JP2000352335A - Fuel injection control unit for in-cylinder injection type spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control unit for an in-cylinder injection type spark ignition engine free from back fire. SOLUTION: An engine 10 is provided with a main fuel injection valve 21 for injecting fuel directly into a combustion chamber 14 and an auxiliary fuel injection valve 26 for injecting fuel into a surge tank 12 comprising an intake passage 11. When the engine starts and temperature of cooling water is at a prescribed degree or less, fuel is injected from the auxiliary fuel injection valve 26 as well as from the main fuel injection valve 21. An electronic control device 32 prohibits fuel injection from the auxiliary fuel injection valve 26 and increases the fuel injection volume from the main fuel injection valve 21 when the engine started and a throttle valve opening is at prescribed degree or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder injection spark ignition having a main fuel injection valve for injecting fuel into an engine combustion chamber and an auxiliary fuel injection valve for injecting fuel into an intake passage when the engine is started. The present invention relates to a fuel injection control device for an internal combustion engine.

[0002]

2. Description of the Related Art In a spark ignition type internal combustion engine in which fuel is directly injected into an engine combustion chamber (in a cylinder), fuel is injected into an intake passage in addition to a main fuel injection valve for in-cylinder injection. Conventionally, an auxiliary fuel injection valve is known (for example, Japanese Patent Application Laid-Open Nos.
-176574). In such an internal combustion engine,
By injecting a part of the fuel necessary for starting the engine from the auxiliary fuel injection valve, sufficiently mixing it with the intake air flowing through the intake passage, vaporizing it, and introducing it into the engine combustion chamber, the engine can be used in cold conditions. Also ensure good engine startability.

[0003]

In a direct injection type internal combustion engine, fuel is pressurized to a high pressure using an engine driven high pressure pump and supplied to a fuel injection valve. At times, the fuel is not pressurized by this high-pressure pump or the pressurization is not sufficient,
The fuel injection pressure decreases and the particle size of the fuel spray increases. For this reason, the ratio of the fuel adhering to the top of the engine piston and the inner wall of the engine combustion chamber among the fuel injected from the main fuel injection valve into the engine combustion chamber increases. Further, when the temperature in the engine combustion chamber is low as in the case of a cold start, the vaporization of the fuel spray is not easily promoted, and the diffusion of the fuel in the combustion chamber becomes insufficient.

As a result, only part of the fuel supplied from the main fuel injection valve and the auxiliary fuel injection valve into the engine combustion chamber is used for actual combustion, and the combustion air-fuel ratio (actually used for combustion) is reduced. (The ratio of the amount of intake air introduced into the engine combustion chamber to the amount of fuel) becomes lean (increases). When the amount of intake air introduced into the engine combustion chamber increases with an increase in the throttle opening or the like, the degree of leaning of the combustion air-fuel ratio further increases.

[0005] When the combustion air-fuel ratio becomes lean as described above, the combustion becomes slower, and the period from the time when the air-fuel mixture is ignited to the time when the combustion ends is increased. As a result, combustion is continued until the intake valve opens, and when the valve opens, the flame remaining in the engine combustion chamber becomes mixed with the air-fuel mixture in the intake passage formed by the fuel injection of the auxiliary fuel injection valve. There was a risk of ignition. Such a phenomenon is generally called a backfire, and contributes to a decrease in durability of an intake system component such as an intake pipe.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel injection control device for a direct injection type spark ignition internal combustion engine capable of suppressing the occurrence of backfire. is there.

[0007]

The means for achieving the above object and the effects thereof will be described below. According to the first aspect of the present invention, a direct injection spark ignition internal combustion engine including a main fuel injection valve for injecting fuel into an engine combustion chamber and an auxiliary fuel injection valve for injecting fuel into an intake passage at the time of engine startup. In this fuel injection control device, the degree of leaning of the combustion air-fuel ratio in the engine combustion chamber is monitored, and the fuel injection amount of the auxiliary fuel injection valve is limited based on the leaning degree.

According to the above construction, when the degree of leaning of the combustion air-fuel ratio is large and the combustion of the air-fuel mixture in the engine combustion chamber becomes slow, the fuel injection of the auxiliary fuel injection valve is stopped or the fuel injection amount is reduced. By limiting the fuel injection amount of the valve, such as by reducing the amount, the occurrence of backfire can be suppressed.

The combustion air-fuel ratio is determined by the amount of intake air introduced into the engine combustion chamber with respect to the amount of fuel actually supplied for combustion among the fuel injected from the main fuel injection valve and the auxiliary fuel injection valve. The lean degree can be monitored based on, for example, the intake air amount or the temperature in the engine combustion chamber estimated from the engine cooling water temperature.

According to the second aspect of the present invention, an in-cylinder injection spark having a main fuel injection valve for injecting fuel into the engine combustion chamber and an auxiliary fuel injection valve for injecting fuel into the intake passage at the time of engine start. In a fuel injection control device for an ignition internal combustion engine,
An auxiliary fuel injection inhibiting means for inhibiting fuel injection of the auxiliary fuel injection valve when an opening of a throttle valve for adjusting an amount of intake air introduced into the engine combustion chamber is larger than a predetermined opening is provided. .

According to the above configuration, when the opening of the throttle valve is larger than the predetermined opening, the fuel injection of the auxiliary fuel injection valve is prohibited, so that no air-fuel mixture is generated in the intake passage, and the intake air is sucked through the passage. Only air flows. Therefore, the degree of leaning of the combustion air-fuel ratio increases with an increase in the amount of intake air, and the occurrence of backfire can be reliably suppressed even in a state where the combustion of the air-fuel mixture in the engine combustion chamber is slow. Become like

When the fuel injection of the auxiliary fuel injection valve is prohibited as described above, the startability of the engine is reduced. As a result, the start is not completed, and the fuel injected from the main fuel injection valve is not burned. May adhere to the wall. Therefore, when restarting the engine, the combustion air-fuel ratio in the engine combustion chamber becomes excessively rich due to the vaporization of the fuel attached to the wall of the engine combustion chamber at the time of the previous start, and the engine startability at the time of such restarting is deteriorated. There is a risk that it will.

Therefore, according to a third aspect of the present invention, in the fuel injection control apparatus for a direct injection type spark ignition internal combustion engine according to the second aspect, the auxiliary fuel injection prohibiting means causes fuel injection of the auxiliary fuel injection valve. Further, main fuel injection prohibiting means for prohibiting fuel injection of the main fuel injection valve when is prohibited.

According to the above configuration, in addition to the functions and effects of the invention described in the second aspect, it is possible to suppress the deterioration of the engine startability at the time of restarting as described above.

According to a fourth aspect of the present invention, in the fuel injection control device for a direct injection type spark ignition internal combustion engine according to the second aspect, the auxiliary fuel injection prohibiting means prohibits the fuel injection of the auxiliary fuel injection valve. Main fuel injection increasing means for increasing the fuel injection amount of the main fuel injection valve when the operation is performed.

According to the above configuration, in addition to the functions and effects of the invention described in claim 2, it is possible to suppress the deterioration of the engine startability due to the prohibition of the fuel injection of the auxiliary fuel injection valve. Become.

According to a fifth aspect of the present invention, there is provided an in-cylinder injection type spark having a main fuel injection valve for injecting fuel into an engine combustion chamber and an auxiliary fuel injection valve for injecting fuel into an intake passage when the engine is started. In a fuel injection control device for an ignition internal combustion engine,
An auxiliary fuel injection reducing means for reducing the fuel injection amount of the auxiliary fuel injection valve when an opening of a throttle valve for adjusting an amount of intake air introduced into the engine combustion chamber is larger than a predetermined opening. I have.

According to the above configuration, when the opening of the throttle valve is larger than the predetermined opening, the fuel injection amount of the auxiliary fuel injection valve is reduced, so that the fuel concentration of the mixture generated in the intake passage is low. It will be suppressed. Therefore,
The flame in the engine combustion chamber ignites the air-fuel mixture in the intake passage even when the air-fuel ratio in the combustion air becomes lean with the increase of the intake air amount and the combustion of the air-fuel mixture in the engine combustion chamber becomes slow. And the occurrence of backfire can be suppressed.

According to a sixth aspect of the present invention, in the fuel injection control device for a direct injection type spark ignition internal combustion engine according to the fifth aspect, the auxiliary fuel injection amount is reduced by the auxiliary fuel injection reducing means. Main fuel injection increasing means for increasing the fuel injection amount of the main fuel injection valve when the amount is reduced is further provided.

According to the above configuration, in addition to the functions and effects of the invention described in claim 5, it is possible to suppress the deterioration of the engine startability due to the decrease in the fuel injection amount of the auxiliary fuel injection valve. become.

According to a seventh aspect of the present invention, in the fuel injection control apparatus for a direct injection type spark ignition internal combustion engine according to the sixth aspect, the auxiliary fuel injection reducing means increases as the opening of the throttle valve increases. The degree of decrease in the amount of fuel injection of the auxiliary fuel injection valve is set to be large, and the main fuel injection increasing means sets the degree of increase in the amount of fuel injection of the main fuel injection valve in accordance with the degree of decrease in the amount of fuel injection of the auxiliary fuel injection valve. Is set.

According to the above configuration, in addition to the effect of the invention described in claim 6, the degree of leaning of the combustion air-fuel ratio increases as the amount of intake air introduced into the engine combustion chamber increases. The lower the combustion speed of the mixture in the engine combustion chamber, that is, the more easily the flame in the engine combustion chamber ignites the mixture in the intake passage, the lower the fuel concentration of the mixture becomes. . In addition, since the degree of increase in the amount of fuel injection of the main fuel injection valve is set according to the degree of reduction in the amount of fuel injection of the auxiliary fuel injection valve, the engine startability due to the decrease in the amount of fuel injection of the auxiliary fuel injection valve is reduced. The decrease is favorably compensated for by increasing the fuel injection amount of the main fuel injection valve. Therefore, according to the above configuration, it is possible to appropriately suppress the occurrence of backfire and the deterioration of the engine startability.

According to the present invention, a direct injection spark having a main fuel injection valve for injecting fuel into the engine combustion chamber and an auxiliary fuel injection valve for injecting fuel into the intake passage when the engine is started. In a fuel injection control device for an ignition internal combustion engine,
An auxiliary fuel injection reducing means is provided for reducing the fuel injection amount of the auxiliary fuel injection valve as the opening of the throttle valve for adjusting the amount of intake air introduced into the engine combustion chamber increases.

According to the above configuration, as the amount of intake air introduced into the engine combustion chamber increases, the degree of leaning of the combustion air-fuel ratio increases, and the combustion speed of the air-fuel mixture in the engine combustion chamber decreases. That is, the more the flame in the engine combustion chamber ignites the mixture in the intake passage, the lower the fuel concentration of the mixture becomes. Therefore, generation of backfire can be suitably suppressed.

According to a ninth aspect of the present invention, in the fuel injection control device for a direct injection type spark ignition internal combustion engine according to the eighth aspect, the fuel injection amount of the auxiliary fuel injection valve is reduced by the auxiliary fuel injection reducing means. Main fuel injection increasing means is further provided for increasing the fuel injection amount of the main fuel injection valve as the degree of reduction at the time of reduction increases.

According to the above construction, in addition to the operation and effect of the invention described in claim 8, the deterioration of the engine startability due to the decrease in the fuel injection amount of the auxiliary fuel injection valve is reduced by the reduction of the fuel injection amount of the main fuel injection valve. An increase in the amount enables a suitable suppression.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment in which the present invention is applied to a fuel injection control device for a direct injection gasoline engine will be described below.

FIG. 1 shows a schematic configuration of a fuel injection control device according to this embodiment. The fuel injection control device includes a fuel supply system 2 for injecting fuel into the engine 10.
0, a control system 30 for controlling fuel injection and the like by the fuel supply system 20, and a detection system 40 comprising various sensors and outputting a detection signal from these sensors to the control system 30 as a part of control data. You.

The fuel supply system 20 of the fuel injection control device is provided for each of the cylinders # 1 to # 4 of the engine 10, and directly injects fuel into the combustion chambers 14 of the cylinders # 1 to # 4. Fuel injection valve 21, delivery pipe 22 for distributing and supplying fuel to main fuel injection valve 21, delivery pipe 2
2. A supply pump 24 and a feed pump 25 for supplying the fuel in the fuel tank 23 to the fuel tank 2, and the fuel is directly supplied from the feed pump 25 to inject the fuel into the surge tank 12 forming a part of the intake passage 11. The fuel injection valve 26 is provided.

Main fuel injection valve 21 and auxiliary fuel injection valve 26
Are provided with an electromagnetic solenoid (not shown) inside thereof, and these valves 21 and 26 are controlled based on a drive signal from the control system 30 input to the electromagnetic solenoid.
Is set.

During normal operation, the supply pump 24 pressurizes fuel fed from the feed pump 25 to a high pressure and feeds the fuel to the delivery pipe 22. Therefore, high-pressure fuel is injected from the main fuel injection valve 21 into the combustion chamber 14. On the other hand, when the engine is started, pressurization of the fuel by the supply pump 24 is stopped, and the feed pump 2
5 is supplied to the delivery pipe 22 through a pressurized chamber (not shown) of the supply pump 24. Therefore, fuel injection by both the main fuel injection valve 21 and the auxiliary fuel injection valve 26 is performed based on the fuel pumping by the feed pump 25.

The engine 10 includes cylinders # 1 to # 4.
The ignition plug 15 is provided in correspondence with. The ignition plugs 15 are connected to igniters 16 each having a built-in ignition coil (not shown).
It is set based on the ignition signal output from 0 to the igniter 16.

On the upstream side of the surge tank 12 in the intake passage 11, a throttle valve 17 for adjusting the amount of intake air introduced into the combustion chamber 14 through the intake passage 11 is provided. The opening of the throttle valve 17 is controlled by the throttle motor 1 controlled by the control system 30.
Adjusted by 8.

The control system 30 of the fuel injection control device includes an electronic control device 32, a main fuel injection valve 21 and an auxiliary fuel injection valve 26 that are driven and controlled through the electronic control device 32.
, An igniter 16 and a throttle motor 18.

The electronic control unit 32 includes an arithmetic unit 33 for executing arithmetic processing, a storage unit 34 for storing various control programs and data to be referred to when executing the control programs, and the fuel injection valves 21 and 26 (electromagnetic solenoids). And an input unit 36 to which detection signals of various sensors are input.

The output unit 35 displays the engine 1 until the engine 10 can operate independently when the engine is started.
Starter 1 that drives 0 crankshaft (not shown)
9 is connected. The start operation (cranking) by the starter 19 is started when an ignition switch (not shown) is switched to a start position.

The detection system 40 of the fuel injection control device includes an accelerator sensor 41, a water temperature sensor 42, an intake pressure sensor 43, a throttle sensor 44, a rotation speed sensor 45, and a cylinder discrimination sensor 46.

The accelerator sensor 41 is provided for the accelerator pedal 1
3 and the amount of depression (accelerator opening ACC
The water temperature sensor 42 is provided on a water jacket (not shown) of the engine 10 and detects the temperature of the engine cooling water (cooling water temperature THW). Further, the intake pressure sensor 43 is connected to the surge tank 12.
The throttle sensor 44 is a sensor that detects the pressure of the intake air (intake pressure PM) in the tank 12 and the throttle sensor 44 detects the opening of the throttle valve 17 (the throttle opening TA). These sensors 41 to
All of the detection signals 44 are input to the calculation unit 33 after being appropriately A / D (analog / digital) converted in the input unit 36.

The rotation speed sensor 45 is a sensor which is provided near a crankshaft (not shown) and outputs a detection signal according to the rotation thereof.
Is a sensor that is provided near a camshaft (not shown) and outputs a detection signal according to the rotation thereof. Both of the detection signals of these sensors 45 and 46 are waveform-shaped at the input unit 36, and are taken into the calculation unit 33 as pulse signals synchronized with the rotation of the crankshaft or the camshaft, respectively. The calculation unit 33 calculates the rotation speed of the crankshaft (engine rotation speed NE) and the rotation phase angle (crank angle CA) based on these pulse signals.

In the fuel injection control device according to the present embodiment, the degree of leaning of the combustion air-fuel ratio is large when the engine is started, so that the flame in the combustion chamber 14 is mixed with the air-fuel mixture in the intake passage 11. When it is determined that there is a risk of ignition, the generation of backfire is suppressed by prohibiting fuel injection by the auxiliary fuel injection valve 26.

Hereinafter, details of the fuel injection control according to the present embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is a flowchart illustrating a processing procedure when calculating the fuel injection amount at the time of starting the engine. A series of processes shown in this flowchart is performed at every predetermined crank angle (for example, 3 crank angles).
The interrupt processing for each 0 ° CA (Crank Angle) is executed by the control system 30, more specifically, by the arithmetic unit 33 of the electronic control unit 32.

First, in this process, it is determined whether or not the engine has been started (step 110). This determination is made based on the engine rotational speed NE and a predetermined rotational speed (for example, 400 rpm).
pm). Then, if it is determined that the engine speed NE is equal to or higher than the predetermined speed and it is not at the time of starting the engine (step 110: NO), the process is temporarily terminated. In this case, the fuel injection amount of the main fuel injection valve 21 is determined based on the accelerator opening ACCP and the like through another processing routine.

On the other hand, if it is determined that the engine has been started (step 110: YES), the in-cylinder fuel injection amount QINJST and the auxiliary fuel injection amount QINJADD at the time of engine start are calculated based on the coolant temperature THW (step 110). Step 12
0,130). Here, the in-cylinder fuel injection amount QINJS
T is a required amount of fuel directly injected into the combustion chamber 14 from the main fuel injection valve 21 at the time of engine start. The auxiliary fuel injection amount QINJADD is injected from the auxiliary fuel injection valve 26 into the surge tank 12. This is the required amount of fuel when starting the engine.

Each of these required quantities QINJST, QINJA
The relationship between the DD and the cooling water temperature THW is stored in the storage unit 34 of the electronic control unit 32, for example, as a function map as shown in FIG. As shown in FIG.
INJADD decreases as the cooling water temperature THW increases, and when the cooling water temperature THW exceeds a predetermined temperature,
It is set to “0”. Therefore, the fuel injection of the auxiliary fuel injection valve 26 is executed only when the engine is started when the coolant temperature THW is lower than the predetermined temperature.

Next, when the throttle opening TA is a predetermined opening a °
It is determined whether or not this is the case (step 140). In this determination process, it is determined whether the amount of intake air introduced into the combustion chamber 14 is larger than a predetermined amount, in other words, the lean air-fuel ratio of the combustion air, by comparing the throttle opening TA with the predetermined opening a °. It is determined whether the degree of chemical conversion is greater than the degree of occurrence of backfire.

Here, the throttle opening TA is equal to the predetermined opening a.
° or less, and therefore, if it is determined that the intake air amount is less than or equal to the predetermined amount (step 140: NO), this process is temporarily terminated. In this case, it is determined that there is no risk of occurrence of backfire, and the already set in-cylinder fuel injection amount QINJST and auxiliary fuel injection amount QINJADD are set.
The main fuel injection valve 21 and the auxiliary fuel injection valve 26 are respectively driven and controlled on the basis of. Therefore, from the fuel injection valves 21 and 26, the required amounts QINJST and QIN
An amount of fuel equal to JADD is injected into the combustion chamber 14 and the surge tank 12, respectively.

On the other hand, when the throttle opening TA is a predetermined opening a °
If it is determined that the intake air amount is larger than the predetermined amount (step 140: YES), the degree of leaning of the combustion air-fuel ratio is large, and backfire may occur. QINJAD
D is reset (steps 150 and 160). That is,
The auxiliary fuel injection amount QINJADD is added to the current in-cylinder fuel injection amount QINJST, and the added value (= QINJADD)
JST + QINJADD) is the new in-cylinder fuel injection amount QI
It is set as NJST (step 150). Then, the auxiliary fuel injection amount QINJADD is set to "0" (step 160), and this processing is temporarily ended. Therefore, in this case, the fuel injection by the auxiliary fuel injection valve 26 is prohibited, and the main fuel injection valve 21 outputs the auxiliary fuel injection amount more than the original required fuel injection amount (in-cylinder fuel injection amount QINJST). A larger amount of fuel is injected by an amount corresponding to QINJADD.

As described above, in this embodiment, the degree of leanness of the combustion air-fuel ratio is monitored by determining the amount of intake air introduced into the combustion chamber 14 based on the magnitude of the throttle opening TA. Like that. If it is determined from the degree of leanness of the combustion air-fuel ratio that backfire may occur, the auxiliary fuel injection valve 2
6 is prohibited.

(1) Accordingly, no air-fuel mixture is generated in the intake passage 11 such as the surge tank 12, and only the intake air flows through the passage 11. As a result, even if the combustion of the air-fuel mixture becomes slow and the flame in the combustion chamber 14 remains even during the intake stroke, the flame is supplied to the intake passage 1.
There is no ignition of the air-fuel mixture in 1, and the occurrence of backfire can be reliably suppressed.

When the fuel injection of the auxiliary fuel injection valve 26 is prohibited as described above, the engine startability may be deteriorated. However, in the present embodiment, the fuel injection of the auxiliary fuel injection valve 26 is restricted. On the other hand, the fuel injection amount of the main fuel injection valve 21 (in-cylinder fuel injection amount QINJST) is increased.

(2) Therefore, it is possible to minimize the deterioration of the engine startability due to the prohibition of the fuel injection of the auxiliary fuel injection valve. Further, in the present embodiment, the intake air amount is estimated based on the throttle opening TA, but the intake air amount is estimated based on, for example, the intake pressure PM and the engine speed NE, or When an air flow meter is provided, the estimation can be made based on the intake air flow rate detected by the air flow meter.

However, normally, when the engine is started, fluctuations in the intake pressure PM, the engine speed NE, and the intake air flow rate become large. Therefore, when the intake air amount is estimated based on these parameters, for example, Even when the fuel injection of the auxiliary fuel injection valve should be prohibited, there is a concern that the fuel injection may be permitted due to a temporary decrease in the intake air amount.

(3) In this regard, according to the present embodiment, the intake air amount is estimated as an average value from which the variation is removed, and the fuel of the auxiliary fuel injection valve is estimated based on the estimated value. Since it is determined whether or not to prohibit the injection, the occurrence of backfire can be more reliably suppressed.

[Second Embodiment] Next, a second embodiment of the present invention will be described, focusing on differences from the first embodiment.

In the present embodiment, the total amount of fuel injection required for starting the engine (total fuel injection QTOTAL) is determined by the in-cylinder fuel injection according to the division ratio k set based on the accelerator opening ACCP and the like. By dividing the quantity QINJST and the auxiliary fuel injection quantity QINJADD, these respective injection quantities QINJST and QINJADD are set to values suitable for suppressing the occurrence of backfire and the deterioration of the engine startability, respectively.

Hereinafter, details of the fuel injection control according to the present embodiment will be described with reference to FIGS. 4 and 5. FIG. FIG. 4 is a flowchart showing a processing procedure when calculating the fuel injection amount at the time of starting the engine. A series of processes shown in this flowchart is performed at every predetermined crank angle (for example, 3 crank angles).
This is executed by the control system 30, more specifically, by the arithmetic unit 33 of the electronic control unit 32, as an interrupt process at each 0 ° CA).

First, in this process, it is determined whether or not the engine is being started based on the engine speed NE (step 210). If it is determined that the engine is not being started (step 210: NO), the process is temporarily terminated, and the fuel injection amount of the main fuel injection valve 21 is determined through another processing routine.

On the other hand, if it is determined that the engine is being started (step 210: YES), the total fuel injection amount QTOTAL is calculated based on the cooling water temperature THW (step 2).
20). Next, the cooling water temperature THW and the accelerator opening ACC
A division ratio k (0 ≦ k <1.0) is calculated based on P (step 230).

The division ratio k is determined by the total fuel injection amount QTOTA
The ratio of the auxiliary fuel injection amount QINJADD to L is determined. When the total fuel injection amount QTOTAL is constant, the auxiliary fuel injection amount QINJADD increases as the division ratio k increases, and when the division ratio k is set to “0”, the auxiliary fuel injection amount QINJADD increases. The fuel injection of the injection valve 26 is stopped.

The relationship between the division ratio k and the coolant temperature THW and the accelerator opening ACCP is stored in the storage unit 34 of the electronic control unit 32 as a function map as shown in FIG. 5, for example. As shown in FIG.
When the accelerator opening ACCP is constant, the value is set to a larger value as the cooling water temperature THW becomes lower. Therefore, the lower the cooling water temperature THW, the lower the auxiliary fuel injection valve 26
The ratio of fuel injected from the fuel cell increases.

Further, when the cooling water temperature THW is constant, the division ratio k is set to a smaller value as the accelerator opening ACCP increases. Therefore, the accelerator opening ACC
As P increases, the proportion of fuel injected from auxiliary fuel injection valve 26 decreases.

Here, the accelerator opening ACCP is used for determining the division ratio k as having a correlation with the throttle opening TA and the intake air amount which changes according to the throttle opening TA. That is, this accelerator opening ACCP
Becomes larger, the throttle opening TA becomes larger, so that it can be determined that the intake air amount is larger. Therefore, by determining the split ratio k based on the accelerator opening ACCP as described above, the proportion of fuel injected from the auxiliary fuel injection valve 26 increases as the intake air amount increases and the combustion air-fuel ratio becomes leaner. As the degree increases, it decreases.

When the division ratio k is determined in this manner, the auxiliary fuel injection amount QINJA is calculated according to the following arithmetic expressions (1) and (2).
DD and the in-cylinder fuel injection amount QINJST are calculated (steps 240 and 250), respectively, and the process is temporarily terminated.

QINJADD = QTOTAL × k (Equation 1) QINJST = QTOTAL−QINJADD (Equation 2) As is clear from the above arithmetic expressions (1) and (2) and the function map shown in FIG. , Accelerator opening ACCP "0 °"
When the value of the auxiliary fuel injection amount QINJADD and the value of the in-cylinder fuel injection amount QINJST are set to the respective reference values QINJ
If ADDK and QINJSTK are used, the auxiliary fuel injection amount Q
INJADD is reduced from its reference value QINJADDK according to the accelerator opening ACCP, and the degree of reduction △ Q
INJADD is set to be larger as the accelerator opening ACCP becomes larger.

On the other hand, the in-cylinder fuel injection amount QINJST has a reference value QINJSTK corresponding to the accelerator opening ACCP.
The amount of increase △ QINJST is set to increase as the accelerator opening ACCP increases, in other words, the amount of decrease △ QINJADD of the auxiliary fuel injection amount QINJADD increases.

Accordingly, as the intake air amount increases, the degree of leaning of the combustion air-fuel ratio increases, and the combustion speed of the air-fuel mixture in the combustion chamber 14 decreases, the air-fuel mixture generated in the intake passage 11 decreases. The fuel concentration can be suppressed, and the decrease in engine startability due to the decrease in the auxiliary fuel injection amount QINJADD can be suitably compensated for by increasing the in-cylinder fuel injection amount QINJST.

Therefore, according to the present embodiment, in addition to the effects (1) and (2) described in the first embodiment, (4) the occurrence of backfire and the deterioration of engine startability are further reduced. Can be appropriately suppressed.

Also, since the intake air amount at the time of starting the engine is estimated based on the accelerator opening ACCP,
The intake air amount is estimated as an average value obtained by removing the fluctuation. Therefore, according to the present embodiment, the same operation and effect as (3) described in the first embodiment can be achieved.

[Third Embodiment] Next, a third embodiment of the present invention will be described, focusing on differences from the first embodiment.

In this embodiment, when backfire is likely to occur, the starting operation by the starter 19 is prohibited, and the fuel injection of both the main fuel injection valve 21 and the auxiliary fuel injection valve 26 is substantially prohibited. By doing so, the occurrence of backfire is suppressed.

Hereinafter, the details of the engine start control in this embodiment will be described. FIG. 6 is a flowchart showing a processing procedure when operating the starter 19 at the time of starting the engine. A series of processes shown in this flowchart is executed by the control system 30, specifically, the arithmetic unit 33 of the electronic control unit 32, as an interrupt process at predetermined time intervals.

In this process, first, it is determined whether or not the ignition switch has been switched to the starting position (step 310). If the ignition switch is in the starting position (step 310: YE
S), the engine speed NE is compared with a predetermined speed TNE (step 320), and when the engine speed NE is equal to or lower than the predetermined speed TNE (step 320: YE).
S) Assuming that the engine start has not been completed, the cooling water temperature THW is further compared with a predetermined determination temperature TTHW (step 330). This predetermined determination temperature TTHW is determined by whether or not the required fuel injection amount of the auxiliary fuel injection valve 26 (corresponding to the auxiliary fuel injection amount QINJADD) is equal to or greater than “0”, in other words, the fuel of the auxiliary fuel injection valve 26. This is a determination value for determining whether injection is performed.

Then, the cooling water temperature THW becomes equal to the predetermined judgment temperature T.
If not more than THW (step 330: YE
S), it is determined that the fuel injection by the auxiliary fuel injection valve 26 is to be executed, and then the accelerator opening ACCP is set to “0”.
°, in other words, whether or not the throttle opening TA is set to be equal to or greater than the idle opening and a predetermined amount or more of intake air is introduced into the combustion chamber 14 is determined. (Step 340).

Then, the accelerator opening ACCP is "0 °".
If not (step 340: NO), the start permission flag XSTRT is set to “OFF” (step 355). Similarly, when the ignition switch is not at the start position (step 310: NO), or when the engine speed NE is higher than the predetermined speed TNE (step 320: NO), the start permission flag XSTRT is similarly set.
Is set to "OFF" (step 355).

On the other hand, when the cooling water temperature THW is equal to the predetermined judgment temperature TT
If it is higher than HW (Step 330: NO), or if the accelerator opening ACCP is “0 °” (Step 3)
40: YES), the start permission flag XSTR
T is set to "ON" (step 350).

Next, the start permission flag XSTRT is set to "O".
N is determined (step 360), and if the flag XSTRT is "ON" (step 36).
0: YES), the start operation by the starter 19 is started (step 370), and the flag XSTRT is set to “OF”.
F "(step 360: NO), the start operation by the starter 19 is stopped (prohibited) (step 3).
80), the process is temporarily terminated.

As described above, according to the present embodiment, the throttle valve 17 is opened beyond the idle opening degree by depressing the accelerator pedal 13, and the auxiliary fuel injection valve 26 is opened.
When it is determined that the backfire is likely to occur when the fuel injection is performed, the starting operation by the starter 19 is prohibited. Therefore, the fuel injection of both the main fuel injection valve 21 and the auxiliary fuel injection valve 26 is also substantially prohibited, so that the occurrence of backfire can be reliably prevented.

Here, unlike the present embodiment, even if only the fuel injection of the auxiliary fuel injection valve 26 is prohibited, the occurrence of backfire can be surely suppressed. However, when the fuel injection of the auxiliary fuel injection valve 26 is prohibited and the engine is started only by the fuel injection of the main fuel injection valve 21, the engine startability is reduced. As a result, the fuel injected from the main fuel injection valve 21 may adhere to the wall surface of the combustion chamber 14 without burning without completing the start. For this reason, when restarting the engine, the combustion air-fuel ratio in the combustion chamber 14 becomes excessively rich due to the vaporization of the fuel adhering to the wall surface of the engine combustion chamber at the time of the previous start, and the engine startability at the time of such restart is restarted. May worsen.

In this regard, in the present embodiment, fuel injection is performed in a state where the engine startability is deteriorated as described above, and a large amount of fuel does not adhere to the wall surface of the combustion chamber 14.
When the depression of the accelerator pedal 13 is released, the engine 10 can be started immediately.

(5) Therefore, according to the present embodiment, it is possible to suppress the deterioration of the engine startability at the time of restarting as described above. [Other Embodiments] Each of the embodiments described above can be implemented by changing the configuration as described below.

In the first embodiment, the throttle opening T
When A is equal to or greater than the predetermined opening degree a °, the auxiliary fuel injection valve 2
6, the fuel injection amount of the auxiliary fuel injection valve 26 (auxiliary fuel injection amount QINJADD) is prohibited.
May be reduced. Further, at the time of the decrease, the degree of decrease of the auxiliary fuel injection amount QINJADD may be set to be larger as the throttle opening TA becomes larger. Further, the fuel injection amount of the main fuel injection valve 21 may be increased in accordance with the degree of the decrease.

In the first embodiment, the throttle opening T
Although the degree of leaning of the combustion air-fuel ratio is monitored by comparing A with the predetermined opening degree a °, for example, the intake air amount calculated from the intake pressure PM and the engine speed NE, the accelerator opening degree ACCP, The degree of lean operation may be monitored based on a parameter that varies in correlation with the amount of intake air introduced into the combustion chamber 14 such as the intake pressure PM.
Further, when the air flow meter is provided, the degree of lean operation can be monitored based on the intake air flow rate detected by the air flow meter.

In the second embodiment, the split ratio k is calculated not only based on the coolant temperature THW but also on the basis of the accelerator opening ACCP, but based on the throttle opening TA instead of the accelerator opening ACCP. The same division ratio k may be calculated. Further, the same division ratio k is set to the intake air amount calculated from the intake pressure PM and the engine speed NE, or the intake pressure PM.
Alternatively, it may be calculated based on a parameter that varies in correlation with the amount of intake air introduced into the combustion chamber 14.

In the above embodiments, the auxiliary fuel injection valve 2
6, the backfire was suppressed by inhibiting the fuel injection of No. 6 or reducing the fuel injection amount (auxiliary fuel injection amount QINJADD). At the same time, the ignition timing was advanced to the advanced side. By changing the timing, the occurrence may be suppressed more reliably.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of a fuel injection control device according to the present invention.

FIG. 2 is a flowchart showing a procedure for calculating a start-time fuel injection amount according to the first embodiment;

FIG. 3 is a function map showing the relationship between the in-cylinder fuel injection amount, the auxiliary fuel injection amount, and the coolant temperature.

FIG. 4 is a flowchart illustrating a procedure for calculating a start-time fuel injection amount according to the second embodiment;

FIG. 5 is a function map showing a relationship between a split ratio for determining an auxiliary fuel injection amount, a coolant temperature, and an accelerator opening.

FIG. 6 is a flowchart illustrating a procedure of an engine start process according to a third embodiment;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Intake passage, 12 ... Surge tank, 13 ... Accelerator pedal, 14 ... Combustion chamber, 15 ... Spark plug, 16 ... Igniter, 17 ... Throttle valve,
18 throttle motor, 19 starter, 20 fuel supply system, 21 main fuel injection valve, 22 delivery pipe,
23: fuel tank, 24: supply pump, 25: feed pump, 26: auxiliary fuel injection valve, 30: control system, 3
2: Electronic control unit, 33: Operation unit, 34: Storage unit, 35
... output unit, 36 ... input unit, 40 ... detection system, 41 ... accelerator sensor, 42 ... water temperature sensor, 43 ... intake pressure sensor, 4
4 ... Throttle sensor, 45 ... Rotation speed sensor, 46 ... Cylinder discrimination sensor, # 1 to # 4 ... Cylinder.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahide Nagano 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Atsushi Ishida 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F Terms (reference) 3G301 HA04 JA00 KA01 LA00 LA03 LB04 LC03 MA01 MA11 MA23 MA24 NA08 NB11 NB15 NE01 NE06 NE15 PA07Z PA11Z PE01Z PE03Z PE04Z PE05Z PE08Z PF03Z PF16Z

Claims (9)

[Claims] 1. A fuel injection control system for a direct injection spark ignition internal combustion engine having a main fuel injection valve for injecting fuel into an engine combustion chamber and an auxiliary fuel injection valve for injecting fuel into an intake passage when the engine is started. An in-cylinder injection spark ignition internal combustion system, wherein a leaning degree of a combustion air-fuel ratio in the engine combustion chamber is monitored and a fuel injection amount of the auxiliary fuel injection valve is limited based on the leaning degree. Engine fuel injection control device. 2. A fuel injection control for a direct injection spark ignition internal combustion engine having a main fuel injection valve for injecting fuel into an engine combustion chamber and an auxiliary fuel injection valve for injecting fuel into an intake passage when the engine is started. The apparatus further comprises auxiliary fuel injection inhibiting means for inhibiting fuel injection of the auxiliary fuel injection valve when an opening of a throttle valve for adjusting an amount of intake air introduced into the engine combustion chamber is larger than a predetermined opening. A fuel injection control device for a direct injection type spark ignition internal combustion engine. 3. The fuel injection control device for a direct injection type spark ignition internal combustion engine according to claim 2, wherein the main fuel is supplied when the auxiliary fuel injection prohibiting means prohibits the fuel injection of the auxiliary fuel injection valve. A fuel injection control apparatus for a direct injection type spark ignition internal combustion engine, further comprising a main fuel injection prohibiting means for prohibiting fuel injection of an injection valve. 4. A fuel injection control device for a direct injection type spark ignition internal combustion engine according to claim 2, wherein said auxiliary fuel injection prohibiting means prohibits said main fuel when said fuel injection of said auxiliary fuel injection valve is prohibited. A fuel injection control apparatus for a direct injection spark ignition internal combustion engine, further comprising a main fuel injection increasing means for increasing the fuel injection amount of an injection valve. 5. A fuel injection control system for a direct injection spark ignition internal combustion engine having a main fuel injection valve for injecting fuel into an engine combustion chamber and an auxiliary fuel injection valve for injecting fuel into an intake passage when the engine is started. The apparatus further includes auxiliary fuel injection reducing means for reducing the fuel injection amount of the auxiliary fuel injection valve when an opening of a throttle valve for adjusting an amount of intake air introduced into the engine combustion chamber is larger than a predetermined opening. A fuel injection control device for a direct injection spark ignition internal combustion engine. 6. A fuel injection control apparatus for a cylinder injection type spark ignition internal combustion engine according to claim 5, wherein said auxiliary fuel injection reducing means reduces said fuel injection amount of said auxiliary fuel injection valve when said auxiliary fuel injection amount is reduced. A fuel injection control device for a direct injection type spark ignition internal combustion engine, further comprising a main fuel injection increasing means for increasing a fuel injection amount of a fuel injection valve. 7. The fuel injection control device for a direct injection type spark ignition internal combustion engine according to claim 6, wherein the auxiliary fuel injection reducing means increases the fuel injection of the auxiliary fuel injection valve as the opening of the throttle valve increases. The main fuel injection increasing means sets the increasing degree of the fuel injection amount of the main fuel injection valve according to the decreasing degree of the fuel injection amount of the auxiliary fuel injection valve. A fuel injection control device for a direct injection spark ignition internal combustion engine. 8. A fuel injection control system for a direct injection spark ignition internal combustion engine having a main fuel injection valve for injecting fuel into an engine combustion chamber and an auxiliary fuel injection valve for injecting fuel into an intake passage when the engine is started. The apparatus according to claim 1, further comprising: an auxiliary fuel injection reducing unit configured to reduce the fuel injection amount of the auxiliary fuel injection valve as the opening of the throttle valve for adjusting the amount of intake air introduced into the engine combustion chamber increases. A fuel injection control device for a direct injection spark ignition internal combustion engine. 9. A fuel injection control apparatus for a direct injection type spark ignition internal combustion engine according to claim 8, wherein the degree of reduction in reducing the fuel injection amount of the auxiliary fuel injection valve by the auxiliary fuel injection reduction means is determined. A fuel injection control device for a direct injection spark ignition internal combustion engine, further comprising a main fuel injection increasing means for increasing the fuel injection amount of the main fuel injection valve as the size of the fuel injection valve increases.