JPH1068337A - Fuel control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure constantly excellent startability, even in an internal combustion engine capable of injecting toward a combustion chamber both in a fuel pressure of a low pressure and of a high pressure. SOLUTION: An amount of fuel fed from a fuel feed means of a fuel injection valve is increased comparing with a reference amount at the starting of operation of an internal combustion engine (S12). However, the increased fuel amount is corrected by a fuel amount correction means when an internal combustion engine is brought into a complete explosion state (S10, S20, S22). Further, a correction amount of a fuel amount by the correction means is varied by a fuel correction amount varying means at steps S20 and S24 when a fuel pressure is switched from a low pressure to a high pressure by a fuel pressure switching means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control system for an internal combustion engine, and more particularly, to a fuel control technique for starting an internal combustion engine.

[0002]

2. Related Art In an internal combustion engine, immediately after starting, the ambient temperature of the fuel is low, and it is difficult for the fuel to vaporize. Therefore, usually, immediately after the start of the internal combustion engine, the fuel injection amount injected from the fuel injection valve is temporarily increased, whereby the fuel amount contributing to combustion is sufficiently ensured. .

[0003] From the point where combustion is completely exploded, until the combustion becomes stable, the temporarily increased fuel amount is gradually reduced, and finally the fuel amount is reduced to a reference fuel according to the operating state of the internal combustion engine. I try to return to the amount. As a result, the startability of the internal combustion engine is improved.

[0004]

However, in recent years,
In order to reduce harmful exhaust gas components and improve fuel efficiency, various direct injection gasoline engines that directly inject fuel into a combustion chamber have been proposed instead of the conventional intake pipe injection type.
In-cylinder injection-type gasoline engines are capable of injecting fuel not only in the intake stroke but also in the compression stroke. ing.

[0005] Even in such a gasoline engine, as described above, the fuel amount is temporarily increased immediately after the engine is started, and the increased fuel amount is gradually reduced when a complete explosion occurs. Is preferred. However, in such a gasoline engine that can raise the fuel pressure not only at low pressure but also at high pressure, it is low pressure at the start of starting, but it becomes a complete explosion state, and the increased fuel amount has not yet reached the reference fuel amount. Before returning, the fuel pressure may be switched to a high pressure depending on the operation state or the like.

As described above, if the fuel pressure is increased while the amount of fuel is increased, the characteristics of the fuel are as follows: the higher the pressure, the smaller the particle size and the atomization proceeds. Is increased, and the increased amount of fuel may become excess fuel. The surplus fuel causes the air-fuel ratio to become over-rich, which may deteriorate the startability of the engine, which is not preferable.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to always ensure good startability even in an internal combustion engine that can inject fuel into a combustion chamber at a low or high fuel pressure. It is an object of the present invention to provide a fuel control device for an internal combustion engine.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a fuel supply means capable of supplying fuel to a fuel injection valve at a low or high pressure, and a fuel supply means. The fuel pressure of the supplied fuel is set to a low pressure at the start of the operation of the internal combustion engine, while the fuel pressure is supplied to the fuel injection valve from the fuel supply means after the start of the operation. Means for increasing the fuel amount relative to a reference amount at the start of operation of the internal combustion engine, complete explosion state detection means for detecting a complete explosion state after the start of operation of the internal combustion engine, and complete explosion state detection means When the complete explosion state is detected, a fuel amount correction means for correcting the increased fuel amount, and a fuel pressure of the fuel supplied from the fuel supply means by the fuel pressure switching means is changed from a low pressure to a high pressure. When switched, it is characterized in that a fuel correction amount changing means for changing the correction amount by the fuel amount correcting means.

Therefore, when the internal combustion engine starts operating, the fuel amount is increased with respect to the reference amount. When the complete explosion state is detected, the increased fuel amount is corrected by the fuel amount correcting means. You. Further, when the fuel pressure of the fuel supplied from the fuel supply means is switched from the low pressure to the high pressure by the fuel pressure switching means, the correction amount by the fuel amount correction means is changed by the fuel correction amount changing means.

As a result, when the fuel pressure is switched from low pressure to high pressure, atomization of the fuel proceeds and the amount of fuel contributing to combustion increases, so that there is a tendency that the fuel becomes excessive and overrich. The over-rich state can be prevented, and the startability of the internal combustion engine is improved. Further, in the invention of claim 2, a fuel supply means for adjusting the fuel pressure to a fuel injection valve from a low pressure to a high pressure and supplying the fuel, and the fuel pressure of the fuel supplied by the fuel supply means at the start of operation of the internal combustion engine A fuel pressure control means capable of continuously variably controlling the fuel pressure to a high pressure according to an operation state after the operation is started; a fuel pressure detection means for detecting a fuel pressure of fuel supplied by the fuel supply means; Fuel increasing means for increasing the amount of fuel supplied from the supply means to the fuel injection valve with respect to a reference amount at the start of operation of the internal combustion engine; and complete explosion state detection for detecting a complete explosion state after the start of operation of the internal combustion engine Means, fuel amount correction means for correcting the increased fuel amount when the complete explosion state is detected by the complete explosion state detection means, and fuel detected by the fuel pressure detection means. There is characterized in that a when a predetermined pressure, the fuel correction amount changing means for changing the correction amount by the fuel amount correcting means.

Therefore, when the internal combustion engine starts operating, the fuel amount is increased relative to the reference amount. When the complete explosion state is detected, the increased fuel amount is corrected by the fuel amount correcting means. You. Further, when the fuel pressure detecting means detects that the fuel pressure of the fuel supplied from the fuel supplying means has changed from a low pressure to a predetermined high pressure, the correction amount by the fuel amount correcting means is changed by the fuel correction amount changing means.

As a result, when the fuel pressure is changed from a low pressure to a high pressure, atomization of the fuel proceeds and the amount of fuel contributing to the combustion increases, so that there is a tendency that the fuel becomes excessive and an over-rich state occurs. The over-rich state can be prevented, and the startability of the internal combustion engine is improved. Further, in the invention according to claim 3, the fuel amount correction means gradually reduces the increased fuel amount to the reference amount when the complete explosion state is detected by the complete explosion state detection means. It is characterized by.

Therefore, when the internal combustion engine starts to operate, the fuel amount is increased with respect to the reference amount. When the complete explosion state is detected, the increased fuel amount is increased by the fuel amount correction means. Until then, the weight loss is corrected satisfactorily. Further, in the invention according to claim 4, the fuel correction amount changing means changes the degree of correction of the fuel amount corrected by the fuel amount correction means to a larger extent and continues the correction.

Therefore, when the fuel pressure of the fuel supplied from the fuel supply means changes from a low pressure to a high pressure, the correction amount by the fuel amount correction means is further changed by the fuel correction amount changing means. As a result, when the fuel pressure is changed from a low pressure to a high pressure, atomization of the fuel proceeds and the amount of fuel contributing to the combustion increases. The state is suitably prevented, and the startability of the internal combustion engine is improved.

According to a fifth aspect of the present invention, the fuel correction amount changing means subtracts a fixed amount of the fuel amount corrected by the fuel amount correction means and continues the correction. Therefore, when the fuel pressure of the fuel supplied from the fuel supply unit changes from a low pressure to a high pressure, a fixed amount is subtracted from the fuel amount corrected by the fuel amount correction unit by the fuel correction amount changing unit.

Thus, when the fuel pressure is changed from a low pressure to a high pressure, atomization of the fuel proceeds and the amount of fuel contributing to combustion increases, so that there is a tendency that the fuel becomes excessive and an over-rich state occurs. Such an overrich state is more suitably prevented, and the startability of the internal combustion engine is improved. Further, in the invention according to claim 6, the fuel amount correcting means includes a first fuel amount correcting means.
And a second fuel amount correcting means capable of correcting the fuel amount as a whole to be smaller than the first fuel amount correcting means. The complete explosion state is detected by the complete explosion state detecting means. When detected, the first fuel amount correction means is selected to correct the increased fuel, and the fuel correction amount changing means selects the second fuel amount correction means to correct the increased fuel. It is characterized by continuing.

Therefore, when the fuel pressure of the fuel supplied from the fuel supply means changes from a low pressure to a high pressure, the second fuel amount can be corrected to be smaller than the first fuel amount correction means.
The fuel amount is corrected based on the fuel amount correcting means. As a result, when the fuel pressure is changed from a low pressure to a high pressure, atomization of the fuel proceeds, and the amount of fuel contributing to combustion increases.
Such an over-rich state is more suitably prevented, and the startability of the internal combustion engine is improved.

[0018]

An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a fuel control device for an internal combustion engine according to the present invention mounted on a vehicle. Hereinafter, the configuration of the internal combustion engine and its fuel control device will be described with reference to FIG.

The engine 1 is of a type that directly injects fuel into a combustion chamber, and is capable of performing fuel injection in a compression stroke (late injection mode) as well as fuel injection in an intake stroke (first injection mode). An in-cylinder in-line four-cylinder gasoline engine is applied. In the in-cylinder injection type engine 1, further, combustion at a lean air-fuel ratio, that is, a lean air-fuel ratio is possible. Therefore, in this engine 1,
The combustion chamber, intake device and exhaust gas recirculation (EGR) device for exhaust gas recirculation (EGR) are designed exclusively for in-cylinder injection. It is said that operation at a lean air-fuel ratio is feasible.

The cylinder head 2 of the engine 1 is also provided with an electromagnetic fuel injection valve 4 together with an ignition plug 3 for each cylinder, whereby fuel is directly injected into the combustion chamber 5. ing. On the top surface of the piston 7 slidably held by the cylinder 6, a hemispherical depression, that is, a cavity 8 is formed at a position where the fuel spray from the fuel injection valve 4 reaches in the latter half of the compression stroke. ing. The compression ratio of the engine 1 is set higher (for example, about 12) than that of the intake pipe injection type.
A DOHC 4-valve valve mechanism is adopted as a valve operating mechanism. An intake camshaft 11 and an exhaust camshaft 12 are rotatably provided above the cylinder head 2 to drive intake and exhaust valves 9 and 10, respectively. Supported.

The cylinder head 2 has both camshafts 1
An intake port 13 is formed in a substantially upright direction so as to pass through between the intake ports 1 and 12, and the intake flow passing through the intake port 13 is reversed in the combustion chamber 5 in the opposite direction to the normal tumble flow. It is possible to generate a tumble flow. On the other hand, the exhaust port 14 is formed in a substantially horizontal direction similarly to a normal engine, but a large-diameter exhaust gas recirculation port, that is, an EGR port 15 is branched obliquely downward.

In the drawing, reference numeral 16 denotes a water temperature sensor for detecting a cooling water temperature Tw. Reference numeral 17 denotes a vane type crank angle sensor that outputs a crank angle signal SGT at a predetermined crank position (for example, 5 ° BTDC and 75 ° BTDC) of each cylinder. The engine rotation speed Ne can be detected based on the Reference numeral 19 denotes an ignition coil that outputs a high voltage to the ignition plug 3. A camshaft that rotates at half the number of revolutions of the crankshaft is provided with a cylinder discrimination sensor (not shown) that outputs a cylinder discrimination signal SGC. It is identifiable whether or not it is.

A throttle body 23, a stepper motor type # 1 ABV (first air bypass valve) 24 functioning as an intake air amount correction means 24, and an air flow sensor 32 are connected to the intake port 13 via an intake manifold 21 having a surge tank 20. And an intake pipe 25 provided with an air cleaner 22. The intake pipe 25 is provided with a large-diameter air bypass pipe 26 for bypassing the throttle body 23 and sucking air into the intake manifold 21. The large-diameter air bypass pipe 26 has a linear solenoid type large # 2ABV (second
An air bypass valve (27) is provided. The air bypass pipe 26 has a passage area similar to that of the intake pipe 25, and when the # 2 ABV 27 is fully opened, the engine 1
The required amount of intake in the low to medium speed range is possible.

The throttle body 23 has a butterfly type throttle valve 28 for opening and closing the flow path, and a throttle position sensor (a throttle valve opening sensor as a throttle valve opening sensor for detecting the opening of the throttle valve 28, that is, the throttle opening θth. Hereinafter, referred to as TPS) 29,
Detecting the fully closed state of the throttle valve 28 and detecting the engine 1
And an idle switch 30 for detecting the idling state of the vehicle. Actually, the TPS 29 outputs a throttle voltage Vth corresponding to the throttle opening θth, and the throttle opening θth is recognized based on the throttle voltage Vth.

The air flow sensor 32 detects the amount of intake air Qa, and for example, a Karman vortex flow sensor is used. On the other hand, the exhaust port 14
O ₂ sensor 40 capable of detecting the actual air-fuel ratio (actual A / F)
An exhaust pipe 43 provided with a three-way catalyst 42 and a muffler (not shown) is connected via an exhaust manifold 41 to which is attached. The above-mentioned EGR port 15 is connected to the upstream of the intake manifold 21 via a large-diameter EGR pipe 44, and a stepper motor type EGR valve 45 is provided in the pipeline.

The fuel tank 50 is installed at the rear of the vehicle (not shown). The fuel stored in the fuel tank 50 is sucked up by an electric low-pressure fuel pump (fuel supply means) 51 and supplied to the engine 1 via a low-pressure feed pipe 52. The fuel pressure in the low-pressure feed pipe 52 is regulated to a relatively low pressure (low fuel pressure) by a first fuel pressure regulator 54 interposed in the return pipe 53. The fuel supplied to the engine 1 is supplied to a high-pressure fuel pump (fuel supply means) attached to the cylinder head 2.
By 55, the fuel is supplied to each fuel injection valve 4 via a high pressure feed pipe 56 and a delivery pipe 57.

The high-pressure fuel pump 55 is, for example, of a swash plate axial piston type, is driven by the camshaft 12, and has a pressure of 5 MPa even when the engine 1 is idling.
A discharge pressure of 7 MPa or more can be generated. The fuel pressure in the delivery pipe 57 is equal to the return pipe 5
The pressure is adjusted to a relatively high pressure (high fuel pressure) by the second fuel pressure regulator 59 interposed in the pipeline 8.

In the figure, reference numeral 60 denotes the second fuel pressure regulator 5.
9 is an electromagnetic fuel pressure switching valve (fuel pressure switching means). The fuel pressure switching valve 60 is capable of relieving fuel in the ON state, thereby reducing the fuel pressure in the delivery pipe 57 to a low fuel pressure. Reference numeral 61 denotes a return pipe for returning a part of the fuel used for lubrication and cooling of the high-pressure fuel pump 55 to the fuel tank 50.

In the cabin of the vehicle, an input / output device, a storage device (RO) for storing control programs, control maps, and the like are provided.
M, RAM, BURAM, etc.), central processing unit (CP
U), an ECU (Electronic Control Unit) 70 including a timer counter and the like is installed, and the ECU 70 performs comprehensive control of the engine 1. ECU7
The various sensors described above are connected to the input side of 0, and detection information from these various sensors is input. E
The CU 70 determines the fuel injection mode, the fuel injection amount, the ignition timing, the EGR gas introduction amount, and the like based on the detected information, and determines the fuel injection valve 4, the ignition coil 19, the E
The drive control of the GR valve 45 and the like is performed. Although not described, the input side of the ECU 70 is connected to a large number of switches and sensors (not shown) in addition to the various sensors described above. Etc. are connected.

Next, the engine 1 configured as described above
Operation at the time of engine start in the fuel control device of
The fuel increase control at the time of starting the engine according to the present invention will be described. When the engine 1 is stopped and in a cold state,
When the driver turns on the ignition key, the ECU
70 turns on the low-pressure fuel pump 51 and the fuel pressure switching valve 60 to supply low fuel pressure fuel to the fuel injection valve 4.

When the driver starts the ignition key, the engine 1 is cranked by the starter motor (not shown) and the engine 1 is started.
The CU 70 starts combustion control including fuel control.
At this time, the ECU 70 selects the first-stage injection mode (that is, the intake stroke injection mode) and increases the amount of fuel so as to achieve a relatively rich air-fuel ratio and injects the fuel. That is,
The ECU 70 performs fuel increase control. This is based on the fact that the fuel vaporization rate is low when the engine is cold. That is, by increasing the amount of fuel, a sufficient amount of fuel that contributes to combustion is secured. The ECU 70 closes the # 2ABV 27 at the time of such a start. Therefore, in this case, the intake air to the combustion chamber 5 is taken through the gap of the throttle valve 28 and the # 1 ABV 24.

The control procedure of the fuel increase control executed by the ECU 70 will be described below. Here, three embodiments of Examples 1 to 3 will be described as fuel increase control. First, a first embodiment will be described. Referring to FIG. 2, there is shown a flowchart illustrating a fuel increase control routine according to the first embodiment, which will be described below with reference to FIG.

In step S10, the engine 1 is cranked and started to operate, and whether or not the engine 1 is being started, that is, in an initial explosion or continuous explosion state until a complete explosion state in which ignition of fuel is ensured. It is determined whether or not there is. The complete explosion state is determined by, for example, whether or not the engine rotation speed Ne based on information from the crank angle sensor 17 has reached a predetermined value Ne2 (complete explosion state detection means). If the determination result is true (Yes) and it is determined that the engine 1 is being started, the process proceeds to step S12.

In step S12, the fuel injection amount F is set to the starting fuel amount F0. That is, the fuel is increased and injected so as to have a relatively rich air-fuel ratio (fuel increasing means).
In this case, the starting fuel amount F0 is set based on the cooling water temperature information Tw from the water temperature sensor 16, and the like. In the next step S14, a fuel increase coefficient KST corresponding to the starting fuel amount F0 is set as an initial value of the fuel increase coefficient KST. The fuel increase coefficient KST is a fuel increase ratio set as a reference value 1 in the case of a reference fuel injection amount FB described later.

If the combustion is completely exploded and the engine is not being started, the result of the determination in step S10 is determined to be false (No), and the process proceeds to step S16. In step S16,
It is determined whether or not the engine is in the start release state. The start release state refers to a state in which the cranking of the engine 1 is successfully released. For example, if the engine 1 is not in the complete explosion state when the cranking of the engine 1 is released, the determination result of step S16 is determined to be false.
In such a case, the occurrence of an engine stall or the like is predicted. Then, the process proceeds to step S18, in which the fuel injection amount F is set to 0, and the fuel injection is stopped. On the other hand, if the result of the determination in step S16 is true and it is determined that the cranking of the engine 1 has been successfully released, the process proceeds to step S20.

In step S20, it is determined whether the fuel pressure is in a low fuel pressure state. Normally, immediately after the start of the operation of the engine 1, the low-pressure fuel pump 51 and the fuel pressure switching valve 60 are turned on, and the fuel pressure is reduced to a low fuel pressure by the first fuel pressure regulator 54. Then, after that, the combustion becomes complete explosion and the engine rotation speed Ne rises, for example, when it reaches a predetermined value Ne1 (for example, 1200 rpm), the fuel pressure switching valve 6
0 is turned off, whereby the fuel pressure is adjusted to a high fuel pressure by the second fuel pressure regulator 59.

That is, in step S20, it is determined whether or not the fuel pressure switching valve 60 is kept on according to the engine speed Ne and the fuel pressure is low.
If the result of the determination in step S20 is true and the fuel pressure is determined to be low, the process proceeds to step S22. In step S22, the fuel increase coefficient KST set to the initial value as described above is reduced by the following equation (1) (fuel amount correcting means).

KST = KST-α (1) where α is a constant, which is set sufficiently smaller than the initial value of the fuel increase coefficient KST. Then, in the next step S26, the fuel injection amount F is calculated from the following equation (2).

F = FB ・ KST ・ K1 + K2 (2) where K1 and K2 are various fuel correction coefficients, and FB is
This is a reference fuel injection amount set based on the engine speed Ne and the engine load. That is, here, the fuel injection amount F set as the starting fuel amount F0 in step S12 is reduced according to the decrease in the fuel increase coefficient KST and is updated to a new fuel injection amount F.

After the fuel injection amount F is updated in this manner, it is next determined in step S28 whether or not the fuel increase coefficient KST is equal to the reference value 1. The case where the fuel increase coefficient KST is the reference value 1 means that the fuel injection amount F becomes the reference fuel injection amount FB, as is apparent from the equation (2). If the decision result in the step S28 is false,
If the fuel increase coefficient KST has not yet reached the reference value 1, this routine is repeatedly executed. Then, while the determination result of step S20 is true through steps S10 and S16, step S22 is executed, and the fuel increase coefficient KST is continuously subtracted by the above equation (1). As a result, the once increased fuel injection amount F is gradually and satisfactorily returned to the normal reference fuel injection amount FB as the engine rotation speed Ne increases.

When the engine speed Ne rises to a predetermined value Ne1 and the fuel pressure switching valve 60 is turned off, the fuel pressure is set to a high fuel pressure, so that the determination result in step S20 becomes false, and in this case, Then, the process proceeds to step S24. In step S24, the fuel increase coefficient KST is reduced by the following equation (3) (fuel correction amount changing means).

KST = KST-β (3) where β is a constant similar to the above constant α, but this constant β is set to a value larger than the constant α (β>
α). That is, in the equation (3), the decreasing rate of the fuel increase coefficient KST is increased. Then, in the same manner as described above, the fuel injection amount F is calculated in step S26,
At 28, it is determined whether or not the fuel increase coefficient KST is equal to the reference value 1.

Normally, when the fuel pressure is set to a high fuel pressure, the high fuel pressure is maintained as long as the engine 1 is in an operating state. Therefore, the determination result of step S20 is false once, and then the routine is repeatedly executed. Then, step S24 is performed.
, The fuel increase coefficient KST continues to be subtracted by the constant β.
Then, the fuel increase coefficient KST is subtracted to the reference value 1, and
If the determination result of step S28 is true, the fuel injection amount F is set to the normal reference fuel injection amount FB, and the routine ends. Thereby, the fuel control at the time of starting is completed.

Referring now to FIG. 5, there is shown a time chart of the time change of the fuel increase coefficient KST at the time of starting the engine 1. The fuel pressure change of the fuel increase coefficient KST in the first embodiment is shown. The subsequent time change is indicated by the two-dot chain line. The figure shows the fuel increase coefficient KST when the calculation is continued by the above equation (1) as in the related art even after the fuel pressure is switched.
As shown in the figure, in the case of the first embodiment, the fuel injection amount F is once set to the start-time fuel amount F0 and is set to a relatively large value. When the fuel pressure is switched from the low fuel pressure to the high fuel pressure, the increased fuel increase coefficient KST has a slope larger than the solid line, that is, has a larger tailing speed than at the time of the low fuel pressure, and rapidly decreases toward the reference value 1. ing. That is, the fuel injection amount F rapidly decreases toward the reference fuel injection amount FB.

Therefore, when the fuel pressure is switched from the low fuel pressure to the high fuel pressure, the fuel particle diameter becomes smaller, so that the atomization of the fuel proceeds and more fuel contributes to the combustion. If the fuel pressure is increased while maintaining the fuel pressure larger than the amount FB, a large amount of surplus fuel is generated, the air-fuel ratio tends to be over-rich, and there is a possibility that combustion may deteriorate. This is suitably prevented, and the startability of the engine 1 is improved.
In addition, by reducing the fuel injection amount F, the emission of unburned fuel is suppressed, and the fuel efficiency is improved.

The dashed line in FIG. 5 indicates the case of the second embodiment, and the broken line indicates the case of the third embodiment, which will be described later. Next, a second embodiment will be described. Referring to FIG. 3, there is shown a flowchart illustrating a fuel increase control routine according to the second embodiment, which will be described below with reference to FIG.

Since steps S110 to S118 in FIG. 3 are the same as steps S10 to S18 in FIG. 2 in the first embodiment,
Here, the description is omitted, and the steps after step S120 will be described. However, in the second embodiment, as will be described later, two fuel increase coefficients, a fuel increase coefficient (first fuel amount correction means) KST1 and a fuel increase coefficient (second fuel amount correction means) KST2, are calculated. . Therefore, in step S114, an initial value is set for each of the fuel increase coefficient KST1 and the fuel increase coefficient KST2 according to the starting fuel amount F0 (however, KST1> KST2).

In step S120, similarly to step S20 in FIG. 2, it is determined whether the fuel pressure is low. If the determination result of step S120 is true and the fuel pressure is determined to be low fuel pressure, then step S12 is performed.
Proceed to 2. In step S122, the actually used fuel increase coefficient KST is obtained by the following equation (4).

KST = KST1 (4) That is, when the fuel pressure is in the low fuel pressure state, the fuel increase coefficient KST1 is selected as the fuel increase coefficient KST.
Then, in the next step S126, the first embodiment
As in step S26, the fuel injection amount F is calculated by the following equation.
It is calculated from (5).

F = FB ・ KST ・ K1 + K2 (5) In the next step S128, the fuel increase coefficient KST1 is calculated by the following equation.
The fuel loss is corrected by (6) (fuel amount correcting means). KST1 = KST1−α (6) This equation (6) is similar to the equation (1) in the case of the first embodiment. However, the constant α does not necessarily have to match that of the equation (1).

In step S130, the fuel increase coefficient KST2 is reduced by the following equation (7) in the same manner as in the above equation (6). KST2 = KST2−α (7) Also in this equation (7), the constant α does not necessarily have to match that of the equation (1). Also, this constant α
May be different from the constant α in the above formula (6).

Further, in step S132, similarly to step S28 in FIG. 2, the fuel increase coefficient K
It is determined whether or not ST is the reference value 1. When the determination result is false and the fuel increase coefficient KST has not yet reached the reference value 1, the routine is repeatedly executed. Then, while the determination result of step S120 is determined to be true after steps S110 and S116, step S122 is executed, and the fuel increase coefficient KST is kept as the fuel increase coefficient KST1 by the above equation (4).

When the engine rotation speed Ne increases to the predetermined value Ne1 and the fuel pressure switching valve 60 is turned off, the fuel pressure is set to a high fuel pressure, so that the determination result in step S120 becomes false, and in this case, Next, step S12
Proceed to 4. In step S124, the actually used fuel increase coefficient KST is obtained by the following equation (8) (fuel correction amount changing means).

KST = KST2 (8) That is, when the fuel pressure is high, the fuel increase coefficient KST2 smaller than the fuel increase coefficient KST1 is selected as the fuel increase coefficient KST. Then, in the same manner as described above, the fuel injection amount F is calculated in step S126, the fuel increase coefficients KST1 and KST2 are subtracted in steps S128 and S130, and whether or not the fuel increase coefficient KST is the reference value 1 is determined in step S132. Is determined.

When the fuel increase coefficient KST is subtracted to the reference value 1 and the result of the determination in step S132 is true, the fuel injection amount F is set to the normal reference fuel injection amount FB, and the routine ends. Here, referring again to FIG. 5, the time change of the fuel increase coefficient KST1 in the case of the second embodiment is indicated by a solid line (the same as in the above-described conventional case), and the fuel increase coefficient
The time change of ST2 is indicated by a dashed line. As described above, in the case of the second embodiment, the fuel injection amount is once set to the starting fuel amount F0, and the fuel increase coefficient KS is set to a large value.
T is, when the fuel pressure switches from low fuel pressure to high fuel pressure,
From the fuel increase coefficient KST1 to the fuel increase coefficient KST2 (KST1> KS
It has been switched to T2). That is, the fuel increase coefficient KST
Is significantly reduced when the fuel pressure is switched from low fuel pressure to high fuel pressure. Thus, as in the case of the first embodiment, the fuel injection amount F is promptly set to the reference fuel injection amount FB, and the same effects as in the first embodiment can be obtained.

In the second embodiment, unlike the first embodiment, the fuel increase coefficient KST is reduced at the moment when the fuel pressure is switched from the low fuel pressure to the high fuel pressure. Therefore, in this case, it is possible to prevent the over-rich state from being reached very quickly, and the startability of the engine 1 is further improved. Next, a third embodiment will be described.

Referring to FIG. 4, there is shown a flowchart illustrating a fuel increase control routine according to the third embodiment, which will be described below with reference to FIG. Step S in FIG.
Steps 210 to S218 are also performed in the first embodiment.
Are the same as steps S10 to S18 in FIG.
20 will be described.

In step S220, similarly to step S20 in FIG. 2, it is determined whether or not the fuel pressure is in a low fuel pressure state. If the determination result of step S220 is true and the fuel pressure is determined to be low fuel pressure, then step S22 is performed.
Proceed to 2. In step S222, the fuel increase coefficient KST is reduced by the following equation (9) in the same manner as in the first embodiment (fuel amount correcting means).

KST = KST-α (9) Then, in the next step S230, the fuel injection amount F is calculated from the following equation (10), as in the first and second embodiments. F = FB ・ KST ・ K1 + K2 (10) Further, in step S232, the fuel increase coefficient KST is set to the reference value 1 in the same manner as in step S28 in FIG.
Is determined. When the determination result is false and the fuel increase coefficient KST has not yet reached the reference value 1, the routine is repeatedly executed. Then, step S21
While the determination result of step S220 is true through 0 and S216, step S222 is executed, and the fuel increase coefficient KST is continuously subtracted by the above equation (9).

When the engine speed Ne rises to the predetermined value Ne1 and the fuel pressure switching valve 60 is turned off, the fuel pressure is set to a high fuel pressure, so that the result of the determination in step S220 becomes false. Next, step S22
Proceed to 4. In step S224, it is determined whether or not the fuel pressure has just been switched to the high fuel pressure. If the determination result is true and the fuel pressure has just been switched to the high fuel pressure,
Next, the process proceeds to step S226.

In step S226, the fuel increase coefficient KST
Is subtracted by a predetermined value (constant amount) γ (fuel correction amount changing means). This predetermined value γ is a value sufficiently larger than the constant α. Then, the routine is repeatedly executed through steps S230 and S232, and then step S22 is executed.
When 4 is executed, it is no longer immediately after the fuel pressure is switched to the high fuel pressure. Therefore, in this case, the result of the determination in step S224 is false, and then step S228
Proceed to.

In step S228, the fuel increase coefficient KST
Is corrected by the following equation (11). KST = KST−α (11) This equation (11) is similar to the above equation (9), but the constant α
Do not always have to match. And
In the same manner as described above, the fuel injection amount F is calculated in step S230, and it is determined in step S232 whether the fuel increase coefficient KST is equal to the reference value 1. When the fuel increase coefficient KST is subtracted to the reference value 1 and the result of the determination in step S232 is true, the fuel injection amount F is set to the normal reference fuel injection amount FB, and the routine ends.

Here, referring again to FIG. 5, the broken line shows the time change of the fuel increase coefficient KST after the high fuel pressure switching in the case of the third embodiment. As described above, in the case of the third embodiment, the fuel amount at start-up is once set to F0, and the increased fuel increase coefficient KST is set to the predetermined value γ when the fuel pressure is switched from low fuel pressure to high fuel pressure. Only has been greatly subtracted. Thereby, similar to the cases of the first and second embodiments,
The fuel injection amount F is promptly set to the reference fuel injection amount FB, and the same effect as above can be obtained.

In the third embodiment, the fuel increase coefficient KST is reduced at the moment when the fuel pressure is switched from the low fuel pressure to the high fuel pressure, as in the case of the second embodiment. Therefore, also in the case of the third embodiment, it is possible to prevent the over-rich state from being reached very quickly, and the startability of the engine 1 is improved as compared with the case of the first embodiment. As described above in detail with reference to the first to third embodiments, the fuel control device for an internal combustion engine of the present invention executes the fuel increase control to increase the fuel injection amount that is increased when the engine 1 is started. The fuel increase coefficient KST corresponding to the fuel injection amount F is tailed so as to gradually return F to the normal reference fuel injection amount FB. Further, when the fuel pressure is switched from low fuel pressure to high fuel pressure, the fuel increase amount is increased. The correction amount of the coefficient KST is changed so as to increase the decrease amount.

Therefore, when the fuel pressure is switched from the low fuel pressure to the high fuel pressure, the fuel particle diameter becomes smaller, so that atomization of the fuel proceeds and more fuel contributes to the combustion. If the fuel pressure is increased while the fuel pressure is greatly increased beyond the amount FB, a large amount of surplus fuel is generated, and the air-fuel ratio tends to be over-rich. Is suitably prevented, and the startability of the engine 1 is improved.

Further, by reducing the fuel injection amount F, the discharge of unburned fuel is suppressed, and the fuel efficiency is improved. In the above embodiment, the fuel pressure is switched from low fuel pressure to high fuel pressure by turning off the fuel pressure switching valve 60 based on the engine speed Ne, and the fuel increase coefficient KST is changed based on this switching. For example, in a fuel control device capable of continuously variably controlling the fuel pressure from a low fuel pressure to a high fuel pressure based on operation information such as the engine rotation speed Ne,
Fuel pressure detecting means may be provided to change the fuel increase coefficient KST when the fuel pressure reaches a predetermined high fuel pressure.

Referring to FIG. 6, there is shown a graph showing the relationship between the fuel pressure and the fuel particle size. As shown in FIG. 6, the fuel particle size decreases as the fuel pressure increases.
For example, the fuel pressure when the fuel particle diameter becomes small and stabilizes to a substantially constant value is increased to a predetermined high fuel pressure P1 (for example,
Pa), the switching from the low fuel pressure to the high fuel pressure is determined based on the fact that the fuel pressure has reached the predetermined high fuel pressure P1, and the correction amount of the fuel increase coefficient KST may be changed.

Thus, at a suitable timing when the fuel particle diameter is minimized and the atomization of the fuel is improved, the fuel increase coefficient K
The ST can be changed, so that the air-fuel ratio is prevented from being in an over-rich state when the engine 1 is started, and the startability of the engine 1 is improved. In the above embodiment, the fuel increase coefficient KST is linearly determined based on the equation (1) in the first embodiment, for example, during the low fuel pressure from when the engine 1 is in the complete explosion state until the fuel pressure is switched to the high fuel pressure. To reduce uniformly. However,
It is said that it is better to increase the start-up fuel amount F0, but it is better to reduce the fuel injection amount F to a predetermined amount immediately after the complete explosion state. Therefore, as shown in FIG. 5, while the starting fuel amount F0 is further increased, the fuel increasing coefficient is changed to the predetermined fuel increasing coefficient value KSTX after the complete explosion state until the fuel increasing coefficient KSTX. ', It may be made to change steeply. As a result, the startability of the engine 1 is further improved, which is effective.

Further, in the above embodiment, the fuel control device is applied to the in-cylinder injection type internal combustion engine capable of directly injecting fuel into the combustion chamber. However, the present invention is not limited to this. The present invention may be applied to an intake pipe injection type internal combustion engine capable of switching control.

[0070]

As described in detail above, claim 1 is as follows.
According to the internal combustion engine fuel control device described above, the fuel amount is increased with respect to the reference amount at the start of the operation of the internal combustion engine, but when the complete explosion state is detected, the increased fuel amount is increased. Good correction can be made by the amount correction means. Further, when the fuel pressure of the fuel supplied from the fuel supply means is switched from the low pressure to the high pressure by the fuel pressure switching means, the correction amount by the fuel amount correction means can be suitably changed by the fuel correction amount changing means.

Accordingly, when the fuel pressure is switched from low pressure to high pressure, the fuel is atomized and the amount of fuel contributing to the combustion increases, so that there is a tendency that the fuel becomes excessive and overrich. The over-rich state can be prevented, and the startability of the internal combustion engine can be improved. According to the fuel control device for an internal combustion engine of the second aspect, the fuel amount is increased with respect to the reference amount at the start of the operation of the internal combustion engine. However, when the complete explosion state is detected, the fuel amount is increased. The fuel amount can be satisfactorily corrected by the fuel amount correcting means. Further, when the fuel pressure detecting means detects that the fuel pressure of the fuel supplied from the fuel supply means has changed from a low pressure to a predetermined high pressure, the correction amount by the fuel amount correcting means is suitably changed by the fuel correction amount changing means. I can do it.

Therefore, when the fuel pressure is changed from a low pressure to a high pressure,
As fuel atomization progresses and the amount of fuel contributing to combustion increases, fuel tends to be excessive and tend to be in an over-rich state.However, such an over-rich state can be prevented and the startability of the internal combustion engine is improved. It is possible to do. According to the fuel control device for an internal combustion engine of the third aspect, the fuel amount is increased with respect to the reference amount at the start of the operation of the internal combustion engine. However, when the complete explosion state is detected, the fuel amount is increased. The reduced fuel amount can be gradually reduced to the reference amount by the fuel amount correcting means. That is, it is possible to satisfactorily return the increased fuel amount to the reference amount.

According to the fourth aspect of the present invention, when the fuel pressure of the fuel supplied from the fuel supply means changes from a low pressure to a high pressure, the correction amount by the fuel amount correction means is changed. Further changes can be made by means. Therefore, an over-rich state when the fuel pressure is changed from a low pressure to a high pressure can be suitably prevented, and the startability of the internal combustion engine can be improved.

According to the fuel control apparatus for an internal combustion engine of the present invention, when the fuel pressure of the fuel supplied from the fuel supply means changes from a low pressure to a high pressure, the fuel amount corrected by the fuel amount correction means is used as the fuel amount. A certain amount can be subtracted by the correction amount changing means. Therefore, the over-rich state when the fuel pressure is changed from a low pressure to a high pressure can be more appropriately prevented, and the startability of the internal combustion engine can be improved.

According to the fuel control device for an internal combustion engine of the sixth aspect, when the fuel pressure of the fuel supplied from the fuel supply means changes from a low pressure to a high pressure, the fuel amount is increased by the first fuel amount correction means. The fuel amount can be corrected based on the second fuel amount correcting means that can be corrected small as a whole.
Therefore, the over-rich state when the fuel pressure is changed from a low pressure to a high pressure can be more appropriately prevented, and the startability of the internal combustion engine can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an internal combustion engine and a fuel control device thereof.

FIG. 2 is a flowchart illustrating a fuel increase control routine according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating a fuel increase control routine according to a second embodiment of the present invention.

FIG. 4 is a flowchart illustrating a fuel increase control routine according to a third embodiment of the present invention.

FIG. 5 is a time chart showing a time change of a fuel increase coefficient KST at the time of starting.

FIG. 6 is a graph showing the relationship between fuel pressure and fuel particle size.

[Explanation of symbols]

 Reference Signs List 1 engine 4 fuel injection valve 17 crank angle sensor (complete explosion state detection means) 51 low pressure fuel pump (fuel supply means) 52 low pressure feed pipe 54 first fuel pressure regulator 55 high pressure fuel pump (fuel supply means) 59 second fuel pressure regulator 60 Fuel pressure switching valve (fuel pressure switching means) 70 Electronic control unit (ECU)

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroki Tamura 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation

Claims (6)

[Claims] 1. A fuel supply means capable of supplying fuel to a fuel injection valve at a low or high fuel pressure, and a fuel pressure of the fuel supplied by the fuel supply means is set to a low pressure at the start of operation of an internal combustion engine. Fuel pressure switching means capable of switching to a high pressure according to an operation state after the start of operation; and a fuel increase for increasing a fuel amount supplied to the fuel injection valve from the fuel supply means to a reference amount at the start of operation of the internal combustion engine. Means, a complete explosion state detecting means for detecting a complete explosion state after the start of operation of the internal combustion engine, and correcting the increased fuel amount when the complete explosion state is detected by the complete explosion state detection means. Fuel amount correction means; and when the fuel pressure of the fuel supplied from the fuel supply means is switched from low pressure to high pressure by the fuel pressure switching means, the correction amount by the fuel amount correction means is changed. The fuel control system for an internal combustion engine comprising: the fuel correction amount changing means. 2. A fuel supply means for supplying a fuel to a fuel injection valve with a fuel pressure adjustable from a low pressure to a high pressure, and a fuel pressure of the fuel supplied by the fuel supply means is set to a low pressure at the start of operation of the internal combustion engine. After the start of the operation, a fuel pressure control means capable of continuously variably controlling up to a high pressure according to an operation state; a fuel pressure detection means for detecting a fuel pressure of the fuel supplied by the fuel supply means; Fuel increasing means for increasing a fuel amount supplied to a fuel injection valve with respect to a reference amount at the start of operation of the internal combustion engine; complete explosion state detecting means for detecting a complete explosion state after the start of operation of the internal combustion engine; When the complete explosion state is detected by the complete explosion state detection means, a fuel amount correction means for correcting the increased fuel amount; and a fuel pressure detected by the fuel pressure detection means is a predetermined value. A fuel control device for an internal combustion engine, comprising: fuel correction amount changing means for changing the correction amount by the fuel amount correction means when the pressure becomes high. 3. The fuel amount correcting means gradually reduces the increased fuel amount to the reference amount when the complete explosion state is detected by the complete explosion state detecting means. 3. The fuel control device for an internal combustion engine according to claim 1 or 2. 4. The fuel correction amount changing unit according to claim 1, wherein the correction amount of the fuel amount corrected by the fuel amount correction unit is further changed to continue the correction. A fuel control device for an internal combustion engine according to any one of the preceding claims. 5. The fuel correction amount changing unit according to claim 1, wherein the fuel correction amount changing unit subtracts a fixed amount from the fuel amount corrected by the fuel amount correction unit and continues the correction. Fuel control device for internal combustion engine. 6. The fuel amount correcting means has a first fuel amount correcting means and a second fuel amount correcting means capable of correcting the fuel amount as a whole smaller than the first fuel amount correcting means. And
When the complete explosion state is detected by the complete explosion state detection means, the first fuel amount correction means is selected to correct the increased fuel, and the fuel correction amount changing means includes: 2. The method according to claim 1, wherein the second fuel amount correcting means is selected to continue the correction.
The fuel control device for an internal combustion engine according to any one of claims 1 to 3.