JPH03260372A - Fuel injection device of engine with supercharger - Google Patents

Abstract

PURPOSE:To improve mixing performance of a mixture gas by providing a supercharger in an intake passage in the downstream side of a throttle valve, and arranging a fuel injection valve in a branch intake passage in each cylinder and an auxiliary fuel injection valve in the upstream side of the supercharger in the intake passage. CONSTITUTION:In the case of an intake system 2 of an engine 1, provided with a main intake passage 6 arranged with a throttle valve 3, a mechanical supercharger 4 and an intercooler 5 successively from the upstream side, surge tank 7 connected with the downstream end of the passage 6 and a plurality of branch passages 9 branched from the surge tank 7 and connected respectively to a combustion chamber 8 of each cylinder, a main fuel injection valve 14 is provided so as to be directed into the combustion chamber 8 in each branch passage 9. An auxiliary fuel injection valve 15 is provided in the just upstream part of the supercharger 4. A sufficiently mixed mixture gas can be supplied to each combustion chamber 8 by injecting fuel asynchronously from the auxiliary fuel injection valve 15 at the time of acceleration or the like while injecting fuel from each main fuel injection valve 14 synchronously with a suction stroke of each cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection device for an engine for an automobile or the like, particularly for a supercharged engine having a supercharger in an intake passage.

(Prior art) In automobile engines, a supercharger is sometimes installed in the intake passage in order to increase the amount of intake air supplied to the combustion chamber and improve engine output. An exhaust turbo supercharger that is driven by exhaust gas energy, a mechanical supercharger that is driven by engine output, etc. are used as a machine. There are two types of superchargers: compression type (combre/sosa type), which compresses intake air, and positive displacement type (blower type), which does not compress intake air by itself. A supercharger has the advantage that a high supercharging pressure can be obtained when the engine is fully loaded or at a high load, and intake air filling efficiency or engine output can be further improved compared to a positive displacement supercharger.

On the other hand, as described in, for example, Japanese Utility Model Application Publication No. 63-51121, fuel in this type of engine is supplied to branch passages that are branched for each cylinder downstream of the supercharger in the intake passage. This is usually done by arranging fuel injection valves and injecting fuel from these injection valves.2 In that case, the fuel injection is configured to be performed in synchronization with the intake stroke of each cylinder. .

(Problem to be Solved by the Invention) By the way, in the case of fs, where the fuel injection valve is arranged in the branch passage in the downstream part of the intake passage as described above, the distance from the injection valve to the combustion chamber is short, so that there is not enough fuel. The mixture is supplied to the combustion chamber in a state that has not been vaporized and atomized, resulting in poor mixing performance of the air-fuel mixture and failure to obtain a good combustion state.

In addition, when a compression-type mechanical supercharger is used as the above-mentioned supercharger, the engine output at high loads is further improved as described above, but at low loads that do not require high boost pressure. Since the intake air is sometimes compressed, the load increases by the amount of compression work, which causes a problem in that the driving loss becomes relatively large at low loads when the engine output is low, and fuel efficiency deteriorates.

The present invention addresses the above-mentioned problems in supercharged engines by improving the mixing properties of the air-fuel mixture, improving the combustion state, and improving the response during acceleration. In particular, when a compression-type mechanical supercharger is used, it is necessary to maintain high boost pressure or intake air charging efficiency during high loads, thereby reducing the driving loss of the supercharger during low loads. The goal is to improve fuel efficiency by increasing fuel efficiency.

<Means for Solving the Problems> In order to solve the above problems, a fuel injection device for a supercharged engine according to the present invention is characterized in that it is configured as follows.

First, the invention according to claim 1 of the present application (hereinafter referred to as the first invention) is a supercharger provided in an intake passage downstream of a throttle valve, and a branch passage branched for each cylinder in the downstream part of the intake passage. In a supercharged engine in which fuel injection valves for injecting fuel in synchronization with the intake stroke of each cylinder are arranged, the synchronous injection fuel injection valve and the fuel injection valve for synchronous injection are disposed upstream of the supercharger in the intake passage. is characterized by the arrangement of another auxiliary fuel injection valve.

Further, the invention according to claim 2 (hereinafter referred to as the second invention) is provided with a compression type mechanical supercharger that is constantly driven by the engine output in the intake passage downstream of the throttle valve,
In addition, similarly to the first invention, a supercharger in which fuel fI injection valves that inject fuel in synchronization with the intake stroke of each cylinder are arranged in branch passages that are branched for each cylinder in the downstream part of the intake passage. In the engine, a gap is provided between the housing and the rotor constituting the supercharger, and a gap is provided to allow part of the intake air to pass through, and the fuel injection valve for synchronous injection is provided on the upstream side of the supercharger in the intake passage. The present invention is characterized in that an auxiliary fuel injection valve separate from the auxiliary fuel injection valve is arranged, and a control means is provided for injecting fuel from the auxiliary fuel injection valve when the engine load is high.

(Function) According to the above configuration, first, in the case of the first invention, since the auxiliary fuel injection valve disposed on the upstream side of the supercharger is located relatively far from the combustion chamber, the injection valve is injected from the injection valve. The fuel is vaporized and atomized before it is supplied to the combustion chamber, and when it passes through the supercharger downstream of the injection valve, it is forcibly combined with the intake air by the rotation of the supercharger. It will be stirred. As a result, by allocating a certain proportion of the required fuel to this auxiliary fuel injection valve, a well-mixed and good air-fuel mixture is supplied to the combustion chamber as a whole, improving combustibility. 5 Also, since the air-fuel mixture created by the fuel injected from the auxiliary fuel injection valve is always stored in the intake passage,
When the amount of intake air increases as the throttle valve opens, this air-fuel mixture is immediately introduced into the combustion chamber, improving acceleration response.Furthermore, the fuel injected from the auxiliary fuel injection valve The supercharger will be cooled and overheating of the supercharger will be prevented.

Further, according to the second invention, when the engine is under low load, a portion of the intake air passes through the gap provided between the housing and the rotor of the supercharger, thereby compressing the intake air by the supercharger. The amount decreases, the driving loss of the supercharger is reduced accordingly, and the fuel efficiency is improved. On the other hand, under high load conditions when fuel is injected from the fuel injection valve upstream of the supercharger, this fuel adheres to the inner wall surface of the rotor in the supercharger and blocks the above-mentioned gap, causing the above-mentioned intake air leakage. This prevents the air from passing through, and therefore, the same compression efficiency as when using a normal compression supercharger with a small gap can be obtained, ensuring high intake air filling efficiency or engine output in accordance with demand.

(Example> Examples of the present invention will be described below.

First, FIG. 1 shows the configuration of the intake system of the engine according to the first embodiment.The intake system 2 of the engine 1 includes, from the upstream side, a throttle valve 3, a mechanical supercharger 11!4, and an intercooler 5. A main intake passage 6 in which a main intake passage 6 is arranged, a surge tank 7 to which the downstream end of the passage 6 is connected, and a surge tank 7 branched from the surge tank 7 and connected to combustion chambers 8...8 of each cylinder in the engine body, respectively. multiple branch passages 9
...9. Further, this intake system 2 is provided with a bypass passage 10 that branches from between the throttle valve 3 and the supercharger 1114 in the main intake passage 6 and joins to the downstream side of the supercharger 4, and the bypass passage 10 A bypass valve 11 is installed in the. The supercharger 4 is driven by the crankshaft 12 of the engine 1 via a belt 13.

In addition, each branch passage 9 in this intake system 2...
At 9, main fuel injection valves 14...14 are respectively installed so as to be directed into the combustion chambers 8...8, and
An auxiliary fuel injection valve 15 is installed immediately upstream of the supercharger 814. Then, according to a signal from the controller 16, the main fuel injection valves 14...14 are synchronously activated during the intake stroke of each cylinder, and the auxiliary fuel injection valve 15 is asynchronously injected with fuel regardless of the intake stroke of each cylinder. It is designed to spray.

Note that the controller 16 also controls the amount of fuel injected from the main fuel injection valves 14 .

Next, to explain the function of this embodiment, the air cleaner (
Intake air drawn into the main intake passage 6 according to the opening degree of the throttle valve 3 from (not shown) is pressurized by the supercharger 4, passes through the intercooler 5, and is cooled. is introduced into the surge tank 7, and further the surge tank 7
The combustion chamber 8 of each cylinder passes through each branch passage #r9...9.
...8 is supplied.

In that case, when the engine is under low load and does not require particularly high intake air filling efficiency, the bypass valve 11 on the bypass passage N10 opens and the intake air is mainly supplied to the bypass passage 10.
The load on the supercharger 4 is reduced by passing through the supercharger 4, and when the engine is under high load, which requires high intake air filling efficiency, the bypass valve 11 is closed and all intake air passes through the supercharger 4. A high boost pressure is obtained, and the intake air filling efficiency or engine output increases.

On the other hand, in synchronization with the intake stroke of each cylinder, each branch passage &'!
Main fuel injection valves 14 respectively arranged at 9...9...
・Fuel is injected from 14, and fuel is also asynchronously injected from the auxiliary fuel injection valve 15, which is separately arranged on the upstream side of the supercharger 4, and these fuels together with the intake air form a mixture. It is then supplied to the combustion chambers 8...8 of each cylinder. In that case, since the auxiliary fuel injection valve 15 is located at a distance from the combustion chambers 8...8, the fuel injected from the injection valve 5 is sufficient to reach the combustion chambers 8...8. The air is vaporized and atomized, and when it passes through the supercharger 814, it is forcibly mixed with the intake air by the rotation of the supercharger 4. Therefore, the main fuel injection valve 14.
...A sufficiently mixed air-fuel mixture as a whole including the air-fuel mixture caused by the fuel injected from the combustion chamber 8
... 8, and good combustibility can be obtained.

In addition, by injecting fuel from the auxiliary fuel injection valve 15 asynchronously with respect to the intake stroke, the portion of the main intake passage 6 downstream of the supercharger 4, especially the surge tank 7
Therefore, during acceleration when the intake air amount increases with the opening operation of the throttle valve 3, the air-fuel mixture is immediately supplied to the combustion chambers 8...8, resulting in a good condition. This results in excellent acceleration response.

Furthermore, when the fuel injected from the auxiliary fuel injection valve 15 passes through the supercharger 4, the supercharger 6
Heat is removed from the supercharger 14, thereby cooling the supercharger 4, thereby preventing overheating and related problems.

Next, a second embodiment shown in FIGS. 2 to 4 will be described.

In the following embodiments, the same components as in the first embodiment will be described using the same reference numerals.

The intake system 2 of the engine 1 according to the second embodiment has the same configuration as the first embodiment, and includes a main intake vent in which a throttle valve 3, a mechanical supercharger tj14A, and an intercooler 5 are arranged from the upstream side. B6, a surge tank 7, a plurality of branch passages 9...9 connected to the combustion chambers 8...8 of each cylinder, and a bypass passage 10 that bypasses the supercharging 94A. A bypass valve 11 is installed on the passage 10.

In addition, each branch passage 9...9 has a main fuel injection valve 14.
...14 are installed respectively, and the supercharger 4
An auxiliary fuel injection valve 15 is installed upstream of A, and fuel injection by these fuel injection valves 14...14.15 is controlled by a signal from a controller 16A.

In that case, the controller 16A controls the main fuel injection valve 1
4...14, as in the first embodiment, fuel is injected in synchronization with the intake stroke of each cylinder, while engine load correspondence I such as the opening degree of the throttle valve 3 is detected. A signal from the sensor 21 is input, and the auxiliary fuel injection valve 15 is configured to inject fuel only when the engine is under high load.

Further, in this embodiment, as the supercharging 114A, as shown in FIG. A so-called roots-type compression supercharger configured to discharge from the outlet 25 is used, and in particular, in this supercharger 4A, as shown enlarged in FIG. 4, the rotors 2B, 23 Both ends 23a of
The dimensions of each part are set so that a gap a larger than the gap normally provided for absorbing thermal expansion is created between the inner circumferential surface 22a of the housing 22 and the inner circumferential surface 22a of the housing 22.

According to this embodiment, when the opening degree of the throttle valve 3 is small and therefore the intake air amount is low during low load of the engine, the synchronous injection Main fuel injection valve 14...1
Fuel is injected only from the supercharger 4A, so only intake air passes through the supercharger 4A.

In that case, since a gap a larger than usual is provided between the housing inner circumferential surface 22a and the rotor tip 23a that constitute the supercharger 114A, the air is sucked into the supercharger 4A from the inlet 24. A portion of the intake air passes through the gap a without being compressed and is discharged from the outlet 25, and the compression work of the supercharger 4A is reduced by that amount. Therefore, the load or driving loss on the supercharger 4 is reduced when the engine is under low load, and fuel efficiency is improved.

On the other hand, during high load of the engine when the opening degree of the throttle valve 3 increases and the intake air amount increases accordingly, in addition to the above-mentioned main fuel injection valves 14...J4, supercharging 8!4A
Fuel is also injected from the auxiliary fuel injection valve 15 located immediately upstream of the fuel injection valve. And this fuel is used for supercharging $4 along with the intake air.
At the same time, the rotor 2 is sucked into the supercharging 114A.
3 and 23, the fuel adheres to the inner circumferential surface 22a of the housing 22 due to centrifugal force, and as a result, as shown by the fII line X in FIG.
The rWJ gap a between the rWJ a and the rotor tip 23a is closed, and the passage of intake air through the internuclear jla is prevented. As a result, the volumetric efficiency of the supercharger 4A is improved, and a high supercharging pressure similar to that of a normal compression supercharger where the gap is not particularly large can be obtained.As a result, when the engine is under high load, High intake air filling efficiency or engine output that meets demand is ensured.

Also in this embodiment, when fuel is injected from the auxiliary fuel injection valve 15 under high load, the mixture is sufficiently mixed in the combustion chambers 8...8, as in the first embodiment. Air is supplied, good acceleration response is obtained, and overheating of the supercharger 11!4A is prevented.

Furthermore, to explain the third embodiment shown in FIG.
The intake system 2 of the engine 1 according to this embodiment also includes, from the upstream side, a throttle valve 3, a mechanical supercharging I! 4 and an intercooler 5, a surge tank 7, a plurality of branch passages 9...9 connected to the combustion chambers 8...8 of each cylinder, and the supercharger 614. It is composed of a bypass passage 10 that bypasses, and a bypass valve 11 is installed on the bypass passage 1o. In addition, each branch passage 9...9 is provided with a main fuel injection valve 14...
14 are arranged, and an auxiliary fuel injection valve 15 is arranged immediately upstream of the supercharger 4.

In this embodiment, the main fuel injection valve 14
...14 and the controller 16B that drives the auxiliary fuel injection valve 15, the engine ignition switch 31
At the same time, the controller 16B receives the signals from the engine coolant and the water temperature sensor 32 that detects the temperature of the engine cooling water, and controls the main fuel injection valves 14... Similarly, while injecting fuel in synchronization with the intake stroke of each cylinder, the auxiliary fuel injection valve 15 is injected when the ignition switch 31 is on and the cooling water temperature is low, below a predetermined value. Fuel is injected when the engine is cold started.

Therefore, according to this embodiment, the ignitability of the air-fuel mixture is poor;
During a cold start of an engine with unstable combustion, each branch passage 9
Main fuel injection valves 14 installed at ...9 respectively.
In addition to the fuel injected from the supercharger 14, fuel is also injected from the auxiliary fuel injection valve 15 located immediately upstream of the supercharger, and the air-fuel mixture sufficiently mixed with the intake air is supplied to the combustion chambers 8...8. That will happen. This improves the ignitability or combustibility of the air-fuel mixture, and provides good starting performance during cold starting.

(Effects of the Invention) As described above, according to the present invention, in an engine equipped with a supercharger in the intake passage, the fuel injection valves for synchronous injection are installed in each branch passage in the downstream part of the intake passage. In addition, by arranging the auxiliary fuel injection valve on the upstream side of the supercharger, vaporization atomization is promoted and an air-fuel mixture that is sufficiently mixed with intake air is supplied to the combustion chamber. In addition to obtaining good combustibility, the mixture of fuel injected from the auxiliary fuel injection valve is constantly stored in the intake system, improving acceleration response. The supercharger is cooled by the fuel injected from the injection valve, and overheating of the supercharger is prevented.

In particular, according to the second invention, a compression type mechanical supercharger is used as the supercharger, and a gap is provided between the housing and the rotor of the supercharger to allow part of the intake air to pass through, In addition, by injecting fuel from the auxiliary fuel injection valve only when the engine is under high load, the load or driving loss on the supercharger is reduced when the engine is under low load, and the required amount is reduced when the engine is under high load. Intake air filling efficiency is ensured, and the fuel efficiency and output performance of the engine are improved at the same time.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIGS. 1, 2, and 5 are diagrams showing the configurations of the first, second, and third embodiments, respectively, and FIG. 3 is a diagram showing the configuration of the second embodiment. FIG. 4 is a schematic sectional view of the supercharger, and FIG. 4 is an enlarged sectional view of essential parts of the supercharger. 4.4A...supercharger, 6...intake passage (main intake passage), 9...branch passage, 14...main fuel injection valve, 15
... Auxiliary fuel injection valve, 16.16A, 16B ... Control means (controller), 22 ... Housing, 23
...Rotor, a...gap.

Claims (2)

[Claims] (1) Fuel injection in which a supercharger is provided in an intake passage downstream of a throttle valve, and fuel is injected into a branch passage for each cylinder downstream of the intake passage in synchronization with the intake stroke of each cylinder. A fuel injection device for a supercharged engine in which valves are respectively arranged, and an auxiliary fuel injection valve different from the synchronous injection fuel injection valve is arranged upstream of the supercharger in the intake passage. A fuel injection device for a supercharged engine, characterized by: (2) A compression-type mechanical supercharger that is constantly driven by the engine output is provided in the intake passage downstream of the throttle valve, and a branch passage for each cylinder in the downstream part of the intake passage is provided with a A fuel injection device for a supercharged engine, in which fuel injection valves for injecting fuel in synchronization with the intake stroke of the supercharger are arranged, and a part of the fuel injection valve is arranged between the housing and the rotor that constitute the supercharger. A gap is provided to allow intake air to pass through, and an auxiliary fuel injection valve other than the synchronous injection fuel injection valve is disposed upstream of the supercharger in the intake passage, and the auxiliary fuel injection valve is disposed upstream of the supercharger in the intake passage. A fuel injection device for a supercharged engine, comprising a control means for injecting fuel from an auxiliary fuel injection valve.