JP2000257476A - Control device for in-cylinder injection internal combustion engine - Google Patents

Abstract

(57) Abstract: A control device for a direct injection internal combustion engine, which promotes mixing of a premixed air-fuel mixture of main injection and additional fuel to prevent deterioration of exhaust gas performance. SOLUTION: In a control device of a direct injection internal combustion engine 1 for injecting fuel directly into a combustion chamber 3 at least during an intake stroke, an injection amount calculating means 34 calculates an injection amount of fuel based on an operating state of the engine. The first fuel injection control means 35 controls the fuel injection means 9 to inject the calculated amount of fuel directly into the combustion chamber 3 during the intake stroke, and the correction amount calculation means 36 controls the intake air by the end of the intake stroke. A fuel correction amount is calculated based on the intake air amount detected by the amount detection means, and the fuel injection is performed by the second fuel injection control means 37 so that the calculated amount of correction fuel is injected into the combustion chamber from the end of the intake stroke. Control means 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for a direct injection type internal combustion engine which is suitable for use in a direct injection type internal combustion engine having an intake stroke injection mode in which fuel is injected at least during an intake stroke.

[0002]

2. Description of the Related Art In recent years, a direct injection internal combustion engine capable of directly injecting fuel into a combustion chamber has been put to practical use. This type of internal combustion engine is capable of supplying fuel in a wide range from the early stage of the intake stroke to the late stage of the compression stroke due to the feature that fuel is directly injected into the combustion chamber. Incidentally, the fuel injection amount in the internal combustion engine is calculated based on the amount of air taken into the combustion chamber and measured. For example, in the case of a direct injection internal combustion engine, in an intake stroke injection mode in which fuel is injected during an intake stroke, a fuel injection amount is set based on an air amount measured during an exhaust stroke. However, if the air amount increases during the intake stroke after measuring the intake air amount during acceleration or the like, the air-fuel ratio becomes leaner than the setting.

[0003] In this regard, Japanese Patent Publication No. Hei 7-59910 discloses that the amount of air sucked into the cylinder near the end of the intake stroke is detected, and the shortage of the fuel injection amount is calculated from the detected amount of air. Based on the results, there has been proposed a technique for injecting a shortage of fuel directly into a cylinder during a compression stroke. Further, as a method of detecting the intake air amount, a method of calculating from an in-cylinder pressure detected by an in-cylinder pressure sensor and an intake air temperature detected by an intake air temperature sensor, an intake air detected by a negative pressure sensor immediately before the intake valve closes, or the like. A method of calculating from a pipe negative pressure and an intake air temperature by an intake air temperature sensor is disclosed.

[0004]

However, the above technique has the following problems. That is, when the amount of intake air is detected near the end of the intake stroke and the insufficient fuel is injected during the compression stroke as in the above-described technique, the detection accuracy of the intake air amount is increased to accurately detect the insufficient fuel amount. On the other hand, there is a possibility that the mixture of the premixed air of the main injection injected in the intake stroke and the additional fuel may not be sufficiently promoted. In particular, as the injection of the additional fuel approaches the end of the compression stroke, the mixing of the fuel becomes insufficient. For this reason, there is a high possibility that smoke is generated or knock is generated to deteriorate the exhaust gas performance.

The present invention has been made in view of the above-mentioned problems, and an in-cylinder injection type in which exhaust gas performance is prevented from deteriorating by promoting mixing of a pre-mixed air mixture of main injection and additional fuel. It is an object to provide a control device for an internal combustion engine.

[0006]

In order to achieve the above object, a control apparatus for a direct injection internal combustion engine according to the present invention provides a direct injection internal combustion engine which injects fuel directly into a combustion chamber at least during an intake stroke. In the control device, the fuel injection amount is calculated by the injection amount calculating means based on the operating state of the engine, and the fuel injection amount is calculated by the first fuel injection control means so that the calculated amount of fuel is directly injected into the combustion chamber during the intake stroke. Control means, and a correction amount of the fuel is calculated by the correction amount calculating means based on the intake air amount detected by the intake air amount detecting means by the end of the intake stroke, and the calculated amount of correction fuel is supplied to the intake stroke. The fuel injection means is controlled by the second fuel injection control means so that the fuel is injected into the combustion chamber from the last stage.

[0007] Thus, the shortage of fuel due to the increase in the amount of intake air in the intake stroke is eliminated, and the mixture of the premixed air of fuel injected into the combustion chamber during the intake stroke and the increased amount of fuel is sufficient. And the deterioration of exhaust gas performance is prevented.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a control device for a direct injection internal combustion engine as an embodiment of the present invention. First, an outline of an in-cylinder injection type internal combustion engine to which the present control device is applied will be described. That is, the engine is a four-cycle engine that is of a spark ignition type and can directly inject fuel into the combustion chamber. As a mode of fuel injection, stoichiometric operation (stoichiometric air-fuel ratio operation) by premixed combustion is realized, and stoichiometric mode in which fuel is injected during the intake stroke to improve output, and lean operation by premixed combustion are realized. During the intake stroke (especially in the first half of the intake stroke), a lean injection mode in which fuel is injected during the intake stroke (particularly in the first half of the intake stroke), and a lean operation by stratified combustion are realized, and during the compression stroke ( In particular, a late lean injection mode in which fuel is injected in the latter half of the compression stroke) is provided, and is selected according to the operating state.

[0011] The schematic structure of the in-cylinder injection type internal combustion engine will be described. As shown in FIG.
The intake passage 4 and the exhaust passage 5 are connected so that they can communicate with the combustion chamber 3. The communication between the intake passage 4 and the combustion chamber 3 is controlled by an intake valve 6, and the communication between the exhaust passage 5 and the combustion chamber 3 is controlled by an exhaust valve 7. The cylinder head 2 is provided with an ignition plug 8 at the center of the top of the combustion chamber 3, and an injector (fuel injection means) 9 has its opening facing the combustion chamber 3 on the intake passage 3 side. Are located in The fuel pressurized by a high-pressure pump (not shown) is supplied to the injector 9.

In the intake passage 4, an intake manifold 11 for introducing intake air into the combustion chamber 3 of each cylinder is provided at an intake port 10 provided relatively upright with respect to the combustion chamber 3.
It is connected to the. Upstream of the intake manifold 11,
An air cleaner 13 and a throttle valve 12 are provided, and the throttle valve 12 is provided with a throttle position sensor (TPS) 14 for detecting the opening thereof. An air flow sensor (AFS) 15 for detecting the intake air flow rate A is provided between the air cleaner 13 and the throttle valve 12.

On the other hand, the exhaust passage 5 is provided with the combustion chamber 3 of each cylinder.
An exhaust manifold 17 for collecting exhaust gases discharged from the exhaust gas into one is connected to the exhaust port 16. An exhaust purification device 18 and a muffler (muffler) (not shown) are provided downstream of the exhaust manifold 17. The exhaust gas purifying device 18 is provided with a NOx catalyst and a three-way catalyst, and purifies harmful components (CO, HC, NOx) in the exhaust gas.

Further, the crankshaft 19 is provided with a crank angle sensor 20. The crank angle sensor 20 detects the rotation of the crankshaft 19 by 180 °.
Signal is output as one cycle, and 5 °
BTDC (365 ° BTDC) and 185 ° BTDC (5
45 ° BTDC), the signal changes from on to off.

The control device (ECU) 30 is applied to the engine 1 having the above-described configuration, and includes, as functional elements, an operation mode selection unit 31, a fuel injection control unit 32, and an ignition timing control unit 33. I have. Operation mode selection means 31
Is means for selecting one of the above-described operation modes according to the engine rotation speed Ne and the average effective pressure Pe (engine load). As the engine rotation speed Ne, information detected by the crank angle sensor 20 is used, and the average effective pressure Pe is used.
Is calculated from each information of the engine rotation speed Ne and the throttle opening θ detected by the TPS 14.

The fuel injection control means 32 includes the injector 9
This is a means for controlling the injection timing and injection amount of the fuel from the engine, and includes an injection amount calculation means 34, a first fuel injection control means 35, a correction amount calculation means 36, and a second fuel injection control means 37. Explaining each constituent means, the injection amount calculating means 34 is a means for calculating the amount of fuel to be injected into the combustion chamber 3. First, the fuel injection control according to the operation mode set by the operation mode selecting means 31. Select a map,
Using the selected fuel injection control map, a target air-fuel ratio corresponding to the engine rotation speed Ne and the average effective pressure Pe is set. And at the end of the previous process, AFS
15 and the engine rotation speed Ne
A / Ne (∝intake air amount) is calculated from
/ Ne and target air-fuel ratio, the fuel injection amount (injection pulse width)
Is calculated.

For example, when the operation mode is the stoichiometric mode in which fuel is injected during the intake stroke or the lean injection mode in the first half, the fuel injection amount is determined based on the intake air flow rate detected at the end of the exhaust stroke and the engine speed. In the case of the late lean injection mode in which the fuel injection is performed during the compression stroke during the compression stroke, the calculation is performed based on the intake air flow rate detected at the end of the intake stroke and the engine rotation speed.

The first fuel injection control means 35 is means for controlling the injector 9 according to the fuel injection amount calculated by the injection amount calculation means 34 and the injection timing determined according to the operation mode. From the fuel injection control map selected according to the operation mode, the fuel injection end timing is set according to the engine rotation speed Ne and the average effective pressure Pe, and the set fuel injection end timing and fuel injection amount (injection pulse width) are set. , The fuel injection start timing is calculated, and an injection pulse is output to the injector 9.

Next, the correction amount calculating means 36 and the second fuel injection control means 37 will be described.
It functions when the selected operation mode is the stoichiometric mode or the lean injection mode.
That is, it is a means that functions only when fuel injection is performed during the intake stroke. When performing fuel injection in the intake stroke, the fuel injection amount (injection pulse width) as described above is calculated based on the intake air flow A ₁ measured in the exhaust stroke end (365 ° BTDC). That is, the amount of intake air estimated from the intake air flow rate A ₁ measured at the end of the exhaust stroke and the engine speed (average engine speed during the exhaust stroke) Ne ₁ is:
The fuel injection amount is calculated as being equal to the intake air actually sucked during the intake stroke. However, when the driver depresses the accelerator for acceleration or the like and the throttle valve 12 is opened, the boost gradually increases,
The intake air amount will also increase. If this increase in the intake air amount occurs in the intake stroke, the amount of air actually sucked into the combustion chamber 3 will be larger than that estimated from A ₁ / Ne ₁ during the exhaust stroke, and A ₁ / in the calculated fuel injection amount on the basis of Ne _1, it becomes leaner than the target air-fuel ratio.

Therefore, when the intake air amount increases during the intake stroke, the correction amount calculating means 36 calculates the correction amount (correction increase) of the fuel injection amount according to the increase. First, the correction amount calculating means 36 detects the intake air flow rate A ₂ by the AFS 15 at the end of the intake stroke (185 ° BTDC), and detects the detected intake air flow rate A ₂ and the engine speed (average engine speed in the intake stroke).
Calculating the A ₂ / Ne ₂ from Ne ₂ Prefecture, the exhaust stroke A ₁ /
Ne ₁ is compared with Ne ₁ . When the difference ΔA / Ne (A ₂ / Ne ₂ −A ₁ / Ne ₁ ) is equal to or greater than a predetermined value, it is determined that the intake air amount has increased, and Δ
The correction amount of the fuel injection amount according to ΔA / Ne is calculated by regarding A / Ne as an increase in the intake air amount. The correction amount (injection pulse width) is calculated from ΔA / Ne and the target air-fuel ratio.

The second fuel injection control means 37 is means for controlling the injector 9 so as to inject the correction fuel of the amount (injection pulse width) calculated by the correction amount calculation means 36 into the combustion chamber 3, Immediately after the correction amount is calculated, the injector 9 is controlled to inject the correction fuel. Therefore, the correction fuel is injected from the end of the intake stroke, and the injection ends at the beginning of the compression stroke.

In the late lean injection mode, that is,
When the fuel injection is performed in the compression stroke, the above-described problem does not occur, so that the correction amount calculating unit 36 and the second fuel injection control unit 37 do not function, and the injection amount calculating unit 34 and the first Only the fuel injection control means 35 functions. Therefore, in this case, the fuel calculated based on the intake air flow rate detected during the intake stroke is injected at a predetermined timing of the compression stroke (the latter half of the compression stroke), and no subsequent correction is performed.

Finally, the ignition timing control means 38 is means for controlling the ignition timing of the spark plug 8 in accordance with the fuel injection control of the first fuel injection control means 36. The ignition timing control map corresponding to the mode is selected, and the selected ignition timing control map is used to correspond to the fuel injection control of the first fuel injection control means 26 according to the engine speed Ne and the average effective pressure Pe. The ignition timing is set.

The control apparatus for a direct injection internal combustion engine as one embodiment of the present invention is configured as described above.
In the intake stroke injection, control is performed as shown in the following flowcharts shown in FIGS. First,
As shown in FIG. 2, when the crank angle sensor 20 detects 365 ° BTDC during the exhaust stroke (when the output signal of the crank angle sensor 20 is turned off from on), the control unit 30 performs a cycle of 180 °. That is, 545
° calculates the engine rotational speed Ne ₁ from the time it took to 365 ° BTDC from BTDC (step S100), detects the intake air flow A ₁ by AFS15 (step S110).

Then, the injection amount calculating means 34
Rotation speed Ne₁And intake air flow rate A ₁And from A₁/ Ne
₁Is calculated (step S120), and the calculated A₁/ Ne
₁And fuel injection based on target air-fuel ratio (injector gain)
Amount (injection pulse width) Pw₁(Step S13)
0). The first fuel injection control means 35 responds to the operation mode.
Engine speed from the fuel injection control map selected
Fuel injection end timing according to degree Ne and average effective pressure Pe
And set the fuel injection end timing and fuel injection amount (injection
Firing pulse width) Pw₁From the fuel injection start timing
You. Then, from the calculated fuel injection start time to end time,
, Fuel is directly injected into the combustion chamber 3 from the injector 9.
Fire.

Next, as shown in FIG.
Means that the crank angle sensor 20 is 18 during the intake stroke.
When 5 ° BTDC is detected, 1
The engine rotation speed Ne ₂ is calculated from the 180 ° cycle up to 85 ° BTDC (step S200).
FS15 by detecting the intake air flow A ₂ (step S210).

Then, the correction amount calculating means 36
Rotation speed Ne_TwoAnd intake air flow rate A _TwoAnd from A_Two/ Ne
_TwoIs calculated (step S220), and the calculated A_Two/ Ne
_TwoAnd A calculated in step S120₁/ Ne₁And the difference Δ
A / Ne (A_Two/ Ne_Two-A ₁/ Ne₁)
(Step S230). The calculated difference ΔA / Ne is a predetermined value
(Step S240), the difference ΔA / Ne is
If the difference is equal to or larger than the predetermined value, the correction amount calculating means 36 calculates the difference ΔA
/ Ne and target air-fuel ratio (injector gain)
Fuel amount (injection pulse width) Pw_TwoIs calculated (step S
250). Then, the second fuel injection control means 37
Immediately after the positive fuel amount Pw2 is calculated, the injector 9
To inject the correction fuel directly into the combustion chamber 3 (step
Step S260). Thereby, the correction fuel Pw_TwoIs the intake line
Injection at the end of the compression stroke, and at the beginning of the compression stroke at the latest.
Is injected into the combustion chamber 3 during the intake stroke.
Fuel Pw₁Is sufficiently promoted with the premixed gas.

FIG. 4 shows the above control in a time chart. With reference to FIG. 4, the operation and effect of the present control device when the intake air amount increases during the intake stroke will be described more specifically. As shown in FIG. 4, it is assumed that the driver operates the accelerator during the exhaust stroke (particularly in the latter half of the exhaust stroke) to increase the opening of the throttle valve 12. At this time, the boost also rises to a magnitude corresponding to the throttle opening, but does not rise completely in response to the change in the throttle opening, but gradually rises slightly after the change in the throttle opening.

In this control means, first, at the end of the exhaust stroke (3
The 65 ° BTDC) in AFS15 detects an intake air flow A _1, to calculate a basic fuel injection quantity Pw ₁ based on the detected intake air flow rate A ₁ and the engine rotational speed Ne _1. Then, injects fuel directly Pw ₁ in the combustion chamber 3 from the injector 9 at a predetermined timing according to the operating state of the intake stroke. By calculating the fuel injection quantity Pw ₁ to predict the amount of intake air in the intake stroke this way the intake air flow rate A ₁ of the exhaust stroke end engine rotational speed Ne ₁ Tokyo, at any time from the beginning of the intake stroke Fuel injection becomes possible.

However, at the end of the exhaust stroke (365 ° BTDC) at which the intake air flow rate A ₁ is detected, the change in the boost is still small, and the boost largely increases during the subsequent intake stroke, and the intake air amount increases. . Therefore, the fuel injection quantity Pw calculated based on the intake air flow A _{1
In the case of 1} , the intake air amount is too small, and the air-fuel ratio becomes leaner than the target air-fuel ratio.

However, in the present control device, at the end of the intake stroke (185 ° BTDC), the intake air flow rate A
₂ is detected and A ₂ / Ne ₂ at the end of the intake stroke is compared with A ₁ / Ne ₁ at the end of the exhaust stroke, and an increase ΔA /
By predicting the amount of increase in the intake air amount from Ne to calculate the corrected fuel quantity Pw ₂ corresponding to .DELTA.A / Ne. Then, the injector 9 is immediately controlled to inject the correction fuel directly into the combustion chamber 3. As a result, the shortage of the fuel injection amount with respect to the intake air amount is resolved, and operation at the target air-fuel ratio becomes possible. At the end of the intake stroke (185 ° BTDC), the corrected fuel amount P
By calculating the w _2, allows injection correction fuel from the intake stroke end, can be sufficient promotion of mixing of the premixture of fuel Pw ₁ injected into the combustion chamber 3 during the intake stroke become.

As described above, according to the control device for the direct injection internal combustion engine, the intake air flow rate A2 is detected at the end of the intake stroke (185 ° BTDC), and A ₂ at the end of the intake stroke is detected.
/ Ne ₂ is compared with A ₁ / Ne ₁ at the end of the exhaust stroke, and the correction fuel Pw ₂ corresponding to the increase ΔA / Ne is directly injected into the combustion chamber 3. There is an advantage that the operation at the target air-fuel ratio becomes possible by eliminating the shortage of the fuel injection amount with respect to the air amount.

Further, a control device for a main injection type internal combustion engine is provided.
According to the corrected fuel Pw from the end of the intake stroke,_TwoInjection of
Enabled and the fuel injected into the combustion chamber 3 during the intake stroke
Pw ₁Of the mixture with the premixed gas
Thus, there is an advantage that deterioration of exhaust gas performance is prevented.
Note that the present invention is not limited to the above-described embodiment.
In other words, various modifications may be made without departing from the spirit of the present invention.
It goes without saying that it can be applied. For example, on
The configuration of the direct injection internal combustion engine described above is merely an example.
Injection of fuel directly into the combustion chamber at least during the intake stroke
Any in-cylinder injection type internal combustion engine may be used.

In the above-described embodiment, the detection timing of the intake air flow rate by the air flow sensor is also the same as the one before the 180 ° BTDC by 5 ° at the end of the intake stroke.
Although 85 ° BTDC is used, the timing is not limited to this, and any timing may be used as long as corrected fuel can be injected from the end of the intake stroke. Further, in the above-described embodiment, the ratio A ₂ / Ne ₂ of the intake air flow rate A ₂ and the engine rotation speed Ne ₂ detected at the end of the intake stroke is substituted for the intake air amount. The intake air flow rate may be continuously detected until the end of the stroke, and the detected intake air flow rate may be sequentially integrated to calculate the actual intake air amount. In this case, a more accurate corrected fuel amount may be calculated. Can be calculated.

Further, the means for detecting the amount of intake air is not limited to the above-described air flow sensor, and other detecting means such as a boost pressure sensor and an in-cylinder pressure sensor may be used.

[0034]

As described above in detail, according to the control apparatus for a direct injection internal combustion engine of the present invention, the correction amount is determined based on the intake air amount detected by the intake air amount detecting means by the end of the intake stroke. The correction amount of the fuel is calculated by the calculation means, and the fuel injection means is controlled by the second fuel injection control means so as to inject the calculated amount of correction fuel into the combustion chamber from the end of the intake stroke. Eliminating the shortage of the fuel injection amount with respect to the intake air amount makes it possible to operate at the target air-fuel ratio, and further, it becomes possible to inject corrected fuel from the end of the intake stroke, and the fuel is injected into the combustion chamber during the intake stroke. There is an advantage that the mixing of the fuel with the premixed gas is sufficiently promoted to prevent deterioration of exhaust gas performance.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a control device for a direct injection internal combustion engine as one embodiment of the present invention.

FIG. 2 is a flowchart illustrating a control flow according to a control device for a direct injection internal combustion engine as one embodiment of the present invention.

FIG. 3 is a flowchart showing a control flow according to a control device for a direct injection internal combustion engine as one embodiment of the present invention.

FIG. 4 is a time chart for explaining an operation effect at the time of intake stroke injection according to the control apparatus for a direct injection internal combustion engine as one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine (in-cylinder injection type internal combustion engine) 3 Combustion chamber 9 Injector (fuel injection means) 15 Air flow sensor (intake air amount detection means) 34 Injection amount calculation means 35 First fuel injection control means 36 Correction amount calculation means 37 Two fuel injection control means

Continued on the front page (72) Inventor Katsunori Ueda 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Hiroki Tamura 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation In-house (72) Inventor Kazuchika Tajima 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation F-term (reference) 3G301 HA01 HA04 HA16 JA21 JA22 LB04 MA12 MA19 MA20 MA26 NC04 PA01Z PA11Z PC02Z PE01Z PE03Z

Claims (1)

[Claims] 1. A control device for a direct injection internal combustion engine for injecting fuel directly into a combustion chamber at least during an intake stroke, comprising: fuel injection means for injecting fuel directly into the combustion chamber; Injection amount calculation means for calculating an injection amount of fuel; first fuel injection control means for controlling the fuel injection means to inject the amount of fuel calculated by the injection amount calculation means into the combustion chamber during an intake stroke. An intake air amount detecting means for detecting an intake air amount; a correction amount calculating means for calculating a fuel correction amount based on the intake air amount detected by the intake air amount detecting means by the end of the intake stroke; A second fuel injection control means for controlling the fuel injection means so as to inject the amount of correction fuel calculated by the correction amount calculation means into the combustion chamber from the end of the intake stroke. Inside Control device for injection type internal combustion engine.