, it is determined whether or not the idle switch 16 is ON. If an affirmative determination is made in step 404, that is, if the vehicle is idling, the process proceeds to step 405. Conversely, if a negative determination is made, it is determined that the vehicle is not idle, and the present control routine ends.

In step 405, ignition timing feedback control is executed. The ignition timing feedback control is executed by the subroutine shown in FIG. 3 similarly to the first embodiment, and the detailed description is omitted here.
When the ignition timing is controlled in step 405, the process proceeds to step 406, in which it is determined whether the engine speed NE is within a predetermined range centered on the target engine speed NE0 at the time of cold idling. If the engine speed NE is within a predetermined range around the target engine speed NE0 at the time of cold idling, the process proceeds to step 407, and if the engine speed is out of the predetermined range, the process proceeds to step 414. Therefore, if the engine speed NE is not within the predetermined range even if the ignition timing is controlled in step 405, the counter T, which will be described later, is reset to 0, and the process returns to step 405 to repeatedly execute the ignition timing feedback control. When the value falls within the predetermined range, the process proceeds to step 407 for the first time. That is, by executing steps 405 and 406, the engine speed is controlled to be within the predetermined range.

If the engine speed NE falls within the predetermined range, the routine proceeds to step 407, where the counter T is incremented by one. Then, the routine proceeds to step 408, where the ignition timing θ at that time is stored in the RAM 23 as a storage value A (T). Here, when step 408 is executed for the first time after a positive determination is made in step 406, the counter T is 1, and the ignition timing θ at that time is stored in the RAM as a stored value A (1).
23. Then, the counter T is set to step 41
Each time step 407 is executed without being reset to 0 in step 4, the counter T is incremented by 1 and the ignition timing θ at that time is stored in the RAM 23 as a storage value A (T) corresponding to the counter value. Next, proceed to step 409,
It is determined whether the counter T is larger than a predetermined value T0. When the counter T is equal to or smaller than the predetermined value T0, the process returns to Step 405, and when the counter T is larger than the predetermined value T0, the process proceeds to Step 410. That is, if the ignition timing feedback control of step 405 is executed and the engine speed NE does not continue for a predetermined period even when the engine speed NE falls within a predetermined range, the process returns to step 405, and the engine speed NE continues for a predetermined period and continues If within range, step 410
Proceed to.

In step 410, an average value AVθ of the stored values A (T) is calculated. That is, when the engine speed NE continuously falls within a predetermined range for a predetermined period due to the ignition timing feedback control executed in step 405,
An average value of the ignition timing controlled at that time is calculated. Since the ignition timing θ has a positive value on the advance side and a negative value on the retard side with respect to the reference ignition timing as a reference, the stored value AVθ
Also takes a positive or negative value with respect to the reference ignition timing. Next, the routine proceeds to step 411, where it is determined whether or not AVθ is a negative value. When it is determined in step 411 that AVθ is a negative value, the process proceeds to step 412, and the fuel injection is set to intake asynchronous injection control. Here, the intake-asynchronous injection control refers to fuel-injection control in which fuel injection timing is determined so that fuel injection is performed when the intake valve 5 is closed. If it is determined in step 411 that AVθ is a positive value, the flow advances to step 413 to set fuel injection to intake synchronous injection control. Here, the intake synchronous injection refers to a fuel injection timing that determines the fuel injection timing so that the fuel injection is performed when the intake valve 5 is opened. In the present embodiment, the fuel injection timing is set to the intake asynchronous injection control initially after the start before the fuel injection timing is set in step 412 or 413.

Next, the operation of the present embodiment will be described with reference to FIGS. FIG. 9 shows a case in which ordinary good fuel is used, and FIG. 10 shows a case in which inferior fuel such as heavy fuel is used. First, a case where a high quality fuel is used will be described with reference to FIG. First, at the time t1, cranking is started and the engine is started.
The first explosion occurs at 2. Thereafter, the engine speed NE may become larger than the target engine speed NE0 at the initially set fuel injection amount increase value (the increase value corresponding to the predetermined ratio β). However, by executing the ignition timing feedback control shown in FIG. 3, the ignition timing is retarded to reduce the torque of the engine. When the ignition timing is retarded, the engine speed NE approaches the target speed NE0. The engine speed NE
Is continuously controlled within a predetermined range around the target rotational speed NE0 (section from time t3 to time t4), the average value AVθ of the ignition timing is calculated. As described above, when high quality fuel is used, the ignition timing is retarded, and at this time, the average value AVθ takes a negative value. Therefore, the fuel injection is set to the intake asynchronous control by the control routine of FIG. As a result, the air-fuel mixture sufficiently vaporized in the intake port 6 can be supplied to the fuel chamber 3 and good combustion can be performed.

Next, a case where a poor fuel is used will be described with reference to FIG. First, cranking is started at time t5 and engine start is started, and then at time t6
The first explosion occurs at. Thereafter, the engine speed NE may become smaller than the target engine speed NE0 at the initially set fuel injection amount increase value (the increase value corresponding to the predetermined ratio β). In this case, the ignition timing is set to the engine torque. It is advanced to rise. If the engine speed NE is continuously controlled within a predetermined range around the target engine speed NE0 by the advance of the ignition timing (section from time t7 to time t8), the average value of the ignition timing at this time is obtained. AVθ is calculated. At this time, the average value AVθ is a positive value on the advance side, and therefore, the fuel injection is set to the intake synchronous injection. Inferior fuel such as heavy fuel is unlikely to evaporate, and if the asynchronous intake injection control is executed, the amount of deposited fuel at the intake port 6 increases and combustion deteriorates. Since the injection control is executed, deterioration of combustion can be prevented.
Also in the present embodiment, as in the first embodiment, when the average value AVθ is a positive value, it indicates that a poor fuel is used, and when the average value AVθ is a negative value, good quality is obtained. Indicates that fuel is being used. Therefore, in other words, AVθ represents the fuel property, and A
It can be said that the calculation step of Vθ functions as fuel property detection means. Also, the calculation process of AVθ can be said to be a fuel property detection period.

As described above, according to the present embodiment, it is possible to appropriately switch between the intake asynchronous injection and the intake synchronous injection according to the fuel property, and it is possible to improve the drivability in the idling operation at the time of starting. The engine speed is maintained at the target speed by the ignition timing feedback control even in the period before the detection of the use of the inferior fuel, and the drivability in this period can be improved.

In the second embodiment of the present invention, the fuel injection timing is switched between the intake asynchronous injection control and the intake synchronous injection control. However, the injection in the intake synchronous injection control is performed only as the intake synchronous injection control. The timing may be switched. In this case, when the average value AVθ (or the ignition timing θ at the time of the ignition timing feedback control when the average value AVθ is not calculated) is positive (that is, when it is detected that the inferior fuel is being used), the average value AVθ is obtained. (Or when the average value AVθ is not calculated, the injection timing is set at the intake bottom dead center compared to when the ignition timing θ during the ignition timing feedback control is negative (that is, when it is detected that good quality fuel is being used). I just need to delay it. In this way, when poor fuel is used, the amount of fuel adhering to the combustion chamber wall surface can be reduced, and combustion can be improved. Also in the case of a so-called direct injection internal combustion engine in which fuel is directly injected into the combustion chamber, the average value AVθ (or the ignition timing θ during the ignition timing feedback control when the average value AVθ is not calculated) is positive as described above. (That is, when it is detected that inferior fuel is used), the average value AVθ
(Or when the average value AVθ is not calculated, the injection timing is set at the intake bottom dead center compared to when the ignition timing θ during the ignition timing feedback control is negative (that is, when it is detected that good quality fuel is being used). I just need to delay it.

[0027]

According to the present invention, drivability in idling operation at the time of starting can be effectively improved regardless of the properties of the fuel used.

[Brief description of the drawings]

FIG. 1 is an overall view of an internal combustion engine to which the present invention is applied.

FIG. 2 is a flowchart for calculating an increase correction value according to the first embodiment of the present invention.

FIG. 3 is a flowchart of ignition timing feedback control according to the first embodiment of the present invention.

FIG. 4 is a map for calculating an increase correction value according to the first embodiment of the present invention.

FIG. 5 is a flowchart for calculating a fuel injection amount according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating an operation when a high quality fuel is used according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating an operation when a poor fuel is used in the first embodiment of the present invention.

FIG. 8 is a flowchart illustrating control according to the second embodiment of the present invention.

FIG. 9 is a diagram illustrating an operation when a high quality fuel is used according to the second embodiment of the present invention.

FIG. 10 is a diagram illustrating an operation when a poor fuel is used according to the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 4 ... Spark plug 5 ... Intake valve 6 ... Intake port 11 ... Fuel injection valve 19 ... Oxygen concentration sensor

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI F02P 5/15 F02P 5/15 E

Claims (6)

[Claims] 1. An ignition timing control means for controlling an ignition timing so that an engine rotation speed becomes a predetermined rotation speed during a predetermined period when the engine is started, and a control for the fuel injection means based on the ignition timing by the ignition timing control means. A fuel injection control device for an internal combustion engine, comprising: control value determining means for determining a value; and driving means for driving the fuel injection means based on the control value determined by the control value determining means. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the control value determined by the control value determining means is a fuel injection amount. 3. The control value determination means determines an increased fuel injection amount when the ignition timing by the ignition timing control means is advanced compared to when the ignition timing is retarded. The fuel injection control device for an internal combustion engine according to claim 2, wherein: 4. The control value determined by the control value determination means is a fuel injection timing.
3. The fuel injection control device for an internal combustion engine according to claim 1. 5. The control value determining means determines a fuel injection timing at which fuel injection is performed at a timing other than the intake stroke when the ignition timing by the ignition timing control means is retarded from a predetermined ignition timing. 5. The internal combustion engine according to claim 4, wherein when the ignition timing by said ignition timing control means is on the advance side of a predetermined ignition timing, a fuel injection timing at which fuel injection is performed during a suction stroke is determined. Engine fuel injection control device. 6. The fuel injection control device for an internal combustion engine according to claim 1, further comprising fuel property determining means for determining a property of fuel based on an ignition timing by said ignition timing control means.