JP3044077B2 - Fuel supply system for turbocharged engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for a supercharged engine having a fuel injection valve for injecting fuel into an intake passage.

[0002]

2. Description of the Related Art Conventionally, as a fuel supply system for a supercharged engine, a fuel injection valve for injecting fuel into an intake port of each cylinder has been provided, and each fuel injection valve has a corresponding fuel injection valve. A so-called sequential injection type in which fuel is injected and supplied in synchronization with intake and exhaust timings is known. And in this kind of fuel supply device,
In order to compensate for the delay caused by the inertia of the fuel spray and to mix the fuel spray and air in the intake port, the injection start timing (hereinafter, referred to as injection timing) of each of the fuel injection valves is set before the intake stroke. Often set. However, as disclosed in Japanese Patent Application Laid-Open No. 58-220933, for example, a fuel injection valve for injecting fuel into an intake port of each cylinder is provided, and during idle operation, the injection timing of each fuel injection valve is set at the intake timing. By setting the valve overlap period (hereinafter referred to as overlap) at the beginning of the stroke and hitting the high-temperature residual gas sucked back to the intake port at the time of overlap and injecting it, the atomization and vaporization of fuel spray is promoted. In some cases, the combustibility is improved.

[0003]

In the above-mentioned publication, the intake pipe negative pressure is high during idling operation,
It utilizes the fact that high-temperature residual gas is sucked back into the intake port at the time of overlap.During normal load operation, especially during high load operation, the negative pressure of the intake pipe decreases and the above cannot be expected. Since the fuel injection amount increases and the injection period becomes longer, in this case, the injection timing is advanced before the intake stroke. However, in the turbocharger system, in the supercharging operation region, the intake air is pressurized and sent to the intake port in a large amount, so that the intake flow velocity becomes considerably high, and the fuel is supplied before the intake stroke as described above. When the fuel is injected, there is a problem that so-called blow-through occurs in which the fuel spray flowing into the combustion chamber together with the intake air having a high flow velocity at the time of the overlap at the beginning of the intake stroke flows out to the exhaust port as it is. Further, in the supercharging operation region, since an output is required and a large amount of fuel is supplied, there is a strong demand to improve vaporization and atomization of the fuel.

The present invention has been made in view of such a point, and an object thereof is to appropriately set a fuel injection timing in a supercharging operation region to vaporize and atomize a fuel spray. It is another object of the present invention to prevent blow-through while improving the output, and to improve the output effectively.

[0005]

Means for Solving the Problems To achieve the above object, a solution taken by the invention of claim 1 is a fuel injection valve which comprises a supercharger and supplies fuel to an intake port of each cylinder. And a fuel supply device for a supercharged engine that supplies fuel from each fuel injection valve in synchronization with intake / exhaust timing of a corresponding cylinder. And a determining means for detecting a load of the engine and determining whether or not the engine is in a supercharging operation area based on the detected load.
Each fuel injection valve is controlled to start fuel injection during a valve overlap period in which both the intake valve and the exhaust valve are open. When it is determined that the fuel injection valve is in the non-supercharging operation region, the injection start timing And control means for controlling the fuel injection valves so that the fuel injection valve is advanced from the injection start timing in the supercharging operation region .

[0006]

With the above arrangement, according to the first aspect of the present invention, when the determination means determines that the engine is in the supercharging operation range, the control means determines that the injection timing of the fuel injection valve is during the overlap period. In the supercharging operation region, the fuel spray injected during the overlap period flows into the combustion chamber as an air-fuel mixture while being mixed with air by a large amount of pressurized, fast-flowing intake air. . Therefore, when the air-fuel mixture (fuel spray) flows into the combustion chamber, it is in the latter half or almost at the end of the overlap period, and the period until the air-fuel mixture flows out to the exhaust port while pushing out the residual gas. Is short, and it is difficult for the air-fuel mixture to flow out of the exhaust port, thereby preventing blow-by. Further, since the mixture is in contact with the high-temperature residual gas when flowing into the combustion chamber, the fuel spray of the mixture is promoted to be vaporized and atomized, and the combustibility is improved. On the other hand, if it is determined by the determining means that the region is not the supercharging operation region, that is, the region is the non-supercharging operation region, the non-supercharging operation region is a low-load region, the intake air flow rate is small, and the mixing with the fuel spray air is performed. Although it is difficult to perform the injection in a short time, the injection timing in this case is advanced by the control means during the overlap period of the supercharging operation region, so that the fuel spray is mixed with the air in the intake port. Sufficiently performed to improve flammability .

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of a supercharged engine provided with a fuel supply device according to an embodiment of the present invention. Although FIG. 1 shows only one cylinder, other cylinders have the same configuration. In FIG. 1, reference numeral 1 denotes an engine. The engine 1 includes a cylinder block 3 forming a cylinder 2, a cylinder head 4 joined to an upper surface of the cylinder block 3, and a piston 5 reciprocating in the cylinder 2. A combustion chamber 6 defined in the cylinder 2 by a lower surface of a cylinder head 4 and a top surface of a piston 5.
Are formed.

An intake passage 7 is connected to the combustion chamber 6,
An intake valve 9 is provided at an opening of the intake port 8 to the combustion chamber 6 at the downstream end of the intake passage 7 so that intake air is introduced into the combustion chamber 6 at a predetermined timing. A supercharger 10 as a mechanical supercharger driven by an output shaft of the engine 1 is provided upstream of the intake passage 7.
Are arranged. An intake manifold 1 having an intake passage 7 formed therein at an upstream opening of the intake port 8.
1 is connected to the downstream end of the intake manifold 1.
A fuel injection valve 12 for injecting fuel into the intake port 8 is provided at a downstream end connection portion of the fuel injection valve 1.

An exhaust passage 14 is connected to the combustion chamber 6, and an exhaust port 15 at the upstream end of the exhaust passage 14 is provided.
An exhaust valve 16 is provided at an opening to the combustion chamber 6 so that exhaust gas is discharged from the combustion chamber 6 at a predetermined timing. The opening / closing timing of the intake valve 9 and the exhaust valve 16 is, as shown in FIG.
Is set to open from 12.5 ° before top dead center, and the exhaust valve 16 is set to close at 25 ° after top dead center. That is, in this embodiment, during the overlap period in which the intake valve 9 and the exhaust valve 16 are both open, the exhaust valve 16 closes from 12.5 ° before the top dead center when the intake valve 9 opens. 25 after top dead center
It is set to be up to ゜.

Reference numeral 21 denotes a rotation speed sensor as rotation speed detection means for detecting the rotation speed of the engine, and 22 denotes a boost sensor for detecting the load on the engine. Is input to the control unit 20. The operation of the fuel injection valve 12 is controlled by the control unit 20.

Next, the operation control of the fuel injection valve 12 by the control unit 20 will be described. First,
In the control unit 20, the fuel injection valve 12 provided for each cylinder 2 is controlled so as to inject and supply fuel in synchronization with the intake / exhaust timing of the corresponding cylinder 2. Here, the case of one cylinder will be described, but the other cylinders are similarly controlled. That is, the control unit 20 determines whether or not the engine 1 is in a supercharging operation region in which the supercharger 10 supercharges the engine 1 under a high load state. This is determined by whether or not the boost value detected by the boost sensor 22 is equal to or greater than a predetermined value. When the rotation speed is equal to or lower than the predetermined rotation speed, that is, in the supercharging operation region and the low speed region, the control unit 20 calculates the fuel injection amount according to the load, and then the fuel injection valve 12 determines the injection timing. The signal is output so as to be during the overlap period. That is, the control unit 20
Is, for example, based on a preset map, the injection timing according to the operating state at that time (in this case, during the overlap period, a specific example is indicated by a dashed line in FIG. 2) And outputs a signal for executing injection to the fuel injection valve 12 when the crank angle corresponds to the injection timing. Further, when the engine speed detected by the speed sensor 21 exceeds a predetermined speed, that is, when the engine is in the supercharging operation region and in the high speed region, the same control as in the low speed region is performed. In this case, the injection timing is advanced from the low-speed range and the amount of advance is set to be larger as the rotation speed increases, and as a specific example, the load is the same as that in the low-speed range. In this case, the injection timing is indicated by the two-dot chain line in FIG.

On the other hand, when the boost value detected by the boost sensor 22 is equal to or less than a predetermined value and the engine 1 is not in the supercharged operation region where the engine 1 is in a low load state, the injection timing is advanced from the supercharged operation region to make the intake stroke. Set to be before. That is, in this case, the injection timing is set in the map in advance so as to be before the intake stroke in the entire engine rotation range, and the control unit 20 uses the map to determine the injection timing (this In this case, before the intake stroke, a specific example is indicated by a broken line in FIG. 2), and when the crank angle corresponds to the injection timing, the fuel is injected into the fuel injection valve 12. Output a signal. From the above, the control unit 20 determines whether or not the engine 1 is in the supercharging operation range based on the output of the boost sensor 22. When the fuel injection valve 12 is controlled to start injecting fuel during the valve overlap period in which the intake valve 9 and the exhaust valve 16 are both open, and when it is determined that the operation is in the non-supercharging operation region, And control means for controlling each of the fuel injection valves 12 so that the injection start timing is advanced from the injection start timing in the supercharging operation region.

Therefore, in the above embodiment, the injection timing of the fuel injection valve 12 in the supercharging operation region and in the low speed region is set during the overlap period. The fuel spray is
A large amount of pressurized intake air with a high flow velocity flows into the combustion chamber 6 as an air-fuel mixture while being mixed with air. Therefore, when the air-fuel mixture (fuel spray) flows into the combustion chamber 6, the air-fuel mixture flows out to the exhaust port 15 while pushing out the residual gas, since the air-fuel mixture is in the latter half or almost at the end of the overlap period. The air-fuel mixture is difficult to flow out of the exhaust port 15 and blow-by can be prevented. Further, since the air-fuel mixture comes into contact with the high-temperature residual gas when flowing into the combustion chamber 6, the fuel spray of the air-fuel mixture can promote vaporization and atomization, thereby improving the combustibility. Further, since the substantial period of the overlap period is shortened on the high rotation side in the supercharging operation region, the air-fuel mixture flowing into the combustion chamber 6 contacts the high temperature residual gas at the same injection timing as in the low speed region. To cope with the fact that the fuel spray is hardly evaporated and atomized, making it difficult to improve flammability.
In this case, in the high-speed range, the injection timing is advanced and the amount of advance is increased as the rotation speed increases, so that the air-fuel mixture flows into the combustion chamber 6 earlier than in the low-speed range, and The contact with the residual gas is performed, and the combustion property can be improved by promoting vaporization and atomization. Moreover, since the substantial period of the overlap period is short, blow-by can be effectively prevented. Therefore, in the supercharging operation region, it is possible to reliably prevent the fuel spray from being blown through from a low speed range to a high speed range, and to promote vaporization and atomization to improve the combustibility and improve the output.

On the other hand, the non-supercharging operation region is a low-load region where the intake air flow rate is small and it is difficult to sufficiently mix fuel spray with air in a short time.
Since the setting is made before the intake stroke advanced from the overlap period of the supercharging operation region, the fuel spray can be sufficiently mixed with the air in the intake port 8,
The flammability can be improved and the fuel efficiency can be improved.

[0016]

As described above, according to the fuel supply system for a supercharged engine according to the first aspect of the present invention, the supercharging operation is performed by setting the injection timing in the supercharging operation range to be during the overlap period. In the operating region, it is possible to prevent blow-through of the fuel spray, promote vaporization and atomization, improve the combustibility, and improve the output. On the other hand, in the non-supercharging operation region, the injection timing is advanced during the overlap period of the supercharging operation region, so that the fuel spray is sufficiently mixed with the air to improve the flammability and improve the fuel efficiency. Can be improved .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a supercharged engine including a fuel supply device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing opening and closing timings of intake and exhaust valves.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 6 Combustion chamber 8 Intake port 10 Supercharger (supercharger) 12 Fuel injection valve 20 Control unit (control means, judgment means) 21 Speed sensor (speed detection means) 22 Boost sensor

Claims (1)

(57) [Claims] A fuel injection valve for supplying fuel to an intake port of each cylinder is provided, and a supercharger is provided, and each fuel injection valve synchronizes with the intake / exhaust timing of a corresponding cylinder. In a fuel supply device for a supercharged engine that injects and supplies fuel, determining means for detecting an engine load and determining whether or not the engine is in a supercharging operation range based on the detected load; When it is determined that the operation is in the operation range, the fuel injection valves are controlled so as to start fuel injection during a valve overlap period in which both the intake valve and the exhaust valve are open, and in the non-supercharged operation region. Control means for controlling each of the fuel injection valves so as to advance the injection start timing from the injection start timing in the supercharging operation region when it is determined that there is a supercharger. Engine fuel Charging device.